Brush-like Polymer Surface on Silk Fibroin Films for Controlled Release of Local Anesthetics

Postsurgical pain management remains a persistent challenge for patients and healthcare providers. This work presents an implantable, degradable drug release platform based on silk biomaterials designed to be placed at a desired surgical site intraoperatively to release the local anesthetic bupivacaine in a sustained manner to prevent and treat postsurgical pain. Methacrylate monomers containing different pendant groups are used to generate brush-like polymers on silk fibroin films by surface-initiated reversible addition-fragmentation chain transfer polymerization. These brushes have side groups to control polymer hydrophilicity and facilitate drug attachment via a hydrolyzable tether. Spectroscopy and contact angle goniometry are used to characterize the chemical composition and hydrophobicity of the synthesized films at each synthetic step. In vitro culture and in vivo implant studies show no differences in biocompatibility compared with unmodified silk films. Bupivacaine can be continually released for at least 7 days. The amount of drug released in vitro is increased by increasing the hydrophilicity of the brush-like polymer, and the released anesthetic is effective at blocking the conduction of action potentials of C-fibers and Aδ-fibers ex vivo. These degradable films show promise as a platform to achieve controllable, continuous delivery of local anesthetics for pain control after surgery.