Transport of Glucose and Poly(ethylene glycol)s in Agarose Gels Studied by the Refractive Index Method

Abstract

The diffusion of glucose and a series of poly(ethylene glycol)s (PEG, average molecular weight = 200, 600, 1000, 10000) in agarose gels (in the range of 0.5−3%, w/w) have been studied with a novel refractive index method developed in our laboratory. The change of the gel refractive index caused by the change of the diffusing solute concentration in the gel during the diffusion process enables the effective solute diffusion coefficients to be computed. The change in glucose concentration in agarose gel with the diffusion distance and the diffusion kinetics of glucose in agarose gels reveal that glucose diffuses freely within these gel matrixes with a high diffusion coefficient ∼6 × 10-10 m2/s for 0.5% and 1.5% agarose gels. However, the diffusion coefficients of PEGs in the gel are generally in the range of (0.7−5.9) × 10-10 m2/s and decrease with an increase in the network density (higher agarose gel concentration) and/or in the molecular weight of the diffusing solutes. It is observed that the molecular ...