Effect of glycerol on sustained insulin release from PVA hydrogels and its application in diabetes therapy

The present study aimed to investigate the effects of glycerol on the physical properties and release of an insulin‑loaded polyvinyl alcohol (PVA) hydrogel film. The insulin‑loaded hydrogel composite film was produced using the freeze‑thawing method, after which the in vitro swelling ratio, transmittance and insulin release, and the in vivo pharmacodynamics, of hydrogels containing various volumes of glycerol were investigated. The results demonstrated that the addition of glycerol reduced the swelling ratio and increased the softness of the PVA hydrogel film. An analysis of insulin release in vitro and of the hypoglycemic effects in rats demonstrated that the PVA hydrogel film had a sustained release of insulin and long‑acting effect over 10 days. The results of the present study suggested that, as a hydrophilic plasticizer, glycerol was able to enhance the release of insulin in the early stage of release profile by enhancing the formation of water channels, although the total swelling ratio was decreased. Therefore, the insulin‑loaded glycerol/PVA hydrogel film may be a promising sustained‑release preparation for the treatment of diabetes.