AgInS2-Coated Upconversion Nanoparticle as a Photocatalyst for Near-Infrared Light-Activated Photodynamic Therapy of Cancer Cells

The development of high-performance near-infrared (NIR) photocatalysts with long-term stability and the elucidation on the working mechanism along with multifunctional activity toward biomedical applications have not been explored sufficiently. Herein, a novel hybrid material of an upconversion nanoparticle (NaYF4/Yb3+,Er3+) (UCN) coated with a ternary semiconductor (AgInS2, AIS) has been synthesized by a simple and robust two-step solvothermal route for NIR light active photocatalysis. Preparation of oleic acid-capped spherical UC nanoparticles (NPs) (similar to 25 nm) followed by solvothermal decomposition of two precursor complexes Ag(acda) and In(acda) 3 resulted in the formation of well-defined NaYF4/ Yb3+,Er3+@AgInS2 core-shell nanoparticles (UCN@AIS NPs) (similar to 90 nm). It has been found that effective energy transfer occurred from NaYF4/Yb3+,Er3+ to AgInS2 by a nonradiative luminescence resonance energy transfer process. Superior photocatalytic decomposition activity was validated in terms of the degradation of methylene blue dye under the exposure of 980 nm NIR laser light with the presence of a UCN@AIS NP catalyst. The degradation process was mediated primarily owing to the formation of a cytotoxic reactive oxygen species (ROS) by the hybrid material under NIR light irradiation, in which UCN performs as a transducer to sensitize AIS and trigger the ROS generation. In vitro cancer cell imaging potentiality of the UCN@ AIS NPs was then studied on cervical cancer cells (HeLa cells). The UCN@AIS NPs induced in vitro cervical cancer cell death (photodynamic therapy) with similar to 27% efficiency as measured by the MTT assay and thus proved to be a decent candidate for NIR active photocatalysts for biomedical applications.