Graphite Screen-printed Electrodes Research Articles

Novel and simple electrochemical sensing platform based on polypyrrole nanotubes/ZIF-67 nanocomposite/screen printed graphite electrode for sensitive determination of metronidazole

Here, a simple, fast, and sensitive voltammetric sensor based on screen printed graphite electrode (SPGE) modified with polypyrrole nanotubes/zeolitic imidazolate framework-67 (PPy NTs/ZIF-67) nanocomposite is introduced for the metronidazole (MNZ) determination. The PPy NTs/ZIF-67 nanocomposite was synthesized and characterized by using X-ray diffraction (XRD) spectroscopy, field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques. The developed sensor based on PPy NTs-ZIF-67 nanocomposite modified SPGE shows an obvious reduction peak at −650 mV for MNZ, mainly due to the synergistic effects of the ZIF-67 and PPy NTs. Differential pulse voltammetry (DPV) was found to be the most suitable method for MNZ detection, showing a linear dynamic range of 0.01 to 500.0 µM and a low limit of detection (LOD) of 0.004 µM. In investigating the practicability, the PPy NTs/ZIF-67/SPGE sensor demonstrated efficient practicability with satisfactory recoveries (97.1 % to 103.5 %) and low relative standard deviation (RSD) values of 1.8–3.6 % for MNZ determination in MNZ tablets and urine samples.

Charged Microdroplets Deposition for Nanostructured-Based Electrode Surface Modification

Accelerated synthesis of gold nanoparticles (AuNPs) in charged microdroplets produced by electrospray ionization (ESI) was exploited to modify the surface of graphite screen-printed electrodes (GSPEs). The deposited AuNPs were then functionalized by the charged microdroplets deposition of 6-ferrocenyl-hexanethiol (6Fc-ht) solutions that act as reducing and stabilizing agents and provide electrochemical properties for the modified electrodes. The morphology and composition of the AuNPs were characterized by scanning electron microscopy (SEM). Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behavior of the modified electrodes. The results showed that the ESI microdroplets deposition technique produces uniform and well-dispersed AuNPs on GSPE, and optimal conditions for deposition were identified, enhancing GSPE electrocatalytic performance. Further functionalization by ESI microdroplets of AuNPs with 6Fc-ht demonstrated improved redox properties compared with the conventional self-assembled monolayer (SAM) method, highlighting the technique’s potential for the easy and fast functionalization of electrochemical sensors.

Label free electrochemical detection of 2-aminoindane

This study describes a label-free voltammetric detection of 2-aminoindane (2-AI), a novel psychoactive substance, using graphite screen-printed electrode modified with an electrochemically oxidized cobalt bis(dicarbollide) derivative (CoK/G/SPE). Morphological, structural and electrochemical characterization is assessed by using a computational approach, scanning electron microscopy, infrared spectrometry and electrochemical techniques. The binding/recognition of 2-AI (as a primary analyte) and 2,5-dimethoxy-4-iodoamphetamine (DOI, as interferent from category amphetamines) is compared, with CoK as a monomer as well as electrochemically deposited on the G/SPE surface. The mechanism of selectivity is proposed. The experimental findings show that these two stimulants compete for the binding/recognition sites on the modified electrode surface, with the adsorption constant values of (2.62 ± 0.67) x 105 and (6.10 ± 1.32) x 105, a linear range of 19.9 – 119 μmol L–1 and 9.97 – 235 μmol L–1, and the limit of detection 7.2 μmol L–1 and 2.37 μmol L–1 for 2-AI and DOI, respectively. An important point considering the analytical applicability and significance of CoK/G/SPE for forensic analysis is the possibility to distinguish 2-AI from an amphetamine derivative in a two-component mixture. The CoK/G/SPE electrodes are successfully applied to determine 19.9 μmol L–1 2-AI in spiked model samples with recovery values of 85.3–94.8 % and relative standard deviations 10–21 %. Such reproducibility is satisfactory considering the low cost of the electrode fabrication route.

Detection of the stimulant clobenzorex using voltammetry and screen-printed electrodes: A simple and fast screening method for application in seized samples and oral fluid of drivers

Clobenzorex (CBZ) is a stimulant drug, recognized for its anorectic potential, legally used in some countries for obesity treatment. However, CBZ is banned in much of the world and has been often used illegally by drivers needing to stay alert for extended periods. Therefore, the rapid identification of CBZ in forensic samples is of paramount importance for public health and safety. In this context, we introduce an innovative electroanalytical screening method for detecting CBZ in seized tablet samples and human oral fluid using voltammetry with a graphite screen-printed electrode (SPE-Gr). The electrochemical detection was optimized in phosphate buffer solution (0.1 mol L−1, pH 7.0) using square wave voltammetry (SWV). The SPE-Gr combined with SWV exhibited a good stability of the electrochemical responses for CBZ detection, with a relative standard deviation of less than 5% across different days (N = 5) and using different SPEs (N = 3). A linear detection range of 2.5–100.0 μmol/L (R2 = 0.992) was achieved, with a low limit of detection (LOD) of 0.32 μmol L−1. Interference studies with other illicit drugs and adulterants confirmed the selectivity of the proposed method for CBZ detection. In addition, the presence of CBZ in seized tablet samples and authentic oral fluids, collected from drivers, was detected and identified using the proposed method, which results were also confirmed by HPLC-MS. Consequently, integrating SPE-Gr with SWV offers a reliable, rapid, sensitive, selective, reproducible, and direct approach for the preliminary qualitative and quantitative analysis of CBZ in forensic contexts. Furthermore, the proposed method provides an efficient oral fluid test for CBZ screening in drivers under the influence of drugs.

The development of a disposable voltammetric sensor based on two-dimensional leaf-like ZIF-L (Zn) modified screen-printed graphite electrode for the simultaneous analysis of uric acid, dopamine and theophylline

The two-dimensional (2D) leaf-like zeolitic imidazolate framework-L (Zn) (ZIF-L (Zn)) was synthesized using a simple method in this study. The ZIF-L (Zn) was characterized using various techniques, such as FE-SEM, XRD, FT-IR, elemental mapping and EDX. The ZIF-L (Zn) was utilized to modify the surface of screen-printed graphite electrode (ZIF-L (Zn)/SPGE) to detect uric acid (UA). The sensor exhibited electrocatalytic behavior for uric acid in phosphate buffer solutions (PBS, 0.1 M), with a linear dependence between the current response and uric acid concentration in the dynamic range from 0.1 μM to 900.0 μM, a low limit of detection (LOD) of 0.04 μM, and good sensitivity of 0.0393 μA/μM under optimized experimental conditions. The ZIF-L (Zn)/SPGE sensor was successfully applied for uric acid determination in the presence of dopamine (DA) and theophylline (Thp) without any interference. The proposed electrode exhibits well-separated oxidation peaks at potentials of 139, 260 and 900 mV for dopamine, uric acid, and theophylline, respectively. In addition, the practical application of the fabricated sensor was demonstrated by detecting dopamine, uric acid, and theophylline in real samples.

Electrochemical classification of benzodiazepines: A comprehensive approach combining insights from voltammetry and liquid chromatography − mass spectrometry

The growing non-medical use of benzodiazepines (BZs) has led to the emergence of counterfeit BZ pills and new psycho-active substances (NPS) in the BZ class on the illicit market. Comprehensive analytical methods for BZ identification are required to allow law enforcement, first aid responders and drug-checking services to analyze a variety of sample types and contents to make timely decisions on the spot. In this work, the electrochemical behavior of diazepam (DZ), clonazepam (CZ) and alprazolam (AP) is studied on graphite screen-printed electrodes, both with and without dissolved oxygen in the solution, to link their redox signals to their chemical structure. After elucidation of their reduction mechanisms using liquid chromatography coupled to high-resolution mass spectrometry, three structural classes (Class 1, Class 2 and Class 3) were defined, each with different redox centers and electrochemical behavior. Subsequently, 22 confiscated pills containing 14 different BZs were correctly assigned to these three structural classes, with the deoxygenated conditions displaying the highest class selectivity. Finally, the three classes were successfully detected after being spiked into five alcoholic beverages in the context of drug-facilitated sexual assault. For analysis in red wine, which complicated the analysis by interfering with Class 1, a dual test strategy in pH 2 and pH 7 was proposed for accurate detection. Its rapid measurements, broad scope and lack of interference from diluents or colors makes this method a promising approach for aiding various services in combating problematic BZ use.

Screen-printed glassy carbon electrodes for electrogenerated chemiluminescence.

Glassy carbon (GC) electrodes are crucial in electrochemistry due to their chemical stability and excellent electrochemical behaviour. This study presents the development of screen-printed glassy electrodes and demonstrates their suitability for electrogenerated electrochemiluminescence (ECL) applications. Model ECL system tris (2,2′-bipyridyl) ruthenium (II)/tripropylamine (Ru(bpy)32+/TPA) is used to benchmark the new electrodes. Different ink formulations are presented, and the electrochemical performance of the corresponding printed electrodes is discussed. In contrast to graphite screen printed electrodes, laser activation did not result in significant benefits at these new GC electrodes. A range of characterization techniques such as scanning electron microscopy, Raman spectroscopy, and spectroelectrochemical methods are used in the study. ECL studies of the GC electrodes was studied using both UV–Vis spectroscopy and image analysis. An ink formulation consisting of a GC to binder ratio of 5:1 by weight yielded the best results, surpassing the response of commercial graphite screen-printed electrodes, and in line with conventional (bulk) glassy carbon electrodes.

Spectroscopic investigations of a commercial graphite screen printed electrode modified by bismuth oxide drop deposition and electrochemical reduction, for cadmium and lead ions simultaneous determination

A single use graphite screen-printed electrode (GSPE) was easily modified, to take advantage of the proven affinity of the nontoxic post-transition metal bismuth (Bi), for metal ions to be detected by Square Wave Anodic Stripping Voltammetry (SWASV). A bismuth oxide (Bi2O3) or a chitosan coated (CS@Bi2O3) nanopowder suspension was drop-casted on the graphite working electrode (WE) surface, giving rise to the precursor of a Bi-modified GSPE. After that, an electrochemical reduction was performed to obtain the Bi– or the CS@Bi–GSPE.X-ray photoelectron spectroscopy and micro-X-ray fluorescence investigations were performed on the graphitic structure pre and post modification. The bismuth oxide deposition amount was considered as critical parameter to sensor performance, indicating a minimum and maximum threshold. Under improved measurement conditions, with a 300 s pre-concentration time, the attained sensors exhibited a linearity in the range (2.0–20.0) μg L−1 in the simultaneous analysis of Pb(II) and Cd(II). The Bi–GSPE showed LODs of 1.7 and 0.5 μg L−1 for Cd(II) and Pb(II) respectively, while 1.5 μg L−1 for Cd(II) and 0.2 μg L−1 for Pb(II) were recorded by the CS@Bi–GSPE. As an applicative proof in real sample, a spike test was carried out in a ground water sample, without any preliminary sample treatment.

Electrochemical Nanosensor for the Simultaneous Determination of Anticancer Drugs Epirubicin and Topotecan Using UiO-66-NH2/GO Nanocomposite Modified Electrode.

In this work, UiO-66-NH2/GO nanocomposite was prepared using a simple solvothermal technique, and its structure and morphology were characterized using field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). An enhanced electrochemical sensor for the detection of epirubicin (EP) was proposed, which utilized a UiO-66-NH2/GO nanocomposite-modified screen-printed graphite electrode (UiO-66-NH2/GO/SPGE). The prepared UiO-66-NH2/GO nanocomposite improved the electrochemical performance of the SPGE towards the redox reaction of EP. Under optimized experimental conditions, this sensor demonstrates a remarkable limit of detection (LOD) of 0.003 µM and a linear dynamic range from 0.008 to 200.0 µM, providing a highly capable platform for sensing EP. Furthermore, the simultaneous electro-catalytic oxidation of EP and topotecan (TP) was investigated at the UiO-66-NH2/GO/SPGE surface utilizing differential pulse voltammetry (DPV). DPV measurements revealed the presence of two distinct oxidation peaks of EP and TP, with a peak potential separation of 200 mV. Finally, the UiO-66-NH2/GO/SPGE sensor was successfully utilized for the quantitative analysis of EP and TP in pharmaceutical injection, yielding highly satisfactory results.

Pharmacogenomic Studies of Antiviral Drug Favipiravir.

In this work, we conducted a study of the interaction between DNA and favipiravir (FAV). This chemotherapeutic compound is an antiviral drug for the treatment of COVID-19 and other infections caused by RNA viruses. This paper examines the electroanalytical characteristics of FAV. The determined concentrations correspond to therapeutically significant ones in the range of 50-500 µM (R2 = 0.943). We have shown that FAV can be electro-oxidized around the potential of +0.96 V ÷ +0.98 V (vs. Ag/AgCl). A mechanism for electrochemical oxidation of FAV was proposed. The effect of the drug on DNA was recorded as changes in the intensity of electrochemical oxidation of heterocyclic nucleobases (guanine, adenine and thymine) using screen-printed graphite electrodes modified with single-walled carbon nanotubes and titanium oxide nanoparticles. In this work, the binding constants (Kb) of FAV/dsDNA complexes for guanine, adenine and thymine were calculated. The values of the DNA-mediated electrochemical decline coefficient were calculated as the ratio of the intensity of signals for the electrochemical oxidation of guanine, adenine and thymine in the presence of FAV to the intensity of signals for the electro-oxidation of these bases without drug (S, %). Based on the analysis of electrochemical parameters, values of binding constants and spectral data, intercalation was proposed as the principal mechanism of the antiviral drug FAV interaction with DNA. The interaction with calf thymus DNA also confirmed the intercalation mechanism. However, an additional mode of interaction, such as a damage effect together with electrostatic interactions, was revealed in a prolonged exposure of DNA to FAV.

Flow-Through Amperometric Biosensor System Based on Functionalized Aryl Derivative of Phenothiazine and PAMAM-Calix-Dendrimers for the Determination of Uric Acid.

A flow-through biosensor system for the determination of uric acid was developed on the platform of flow-through electrochemical cell manufactured by 3D printing from poly(lactic acid) and equipped with a modified screen-printed graphite electrode (SPE). Uricase was immobilized to the inner surface of a replaceable reactor chamber. Its working volume was reduced to 10 μL against a previously reported similar cell. SPE was modified independently of the enzyme reactor with carbon black, pillar[5]arene, poly(amidoamine) dendrimers based on the p-tert-butylthiacalix[4]arene (PAMAM-calix-dendrimers) platform and electropolymerized 3,7-bis(4-aminophenylamino) phenothiazin-5-ium chloride. Introduction of the PAMAM-calix-dendrimers into the electrode coating led to a fivefold increase in the redox currents of the electroactive polymer. It was found that higher generations of the PAMAM-calix-dendrimers led to a greater increase in the currents measured. Coatings consisted of products of the electropolymerization of the phenothiazine with implemented pillar[5]arene and PAMAM-calix-dendrimers showing high efficiency in the electrochemical reduction of hydrogen peroxide that was formed in the enzymatic oxidation of uric acid. The presence of PAMAM-calix-dendrimer G2 in the coating increased the redox signal related to the uric acid assay by more than 1.5 times. The biosensor system was successfully applied for the enzymatic determination of uric acid in chronoamperometric mode. The following optimal parameters for the chronoamperometric determination of uric acid in flow-through conditions were established: pH 8.0, flow rate 0.2 mL·min-1, 5 U of uricase per reactor. Under these conditions, the biosensor system made it possible to determine from 10 nM to 20 μM of uric acid with the limit of detection (LOD) of 4 nM. Glucose (up to 1 mM), dopamine (up to 0.5 mM), and ascorbic acid (up to 50 μM) did not affect the signal of the biosensor toward uric acid. The biosensor was tested on spiked artificial urine samples, and showed 101% recovery for tenfold diluted samples. The ease of assembly of the flow cell and the low cost of the replacement parts make for a promising future application of the biosensor system in routine clinical analyses.

Eco-friendly spark-generated CoxOy nanoparticle-modified graphite screen-printed sensing surfaces for the determination of H2O2 in energy drinks

The modification of graphite screen-printed electrodes (SPEs) is reported using an eco-friendly and extremely fast method based on the direct cobalt pin electrode-to-SPE spark discharge at ambient conditions. This approach does not utilize any liquids or chemical templates, does not produce any waste, and allows the in-situ generation of CoxOy nanoparticles onto the electrode surface and the development of efficient electrocatalytic sensing surfaces for the determination of H2O2. Co-spark SPEs were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy (XPS), revealing the formation of surface confined CoxOy nanoparticles and the diverse oxidation states of cobalt species. Co-spark SPEs were also characterized with cyclic voltammetry and electrochemical impedance spectroscopy. Redox transitions of the surface confined electrocatalysts are demonstrated by electrochemical polarization studies, showing the formation of different oxides (CoxOy), varying the XPS results. Amperometric measurements at 0.3 V vs. Ag/AgCl revealed a linear relationship between the current response and the concentration of H2O2 over the range 1 − 102 μM, achieving a limit of detection (3σ/m) of 0.6 μM. The interference effect of various electroactive species was effectively addressed by employing dual measurements in the absence and presence of the enzyme catalase. The analytical utility of the method was evaluated in antioxidant rich real-world samples, such as energy drinks, demonstrating sufficient recovery.Graphical

Simple and sensitive voltammetric sensor for in‐situ clinical and environmental 17‐β‐estradiol monitoring

AbstractThe direct electrochemical oxidation of 17‐β‐estradiol (E2) at conventional electrodes gives weak current signals making detection at trace levels difficult, as required for clinical and environmental applications. In order to strengthen the electrochemical behavior of E2, a simple and sensitive sensor has been realized based on a graphite screen printed electrode (GSPE) functionalized according to a two‐step procedure: i) drop‐casting deposition of gold nanoparticles (AuNPs); ii) electropolymerization of methylene blue (MB). The final PMB‐AuNPs‐GSPE platform was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The pH value was optimized in order to obtain the best detection efficiency and the highest peak current response was obtained at pH 7.0. The synergistic contributions of both AuNPs and PMB allowed the proposed sensor to show a wide linear range from 0.5 to 125.0 μmol L−1 with a LOD of 41 nmol L−1, long‐term stability and good reproducibility (RSD=2.9 % for n=10). Moreover, the sensor was able to distinguish E2 from several interfering compounds commonly present in urine and river water as well as from other endocrine‐ disrupting chemicals (EDCs), denoting its high specificity to E2 molecule. Finally, the developed electrode platform was successfully applied to the determination of E2 in both human urine and river water samples without any purification step under the standard addition method.

Synchronous analysis of acetaminophen, codeine, and caffeine in human fluids employing graphite screen-printed electrodes.

A facile electrochemical approach is proposed for the synchronous determination of acetaminophen (ACP), codeine (COD) and caffeine (CAF) utilizing unmodified screen-printed electrodes (SPEs). The determination of ACP, COD and CAF has been explored across different supporting electrolytes including sulfuric acid (H2SO4), hydrochloric acid (HCl), phosphoric acid (H3PO4) and Briton Robinson (B.R) buffer solutions. It was found that a 0.05 mol L-1 sulfuric acid solution is an optimal supporting electrolyte utilized for voltammetric analysis of ACP, COD, and CAF with improved sensitivity, stability, and reproducibility. The electro-analytical sensing of ACP, COD and CAF was investigated using SPEs within linear concentration ranges of 3.0-35.0 μmol L-1, 10-160 μmol L-1 and 10-160 μmol L-1 and revealed competitively low limits of detection (3S/N) of 0.9, 4.8 and 6.3 μmol L-1 for ACP, COD and CAF, respectively. The results indicated the possibility of such a simple and quick electroanalytical protocol for online monitoring of pharmaceutical formulations comprising ACP, COD, and CAF drugs in human fluids with satisfactory recovery.

Synthesis of ZnO@TiO2 nanoparticles and its application to construct an electrochemical sensor for determination of hydrazine

In the present research, ZnO@TiO2 nanoparticles (ZnO@TiO2 NPs) was synthesized by using a simple method and the results of infrared (IR), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and energy-dispersive X-ray spectroscopy (EDX) confirmed their synthesis. Then, an electrochemical sensor based on screen printed graphite electrode (SPGE) modified with ZnO@TiO2 NPs was developed for voltammetric detection of hydrazine in water samples. The ZnO@TiO2 NPs modified SPGE demonstrates significant performance toward the hydrazine detection due to the synergistic effect between ZnO NPs and TiO2 NPs and it proved by the results from cyclic voltammetry (CV). Also, the observation of an oxidation peak without a reduction peak in the opposite scan direction indicated the irreversibility of the electrochemical oxidation of hydrazine on both the bare SPGE and the ZnO@TiO2/SPGE. Under optimized conditions (pH and differential pulse parameters), the voltammetric current response of hydrazine at the ZnO@TiO2/SPGE showed linear dependence on the concentration, ranging from 0.01 µM to 585.0 µM with a limit of detection (LOD) of 0.005 µM. In addition, the pertinency of the ZnO@TiO2/SPGE sensor for practical applications was investigated by quantification detection of hydrazine in water samples. The findings showed recovery values between 97.3 % and 104.2 % and relative standard deviations (RSDs) ≤ 3.5 % for river and tap water samples.

Stereoselective Voltammetric Biosensor for Myo-Inositol and D-Chiro-Inositol Recognition.

This paper describes the development of a simple voltammetric biosensor for the stereoselective discrimination of myo-inositol (myo-Ins) and D-chiro-inositol (D-chiro-Ins) by means of bovine serum albumin (BSA) adsorption onto a multi-walled carbon nanotube (MWCNT) graphite screen-printed electrode (MWCNT-GSPE), previously functionalized by the electropolymerization of methylene blue (MB). After a morphological characterization, the enantioselective biosensor platform was electrochemically characterized after each modification step by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The results show that the binding affinity between myo-Ins and BSA was higher than that between D-chiro-Ins and BSA, confirming the different interactions exhibited by the novel BSA/MB/MWCNT/GSPE platform towards the two diastereoisomers. The biosensor showed a linear response towards both stereoisomers in the range of 2-100 μM, with LODs of 0.5 and 1 μM for myo-Ins and D-chiro-Ins, respectively. Moreover, a stereoselectivity coefficient α of 1.6 was found, with association constants of 0.90 and 0.79, for the two stereoisomers, respectively. Lastly, the proposed biosensor allowed for the determination of the stereoisomeric composition of myo-/D-chiro-Ins mixtures in commercial pharmaceutical preparations, and thus, it is expected to be successfully applied in the chiral analysis of pharmaceuticals and illicit drugs of forensic interest.

IMMUNOSENSOR BASED ON SCREEN-PRINTED GRAPHITE ELECTRODES MODIFIED WITH GOLD NANOPARTICLES AND SYNTHETIC MEMBRANE-LIKE SUBSTANCE FOR THE DETERMINATION OF CHLORAMPHENICOL

An electrochemical immunosensor based on screen-printed graphite electrodes has been developed for the determination of the antibiotic chloramphenicol in water and milk samples. It has been shown that the immobilization of chloramphenicol-specific antibodies in a liquid crystal layer of a membrane-like didodecyldimethylammonium bromide preserves the mobility and accessibility of active centers of antibodies, and the addition of gold nanoparticles improves electron transfer from the electrode surface to the redox centers of horseradish peroxidase used as a label. The limit of detection of chloramphenicol in water was 0.02 μg/L, in milk - 0.04 μg/L. The method can be used to determine residual amounts of chloramphenicol in animal products.

Immunosensor Based on Screen-Printed Graphite Electrodes Modified with Gold Nanoparticles and a Synthetic Membrane-Like Substance for the Determination of Chloramphenicol

Immunosensor Based on Screen-Printed Graphite Electrodes Modified with Gold Nanoparticles and a Synthetic Membrane-Like Substance for the Determination of Chloramphenicol

A novel dsDNA decamer-based electrochemical biosensor for selective determination of irinotecan active metabolite - SN38

This paper presents a novel biosensor for detecting the active metabolite of irinotecan, SN38, with high selectivity and sensitivity. The biosensor utilizes a dsDNA decamer (5′-GCGTTGTCGC-3′) that selectively interacts with SN38. The biosensor, consisting of a screen-printed graphite electrode with the dsDNA decamer as the recognition layer, demonstrates stability, sensitivity, and selectivity towards SN38 through electrochemical studies. It offers a wide linear range of 1–200 nM, comparable to the high-performance liquid chromatography (HPLC) method, with a sensitivity of 57 nA/nM and a detection limit of 1.06 nM. Compared to a bare graphite electrode, the biosensor exhibits a significant 31-fold increase in sensitivity and a detection limit three orders of magnitude lower. Selectivity studies were conducted using electrochemically active and inactive interferents, including biologically active compounds. Bioreceptor interactions with chosen interferents were examined using HPLC and nuclear magnetic resonance (NMR). Tests of the biosensor was performed using laboratory samples and artificial urine samples spiked with SN38. This disposable biosensor, based on dsDNA, provides an innovative approach for accurately determining SN38 levels in the therapeutic drug concentration range. It holds promise as an alternative method for clinical diagnosis and monitoring of SN38 levels in cancer patients undergoing irinotecan treatment.

ZnO Hollow Quasi-Spheres Modified Screen-Printed Graphite Electrode for Determination of Carmoisine.

Food colorants are important in food selection because they improve the gastronomic appeal of foods by improving their aesthetic appeal. However, after prolonged use, many colorants turn toxic and cause medical problems. A synthetic azo-class dye called carmoisine gives meals a red color. Therefore, the carmoisine determination in food samples is of great importance from the human health control. The current work was developed to synthesis ZnO hollow quasi-spheres (ZnO HQSs) to prepare a new electrochemical carmoisine sensor that is sensitive. Field emission-scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) have been used to analyze the properties of prepared ZnO HQSs. A screen-printed graphite electrode (SPGE) surface was modified with ZnO HQSs to prepare the ZnO HQSs-SPGE sensor. For carmoisine detection, the ZnO HQSs-SPGE demonstrated an appropriate response and notable electrocatalytic activities. The carmoisine electro-oxidation signal was significantly stronger on the ZnO HQSs-SPGE surface compared to the bare SPGE. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CHA), and differential pulse voltammetry (DPV) have been utilized to investigate the suggested protocol. The DPV results revealed an extensive linear association between variable carmoisine concentrations and peak current that ranged from 0.08 to 190.0 µM, with a limit of detection (LOD) as narrow as 0.02 µM. The ZnO HQSs-SPGE's ability to detect carmoisine in real samples proved the sensor's practical application.