Browsing by Author "Muhammad Ahmad"

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An Array-based Photolithographically Patterned Electrochemical Sensing Platform for Highly Sensitive Determination of Uric Acid, Dopamine, l-Tryptophan, and Pyridoxine in Biological Samples
(Springer Nature, 2024) Ankit Kumar Singh; Shreanshi Agrahari; Shivani Shukla; Ida Tiwari; Muhammad Ahmad; S. Ravi P. Silva
Biomolecules play important roles in physiological functions and pharmacological characteristics of human body. Uric acid (UA) is the end product of purine. Dopamine (DA) is a neurotransmitter of catecholamine group. l-tryptophan is an essential amino acid that can be metabolized to neuroactive substances. Pyridoxine is a water-soluble vitamin playing an important role in nervous system. The abnormalities in their concentration levels led to a wide range of significant mental and physical illnesses. Thus, electrochemical analysis of these analytes on an array system would be beneficial from clinical or scientific points of view. This work was aimed at the development of practical sensor array for determination of multiple analytes on a single sensing platform using individually addressable microelectrodes. The occurrence of adsorption–desorption phenomenon on the surface of palladium microelectrode array (Pd MEA) printed on the silicon wafer through photolithography was exploited for electro-oxidation of UA, DA, l-tryptophan and pyridoxine. The sensing of electroactive UA was done using carbon nanotubes(CNTs) grown Pd MEA as a working electrode, while selectivity for other analytes was achieved by the modification of CNTs/Pd MEA through electrodeposition of poly(l-lysine) (poly(l-lysine)/CNTs/Pd MEA) for DA sensing, poly(l-arginine) (poly(l-arginine)/CNTs/Pd MEA) for l-tryptophan sensing and reduced graphene oxide (rGO/CNTs/Pd MEA) for pyridoxine sensing. The electrochemical differential pulse voltammetry (DPV) analyses reveal excellent linearity in the concentration ranges of 50–6000 µmol/L, 2–8000 µmol/L, 20–15,000 µmol/L, and 10–5000 µmol/L with detection limits of 15.0, 0.5, 10.0, and 1.0 µmol/L for UA, DA, l-tryptophan, and pyridoxine, respectively. The proposed multiple analytes sensor has shown very high sensitivities of 140, 9580, 2280, and 940 µA·(µmol·L−1)−1·cm−2 for UA, DA, l-tryptophan, and pyridoxine sensing, respectively. Further, accuracy and reliability of the fabricated sensor were also tested in real samples. © The Nonferrous Metals Society of China 2024.
Electrochemical biosensors based on in situ grown carbon nanotubes on gold microelectrode array fabricated on glass substrate for glucose determination
(Springer, 2023) Ankit Kumar Singh; Nandita Jaiswal; Ida Tiwari; Muhammad Ahmad; S. Ravi P. Silva
A highly sensitive electrochemical sensor is reported for glucose detection using carbon nanotubes grown in situ at low temperatures on photolithographically defined gold microelectrode arrays printed on a glass substrate (CNTs/Au MEA). One of the main advantages of the present design is its potential to monitor 64 samples individually for the detection of glucose. The selectivity of the fabricated MEA towards glucose detection is achieved via modification of CNTs/Au MEA by immobilizing glucose oxidase (GOx) enzyme in the matrix of poly (paraphenylenediamine) (GOx/poly (p-PDA)/CNTs/Au MEA). The electrocatalytic and electrochemical responses of the proposed sensing platform towards glucose determination were examined via cyclic voltammetry and electrochemical impedance spectroscopy. The developed impedimetric biosensor exhibits a good linear response towards glucose detection, i.e., 0.2–27.5 µM concentration range with sensitivity and detection limits of 168.03 kΩ−1 M−1 and 0.2 ± 0.0014 μM, respectively. The proposed glucose biosensor shows excellent reproducibility, good anti-interference property, and was successfully tested in blood serum samples. Further, the applicability of the proposed sensor was successfully validated through HPLC. These results supported the viability of using such devices for the simultaneous detection of multiple electroactive biomolecules of physiological relevance. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s).