The monitoring of ziram levels is of vital importance due to its widespread application in agriculture and the possible risks it poses to human health and the ecosystem. This work proposes an innovative approach for the highly sensitive and selective sensing of ziram, a widely used dithiocarbamate fungicide, through the formation of copper dimethyldithiocarbamate Cu)DDC)₂ assisted dual quenching of red and blue emission carbon dots (R/NCDs and B/NSCDs). When ziram is added to a system containing copper-bound B/NSCDs and R/NCDs, the displacement of ziram zinc ions by copper ions leads to the formation of a yellow-colored Cu)DDC)₂ complex. This complex induces significant quenching of the fluorescence emissions from both types of carbon dots, consequently enhancing the sensitivity of the detection method. Comprehensive characterization of the R/NCDs and B/NSCDs was conducted using various spectroscopic and morphological techniques to elucidate their structural and optical properties. The quenching mechanism was confirmed through different spectroscopic techniques, including fluorescence lifetime measurements, UV–vis spectroscopy, and Stern-Volmer analysis. The proposed method demonstrated high sensitivity across a wide concentration ranging from 20 to 1000 ng mL⁻¹, making it suitable for trace-level detection of ziram. Moreover, the method exhibited excellent selectivity and recovery when applied to real samples, such as apples, grains, and water matrices. The combination of high sensitivity, selectivity, and applicability to diverse sample matrices makes this carbon dot-based dual quenching method a promising approach for fast and accurate detection of ziram in various environmental and agricultural applications.

This study develops a novel fluorometric method for the sensitive and selective determination of urea, based on unique system comprising nitrogen doped red-emissive carbon dots (NRECDs), zinc-dithizone complex, and the urease enzyme. The underlying principle of this method relies on the pH increase resulting from the enzymatic breakdown of urea by urease. Initially, the fluorescence of the NRECDs is quenched by the red-colored zinc-dithizone complex. However, upon the addition of urea, the subsequent release of ammonia and the consequent rise in pH lead to the dissociation of the zinc-dithizone complex, causing a color change from red to yellow. This spectral shift eliminates the quenching effect, resulting in the restoration of the CDs’ fluorescence. The prepared NRECDs were comprehensively characterized using various spectroscopic techniques, including fluorometry, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, and transmission electron microscopy (TEM) imaging. The proposed fluorometric method exhibits excellent sensitivity (Limit of detection = 0.0012 mM) and linearity (R² = 0.9951) in the determination of urea. Notably, this approach addresses the selectivity limitations of previous pH-sensitive CDs-based methods, which relied solely on the intrinsic response of CDs, lacking specificity in either quenching or fluorescence enhancement. Furthermore, the developed method demonstrates remarkable selectivity, as evidenced by negligible interference from various potentially interfering substances, ensuring reliable and accurate urea quantification. When applied to human serum samples, the method showcased excellent recovery with low relative standard deviations, highlighting its practical applicability in biomedical and clinical applications.

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.