Nanozyme controlled photothermal heat generation on nanoceria decorated MoS2 nanoflowers for enhanced cytotoxicity in cancer chemo-photothermal therapy

In recent years, the fabrication of nanomaterials with built-in ability to mimick biological enzymes (nanozymes) is gaining popularity for biomedical applications, especially for cancer photothermal therapy, based on non-toxic and photo-thermal heat generating 2D materials. The use of 2D inter-layered MoS2 nanoflowers (NFs) is especially interesting as it results in nanozymes that are photostable and biocompatible for normal cells under physiological conditions. In this work, we have synthesized MoS2 nanoflowers (NFs) decorated with CeO2 nanoparticles (NPs) using two linker molecules of cysteine and polyethylenimine connected through carbodiimide chemistry. The electron microscopy investigations revealed the formation of flower shaped MoS2 of 400 & PLUSMN; 100 nm in size decorated with spherical shaped CeO2 NPs of 15 & PLUSMN;5 nm in size. The fabricated nanozymes were investigated by UV-visible (UV-vis), FTIR spectroscopy, Raman spectroscopy and dynamic light scattering. The NFs decorated with long-chain PEI molecules demonstrated higher photo-thermal heat generation when compared to nanozymes decorated with low molecular weight PEI. Notably, the photo-thermal heat generation, biocompatibility, anti-cancer activity of nanozymes are significantly influenced by molecular weight of PEI, concentration of nanozymes, time duration of near-infrared (NIR) light exposure, power density of NIR light and folic acid (FA) conjugation. The nanozymes conjugated with FA on their surface exhibited excellent anti-cancer activity against human colon cancer cells under NIR light exposure at 808 nm and 0.5 W/cm2. Hence, the nanozymes demonstrated here have huge potential as nanophoto-thermal agents in cancer photothermal therapy.