Lipid-wrapped Upconversion Nanoconstruct /Photosensitizer Complex for Near-Infrared Light-mediated Photodynamic Therapy.

Photodynamic therapy (PDT) is a non-invasive medical technology that has been applied in cancer treatment where it is accessible by direct or endoscope-assisted light irradiation. To lower phototoxicity and increase tissue penetration depth of light, great effort has been focused on developing new sensitizers that can utilize red or near-infrared (NIR) light for the past decades. Lanthanide-doped upconversion nanoparticles (UCNPs) have a unique property to transduce NIR excitation light to UV-Vis emission efficiently. This property allows some low-cost, low-toxicity, visible light commercially available sensitizers, which originally is not suitable for deep tissue PDT, to be activated by NIR light, and has been reported extensively in the past few year. However, some issues still remain in UCNP-assisted PDT platform such as colloidal stability, photosensitizer loading efficiency, and accessibility for targeting ligand installation, despite some advances in this direction. In this study, we designed a facile phospholipids-coated UCNP method to generate a high-colloidally stable nanoplatform that can effectively load a series of visible light sensitizers in the lipid layers. The loading stability and singlet oxygen generation efficiency of these sensitizers loaded lipid-coated UCNP platform were investigated. We also have demonstrated the enhanced cellular uptake efficiency and tumor cell selectivity of this lipid-coated UCNP platform by changing the lipid dopant. On the basis of the evidence of our results, the lipid-complexed UCNP nanoparticles could serve as an effective photosensitizers carrier for NIR light mediated PDT.