A Systematic Comparative Study of the Toxicity of Semiconductor and Graphitic Carbon-Based Quantum Dots Using In Vitro Cell Models

Comparison of Toxicity and Cellular Uptake of CdSe/ZnS and Carbon Quantum Dots for Molecular Tracking Using Saccharomyces cerevisiae as a Fungal Model

Plant resource sharing mediated by mycorrhizal fungi has been a subject of recent debate, largely owing to the limitations of previously used isotopic tracking methods. Although CdSe/ZnS quantum dots (QDs) have been successfully used for in situ tracking of essential nutrients in plant-fungal systems, the Cd-containing QDs, due to the intrinsic toxic nature of Cd, are not a viable system for larger-scale in situ studies. We synthesized amino acid-based carbon quantum dots (CQDs; average hydrodynamic size 6 ± 3 nm, zeta potential -19 ± 12 mV) and compared their toxicity and uptake with commercial CdSe/ZnS QDs that we conjugated with the amino acid cysteine (Cys) (average hydrodynamic size 308 ± 150 nm, zeta potential -65 ± 4 mV) using yeast Saccharomyces cerevisiae as a proxy for mycorrhizal fungi. We showed that the CQDs readily entered yeast cells and were non-toxic up to 100 mg/L. While the Cys-conjugated CdSe/ZnS QDs were also not toxic to yeast cells up to 100 mg/L, they were not taken up into the cells but remained on the cell surfaces. These findings suggest that CQDs may be a suitable tool for molecular tracking in fungi (incl. mychorrhizal fungi) due to their ability to enter fungal cells.

Biogenic Carbon Quantum Dots as a Neoteric Inducer in the Game of Directing Chondrogenesis

The journey into the field of stem cell biology has been an endeavor of paramount advancement in biomedicine, establishing new horizons in the avenue of materiobiology. The creative drive of the scientific community focuses on ameliorating the utilization of stem cells, which is currently untapped on a large scale. With similar motivation, we present a nascent strategy of maneuvering biogenic carbon quantum dots (CQDs) to eclipse the toxic hurdles of chemical synthesis of carbon allotropes to serve as a biocompatible trident in stem cell biology employing a three-prong action of stem cell differentiation, imaging, and migration. The derivation of CQDs from garlic peels as a biogenic precursor abets in realizing the optophysical features of CQDs to image mesenchymal stem cells without hampering the biological systems with cytotoxicity. We report the versatility of biogenic CQDs to generate reactive oxygen species (ROS) to robustly influence stem cell migration and concomitantly chondrocyte differentiation from human Wharton's jelly mesenchymal stem cells (hWJ-MSCs). This was orchestrated without the use of chondrogenic induction factors, which was confirmed from the expression of chondrogenic markers (Col II, Col X, ACAN). Even the collagen content of cells incubated with CQDs was quite comparable with that of chondrocyte-induced cells. Thus, we empirically propose garlic peel-derived CQDs as a tangible advancement in stem cell biology from a materiobiological frame of reference to hone significant development in this arena.

New Insights into the Cellular Toxicity of Carbon Quantum Dots to Escherichia coli

In this study, the cytotoxicity and toxic mechanism of carbon quantum dots (CQDs) to E. coli were evaluated in vitro. The synthetic CQDs were extremely small in size (~2.08 nm) and displayed strong fluorescence. The results demonstrated that CQDs showed good biocompatibility with E. coli within a short culture time. However, when the exposure time exceeded 24 h, the toxicity of CQDs became apparent, and the contents of reactive oxygen species, lactate dehydrogenase, and the crystal violet absorption rate increased significantly. To further explore the cytotoxic mechanism, approaches including confocal laser scanning microscopy, scanning electron microscopy, and biological transmission electron microscopy combined with zeta potential tests, osmotic pressure measurement, and comet assays were performed. On the one hand, the CQDs altered the surface charges of cells and induced lipid peroxidation by adhesion on the surface of E. coli, leading to an increase in the permeability of the cell wall. On the other hand, when the concentration of CQDs reached 200 µg/mL, the osmotic pressure of the extracellular environment was significantly reduced. These are the main factors that lead to cell edema and death. Finally, the comet assays confirmed that CQDs could induce DNA damage, which could inhibit the proliferation of E. coli.

Fluorescent nanoparticles as tools in ecology and physiology

Fluorescent nanoparticles (FNPs) have been widely used in chemistry and medicine for decades, but their employment in biology is relatively recent. Past reviews on FNPs have focused on chemical, physical or medical uses, making the extrapolation to biological applications difficult. In biology, FNPs have largely been used for biosensing and molecular tracking. However, concerns over toxicity in early types of FNPs, such as cadmium-containing quantum dots (QDs), may have prevented wide adoption. Recent developments, especially in non-Cd-containing FNPs, have alleviated toxicity problems, facilitating the use of FNPs for addressing ecological, physiological and molecule-level processes in biological research. Standardised protocols from synthesis to application and interdisciplinary approaches are critical for establishing FNPs in the biologists' tool kit. Here, we present an introduction to FNPs, summarise their use in biological applications, and discuss technical issues such as data reliability and biocompatibility. We assess whether biological research can benefit from FNPs and suggest ways in which FNPs can be applied to answer questions in biology. We conclude that FNPs have a great potential for studying various biological processes, especially tracking, sensing and imaging in physiology and ecology.