Colloid surface chemistry critically affects multiple particle tracking measurements of biomaterials

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Characterization of the properties of complex biomaterials using microrheological techniques has the promise of providing fundamental insights into their biomechanical functions; however, precise interpretations of such measurements are hindered by inadequate characterization of the interactions between tracers and the networks they probe. We here show that colloid surface chemistry can profoundly affect multiple particle tracking measurements of networks of fibrin, entangled F-actin solutions, and networks of cross-linked F-actin. We present a simple protocol to render the surface of colloidal probe particles protein-resistant by grafting short amine-terminated methoxy-poly(ethylene glycol) to the surface of carboxylated microspheres. We demonstrate that these poly(ethylene glycol)-coated tracers adsorb significantly less protein than particles coated with bovine serum albumin or unmodified probe particles. We establish that varying particle surface chemistry selectively tunes the sensitivity of the particles to different physical properties of their microenvironments. Specifically, particles that are weakly bound to a heterogeneous network are sensitive to changes in network stiffness, whereas protein-resistant tracers measure changes in the viscosity of the fluid and in the network microstructure. We demonstrate experimentally that two-particle microrheology analysis significantly reduces differences arising from tracer surface chemistry, indicating that modifications of network properties near the particle do not introduce large-scale heterogeneities. Our results establish that controlling colloid-protein interactions is crucial to the successful application of multiple particle tracking techniques to reconstituted protein networks, cytoplasm, and cells.
Publisher
BIOPHYSICAL SOCIETY
Issue Date
2004-06
Language
English
Article Type
Article
Keywords

SELF-ASSEMBLED MONOLAYERS; ACTIN NETWORKS; COMPLEX FLUIDS; DISPERSION POLYMERIZATION; VISCOELASTIC MODULI; PROTEIN ADSORPTION; SOFT MATERIALS; F-ACTIN; MICRORHEOLOGY; FILAMENT

Citation

BIOPHYSICAL JOURNAL, v.86, no.6, pp.4004 - 4014

ISSN
0006-3495
DOI
10.1529/biophysj.103.037812
URI
http://hdl.handle.net/10203/83624
Appears in Collection
ME-Journal Papers(저널논문)
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