N-(2-hydroxyl)propyl-3-trimethyl ammonium chitosan-coated gold nanoparticle-based platform for photothermal/chemo-photodynamic therapy

The combination of photodynamic and photothermal therapy is an interesting strategy for cancer treatment. In this work, we synthesized gold nanoparticles (AuNPs) loaded with methylene blue (MB) and coated with trimethylammonium functionalized chitosan (HTCC). Initially, HTCC was synthesized and characterized by 1H NMR, FTIR and elemental analysis. The degree of substitution (DS) of HTCC of 69 % was obtained through 1H NMR. The formulated HTCC-MB-AuNPs presented strong absorption in the visible range (500–800 nm), a small size of 150 nm, and zeta potential of about + 26 mV. The incorporation of MB in gold nanoparticles coated with HTCC modified the photophysical and photochemical properties, such as a decrease in the intensity of fluorescence emission and a decrease in the reactivity of MB with photo-oxidation model reactions. In vitro testing in MDA-MB231 breast cancer cells showed that HTCC-MB-AuNPs exert significant cytotoxicity in the presence of photo stimulation (red laser, 660 nm, 100 mW cm−2), possibly by combining photothermal and photodynamic effects (PTT + PDT). In the dark, under the same conditions, MB showed less cytotoxicity to cancer cells, especially when encapsulated in HTCC-MB-AuNPs. These results reveal a novel application potential of HTCC-MB-AuNPs in phototherapies for the treatment of cancer.