Enhancing the Electrical Conductivity of Electrospun PCL Fibers by Coating with Polydopamine and In Situ Gold Nanoparticles Doped on the Polydopamine Coating

Polycaprolactone (PCL) is a synthetic biodegradable polymer widely used in biomedical research due to its flexibility, safety for use in the body, and FDA approval for medical use. Nevertheless, its inherent hydrophobicity and restricted bioactivity limit its direct utilization in the field of biomaterials. Efforts to overcome these limitations include, but are not limited to, surface modifications, coating, and the use of copolymers of PCL with hydrophilic polymers. Polydopamine (PDA), the oxidative polymerization product of dopamine, a naturally occurring biomolecule in living organisms, is a flexible, bioinspired coating that makes surfaces more hydrophilic and facilitates cell attachment by incorporating numerous catechol and amine functional groups, making it suitable for biomaterial applications. PCL nanofibers were coated with PDA in three concentrations of dopamine solutions (0.2, 2, and 20 mg·mL^-1). Then, gold nanoparticles (AuNPs) were deposited in situ using sodium borohydride reduction. Morphological, physicochemical, and electrical properties of both PDA-coated and AuNP-loaded PCL fibers were comparatively investigated. The PDA coating made the surface significantly more hydrophilic compared to PCL-only surfaces, and AuNP-loaded fibers exhibited an extremely hydrophilic character. The primary concern of this article, electrical conductivity, was found to increase by up to a hundredfold with PDA coating and by a thousandfold with loading of AuNPs. PDA coating or loading AuNPs onto PDA-coated electrospun PCL fibers can provide a wide range of applications in the field of biomaterials.