Effective near-infrared photodynamic therapy assisted by upconversion nanoparticles conjugated with photosensitizers

Abstract

Qing Qing Dou,1 Choon Peng Teng,1 Enyi Ye,1 Xian Jun Loh1–3 1Institute of Materials Research and Engineering, A*STAR, Singapore; 2Department of Materials Science and Engineering, National University of Singapore, Singapore; 3Singapore Eye Research Institute, Singapore Abstract: A drug model photosensitizer–conjugated upconversion nanoparticles nanocomplex was explored for application in near-infrared photodynamic therapy. As near-infrared penetrates deeper into the tissue, the model is useful for the application of photodynamic therapy in deeper tissue. The nanocomplex that was synthesized had low polydispersity, and the upconversion nanoparticle was covalently conjugated with the photosensitizer. The robust bond could prevent the undesired premature release of photosensitizer and also enhance the singlet-oxygen generation. Singlet-oxygen generation rate from this nanocomplex was evaluated in solution. The photodynamic therapy effect was assessed with MCF-7 cells in two different methods, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and live/dead assay. The assay results showed that promising efficacy (>90%) can be achieved with a low concentration (50 µg mL-1) of this nanocomplex and mild dosage (7 mW cm-2) of near-infrared laser treatment. Keywords: nanocomplex, singlet-oxygen generation rate, MTT assay, live/dead assay