Leveraging Spectral Matching between Photosensitizers and Upconversion Nanoparticles for 808 nm-Activated Photodynamic Therapy

Abstract

Upconversion nanoparticles (UCNPs) are promising platforms to enhance the therapeutic response of cancer cells toward photodynamic therapy (PDT). When coupled with UCNPs, the photosensitizers in PDT are indirectly activated by near-infrared (NIR) excitation that allows for deeper tissue penetration and reduced attenuation. To achieve maximum performance, the upconverted emission peak of the UCNPs and absorption band of the photosensitizers need to overlap significantly. However, the spectral mismatch between the upconverted emission maximum of UCNPs (predominantly in the green) and absorption maximum of most available photosensitizers (in the red) greatly limits the therapeutic efficacy of current UCNP-PDT platforms. Here we report a UCNP-PDT platform that under biobenign 808 nm NIR excitation shows a strong spectral overlap between the UCNP emission (λem) and absorption of zinc phthalocyanine photosensitizers (λabs). The spectrally matched UCNP red emission band is 40 times stronger than the green emissi...