Mona A. Mohamed

Novel MWCNTs/graphene oxide/pyrogallol composite with enhanced sensitivity for biosensing applications

A novel and highly sensitive biosensor employing graphene oxide nano-sheets (GO), multiwalled carbon nanotubes (MWCNTs), and pyrogallol (PG) was fabricated and utilized for the sensitive determination of omeprazole (OME). The morphological and structural features of the composite material were characterized using different techniques. The modified electrode showed a remarkable improvement in the anodic oxidation activity of OME due to the enhancement in the current response compared to the bare carbon paste electrode (CPE). Sensor composition and measurement conditions were optimized using an experimental design. Differential pulse voltammetry (DPVs) exhibited two expanded linear dynamic ranges of 2.0×10-10-6.0×10-6M and 6.0×10-6-1.0×10-4M for OME at pH 7 with a detection limit of 1.02×10-11M. The practical analytical utilities of the modified electrode were demonstrated by the accurate determination of OME in pharmaceutical formulation and human serum samples with mean recoveries of 100.97% and 98.58%, respectively. The results clearly revealed that the proposed sensor is applicable to clinical analysis, quality control and routine determination of drugs in pharmaceutical formulations.

Electroanalytical sensing of the antimicrobial drug linezolid utilising an electrochemical sensing platform based upon a multiwalled carbon nanotubes/bromocresol green modified carbon paste electrode

The electroanalytical sensing of linezolid (LIN) is explored utilising an electrochemical sensing platform based upon a multiwalled carbon nanotubes (MWCNTs)/bromocresol green (BCG) modified carbon paste electrode (MWCNT/BCG/CPE). Cyclic voltammetry, differential pulse voltammetry, chronoamperometry, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy techniques are all used to characterise the properties of the electrochemical sensor. The synergetic effects of BCG and MWCNTs result in an electrocatalytic-type response providing a significantly improved electroanalytical response compared to a bare unmodified CPE. Additionally, the MWCNT/BCG/CPE sensing platform outperforms electrochemical sensors previously reported in the literature with a larger linear response and lower limit of detection. The MWCNT/BCG/CPE electrochemical sensing platform was evaluated towards the sensing of LIN where a linear range from 5.00 × 10−8 to 1.45 × 10−4 mol L−1 with a good linearity and high correlation (0.9968) was observed with the limits of detection and quantification found to correspond to 7.57 × 10−9 and 2.50 × 10−8 mol L−1 respectively. The proposed sensor was applied to the determination of LIN in the presence of cefixime trihydrate (CEF) which are both found in combined dose tablet formulations. The sensor was shown to be successfully applied to the determination of LIN in a pharmaceutical formulation and human urine and saliva samples with satisfactory recoveries. The proposed electrochemical sensing platform is simple and inexpensive and has the potential to be applied to clinical analysis, quality control and the routine determination of drugs in pharmaceutical formulations.

New voltammetric analysis of olanzapine in tablets and human urine samples using a modified carbon paste sensor electrode incorporating gold nanoparticles and glutamine in a micellar medium

An effective novel electrochemical sensor for the selective determination of olanzapine (OLA) was introduced. The prepared sensor was based on a carbon paste electrode chemically modified with glutamine (GL) and gold nanoparticles (GNs) in the presence of sodium dodecyl sulphate (SDS) in the medium. The effect of carbon paste composition and scan rate were tested. The working solution pH was 7. The analytical method validation parameters were studied. The linear response was obtained for OLA in the range of 5 × 10−7 to 1.25 × 10−4 M with a correlation coefficient of 0.9986. LOD and LOQ were calculated and found to be 3.58 × 10−9 and 1.19 × 10−8 M, respectively. The utility of this sensor was examined for the determination of OLA in its pharmaceutical dosage form and human urine. Also the proposed method was applied for the simultaneous determination of OLA, fluoxetine (FLX), ascorbic acid (AA) and uric acid (UA).

Smart bi-metallic perovskite nanofibers as selective and reusable sensors of nano-level concentrations of non-steroidal anti-inflammatory drugs

A strategy for trace-level carbon-based electrochemical sensors is investigated via exploring the interesting properties of BaNb2O6 nanofibers (NFs). Utilizing adsorptive stripping square wave voltammetry (ASSWV), an electrochemical sensing platform was developed based on BaNb2O6 nanofibers-modified carbon paste electrode (CPE) for the sensitive detection of lornoxicam (LOR). Different techniques were used to characterize the fabricated BaNb2O6 perovskite NFs. The obtained data show the feasibility to electro-oxidize LOR and paracetamol (PAR) on the surface of the fabricated sensor. The amount of nanofiber and testing conditions were optimized using response surface methodology and ASSWV technique. The optimized BaNb2O6/CPE sensor exhibits low detection limit of 6.39 × 10-10 mol L-1, even in the presence of the co-formulated drug paracetamol (PAR). The sensor was successfully applied for biological applications.

Electrochemical Determination of the Serotonin Reuptake Inhibitor, Dapoxetine, Using Cesium–Gold Nanoparticles

Cesium–gold (Cs–Au) nanoparticles are shown to be analytically advantageous for the electroanalytical sensing of dapoxetine (DPX), a serotonin reuptake inhibitor used for the treatment of premature ejaculation. The Cs–Au nanoparticles are electrically wired and supported upon mass producible, economical screen-printed electrochemical sensing platforms and are characterized electrochemically (cyclic voltammetry and electrochemical impedance spectroscopy) and physiochemically (field emission scanning electron microscopy and energy dispersive X-ray analysis). The face-centered design was applied to optimize the significant experimental factors by using square wave voltammetry. The Cs–Au-based sensor is found to exhibit a large linear range (10–7 to 10–4 M) with a good analytical linearity with the limits of detection and quantification corresponding to 2.50 × 10–10 and 8.33 × 10–8 M, respectively. The developed sensor was successfully applied in the quantification of DPX in the presence of sildenafil, both of which are commonly found within combined dose tablet pharmaceutical formulations. The proposed DPX electrochemical Cs–Au-based sensor has the advantages of being single-shot and disposable and is shown to be successful in determining DPX in pharmaceutical formulations, human urine, and serum samples with acceptable recoveries.

3D spongy graphene-modified screen-printed sensors for the voltammetric determination of the narcotic drug codeine

Adenine-functionalized spongy graphene (FSG) composite, fabricated via a facile and green synthetic method, has been explored as a potential electrocatalyst toward the electroanalytical sensing of codeine phosphate (COD). The synthesized composite is characterized using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray powder diffraction, UV-vis absorption spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy (HRTEM), and thermogravimetric analysis. The FSG was electrically wired via modification upon screen-printed (macro electrode) sensors, which behave as a hybrid electrode material for the sensitive and selective codeine phosphate (COD) determination in the presence of paracetamol (PAR) and caffeine (CAF). The FSG- modified sensor showed an excellent electrocatalytic response towards the sensing of COD with a wide linear response range of 2.0 × 10-8-2.0 × 10-4M and a detection limit (LOD) of 5.8 × 10-9M, indicating its potential for the sensing of COD in clinical samples and pharmaceutical formulations.

Smart electrochemical sensing platform for the simultaneous determination of psychotic disorder drugs isopropamide iodide and trifluoperazine hydrochloride

A novel, simple and highly sensitive sensor for the simultaneous determination of isopropamide iodide (ISP) and trifluoperazine hydrochloride (TFP) was developed. A carbon paste electrode was modified with m-cresol purple (MCP) and carboxylated multiwalled carbon nanotubes (MWCNTs). Different techniques were used to characterize the nanostructure and performance of the sensor. Under the optimized experimental conditions, ISP and TFP showed linear responses over the ranges of 5.50 × 10−6–1.70 × 10−4 and 5.00 × 10−7–1.34 × 10−3 mol L−1, respectively. The detection limits for ISP and TFP were found to be 9.91 × 10−7 mol L−1 and 1.10 × 10−7 mol L−1, respectively. Satisfactory recoveries of analytes from these samples were demonstrated, indicating that the suggested sensor is highly suitable for clinical analysis, quality control and routine determination of ISP and TFP in pharmaceutical formulations and human fluids.

Magnetic cobalt ferrite nanoparticles CoFe2O4 platform as an efficient sensor for trace determination of Cu(II) in water samples and different food products

In the present work, we aimed to demonstrate the fabrication of a novel electrochemical sensor for the trace determination of Cu(II) in different food matrices. The new sensor was fabricated using cobalt ferrite nanoparticles (CoFe2O4) which were prepared via an eco-friendly green method. The prepared nanoparticles were investigated and characterized using different techniques. The described differential pulse anodic stripping voltammetry (DP-ASV) was optimized and validated. Under the optimal conditions, the sensor showed sensitive response to Cu determination over a wide linear range. The limits of detection and quantification were found to be 0.085 and 0.284 ppb, respectively, which are considered as lower than the reported limits. Furthermore, the developed method was applied for trace quantitation of Cu in water, oil, sugar and tea. This was carried out without interferences from various inorganic and organic species. Satisfactory recoveries of Cu from samples clearly revealed that the proposed sensor can be applied into quality control and routine determination of Cu samples.

An engineered nanocomposite for sensitive and selective detection of mercury in environmental water samples

We report on a novel carbon-based nanocomposite made of reduced graphene oxide/titania nanotubes (RGO/TNT) with excellent conductivity and absorptivity for the sensitive electrochemical determination of Hg(II) as a water pollutant. Field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, FTIR spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy were used to characterize the morphological, structural, and electrochemical properties of the fabricated modifier. Square wave anodic stripping voltammetry was applied for the analytical measurements. The parameters influencing the peak current response were studied and optimized. The linear response of detection toward Hg(II) was found to be in the range of 2.5 × 10−10–5 × 10−6 M with a high regression coefficient (0.999). The limit of detection was found to be 4 × 10−11 M. The investigated sensing platform was tested for Hg(II) simultaneously in the presence of Cu(II) and Mn(II) and proved to have high sensitivity, selectivity, and reproducibility. Finally, the modified electrode was used for the trace level detection of Hg(II) in real environmental water samples, showing promising results.