Synthesis of magnetic N-doped carbon dots as pH-responsive targeted molecule cargo and its antioxidant and antibacterial behaviour

This study successfully generated magnetic N-doped carbon dots (CDs-MNPs) that exhibit two distinct functions: pH-responsive targeted drug delivery and powerful antioxidant action. The structural integrity, magnetic characteristics, and thermal stability of the samples were confirmed using comprehensive characterisation techniques, such as scanning electron microscopy, superconducting quantum interference device, Fourier Transform Infrared Spectroscopy, X-ray diffraction, continuous-wave electron para-magnetic resonance, X-ray photoelectron spectroscopy, surface porosity and thermogravimetric analysis. The CDs-MNPs displayed pH-dependent drug release profiles that conformed to zero-order, Higuchi, and Peppas models, demonstrating their ability to provide regulated release. The antioxidant activity of the carbon dots was assessed using the DPPH assay, where the radical scavenging capacity exceeded 80 %. This high level of activity was attributed to the synergistic effects of nitrogen doping and the functional groups present on the carbon dots. The biocompatibility of the specimen (up to 100 mg mL^-1), which is essential for biomedical applications, was confirmed by MTT assays. This study highlights the potential of CDs-MNPs as an effective option for therapeutic interventions, providing customised drug delivery and antioxidant advantages. The antibacterial activity of CDs-MNPs was evaluated against Gram-negative <i>Escherichia coli</i> and Gram-positive <i>Staphylococcus aureus</i> bacterial strains, demonstrating significant efficacy. These results highlight the potential of CD-based nanobactericides for applications in biomedical and food monitoring.