1. Electrochemical Impedance Spectroscopy Microsensor Based on Molecularly Imprinted Chitosan Film Grafted on a 4-Aminophenylacetic Acid (CMA) Modified Gold Electrode, for the Sensitive Detection of Glyphosate
Fares Zouaoui, Saliha Bourouina-Bacha, Mustapha Bourouina, Albert Alcacer, Joan Bausells, Nicole Jaffrezic-Renault, Nadia Zine, Abdelhamid Errachid Front Chem. 2021 May 7;9:621057. doi: 10.3389/fchem.2021.621057. eCollection 2021.
A novel electrochemical impedance spectroscopy (EIS) microsensor was implemented for the dosage of traces of glyphosate, in real and synthetic water samples. Molecularly imprinted chitosan was covalently immobilized on the surface of the microelectrode previously modified with 4-aminophenylacetic acid (CMA). The characterization of the resulting microelectrodes was carried out by using cyclic voltammetry measurement (CV), scanning electron microscopy (SEM), and electrochemical impedance spectrometry (EIS). EIS responses of the CS-MIPs/CMA/Au microsensor toward GLY was well-proportional to the concentration in the range from 0.31 × 10-9 to 50 × 10-6 mg/mL indicating a good correlation. The detection limit of GLY was 1 fg/mL (S/N = 3). Moreover, this microsensor showed good reproducibility and repeatability, high selectivity, and can be used for the detection of GLY in river water.
2. A vibrational spectroscopy study on 3-aminophenylacetic acid by DFT calculations
Yasemin Akkaya, Kubilay Balci, Yeliz Goren, Sevim Akyuz Spectrochim Acta A Mol Biomol Spectrosc. 2015 Aug 5;147:303-15. doi: 10.1016/j.saa.2015.03.094. Epub 2015 Mar 31.
In this study, in which the group vibrations of 3-aminophenylacetic acid were investigated by electronic structure calculations based on Density Functional Theory (DFT), the possible stable conformers of the molecule were searched through a relaxed "potential energy surface scan" carried out at B3LYP/6-31G(d) level of theory. The corresponding equilibrium geometrical and vibrational spectral data for each of the determined stable conformers and for their possible dimer structures were obtained through "geometry optimisation" and "frequency" calculations carried out at B3LYP/6-31G(d) and B3LYP/6-311G++(d,p) levels of theory. The obtained results confirmed that anharmonic wavenumbers calculated at B3LYP/6-311G++(d,p) level generally quite well agree with the experimental wavenumbers, however, harmonic wavenumbers calculated at both levels of theory need an efficient refinement for a satisfactory agreement with experiment. In particular, the harmonic wavenumbers, IR and Raman intensities refined within Scaled Quantum Mechanical Force Field (SQM FF) methodology constituted the primary data set in the interpretation of the experimental FT-IR, FT-Raman and dispersive Raman spectra of 3-aminophenylacetic acid. By the help of these refined spectral data, the effects of conformation and intermolecular hydrogen bonding on the fundamental bands observed in the experimental spectra could be correctly predicted.
3. Impedimetric immunosensor for dengue diagnosis using graphite screen-printed electrodes coated with poly(4-aminophenylacetic acid)
Thiago Coimbra Pimenta, Cátia da Cruz Santos, Ronaldo Luís Thomasini, Lucas Franco Ferreira Biomed Microdevices. 2018 Sep 4;20(3):78. doi: 10.1007/s10544-018-0324-2.
Dengue is an infectious viral disease transmitted by the Aedes aegypti mosquito, the control of which is complex. In addition, the clinical diagnosis is difficult to perform since it resembles other febrile infections; thus, the development of more effective methods to detect dengue virus (DV) has drawn increasing attention. The present study aimed to develop an impedimetric immunosensor for dengue diagnosis using a screen-printed electrode (SPE) functionalized with polymer films derived from 4-aminophenylacetic acid (4-APA). Data obtained from scanning electron microscopy (SEM) showed the deposition of a uniformly distributed material over the electrode surface. The immunosensor was based on the specific interaction between dengue antigen, NS1 protein, and anti-NS1 antibodies, IgG and IgM. In a characterization study using cyclic voltammetry (CV), the polymer film showed two oxidation peaks at +0.17 and + 0.35 V in 0.50 M sulfuric acid solution, indicating its adsorption and electroactivity at the SPE surface. Electrochemical impedance spectroscopy (EIS) measurements showed a higher charge transfer resistance (Rct) to the polymer film-modified SPE as compared with the bare SPE, corroborating a previous study. The best rNS1 concentration for immobilization was 1.00 ng/mL, and the immunoreaction time between the antigen (Ag) and the antibody (Ab) was 20 min. Dilutions of positive and negative clinical serum samples were evaluated by EIE, from which it was possible to elucidate, for the positive serum, that the more diluted the serum the greater the Rct. Negative serum also showed an analytical signal, probably due to the presence of non-specific antibodies; however, the generated signal presented values closer to the rNS1 signal, indicating good selectivity of the proposed platform. The experiments were repeated using bare SPE to verify the importance of the polymer film in biosensor construction. No significant difference was observed between these results. Graphical abstract Proposed schematic for the genosensor development.
