Protocol for the Synthesis of Green Fluorescence Carbon Quantum Dots and Biological Application

Carbon quantum dots (CQDs) are materials that are made up of particles that are only a few n anometers wide. They have no dimensions and can change their fluorescence qualities. They are also verybiocompatible and have a lot of potential to change the chemistry of their surface. Their eco-friendly synthesis from precursors, like citric acid (CA) and ascorbic acid (AA), provides a sustainable approach to highly fluorescent nanomaterials with promising applications in bioimaging, drug delivery, and other biomedical fields. Green-emitting carbon quantum dots (GCQDs) were synthesized via a simple reflux approach using citric acid and ascorbic acid as biomolecular precursors in a solvent solution of ethanol-water (1:2). The obtained GCQDs solution was purified using a dialysis process. Besides this, pH maintenance, lyophilization, and further submission for detailed physicochemical evaluation and characterization are done. The spectroscopic analysis, including UV–visible spectroscopy, fluorescence spectroscopy, and FTIR, confirmed the presence of surface functional groups and strong fluorescence properties and quantum yield calculations of the synthesized GCQDs. Microscopic and structural analyses using XRD, AFM, and TEM revealed the nanoscale, predominantly spherical morphology of the synthesized GCQDs. In addition, in vitro biological evaluations such as MTT assay and cellular uptake analysis were undertaken to evaluate cytocompatibility and intracellular distribution. We study the endocytosis pathway of these GCQDs, with size variations ranging from 3 to 5 nm, in mouse tissue-derived primary cells, tissues, and zebrafish embryos. GCQDs were internalized into mouse kidney and liver primary cells through a clathrin-mediated pathway. The findings confirmed that the produced GCQDs exhibit good water solubility, favorable biocompatibility, and significant potential as candidates for biomedical imaging applications.