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Controlling nonspecific protein adsorption in a plug-based microfluidic system by controlling interfacial chemistry using fluorous-phase surfactants

Roach, L. Spencer and Song, Helen and Ismagilov, Rustem F. (2005) Controlling nonspecific protein adsorption in a plug-based microfluidic system by controlling interfacial chemistry using fluorous-phase surfactants. Analytical Chemistry, 77 (3). pp. 785-796. ISSN 0003-2700. doi:10.1021/ac049061w.

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Control of surface chemistry and protein adsorption is important for using microfluidic devices for biochemical analysis and high-throughput screening assays. This paper describes the control of protein adsorption at the liquid-liquid interface in a plug-based microfluidic system. The microfluidic system uses multiphase flows of immiscible fluorous and aqueous fluids to form plugs, which are aqueous droplets that are completely surrounded by fluorocarbon oil and do not come into direct contact with the hydrophobic surface of the microchannel. Protein adsorption at the aqueous-fluorous interface was controlled by using surfactants; that were soluble in fluorocarbon oil but insoluble in aqueous solutions. Three perfluorinated alkane surfactants capped with different functional groups were used: a carboxylic acid, an alcohol, and a triethylene glycol group that was synthesized from commercially available materials. Using complementary methods of analysis, adsorption was characterized for several proteins (bovine serum albumin (BSA) and fibrinogen), including enzymes (ribonuclease A (RNase A) and alkaline phosphatase). These complementary methods involved characterizing adsorption in microliter-sized droplets by drop tensiometry and in nanoliter plugs by fluorescence microscopy and kinetic measurements of enzyme catalysis. The oligoethylene glycol-capped surfactant prevented protein adsorption in all cases. Adsorption of proteins to the carboxylic acid-capped surfactant in nanoliter plugs could be described by using the Langmuir model and tensiometry results for microliter drops. The microfluidic system was fabricated using rapid prototyping in poly(dimethylsiloxane) (PDMS). Black PDMS microfluidic devices, fabricated by curing a suspension of charcoal in PDMS, were used to measure the changes in fluorescence intensity more sensitively. This system will be useful for microfluidic bioassays, enzymatic kinetics, and protein crystallization, because it does not require surface modification during fabrication to control surface chemistry and protein adsorption.

Item Type:Article
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URLURL TypeDescription CentralArticle Information
Ismagilov, Rustem F.0000-0002-3680-4399
Additional Information:Copyright © 2005 American Chemical Society. Published In Issue: February 01, 2005. Received for review June 27, 2004. Accepted October 29, 2004. This work was supported by the NIH (R01 EB001903), Dupont Young Professor Award (R.F.I.), the Burroughs Wellcome Fund Interfaces Fellowship No. 1001774 (L.S.R.) and the Predoctoral Training Grant (H.S.) of the NIH (GM 08720). At the University of Chicago, work was performed at the MRSEC microfluidic facility funded by the NSF. We thank Yelena Koldobskaya for help with numerical simulations. Supporting Information Available: Additional information as noted in text:  details of R_f -OEG extraction; drop tensiometry measurements for alkaline phosphatase at interfaces that presented each one of the three following surfactants:  R_f -COOH, R_f -CH_2CH_2OH, or R_f -OEG; tensiometry data for variable concentrations of fibrinogen at an interface that presents the R_f -COOH surfactant; tensiometry data for the adsorption of concentrated fibrinogen to a pure fluorocarbon interface, and also Selwyn's plots for alkaline phosphatase kinetics measured within a microfluidic device for plugs formed with each one of the following three surfactants:  R_f -COOH, R_f -CH_2CH_2OH, or R_f -OEG. This material is available free of charge via the Internet at
Funding AgencyGrant Number
NIBIBR01 EB001903
DuPont Young Professor GrantUNSPECIFIED
Burroughs Wellcome Fund Interfaces1001774
NIHGM 08720
Subject Keywords:self-assembled monolayers; water-soluble surfactants; bovine serum-albumin; droplet formation; fibrinogen adsorption; poly(ethylene glycol); tension measurements; air/water interface; liquid interfaces; microchannel emulsification
Issue or Number:3
Record Number:CaltechAUTHORS:20130821-160729676
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40858
Deposited By: Whitney Barlow
Deposited On:28 Aug 2013 18:39
Last Modified:10 Nov 2021 00:09

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