Determination of epigallocatechin-3-gallate with a high-efficiency electrochemical sensor based on a molecularly imprinted poly(o-phenylenediamine) film

Novel Electrochemical Sensing of Catechins in Raw Green Tea Extract via a Trimetallic Zeolitic Imidazolate Fibrous Framework

Human health-related issues are increasing in day to day life because of the modern and unhygienic food lifestyles. In recent times, green tea (GT) gains more attention due to its numerous health benefits. It contains more biologically active compounds that improve mental health, increase metabolism, reduce cancer risks, and serve as an anti-aging agent for the brain. As it is globally consumed, the evaluation of the compounds present in it is very important. Hence, an attempt has been performed to evaluate these components in GT by using a cobalt nickel iron-based trimetallic zeolitic imidazolate framework as microfibers (CoNiFe-ZIF-MFs) synthesized via an electrospinning technique. Interestingly, the synthesized CoNiFe-ZIF-MFs catalyst simultaneously detects three major catechin (CT) groups, namely, epigallocatechin-3-gallate (EGCG), epicatechin (EC), and epicatechingallate (ECG). Further, the square wave voltammetry findings showed that there is a wide linear range of 50 ng to 1 mg for all the three CTs with LODs 45, 8, and 4 ng for EGCG, EC, and ECG, respectively. These results confirm the excellent sensing behavior of the composite toward GT extracts, proposing its practical utility in real-time compound analysis in food sectors. Other results like stability and reproducibility also promote its usage in the biomedical field. This study mainly focuses on the direct sensing of CTs present in GT without spiking any commercially purchased sample, and the sensing was performed simultaneously for all the three analytes; thus, this work gains novelty from the existing ones.

One-pot green preparation of deep-ultraviolet and dual-emission carbon nanodots for dual-channel ratiometric determination of polyphenol in tea sample

A novel deep-ultraviolet and dual-emission carbon nanodots (DUCDs)-based dual-channel ratiometric probe was prepared by a one-pot environmental-friendly hydrothermal process using guanidine as the only starting material for sensing polyphenol in tea sample (TPPs). Under the exposure to TPPs, the DUCDs not only provided a characteristic colorimetric response to TPPs, but also displayed TPPs-sensitive ratiometric fluorescence quenching. The detection mechanism was proved to be that enrichment-specific hydroxyl sites (e.g., -NH₂ and -COOH) of DUCDs can specifically react with phenolic hydroxyl groups of TPPs to generate dynamic amide and carboxylate bonds by dehydration and/or condensation reaction. As a result, a new carbon nanomaterial with decrement of surface passivation groups, inherent light-absorbing, and invalid fluorescence emission was generated. The ratio (FL_297nm/FL_395nm) of fluorescence intensity at 297 nm and 395 nm of DUCDs excited at 275 nm decreased with increasing TPPs concentration. The linearity range was 5.0 ng/mL to 100 µg/mL with a detection limit (DL) of 3.5 ± 0.04 ng/mL for TPPs (n = 3, 3σ/k). Colorimetry of DUCDs, best measured as absorbance at 320 nm, was increased linearly in the TPP concentration range 200 ng/mL-200 µg/mL with a DL of 94.7 ± 0.04 ng/mL (n = 3, 3σ/k). The probe was successfully applied to the determination of TPPs in real tea samples, showing potential application prospects in food analysis.

Electrochemical Sensors and Biosensors for the Analysis of Tea Components: A Bibliometric Review

Tea is a popular beverage all around the world. Tea composition, quality monitoring, and tea identification have all been the subject of extensive research due to concerns about the nutritional value and safety of tea intake. In the last 2 decades, research into tea employing electrochemical biosensing technologies has received a lot of interest. Despite the fact that electrochemical biosensing is not yet the most widely utilized approach for tea analysis, it has emerged as a promising technology due to its high sensitivity, speed, and low cost. Through bibliometric analysis, we give a systematic survey of the literature on electrochemical analysis of tea from 1994 to 2021 in this study. Electrochemical analysis in the study of tea can be split into three distinct stages, according to the bibliometric analysis. After chromatographic separation of materials, electrochemical techniques were initially used only as a detection tool. Many key components of tea, including as tea polyphenols, gallic acid, caffeic acid, and others, have electrochemical activity, and their electrochemical behavior is being investigated. High-performance electrochemical sensors have steadily become a hot research issue as materials science, particularly nanomaterials, and has progressed. This review not only highlights these processes, but also analyzes and contrasts the relevant literature. This evaluation also provides future views in this area based on the bibliometric findings.

Molecularly Imprinted Electrochemical Sensors: Analytical and Pharmaceutical Applications Based on Ortho-Phenylenediamine Polymerization

Background:

The molecular imprinting technique has been applied in many fields including separation, artificial antibody mimics, catalysis, sensing studies, and drug delivery. The reasons for the popularity of this technique among the researchers are high selectivity due to the cavities that are formed on the polymer surface for the specific analyte, high robustness, high durability under extreme conditions and low cost. When these advantages are combined with the advantages of electrochemical methods such as rapid response time, ease of use, cheapness and miniaturizability, Molecularly Imprinted Polymer (MIP) based electrochemical sensors turn out to be a widely-preferred sensing tool.

Objective:

This article provides the reader with information on MIP-based electrochemical sensors and reviews the applications of the MIP sensors prepared by electropolymerization of orthophenylenediamine, a monomer whose mechanical and chemical stability is very high.

Results and Conclusion:

The literature survey summarized in this review shows that cyclic voltammetry is the most widely preferred electrochemical technique for electropolymerization of o-PD. The media chosen is generally acetate or phosphate buffers with different pH values. Although there are numerous solvents used for template removal, generally methanol and NaOH have been chosen.

Novel electrochemical sensor based on molecularly imprinted polymer for selective recognition of sesquiterpene β-caryophyllene

Molecularly imprinted polymers provide an excellent platform for the modification of selective electrodes for sensing applications. Herein, we present a novel modified carbon paste electrode (CPE) with a selective molecularly imprinted polymer (MIP) for recognition of sesquiterpene β-caryophyllene, constituted of important plants oil-resins and extracts. The non-covalent MIP was synthesized using AA, EGDMA, and AIBN as a functional monomer, cross-linker and initiator agent, respectively. Structural and chemical characterization of the synthesized MIP was conducted through scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). It was possible to verify the functional features of the synthesized MIP related to the extraction process of the template molecule. The CPE modified with MIP for sesquiterpene β-caryophyllene recognition was characterized by electrochemical techniques as cyclic voltammetry (CV) and square wave voltammetry (SWV). The highest selective recognition electrode enables to detect concentrations in the range between 1.5 × 10^-7 and 7.5 × 10^-7 M, showing great potential for applications in monitoring content of sesquiterpene β-caryophyllene in technological processes and for predicting the quality of extracts, oils, and resins of plants.

Electrochemical aptasensor for mucin 1 based on dual signal amplification of poly(o-phenylenediamine) carrier and functionalized carbon nanotubes tracing tag

Mucin 1 (MUC 1), as a most studied mucin, has become a useful marker for identifying breast cancer in the early stages. In this work, a novel method for the determination of MUC 1 in serum was developed based on a sandwich-type electrochemical aptasensor, which combined a dual signal amplification strategy of poly(o-phenylenediamine)-Au nanoparticles (PoPD-AuNPs) hybrid film as carrier and AuNPs functionalized silica/multiwalled carbon nanotubes core-shell nanocomposites (AuNPs/SiO2@MWCNTs) as tracing tag. The PoPD-AuNPs film provides a suitable microenvironment for stabilizing the primary aptamer (Apt) assembly, and the AuNPs/SiO2@MWCNTs enhances the surface area for immobilizing abundant secondary Apts as well as load large amounts of electrochemical probe thionine (Thi). In the presence of MUC 1, the sandwich-type recognition reacted on the aptasensor surface, and the Thi-AuNPs/SiO2@MWCNTs nanoprobes were captured onto the electrode surface to form biocomplex. AuNPs and MWCNTs could facilitate the electron transfer from Thi to the electrode, thus amplifying the detection response. Under the optimized experimental conditions, the proposed sensing strategy provided a wider linear dynamic range over three orders of magnitude with the detection limit down to 1 pM. Moreover, the aptasensor demonstrated good precision, acceptable stability and reproducibility.