Spent Coffee Ground-Derived Carbon Dots as Redox-Modulating Biomaterials for Astrocytic Differentiation of Human Neural Progenitor Cells

Food waste-derived carbon dots (CDs) from spent coffee grounds or spinach were synthesized via hydrothermal and solvothermal methods and systematically characterized for their photoluminescence and surface chemical properties. Biological evaluations using human neural progenitor cells (hNPCs) demonstrated efficient cellular uptake and high biocompatibility across all synthesized CDs. Notably, coffee-derived blue-emitting CDs (B-CDs) exhibited robust concentration-dependent antioxidant activity and reduced intracellular reactive oxygen species (ROS) levels. In addition, B-CDs were associated with enhanced astrocytic differentiation of hNPCs. To further evaluate the antioxidative effects of B-CDs under oxidative stress conditions, cells were exposed to H2O2-induced oxidative stress during differentiation. B-CDs alleviated oxidative stress-associated cellular damage and reduced the expression of inflammation-related markers. This antioxidative effect was accompanied by the downregulation of C3, a marker of neurotoxic reactive astrocytes. Further, B-CDs promoted early phosphorylation of STAT3 (Tyr705), a key driver of astrocytic differentiation, and induced sustained expression of a cytoprotective enzyme HO-1, linking intracellular ROS reduction to astrocyte-biased differentiation. This work demonstrates that food waste-derived CDs can function as bioactive nanomaterials capable of modulating neural progenitor cell differentiation and mitigating cellular stress. These findings highlight their potential for applications in neural interface materials, regenerative medicine, and redox-responsive biomaterial systems.