Cancer‐Targeting Graphene Quantum Dots: Fluorescence Quantum Yields, Stability, and Cell Selectivity

Abstract

Folic acid, due to its high affinity towards folate receptors (FR), has been recognized as one of the most promising cancer targeting vectors. However, the inherent defects of low water solubility (1.6 μg•mL -1 ), high sensitivity towards photobleaching, low fluorescent quantum yields (QYs,<0.5%) seriously limit its practical application. Herein ultra-stable, highly-luminescent graphene quantum dots (GQDs) that selectively target diverse cancer cells are prepared and tested. The new GQDs present step changes compared to common folic acid through a ~6250 times increase in water solubility (to ~10 mg•mL -1 ), more than 150 times in QYs (up to ~77%), while maintaining luminescence stability up to 98% subjected to UV, visible light, and heating over 360 min. It is shown that the suppression of This article is protected by copyright. All rights reserved.3 non-radiative transitions by amino groups pyrolyzed from pterin play a key role in the mechanism of high QYs and excellent stability. The functional groups that are likely responsible for the selective targeting of cancer cells with different levels of folate receptor expression on the surface are identified. Collectively with these promising properties, the new functional graphene quantum dots may open a new avenue for cancer diagnosis, drug delivery and therapies.

Recent Advances on Graphene Quantum Dots for Bioimaging Applications

“…On the other hand, the strong electrostatic interaction between positively charged PNF and negatively charged cellular membrane greatly facilitated the efficient internalization, resulting in a five-fold higher cellular uptake of PNF-GQDs than GQDs alone. Subsequently, folic acid-conjugated GQDs (FA-GQDs) were also reported by Zhang et al for targeted FL imaging (Zhang et al, 2019a). The timedependent enhanced fluorescence of FA-GQDs was observed in SKOV3 cells (Figure 9C), which confirmed the selective internalization due to FA targeting, whereas the confocal fluorescence microscopy indicated the positive correlation between the internalization of FA-GQDs and the expression of cell surface FA receptor.…”

Synthesis of graphene quantum dots and their applications in drug delivery

“…In recent years, the applications of GQDs in drug delivery [123][124][125][126][127], sensors [128][129][130][131][132][133][134], bio-imaging [10,63,[135][136][137][138][139][140], magnetic hyperthermia [141][142][143], photothermal therapy [144][145][146][147][148], antibacterial [145,149,150], catalyst [69,[151][152][153][154][155], environmental protection [38,156,157], and energy [158][159][160][161][162][163] has made remarkable accomplishment. In order to better apply GQDs to drug delivery, some researchers had used density functional theory (DFT) calculations [164]…”

Recent advance of carbon dots in bio-related applications

“…Wang et al produced the excitation-dependent emission CDs from CS, which exhibit high uptaking of SAS cells [118]. FA and tris(hydroxymethyl)amino methane are heated to form FR targeting CDs (FR-CDs) with PL QY of 77% and super photo and thermal stability [119]. With the presence of free FA, PL intensity of FR-CDs inside the SKOV3 cells decreased over 85% indicating that the uptake of FR-CDs effectively depressed by free FA.…”