Exploring the photothermal hot spots of graphene in the first and second biological window to inactivate cancer cells and pathogens

Abstract

Cancer, being a potentially fatal disease, causes millions of deaths worldwide and poses a threat to relatively all beings, while disease and infections arising from pathogens are equally life threatening. Therefore, it is primarily necessary to design materials that can conquer over both cancer cells as well as pathogens. Advancements in the realm of nanomaterial-based theranostics for photodynamic (PDT) and photothermal (PTT) therapies have been groundbreaking. However, a greater focus on graphene-based nanomaterials such as photothermal theranostics under the first and second near-infrared (NIR) window is imminent. Keeping that in mind, we have developed a new and simple biocompatible nanocomposite material composed of reduced graphene oxide (RGO) and polyacrylic acid (PAA) to achieve RGO functionalized PAA (RGOPAA). The focus of this study is to compare PTT capability and inactivation of cancer cells and pathogens by RGOPAA under two different NIR windows (808 and 1064 nm). The photothermal heating curves of RGOPAA showed similar temperature profiles at 808 and 1064 nm wavelengths. Confocal laser scanning microscopy images showed successful internalization of RGOPAA into HeLa cells while the MTT assay and heat shock protein expression studies revealed that the cytotoxicity of HeLa cells was mainly attributed to heat generation of graphene upon photoirradiation. In addition, photothermal studies were also performed in the pathogenic bacteria, S. aureus, which revealed excellent killing efficiencies. Our findings conclude that both NIR I and II produce similar effects in terms of cancer cell and pathogen inactivation, although NIR II can be a much better choice for in vivo imaging studies owing to its deeper penetration and higher transparency.