Microwave assisted synthesis of N-doped carbon quantum dots for doxorubicin delivery

Carbon quantum dots (CQDs) have emerged as a versatile nanoplatform for biomedical application owing to their tunable physicochemical properties. In this context, microwave strategy was applied for the first time to synthesize N-CQDs under uniform dielectric heating of 360 W, using readily available organic molecules, namely meta-toluidine, meta-aminophenol and meta-aminobenzoic acid. The novelty of the work was to study the effect of variation of single functional-group at the meta-positions on the surface polarity and charge density for the production of N-CQDs. Out of three precursors, the meta-aminobenzoic acid-derived CQDs manifested the highest degree of aqueous dispersibility with average particle size of around 4–6 nm, and were thus selected for further study. The as synthesized CQDs from meta-aminobenzoic acid was conjugated to doxorubicin at different drug concentrations and MTT assay was carried out using HeLa cells to assess the effectiveness of the CQD-doxorubicin conjugate and free drug. MTT assay revealed 74.47 ± 2.45% and 65.73 ± 4.61% cytotoxicity of the CQD-doxorubicin conjugate and the free drug, respectively against HeLa cells at the highest drug concentration of 12 µg/ml, presumably owing to facilitated endocytic uptake of the conjugate over the free drug by the HeLa cells.