A Critical Review of Waste Biomass-Derived Carbon Dots for Drug Delivery: Synthesis, Properties, Applications, and Future Prospects

Abstract

Carbon dots (CDs) made from waste materials and renewable biomass are gaining popularity due to the growing need for sustainable and multipurpose medicine delivery systems. A promising strategy that addresses waste valorization and the creation of functional nanomaterials for therapeutic administration at the same time is waste-biomass-derived carbon dots (WBCDs). The synthesis, physicochemical characteristics, drug-delivery uses, biocompatibility, and translational potential of WBCDs are all rigorously examined in this review. The chemical composition of various waste biomass precursors— such as food wastes, plant-derived materials, agricultural residues, and chitin-rich wastes—and how it affects CD size, morphology, surface functionality, heteroatom incorporation, optical characteristics, and biological performance are examined. The main synthesis techniques—hydrothermal, microwave-assisted, microwave-hydrothermal, pyrolytic, ultrasonic, chemical oxidation, electrochemical, and conventional thermal approaches—are compared with a focus on how they affect characteristics important to drug delivery. Drug-loading processes, pH-responsive and controlled release, cellular uptake, targeted delivery, tracking using fluorescence, and theranostic uses are all given special consideration. The potential of WBCDs for delivering antibiotics, anticancer medications, anti-inflammatory medicines, and bioactive compounds is demonstrated by representative systems based on wheat bran, bamboo leaves, crab shells, sugarcane bagasse, sago bark, carrot roots, sea-buckthorn leaves, and other biomass sources. The review also emphasizes how precursor composition, surface chemistry, particle properties, purification, dose, and exposure conditions all have a significant impact on claimed biological safety. Biomass heterogeneity, batch-to-batch variability, purification, repeatability, limited control over drug loading and release, long-term toxicity, biodistribution, scalability, and regulatory translation are among the outstanding issues despite encouraging laboratory and preclinical results. Standardized synthesis, sophisticated characterisation, logical surface engineering, stimuli-responsive and target-specific administration, thorough toxicological evaluation, scalable processing, and life-cycle assessment should thus be the main areas of future development. All things considered, WBCDs are an emerging platform that combines multifunctional medication delivery technologies with the concepts of the circular economy.