Transdermal delivery of near-infrared photothermal-responsive PDA@Ag through dissolvable carboxymethyl chitosan films coated on PEGDA microneedle arrays for potential antibacterial applications

Eradicating cutaneous infections induced by pathogenic microorganisms, such as bacteria, fungi, and viruses, <i>via</i> conventional topical drug delivery is challenging owing to limited epidermal penetration. To overcome this limitation, we fabricated a poly(ethylene glycol) diacrylate (PEGDA) microneedle array coated with a carboxymethyl chitosan (CMC) film embedded within situ-synthesized polydopamine-modified silver nanoparticles (PDA@Ag NPs) for enhanced antibacterial efficacy. This design utilizes microneedle (MN)-mediated skin perforation to enhance drug permeation, combined with rapid film dissolution for the efficient release of the payload. The experimental findings revealed that the PDA@Ag-CMC/PEGDA MNs possess favorable biocompatibility along with dual photothermal and photodynamic functionalities. Mild photothermal therapy (PTT) triggered by these MNs promotes the production of antibacterial reactive oxygen species (ROS), resulting in a high antibacterial rate of up to 98% against both <i>Escherichia coli</i> (<i>E. coli</i>) and <i>Staphylococcus aureus</i> (<i>S. aureus</i>) under NIR irradiation at a PDA@Ag concentration of 40 μg mL^-1. To assess transdermal delivery performance, lidocaine hydrochloride (LiH) (78 μg per MN array) was incorporated into the CMC film as a model drug. Physiological conditions confirmed accelerated LiH release from the PDA@Ag-LiH-CMC/PEGDA system upon aqueous exposure. This minimally invasive approach demonstrated promising broad-spectrum antibacterial activity, suggesting that the PDA@Ag-LiH-CMC/PEGDA platform could serve as a viable clinical solution for managing polymicrobial skin infections and alleviating wound pain.