Glutathione (GSH) is an important antioxidant biomarker with pivotal roles in multiple biological processes. Herein, a novel dual-emission ratiometric fluorescence nanoprobe was developed for selective and sensitive GSH detection by exploiting competitive interactions with a silver-riboflavin (Ag-RF) complex. The nanoprobe consists simply of a mixed solution of Ag-RF complex displaying characteristic yellow emission at 525 nm and nitrogen-doped carbon dots exhibiting blue emission at 440 nm. Due to the strong affinity of GSH toward silver ions, the addition of GSH liberates riboflavin from the Ag-RF complex leading to quenching of adjacent nitrogen-doped carbon dots through fluorescence resonance energy transfer (FRET). By ratiometrically measuring the fluorescence intensities at 525 and 440 nm (F₅₂₅/F₄₄₀), GSH levels can be rapidly quantified without interference. This sensor gave excellent linearity (R² = 0.9986) over 0.05–70 μmol/L GSH with high sensitivity (limit of detection = 0.015 μmol/L). The sensor also provided accurate GSH analysis in spiked human serum samples (96–98.5 % recoveries), validating practical applicability. With advantages of simplicity, selectivity, and low sample volume requirements, this fluorescent nanoprobe holds great promise as a tool for real-time, in-field monitoring of GSH for basic research and clinical investigations.

This research work introduces a novel sensor that utilizes two fluorophores to enable simultaneous monitoring of gentamicin sulphate (GNT) and ketorolac tromethamine (KET). The innovative sensor is composed of carbon dots (CDs) derived from black grapes (BG) and eosin Y (EY) dye. The interaction between the studied drugs and EY/BG@CDs sensor components allows for their simultaneous detection where GNT quenches the fluorescence of EY at 535 nm without affecting the fluorescence of CDs, while KET quenches the fluorescence of BG@CDs at 385 nm without impacting EY fluorescence. The BG@CDs probe was successfully characterized using various techniques such as absorption spectrophotometry, spectrofluorimetry, TEM imaging, infrared spectroscopic analysis, and XRD analysis. The suggested methodology was observed to be highly sensitive for the simultaneous determination of GNT and KET in their spiked rabbit plasma samples, with wide linear ranges and low limit of detection (LOD) values. The studied drugs were extracted using a highly selective extraction method involving protein precipitation followed by mixed mode solid phase extraction using an Oasis WCX cartridge. The simultaneous determination of GNT and KET is essential due to the potential interactions between the studied drugs. Therefore, this analysis can be used to evaluate the necessity of dose monitoring and the potential adverse effects of co-administration of these drugs.

A novel selective and reliable ratiometric fluorescence probe has been successfully synthesized for precise, sensitive, and simple quantitation of methotrexate (MTX). Hydrothermal method was employed to fabricate nitrogen-doped carbon dots using Annona squamosa seeds (AS-CDs) as a starting material, and their characteristics were confirmed using transmission electron microscopy (TEM), UV-Vis spectroscopy, fluorescence spectroscopy, X-ray diffractometry (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The ratiometric fluorometric assay, which is based on measuring the ratio of emissions (F₃₅₅/F₄₃₀), has a wide detection range of 5–2000 ng /mL and a limit of detection (LOD, S/N = 3) of 1.5 ng /mL. The developed sensing method was successfully applied to the quantification of MTX in rabbit plasma samples and parenteral formulations, achieving satisfactory recoveries %. Magnetic molecularly imprinted solid-phase microextraction was used for selective extraction of MTX from plasma samples. The pharmacokinetic parameters were successfully determined in real rabbit plasma samples after intravenous administration of MTX. The as-designed probe does not only improve the sensitivity, but also enhances the precision and accuracy of the proposed method. Overall, this study presents a promising approach for the detection of MTX in genuine samples with acceptable degree of selectivity and sensitivity.

Molecularly imprinted polymers (MIPs) are a type of artificial polymer, which have complementary cavities that are designed to bind a specific target molecule with a high degree of selectivity. Due to their effectiveness and stability, MIPs have found their way into many applications in medicine, chemistry, analysis and sensing fields. One of the most important modern uses of MIPs is the recognition of biological molecules of medical significance, which are called “biomarkers”. The use of MIPs enables easy and rapid extraction and detection of these biomarkers from different biological matrices. There are multiple techniques that arose for synthesis of MIPs each with their own set of advantages and drawbacks. In this review, we discuss MIPs in detail including their different types, methods of synthesis, characterisation methods, common challenges, in addition to their applications in different fields with a focus on their use in the analysis of protein biomarkers.