20 Molecular Medical Devices for Nanoneurosurgery

303

B. Kateb et al. (eds.),

The Textbook of Nanoneuroscience and Nanoneurosurgery

https://doi.org/10.1007/978-3-030-80662-0_20

Molecular Medical Devices

for Nanoneurosurgery

Drora Samra Shevy, Rutledge Ellis-Behnke,

and Babak Kateb

Abstract

Nanoneurosurgery represents a groundbreaking paradigm

in the central nervous system (CNS) therapeutic arena,

providing unprecedented precision and potential for direct

intervention. This review delves into the transformative

potential of molecular nanoneurosurgery, with a particu

lar focus on its application in treating conditions such as

renovascular hypertension (RVHT) and intracerebral

hemorrhage (ICH) in a rat model. Utilizing the self-

assembling peptide (RADA)4, we demonstrate the thera

peutic efficacy of this nanomaterial in mitigating

hematoma expansion, reducing cell apoptosis and inhibit

ing inflammatory responses post-ICH. The surgical meth

odology employed encompasses a comprehensive

sequence from the induction of RVHT, selection criteria

based on systolic blood pressure, ICH induction, blood

clot aspiration, and precise administration of (RADA)4,

to the subsequent evaluations of hematoma volume, cell

death, and inflammatory markers.

The results highlight a significant reduction in hema

toma volume, TUNEL-positive cells, and iNOS-

immunoreactive cells in the (RADA)4-treated group,

showcasing the material’s protective and therapeutic

potential. While this study sheds light on the promising

applications of nanoneurosurgery, it also underscores the

need for further research and development in this domain

to enhance the precision, efficacy, and safety of such

nanomaterials in clinical settings.

Moreover, nanoneurosurgery emerges as a pioneering

approach in the realm of nerve repair, presenting innovative

solutions with enhanced precision and potential for func

tional restoration. This review meticulously examines the

advancements and applications of nanoneurosurgery, with

a distinct emphasis on optic nerve repair, a challenging yet

crucial domain within neurosurgery. We explore the utiliza

tion of self-assembling peptides such as (RADA)4, eluci

dating its role in promoting nerve regeneration and

functional recovery in models of optic nerve injury.

Through a comprehensive analysis of surgical method

ologies, this study highlights the intricate procedures

involved in the administration of nanomaterials, empha

sizing their therapeutic efficacy in mitigating damage,

reducing inflammation, and enhancing neuronal regenera

tion. The outcomes underscore a significant improvement

in nerve function and structural integrity, marking a

promising step toward the development of effective treat

ments for optic nerve injuries. Additionally, the review

discusses the broader implications of nanoneurosurgery

in the central nervous system (CNS), showcasing its

potential to address a spectrum of neurological disorders.

The results emphasize the need for ongoing research,

standardized protocols, and safety evaluations to fully

harness the potential of nanoneurosurgery, ensuring its

successful translation from experimental models to clini

cal practice.

D. S. Shevy

California Institute of Technology (Caltech), Pasadena, CA, USA

e-mail:

drora@caltech.edu

R. Ellis-Behnke (

)

Department of Brain & Cognitive Sciences, Massachusetts

Institute of Technology, Cambridge, MA, USA

Arch Therapeutics Inc., Columbia, SC, USA

e-mail:

rutledg@mit.edu

B. Kateb (

)

Society for Brain Mapping and Therapeutics,

Pacific Palisades, CA, USA

National Centre for Nano-Bio-Electronics (NCNBE),

Pacific Palisades, CA, USA

Brain Technology and Innovation Park (BTIP),

Pacific Palisades, CA, USA

World Brain Mapping Foundation (WBMF),

Pacific Palisades, CA, USA

e-mail:

Babak.Kateb@worldbrainmapping.org

304

Keywords

Medical devices · Nanoneurosurgery · Molecular

medical device

Introduction

The neural organization has implications in the realm of

nanoneurosurgery. At the molecular level, cells communi

cate, differentiate, proliferate, and repair using a multitude of

signaling pathways and molecular machines (Alberts et al.,

2014

). These processes are highly refined, evolved over mil

lennia, and have a precision that is unparalleled by our cur

rent surgical tools.

The Potential of Molecular Medicine

Molecular medicine revolves around understanding and har

nessing these cellular processes for therapeutic purposes

(Alberts et al.,

2014

). Within the framework of neurosurgery,

the potential of molecular medicine opens up a novel dimen

sion where intervention is not just physical but bio-chemical

(Feynman,

2018

Understanding Molecular Machines

The term “molecular machines” or nanomachines refers to

complexes of proteins and other molecules that perform spe

cific tasks within cells. For instance, the kinesin protein

“walks” along cellular highways made of microtubules, car

rying with it essential materials. Another example is the ATP

synthase, a molecular motor that produces energy currency

(ATP) for the cell (Alberts et al.,

2014

Harnessing Molecular Mechanisms

for Nanoneurosurgery

With advancements in nanotechnology, researchers are now

able to design nanoparticles that can mimic, enhance, or dis

rupt these natural molecular machines (Silva,

2008

). For

example, nanoparticles can be engineered to release specific

molecules that can aid in the repair of damaged neurons, or

to specifically target tumor cells and deliver a lethal dose of

drugs, avoiding harm to surrounding healthy tissue (Peer

et al.,

2007

Innovations in Molecular Imaging

Beyond interventions, molecular imaging using nanoparti

cles can allow surgeons to visualize the finest structures of

the brain and its pathologies in real time, offering superior

guidance during surgical procedures. Quantum dots, gold

nanoparticles, and other imaging agents can be used to high

light different cellular structures, improving the resolution

and precision of imaging modalities like MRI and CT scans

(West & Halas,

2003

Challenges and Ethical Considerations

However, the path to realizing the full potential of nanoneu

rosurgery is filled with challenges. The brain’s protective

barrier, the blood–brain barrier, poses a significant hurdle to

introducing nanoparticles into the CNS (Silva,

2008

Researchers are exploring various techniques, from design

ing nanoparticles that can “trick” their way past this barrier

to using focused ultrasound to make the barrier temporarily

permeable (Whitesides & Grzybowski,

2002

). Furthermore,

the very concept of introducing molecular machines and

nanoparticles into the human body raises ethical concerns

(Camazine et al.,

2001

The Phrases “Self-assembly”

and “Self-organization”

•

Self-assembly refers to the process by which individual

components spontaneously come together to form a

larger, organized structure. This is driven by specific

interactions, such as hydrogen bonding, van der Waals

forces, or other intermolecular forces. An example is the

way lipid molecules arrange themselves into bilayer

structures in water due to their hydrophobic and hydro

philic regions (Oberdörster et al.,

2005

). Another classic

example is the double helix formation of DNA.

•

Self-organization is a broader concept and involves the

spontaneous arrangement of systems or structures into

patterns or structures without external interference. In

biological systems, this can be seen in the formation of

cellular structures, tissue organization, or even the

arrangement of cells during development (Health,

2023

Origins of Neurosurgery and Cellular

Assembly in Neural Development

The annals of history offer intriguing insights into the prac

tice of neurosurgery, with primitive tools crafted ingeniously

from available materials like obsidian and sharp-edged

stones (Tullo,

2010

). Artifacts dating some 13,000 years

back shed light on the ancient Incas’ practice of trephination

(Moghaddam et al.,

2015

). This surgical procedure entailed

making an opening in the skull, ostensibly to release malig

nant spirits, which in hindsight could have been manifesta

D. S. Shevy et al.

305

tions of ailments like epilepsy or severe migraines

(Neuroskeptic,

2012

Tissue Organization and Neurulation

The developmental journey from a fertilized egg to a multi

cellular organism is a marvel of biology (Muñoz-Sanjuán &

Brivanlou,

2002

). The blastocyst, an early embryonic phase,

undergoes neurulation (Fig.

20.1

) (Purves & Lichtman,

1985

), forming the neural tube from its ectodermal layer

(Schoenwolf & Smith,

1990

). This blastocyst differentiates

into three distinct cellular realms:

•

The endoderm, giving rise to the inner linings of the

digestive and respiratory tracts (Zorn & Wells,

2009

)

•

The mesoderm, spawning the body’s organs, muscles, and

circulatory system (Buckingham et al.,

2005

)

•

The ectoderm, the precursor of the skin and the central

nervous system (Schoenwolf & Smith,

1990

)

Cellular Movement and ECM Interactions

Understanding cellular motion, particularly during neurula

tion, requires delving into the complex interactions between

cells and the extracellular matrix (ECM) (Hay,

2005

). Cells

Fig. 20.1

Neurulation. (

)

Embryo showing the

ectoderm (yellow) and the

start of the neural plate

precursor (green). Also shown

are the mesoderm and the

endoderm (

). (

) How

cells move during the

formation of the neural tube.

Note that the red cell moves

fastest and is first to reach the

midline (arrow indicates the

direction of midline), where

the neural tube starts to zip

up. The rest of the cells

follow at a slower rate. The

center of the spinal cord joins

first and then proceeds in both

directions toward the head

and the tail. (

) Neural tube

zipping up in relation to cell

migration (Purves &

Lichtman,

1985

)

Molecular Medical Devices for Nanoneurosurgery

306

experience variances in the densities of the ECM on their sur

faces, influencing their locomotion (Huttenlocher & Horwitz,

2011

). Furthermore, molecular complementarity—akin to the

lock-and-key model in molecular biology—plays a pivotal

role (Berg,

2002

). It denotes the propinquity between two

molecular structures, ensuring their apt alignment and bind

ing. DNA replication is a testament to this principle, where

complementarity between nucleotide bases drives accurate

DNA copying (Bruce Alberts et al.,

2002

). In the cellular

milieu, variations in the ECM’s composition can significantly

affect cell movement dynamics, whether enhancing cellular

adhesion or promoting swift movement (Copp et al.,

2003

The formation of the neural tube exemplifies the vast potential

and intricate roles that nanoscale interactions play (Ridley

et al.,

2003

). Such interactions, both mechanical and electro

static, wield considerable power (Liotta & Kohn,

2001

). They

can either aid a tumor to settle, gradually modifying its sur

roundings to foster its growth or inhibit its spread, enabling the

body’s defense mechanisms to eradicate it before it can estab

lish a stronghold (Tsonis,

2000

Reimagining Cellular Regeneration

Though it might not resemble traditional surgery, the body’s

innate capability to dynamically restructure and rejuvenate

its systems is paramount (Mammoto & Ingber,

2010

). The

same principles can be employed to engineer an environment

conducive to healing and regeneration (Salomoni & Calegari,

2010

). A standout example in this realm is the groundbreak

ing work by Salomoni and Calegari in 2010 (Calegari &

Huttner,

2003

). By modulating the duration of the G1 phase

in the cell cycle, they managed to rejuvenate cells, imbuing

them with a pseudo-youthful vigor that spurred growth (Poss

et al.,

2002

). While this method necessitates further investi

gations, its implications are profound. Imagine harnessing

this ability to promote regeneration in damaged organs,

limbs, or even brain tissue (Jessberger & Gage,

2014

). Such

techniques could potentially bridge gaps left by injuries or

neurodegenerative conditions (Park,

2013

The confluence of molecular biology, nanotechnology, and

classical surgery has paved the way for innovative medical

approaches (Alghamdi et al.,

2022

). These approaches, inspired

by natural processes, may redefine therapeutic interventions,

steering us closer to the elusive goal of holistic healing.

Central Nervous System

and Nanoneurosurgery

The vast intricacy of the central nervous system (CNS) has

been a subject of fascination and study for centuries (Newman

& Reichenbach,

1996

). When we think of the CNS, the first

image that often comes to mind is the brain, with its convo

luted folds and ridges. But how do we perceive such com

plexity? The answer lies in the eye—also a part of the CNS

(Safran,

2009

). Depending on the perspective—neurosur

gery or ophthalmology—the eye can be considered an exten

sion of the brain or vice versa (Schmidt & Leach,

2003

). This

dual perspective hints at the profound impact nanotechnol

ogy procedures can have on both the eye and the brain.

Purpose and Impact of Nanoneurosurgery

In the realm of nanotechnology, the primary goal of nanoneu

rosurgery is to reestablish and rejuvenate the disrupted path

ways within the CNS (Yuste,

2015

). This is not merely about

reconnecting the paths, but ensuring they are operational,

resembling their naive, original state. The focus is not just on

the physical restoration but also the functional revival

(Alivisatos et al.,

2013

). The visual system, being more

accessible, has been a prime candidate for such experiments.

The results have not only been histological but also opera

tional (Rolls & Treves,

2011

One of the major complications in spinal cord injuries is

the phenomenon of Diaschisis—a sudden alteration in a

healthy portion of the CNS due to damage in a distant area

(Lane et al.,

2014

). This makes it challenging to differentiate

between genuine regeneration and mere functional recovery,

particularly in instances where treatments like stem cell

injections report rapid recoveries (Huang et al.,

2017

). To

further elucidate, it is pivotal to distinguish between different

neuronal populations:

Neurons that are connected and functional

Neurons that are disconnected but remain functional

Neurons that are connected but non-functional due to

their link to a non-functional region

The exact nature of neuronal injuries can be diverse

(Yenari & Han,

2012

). They might not always involve a com

plete disconnect but can sometimes be partial disconnections

compounded by secondary damage from inflammation or

ischemia. Methods like hypothermia, despite the associated

debates, have shown benefits in preserving neurons (Silva,

2006

Recent Developments

Over the past 10 years, advancements in the field of nanoneu

rosurgery have been profound:

Improved

Nanomaterials

: The development and use of

biocompatible nanomaterials have enabled more effective

surgeries, ensuring minimal adverse reactions within the

CNS (Nair et al.,

2013

D. S. Shevy et al.

307

Advanced Imaging Techniques

: Modern imaging modali

ties, aided by nanotechnology, allow surgeons to visual

ize the CNS structures with unprecedented clarity, aiding

in more precise interventions (Zhang & Khademhosseini,

2017

Personalized

Treatment Plans

: With the help of nanotech

nology, treatments can be tailored based on the individu

al’s unique neurological structure and requirements

(Mavroidis et al.,

2004

Robot-assisted Procedures

: The incorporation of nano

technology with robotic surgery has paved the way for

surgeries that are more accurate, less invasive, and with

reduced recovery times (Kim et al.,

2010

Nano Drug Delivery

: Targeted drug delivery systems,

using nanotechnology, ensure that medications reach the

precise location in the CNS, enhancing the treatment’s

efficiency (Marblestone et al.,

2013

Neural Interface Devices

: Nanoscale devices have been

developed to bridge gaps in neural pathways, ensuring

that signals can be transmitted even if a part of the path

way is damaged (Martino & Pluchino,

2006

Stem Cell Integration

: The blend of nanotechnology with

stem cell research has given rise to techniques that pro

mote the integration of stem cells within the CNS, aiding

regeneration (Ellis-Behnke et al.,

2006b

In conclusion, while the realm of nanoneurosurgery is

still in its nascent stages, the developments over the past

decade have been monumental. As technology and research

progress, the potential for complete restoration and functional

recovery in CNS injuries becomes increasingly tangible.

Four Ps of CNS Regeneration: A Framework

for CNS Regeneration

To encapsulate the regeneration process in the CNS, the

framework of the “Four Ps of CNS Regeneration” was devel

oped, breaking down the process into four stages: preserve,

permit, promote, and plasticity (Figs.

20.2

and

20.3

) (Ellis-

Behnke,

2007

). Each of these stages focuses on a particular

challenge and the methods to address it.

The concept of “Four Ps of CNS Regeneration” (preserve,

permit, promote, and plasticity) devised by Ellis-Behnke in

2007 offers an integrative approach to understand the under

lying mechanisms and strategies for central nervous system

(CNS) regeneration (Ellis-Behnke,

2007

). Let us delve into

the new developments in the field that have taken place over

the last 10 years

Preserve

Advancements in imaging and diagnostics now allow for

early detection of neuronal injury. With timely interventions,

the immediate preservation phase has become more efficient.

There is also a better understanding of anti-apoptotic path

ways, which have led to drug developments to inhibit cell

death post-injury. In the longer duration preservation, neuro

trophic factors, small molecules, and gene therapies are

being explored to support the prolonged survival of neurons.

Advancements in biocompatible scaffolds are also ensuring

a conducive environment for cell survival during

regeneration.

Permit

With advancements in nanotechnology, bioengineered mate

rials are being designed to mimic the extracellular matrix of

the CNS, facilitating better cell migration and offering a con

ducive environment for regeneration. Molecular studies over

the past decade have provided insights into the inhibitory

molecules present in the CNS post-injury. Strategies like

enzyme treatments to break down inhibitory molecules, as

well as blocking their receptors, have emerged. Advanced

techniques in CRISPR and optogenetics are also being

explored to modify neuronal environments (Ellis-Behnke,

2007

Promote

The advent of personalized medicine allows for customized

treatments, which enhance regeneration through drug deliv

ery systems utilizing nanoparticles and liposomes to ensure

sustained release of growth-promoting molecules. Stem cell

therapies, including induced pluripotent stem cells (iPSCs),

have shown promise in promoting regeneration. Moreover,

combining traditional approaches with electrical stimulation

or bioelectronic methods is under exploration. This approach

aims at expediting the regeneration process and ensuring that

the growth is directed toward the target tissue.

Plasticity

Recent research has emphasized the role of post-injury reha

bilitation in rewiring the CNS. Advanced technologies like

virtual reality (VR) and augmented reality (AR) are employed

Molecular Medical Devices for Nanoneurosurgery

308

Fig. 20.2

Four Ps of CNS regeneration. Each of the four Ps is repre

sented by a horizontal bar depicting the time of treatment, as well as the

duration needed for the treatment to remain active. P1:

preserve

cells.

This is broken down into two parts: antiapoptotic and antinecrosis treat

ment, and growth factor support during elongation. P2: create a

permis

sive

environment. This is also broken down into two parts: creating a

permissive environment around the site of injury and making the target

tissue permissive to reinnervating axons. P3:

promote

the growth of

axons in an elongation mode. P4:

plasticity

. This has two parts: reduc

ing immediate post-injury plasticity so that filling-in is kept to a mini

mum and dysregulating plasticity during the time that axons are

reconnecting in the target tissue. This can be accomplished with factors

or training. The timeline runs from left to right and starts at the time of

injury: (a) time of injury, (b) 24 h after injury, (c) 72–96 h after injury,

(d) 2 weeks to 4 months or longer, and (e) years (Ellis-Behnke,

2007

)

Fig. 20.3

Mapping experiments to the four Ps of CNS regeneration.

There can be interplay with each of the four Ps, or one therapy could

impact all the Ps at once. Pay close attention to the correct time to pull

each of the levers (Ellis-Behnke,

2007

)

for rehabilitation to stimulate accurate CNS regeneration.

Non-invasive brain stimulation techniques, like transcranial

direct current stimulation (tDCS) and transcranial magnetic

stimulation (TMS), are being researched to enhance

plasticity

and functional recovery. Furthermore, understanding the

molecular underpinnings of Hebbian plasticity has led to the

development of drugs that can modulate synaptic strength.

This, combined with rehabilitation, can help in achieving

functional recovery more efficiently (Ellis-Behnke,

2007

Conclusions

The last decade has seen a surge in multidisciplinary

approaches combining biology, technology, and medicine

for CNS regeneration. As our understanding deepens and

technology advances, the dream of achieving complete

recovery post-CNS injuries is coming closer to reality.

Nanotechnology in Medicine: A Decade

of Progress

Nanotechnology, first coined by Norio Taniguchi in 1974

(Taniguchi,

1974

), has witnessed staggering growth and

potential in various fields, especially medicine. Over the past

10 years, the advancements in this domain have been nothing

short of revolutionary (Chauhan et al.,

2011

Nanomedicine Evolution

Old Landscape:

Traditionally, nanomedicine was heavily

reliant on liposomes, with Doxil being the flagship FDA-

approved nanomedicine in 1995 (Wicki et al.,

2015

). The

D. S. Shevy et al.

309

subsequent developments saw the rise of nanocrystals, pro

tein–drug conjugates, and metal nanoparticles, with each

innovation aiming to increase the delivery efficiency of drugs

and reduce potential side effects (Bobo et al.,

2016

New Developments

Targeted Drug Delivery: Advancements in nanocarrier

systems have allowed for precise drug delivery (Bobo

et al.,

2016

). Gold nanoparticles, magnetic nanoparticles,

and dendrimers have been researched extensively for tar

geted cancer therapy, allowing drugs to be directed spe

cifically to cancer cells, reducing systemic toxicity (Wicki

et al.,

2015

Diagnostic Advancements

Quantum dots, possessing unique light-emitting properties,

are now being used for in vivo imaging (Blanco et al.,

2015

Their stability and ability to get tagged to specific molecules

make them invaluable in early disease detection (Gao et al.,

2016

Biomaterials for Tissue Engineering: The development of

nanofibrous scaffolds has been a significant breakthrough in

tissue engineering (Auletta et al.,

2017

). These scaffolds pro

vide a suitable environment for cell growth and differentia

tion, with potential applications in regenerating damaged

tissues and organs (Yin et al.,

2016

Gene Editing and Therapies: As CRISPR technology

gains momentum and garners more attention, nanoparticles

have become a potential vector for delivering gene-editing

tools directly into target cells, making treatments for genetic

disorders more accessible (Langer,

2013

Nanoscaffolds: Building and Rebuilding

at the Nanoscale

Old Understanding:

Nanoscaffolds, typically comprising a

series of amino acids, have traditionally been used to create

conducive environments for cellular reconnection (Auletta

et al.,

2017

). These structures, after serving their purpose,

would disassemble and get excreted (Yin et al.,

2016

Recent Breakthroughs

Biodegradable Nanoscaffolds: The past decade has seen

the design of more sophisticated biodegradable nanoscaf

folds, which can degrade into harmless components over

time. These provide support for cell growth and then

gradually disappear, negating the need for surgical

removal (Yin et al.,

2016

Smart Nanoscaffolds: These scaffolds respond to envi

ronmental cues, like pH or temperature changes, and can

release embedded drugs upon such stimuli, making treat

ments more efficient (Conde et al.,

2013

)

Nanomedicine: Current Paradigm and Promise

While traditional nanomedicine relied heavily on aggregated

molecules, the contemporary approach is significantly more

sophisticated (Lammers et al.,

2016

). True nanomedicine, or

biologic medicine, focuses on the precision delivery of sin

gular molecules to specific sites. The goal is to maximize

therapeutic effects while minimizing side effects (Bobo

et al.,

2016

Latest Insights

Personalized Nanomedicine: Leveraging the power of

genomics, customized nanoparticles can be designed

based on an individual’s genetic makeup, ensuring higher

therapeutic efficacy (Yin et al.,

2016

Safety Protocols: With the proliferation of nanomedi

cines (Lammers et al.,

2016

), there is an increased focus

on understanding their long-term impacts on human

health. This has led to the development of safer nanopar

ticles and rigorous testing protocols to ensure minimal

toxicity (Andreas Wicki et al.,

2015

In conclusion, the last decade has seen nanotechnology

and medicine converge in unprecedented ways, leading to

more effective, targeted, and safer therapeutic interventions.

The pace of innovation promises even greater breakthroughs

in the coming years, making nanomedicine one of the most

exciting frontiers in healthcare (Chauhan et al.,

2011

A Deeper Dive into Nanomedicine

Distinction, Development, and Promise

Nanomedicine, deeply rooted in nanotechnology, ushers in

innovative modalities for existing and emerging treatments.

It can either refine an existing treatment or inaugurate new

classes of therapies and devices based on nanoscale dimen

sion (Chauhan et al.,

2011

Contrary to small molecules, which are essentially con

glomerates of 100,000 or more molecules delivered in clus

ters, nanomedicine offers more precision. Many of these

molecules often fail to reach their target due to issues related

to solubility, distribution, and metabolic pathways (Lammers

et al.,

2016

). The allure of nanomedicine, or biologic medi

cine, lies in its ability to present one or multiple molecules to

Molecular Medical Devices for Nanoneurosurgery

310

a designated site. Afterward, they are meticulously destroyed

or excreted, mitigating side effects (Bobo et al.,

2016

Developments Over the Decade

Personalized Nanomedicine

The integration of genomics with nanotechnology has

paved the way for tailoring nanoparticles to an individu

al’s genetic framework, enhancing therapeutic precision

(Yin et al.,

2016

Safety Protocols: The rise of nanomedicines has also

spotlighted their long-term effects on human health

(Lammers et al.,

2016

), driving the creation of safer

nanoparticles and stringent testing protocols (Wicki et al.,

2015

Enhanced Drug Delivery

The newer approaches in nanomedicine have been designed

to overcome traditional barriers of drug delivery. Through

novel techniques, drugs can be guided to target tissues,

increasing efficacy and reducing unwanted systemic expo

sure (Bobo et al.,

2016

In sum, the fusion of nanotechnology and medicine over

the last decade signifies a monumental shift toward advanced,

targeted, and safer therapeutic strategies. The rapid pace of

innovations hints at even brighter prospects for nanomedi

cine in the years to come (Chauhan et al.,

2011

Figure

20.4

demonstrates a schematic overview of the

major types of nanomedicine.

Nanomaterials

Advancements in Nanomaterials and Self-

assembly in Medicine

Understanding Nanomaterials

Biomedical applications have seen an expansive range of

materials. Materials vary in hardness and resilience. Some,

like those used in hip replacements, are sturdy and meant for

permanence (Merola & Affatato,

2019

). In contrast, others,

softer in nature, degrade and eventually leave the body

(Bonferoni et al.,

2021

). A notable intermediate is the cate

gory utilized for drug delivery, such as poly(lactide-co-

glycolide) (PLGA), a biocompatible and non-toxic polymer

fashioned from lactic and glycolic acid, serves as a conduit

for drug delivery, thanks to its non-toxic nature (Shi et al.,

2010

). Another is poly(methyl methacrylate) (PMMA), a

clear thermoplastic, finding applications in orthopedics

(Ratner,

2012

). However, the decomposition of these sub

stances can produce acidic by-products, possibly triggering

immune reactions (Alkie et al.,

2017

). Some are so stable,

bound covalently, requiring chemical degradation (Visan

et al.,

2021

Liposomes and micelles have gained attention for drug

delivery (Liu et al.,

2022

). Comprising lipid bilayers, lipo

somes can encase aqueous contents, while micelles have

either a fatty acid core with a polar surface or the reverse

(Aguilar,

2013

). These carriers can be engineered for target

specificity, especially for tumors (Zhang et al.,

2020

). Most

of the research involving these carriers has gravitated toward

cancer therapies. With the surge in cancer research, these

carriers are becoming paramount in the quest for effective

treatments (Liu et al.,

2022

The Beauty and the Evolving Dynamics

of Self-assembly

At the crossroads of science and medicine, the phenomenon

of self-assembly emerges as a beacon of hope. In the world

of nanoscale, scaffolds, once rigid and static, now exhibit the

flexibility to reconfigure based on environmental stimuli.

Drawing inspiration from nature, our body’s intricate bar

riers such as the skin, mucous membranes, and notably, the

blood–brain barrier serve as inspiration for these synthetic

counterparts (Chen & Liu,

2016

). With tight cellular junc

tions, these natural barriers have become the gold standard in

pathogenic defense mechanisms (Paradis et al.,

2021

Emerging research has thrown the spotlight on materials

possessing an innate ability to self-assemble (Ariga et al.,

2019

; Latypov & Coskun,

2015

This dynamic behavior, primarily orchestrated by

hydrophobic and hydrophilic interactions, is reminiscent

of the forces that drive protein folding (Newberry &

Raines,

2019

). Whether through direct interactions within

the protein matrix or indirect ones involving solvents, the

choreography of these forces is meticulous. The power

balance between hydrophilic and hydrophobic groups is

vital, with the former typically exerting stronger forces,

contingent upon their orientation (Durell & Ben-Naim,

2017

). These interactions beget structures, ranging from

minuscule amino acid sequences to grander designs like

fibrous sheets.

Additionally, advancements in understanding the van

der Waals forces and hydrogen bonds have paved the way

for intricate molecular designs (Hermann et al.,

2017

Distinct from each other, while hydrogen bonds engage

different electronegative entities, van der Waals forces

arise from fleeting dipoles (Hermann et al.,

2017

). A sig

nificant leap in the realm of ionic self-assembling peptides

has been the discovery and utilization of the (RADA)4

sequence (Koutsopoulos & Zhang,

2012

). This peptide’s

amphiphilic character, an interplay of hydrophobic and

hydrophilic residues, has been harnessed to create self-

assembled

-sheets.

D. S. Shevy et al.

311

Fig. 20.4

A schematic

overview of the major types

of nanomedicine(Mühlebach,

2018

)

These sophisticated 3D structures, with their hydrogel

avatar, mimic the extracellular matrix (ECM) and promise

strides in drug delivery and rapid hemostasis (Nicolas et al.,

2020

). With advancements, variants such as (RADA)4K5

have been structured into nanofibers, further broadening

their application spectrum (Elgersma et al.,

2019

In a parallel development, the DNA realm has seen break

throughs in understanding supercoiling, especially in the

context of DNA condensation (Dorman & Dorman,

2016

Harking back to the pioneering work of Johannes Freidrich

Miescher in 1869, contemporary studies emphasize the role

of salt concentrations in influencing DNA structure (Singh &

Singh,

2015

Molecular Medical Devices for Nanoneurosurgery

312

This dynamic interplay of chemistry, through modulation

of concentration and salt type, is slowly emerging as a tool

for structure fine-tuning at the nanolevel (Fadeel,

2019

In Retrospect and Forward Thinking

Nanomaterials, with their promise and potential, are script

ing a new chapter in biomedical applications (Goldman &

Coussens,

2005

). As research delves deeper into the intrica

cies of self-assembly and molecular interactions, the horizon

seems ripe with possibilities (Malik et al.,

2023b

). With this

second edition, we aim to bridge the knowledge of the past

with the innovations of the present, paving the way for a

future where medicine and nanotechnology walk hand in

hand (Morigi et al.,

2012

Advancements in Self-assembling Peptides

and Multidimensional Biomaterials

Journey with (RADA)4 and Beyond

The self-assembling peptide (SAP) known as (RADA)4 is a

hallmark in the world of synthetic biological materials (Gray

et al.,

2022

). Comprising ionic self-complementary peptides,

it is fashioned through a meticulous balance of alternating

positive and negative l-amino acids (Lee et al.,

2019

). What

is truly captivating is how they transform in the presence of

physiological-concentration salts (Ince-Coskun & Ozdestan-

Ocak,

2020

). These assemblies give birth to highly hydrated

scaffolds, with structures reminiscent of

-sheet ionic pep

tides (Mocanu et al.,

2022

). The nanofibers woven by

(RADA)4, each measuring approximately 10 nm in diameter

(Fig.

20.5

) (Ellis-Behnke et al.,

2006a

), are evocative of

nature’s own creation—the extracellular matrix (ECM)

(Salerno & Netti,

2023

Newer advancements have amplified our understanding

of this peptide’s utility. These nanofibers are more than just

structures; they represent a future where regeneration and

repair can be achieved seamlessly (Ogueri & Laurencin,

2020

). Their high compatibility with physiological environ

ments coupled with their impressive immunological neutral

ity makes them a boon for in vitro and in vivo applications

(Binaymotlagh et al.,

2022

Unveiling the EAKA Sequence

An innovative addition to the realm of self-assembling pep

tides is the EAKA sequence. A stiff counterpart to the more

malleable (RADA)4, EAKA’s structure is derived from the

yeast protein zuotin, specifically the amino acid sequence

(Ac-(AEAEAKAK)2-CONH2) (Chen & Zou,

2019

). Its

uniqueness lies in its rigidity, akin to driving a nail through a

soft medium (Kisiday et al.,

2002

These peptides, a product of meticulous research, com

prise alternating hydrophilic and hydrophobic residues (Kim

et al.,

2022

). The choreography between these residues gives

rise to

-sheet structures with distinct hydrophobic and

hydrophilic faces (Korendovych & DeGrado,

2020

). While

(

)

DI wa

ter

1.5

Ions

/salt

(

)

(

)

(

)

(

)

Fig. 20.5

How self-

assembled materials work,

what they look like, and what

the resultant fiber formation

looks like under a scanning

electron microscope (SEM).

(

) (RADA)4 molecule with

dimensions. This is mixed in

deionized water at various

concentrations. (

) (RADA)4

mixture added to the body,

which is water with high salt

content. The material

assembles into sheets as a

result of the aqueous

environment due to the

hydrophobic part trying to

hide from water. (

) Sheets

assembling into fibers and

forming a 3D structure in the

tube. (

) High hydration with

99% water. (

) The 20-nm

fiber structure is visualized

using an SEM. Scale bar

represents 200 nm (Ellis-

Behnke et al.,

2006b

)

D. S. Shevy et al.

313

the (RADA)4 sequence yields a supple scaffold in tune with

the dynamics of living tissues such as the brain, EAKA, with

its stiffer nature, is more specialized in its applications (Ye

et al.,

2008

Self-assembly and the Power of Environment

The age-old idea of materials passively fitting into their envi

ronments is being revolutionized (Schubert & Smulders,

2019

). Now, we see a paradigm where the environment

actively participates in molding the material (Sharma et al.,

2020

). When introduced to charged environments, these pep

tides undergo folding, showcasing the intimate relationship

between solvent and material (Aguayo-Ortiz et al.,

2018

The magic unfolds as a liquid introduced to a wound trans

forms, self-organizing to interact with nanoparticles native to

the injury site (Mitchison & Field,

2021

Further exploring the dynamism of the self-assembly pro

cess, once a sequence is infused into a site, it nucleates at the

tissue interface (Takeuchi et al.,

2005

). The peptides, sensing

the charge from the solvent, align in a manner that aids tissue

repair (Pramounmat et al.,

2022

). The entire orchestration is

swift, resulting in a structure harmonious with the native tis

sue (Gupta et al.,

2021

Beyond Two Sequences: The Universe

of Combinatorial Possibilities

While (RADA)4 and EAKA have demonstrated impressive

capabilities individually, the frontier of biomedical research

is pushing boundaries by delving into combinatorial possi

bilities (Dasgupta & Das,

2019

). By juxtaposing different

sequences or even creating solutions of two varied sequences,

the potential configurations are boundless (Chan et al.,

2017

Envision a future where scaffold materials are not just

homogenous sequences but also a symphony of mixed

sequences, each lending its unique capability to the structure

(Eldeeb et al.,

2022

). The resulting heterogeneity can pave

the way for biomaterials that can serve multidimensional

purposes, from scaffolding to drug delivery and beyond (Jin

et al.,

2020

In Retrospect and a Glimpse into the Future

Self-assembling peptides, from (RADA)4 to EAKA and

beyond, are redrawing the boundaries of biomaterial applica

tions (La Manna et al.,

2021

). With each new discovery, the

promise of regenerative medicine, targeted drug delivery,

and more becomes tangible.

Advances in SAPs

(RADA)4 and EAKA are prominent examples of self-

assembling peptides (SAPs) used in the biomaterials and

regenerative medicine fields (Chen & Zou,

2019

). However,

the world of SAPs is vast and rapidly evolving, with numer

ous peptides being studied for various applications, from

drug delivery to tissue engineering (Urciuolo et al.,

2023

Some Other Noteworthy SAPs Include

(RADA)4

It forms stable beta-sheet structures and has been widely

studied for neural tissue repair and scaffold creation (Koss

et al.,

2016a

EAKA

Known for its stiffness, it provides different mechanical

properties than RADA (Koss et al.,

2016a

RAD16-I (Ac-(RADA)4-CONH2)

RAD16-I and RAD16-II are both self-assembling peptides,

but they are variants with distinct sequences (Dégano et al.,

2009

). These sequences form stable beta-sheet structures

similar to RADA and have been investigated for their poten

tial in tissue engineering, particularly for applications in neu

ral tissue repair (Holmes et al.,

2000

RAD16-II

This is another peptide sequence derived from the (RADA)4

(Cho et al.,

2012

) structure. It has shown promise for neural

tissue regeneration and other applications similar to

(RADA)4 (Li et al.,

2007

). This peptide has a slightly differ

ent sequence, but like RAD16-I, it is also designed for self-

assembly. While both are used as biomaterials in regenerative

medicine and tissue engineering, the subtle differences in

their sequences might confer distinct biochemical and bio

physical properties (Fig.

20.6

) (Japan,

2016

KLDL, KLDF, and DLEU

These peptides are capable of forming beta-sheet structures

similar to (RADA)4, and they have been investigated for

their potential in biomedical applications. KLDL and KLDF

are related peptide sequences, but they are different due to

the change in the last amino acid (Lys-Leu-Asp-Leu and

Lys-Leu-Asp-Phe, respectively). DLEU is another sequence,

distinct from the two aforementioned ones (Li et al.,

2007

Protein Amyloids

This peptide can assemble into amyloid fibrils and has been

studied for potential use in nanotechnology and biomedical

applications (Almeida & Brito,

2020

; Wei et al.,

2017

Molecular Medical Devices for Nanoneurosurgery

314

Fig. 20.6

RADA16-I

self-assembles under suitable

physiochemical conditions

due to the polar amino acids

and hydrophobic interaction

and form

-sheet (Japan,

2016

)

FKFE

Another peptide known for its beta-sheet structure formation

and potential use in creating self-assembled peptide scaf

folds (Lee et al.,

2013

FEFEFKFK (P11–4)

The sequences FKFE and FEFEFKFK (often referred to as

P11–4) are related but different. P11–4 is a longer sequence

and has specific properties that make it unique (Yang et al.,

2020

). A peptide known for its ability to form hydrogels and

has potential applications in drug delivery.

This peptide, like others in its class, forms nanofibers and

can self-assemble into hydrogels under specific conditions.

Its applications have been explored in the field of dental

medicine, notably for pulp capping and the treatment of den

tin hypersensitivity.

MAX1 (VKVKVKVKVDPPTKVKVKVKV-NH2)

and MAX8

These peptides, designed through computational methods,

form stable

-sheet structures and can be used to create

hydrogels for cell culture and tissue engineering.

MAX1 and its derivatives have been used to create hydro

gels due to their self-assembly properties. The particular

sequence promotes beta-hairpin structures, which further

aggregate to form stable hydrogels. These hydrogels are par

ticularly interesting for drug delivery and cell

encapsulation.

Q11 (QQKFQFQFEQQ)

The Q11 peptide has been investigated for its potential use in

tissue engineering and regenerative medicine, specifically

for its ability to create scaffolds. Due to its properties, the

Q11 peptide can also be functionalized with bioactive sig

nals, enhancing its utility in medical applications (Rudra

et al.,

2010

Biomimetic Peptides

Some peptides are designed to mimic the properties of natu

rally occurring proteins or peptide sequences in the human

body. For example, sequences that replicate parts of collagen

or elastin have been synthesized. These biomimetic peptides

can provide environments similar to natural ECM, promot

ing cell adhesion, proliferation, and differentiation (Groß

et al.,

2015

Peptide Amphiphiles (PAs)

PAs are long-chain molecules with a hydrophilic peptide

sequence attached to a hydrophobic alkyl tail. They have the

ability to self-assemble into various structures such as nano

fibers, micelles, or vesicles. These PAs are versatile and have

been studied for applications ranging from drug delivery to

tissue engineering (Fuertes Llanos et al.,

2023

Recent Advancements

•

Self-assembling peptides, such as RADA and EAKA,

have garnered significant attention in the field of regen

erative medicine due to their biocompatibility, customiz

ability, and versatile applications. While RADA and

EAKA are among the more well-known self-assembling

peptides, researchers have explored a multitude of other

sequences for various applications.

•

The utility of these peptides is not just limited to their

self-assembling properties. Recent research has focused

on functionalizing these peptides to carry drugs, growth

factors, or other bioactive compounds, enhancing their

utility in tissue engineering or regenerative medicine.

•

There is also growing interest in combining these self-

assembling peptides with other materials (like polymers

or inorganic nanoparticles) to create composite materials

with enhanced properties.

•

Advanced manufacturing techniques, such as 3D bio

printing with self-assembling peptide inks, are also being

developed. This will allow for the precise creation of tis

sues or organs with intricate architectures (Li et al.,

2023b

•

Monitoring and controlling the kinetics of self-assembly

is another active area of research. By understanding and

D. S. Shevy et al.

315

manipulating how quickly and under what conditions

these peptides assemble, researchers can better tailor their

applications (Li et al.,

2023a

In summary, while RADA and EAKA are seminal

sequences in the field of self-assembling peptides, there is a

vast and growing library of peptides being developed for a

wide array of biomedical applications. The future of this

field is incredibly promising, with continual advancements

in both the understanding of self-assembly mechanisms and

the applications of these versatile materials (Mignon et al.,

2019

Nanomedicine: A Revolution

at the Nanoscale

Nanomedicine is a fascinating intersection of nanotechnol

ogy and medicine, extending its influence from the utiliza

tion of nanomaterials and biological devices (Soares et al.,

2018

) to the incorporation of nanoelectronic biosensors

(Ramesh et al.,

2023

) and, intriguingly, even to the potential

applications in molecular nanotechnology such as biologi

cally integrated machines.

It may sound unconventional, perhaps even counterintui

tive, to define medicine by scale. Yet, transitioning from the

microscale to the nanoscale is more than just a matter of

reduction in size (Damodharan,

2021

). This descent into the

nanorealm heralds dramatic alterations in properties, open

ing up a slew of unique and beneficial characteristics that

nanomaterials can offer (Malik et al.,

2023a

). For instance,

causing damage or creating openings in a cell at larger scales

would invariably lead to the cell’s death, or at the very least,

significantly impair its function due to trauma (Basera et al.,

2023

). Surprisingly, at the nanoscale, it is feasible to create

minuscule perforations in cells or monitor cellular compo

nents like proteins and pH levels without disturbing the cell’s

inherent activities (Capozza et al.,

2018

Such nano-level interventions echo the pioneering

efforts of in vitro fertilization (IVF) (Eskew & Jungheim,

2017

). The watershed moment in this domain came in 1997,

with assisted reproductive technology (ART) marking a

paradigm shift (Graham et al.,

2023

). Here, successful fer

tilization culminated in the birth of a baby with a unique

genetic constitution—contributions from three distinct

sources: DNA from the nucleus of one egg, cytoplasmic

DNA from a second egg, and the genetic material from a

sperm, with each source tracing back to a different donor

(Cohen et al.,

1997

). This groundbreaking approach, essen

tially nanosurgery of the cell, which may have seemed like

a futuristic dream at one point, has now been normalized

and is routinely practiced in IVF clinics around the world

(Shandilya et al.,

2020

This evolving realm of nanomedicine is reshaping our

understanding of medical interventions, illuminating paths

to innovative treatments and expanding the horizons of what

we deem possible in the world of medicine (Shi et al.,

2020

Nanoneurosurgery: Precision

at the Nanoscale

The contemporary surgical landscape is often marred by

visual obstructions like blood and debris, necessitating con

tinual irrigation with saline to maintain clarity (Pieper et al.,

2018

). Nanosurgery, however, offers a refreshingly clean and

clear paradigm, given the intrinsic transparency of nanoma

terials and the absence of macro-sized interferences.

CNS Regeneration: Bridging the Neural Gap

In the quest for regenerating the central nervous system

(CNS), re-establishing connections between severed parts is

pivotal (Andrews,

2009

). Reconnecting the optic nerve, a

critical component of the CNS, exemplifies this challenge

(Chiu & Miller,

2016

The solution found was fibrin glue, initially applied to

coat Dacron arterial grafts enhancing their biocompatibility

(Chiu & Miller,

2016

). Empirical studies later revealed that

the optic nerve could regenerate using a sciatic nerve bridge

between the eye and the superior colliculus, thus rejuvenat

ing both the nerve and its function (Ellis-Behnke et al.,

2006b

This fibrin sealant, composed of human fibrinogen and

thrombin, facilitates tissue reattachment and is commonly

employed in surgeries to assist hemostasias, especially when

conventional techniques are insufficient (Spotnitz,

2014

). Its

applications range from dura mater repairs and wound heal

ing to “no sutures” corneal transplantation and managing

postoperative pain. However, precautions are necessary

(Albala,

2003

), as its entry into the bloodstream can precipi

tate thromboembolism or disseminated intravascular coagu

lation. Also, its protein content can be denatured by

antiseptics containing ethanol, iodine, or heavy metals.

A nerve graft, serving as a conduit for damaged nerves,

can be autologous (from the patient) or allogeneic (from a

cadaver) (Rebowe et al.,

2018

). Optic nerve implantation

using a peripheral nerve bridge is a quintessential example.

This technique entails introducing a sciatic nerve implant

into the optic nerve sheath without hampering the eye’s

blood flow, ensuring continued ocular nourishment (Ahmed

et al.,

2020

Further experimentation disconnected the optic nerve

sheath from the eye to gauge retinal ganglion cells’ (RGCs)

survival and growth potential. Such investigations, preceding

Molecular Medical Devices for Nanoneurosurgery

316

the utilization of the self-assembled material (RADA)4,

highlighted three insights:

The necessity for a flowable, sealing, and reattaching

material.

The importance of biologically inert materials in preserv

ing cell and tissue integrity.

The potential to restore a major disrupted blood supply

with apt materials, facilitating vascular breakdown and

reconnection.

The rapid restoration of blood supply challenges previ

ous assumptions about retinal fragility. Despite these

experiments being in rodents, with potential differences in

vascular reconnection and clot dissolution between species,

the implications are profound. The challenges with fibrin

glue, such as shelf-life and disease transmission risks, point

toward the promise of self-assembling nanomaterials

(Zheng et al.,

2022

). Such materials polymerize, forming

covalent bonds that subsequently degrade, while other self-

assembling peptides (SAPs) undergo dynamic reconfigura

tions (Bruggeman et al.,

2019

). This interplay of

self-assembly and dynamism can be harnessed more effec

tively for CNS applications.

The revelation that fibrin glue promotes cell survival

paves the way for exploring other materials for neural

repair and reconstruction. Although the precise mecha

nisms remain partially obscured, some investigations sug

gest fibrin glue boosts the secretion of regenerative

cytokines like SDF-1 and bFGF (Xu et al.,

2019

), which

optimize wound healing, fibroblast function, and neovascu

larization, in addition to their coagulation functions source

(Hopfner et al.,

2018

In summation, nanoneurosurgery, with its emphasis on

precision and molecular-level interventions, holds immense

potential for CNS regeneration and offers promising avenues

for revolutionizing neurosurgical approaches.

Surgical Method of the Optic Nerve

With the rodent completely anesthetized, the superior rectus

and lateral rectus muscles of the eye were protruded and the

ON was exposed. In some cases, the superior oblique mus

cle also needed to be cut. Care was taken to allow suturing

of the muscles when the eye was placed back into the socket.

After the eye was protruded, both the ON and the nerve

sheath were severed posterior to the lamina cribrosa at the

point where the ON sheath joined the globe. This gave the

maximum surface area for the adherence of fibrin mixture.

The mixture was composed of thrombin, fibrinogen, and

calcium chloride, which were obtained from Sigma and

placed in separate containers. Each of these was placed in a

syringe, and the syringes were taped together, so they could

be applied simultaneously and in correct proportion to

achieve maximum binding and shortened polymerization

time. Since this was a pilot study, different concentrations

were used to analyze bonding time and material concentra

tion for the best results which would ensure the best chances

for the healing process with the least obstacles for blood

flow restoration and the ON reinnervation. The animals

were allowed to survive for 8 weeks, and histology was per

formed to determine RGC survival, tissue integrity, and

regeneration.

Results

The fibrin glue formed by the mixture allowed revasculariza

tion of the globe in less than 24 h. Although actual blood

flow was not measured, RGC survival was used as a metric

for revascularization. Rats and hamsters Retina die quickly

without perfusion for 48–72 h.

In this experiment, 50–80% of the RGBs survived point

ing out that blood flow to the ophthalmic artery was restored.

This was in sharp contrast to others’ work showing that 80%

of the RGCs died when the ON was severed behind the globe

without using the fibrin glue. Restoration of blood did estab

lish healing of the ON sheath. However, there was no rein

nervation of the RGCs past the transaction, which was

assessed by the cholera toxin B (CTB)–fluorescein isothio

cyanate (FITC) injection into the eye, the use of antibody to

CTB-FITC, and visualization with a fluorescent dye

(Fig.

20.7

Modern Advances

As we delve into the future, it is paramount to comprehend

the modern advancements in the realm of neurosurgery,

especially concerning the optic nerve. With the infusion of

nanotechnology, there is a notable shift toward minimally

invasive techniques. Advanced imaging modalities, includ

ing OCT angiography, are being utilized for better visualiza

tion, diagnosis, and surgical precision. Furthermore, the

synthesis of novel biomaterials, including stem cell-derived

matrices, is emerging, aiming for enhanced RGC survival

and potential regeneration. Newer research also underscores

the significance of neuroprotective agents that could aug

ment the survival and functioning of RGCs post trauma or

surgical intervention. As the medical field continues its

relentless march forward, it is hoped that these modern inter

ventions will revolutionize our understanding and manage

ment of optic nerve pathologies and injuries (References:

Various peer-reviewed articles and journals on neurosurgery

and ophthalmology).

D. S. Shevy et al.

317

)

Thrombin

Calc

ium

Fibri

Fibrinoge

Fibrin glue

(c)

(d)

)

(e)

Fig. 20.7

Repairing the brain

with fibrin glue. (

)

Components of fibrin glue

and cascade of how thrombin

and fibrinogen, along with

calcium, are added to form

fibrin glue. (

) Scanning

electron microscopy of fibrin

glue and the clot that forms as

a result of the clotting

cascade. (

) Locations of the

disconnection and treatment

of the mixture. (

) How ON is

reconnected at the same

location. (

) An eye showing

how reconnection happens

and how the resulting tissue

looks like after being

reconnected. This was

performed in hamsters, rats,

and mice. Picture shown is

that of a fixed rat eye. The

tissue appears normal as the

fibrin dissolves and as the

tissue heals. Scale bar

represents 10

m (Ellis-

Behnke et al.,

2006a

)

CNS Regeneration After Acute Injury

Nano Neuro Knitting

CNS Regeneration After Acute Injury:

The Promise of Nano Neuro Knitting

Introduction

One of the long-standing challenges in neurology and neuro

surgery has been the effective regeneration of the central ner

vous system (CNS) post-injury (Fawcett,

2020

). Traditional

approaches have been limited in their scope and efficacy.

However, with the advent of nanotechnology and its integra

tion into neuroscience, a new frontier has emerged—“nano

neuro knitting” (Ellis-Behnke et al.,

2006b

Concept of Nano Neuro Knitting

Derived from its nomenclature—“nano” refers to the

nanoscale, “neuro” relates to the CNS, and “knitting” reso

nates with the art of creating fabric through intricate inter

locking—the term “nano neuro knitting” embodies the

integration of these principles. It paints a picture of using

nanotechnology to interface with the nervous system, draw

ing parallels to knitting’s intricate loops to create or mend

fabric.

Methodology

Recent research has illuminated the potential of nano neuro

knitting in aiding partial reinnervation in damaged regions of

the CNS (Huebner & Strittmatter,

2009

). A prime example is

the utilization of (RADA)4, a self-assembling peptide. When

introduced into the environment of an injured nervous sys

tem, it forms nanofibers. These fibers, at a molecular level,

create a scaffold-like structure, acting as a bridge or lattice

over damaged areas. The immediate advantage of this is the

creation of a supportive environment conducive to the

regrowth of axons with inherent regenerative capabilities.

An important aspect highlighted in studies, such as the

one by Ellis-Behnke et al. in 2006b, is the prevention of early

scar formation, a common challenge post-injury. The

(RADA)4 scaffold not only promoted axonal growth but also

deterred the scar formation process (Ding et al.,

2023

). A

remarkable outcome of this study was the reversal of func

tional deficits, notably reversing blindness in hamsters

through the regeneration of the optic tract (OT).

Benefits and Implications

The Implications of Nano Neuro Knitting Are Profound

Precision: By working at the nanoscale, there is an ele

vated level of precision that was not possible with earlier

methods. This precision ensures minimal interference

Molecular Medical Devices for Nanoneurosurgery

318

with healthy tissue and a targeted approach to the injured

site (Arumov et al.,

2021

Functionality Restoration: The technique does not just

promote tissue healing; it aids in the restoration of func

tionality, which is the ultimate objective post-CNS injury

(Krucoff et al.,

2019

Inhibiting Scar Formation: Scar formation, often a hin

drance to regeneration, is deterred, thereby promoting

unhindered tissue repair (Krucoff et al.,

2019

Future Prospects

Despite its promise, nano neuro knitting remains in its

nascent stages. That said, the amalgamation of nano bio

medical technology and molecular self-assembly in CNS

repair is undeniably exciting (Panda et al.,

2021

). In envi

sioning the future of CNS repair, one cannot help but be

hopeful (Tran et al.,

2018

). As technology and research

evolve, it is conceivable that nano neuro knitting could revo

lutionize the way we approach, understand, and treat CNS

injuries. It is not just about mending tissues; it is about

restoring lives.

Surgical Methods for Eye Vision Restoration:

Exploring Nano Neuro Knitting

Introduction:

Advancements in surgical methods, specifi

cally in the realm of nanotechnology, are drastically altering

the landscape of eye vision restoration. One prime example

of this is the concept of “nano neuro knitting,” a process that

employs self-assembling peptides to reconnect disconnected

neurons, not just around the wound but through the very cen

ter of it.

Research Approach:

The primary aim was to bridge the

gap created by injury in the central nervous system (CNS),

specifically the optic tract (OT). To illustrate the efficacy of

this technique, both young and adult Syrian hamsters under

went surgery.

Young Animals:

53 young Syrian hamsters were used, with

the optic tract (OT) within the superior colliculus (SC) being

completely severed. This ensured no possibility of spontane

ous regeneration around the lesion. Of these animals:

•

10 were treated with a 10-

L injection of 1% (RADA)4.

•

6 were given isotonic saline as controls.

•

27 received no injection.

These hamsters were then monitored for varying dura

tions: 24 h, 72 h, 30 days, and 60 days post-surgery.

Adult Animals:

16 Syrian hamsters underwent a similar

procedure. The Brachium of the superior colliculus (BSC)

was transected. Notably, a 2-mm-deep incision was made to

prevent axonal growth around the lesion, compelling it to

pass through the center of the injury.

Assessment of Vision:

Vision restoration was evaluated

using a behaviorally anchored system. The hamsters’ visu

ally triggered orienting eye movement was tested, using sun

flower scenes as the stimulus. Each session lasted 10–20 min

every other day, where sunflowers were presented 10 times

on each side.

Findings:

Tissue Restoration

: In the case of young animals treated

with (RADA)4, the initial gap from the injury was signifi

cantly reduced within the first 24 h and was either drasti

cally diminished or completely eliminated by 72 h,

30 days, and 60 days. Adult animals presented similar out

comes, showcasing that the technique is age independent.

Axonal Restoration

: Functional connectivity was assessed

by using a fluorescently tagged CTB fragment. This acted

as a regeneration marker across wounds. A staggering

92% of treated cases showed evidence of regenerated

axons in the SC.

Behavioral Results

: Functionally, 75% of the adult ani

mals treated demonstrated a restored ability to visually

orient toward stimuli. This directly correlated with axonal

regeneration, indicating that the structural repair trans

lated to functional recovery. In comparison, controls

remained visually impaired.

Figures:

•

Figure

20.8

illustrates the young animals’ brain repair. It

compared control and treated cases and showed the

repaired region in the latter. Additionally, it offered a

microscopic view of the self-assembling material in the

brain.

•

Figure

20.9

depicts adult brain repair. It highlighted ana

tomical structures like the SC, PT, LP, MGB, LGB, and

IC. Furthermore, it visualized the regenerating axons in

(RADA)4 treated animals compared to saline-treated

controls.

•

Figure

20.10

depicts the behavioral results. Seventy-five

percent of treated animals responded significantly better

than blind controls. As the tests progressed, the vision of

the treated group notably improved.

Conclusion:

The study illuminates the potential of “nano

neuro knitting” as an effective technique for CNS and optical

D. S. Shevy et al.

319

(a)

Knif

e cut.

in SC

)(

(d)

Fig. 20.8

Repairing the brain of young animals. (

) Parasagittal view

of an adult hamster brain showing a schematic representation of the

lesion (blue) that transects the OT in the middle of the SC in young

animals. (

) Control at 1 month after lesion showing the gap formed

without regeneration. (

) Treated case at 1 month after lesion and treat

ment showing repair of the brain (arrows). (

) Inset: Scanning electron

microscopy of material as it self-assembles in the brain. Scale bar rep

resents (

) 500

m, (

) 100

m, and (

) 1

m (Ellis-Behnke et al.,

2006a

)

(a)

Optic

tra

)(

Fig. 20.9

Repairing the brain of adult animals. (

) Dorsal view recon

struction of the hamster brain with the cortex removed. Rostral to the

left, and caudal to the right. Anatomical structures include the SC, pre

tectal area (PT), lateral posterior nucleus (LP), medial geniculate body

(MGB), lateral geniculate body (LGB), and inferior colliculus (IC). The

red line depicts the location of the transection of the OT (brachium of

the SC) made at 3 months. (

) Enlarged view of the area rostral to the

lesion site showing CTB-FITC-labeled axons stopped before the gap

(large arrow) created by the injury in the saline-treated control animal.

The gap was formed with saline treatment (star). (

) Labeled regenerat

ing axons crossing the injured region and growing toward the target in

the (RADA)4-treated animal. The location of the healed lesion and the

approximate location of the injury (arrows) are shown. Scale bars rep

resent (

) 100

m and (

) 25

m (Ellis-Behnke et al.,

2006a

)

injuries. With a high success rate in both young and adult

subjects, it offers a promising avenue for surgical interven

tions aiming to restore vision post-injury.

The potential of nano neuro knitting underscores the

importance of continued research in this area, making way

for possible clinical applications in the foreseeable future.

Other Agents to Enhance Regeneration

Results

At the molecular level, the processes of renewal and regen

eration are steered by a diverse range of soluble bioactive

agents. These agents span a broad spectrum, from neu

rotransmitters, short peptides, and chemokines to growth

Molecular Medical Devices for Nanoneurosurgery