Monitoring small molecule diffusion into hydrogels at various temperatures by fluorescence technique

Steady state fluorescence technique was used to study small molecule diffusion into polyacrylamide (PAAm) gels at various temperatures. Pyranine (Py), dissolved in water was introduced as a probe and fluorescence emission (Ip) from Py was monitored during diffusion. Scattered light intensities, Isc from PAAm gel was also monitored to observe structural variations during diffusion process. Increase in Ip intensity was attributed to Py diffusion into PAAm gel. On the other hand decrease in Isc intensity was interpreted as the variation of the spatial heterogeneities in the system. Li-Tanaka and Fickian models were used to quantify the swelling and diffusion experiments and diffusion coefficients were produced in both cases. Related activation energies were also calculated from the corresponding physical processes.