Nanomaterials

Carbon quantum dots (CQDs) have attracted intense research interest due to their unique physicochemical properties and broad application potential. CQDs are a new class of ultrasmall fluorescent carbon nanoparticles (<10 nm) that exhibit bright photoluminescence, broad excitation spectra, high quantum yields (QYs), and excellent photostability. Structurally, they consist of graphitic sp²/sp³-hybridized carbon with amorphous or nanocrystalline cores. Unlike conventional semiconductor quantum dots (SQDs), which often contain toxic group II–VI, III–VI, or IV–VI elements, CQDs offer a safer and more environmentally friendly alternative for biomedical and cosmetic applications. This review summarizes recent advances in green-chemistry approaches for CQD synthesis, including top-down, bottom-up, waste-derived, and surface-functionalization methods. Particular attention is given to natural carbon sources, which provide low-cost, sustainable, and eco-friendly routes for scalable production. The optical, electronic, and toxicological properties of CQDs are discussed to clarify their performance and safety profiles. Special emphasis is placed on their emerging roles in wound healing and cosmetic formulations, which remain underexplored despite their promising potential. To our knowledge, this is the first comprehensive review focusing on the current progress, key challenges, and future perspectives of CQDs in beauty and personal care applications.

Chlorella vulgaris is a microalga with well-established nutritional, antioxidant, anti-inflammatory, and antibacterial potential. The current study aimed to explore the green synthesis of silver nanoparticles (AgNPs) using the ethanolic extract of C. vulgaris and to assess how nanoparticle formation affects the chemical composition, antimicrobial potential, antioxidant capacity, and spasmolytic activity of the extract, building on earlier evidence for its modulatory effects on gastrointestinal smooth muscle. Even though AgNPs from Chlorella have been obtained previously, to the best of our knowledge, their spasmolytic activity has not been evaluated. To assess their properties and stability, ATR-FTIR, TEM images, XRD, DLS, and zeta potential were used. The obtained AgNPs were mostly spherical (with a diameter between 10 and 50 nm) and showed good colloidal stability. The synthesis of AgNPs resulted in significant changes in lipid composition, pigment content, and fatty acid profiles, including a decrease in total chlorophylls and an increase in mono- and polyunsaturated fatty acids. The biosynthesized AgNPs showed moderate to strong antibacterial activity against a variety of Gram-positive and Gram-negative bacteria, yeasts, and fungi. The most pronounced inhibitory effect was observed against A. niger and P. chrysogenum. In ex vivo organ bath experiments, AgNPs modulated the contractile activity and the spasmolytic profile of isolated rat gastric smooth muscle compared with C. vulgaris extract. These results demonstrate that green-synthesized AgNPs present systems with altered smooth muscle activity and improved antibacterial qualities, underscoring their potential for use in functional foods, nutraceuticals, and gastrointestinal therapeutics.

Silver nanoparticles (AgNPs) are extensively employed for their antimicrobial and biomedical properties, yet concerns persist regarding their potential toxicity. While AgNPs can induce oxidative stress, membrane disruption, and DNA damage, in vivo data remain inconsistent. This study investigated whether batch-to-batch variability in nominally identical AgNPs of 10 nm size contributes to divergent in vivo toxicity outcomes. CD-1 (ICR) mice were intravenously injected with a single 10 mg/kg bw dose of spherical, citrate-coated 10 nm AgNPs from three different batches purchased from the same manufacturer. The mice were euthanized 24 h post-exposure for quantitative silver determination by inductively coupled plasma–mass spectrometry (ICP–MS) and histopathological evaluation of liver, spleen, lungs, kidneys, and brain. Autometallography and immunofluorescence were used to assess silver distribution and cellular localization in the hepatobiliary system. All the batches induced hepatobiliary toxicity, characterized by hepatocellular necrosis and gallbladder wall hemorrhage, of differing severity. The most toxic batches contained higher proportions of smaller AgNPs, suggesting that differences in size distribution influence toxicological outcomes. Silver agglomerates were localized within multiple cell types, indicating internalization and cell-specific cytotoxicity. These findings highlight that minor physicochemical variations affect in vivo results, underscoring the importance of nanoparticle characterization to improve reproducibility in nanotoxicological research.