Preparation and In Vitro Characterization of Crocin-loaded Casein Hydrogels

Crocin, the main active constituent of saffron, has many important biological activities. Due to its anti-inflammatory properties, crocin can be potentially effective in different pathological conditions including oral ulcers. Novel drug delivery systems such as hydrogels have been used to increase the stability of crocin and provide a controlled release of this compound. Casein is the main protein of milk that possesses suitable properties for the fabrication of hydrogels. In this paper, casein-based hydrogels with different casein to crocin weight ratios were synthesized using the acid-gelation method. The prepared crocin-loaded hydrogels were characterized regarding their rheological behavior, drug content, swelling ratio, surface morphology, thermal stability, and in vitrorelease profile. The structure of casein hydrogels was characterized using Fourier transform infrared and X-ray diffraction. All formulations exhibited a pseudoplastic rheological behavior and there was no statistically significant difference in viscosityamong them. Hydrogel with casein to crocin weight ratio of 10:1 had larger pores and demonstrated a higher swelling percentage and suitable thermal stability. All casein-based hydrogels demonstrated a slow release of crocin over 24 hours and the hydrogel with lower casein to crocin weight ratio had an increased release rate. Taken together, casein-based hydrogels were found to be effective carriers to provide a controlled release system for crocin delivery.