pH-Based Cancer Detection by Graphene Quantum Dots

Abstract

Many cancers are characterized by rapid cell growth and division. This growth causes the area to become densely packed, forming tumors and therefore limiting oxygen penetration, while simultaneously causing the cell to have elevated energy needs. These factors trigger the use of mechanisms which result in high H+ output, resulting in cancerous extracellular environments measurably more acidic than their healthy counterparts. This study was conducted to determine the suitability of various nanomaterial-based platforms for pH sensing as an additive to their previously shown suitability for drug/gene delivery and bioimaging. Several platforms were chosen, including Glucose-Derived Graphene Quantum Dots (GGQDs), Reduced Graphene Oxide-Derived Graphene Quantum Dots (RGQDs), L-Glutamic Acid-Derived Graphene Quantum Dots (LGGQDs), and Aluminum-Doped Reduced Graphene Oxide-Derived Graphene Quantum Dots (Al-RGQDs), which all have peaks in their emission spectra in both the visible and infrared range, ideal for in vitro and in vivo imaging respectively. Nine spectra were taken from each of these platforms in the visible and infrared ranges from pH 6.00 to 8.00, as would be expected in cancerous and healthy biological systems. These spectra were then analyzed for defining characteristics which would distinguish between the various pH levels. While the results from RGQDs are thus far inconclusive, the visible spectra of GGQDs and LGGQDs showed correlation between pH and intensity, and the relative peak intensity readings from the visible and infrared Al-RGQDs showed a promising inverse relationship that bears further investigation.