A magnetic nanoparticles-zinc oxide/zinc hexacyanoferrate hybrid film for amperometric determination of tyrosine

Carbon Inks-Based Screen-Printed Electrodes for Qualitative Analysis of Amino Acids

Due to the great significance of amino acids, a substantial number of research studies has been directed toward the development of effective and reliable platforms for their evaluation, detection, and identification. In order to support these studies, a new electrochemical platform based on PANI/ZnO nanowires' modified carbon inks screen-printed electrodes was developed for qualitative analysis of electroactive amino acids, with emphasis on tyrosine (Tyr) and tryptophan (Trp). A comparative investigation of the carbon ink before and after modification with the PANI/ZnO was performed by scanning electron microscopy and by Raman spectroscopy, confirming the presence of PANI and ZnO nanowires. Electrochemical investigations by cyclic voltammetry and electrochemical impedance spectroscopy have shown a higher charge-transfer rate constant, which is reflected into lower charge-transfer resistance and higher capacitance values for the PANI/ZnO modified ink when compared to the simple carbon screen-printed electrode. In order to demonstrate the electrochemical performances of the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes for amino acids analysis, differential pulse voltammograms were obtained in individual and mixed solutions of electroactive amino acids. It has been shown that the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes allowed for tyrosine and tryptophan a peak separation of more than 100 mV, enabling their screening and identification in mixed solutions, which is essential for the electrochemical analysis of proteins within the proteomics research field.

Enzyme-based sensing on nanohybrid film coated over FTO electrode for highly sensitive detection of antibiotics

Cefepime and Meropenem are the new class of antibiotics, which are particularly used as last potent defender or the antibiotics of the last resort against multi-resistant bacterial species. In this paper, an impedance-based electrochemical biosensor was fabricated for identifying antibiotics of last resort in the forensic samples including gastric lavage and other body fluids. The sensor was developed using platinum nanoparticles (PtNPs) and electrodeposited zinc oxide- zinc hexacyanoferrate hybrid film (ZnO/ZnHCF) on the surface of a fluorine-doped glass electrode (FTO). Further, penicillinase was immobilized onto the modified electrode using penicillinase enzyme. The developed biosensor exhibits a good analytical response for the detection of antibiotics evaluated using electrochemistry studies. The linear response of the fabricated electrode was observed from 0.1 to 750 µM and the electrode limit of detection (LOD) was observed as 0.1 µM. The sensor confirms good accuracy, is highly selective, and sensitive for the target. While storing the modified electrode at 4 °C, the stability of biosensor was evaluated for 45 days, and activity loss of 30-40% was observed. The highly sensitive interface of Penicillinase@CHIT/PtNP-ZnO/ZnHCF/FTO electrode shows a promising future in forensic studies.

Detection of Phenylketonuria Markers Using a ZIF-67 Encapsulated PtPd Alloy Nanoparticle (PtPd@ZIF-67)-Based Disposable Electrochemical Microsensor

Phenylketonuria (PKU) is a common disease in congenital disorder of amino acid metabolism, which can lead to intellectual disability, seizures, behavioral problems, and mental disorders. We report herein a facile method to screen for PKU by the measurements of its metabolites (markers). In this work, a disposable electrochemical microsensor modified with a ZIF (zeolitic imidazolate framework)-based nanocomposite is constructed, in which ZIF-67 crystals are encapsulated with PtPd alloy nanoparticles (NPs) forming the nanocomposite (PtPd@ZIF-67). According to electrochemical measurements, the PtPd@ZIF-67-modified microsensor shows good responses and selectivity to phenylpyruvic acid and phenylacetic acid, while almost no response toward other amino acid analogues is observed. Here, a new sensing mechanism based on the acylation reaction between the imidazole linker in ZIF-67 and carboxyl in PKU markers has been proposed and verified through the Fourier-transform infrared spectroscopy study. Moreover, the encapsulated PtPd NPs elevate the electron transfer capability of the PtPd@ZIF-67-modified microsensor and further improve the electrochemical sensing performance. Finally, we demonstrate that the developed PtPd@ZIF-67-modified microsensor has the possibility to sensing of PKU markers with high response and good specificity and may be extended to exploit the point-of-care rapid PKU screening.