Optical Microneedle-Enhanced Transdermal Light Scattering for In Situ Photothermal Therapy Targeting Basal-Layer...

Near-infrared (NIR) light-mediated photothermal and photodynamic therapies are promising for nonsurgical treatment of skin diseases. However, the skin's inherent light absorption, especially from melanin in the epidermis, attenuates NIR energy penetration, limiting photothermal efficacy and potentially causing off-target tissue damage. In this context, we developed subcutaneous light response-enhanced microneedles (SLE MNs) that allow basal layer-localized seeding of therapeutics and leverage physical channels to efficiently transmit light transdermally, facilitating in situ scattered light activation for enhanced photothermal and photodynamic therapy outcomes. Such ultraoptical SLE MNs facilitated NIR light penetration, achieving up to 80% of initial light power at 500 μm subcutaneously, representing an approximate 160% increase compared to the control groups. Additionally, we conceptualized a two-segmented MN structure integrating light-guiding channels with photoresponsive therapeutics to enable precise in situ basal-layer treatment, effectively mitigating local hyperenergy on the skin surface and energy attenuation within tissues. This optical SLE MN patch offers a transformative platform for transdermal light therapy with significant clinical potential.