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2022
Fares, M. Y., N. S. Abdelwahab, M. A. Hegazy, M. M. Abdelrahman, A. M. Mahmoud, and G. M. El-Sayed, "Nanoparticle-enhanced in-line potentiometric ion sensor for point-of-care diagnostics for tropicamide abuse in biological fluid.", Analytica chimica acta, vol. 1192, pp. 339350, 2022. Abstract

Point of care (POC), also identified as on-site testing, has evolved as a rapid and accurate technique for drug of abuse screening and analysis. The aim of this work is to detect tropicamide (TPC) abuse in biological fluids; we selected rat plasma as example. We developed a disposal miniaturized, portable, green, and budget-friendly POC solid-state electrochemical sensor based on potentiometric transduction. To attain that, an innovative microfabricated electrode modified with conducting polymer poly(3-octylthiophene) (POT) has been placed on sensitized printed circuit board (PCB). A two-stage optimization process was implemented to develop the fabricated electrode. The first stage of the optimization process depends on screening various ionophores in order to enhance the sensor selectivity towards tropicamide. Copper nanoparticles exhibited the highest selectivity towards TPC. The second stage was utilizing a polymer as an ion-to-electron transducer layer between the copper nanoparticles impregnated ion sensing membrane and the microfabricated solid-contact ion-selective electrode. This polymer was added to boost the stability of the potential drift (1.2 mV/h) due to the hydrophobic behavior of the POT, which precludes the formation of an aqueous layer at the Cu electrode/polymeric membrane interface and improve the limit of detection (1.1 × 10 M). Nernstian potentiometric response was accomplished for TPC with a slope of 58.46 ± 0.43 mV/decade and E ∼ 189.39 ± 2.12 over the concentration range 1.0 × 10 to 1.0 × 10 M. The suggested sensor's intrinsic figure of merits include a quick response time (13 ± 2 s) and long life time (45 days). The proposed sensor has been successfully employed in the selective determination of TPC in pharmaceutical formulations, and biological fluids. When the results were compared to those of the official approach, there was no statistically significant difference. The Eco-Scale tool assessed and measured the greenness profile of the established method.

Azab, N. E. F., A. M. Mahmoud, and Y. A. Trabik, "Point-of-care diagnostics for therapeutic monitoring of levofloxacin in human plasma utilizing electrochemical sensor mussel-inspired molecularly imprinted copolymer", Journal of Electroanalytical Chemistry, vol. 918, pp. 116504, 2022.
ElMously, D. A., A. M. Mahmoud, A. M. Abdel-Raoof, and E. Elgazzar, "Synthesis of Prussian Blue Analogue and Its Catalytic Activity toward Reduction of Environmentally Toxic Nitroaromatic Pollutants", ACS Omega, vol. 7, issue 47, pp. 43139–43146, 2022.
2021
Abo-Elmagd, I. F., A. M. Mahmoud, M. A. Al-Ghobashy, M. Nebsen, N. S. El Sayed, S. Nofal, S. H. Soror, R. Todd, and S. A. Elgebaly, "Impedimetric Sensors for Cyclocreatine Phosphate Determination in Plasma Based on Electropolymerized Poly(o-phenylenediamine) Molecularly Imprinted Polymers", ACS Omega, vol. 6, issue 46, pp. 31282–31291, 2021.
Safwat, N., A. M. Mahmoud, M. F. Abdel-Ghany, and M. F. Ayad, "In situ monitoring of triclosan in environmental water with subnanomolar detection limits using eco-friendly electrochemical sensors modified with cyclodextrins.", Environmental science. Processes & impacts, vol. 23, issue 3, pp. 457-466, 2021. Abstract

The environmental emergence of unexpected contaminants has gained the attention of the scientific community. A broad spectrum antimicrobial compound named triclosan (TCS) was detected in the environment as an emerging contaminant. Owing to its inherent toxicity, we have proposed eco-friendly potentiometric liquid state sensors to be used for monitoring and quantifying TCS in environmental water samples. The proposed sensors have been optimized by modifying the inner filling solution using hydrophilic 2-hydroxypropyl β-cyclodextrin as a complexing agent to be capable of minimizing the trans-membrane ion flux and hence improving the selective and sensitive determination of TCS in environmental matrices with low LOD values. The obtained linear response of the optimized sensor was (1 × 10 to 1 × 10 M) compared to the control sensor (1 × 10 to 1 × 10 M). The obtained limit of detection (LOD) value was found to be 9.86 × 10 M compared to 9.78 × 10 M of the control sensor. The modification of the inner filling solution of the sensor with 2-hydroxypropyl β-cyclodextrin improves not only its sensitivity but also its response time to be only 5 seconds. The electrical performance of the proposed sensor was evaluated following IUPAC recommendations. Both the pH and temperature effects were studied and optimized. Two different greenness assessment tools, Analytical Eco-scale and Green Procedure Index, were adopted upon the evaluation of the proposed sensors' greenness.

Abd El-Rahman, M. K., G. Mazzone, A. M. Mahmoud, E. Sicilia, and T. Shoeib, "Novel choline selective electrochemical membrane sensor with application in milk powders and infant formulas.", Talanta, vol. 221, pp. 121409, 2021. Abstract

Choline (Ch), is a vitamin-like essential water-soluble organic micronutrient. The US-FDA requires that infant formula not made from cow's milk must be supplemented with Ch. Direct determination of Ch in milk powders and infant formulas is a challenging task due to the lack of a detectable chromophore, its existence in free and complexed forms as well as the presence of multi-analytes in these complex matrices. Here, an enzyme-free potentiometric ion selective electrode (ISE) with high selectivity for Ch, a linear range from 0.03 μM up to 1 mM, a 0.061 μM detection limit (LOD) and a typical response time less than 5 and no greater than 60 s is developed for monitoring of Ch in infant formula and milk powders. To achieve these ISE parameters we relied on the ability of calixarenes and its derivatives to form host-guest complexes with the positively charged quaternary ammonium moiety of Ch. We employed a lipophilic (membrane-compatible) calixarene as an ionophore in the sensing membrane phase to provide a molecular receptor for Ch capable of selective binding; while utilizing, hydrophilic (water-soluble) p-sulfonated calixarene as a buffering agent to optimize the inner filling solution to reduce transmembrane Ch fluxes. All the calixarene structures and their complexes with Ch were optimized at the density functional theory (DFT) level and the Gibbs free energies for the inclusion of Ch into the calixarenes were calculated. The prepared sensor was shown to selectively respond only to Ch in the presence of all other interferents in the tested matrices with results that are not statistically significantly different for either accuracy or precision relative to the much more laborious official AOAC 1999 coupled enzymatic-spectrophotometric method. The proposed method is highly selective, non-enzymatic, requires no derivatization or incubation steps, offers a fast response time, and has the potential of portability for in situ analysis, while being relatively cost effective and non-laborious.

Gad, A. G., Y. M. Fayez, K. M. Kelani, and A. M. Mahmoud, "TLC-smartphone in antibiotics determination and low-quality pharmaceuticals detection.", RSC advances, vol. 11, issue 31, pp. 19196-19202, 2021. Abstract

Thin layer chromatography (TLC) is a powerful and simple technique for screening and quantifying low quality and counterfeit pharmaceutical products. The detection methods used to detect and quantify separate analytes in TLC ranges from the densitometric method to mass spectrometric or Raman spectroscopic methods. This work describes the development and optimization of a simple and sensitive TLC method utilizing a smartphone CCD camera for verification of both identity and quantity of antibiotics in dosage form, namely ofloxacin and ornidazole. Mixtures of ofloxacin and ornidazole were chromatographed on a silica gel 60 F plate as a stationary phase. The optimized mobile phase is -butanol : methanol : ammonia (8 : 1 : 1.5 by volume). Iodine vapor has been used as a "universal stain" to visualize the spots on the TLC plates in order to obtain a visual image using the smartphone camera and a desk lamp as an illumination source, thus eliminating the need for a UV illumination source. The recorded images were processed to calculate the values ( values for ofloxacin and ornidazole were 0.12 and 0.76, respectively) which provide identity of the drugs while spot intensity was calculated using a commercially available smartphone app and employed for quantitative analysis of the antibiotics and "acetaminophen" as an example of a counterfeit substance. The smartphone TLC method yielded a linearity of ofloxacin and ornidazole in the range of 12.5-62.5 μg/band and 500-1000 μg/band, respectively. The limit of detection was found to be 1.6 μg/spot for ofloxacin and 97.8 μg/spot for ornidazole. The proposed method was compared with the bench top densitometric method for verification using a Camag TLC Scanner 3, the spot areas were scanned at 320 nm. The value of ofloxacin and ornidazole was calculated to be 0.12 and 0.76, respectively. The densitometric method yielded a linearity of ofloxacin and ornidazole in the range of 5-40 μg/band and 5-50 μg/band, respectively. The limit of detection was found to be 0.8 μg/spot for ofloxacin and 1.1 μg/spot for ornidazole. The proposed method has been successfully applied for the determination of ofloxacin and ornidazole present in more than one pharmaceutical dosage form and was comparable to the densitometric method.

2019
Abd El-Rahman, M. K., G. Mazzone, A. M. Mahmoud, E. Sicilia, and T. Shoeib, "Spectrophotometric determination of choline in pharmaceutical formulations via host-guest complexation with a biomimetic calixarene receptor", Microchemical Journal, vol. 146, pp. 735-741, 2019.
2018
Mousavi, M. P., M. K. Abd El-Rahman, A. M. Mahmoud, R. M. Abdelsalam, and P. Buhlmann, "In Situ Sensing of the Neurotransmitter Acetylcholine in a Dynamic Range of 1 nM to 1 mM", ACS Sensors, vol. 3, issue 12, pp. 2581–2589, 2018.
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