Studies on the origin of the voltammetric response of the PC-3 cell suspension

Electrochemical response mechanism of DNA damaged cells: DNA damage repair and purine metabolism activation

In modern society, due to the sharp increase in pollutants that cause DNA damage, there is a growing demand for innovative detection techniques and biomarkers. In this paper, the electrochemical behavior of HepG2 cells exposed to CdCl2 was investigated, and the electrochemical response mechanism of DNA damage was identified by exploring the correlation between the DNA damage response and purine metabolism. Western blot analysis revealed that the expression levels of ATM and Ku70 increased at 0.3 μM CdCl2, indicating a DNA damage response and activation of DNA repair processes. Simultaneously, elevated expression levels of PRPP aminotransferase, HPRT, and XOD were observed, leading to an increase in intracellular purine levels and electrochemical signals. The expression of Ku70 peaked at 0.5 μM CdCl2, indicating the highest DNA repair activity. The expression profiles of these purine metabolism proteins mirrored those of Ku70, suggesting a strong correlation between the activation of purine metabolism and DNA damage repair. Consistently, intracellular purine levels exhibited a similar trend, leading to corresponding changes in electrochemical signals. In summary, electrochemical using intracellular purines as biomarkers has the potential to emerge as a novel method for detecting early DNA damage.

Electrochemistry detection of estrogenic effect: Regulation of de novo purine synthesis and catabolism by gibberellin and fulvestrant

The estrogenic effect of plant growth regulators has been received little attention, which leads to the lack of relevant toxicity data. In this study, the estrogenic effect induced by gibberellin with ERα-dependent manner was found by E-screen and western blot methods, and the electrochemical signals of MCF-7 cells regulated by gibberellin and fulvestrant were investigated. The results showed that the electrochemical signals of MCF-7 cells were increased by gibberellin, while reduced by fulvestrant significantly, and displayed an extremely sensitive response to the effects of estrogenic effect induced by ERα agonist and antagonist. Western blot results showed that the expressions of phosphoribosyl pyrophosphate amidotransferase and hypoxanthine nucleotide dehydrogenase in de novo purine synthesis and adenine deaminase in catabolism were more effective regulated by gibberellin and fulvestrant, resulting in significant changes of the levels of guanine, hypoxanthine and xanthine in cells, and then electrochemical signals. The results provide a theoretical basis for the establishment of new electrochemical detection method of the estrogenic effect of plant regulators.

Recent advances in electrochemical cell-based biosensors for food analysis: Strategies for sensor construction

Owing to their advantages such as great specificity, sensitivity, rapidity, and possibility of noninvasive and real-time monitoring, electrochemical cell-based biosensors (ECBBs) have been a powerful tool for food analysis encompassing the areas of nutrition, flavor, and safety. Notably, the distinctive biological relevance of ECBBs enables them to mimic physiological environments and reflect cellular behaviors, leading to valuable insights into the biological function of target components in food. Compared with previous reviews, this review fills the current gap in the narrative of ECBB construction strategies. The review commences by providing an overview of the materials and configuration of ECBBs, including cell types, cell immobilization strategies, electrode modification materials, and electrochemical sensing types. Subsequently, a detailed discussion is presented on the fabrication strategies of ECBBs in food analysis applications, which are categorized based on distinct signal sources. Lastly, we summarize the merits, drawbacks, and application scope of these diverse strategies, and discuss the current challenges and future perspectives of ECBBs. Consequently, this review provides guidance for the design of ECBBs with specific functions and promotes the application of ECBBs in food analysis.

The toxicity response of the electrochemical signal of the cell to the drug metabolized by the S9 system

The electrochemical detection method of cytotoxicity using intracellular purines as biomarkers has shown great potential for in vitro drug toxicity evaluation. However, no electrochemical detection system based on an in vitro drug metabolism mechanism has been devised. In this paper, electrochemical voltammetry was used to investigate the effect of the S9 system on the electrochemical behavior of HepG2 cells, and benzo[a]pyrene, fluoranthene, and pyrene were employed to investigate the sensitivity of electrochemical signals of cells to the cytotoxicity of drugs metabolized by the S9 system. The results showed that, within 8 h of exposure to the S9 system, the electrochemical signal of HepG2 cells at 0.7 V did not alter noticeably. The levels of xanthine, guanine, hypoxanthine, and adenine in the cells were not significantly altered. Compared with the absence of S9 system metabolism, benzo[a]pyrene and fluoranthene processed by the S9 system decreased the electrochemical signal of the cells in a dose-dependent manner, while pyrene did not change it appreciably. HPLC also revealed that benzo[a]pyrene and fluoranthene metabolized by the S9 system decreased the intracellular purine levels, whereas pyrene had no effect on them before and after S9 system metabolism. The cytotoxicity results of the three drugs examined by electrochemical voltammetry and MTT assay showed a strong correlation and good agreement. The S9 system had no effect on the intracellular purine levels or the electrochemical signal of cells. When the drug was metabolized by the S9 system, variations in cytotoxicity could be precisely detected by electrochemical voltammetry.

K2Cr2O7-induced DNA damage in HT1080 cells: Electrochemical signal response mechanism

The existing DNA damage detection technology cannot meet the current detection requirements. It is critical to build new methods and discover novel biomarkers. In this study, alkaline comet and 8-OHDG ELISA assays were used to identify DNA damage in HT-1080 cells exposed to K2Cr2O7, and electrochemical behaviors of HT-1080 cells with DNA damage was studied. With an increase in K2Cr2O7 exposure time, two electrochemical signals from HT-1080 cells at 0.69 and 1.01 V steadily grew before decreasing after reaching their highest values. The electrochemical signal's initial response time and peak time decreased as the concentration of K2Cr2O7 increased. The duration of the high dose group was 0.5 and 1 h, while the low dose group was 1.5 and 6 h. Western blotting analysis revealed that DNA damage increased the expression of proteins involved in catabolism and de novo purine synthesis, particularly de novo purine synthesis. Expressions of PRPP amidotransferase, IMPDH, and ADA were all higher than those of ADSS, XOD, and GDA, which resulted in larger concentrations of hypoxanthine, guanine, and xanthine, and in turn improved electrochemical signaling. These findings suggest that intracellular purine identified by linear scan voltammetry is predicted to evolve as a marker of early DNA damage.

A dual-functional module cellular electrochemical sensing platform for simultaneous detection guanine and xanthine

The separation of the superimposed electrochemical signals of intracellular guanine (G) and xanthine (X) is difficult, which is great obstacle to the application of cell electrochemistry. In this paper, independent functional modules, G-functional module (G-FM) and X-functional module (X-FM), were constructed by molecular imprinting technology for sensitive detection of G and X without mutual interference, then integrated in dual-functional module cellular electrochemical sensing platform (DMCEP) as signal sensing units. DMCEP transmitted signals of G and X in cells synchronously to two windows by two signal sensing channels, and achieved the separation of superimposed signals of G and X in cells. DMCEP exhibited satisfactory reproducibility with relative standard deviation (RSD) of 3.10 and 2.22 %, repeatability with RSD of 3.72 and 3.05 % for G and X detection, and detection limit 0.05 μΜ for G and 0.06 μΜ for X. Good linear relationships between cell concentrations and the signals of G and X on DMCEP were shown in range of 0.75-85 × 10⁶ and 3-85 × 10⁶ cells/mL, respectively. The growth of MCF-7 cells was tracked by DMCEP, and showed consistent trend with the cell counting method, while the change of cell viability from lag to logarithmic phase captured by DMCEP was earlier than that of cell counting method. This strategy provided the foundation for the establishment of the cell viability electrochemical detection method, and new insights into the simultaneous recording of other analyses with superimposed peak positions and the simultaneous tracking of multiple biomarkers.

Electrochemical detection mechanism of estrogen effect induced by cadmium: The regulation of purine metabolism by the estrogen effect of cadmium

Some heavy metals in the environment may have estrogen-like activity, which probably lead to major diseases such as breast cancer. It is of great importance to establish new methods to evaluate the estrogen effect of heavy metals from multiple angles due to the complex mechanism of estrogen effect. In this paper, using MCF-7 cells as model, the electrochemical detection mechanism of the estrogen effect of heavy metal cadmium (Cd) was studied. The two electrochemical signals of MCF-7 cells derived from uric acid (0.30 V) and the mixture of guanine and xanthine (0.68 V) increased in a time and dose-dependent manner when MCF-7 cells induced by Cd, reaching the maximum at 96 h and 10-9 mol L-1. Further studies found that three purine metabolism pathways about de novo synthesis, salvage synthesis and decomposition metabolism were activated by the estrogen effect of Cd. The expression of PRPP amidotransferase in purine de novo synthesis pathway and HPRT in purine salvage synthesis pathway up-regulated, especially HPRT, which promoted cell proliferation together. Nevertheless, the expression of GDA and ADA, the key enzymes in purine decomposition metabolism pathway, up-regulated in a time and dose-dependent manner, which had same tendency with that of ERα, thereby increased the content of intracellular hypoxanthine, guanine, xanthine and uric acid, and enhanced electrochemical signals.

The electrochemical potential is a key parameter for cell adhesion and proliferation on carbon surface

The Nernst potential of the support/cell interface is suspected to play a key role in cell adhesion and proliferation. However, the studies that have addressed this topic have generally varied the electrochemical potential of the interface by comparing different materials or by varying the chemical composition of the surface coating. It is consequently hard to definitively separate the actual effect of the potential from possible side-effects due to differences in the surface composition or topography. Here, a 3-electrode set-up was used to apply different values of potential to identical carbon electrodes. Potentials were applied in the range -200 to 400 mV vs. silver pseudo-reference (SPR), i.e. 90 to 690 mV/SHE, to screen-printed carbon electrodes used to grow Vero or Raw 264.7 cell lines. Values up to 200 mV/SPR prohibited cell adhesion and even caused detachment of cells that were previously adhered. The value of 400 mV/DRP allowed cell adhesion and proliferation, leading to confluent and sometimes very compact mats. The zero charge potential, measured around 200 mV/DRP, showed that the drastic effect of the applied potential was probably due to the negative/positive switch of the surface charge.

Cell-based electrochemical cytosensor for rapid and sensitive evaluation of the anticancer effects of saponin on human malignant melanoma cells

Discovering new anticancer agents and analyzing their activities is a vital part of drug development, but it requires a huge amount of time and resources, leading to the increasing demands for more-effective techniques. Herein, a novel and simple cell-based electrochemical biosensor, referred to as a cytosensor, was proposed to investigate the electrochemical behavior of human skin malignant melanoma (SK-MEL28) cells and the anticancer effect of saponin on cell viability. To enhance both electrocatalytic properties and biocompatibility, gold nanoparticles were electrochemically deposited onto a conductive substrate, and poly-L-lysine was further added to the electrode surface. Electric signals from SK-MEL28 cells on the electrodes were obtained from cyclic voltammetry and differential pulse voltammetry. The cathodic peak current was proportional to the cell viability and showed a detection range of 2,880-40,000 cells per device with an excellent linear cell number-intensity relationship (R²= 0.9952). Furthermore, the anticancer effect of saponin on SK-MEL28 cells was clearly established at concentrations higher than 20 μM, which was highly consistent with conventional assays. Moreover, the developed electrochemical cytosensor for evaluating anticancer effects enabled rapid (<2 min), sensitive (LOQ: 2,880cells/device), and non-invasive measurements, thus providing a new avenue for assessing the anticancer drugs in vitro.

Development of a paper-based microanalysis device doped with multi-walled carbon nanotubes for in vitro evaluation of fluorene cytotoxicity

Developing a cost-effective and simple micro-analysis tool has long been an important objective in the toxicological detection of fluorene. In this study, a disposable paper-based micro-analysis device (μ-PAD) was designed using graphite doped with multi-walled carbon nanotubes (MWCNTs) to hand draw the electrode (MWCNTs/μ-PAD). We investigated the feasibility of the designed MWCNTs/μ-PAD as a cell-sensing platform using voltammetry measurements. Its application for evaluating the cytotoxicity of fluorene was studied based on the electrochemical determination of human breast cancer cells induced by fluorene. The results showed a dose-dependent toxicity effect of fluorene on cellular activity. The measurements were comparable with those obtained using a methyl-thiazolyl-tetrazolium assay. The detection limit of the MWCNTs/μ-PAD for human breast cancer cells was as low as 4.00 × 10³ cells·mL^-1 owing to the enhanced catalytic activity of the MWCNTs. Notably, the MWCNTs/μ-PAD-which had a diameter of 7.00 mm-allowed a sampling volume of 10.0 μL, which is 50.0 times less than the sampling volume required with a conventional electrode (500 μL). Advantages such as the simplicity of manufacture, low consumption, low cost, rapid detection, and disposability, suggest that the MWCNTs/μ-PAD could provide new opportunities and directions for in vitro microanalysis.

A label-free approach to detect cell viability/cytotoxicity based on intracellular xanthine/guanine by electrochemical method

INTRODUCTION

Cell viability and cytotoxicity is one of the most important toxicology indicators. In this study, an electrochemical method for detecting cell viability and cytotoxicity was discussed with the intracellular small molecule metabolite purines as indexes.

METHODS

The electrochemical behaviors of Balb/c 3T3, CHO, PC-12 and V79 cell suspensions were studies by cyclic voltammetry, and cell viability and cytotoxicity of four cell lines were compared by electrochemical, cell counting, 3-(4,5-dimethyl-2-Thiazyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) and trypan blue exclusion methods.

RESULTS

Four cell lines all showed an oxidation peak derived from mixture of xanthine and guanine at about 0.7 V. Using intracellular xanthine and guanine as index, the electrochemical method could not only describe the cell growth curves of four cell lines, but also reflect the changes of cell viability at various phases of the cell growth prior to the counting method. Compared with MTT, cell counting and trypan blue staining methods, the electrochemical method could detect the cytotoxicity of carcinogen earlier and more sensitively.

DISCUSSION

The electrochemical method could track the change of intracellular xanthine and guanine contents, and used it as index to detect cell viability and cytotoxicity at the molecular level without markers, showing greater advantages over the method with apparent cell proliferation as the endpoint.

Construction and application of a new cell electrochemical detecting system based on the hyposmotic principle

A new cell electrochemical detecting system has been constructed based on the hyposmotic principle, in which the electrochemical signals have been strengthened by about 109.75% for the signal at about +0.70 V and 532.94% for the signal at about +1.03 V. The electrochemical detection limits of the cells have been improved by one order of magnitude. The individual concentrations of intracellular purines have been obtained.

A Mini-Electrochemical System with Integrated Micropipet Tip and Pencil Graphite Electrode for Measuring Cytotoxicity

A novel mini-electrochemical system has been developed for evaluating cytotoxicity of anticancer drugs based on trace cell samples. The mini-electrochemical system was integrated by using pencil graphite modified with threonine as working electrode, an Ag/AgCl reference electrode and a micropipet tip as electrochemical cell. The mini-electrochemical system dramatically reduces sample volumes from 500 μL in a traditional electrochemical system to 10 μL, and exhibits excellent electrocatalytic activity toward oxidation of purine from MCF-7 cells due to increased sensitivity provided by threonine. Moreover, the relationship between peak current and the cell concentration in the range from 3.0 × l0³ to 7.0 × l0⁶ cells/mL was studied, and a nonlinear exponential relationship between them was established over a wide concentration range. In evaluating the effect of anticancer drugs on cell viability, the results of drug cytotoxicity test based on cyclophosphamide were in close agreement with classical 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assays. The proposed device is so simple, cheap, and easy to operate that it could be applied to single-use applications. The mini-electrochemical system proved to be a useful tool and can be applied to electrochemical studies of cancer cells as well as other biological samples such as proteins and DNA.

Electrochemical estrogen screen method based on the electrochemical behavior of MCF-7 cells

It was an urgent task to develop quick, cheap and accurate estrogen screen method for evaluating the estrogen effect of the booming chemicals. In this study, the voltammetric behavior between the estrogen-free and normal fragmented MCF-7 cell suspensions were compared, and the electrochemical signal (about 0.68V attributed by xanthine and guanine) of the estrogen-free fragmented MCF-7 cell suspension was obviously lower than that of the normal one. The electrochemistry detection of ex-secretion purines showed that the ability of ex-secretion purines of cells sharp decreased due to the removing of endogenous estrogen. The results indicated that the electrochemical signal of MCF-7 cells was related to the level of intracellular estrogen. When the level of intracellular estrogen was down-regulated, the concentrations of the xanthine and hypoxanthine decreased, which led to the electrochemical signal of MCF-7 cells fall. Based on the electrochemical signal, the electrochemical estrogen screen method was established. The estrogen effect of estradiol, nonylphenol and bisphenol A was evaluated with the electrochemical method, and the result was accordant with that of MTT assay. The electrochemical estrogen screen method was simple, quickly, cheap, objective, and it exploits a new way for the evaluation of estrogenic effects of chemicals.

Functionalized solid electrodes for electrochemical biosensing of purine nucleobases and their analogues: a review

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.

In situ electrochemical assessment of cytotoxicity of chlorophenols in MCF-7 and HeLa cells

An in situ electrochemical method was used to assess the cytotoxicity of chlorophenols using human breast cancer (MCF-7) and cervical carcinoma (HeLa) cells as models. On treatment with different chlorophenols, the electrochemical responses of the selected cells, resulting from the oxidation of guanine and xanthine in the cytoplasm, indicated the cell viability. In addition, the in situ in vitro electrochemical method was further compared with the traditional MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays. Although similar cytotoxicity data were obtained from both methods, the effective concentrations of chlorophenols that inhibited 50% cell growth (EC50 values) from the electrochemical method were only slightly lower than those from the MTT assay. These results indicate that the in situ in vitro electrochemical method paves a simple, rapid, strongly responsive, and label-free way to the cytotoxicity assessment of different chlorophenol pollutants.

A novel electrochemical method to evaluate the cytotoxicity of heavy metals

There is an ongoing search to develop techniques for detection of heavy metals which are highly toxic and can cause damaging effects even at very low concentrations. In this present study, we report a label-free electrochemical method based on the direct voltammetric response of human cervical carcinoma (HeLa) cells on a highly sensitive graphene modified electrode. Five heavy metals were tested with the method and the results were validated by the traditional methyl tetrazolium (MTT) assay. The results revealed that the most toxic metal was Cr, followed by Cd, Cu, Pb and Zn. A good correlation between the two methods was observed. This work will be beneficial in providing a novel monitoring method to detect hazardous pollutants in the field of environmental toxicology.

Detection of the cell viability and proliferation using two-signal electrochemical method

Two electrochemical signals of the MCF-7 cell were simultaneously detected by using multiwall carbon nanotubes and room temperature ionic liquid composite film modified electrode. The signal at +0.726 V due to the oxidation of xanthine and guanine, was obviously improved. And the signal at +1.053 V due to the oxidation of hypoxanthine and adenine was found for the first time. This two-signal electrochemical method is credible to detect cell viability and proliferation.