Injectable Silk Fibroin-Based Hydrogel for Sustained Insulin Delivery in Diabetic Rats

Diabetes is a chronic disease affecting over 400 million people worldwide. Inadequate production of insulin due to loss of beta cells or insulin resistance within the body imbalances the glucose homeostasis, resulting in an abrupt increase of blood glucose level. The conventional and last resort of treatment involves repeated subcutaneous insulin injections to maintain the physiological glucose homeostasis. However, continuous and multiple subcutaneous injections are associated with poor patient compliance and local amyloidosis of insulin, which can be overcome with controlled and sustained insulin delivery. In this context, we have designed and formulated an injectable silk fibroin hydrogel (iSFH) to realize sustained insulin delivery over a prolonged period under diabetic conditions. The specific composition of glycol additives (ethylene glycol and triethylene glycol) allowed the silk fibroin protein to form an injectable hydrogel within 50 min. The detailed characterization of iSFH by a field-emission scanning electron microscope displayed the desired mesoporous structures, which are appropriate for drug (insulin) encapsulation in its active form. Interestingly, the subcutaneous injection of iSFH-encapsulated insulin (insulin-iSFH) in diabetic T1DM Wistar rats showed controlled release of insulin and restored physiological glucose homeostasis up to 4 days. The biocompatible and biodegradable nature of iSFH makes it a potential drug delivery system for active storage, and controlled and sustained delivery of insulin in diabetic conditions to maintain the physiological glucose level.