Automated Open-Loop in Vitro photothermal TherapyUsing Near-Infrared Emitting Graphene Quantum Dots

Abstract

Graphene-based materials have been the subject of interest for photothermal therapy due to their high light to heat conversion efficiency. Graphene quantum dots (GQDs) are expected to both possess advantageous photothermal properties and facilitate visible and near-infrared (NIR) fluorescence image-tracking, while surpassing the other graphene-based materials in their biocompatibility. To test these capabilities several different GQD structures were synthesized using top-down (RGQDs from reduced graphene oxide) and bottom-up (HGQDs from molecular hyaluronic acid) approaches. RGQDs and HGQDs possess nanometer-scale sizes, are hydrophilic, and exhibit fluorescence throughout the visible and NIR. The high biocompatibility of RGQDs (1.5 mg/ml) and HGQDs (1.7 mg/ml) and substantial absorption tail in the NIR make them suitable for biological photothermal therapy applications. In aqueous suspensions of RGQDs and HGQDs, a low power (0.8 W/cm2) 808 nm NIR laser irradiation facilitates heating up to 46.0 and 47.0 °C, respectively, making them sufficient for cancer tumor ablation. In vitro photothermal studies were performed via cost-effective open-loop automated approach involving a 3D printer head controlling the laser and a thermocouple. These experiments are carried out in a 96 well plate to show that GQDs can facilitate HeLa cancer cells heating up to 54.5 and 43.5 °C from 37.0 °C, leading to the inhibition of cell viability down to 23%. GQDs’ fluorescence in the visible and NIR effectively tracks their intracellular accumulation verifying effects of photothermal treatment. The combination of therapeutic and imaging capabilities makes GQDs developed in this work highly prospective anticancer agents.