Bupivacaine-eluting soy protein structures for controlled release and localized pain relief: An in vitro and in vivo study

Burn pain is known to be excruciating, and while burn care has greatly advanced, treatment for burn-related pain is lacking. Current pain relief methods include systemic administration of analgesics, which does not provide high drug concentration at the wound site. In the present study, soy protein was used as the base material for bupivacaine-loaded hybrid wound dressings. The effect of the formulation on the drug release profile was studied using high performance liquid chromatography, and the cytotoxicity was tested on human fibroblasts. A second-degree burn model in rats was used to quantify the efficacy of the wound dressings in vivo, using the Rat Grimace Scale. All tested films exhibited high biocompatibility, and the drug release profiles showed rapid release during the initial 5 hr and a continuous slower release for another 24 hr. Significant pain relief was achieved in the animal trials, proving a decrease of 51–68% in pain levels during days 1–3 post-burn. Hence, the results indicate a safe and controlled bupivacaine release for a period of more than 24 hr, effectively treating pain caused by second-degree burns. The understanding of the formulation-properties effects, together with our in vivo study, enables to advance this field toward tailorable systems with high therapeutic potential.