Development of metal-free, recyclable enzyme mimics is challenging and requires key chemical modifications at the molecular level. Here, nitrilotriacetic acid-functionalized carbon nanospheres (LC-CNS@NTA) were prepared from the nitrogenrich weed Lantana camara (LC) using a simple hydrothermal reaction condition. Transmission electron microscopy (TEM) studies revealed size of ∼160 ± 20 nm for LC-CNS@NTA whereas, the same showed fluorescence emission at ∼520 nm with a ∼63% quantum yield. Furthermore, LC-CNS@NTA showed strong peroxidase (Pxrd) activity toward a wide range of substrate viz., H 2 O 2 , 3,3′,5,5′-tetramethylbenzidine, and o-phenylenediamine with K m and V max values of ∼257 μM and 1.06 μM/s, 282 μM and 1.47 μM/ s, and 270.8 μM and 1.647 μM/s, respectively. Interestingly, this also showed catalase (CAT) activity against H 2 O 2 with K m and V max values of ∼0.374 μM and 1.87 μM/s, respectively. It was observed that LC-CNS@NTA could effectively reduce the oxidative stressinduced cytotoxicity of HEK293 cells via retention of mitochondrial membrane potential, prevention of lipid peroxidation and DNA damage. It was further found that LC-CNS@NTA-treated cells showed reduced level of intracellular protein carbonylation and protein aggregation. The finding of the present study is expected to pave the path for designing engineered metal-free carbon nanozyme with dual enzyme mimic activity.

The development of biocompatible, widely applicable fluorescent imaging probe, with emission beyond the cellular and tissue autofluorescence interference, is a challenging task. In this regard, a series of 28 different fluorescent carbon dots (CDs) were synthesized using carbohydrates as carbon and cysteine (Cys) and o-phenylenediamine (OPD) as nitrogen source. The screened CDs showed photostability with bright blue (∼505–520 nm) and red (∼588–596 nm) emission and high fluorescence quantum yield (QY = 72.5 ± 4.5%). FTIR and NMR studies suggested presence of carboxylate and ester group for Cys- and OPD-based CDs, respectively. HRTEM results showed particle size of ∼3.3–5.8 nm for all the developed CDs. The antibacterial studies suggested that the developed CDs showed preferential antibacterial activity against Escherichia coli, with IC50 value of ∼200 μg/mL. Cytotoxicity and confocal microscopy studies of HeLa cells reflected that these CDs showed both anticancer activity and imaging ability. Agarose gel electrophoresis, together with SOSG assay and thiol estimation studies, suggested oxidative stress induced DNA degradation to be the primary cause for cell death. These hemocompatible CDs can thus be used as simultaneous imaging probe and photo dynamic therapeutic agent for both antibacterial and anticancer activity.

No abstract