Fabrication of magnetic iridium nanocomposites for the detection of selective serotonin re-uptake inhibitors
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Date
2024
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University of the Western Cape
Abstract
Depression is a common and widespread mental disorder affecting millions of people worldwide. It has become the leading cause of disability and has been listed as the third largest cause of disease burden since 2008 and is expected to rank the first by 2030. Selective serotonin re-uptake inhibitors (SSRIs) are one of the most prescribed classes of antidepressants used for the treatment of moderate to severe depressive disorder, personality disorders and various phobias. This class of antidepressants was created with improved margins of safety. However, genetic polymorphism may be responsible for the high variability in patients’ responses to treatment, ranging from failure to delayed therapeutic responses to severe adverse effects of treatment. It is crucial that the appropriate amount of SSRI drugs is administered to ensure the optimum therapeutic efficacy and intervention to minimise severe and toxic effects in patients, which may be the result of accidental and deliberate cases of poisoning. Determining SSRI concentration in human fluids and the environment with high sensitivity, specificity, and reproducibility, increased usage, and reduced fouling effects and at a low cost and real-time monitoring, is imperative. A comprehensive study of the development of a novel electrochemical sensor based on iridium-gold nanocomposite (IrAuNPs) modified electrodes for the detection and quantification of antidepressants, paroxetine (PRX) and citalopram (CIT) was conducted. The sensing platform based on a glassy carbon electrode (GCE) was modified by drop casted iridium-gold nanocomposites (IrAuNPs), which allowed for enhanced conductivity. Iridium-gold nanocomposites (IrAuNPs) along with its counterpart’s iridium nanoparticles (IrNPs) and gold nanoparticles (AuNPs) were synthesized from coffee waste extract via complete green chemistry. The synthesized nanoparticles and nanocomposites were characterised for their optical properties, size, polydispersity, stability, morphology, crystallinity, and active functional groups using ultraviolet-visible (UV-Vis) spectroscopy, dynamic light scattering (DLS) analysis, high resolution transmission electron microscopy (HRTEM), high resolution scanning electron microscopy (HRSEM), X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The electrochemical properties of IrNPs, AuNPs and IrAuNPs were determined using cyclic voltammetry (CV) and square wave voltammetry (SWV). In this study the results showed that the extract of the coffee waste was capable of reducing iridium (II) chloride and gold (III) chloride to form IrNPs and AuNPs respectively as well as the bimetallic, IrAuNPs. Mostly near-spherical to spherical nanoparticles, with core sizes ranging from 2.02 nm to 13.27 nm were synthesized. Electrochemical studies revealed an irreversible behaviour for IrNPs with quasi-reversibility for AuNPs and IrAuNPs with great stability with the increase in scan rate. The surface concentration of IrNPs was calculated to be 1.02x10-9 mol.cm2, while the surface concentration of AuNPs was 7.72x10-10 mol.cm2 and IrAuNPs had an increased in the surface concentration of 2,34x10-9 mol.cm2. These electrochemical parameters revealed that the iridium gold nanocomposite (IrAuNPs) can be a good candidate for the sensor application, and thus was used to detect antidepressants, citalopram, and paroxetine. The electrochemical sensor could determine paroxetine and citalopram in the concentration range of 20 nM to 200 nM and 1 μM to 10 μM with limits of detection (LOD) of 0.072 nM and 0.085 μM respectively. Paroxetine and citalopram were spiked in 20 % synthetic urine and were found to be in higher concentration ranges of 2 μM to 20 μM and 10 μM to 55 μM with a higher LOD of 1.168 μM and 5.669 μM for paroxetine and citalopram respectively. This increase is due to the interfering compounds found in the synthetic urine. The sensor showed a recovery percentage of 90 – 115.1 % for paroxetine 86 – 113.1 % for citalopram. The proposed sensor showed good precision, and accuracy with excellent sensitivity and selectivity of drug identification in a rapid analysis time, which is crucial in applications of biological matrices. This study was thus successful in fabricating an electrochemical sensor for the detection of paroxetine and citalopram in phosphate buffer solution and synthetic urine.
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Keywords
Green Nanotechnology, Iridium nanoparticles, Gold nanoparticles, Iridium-gold nanocomposites, Waste management