Sustainable upcycling of watermelon peels into a nanosensor for the selective detection of mefenamic acid, a nonsteroidal anti-inflammatory drug with antioxidant properties, in biofluids and pharmaceutical formulations

Abstract

Mefenamic acid has recently been identified to possess antioxidant properties, expanding its potential applications beyond traditional pain relief. Emerging studies suggest its possible role in the prevention or management of Alzheimer’s disease through its anti-inflammatory and oxidative stress-reducing effects. This study represents an innovative, highly green eco-friendly method for determination of mefenamic acid in plasma, urine and in its pharmaceutical forms. It involves the transformation of waste watermelon peels into a highly fluorescent switch off nanosensor. For the first time, carbon quantum dots were synthesized from watermelon peel in one step via in situ microwave-assisted carbonization process, completed within 17.0 min without the addition of any external chemicals. The synthesized carbon quantum dots were found to have good fluorescence (λex/em 330.0/420.0 nm), high water solubility and good stability. The synthesized carbon dots were characterized using fluorescence spectroscopy, UV–Visible Spectroscopy, X-ray photoelectron spectroscopy, Zeta potential analysis; Transmission electron microscopy and Fourier transform infrared. The formed Carbon dots appeared to have average particle size of 3.69 - 6.19 nm and their shape was spherical. Mefenamic acid, a nonsteroidal anti-inflammatory anthranilic acid derivative with antioxidant properties, was determined using the synthesized carbon quantum dots by inner filter effect (IFE) and static fluorescence quenching mechanism. The quenching effect on the produced carbon quantum dots was utilized for determination of mefenamic acid over the range of (0.50 – 20.0 µg/mL). The % recovery of the developed method was found to be 100.03 ± 0.776 in pure form, 99.973 ± 0.713 in capsule, 99.70 ± 3.740 in plasma and 99.968 ± 4.005 in urine. Determination of mefenamic acid in the presence of different species indicated high selectivity of the suggested method. The validity of the proposed method was assessed according to the ICH recommendations. Different greenness assessment tools were used for evaluation of the proposed method sustainability. By using watermelon peel, typically regarded as waste, this method offers a green and sustainable route for synthesizing carbon quantum dots from natural sources. Also, using water as solvent without using any other organic solvents; it gives a great advantage to our work as it does not produce any chemical or harmful waste, which makes it safe for the analyst and earth.