Novel Analgesic Drug Eluting Soy Protein Films as Wound Dressings: An In Vivo and In Vitro Study

Background: Burn pain is considered 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 risking severe side effects and bringing to low drug concentrations at the wound site. In our study, soy protein is used as a base material for drug eluting wound dressings which are biocompatible, relatively cheap and provide controlled and local release of analgesic agents.

Methods: Different formulations of wound dressings loaded with bupivacaine, an anesthetic, were prepared. Cytotoxicity of the films was tested on human fibroblasts using Alamar-Blue assay and drug release profiles were characterized using HPLC. In vivo tests were performed on rats in a second-degree burn model, quantifying pain relief capabilities of the dressing using von Frey filaments and the Rat Grimace Scale method.

Results: Cytotoxicity tests indicated good viability for all film formulations tested, with no significant differences among the various bupivacaine concentrations. Drug release profiles showed rapid release during the initial 5 hours and a continuous slower release for another 24 hours. Significant pain relief was achieved in both pain evaluation methods in the animal trials, proving that the dressing decreases both mechanically induced and spontaneous pain for at least three days post-burn.

Conclusions: Our results indicate a safe and controlled release of bupivacaine for a period of more than 24 hours, effectively treating pain caused by second-degree burns. Our technology presents a new concept in the field of pain management, already at first response care.