Carbon dots in drug delivery and therapeutic applications

Carbon dots (CDs) are recently introduced carbon nanomaterials showing diverse properties. They show unique fluorescent behavior, low production cost, ecofriendliness, electron mobility, potent antioxidant and antibacterial capabilities, good biocompatibility, and abundant functional groups providing opportunities in functionalization for desired properties such as targeted drug delivery, diagnostics, and therapeutics. In this review, we provide a general overview of their synthesis processes, including top-down and bottom-up approaches and their associated benefits and drawbacks. Together with their pros and cons, we also explore the structural and optical properties, photoluminescence mechanisms, free radicals scavenging behavior, toxicity and biological behavior, surface chemistry, and functionalization for drug delivery and therapeutic effects. Furthermore, significant advances in the applicability of CDs such as bioimaging, cellular labelings, cell tracking, biosensing, bioanalytical assays, and therapeutic behavior, like antibacterial properties, tissue engineering, drug delivery system, gene delivery, cancer therapy, photothermal therapy (PTT), photodynamic therapy (PDT), and combinatorial (theranostic) applications are also discussed.