Sustainable carbon quantum dots synthesized from yeast β-glucan as a promising nanomaterial for biological applications

Carbon quantum dots (CQDs) have emerged as eco-friendly nanomaterials with tunable optical properties and biomedical potential. This study aimed to synthesize and characterize phosphorus-doped CQDs from Saccharomyces cerevisiae β-glucan, providing a green, reproducible production route and assessing their physicochemical and biological properties. β-Glucan extracted from yeast cell wall (YCW) was hydrothermally carbonized at 250 °C to yield fluorescent CQDs. Structural, optical, and compositional analyses were conducted using FTIR, XRD, EDX-MAP, TEM, and DLS. The antibacterial, antioxidant, anti-inflammatory, and cytotoxic properties were systematically evaluated using standard in vitro assays. The synthesized CQDs exhibited strong π-π* absorption at 201 nm and pH-sensitive blue photoluminescence with a 24% quantum yield, and TEM confirmed core sizes below 10 nm. The CQDs displayed broad-spectrum antibacterial activity, exceeding ciprofloxacin against resistant Pseudomonas aeruginosa, with MIC and MBC values ranging from 0.93 to 3.75 mg mL⁻¹. They also showed high antioxidant activity under acidic conditions and reduced erythrocyte sedimentation rate from 12 mm h⁻¹ to 1 mm h⁻¹, indicating anti-inflammatory potential. Cell viability remained above 70% at ~ 47 µg mL⁻¹, confirming acceptable biocompatibility. β-Glucan-derived CQDs offer sustainable synthesis, strong optical properties, and multifunctional bioactivity, creating an eco-friendly nanomaterial for antimicrobial, antioxidant, and inflammation-responsive uses.