Photophysical insights and in vitro cytotoxicity of dyes-gold nanostars system towards MCF-7 and A-549 cancer cells

Abstract

In this paper, the interaction of phenothiazine (PHZ) dyes (Azure A (AZA) and thionine (TH)) with gold nanostars (Au NSs) were studied using absorption spectroscopy, steady state emission spectroscopy, high resolution transmission electron microscopy (HR-TEM), dynamic light scattering (DLS), Zetapotential measurements and Fourier transform infrared (FT-IR) spectroscopy. Absorption spectral studies of Au NSs in the presence of dyes resulted in a slight red shift on the surface plasmon resonance band (SPR) of Au NSs, suggesting the changes in the Au NSs surface owing to the adsorption of dyes. The phenomena of hypochromism and the appearance of coupled localized surface plasmon resonance (LSPR) bands in the absorption spectral studies of the AZA-Au NSs and TH–Au NSs systems suggested the vital role of electrostatic interactions between PHZ dyes and Au NSs. The formation of the ground state complex between dyes and Au NSs were evident from the outcome of the steady-state emission titration experiments of the dyes-Au NSs system. Further, the cytotoxic activity of AZA, TH, AZA-Au NSs and TH-Au NSs complexes on breast cancer (MCF-7) and A-549 cell lines were also investigated. These studies revealed that AZA-Au NSs, TH-Au NSs complexes showed the higher level of cytotoxicity than PHZ dyes treated cells.