Build an implanted "arsenal": detachable microneedles for NIR-triggered cancer photothermo-chemotherapy.

The current trend in tumor research is shifting from monotherapy to multimodal therapy. However, how to achieve on-demand drug delivery and minimize the invasiveness of treatment are still big challenges. Herein, we present a detachable microneedles (MNs) system, which consists of polycaprolactone (PCL) needles and polyvinylpyrrolidone/poly (vinyl alcohol) substrate, to build an implanted drug depot for on-demand photothermo-chemotherapy. Owing to the dissolvability of the substrate, detachable MNs can intradermally implant PCL needles loaded with photothermal conversion agent Prussian blue nanocubes (PB NCs) and chemotherapeutics doxorubicin hydrochloride (Dox·HCl). Once near-infrared light irradiates, PB NCs could translate light to local regional hyperthermia, which not only ablates cancer cells but also meltPCL to accelerate the diffusion of Dox·HCl. These MNs displayed a stable and repeatable photothermal effect under NIR irradiation. The ex vivo experiments using isolated swine skin demonstrated the as needed Dox·HCl delivery triggered by NIR light. Moreover, the robust antitumor efficacy of the MN system was proved in KB tumor-bearing nude mice under three timed NIR irradiation. Therefore, the developed detachable MNs which could build implanted "arsenal" for on-demand photothermo-chemotherapy have a bright future in tumor suppression.