Keratin sponge/hydrogel II: Active agent delivery

Abstract

Keratin sponge/hydrogels, described in Part I as the products of oxidation and reduction hydrolysis of fine and coarse wool fibers, were examined as excipient-platforms for the delivery of riboflavin. By absorption through well-defined pores and networks, saturated moisture equilibrium was reached within one hour with swelling ratios of 3.7–5.7. Riboflavin uptake by the four different keratin sponge/hydrogels was from 27.9 to 224 µg. Within 60 minutes, reductive keratin sponge/hydrogels from fine and coarse wool, and the oxidative species from fine wool, released 100% riboflavin at 1.58–1.73% per minute and oxidative sponge/hydrogel from coarse wool released 48% riboflavin at 0.8% riboflavin per minute. Rates of riboflavin release were faster within the initial 10 minutes where reductive sponge/hydrogels released 80–84% riboflavin at 8.0–8.4% per minute and oxidative sponge/hydrogels released 26–63% riboflavin at 2.6–6.3% per minute. Riboflavin delivery at timed intervals was examined with the Korsmeyer–Peppas mathematical model for fractional release. Release patterns followed quasi-Fickian diffusion of the drug by transport through channels and voids. All keratin sponge/hydrogels functioned as site-specific agents with two-stage delivery where immediate release of riboflavin was followed by a period of prolonged, lower dosage release. Swelling studies, the mobility of water, and the behavior of riboflavin release favorably framed keratin sponge/hydrogels as microfluidic devices with implied applications for advanced biomedical and biotechnological applications.