Analysis of carbamazepine serum by differential pulse voltammetry (DPV) and comparison with fluorescence polarization immunoassay (FPIA): an animal study

Electrochemical Carbamazepine Aptasensor for Therapeutic Drug Monitoring at the Point of Care

Monitoring the anti-epileptic drug carbamazepine (CBZ) is crucial for proper dosing, optimizing a patient's clinical outcome, and managing their medication regimen. Due to its narrow therapeutic window and concentration-related toxicity, CBZ is prescribed and monitored in a highly personalized manner. We report an electrochemical conformation-changing aptasensor with two assay formats: a 30 min assay for routine monitoring and a 5 min assay for rapid emergency testing. To enable "sample-to-answer" testing, a de novo CBZ aptamer (K _d < 12 nM) with conformational switching due to a G-quadruplex motif was labeled with methylene blue and immobilized on a gold electrode. The electrode fabrication and detection conditions were optimized using electrochemical techniques and visualized by atomic force microscopy (AFM). The aptasensor performance, including reproducibility, stability, and interference, was characterized using electrochemical impedance spectroscopy and voltammetry techniques. The aptasensor exhibited a wide dynamic range in buffer (10 nM to 100 μM) with limits of detection of 1.25 and 1.82 nM for the 5 and 30 min assays, respectively. The clinical applicability is demonstrated by detecting CBZ in finger prick blood samples (<50 μL). The proposed assays provide a promising method to enable point-of-care monitoring for timely personalized CBZ dosing.

A new molecular imprinted PEDOT glassy carbon electrode for carbamazepine detection

An electrochemical sensor for the detection of carbamazepine was fabricated by the electropolymerization of PEDOT on glassy carbon electrodes. Molecular imprinted polymer sites were synthesized by cyclic voltammetry on the electrodes' surfaces providing high selectivity and sensitivity towards carbamazepine molecules. Scanning electron microscopy validated the formation of the polymer. Extraction of carbamazepine from the polymer was performed by immersion in acetonitrile and validated by ultraviolet-visible spectroscopy along with cyclic voltammetry experiments comparing pre- and post-template extraction data. Further cyclic voltammetry and square-wave voltammetry tests aided in characterizing the electrodes' response to carbamazepine concentration in PBS solution with [Fe(CN)₆]^3-/4- as a redox pair/mediator. The limits of detection and quantification were found to be 0.98 x 10^-3 M and 2.97 x 10^-3 M respectively. The biosensor was highly sensitive to carbamazepine molecules in comparison to non-imprinted electrodes, simple to construct and easy to operate.

Two-Dimensional Metallic NiSe2 Nanoclusters-Based Low-Cost, Flexible, Amperometric Sensor for Detection of Neurological Drug Carbamazepine in Human Sweat Samples

Here we report a low-cost, flexible amperometric sensing platform for highly selective and sensitive detection of carbamazepine (CBZ) in human sweat samples. Detailed morphological characterization of the two-dimensional transition metal dichalcogenide NiSe₂, synthesized using one-step hydrothermal method, confirms the formation of dense NiSe₂ nanoclusters in the range of 500–650 nm, whereas X-ray diffraction and X-ray photoelectron spectroscopy studies reveal a stable and pure cubic crystalline phase of NiSe₂. The sensor device is fabricated by uniformly depositing an optimized weight percentage of as-synthesized NiSe₂ onto flexible and biocompatible polyimide substrate using spin coating, and metal contacts are established using thermal evaporation technique. The sensor exhibits a remarkable sensitivity of 65.65 μA/nM over a wide linear range of 50 nM to 10 μM CBZ concentrations and a low limit of detection of 18.2 nM. The sensing mechanism and excellent response of NiSe₂ toward CBZ can be attributed to the highly conductive metallic NiSe₂, large electroactive surface area of its nanoclusters, and highly interactive Ni²⁺/Ni³⁺ oxidation states. Furthermore, the presence of 10-fold excess of capable interferents, such as lactic acid, glucose, uric acid, and ascorbic acid, does not affect the accurate determination of CBZ, thus demonstrating excellent selectivity. The real-time detection of CBZ is evaluated in human sweat samples using standard addition method, which yields reliable results. Furthermore, the sensor shows excellent robustness when subject to bending cycles and fast response time of 2 s. The strategy outlined here is useful in developing sensing platforms at low potential without the use of enzymes or redox binders for applications in healthcare.

Stability indicating spectrophotometric methods for quantitative determination of carbamazepine and its degradation product, iminostilbene, in pure form and pharmaceutical formulations

A stressed study on the stability and degradation behavior under ICH forced degradation conditions of most widely used antiepileptic drug; carbamazepine (CMZ) is presented in this work. The research also includes studying spectrophotometric nature of CMZ and assaying it with mostly used spectrophotometric techniques. Six simple and sensitive spectrophotometric methods are introduced as stability indicating methods for quantitative determination of CMZ and its degradation product, one of its reported potential impurities; iminostilbene (IMS). Dual wavelength is method I where two wavelengths (215 and 270 nm for CMZ and 258 and 307 nm for IMS) were chosen for each component while absorbance difference is zero for the second one. Method II is isoabsorptive point method where the absorbance of CMZ at A_{225 nm} was measured in the range of 0.5-20 μg mL^-1. Method III is second derivative method which allows simultaneous determination of CMZ at 247 nm and IMS at 273 nm without any interference. Method IV based on measuring the peak amplitude of first derivative of ratio spectra (¹DD) at 280.5 and 253 nm for determination of CMZ and IMS, respectively. Method V is mean centering of the ratio spectra with good linearity for CMZ and IMS over 200-330 nm. Ratio difference method is method VI where good linearity was achieved for determination of CMZ and IMS by measuring differences in the amplitude of ratio spectra at 285, 258 nm and 258, 285 nm, respectively. The proposed methods show successful application in CMZ's pharmaceutical formulations.

Application of fluorescence polarization immunoassay for determination of carbamazepine in wastewater

Carbamazepine is an antiepileptic drug that can be used as a marker for the cleaning efficiency of wastewater treatment plants. Here, we present the optimization of a fast and easy on-site measurement system based on fluorescence polarization immunoassay and the successful application to wastewater. A new monoclonal highly specific anti-carbamazepine antibody was applied. The automated assay procedure takes 16 min and does not require sample preparation besides filtration. The recovery rates for carbamazepine in wastewater samples were between 60.8 and 104% with good intra- and inter-assay coefficients of variations (less than 15 and 10%, respectively). This automated assay enables for the on-site measurement of carbamazepine in wastewater treatment plants.