Článek si všímá posledních prezentovaných prací s problematikou elektrochemické detekce insulinu a předkládá kritický pohled na výzkum a vývoj jeho elektrochemických neenzymových senzorů. Monitoruje vliv experimentálních podmínek na insulinový oxidační signál a zamýšlí se nad katalytickými efekty nanočástic či nanokompozitů deponovaných na površích elektrochemického snímače.
The article notes the latest presented work on the electrochemical detection of insulin and presents a critical view of the research and development of its electrochemical non-enzymatic sensors. It monitors the effect of experimental conditions on the insulin oxidation signal and considers the catalytic effects of nanoparticles or nanocomposites deposited on the surfaces of the electrochemical sensor.
In this paper, the d(GCGAAGC) heptamer and the closely related d(GCGAGC) hexamer are examined via electrochemical (cyclic voltammetry) and spectroscopic (circular dichroism) methods. Dramatic changes in the CD spectroscopic and CV electrochemical properties, induced by the loss of only one single nucleotide (A), are detected. The CD spectra and native polyacrylamide gel electrophoresis (PAGE) confirmed structural changes taking place in the relevant chain-like oligodeoxynucleotide assemblies. Dedicated studies suggest that the heptamer (Hp) possesses a hairpin structure, whereas the hexamer (Hx) appears to be rather a duplex. Both of the structures exhibited completely different adsorption behavior at the hanging mercury drop electrode, and this factor was readily confirmed by means of elimination voltammetry with linear scan (EVLS). We established that the Hp hairpin (~-1300 mV), compared to the Hx duplex (~-1360 mV), is the thermodynamically favored electron acceptor. The adsorption isotherms were constructed based on the voltammetric peak height values, reflecting the reduction of the adenine (A) and cytosine (C) moieties as well as the oxidation of the 7,8-dihydroguanine (7,8-DHG) moieties. Finally, as revealed by the spectroscopic and electrochemical results, Hx forms a bimolecular antiparallel homo-duplex carrying both Watson-Crick base pairs (CG or GC) and mismatched edge-to-edge base pairs (GA or AG).
Diabetes mellitus can be considered one of the most widespread diseases globally. Hence, the diabetes research is currently focused on developing an effective, low-cost sensor having high stability and suitable analytical characteristics. Screen printed carbon electrodes (SPCEs) embody ideal candidates for insulin determination due to the small area of the working electrode eliminating the solution volume required for the given purpose. Modification of SPCEs by using nanoparticles resulted in an increase of the working electrode surface area and formation of a higher number of active species. The aim of this paper is to examine the impact of a chitosan membrane on the electrochemical determination of insulin on NiO nanoparticles (NiONPs) and multi-walled nanotube (MWCNTs) modified SPCE (NiONPs/MWCNTs/SPCE). This study is primarily conceived to compare the analytical characteristics and stability of NiONPs/chitosan-MWCNTs/SPCE and NiONPs/MWCNTs/SPCE. An electrode modified with chitosan displays a wider linear range, one of 0.25 μM - 5 μM (R2 0.997); a lower limit of detection, 94 nM; a high sensitivity (0.021 μA/μM) and better stability than that of an electrode without chitosan. According to these characteristics, the polymer is considered a necessary compound of the electrochemical insulin sensor, improving the sensor's analytical characteristics.
- MeSH
- Biosensing Techniques instrumentation MeSH
- Chitosan chemistry MeSH
- Electrochemical Techniques instrumentation MeSH
- Electrodes MeSH
- Insulin analysis MeSH
- Humans MeSH
- Limit of Detection MeSH
- Membranes, Artificial * MeSH
- Nanoparticles chemistry MeSH
- Nanotubes, Carbon chemistry MeSH
- Nickel chemistry MeSH
- Recombinant Proteins analysis MeSH
- Carbon chemistry MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
We review the progress achieved during the recent five years in immunochemical biosensors (immunosensors) combined with nanoparticles for enhanced sensitivity. The initial part introduces antibodies as classic recognition elements. The optical sensing part describes fluorescent, luminescent, and surface plasmon resonance systems. Amperometry, voltammetry, and impedance spectroscopy represent electrochemical transducer methods; electrochemiluminescence with photoelectric conversion constitutes a widely utilized combined method. The transducing options function together with suitable nanoparticles: metallic and metal oxides, including magnetic ones, carbon-based nanotubes, graphene variants, luminescent carbon dots, nanocrystals as quantum dots, and photon up-converting particles. These sources merged together provide extreme variability of existing nanoimmunosensing options. Finally, applications in clinical analysis (markers, tumor cells, and pharmaceuticals) and in the detection of pathogenic microorganisms, toxic agents, and pesticides in the environmental field and food products are summarized.
- MeSH
- Biosensing Techniques * MeSH
- Immunoassay * MeSH
- Humans MeSH
- Nanoparticles chemistry MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Review MeSH
The DNA fragment d(GCGAAGC), occurring in the initial replication stage of the phage ?X174, in herpes simplex virus, in the promoter region of the heat-shock gene of E. coli and in rRNA genes is still in the focus of biological and biochemical research. This shortest hairpin guided us to study the relationship between the structure and function of other heptamers with changing triplet sequence in the center of the ODN molecule (AAA, GGG, CCC). Replacement of the central part of ODN was chosen because it was initially expected that the double peak of the G oxidation signal is due to the difference in the positions of G in the stem and a loop of the initially investigated d (GCGAAGC) fragment. The experiments, however, did not confirm this assumption. In this work, we have focused on the study of the interaction of selected heptamers with the surface of the mercury in order to answer the question to what extent the A + C reduction peaks and double-peak G oxidation signals are able to reflect the structures of heptamers affected by different central tri¬nucleotide sequences. Guanine residues d(GCGGGGC) in the structure of the quadruplex are resistant to structural changes and the voltammetric responses are therefore mini¬mized. The interactions of quadruplexes with the surface of the electrode are also weaker than interactions of hairpin structures d(GCGAAGC), d(GCAAAGC) and the duplex structure d(GCCCCGC). The presented research has shown that a small change in the central sequence not only can alter the structure (tetramolecular quadruplex, hairpin, bimolecular duplex) but also influences the electrochemical and adsorption properties of these molecules on the charged interface. Although electrochemistry is able to detect the various structural layout of the studied heptamers, it is desirable to support the electrochemical conclusions with other methods, e.g., UV-VIS absorption spectra reflecting chiroptic properties of ODNs and separation methods, such as gel electrophoresis (PAGE).
- MeSH
- Electrophoresis, Gel, Two-Dimensional MeSH
- Adsorption MeSH
- Chemistry Techniques, Analytical MeSH
- DNA * ultrastructure MeSH
- Electrochemistry MeSH
- DNA Fragmentation MeSH
- Molecular Conformation * MeSH
- Simplexvirus genetics MeSH
- Spectrum Analysis MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
Electrochemical methods, particularly when applied in connection with mercury-containing electrodes, are excellent tools for studying nucleic acids structure and monitoring structural transitions. We studied the effect of the length of the central (dG) n stretch (varying from 0 to 15 guanine residues) in 15-mer oligodeoxynucleotides (ODN, G0 to G15) on their electrochemical and interfacial behavior at mercury and carbon electrodes. The intensity of guanine oxidation signal at the carbon electrode (peak G(ox)) was observed to increase continuously with number of guanines between 0 and 15, with only a slight positive shift for ODNs with seven or more guanines in the central segment. Very different effects were observed when the peak G(HMDE) was measured at the mercury electrode. Intensity of the latter signal increased with number of guanines up to G5, and decreased sharply with further elongation of the (dG) n stretch. CD spectroscopy and electrophoresis experiments revealed formation of parallel intermolecular quadruplex structures for ODNs containing five or more G residues. Further measurements made by cyclic and alternating-current voltammetry revealed a strong influence of the ODN structure on their behavior at electrically charged surfaces.
In this study we have chosen a new approach and characterized three miRNAs (miR-23a, miR-34a and miR-320a) related to prostate cancer and head and neck cancer by spectral (circular dichroic and UV-absorption spectra) and electrochemical (voltammetry at graphite and mercury electrodes) methods. The spectral and voltammetric results, reflecting different nucleotide sequences of miRNAs, were complemented by the results of DNAs(U) having the same oligonucleotide sequences as miRNAs. The effect of the substitution of ribose for deoxyribose was shown and structural diversity was confirmed. The stability of RNA and DNA(U) was studied using CD and UV-absorption spectroscopy and melting points were calculated. MiRNA-320a with the highest content of guanine provided the highest melting point. With respect to the rapid progress of miRNA electrochemical sensors, our results will be useful for the research and development of sensitive, portable and time-efficient miRNA sensors, which will be able to diagnose cancer and other diseases.
- MeSH
- Circular Dichroism methods MeSH
- Electrochemistry methods MeSH
- Photoelectron Spectroscopy methods MeSH
- Humans MeSH
- MicroRNAs blood MeSH
- Biomarkers, Tumor blood MeSH
- Head and Neck Neoplasms blood MeSH
- Prostatic Neoplasms blood MeSH
- Case-Control Studies MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Interest in electrochemical analysis of purine nucleobases and few other important purine derivatives has been growing rapidly. Over the period of the past decade, the design of electrochemical biosensors has been focused on achieving high sensitivity and efficiency. The range of existing electrochemical methods with carbon electrode displays the highest rate in the development of biosensors. Moreover, modification of electrode surfaces based on nanomaterials is frequently used due to their extraordinary conductivity and surface to volume ratio. Different strategies for modifying electrode surfaces facilitate electron transport between the electrode surface and biomolecules, including DNA, oligonucleotides and their components. This review aims to summarize recent developments in the electrochemical analysis of purine derivatives, as well as discuss different applications.
Previously, it has been proved that resveratrol exhibits beneficial effect towards human health, maily due to its antioxidant attributes. Naturally, resveratrol occurs in its trans- form and is contained in plenty of plants, but the highest levels were determined in grapevine (Vitis vinifera L.). Thus, a wine contains negligible amounts of this attractive substance and consumption of a wine in appropriate quantity provides advantageous effects on the human body.
Many studies have already proven the positive effects of flavonoids on organisms. There are many plants which content important amounts of these secondary metabolites in their bodies, one of those being certainly vine (Vitis vinifera). The consumption of wine products is very popular all over the world and it is also connected with the health beneficial effects that it provides. Red wines content more flavonoids then other white or rosé varieties. It is mainly the consequence of the winemaking process during which the grape skin is either removed of left to release its secondary metabolite content, in case of the red and partially the rosé varieties
- MeSH
- Antioxidants MeSH
- Flavonoids * metabolism therapeutic use MeSH
- Humans MeSH
- Wine * MeSH
- Vitis MeSH
- Check Tag
- Humans MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
