Two major challenges of current
photodynamic therapy (
PDT) are the limited tissue penetration of excitation light and poor
tumor-selectivity of the
photosensitizer (PS). To address these issues, we developed a multifunctional nanoconstruct consisting of upconversion nanoparticles (UCNPs) that transform near-infrared (NIR) light to visible light and a
photosensitizer zinc(II) phthalocyanine (ZnPc).
Folate-modified amphiphilic
chitosan (FASOC) was coated on the surface of UCNPs to anchor the ZnPc close to the UCNPs, thereby facilitating resonance energy transfer from UCNPs to ZnPc. Confocal microscopy and NIR small animal imaging demonstrated the enhanced
tumor-selectivity of the nanoconstructs to
cancer cells that overexpressed
folate receptor.
Reactive oxygen species (ROS) generation in
cancer cells under a 1-cm tissue was higher upon excitation of UCNPs with the 980 nm light than that with 660 nm irradiation. In vivo
PDT treatments for deep-seated
tumors demonstrated that NIR light-triggered
PDT based on the nanoconstructs possessed remarkable therapeutic efficacy with
tumor inhibition ratio up to 50% compared with conventional visible light-activated
PDT with a noticeable reduced
tumor inhibition ratio of 18%. These results indicate that the multifunctional nanoconstruct is a promising
PDT agent for deep-seated
tumor treatment and demonstrate a new paradigm for enhancing
PDT efficacy.