Milk-Derived Carbon Quantum Dots: Study of Biological and Chemical Properties Provides Evidence of Toxicity

Abstract

Carbon dots (CDs) are carbon-based zero-dimensional nanomaterials that can be prepared from a number of organic precursors. In this research, they are prepared using fat-free UHT cow milk through the hydrothermal method. FTIR analysis shows C=O and C-H bond presence, as well as nitrogen-based bond like C-N, C=N and –NH2 presence in CDs, while the absorption spectra show the absorption band at 280 ± 3 nm. Next, the Biuret test was performed, with the results showing no presence of unreacted proteins in CDs. It can be said that all proteins are converted in CDs. Photo luminance spectra shows the emission of CDs is 420 nm and a toxicity study of CDs was performed. The Presto Blue method was used to test the toxicity of CDs for murine hippocampal cells. CDs at a concentration of 4 mg/mL were hazardous independent of synthesis time, while the toxicity was higher for lower synthesis times of 1 and 2 h. When the concentration is reduced in 1 and 2 h synthesized CDs, the cytotoxic effect also decreases significantly, ensuring a survival rate of 60–80%. However, when the synthesis time of CDs is increased, the cytotoxic effect decreases to a lesser extent. The CDs with the highest synthesis time of 8 h do not show a cytotoxic effect above 60%. The cytotoxicity study shows that CDs may have a concentration and time–dependent cytotoxic effect, reducing the number of viable cells by 40%.

Carbon Dots: Opportunities and Challenges in Cancer Therapy

“…Biowaste resources have also been widely used as low-cost, renewable resources with advantages in biodegradability, biocompatibility, and availability [ 109 ]. The increasing interest in using natural resources in CD synthesis using hydrothermal carbonization approaches in recent years requires a minimal experimental setup [ 110 , 111 , 112 ]. Additionally, there is relatively little information on the regulatory status of QDs and CDs in the literature.…”

Development of Carbon Dots Synthesized from Green Tea and Alpha‐hydroxyl Acids with Enhanced Antioxidant Activity, Photostability and UV Protection Properties

“…This leads to a strong absorption in UVC absorption for G‐CDs. Thus, G‐CDs are structurally optimized for enhanced UVC shielding [58,59] . These results therefore assure us that our CDs have the potential for use in cosmetics.…”

An overview on animal/human biomass-derived carbon dots for optical sensing and bioimaging applications

“…172 Besides, severe in vitro cytotoxicity was observed for cow milk-derived CDs on mouse hippocampus cells (HT22, cell viability <60%) even at the lowest concentration of 0.4 mg mL −1 . 197 The toxicity study of hamburger-, lamb-, chicken-, and chicken breast-derived doped CDs exhibited the more cytotoxic effect of CDs obtained at a higher temperature in comparison to that synthesized at a relatively lower temperature (Table S2 †) due to their surface functional groups and large amount of carbon core via effective carbonization. 149,153,158,159 Interestingly, the lamb-derived N,S-CDs obtained at a longer baking time (CD-3: 45 min and cell viability: 45.0%) had much higher cytotoxicity than that from the shorter baking times (CD-1: 15 min, cell viability: 95.0% and CD-2: 30 min, cell viability: 74.0%), which is again related to the degree of carbonization and surface passivation.…”

“…A large negative zeta potential value suggests strong electrostatic repulsion among the negatively charged functional groups and better stability of animal/human biomass-derived CDs in aqueous solution. 128,129,131,132,[140][141][142]144,185,189,191,197,203,207,208,215 Besides a negative zeta potential, animal/human-derived CDs with positive zeta potentials have also been reported. 137,198,230,236,243 The functional groups and elemental compositions of animal/human biomass-derived CDs are oen analyzed by Fourier transform infrared (FTIR) spectroscopy and XPS.…”