Filling core–shell microneedles with pressurized oxygen-embedded particles (POPs) to improve photodynamic therapy

Photodynamic therapy (PDT) represents a spatiotemporal and minimally invasive treatment for superficial diseases. Enhancing the delivery efficiency of photosensitizers and elevating oxygen levels at the lesion site are two established strategies for improving its effectiveness. Here, we introduce a strategy involving the release of pressurized oxygen to drive photosensitizer diffusion, which is incorporated into a core-shell microneedle (MN) system to improve PDT. This MN system comprises a polyvinylpyrrolidone shell and methylene blue (MB) photosensitizer loaded core particles containing pressurized oxygen bubbles. Upon insertion, the aqueous tissue environment triggers the dissolution of particles within the MNs, enabling the rapid release of oxygen, thereby promoting the diffusion of MB. <i>In vitro</i> experiments demonstrate that these particles could effectively accelerate the release and diffusion of MB. The released oxygen could relieve hypoxia and increase the generation of reactive oxygen species (ROS) of PDT. In a mouse melanoma model, the MN system enhances tumor growth inhibition induced by PDT and mitigates tumor metastasis. This innovative system offers an autonomous, safe, and convenient approach for localized gas delivery and drug diffusion, potentially creating new avenues for efficiently combining gas and other therapies for superficial diseases.