Electropolymerization mechanisms of hydroxyphenylacetic acid isomers

Surface chemistry applications and development of immunosensors using electrochemical impedance spectroscopy: A comprehensive review

Immunosensors are promising alternatives as detection platforms for the current gold standards methods. Electrochemical immunosensors have already proven their capability for the sensitive, selective, detection of target biomarkers specific to COVID-19, varying cancers or Alzheimer's disease, etc. Among the electrochemical techniques, electrochemical impedance spectroscopy (EIS) is a highly sensitive technique which examines the impedance of an electrochemical cell over a range of frequencies. There are several important critical requirements for the construction of successful impedimetric immunosensor. The applied surface chemistry and immobilisation protocol have impact on the electroanalytical performance of the developed immunosensors. In this Review, we summarise the building blocks of immunosensors based on EIS, including self-assembly monolayers, nanomaterials, polymers, immobilisation protocols and antibody orientation.

Sustainable Electropolymerization of Zingerone and Its C2 Symmetric Dimer for Amperometric Biosensor Films

Polymeric permselective films are frequently used for amperometric biosensors to prevent electroactive interference present in the target matrix. Phenylenediamines are the most commonly used for the deposition of shielding polymeric films against interfering species; however, even phenolic monomers have been utilized in the creation of these films for microsensors and biosensors. The purpose of this paper is to evaluate the performances of electrosynthesized polymers, layered by means of constant potential amperometry (CPA), of naturally occurring compound zingerone (ZING) and its dimer dehydrozingerone (ZING DIM), which was obtained by straight oxidative coupling reaction. The polymers showed interesting shielding characteristics against the main interfering species, such as ascorbic acid (AA): actually, polyZING exhibited an AA shielding aptitude comprised between 77.6 and 99.6%, comparable to that obtained with PPD. Moreover, a marked capability of increased monitoring of hydrogen peroxide (HP), when data were compared with bare metal results, was observed. In particular, polyZING showed increases ranging between 55.6 and 85.6%. In the present work, the molecular structures of the obtained polymers have been theorized and docking analyses were performed to understand their peculiar characteristics better. The structures were docked using the Lamarckian genetic algorithm (LGA). Glutamate biosensors based on those polymers were built, and their performances were compared with biosensors based on PPD, which is the most widespread polymer for the construction of amperometric biosensors.

Recent trends in degradation strategies of PFOA/PFOS substitutes

The global elimination and restriction of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), respectively, have urged manufacturers to shift production to their substitutes which still pose threat to the environment with their bioaccumulation, toxicity and migration issues. In this context, efficient technologies and systematic mechanistic studies on the degradation of PFOA/PFOS substitutes are highly desirable. In this review, we summarize the progress in degrading PFOA/PFOS substitutes, including four kinds of mainstream methods. The pros and cons of the present technologies are analyzed, which renders the discussion of future prospects on rational optimizations. Additional discussion is made on the differences in the degradation of various kinds of substitutes, which is compared to the PFOA/PFOS and derives designing principles for more degradable F-containing compounds.

Poly(sulfosalicylic acid)-functionalized gold nanoparticles for the detection of tetrabromobisphenol A at pM concentrations

Developing a sensitive, simple and fast sensing system for 3,3',5,5'-tetrabromobisphenol A (TBBPA) is important because of its ubiquitousness and high toxicity. In this work, a gold nanoparticles (AuNPs) and poly(sulfosalicylic acid) (PSSA) composite film (AuNPs-PSSA) is fabricated in-situ on an electrode surface via cyclic voltammetry scanning. The characterization via scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray (EDX) analysis and Fourier transform infrared (FTIR) spectroscopy indicate that the PSSA film is homogeneously decorated with AuNPs, and a highly uniform and thin composite film is obtained. Electrochemical tests reveal that the AuNPs-PSSA film exhibits larger active surface area, lower charge transfer resistance and higher accumulation efficiency toward TBBPA than single AuNPs and PSSA film. As a result, the oxidation signals and sensing sensitivity of TBBPA are significantly enhanced on the surface of the AuNPs-PSSA. The developed TBBPA sensing platform using AuNPs-PSSA composite film, with low detection limit (25 pM) and wide linear range (0.1-10 nM), is successfully utilized to measure TBBPA level in wastewater samples. The results are highly consistent with those that obtained from high-performance liquid chromatography. The preparation and reusability of the TBBPA sensor can be automatically achieved through CV scanning, providing a promising on-line monitoring system for wastewater samples.

Optimization and Application of Electrochemical Transducer for Detection of Specific Oligonucleotide Sequence for Mycobacterium tuberculosis

In this study, the electropolymerization of 4-hydroxyphenylacetic acid (4-HPA) over graphite electrodes (GE) was optimized, aiming its application as a functionalized electrochemical platform for oligonucleotides immobilization. It was investigated for the number of potential cycles and the scan rate influence on the monomer electropolymerization by using cyclic voltammetry technique. It was observed that the polymeric film showed a redox response in the region of +0.53/+0.38 V and the increase in the number of cycles produces more electroactive platforms because of the better electrode coverage. On the other hand, the decrease of scan rate produces more electroactive platforms because of the occurrence of more organized coupling. Scanning electron microscopy (SEM) images showed that the number of potential cycles influences the coverage and morphology of the electrodeposited polymeric film. However, the images also showed that at different scan rates a more organized material was produced. The influence of these optimized polymerization parameters was evaluated both in the immobilization of specific oligonucleotides and in the detection of hybridization with complementary target. Poly(4-HPA)/GE platform has shown efficient and sensitive for oligonucleotides immobilization, as well as for a hybridization event with the complementary oligonucleotide in all investigated cases. The electrode was modified with 100 cycles at 75 mV/s presented the best responses in function of the amplitude at the monitored peak current values for the Methylene Blue and Ethidium Bromide intercalators. The construction of the genosensor to detect a specific oligonucleotide sequence for the Mycobacterium tuberculosis bacillus confirmed the results regarding the poly(4-HPA)/GE platform efficiency since it showed excellent sensitivity. The limit of detection and the limit of quantification was found to be 0.56 (±0.05) μM and 8.6 (±0.7) μM, respectively operating with very low solution volumes (15 µL of probe and 10 µL target). The biosensor development was possible with optimization of the probe adsorption parameters and target hybridization, which led to an improvement in the decrease of the Methylene Blue (MB) reduction signal from 14% to 34%. In addition, interference studies showed that the genosensor has satisfactory selectivity since the hybridization with a non-specific probe resulted in a signal decrease (46% lower) when compared to the specific target.

Simultaneous measurement and quantitation of 4-hydroxyphenylacetic acid and dopamine with fast-scan cyclic voltammetry

Caged compounds have been used extensively to investigate neuronal function in a variety of preparations, including cell culture, ex vivo tissue samples, and in vivo. As a first step toward electrochemically measuring the extent of caged compound photoactivation while also measuring the release of the catecholamine neurotransmitter, dopamine, fast-scan cyclic voltammetry at carbon-fiber microelectrodes (FSCV) was used to electrochemically characterize 4-hydroxyphenylacetic acid (4HPAA) in the absence and presence of dopamine. 4HPAA is a by-product formed during the process of photoactivation of p-hydroxyphenacyl-based caged compounds, such as p-hydroxyphenylglutamate (pHP-Glu). Our data suggest that the oxidation of 4HPAA occurs through the formation of a conjugated species. Moreover, we found that a triangular waveform of -0.4 V to +1.3 V to -0.4 V at 600 V s(-1), repeated every 100 ms, provided an oxidation current of 4HPAA that was enhanced with a limit of detection of 100 nM, while also allowing the detection and quantitation of dopamine within the same scan. Along with quantifying 4HPAA in biological preparations, the results from this work will allow the electrochemical measurement of photoactivation reactions that generate 4HPAA as a by-product as well as provide a framework for measuring the photorelease of electroactive by-products from caged compounds that incorporate other chromophores.