Electrochemical Detection System Research Articles

Towards using high-performance liquid chromatography at home

In order to make high-performance liquid chromatography (HPLC) more widely available at home and in small-scale settings, we have simplified two of its most costly modules, namely the pump and the detector. This should make the setup affordable for home or small laboratory use. A manual HPLC pump was constructed so as to fit into a caulk gun from a local hardware store enabling the generation of 100-150 bar of pressure. In order to limit the pressure drop during the running of a chromatogram, a pulse dampener was developed. We further modified the electrochemical detection (ECD) system so as to use a cheap boron-doped diamond electrode with an overlay of thin filter paper, causing an eluent flow over the electrode by wicking and gravity. Both the pump and the detector are at least ten times cheaper than conventional HPLC modules.Using a home-packed JupiterⓇ Proteo reversed phase capillary column we show how this low-cost HPLC system generates well resolving chromatograms after direct injection of fresh urine. The ECD did not lose its sensitivity during regular use over more than half a year. For homovanillic acid (HVA), which is of medical interest, we measured a linear dynamic range of two orders of magnitude, a detection limit of HVA in the injected sample of 3 μM and a coefficient of variation <10%. The contribution to peak broadening by the detector was much smaller than the contributions by the injector and by the column. After consumption of table olives containing hydroxytyrosol (HT), its metabolite HVA in the corresponding urine could be measured quantitatively. An approach to quantify HT in table olives is presented, as well. This method provides a new tool for investigating physiology of oneself or of dear ones at home.

Direct electrochemical enhanced detection of dopamine based on peroxidase-like activity of Fe3O4@Au composite nanoparticles

Substantially, the unique enzyme-like bioactivity of nanoparticles is essential for the detection performance promotion of electrochemical sensors. Herein, the gold magnetic particles (Fe3O4@Au) were successfully formed by self-assembly method, its physical and chemical properties are characterized by Fourier transform infrared (FT-IR), Transmission electron microscopy (TEM) and Vibrating sample magnetometer (VSM) techniques. Fe3O4@Au was found to be able to exhibit impressive peroxidase-like activity and follow Michaelis-Menten kinetics with a good affinity towards H2O2 and TMB. A novel highly sensitive and selective enzyme-free enhanced electrochemical sensor based on the peroxidase-like activity of Fe3O4@Au was prepared for the detection of dopamine (DA). Electrochemical cyclic voltammetry (CV) was used to measure dopamine and the electrochemical detection system was optimized. The results showed that the established enzyme-free enhanced electrochemical sensor showed extremely high sensitivity towards dopamine under the optimized conditions, with a good linear relationship between the current response, and the concentration of dopamine in the range of 0.01–1 mmol/L with a detection limit of 0.0109 mg/L (S/N = 3). In addition, the established enzyme-free enhanced electrochemical sensor was successfully applied in the detection of dopamine in pork samples. In view of this, the proposed new enzyme-free electrochemical assay has great potential in the fields of food quality control and security detection.

Recent Progress in Electrochemical Detection of Human Papillomavirus (HPV) via Graphene‐Based Nanosensors

In the present study, applications of advanced nanomaterials such as graphene oxide (GO), reduced graphene oxide (rGO), and graphene quantum dots (GQDs) as leading and potential candidates toward treating the human papillomaviruses (HPVs) were investigated. In this matter, a comprehensive summary of the formation of GO, rGO, and GQDs will be reported in detail. Continuous efforts have been exerted to develop high‐performance biosensors and electrochemical detection systems toward accurate detection of HPV using novel routes. This review paper showed that HPVs appeared in different types and species. These HPVs have many complications on humans, and thus, there are different ways that a person could be exposed to them. Meanwhile, several routes of transmitting the HPVs to human cells are discussed too. Indeed, sexually transmitted diseases could be easily infected by HPVs, although the human immune system can also be boosted to treat this dangerous virus effectively. Some of the HPVs such as HPV‐16 and HPV‐18 are so dangerous, and HPV DNA could be detected in several vertical cancers. Herein, we reported and summarized some recent progress in electrochemical detection of HPVs using graphene‐based nanosensors.

Detection of the SARS-CoV-2 spike protein in saliva with Shrinky-Dink© electrodes

Using the children's toy, Shrinky-Dink©, we present an aptamer-based electrochemical (E-AB) assay that recognizes the spike protein of SARS-CoV-2 in saliva for viral infection detection. The low-cost electrodes are implementable at population scale and demonstrate detection down to 1 ag mL-1 of the S1 subunit of the spike protein.

Cross-triggered and cascaded recycling amplification system for electrochemical detection of circulating microRNA in human serum.

A cross-triggered and cascaded recycling amplification system was developed for electrochemical sensing of microRNA 122 based on the DNAzyme/multicomponent nucleic acid enzyme cleavage technique and a dumbbell-shaped probe. The linear range and detection limit were obtained to be 1 fM-100 pM and 0.34 fM, respectively. Compared with some reported studies, the proposed system can achieve the selective detection of endogenous miRNA in liver injury patients and healthy human serums with the advantages of high sensitivity, low cost, and easy manipulation, which are significant for disease diagnosis as well as the fundamental research of molecular biology.

Advances in the Detection of Toxic Algae Using Electrochemical Biosensors.

Harmful algal blooms (HABs) are more frequent as climate changes and tropical toxic species move northward, especially along the Iberian Peninsula, a rich aquaculture area. Monitoring programs, detecting the presence of toxic algae before they bloom, are of paramount importance to protect ecosystems, aquaculture, human health and local economies. Rapid, reliable species identification methods using molecular barcodes coupled to biosensor detection tools have received increasing attention as an alternative to the legally required but impractical microscopic counting-based techniques. Our electrochemical detection system has improved, moving from conventional sandwich hybridization protocols using different redox mediators and signal probes with different labels to a novel strategy involving the recognition of RNA heteroduplexes by antibodies further labelled with bacterial antibody binding proteins conjugated with multiple enzyme molecules. Each change has increased sensitivity. A 150-fold signal increase has been produced with our newest protocol using magnetic microbeads (MBs) and amperometric detection at screen-printed carbon electrodes (SPCEs) to detect the target RNA of toxic species. We can detect as few as 10 cells L−1 for some species by using a fast (~2 h), simple (PCR-free) and cheap methodology (~2 EUR/determination) that will allow this methodology to be integrated into easy-to-use portable systems.

Fluorescent and electrochemical dual-mode detection of Chikungunya virus E1 protein using fluorophore-embedded and redox probe-encapsulated liposomes.

The critical goal of sensitive virus detection should apply in the early stage of infection, which may increase the probable survival rate. To achieve the low detection limit for the early stage where a small number of viruses are present in the sample, proper amplified signals from a sensor can make readable and reliable detection. In this work, a new model of fluorescent and electrochemical dual-mode detection system has been developed to detect virus, taking recombinant Chikungunya virus E1 protein (CHIK-VP) as an example. The hydrophobic quantum dots (QDs) embedded in the lipid bilayer of liposome and methylene blue (MB) encapsulated in the inner core of liposomes played a role of dual-signaling modulator. After CHIK-VP addition, the nanocomposites and APTES-coated Fe3O4 nanoparticles (Fe3O4 NPs) were conjugated with antibodies to form a sandwich structure and separated from the medium magnetically. The nanoconjugates have been burst out by chloroform as surfactant, and both the QDs and MB are released from the liposome and were then monitored through changes in the fluorescence and electrochemical signals, respectively. These two fluorometric and electrochemical signals alteration quantified the CHIK-VP in the range of femtogram to nanogram per milliliter level with a LOD of 32 fg mL−1, making this liposomal system a potential matrix in a virus detection platform. Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s00604-020-04656-2.

Development of an Electrochemical Biosensor of Ubiquitin C-Terminal Hydrolase L1 (UCH-L1) for the Assessment of Traumatic Brain Injury (TBI)

INTRODUCTION Traumatic brain injury (TBI) is defined as a neurotrauma caused by a mechanical force applied to a head. An appropriate clinical therapy after TBI is crucial, or patients may suffer lasting effects in physical and mental abilities [1]. To find TBI, cranial computer tomography (CT) is commonly used, however, CT sometimes fails to find mild TBI (mTBI) even it accounts for majority of all cases of TBI. Recently, a blood-based biomarker, ubiquitin C-terminal hydrolase L1 (UCH-L1) has been regarded a promising marker for mTBI, as it becomes present in serum soon after TBI [2,3]. Actually, it was reported the elevated serum UCH-L1 level was observed with the soldiers exposed to low-level blast [4] and the athletes after sub-concussive dead hits [5]. Enzyme-linked immuno sorbent assay (ELISA) is currently used to detect the biomarker, however, since the ELISA is time-consuming procedure and requires specific laboratory equipment, development of a hand-held device to be used on-site in the field is expected. In this study, we propose and report a novel principle for a rapid, one-step electrochemical detection system for UCH-L1 to be dedicated for mTBI diagnosis. METHOD To detect UCH-L1, we chose an electrochemical method in terms of a rapid response time, miniaturization, and simple instrumentation. We employed a competitive assay combined with square wave voltammetry (SWV) on anti-UCH-L1 antibody immobilized electrode. In this system, a redox probe (phenazine ethosulfate: PES) modified UCH-L1 and the target biomarker is going to competitively bind to the antibody on the electrode, resulting electrochemical signal depend on the concentration of UCH-L1 in a sample. To construct the system, PES modified UCH-L1 was prepared using amine-reactive PES. This molecule has N-hydroxysuccinimide linked to PES, therefore, upon mixing amine-reactive PES with UCH-L1, it will react with amine group of lysine residue and make a covalent bond. After the modification, enzyme-linked immuno sorbent assay (ELISA) was performed to investigate the binding affinity of anti-UCH-L1 antibody against UCHH-L1 and PES modified UCH-L1. To detect UCH-L1, we added UCH-L1 together with PES-modified UCH-L1 on the antibody immobilized gold electrode, and performed SWV at a potential range of -0.5 to 0.1 V with different frequencies of square wave. RESUTLS The result of ELISA showed that the antibody had almost same affinity against non-labeled UCH-L1 and PES-modified UCH-L1. Therefore, the modification of PES did not affect the recognition of antibody. When we incubated the electrode with different concentration of PES-modified UCH-L1, a square wave voltammetry signal was increased in a concentration dependent manner, indicating the PES modified on the UCH-L1 was electrochemically active, and the amount of PES-modified UCH-L1 was detected by SWV when it was captured by anti-UCH-L1 antibody on the electrode. In the competitive assay, the incubation of intact UCH-L1 together with PES-modified UCH-L1 resulted in the SWV signal change depend on the UCH-L1 concentration. With this detection principle, we could detect UCH-L1 within 10 minutes without any washing procedure, which is ideal for the on-site detection of mTBI. CONCLUSION In this study, we developed a rapid electrochemical detection system of TBI biomarker, UCH-L1, based on the competitive of redox probe-modified UCH-L1 with the target. Using this detection system, we were able to observe SWV signal change within 10 minutes upon addition of UCH-L1. This study shows the proof-of-concept of this rapid competitive assay, and we hope it would help future development of TBI detection device. REFERENCES [1] S. W. Hoffman and C. Harrison, Clin. Neuropsychol., 23(8), 1400–1415 (2009).[2] R. Diaz-Arrastia, K. K. W. Wang, L. Papa, M.D. Sorani, J. K. Yue, A. M. Puccio, P. J. McMahon, T. Inoue, E. L. Yuh, H. F. Lingsma, A. I. R. Maas, A. B. Valadka, D. O. Okonkwo, G. T. Manley, TRACK-TBI Investigators, J. Neurotrauma, 31(1), 19–25 (2013).[3] L. Papa, G. M. Brophy, R. D. Welch, L. M. Lewis, C. F. Braga, C. N. Tan, N. J. Ameli, M. A. Lopez, C. A. Haeussler, D. I. M. Giordano, S. Silvestri, P. Giordano, K. D. Weber, C. Hill-Pryor, D. C. Hack, JAMA Neurol., 73(5), 551–560 (2016).[4] C. M. Tate, K. K. W. Wang, S. Eonta, Y. Zhang, W. Carr, F. C. Tortella, R. L. Hayes, G. H. Kamimori, J. Neurotrauma, 30(19), 1620–1630 (2013).[5] V. Puvenna, C. Brennan, G. Shaw, C. Yang, N. Marchi, J. J. Bazarian, K. Merchant-Borna, D. Janigro, PLoS ONE, 9(5), e96296–9 (2015).

Development of a Lab on a Chip Prototype for Sex Detection in Plants

INTRODUCTION The fruit industry employs millions of hectares for production; of these, a significant percentage uses only female or hermaphrodite plants. The selection is carried out by morphological analysis, waiting from 10 to 16 weeks until blooming, which represents an inefficient use of resources. Typically, well-equipped laboratories and trained personnel are required to perform DNA analysis and give valid results [1-2]. Devices capable of generating this information within a short timespan could contribute to a fast and effective selection of productive plants, that translates in resource savings and an increase in production. In this work, the implementation of an alternative DNA analysis in a single chip is evaluated. The objective is the development of a fully integrated device which incorporates all sequential steps to evaluate vegetal material, that ensure an easy to use product, safeguarding the correct use by non-trained operators and reducing the time to obtain a result. This will cover a chip design able to take the sample, contain the extraction and amplification of genetic material, and the evaluation of two different detection systems (optical and electrochemical). MATERIALS AND METHODS The chip was fabricated in a 3 mm thick acrylic PMMA with a CNC micromilling equipment. Each chip is composed of four cavities (15 to 30 µL) and connected by channels (width 300 – 100 µm, height 150 µm). After the addition of the reactants, are sealed with adhesive double-sided tape and a 1 mm thick PDMS membrane. The electrochemical detection design is composed by three electrodes (WE-Au, AE-Au, RE-Ag|AgCl), 0.5 M Ru(NH3)6Cl3 as a DNA intercalating agent [3] in 40 mM TAE buffer. A random squence of DNA (5’-TAGTCGTCAATCCTCCGCTT) (50 – 540 ng/µL) was tested to evaluate the efficiency of the system by three electrochemical techniques (SWV, DPV and CV) in a BioLogic potentiostat. On the other hand, the optical detection system is composed of a phototransistor (Max. sensitivity @ 550 nm), a filter (520 nm) and a led (Max. WL peak @ 455 nm) to detect the fluorescent DNA intercalator SYBRgreen. Different concentrations of fluorescein (0.005 – 10 µM) were used to evaluate the system capabilities. Then, the system was evaluated with the same DNA sequence and compared with a fluorescence microscope (Nikon Eclipse Ti-u). RESULTS In the electrochemical detection system, we observed a proportional decrease in the Ru(NH3)6Cl3 signal as the DNA concentration increase. The data showed that square wave voltammetry was the most sensitive technique (R2=0.9372, LOD 158.01 ng/µL and LOQ 722.39 ng/µL), although the three were adequate for detection. In the optical detection system, we observed a similar tendency in the signals (LOD 111.50 ng/µl) compared to the microscope results (LOD 94.16 ng/µL) showing a R2=0.982, validating the functionality of our system. Current results show that the optical system is more sensitive and could let us differentiate smaller concentrations of DNA. CONCLUSIONS In this work a lab on a chip prototype was designed, fabricated and tested. The chips are disposable and need minimal human intervention after the sampling. It’s capable of performing DNA detection through two different systems, however, the optical detection system showed more sensitivity. Nevertheless, the evaluation of vegetal material is needed to further validations. REFERENCES [1] Walter Barrantes, Carlos Lorìa, Luis Gòmez, “Evaluation of two-sex determining systems in papaya plants (Carica papaya) Pococì hybrid”, Experimental Station Fabio Baudrit, Costa Rica University, Costa Rica, 2019.[2] Cornelis Senne, “Forensic Lab on a Chip DNA analysis”, Laboratory of Pharmaceutical Biotechnology, Department of life Science Technologies, Imec, Ghent University. Belgium, 2019.[3] Lü-Ying Li, Hai-Na Jia, Hui-Juan Yu, Ke-jie Du, “Synthesis characterization, and DNA binding studies of ruthenium complexes [Ru(tpy)(ptn)]2+ and Ru(dmtpy)(ptn)]2+. KEYWORDS: microfluidics, electrochemical detection, optical detection, fluorescent dye, DNA. Figure 1

(Invited) High-Sensitive Electrochemical Detector with Micro-Stirrer Driven By Surface Acoustic Wave

Micro total analysis system (μTAS), by applying microfabrication technology used in the manufacture of semiconductor integrated circuits, applies chemical processing and biochemical analysis usually conducted using test tubes in a laboratory to microscopic flow paths fabricated on a chip, and it is an ultra compact analytical system.Advantages of μTAS are that it requires only a small amount of sample used for measurement, the space in the groove is narrow, so that the diffusion distance of molecules can be shortened, the reaction time can be shortened, automation of measurement including pretreatment, miniaturization of the equipment, disposable of the equipment, low cost, reduction of manpower and the like can be cited.If μTAS is put into practical use, it is expected that everyone can easily and accurately inspect on site. However, as μTAS uses extremely small samples such as tens of microliters, the issues such as handling difficulty and reproducibility remain. Turning to the electrochemical sensor, electrochemical measurement is effective as a detection method in μTAS because it has advantages such as fast response, inexpensive, easy to miniaturize, and so far, many electrochemical biosensors have been reported. Generally, in the electrochemical measurement, based on the electron transfer between the analyte on the electrode surface and the electrode, the analyte is detected from the current value. In the analysis with a sample volume of several milliliter scale, the agitator is placed in the solution cell and stirring is carried out, whereby the supply to the electrode surface of the measurement analyte is enhanced, whereby high sensitivity can be detected. However, μTAS can not place a stirrer because it uses a small amount of tens of microliters, and it is difficult to stir manually, the diffusion of the detection analyte to the electrode surface becomes rate-limiting, causing a decrease in sensor sensitivity. Therefore, in this research, we focused on an actuator using surface acoustic wave (SAW) in order to solve the problem that sensor sensitivity decreases in electrochemical measurement of a small amount of sample. Surface acoustic waves are vibrations that concentrate and propagate on the surface of an object and can be generated by applying a high frequency potential to the IDT (Inter digital transducer) fabricated on the surface of the piezoelectric substrate. IDT can be easily fabricated by conventional photolithography technology. Since surface acoustic waves can be driven by microscale pattern electrodes fabricated by microfabrication, they are suitable for handling a very small amount of liquid droplets. Many reports have been reported as droplet flow manipulation techniques by using SAW. In the field of biotechnology, application to PCR with enhanced reaction efficiency of trace amounts of samples has been reported. Many researches have also been reported in which SAW is applied as a conversion element of a biosensor. A detection method by label free is proposed by measuring the frequency shift due to adsorption to the sensor surface. In recent years, co-authors reported a technology to place a small amount of 5 μL droplets in the pool and drive them by SAW. They also studied the relation between the power supplied to the IDT and the angular velocity and temperature of stirring the liquid using the SAW driven micro liquid rotor.If we could fuse this SAW technology with electrochemical measurement and stir a small amount of sample, diffusion of the target substance to the electrode surface increased, and we thought that we could solve the problem of sensitivity reduction due to diffusion control. In this research, we propose a novel measurement system which electrochemical detection is carried out by integrating 3 electrode system for electrochemical detection on SAW substrate developed by bicycle, and stirring minute amount of sample by SAW. As a result, it is possible to increase the diffusion rate of the analyte in the small amount sample to the electrode surface, aiming at constructing an electrochemical detection system with high sensitivity and good reproducibility. Figure 1

Electrochemical detection of baicalein based on a three-dimensional micromixer

Baicalein, a kind of flavonoid, has many medical benefits, and therefore, its accurate and efficient determination is necessary in the field of medical ingredient detection. To achieve the rapid and precise detection of baicalein, a three-dimensional (3D) expansion–contraction wave micromixer was designed and used along with an electrochemical detection method to assemble a micromixing electrochemical detection system. First, the performances of the wave micromixers were investigated using the COMSOL Multiphysics 5.3 a software with three optimisation objectives, namely, the mixing uniformity, pressure drop, and mixing performance index, to comprehensively evaluate the properties of the micromixers. Second, a 3D expansion–contraction wave micromixer with optimal mixing properties was fabricated using the 3D printing technology. Third, a micromixing electrochemical detection system was built to study the redox behaviours of baicalein through the electrochemical cyclic voltammetry method. The effects of buffer varieties, buffer pH values, scanning speeds, and inlet flow rates on the redox curves of baicalein were studied to determine the appropriate experimental conditions. The results demonstrated that the currents of the oxidation peak increased linearly with the baicalein concentrations within the range of 3.55 × 10−6–5.92 × 10−5 mol l−1 and the detection limit of 1.861 × 10−8 mol l−1 (S/N = 3). The relative standard deviation among the results obtained through repeated experiments was 2.86%; this proves a high detection reproducibility of the new method. Compared with spectrophotometry, the error determined using the novel method in a real sample detection was 0.31%, thus achieving an efficient and precise detection of baicalein. The micromixing electrochemical detection method can remarkably improve the mixing efficiency, shorten the detection time, and decrease the detection limit, and therefore could be popularised for the exact content detection of other flavonoids.

Application of naphthalene diimide in biotechnology

Naphthalene diimide (NDI) is an electron-deficient, robust, and planar molecule. These characteristics make it highly applicable to electronic devices that take advantage of their electric character, for imide group-based supramolecular materials that utilize hydrogen bonding, or for sensing materials with a combination of functional groups. Water-soluble NDI binds to a DNA duplex via the threading intercalation mode. Such NDI has enabled the development of unique DNA analytical techniques, functional DNA polymers, and supramolecular polymers. A ferrocene-containing NDI, possessing electrochemically active sites, has been applied to an electrochemical gene detection system and utilized in the precision analysis of genes and single nucleotide polymorphisms. Recently, a DNA quadruplex was identified as one of the noncanonical DNA structures formed by a guanine quartet (G4). The latter serves as one of the control units of gene expression and is associated with cancer development. A stable complex was formed between electron-deficient NDI and the electron-rich G4 planes. Since the G4 stabilizer is recognized as an anticancer agent with relatively few side effects, NDI derivatives may serve as potential candidates for anticancer therapeutics or for designing a unique cancer-detection system. Water-soluble Naphthalene diimide (NDI) binds to the DNA duplex via threading intercalation mode. This has provided unique DNA analytical techniques, functional DNA polymers, and supramolecular polymers. Especially the ferrocene-containing NDIs, having electrochemically active sites, has been applied to an electrochemical gene detection system and also utilized in the precision analysis of genes and single nucleotide polymorphisms. Recently, NDI derivatives have been recognizing as potential candidate for anticancer therapeutics and for designing a unique cancer-detection system.

Point-of-use sweat biosensor to track the endocrine-inflammation relationship for chronic disease monitoring.

Aim:The hypothalamic–pituitary–adrenal axis is involved in maintaining homeostasis by engaging with the parasympathetic nervous system. During the process of disease affliction, this relationship is disturbed and there is an imbalance driven response observed.Materials & methods:By monitoring the two key components involved in these pathways, cortisol and TNF-α, the manifestations of chronic stress on the body’s homeostasis can be evaluated in a comprehensive manner. This work highlights the development of an electrochemical detection system for the two biomarkers through human sweat.Results:Limit of detection and dynamic ranges are 1 ng/ml, 1–200 ng/ml for cortisol and 1 pg/ml, 1–1000 pg/ml for TNF-α.Conclusion:This wearable system is designed to be a point of use, chronic disease self-monitoring and management platform.

Ultrasensitive label-free detection for lung cancer CYFRA 21-1 DNA based on ring-opening polymerization

Cytokeratin fragment antigen 21-1 (CYFRA 21-1) DNA is perceived as sensitive tumor marker for the diagnosis of non-small cell lung cancer and other tumor. Herein, linear chain poly(ε-caprolactone) (PCL) synthesized by ring-opening polymerization is applied to ultrasensitive label-free electrochemical impedance detection system for CYFRA 21-1 DNA. First, thiolated peptide nucleic acid (PNA) is self-assembled into the Au electrode surface through the formation of Au–S bonds, allowing the PNA to act as biomolecular probe and form PNA/DNA heteroduplex with the target DNA via specific hybridization. Then, PCL is conjugated to the immobilized DNA on the electrode via “carboxylate–Zr4+–phosphate” bridges. Finally, the electrochemical response of modified PNA/DNA/Zr4+/PCL electrode is determined by electrochemical impedance method to quantify of CYFRA 21-1 DNA. Under optimal conditions, this method exhibits highly sensitivity with a broad linear range (0.1 fM – 1 nM) (R2 = 0.995) and the limit of detection (LOD) is as low as 10.73 aM, which is equivalent to just 64 molecules in a 10 μL sample. What's more, the high selectivity, good anti-interference, label-free operation, and real-time monitoring in complex samples of the proposed strategy demonstrate its broad application for the early diagnosis and clinical monitoring.

Two-signal electrochemical detection system for evaluation viability of Staphylococcus aureus

Establishment of new method for evaluation microbial viability has become an urgent need in the fields of biology, medicine, environment and so on. In this paper, two electrochemical signals of Staphylococcus aureus (S. aureus) at + 0.693 and + 0.973 V vs. Ag/AgCl (sat. KCl) were detected on the multi-walled carbon nanotube modified glassy carbon electrode (MWCNTs/GCE), and attributed to the oxidation of guanine and adenine secreted by S. aureus. For the first time, bacterial viability was evaluated from the perspective of proliferation and purine metabolism. Compared with the plate counting method, the electrochemical signals of guanine and adenine showed an earlier change of viability when S. aureus entered stationary from logarithmic phase and apoptotic from stationary phase during the growth process of S. aureus. There were good linear relationships between electrochemical signals of guanine and adenine and the number of S. aureus cells in different growth phases, but there were different detection thresholds. At the logarithmic phase, S. aureus had stronger viability and ability to metabolize purines, which resulted in a lower detection threshold. Both electrochemical signals of bacteria could well reflect the inhibition of levofloxacin on S. aureus viability, and the guanine signal peak was closer to the result of plate counting method.

Electrochemical Performance of Micropillar Array Electrodes in Microflows.

The microchip-based electrochemical detection system (μEDS) has attracted plenty of research attention due to its merits including the capability in high-density integration, high sensitivity, fast analysis time, and reduced reagent consumption. The miniaturized working electrode is usually regarded as the core component of the μEDS, since its characteristic directly determines the performance of the whole system. Compared with the microelectrodes with conventional shapes such as the band, ring and disk, the three-dimensional (3D) micropillar array electrode (μAE) has demonstrated significant potential in improving the current response and decreasing the limits of detection due to its much larger reaction area. In this study, the numerical simulation method was used to investigate the performance of the μEDS, and both the geometrical and hydrodynamic parameters, including the micropillars shape, height, arrangement form and the flow rate of the reactant solution, were taken into consideration. The tail effect in μAEs was also quantitatively analyzed based on a pre-defined parameter of the current density ratio. In addition, a PDMS-based 3D μAE was fabricated and integrated into the microchannel for the electrochemical detection. The experiments of cyclic voltammetry (CV) and chronoamperometry (CA) were conducted, and a good agreement was found between the experimental and simulation results. This study would be instructive for the configuration and parameters design of the μEDS, and the presented method can be adopted to analyze and optimize the performance of nanochip-based electrochemical detection system (nEDS).

Cancer Cell Detection‐Based on Released Hydrogen Peroxide Using a Non‐Modified Closed Bipolar Electrochemical System

AbstractIn this study, a non‐modified closed bipolar electrochemical system for ultrasensitive cancer cell detection by quantitative measurement of released hydrogen peroxide in the presence of ascorbic acid has been developed. This system includes two separate chambers (reporting and sensing), a piece of a gold archival CD (compact disc) as a bipolar electrode, and two platinum driving electrodes. By following the ECL (electrochemiluminescence) intensities of luminol oxidation in the reporting chamber, the hydrogen peroxide released by cancer cells in the presence of ascorbic acid was monitored. Under the optimum conditions, the biosensor delivers a wide linear range from 2.5×10−9 to 1×10−6 M, and a detection limit for hydrogen peroxide as low as 1.8×10−9 M. Also, this system can detect cancer blood cell concentrations (CCRF‐CEM: T‐lymphoblastic leukemia cell line) as low as 12 cells in 300 μL of cell suspension. The present bipolar electrode‐electrochemiluminescence (BPE‐ECL) system demonstrates a simple and low‐cost device with excellent performance without any electrode surface modification for the detection of cancer cells based on different levels of released hydrogen peroxide by normal and cancer cells. The present biosensor can be applied as a promising alternative method for the detection of H2O2 in the field of pathology, cancer diagnosis, and environmental monitoring.

Smartphone-Based Electrochemical Potentiostat Detection System Using PEDOT: PSS/Chitosan/Graphene Modified Screen-Printed Electrodes for Dopamine Detection.

In this work, a smartphone-based electrochemical detection system was designed and developed for rapid and real-time detection of dopamine (DA). The system included a screen-printed electrode (SPE) used as a sensor, a hand-held electrochemical potentiostat and a smart phone with a specially designed app. During the detection period, the SPEs modified with poly(3,4-ethylenedioxythiophene) (PEDOT), chitosan (CS) and graphene (G) were used to convert and amplify the electrochemical reaction signals. The electrochemical potentiostat was used to generate excitation electrical signals and collect the electrical signals converted from the sensor. The smartphone—connected to the detector via Bluetooth-was used to control the detector for tests, further process the uploaded data, and plot graphs in real time. Experimental results showed that the self-designed sensing system could be employed for highly selective detection of DA in the presence of interfering substances such as ascorbic acid (AA) and uric acid (UA). CV was carried out to characterize the electrochemical properties of the modified SPEs and the electrochemical behaviors of DA on the modified SPEs. Finally, according to the analysis of DPV responses of DA, the system could detect DA with a detection sensitivity of 0.52 ± 0.01 μA/μM and a limit of detection of 0.29 μM in the linear range of DA concentrations from 0.05 to 70 μM.

Multicenter Evaluation of a PCR-Based Digital Microfluidics and Electrochemical Detection System for the Rapid Identification of 15 Fungal Pathogens Directly from Positive Blood Cultures.

Routine identification of fungal pathogens from positive blood cultures by culture-based methods can be time-consuming, delaying treatment with appropriate antifungal agents. The GenMark Dx ePlex investigational use only blood culture identification fungal pathogen panel (BCID-FP) rapidly detects 15 fungal targets simultaneously in blood culture samples positive for fungi by Gram staining. We aimed to determine the performance of the BCID-FP in a multicenter clinical study. Blood culture samples collected at 10 United States sites and tested with BCID-FP at 4 sites were compared to the standard-of-care microbiological and biochemical techniques, fluorescence in situ hybridization using peptide nucleic acid probes (PNA-FISH) and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Discrepant results were analyzed by bi-directional PCR/sequencing of residual blood culture samples. A total of 866 clinical samples, 120 retrospectively and 21 prospectively collected, along with 725 contrived samples were evaluated. Sensitivity and specificity of detection of Candida species (C. albicans, C. auris, C. dubliniensis, C. famata, C. glabrata, C. guilliermondii, C. kefyr, C. krusei, C. lusitaniae, C. parapsilosis, and C. tropicalis) ranged from 97.1 to 100% and 99.8 to 100%, respectively. For the other organism targets, sensitivity and specificity were as follows: 100% each for Cryptococcus neoformans and C. gattii, 98.6% and 100% for Fusarium spp., and 96.2% and 99.9% for Rhodotorula spp., respectively. In 4 of the 141 clinical samples, the BCID-FP panel correctly identified an additional Candida species, undetected by standard-of-care methods. The BCID-FP panel offers a faster turnaround time for identification of fungal pathogens in positive blood cultures that may allow for earlier antifungal interventions and includes C. auris, a highly multidrug-resistant fungus.

Coupling of Anodic Stripping Voltammetry with Sampled-Current Voltammetry on an Electrode Array: Application to Lead Detection

Electrochemical detection systems are very promising for pollution monitoring owing to their easy miniaturization and low cost. For this purpose, we have recently developed a new concept of device based on Electrodes Array for Sampled-Current Voltammetry (EASCV), which is compatible with miniaturization and portability. In this work, to improve the sensitivity of the analytical method, we added a preconcentration step before EASCV analysis, combining sampled-current voltammetry with anodic stripping voltammetry. Lead was chosen as analyte for this probe of concept owing to its high toxicity. The conditions for electrodeposition of lead on gold were optimized by means of under potential deposition. Current intensities 300 times higher than with linear sweep anodic stripping voltammetry were obtained, showing the interest in the method. The value of the sampling time directly affected the sensitivity of the sensor given by the slope of the linear calibration curve. The sensor exhibited a limit of detection of 1.16 mg L−1, similar to those obtained with linear sweep anodic stripping voltammetry.