Dissolving PEGDA-Based Microneedles to Transdermally Deliver PDA@Cu with Photothermal Properties for Potential Antibacterial Applications

The stratum corneum of the skin functions as a barrier, obstructing drug absorption and complicating the treatment of skin infections caused by pathogens such as bacteria, fungi, and viruses through topical methods. In this research, a microneedle patch was developed, which consists of gelatin-sucrose (SG) that encapsulates polydopamine-copper nanoparticles (PDA@Cu) at the tip for antibacterial purposes. Poly(ethylene glycol) diacrylate (PEGDA) served as the primary substrate for the microneedle shaft (PDA@Cu-SG/PEGDA). This patch was engineered to enhance skin permeability and facilitate the efficient delivery of drugs through the rapid dissolution of the tips. Coordinate bonds can be formed between PDA and Cu ions, resulting in the immobilization of Cu particles on the PDA surface, which aids in the green synthesis of PDA@Cu photothermal antibacterial particles. The SG polymer, which contained PDA@Cu, was employed to fill the tip cavities through a series of centrifugation steps. Subsequently, UV-induced polymerization was carried out to produce PEGDA microneedles with hydrophilic tips (PDA@Cu-SG/PEGDA). Furthermore, the physicochemical characteristics of the polymer microneedles, including morphology, composition, and mechanical strength, were thoroughly characterized. These microneedles with hydrophilic tips demonstrated sufficient mechanical strength. Owing to the ability of PDA@Cu to disrupt bacterial membranes, the microneedle patch demonstrated excellent in vitro antibacterial efficacy. We validated the antibacterial activity of the microneedle patch against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> by conducting in vitro bacterial plate coating assays. The results of the assays indicated that this minimally invasive strategy achieved broad-spectrum antibacterial effects; thus, this may be a suitable approach for managing polymicrobial skin infections during clinical trials.