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Monitoring nanoprobe diffusion in osmotically-stressed hydrogels

  • Hacene Boukari (a1), Candida de Silva (a2), Ralph Nossal (a3) and Ferenc Horkay (a4)

Abstract

We have developed an optical chamber for studying the effect of swelling or shrinking of a gel on the translational diffusion of fluorescent nanoprobes embedded in the gel. On one side of the chamber, the gel is in contact with a hydrating or dehydrating polymeric solution through a porous membrane, allowing control of the rate of hydration or dehydration of the gel. On the other side, a laser beam is focused into the gel to excite the fluorescence of the nanoprobes, which is continuously monitored to reveal possible structural changes of the stressed gel. Using fluorescence correlation spectroscopy we measure correlation functions of the nanoprobes at various times following the contact of the gel with the hydrating or dehydrating solution, and determine changes of both the average concentration and the apparent diffusion time of the nanoprobes as the gel is shrinking or swelling. We have tested the chamber using the fluorophore, TAMRA (MW = 430 Da), embedded in a poly(vinyl-alcohol) gel that is being dehydrated by a solution of poly(vinyl-pyrrolidone) (28% w/w). As expected TAMRA moves slower as the gel shrinks. However, the changes in the diffusion time of TAMRA as a function of the PVA concentration of the shrinking gel appear to be different than those measured on TAMRA diffusing in PVA gels prepared at different PVA concentrations but with the same cross-link density.

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Monitoring nanoprobe diffusion in osmotically-stressed hydrogels

  • Hacene Boukari (a1), Candida de Silva (a2), Ralph Nossal (a3) and Ferenc Horkay (a4)

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