Advances in the application of biosynthesized carbon dots as fluorescent probes for bioimaging

Carbon dots (CDs) are emerging as versatile fluorescent nanoprobes for bioimaging applications due to advantages like tunable emissions, excellent biocompatibility, facile surface functionalization, and ease of synthesis. This review summarizes recent advances in applying biosynthesized CDs for sensitive bioimaging. CDs derived from sustainable biomass sources through green techniques like hydrothermal and microwave synthesis demonstrate bright, excitation-tunable photoluminescence spanning visible to near-infrared spectra. Careful control of synthesis parameters and surface passivation strategies enhance quantum yields above 50% comparable to toxic semiconductor dots. Conjugation with polymers, peptides, and recognition elements like antibodies impart solubility and selectivity towards cancer cells and biomarkers. In vitro validation in standard lines shows targeted organelle imaging abilities. In vivo administration reveals renal clearance pharmacokinetics with preferential tumor accumulation via enhanced permeability effects. Average tumor growth inhibition around 50-80% was achieved in mouse xenografts using CDs-drug formulations through combined therapeutic effects of chemotherapy and photothermal ablation under imaging guidance. However, concerns regarding toxicity from chronic exposures, large-scale reproducible manufacturing, and multimodal imaging capabilities need redressal prior to further clinical translation.