Multifunctional Bio-Inspired Biomedical Adhesive Featuring Instant Adhesion for Topical Drug Delivery

Abstract

This report presents the synthesis and characterization of a new biomedical adhesive featuring instant adhesion properties for a potential application in topical drug delivery on a localized area. This new biomedical adhesive is synthesized through thermally initiated radical polymerization and consists of: 1) a mussel-inspired repeating unit (catechol), which provides strong biomedical adhesion, biocompatibility, and robust skin interactions, and 2) 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), an anionic repeat unit known for its biocompatibility, drug delivery capabilities, and electrostatic interactions. This combination leads to a multifunctional biomedical adhesive that offers instant adhesion to the skin without the need for additional crosslinkers. The resulting copolymer, poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-N-methacryloyl 3,4-dihydroxyl-L-phenylalanine), further known as poly(AMPS-co-MDOPA), was tested both on PET film as well as porcine skin to quantify the adhesion properties and compare the setting times of the adhesive. A small amount (30 mg on dry PET surface, 100 mg on wet porcine skin) of adhesive was able to achieve a maximum strength of 105 kPa on dry PET substrate in lap shear strength test, and 3.1 kPa on wet porcine skin following only 5 minutes of application time. 1H NMR was performed to confirm the chemical structure of the polymer, demonstrating successful synthesis with a repeating unit ratio of 88:12 for AMPS:MDOPA. The polymer showed no cytotoxicity when exposed to primary human dermal fibroblasts, proving the polymers’ excellent biocompatibility. In separate tests, the new polymer demonstrated significantly lower cytotoxicity compared to a commercial sunscreen approved for use on human skin. In tests using proliferating human dermal fibroblast cells, the combination of the new poly(AMPS-co-MDOPA) (7.5 mg/mL) with sodium valproate (2 mM) effectively triggered cell death, demonstrating successful drug delivery. Due to high / instant skin adhesion, soft nature, biocompatibility, and drug efficiency, this new copolymer shows great promise as a biomedical adhesive for skin tissue, offering a comfortable and efficient alternative to drug-containing topical ointments by extending the residual of the drug at a localized skin site.