Photodegradation of carbon dots cause cytotoxicity

Abstract

Carbon dots (CDs) are photoluminescent nanomaterials with wide-ranging applications. Despite their photoactivity, it remains unknown whether CDs degrade under illumination and whether such photodegradation poses any cytotoxic effects. Here, we show laboratory-synthesized CDs irradiated with light degrade into molecules that are toxic to both normal (HEK-293) and cancerous (HeLa and HepG2) human cells. Eight days of irradiation photolyzes 28.6-59.8% of the CDs to <3 kilo Dalton molecules, 1431 of which are detected by high-throughput, non-target high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Molecular network and community analysis further reveal 499 cytotoxicity-related molecules, 212 of which contain polyethylene glycol, glucose, or benzene-related structures. Photo-induced production of hydroxyl and alkyl radicals play important roles in CD degradation as affected by temperature, pH, light intensity and wavelength. Commercial CDs show similar photodegraded products and cytotoxicity profiles, demonstrating that photodegradation-induced cytotoxicity is likely common to CDs regardless of their chemical composition. Our results highlight the importance of light in cytocompatibility studies of CDs.

Antibacterial Properties of Citric Acid/β-Alanine Carbon Dots against Gram-Negative Bacteria

“…Even though light affects the antimicrobial properties of CDs synthesized from citric acid and beta-alanine, our results indicate that longer incubations in the dark are also able to prevent bacterial growth indicating that these CDs also carry antimicrobial properties that are not light-dependent. A recent report on cytotoxic side effects of photodegraded carbon dots on normal and cancerous human cells [ 28 ] indicates a demand for CDs that do not require photoactivation to gain antimicrobial properties. Hence, CDs synthesized from citric acid +beta-alanine can be an alternative for antimicrobial photo-independent carbon dots.…”

Carbon dots for virus detection and therapy

“…Although the prospects for the use of CDs in nanomedicine are broad, the potential risks arising from interactions between CDs and biological systems must also be considered [50,55,56]. We have already published several papers focusing on the biological use and cytotoxicity of different types of carbon dots [46,53,57].…”

Tryptophan-sorbitol based carbon quantum dots for theranostics against hepatocellular carcinoma

“…However, most of these studies focused on either fluorescent diagnosis or anticancer activity, few concentrated on the intrinsic theranostic applications [ 19 ]. Moreover, CQDs may irradiate with light degrade into molecules that are toxic to both normal and malignant cells [ 25 ]. Therefore, it is imperative to design synthetic CQDs for theranostics using natural carbon sources as precursors without organic solvents.…”