1
Supporting Information
Enhanced broadband fluorescence detection of
nucleic acids
using multipolar gap
-
plasmon
s
on biomimetic Au metasurfaces
Vinayak Narasimhan
,
a
Radwanul Hasan
Siddique,
a
Magnus Hoffmann,
b
Shailabh Kumar
a
and
Hyuck Choo
a
*
a
Department of Medical Engineering
,
California Institute of Technology
,
Pasadena, CA
91125
,
USA
b
Department of Biology
and
Biological Engineering, California Institute of Technology
,
Pasadena, CA 91125, USA
*
E
-
mail:
hyuck.choo@samsung.com
;
hchoo@caltech.edu
F
ig
.
S
1
The absorption (dotted black) and scattering (solid red) cross sections in the Vis
-
NIR
regime of
(
a) the
l
= 1 dipolar mode of smaller MIM structures with diameters from 50
–
80
nm and
(
b) the
l
= 2 quadrupolar mode of larger MIM structures with diameters from 200
–
500 nm. The ratio of the scattering to absorption cross section is considerably higher for the
l
= 2 mode compared to the
l
= 1 mode.
Electronic
Supplementary
Material
(ESI)
for
Nanoscale.
This
journal
is
©
The
Royal
Society
of
Chemistry
2019
2
Fig
.
S
2
. Schematic illustrations of different phases of the 3
-
dimensional phase separation
process of the self
-
assembly technique (adapted from
1
).
3
F
ig
.
S
3
.
(
a) Normalized |E|
2
enhancement computed through FDTD experienced by emitters
at various distances from the plasmonic hotspot of an MIM structure of diameter 340 nm. The
diameter corresponds to the mean diameter of the samples used the work. Dotted lines
correspond to the ex
citation maxima of each fluorophore used in the study. NHS ester
corresponds to a distance of ~ 0 nm while
(
b) PEG 600, PEG 1000 and PEG 2000 correspond
to distances of ~ 0, 7, 8
.75 and 11 nm respectively
.
2
(
c) Fluorescence enhancement factor of
Alexa Fluor 647 at various distances from the plasmonic hotspot of the MIM
-
MS.
Numerically computed enha
ncement factors for the same distances are plotted as dots.
F
ig
.
S
4
.
(
a) The radiative (
훾
"
,
solid), nonradiative (
훾
#"
,
dashed) and total (
훾
$%$
,
dotted) decay
rates versus wavelength at an emitter distance of 0 nm from an MIM structure of diameter 340
nm computed through FDTD. The vertical dotted lines correspond to the emission maxima of
the fluorophores used in the study. The peak position of
훾
"
correlates well with the plasmon
resonance wavelength of the
l
= 2 mode of the structure.
(
b) High absorption for wavelengths
less than 500 nm which corresponds to losses through nonradiative channels is due to high
intrinsic material losses.
3
(
c)
훾
"
and
훾
#"
versus distance for the fluorophores used in the study.
4
Fig
.
S
5
.
The absorption (dotted black) and scattering (solid red) cross sections of
(
a
) a 340 nm
MIM struct
ure and
(
b
) a 100 nm nanodisk with a matching plasmon resonance computed
through FDTD. The resonance of the nanodisk is considerably narrower.
(
c
) The
훾
"
and
훾
#"
for the MIM structure and nanodisk at various distances computed through FDTD. In most
cases,
the
훾
"
for the MIM structure is orders of magnitude greater than the nanodisk.
(
d
) The
structurally
-
induced quantum yield
휂
for a emitter with an intrinsic quantum yield of unity (
휂
'
= 1) for various distances computed through FDTD. The nanodisk quenches the emitter for
distances < 10 nm while the MIM structure suppresses quenching.
5
Fig
.
S
6
. The design of capture and detection hybridization oligonucleotides using NUPACK.
4
The base sequence range indicated in black (
gag
: bases 1
–
19,
CD4
: bases 1
–
20 and
CCR5
:
bases 1
–
33) and red (
gag
: bases 71
–
100,
CD4
: bases 36
–
56 and
CCR5
: bases 83
–
100)
correspond to the location of binding of the capture and det
ection oligos respectively. Regions
with a high probability of secondary structure formation were avoided.
Fig
.
S
7
. Fluorescence micrographs of 100
-
bp CD4 sequence captured and detected from a
concentration of 10 pM to 10
μ
M.
6
Fig
.
S
8
.
Normalized fluorescence intensity for the
20
-
bp
CD4
capture oligo conjugated with
AF647
.
The biosensing of such a small sequence is enabled by the supression of quenching by
the quadrupolar mode of the MIM
-
MS.
Fig
.
S
9
. Flow cytometry histogram indi
cating high expression of CD4 glycoprotein on the
surface of transfected Expi293 cells (red) in comparison to untransfected but labeled Expi293
cells (green) and untransfected unlabeled Expi293 cells (blue).
References
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2
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