Removable Photocatalysis Microneedle Reactor for Carbon Monoxide Delivery to Enhance Chemosensitization.

Carbon monoxide (CO) has emerged as a promising therapeutic agent, yet ensuring safe and precise CO delivery remains challenging. Here, we report a removable hydrogel-forming microneedle (MN) reactor for CO delivery via photocatalysis, with an emphasis on chemosensitization. Upon application, body fluids absorbed by the MNs dissolve the effervescent agents, leading to the generation of carbon dioxide (CO 2 ) and triggering the release of the chemotherapeutics cisplatin. Meanwhile, the photocatalysts (PCs) trapped within MNs convert CO 2 to CO under 660 nm light irradiation. These PCs can be removed by hydrogel-forming MNs, thereby mitigating potential biological risks associated with residual PCs. Both in vitro and in vivo experiments showed that MN-mediated CO delivery significantly improved tumor sensitivity to cisplatin by suppressing DNA repair, using an A375/CDDP melanoma model. This removable photocatalysis MN reactor offers safe and precise local delivery of CO, potentially creating new opportunities for CO or its combination therapies.