This study focuses on the determination of the active metabolite of molnupiravir (MOL), N-hydroxycytidine (NHC), using a square wave voltammetric (SWV) method. Carboxylesterase-2 enzymes catalyze the conversion of MOL prodrug into NHC. However, co-administration of verapamil (VER), a carboxylesterase-2 inhibitor, may reduce the levels of NHC, leading to decreasing its antiviral activity. In this context, the levels of NHC and VER were simultaneously monitored using a carbon paste electrode modified with phase I of copper tetracyanoquinodimethane (CuTCNQ) which is highly conductive charge transfer complex. The as-designed sensor was characterized successfully using various spectroscopic techniques and Scanning Electron Microscopy (SEM). The electrochemical behavior of the newly fabricated probe was examined using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). This method demonstrated its efficacy in measuring NHC and VER levels in rabbit plasma samples, showing high sensitivity and selectivity. The calibration plots for the simultaneous quantitation of NHC and VER displayed excellent linearity over the concentration ranges of 50–1600 nmol/L for NHC and 10–250 nmol/L for VER. The limits of detection (LOD) and quantitation (LOQ) in rabbit plasma were found to be 15.2 and 50.8 nmol/L for NHC and 2.9 and 9.9 nmol/L for VER, respectively. Moreover, fundamental pharmacokinetic parameters were calculated for NHC before and after co-administration of VER. The results suggest that the SWV method using CuTCNQ-modified CPE can be a useful tool for the determination of NHC and VER levels in plasma samples, with potential applications in the monitoring of drug-drug interactions involving carboxylesterase-2 inhibitors.

This study focuses on the interaction between the antihyperlipidemic drug fluvastatin (FLV) and the antidiabetic drug empagliflozin (EMP), which are commonly co-administered medications. EMP's impact on FLV levels is attributed to its inhibition of organic anion transporting polypeptide 1B1 (OATP1B1), responsible for FLV liver uptake, consequently elevating FLV concentrations in blood. Traditional extraction methods for FLV faced difficulties due to its high hydrophobicity. In this study, a hydrophobic natural deep eutectic solvent (NDES) using air assisted dispersive liquid–liquid microextraction (AA-DLLME) was utilized as an excellent choice for achieving the highest extraction recovery, reaching 96% for FLV and 92% for EMP. The NDES was created through the combination of menthol and hippuric acid in a 4:1 ratio, making it a green and cost-effective pathway. Liquid phase microextraction followed by spectrofluorometric measurements of FLV at λ_em = 395 nm and EMP at λ_em = 303 nm, with excitation at a single wavelength of 275 nm was carried out. Response surface methodology (RSM) relying on central composite design (CCD) was used to optimize the variables affecting the AA-NDES-DLLME. The optimized conditions for extraction are: NDES volume of 200 μL, centrifugation time of 15 minutes, air-agitation cycle of 6 cycles, and sample pH of 4.0. Under these optimized conditions, the developed method exhibited good linearity and precision. The method showed good recoveries from rabbit plasma samples spiked at varying concentrations of the analyzed compounds. To assess the applicability and effectiveness of the hydrophobic DES, the validated method was applied to extract the studied drugs from rabbit plasma samples after oral administration of FLV alone and in combination with EMP. The pharmacokinetic parameters of FLV were calculated in both cases to investigate any changes and determine the need for dose adjustment.

This work presents a simple yet selective fluorometric protocol for the quantification of vancomycin, an important antibiotic for treating infections caused by Gram-positive bacteria. A novel ratiometric fluorometric method for the determination of vancomycin is developed based on dual emissive carbon dots (DECDs) with emission at 382 nm and 570 nm in combination with Co²⁺ ions. Upon addition of Co²⁺ions, the fluorescence at 382 nm of DECDs is enhanced while emission at 570 nm remains constant. In the presence of vancomycin, it complexes with Co²⁺ leading to quenching of the 382 nm fluorescence due to strong binding with Co²⁺ in the Co@DECDs system. The DECDs are fully characterized by TEM and different spectroscopic techniques. The proposed ratiometric method is based on measuring fluorescence ratio (F₅₇₀/F₃₈₂) against vancomycin concentration and the method exhibits a good linearity range from 0.0 to 120.0 ng mL⁻¹ with a low limit of detection (S/N = 3) of 0.31 ng mL⁻¹. The method shows good selectivity with minimal interference from potential interfering species. This ratiometric fluorometric approach provides a promising tool for sensitive and specific vancomycin detection in clinical applications.

This work pioneers a selective fluorometric assay for the fibrinolytic agent streptokinase by strategically coupling its thrombolytic action to fluorescence signaling using carbon dots integrated into fibrin clot network. Streptokinase triggers clot lysis and caused release of photoluminescent carbon dots integrated within the fibrin network in a concentration-dependent manner. Transmission electron microscope (TEM) imaging verifies distinct aggregation of the carbon dots upon addition to fibrin. The carbon dots are derived via an eco-friendly hydrothermal approach using cucumber peel as the source of carbon. Structural and optical characterization of the carbon dots were performed using different techniques including X-ray diffraction, TEM, Fourier-transform infrared spectroscopy, and ultraviolet–visible absorption and fluorescence spectroscopies. All experimental parameters influencing the formation of the fibrin clot and factors governing the release of carbon dots upon the addition of streptokinase have been fully optimized. This fluorescence assay offers high selectivity for streptokinase over potential interferences in addition to excellent sensitivity with a 0.017 μg/mL limit of detection and a wide linear range (0.05–500 μg/mL). Successful application to pharmaceutical formulations is demonstrated with excellent recovery and precision. By ingeniously linking streptokinase activity to carbon dot fluorescence, this novel assay provides a rapid, simple and eco-friendly method for selective streptokinase detection.

Cisplatin (CIS) and etoposide (ETP) combination therapy is highly effective for treating various cancers. However, the potential for pharmacokinetic interactions between these drugs necessitates selective sensing methods to quantitate both CIS and ETP levels in patient's plasma. This work develops a dual fluorescence probe strategy using glutathione-capped copper nanoclusters (GSH-CuNCs) and nitrogen-doped carbon dots (N-CDs) for the simultaneous analysis of CIS and ETP. The fluorescence signal of GSH-CuNCs at 615 nm increased linearly with CIS concentration while the N-CD emission at 480 nm remained unaffected. Conversely, the N-CD fluorescence was selectively enhanced by ETP with no interference with the CuNC fluorescence. Extensive materials characterization including UV-vis, fluorescence spectroscopy, XRD, and TEM confirmed the synthesis of the nanoprobes. The sensor showed high sensitivity with limits of detection of 6.95 ng mL⁻¹ for CIS and 7.63 ng mL⁻¹ for ETP along with excellent selectivity against potential interferences in rabbit plasma. Method feasibility was demonstrated with application to real rabbit plasma samples. The method was further applied to estimate the pharmacokinetic parameters of CIS before and after ETP coadministration. The dual nanoprobe sensing strategy enables rapid and selective quantitation of CIS and ETP levels to facilitate therapeutic drug monitoring and optimization of combination chemotherapy regimens.

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.