Antiviral Properties of Carbon-Based Quantum Dots

Carbon quantum dots (CQDs) are small, carbon-based nanoparticles, valued for their excellent biocompatibility, chemical stability, and strong photoluminescence, with antibacterial, anticancer, and antiviral properties. CQDs can be easily synthesized via top-down (breaking down larger carbon structures, such as graphite) or bottom-up (formation from molecular precursors, such as citrate) methods. CQDs used in this study were synthesized via a bottom-up approach from citric acid.We performed cytotoxicity assays on these CQDs using (i) Sulforhodamine B (SRB) assay to examine effects on cell proliferation, and (ii) Annexin V flow cytometric analysis to examine the induction of apoptosis in primary mouse embryonic fibroblasts (pMEFs). Our results indicate a high biocompatibility of CQDs. Next, we investigated the antiviral properties of CQDs against murine cytomegalovirus (MCMV) using a plaque-forming unit (PFU) assay. Cells were pre-treated with CQDs (0.05 mg/mL and 0.005 mg/mL) for 24 hours and subsequently infected with MCMV. Viral plaques were counted under a microscope, and a significant decrease could be observed in CQD-treated samples in a dose-dependent manner. To better understand the antiviral effect, we isolated RNA from CQD-treated and untreated pMEFs. We performed RT-qPCR to quantify the expression of ISGs (e.g. Stat1, Stat2, Irf7, Prk etc.), Tnfa and Il-1b, which all are genes encoding proteins that are involved in the antiviral defence. All tested genes were upregulated in CQDs-treated samples in a dose-dependent manner. Our data indicate that CQDs produced from citric acid might be promising candidates for creating novel antiviral agents against CMV.