Saliva represents one of the most useful biological samples for non-invasive testing of health status and diseases prognosis and therefore, the development of advanced sensors enabling the determination of biomarkers in unspiked human whole saliva is of immense importance. Herein, we report on the development of a screen-printed graphite sensor modified with carbon nanomaterials generated by spark discharge for the determination of guanine and adenine in unspiked human whole saliva. The designed sensor was developed with a "green", extremely simple, fast (16 s), fully automated "linear mode" sparking process implemented with a 2D positioning device. Carbon nanomaterial-modified surfaces exhibit outstanding electrocatalytic properties enabling the determination of guanine and adenine over the concentration range 5 - 1000 nM and 25 - 1000 nM, while achieving limits of detection (S/N 3) as low as 2 nM and 8 nM, respectively. The sensor was successfully applied to the determination of purine bases in unspiked human whole saliva following a simple assay protocol based on ultrafiltration that effectively alleviates biofouling issues. Recovery was 96-108%.
- MeSH
- Adenine MeSH
- Electrochemical Techniques MeSH
- Electrodes MeSH
- Graphite * MeSH
- Guanine MeSH
- Humans MeSH
- Saliva MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Synthetic food colorants are extensively used across the globe regardless of the fact that they induce deleterious side effects when used in higher amounts. In this work, a novel electrochemical sensor based on nickel nanoparticles doped lettuce-like Co3O4 anchored graphene oxide (GO) nanosheets was developed for effective detection of sulfonated azo dye sunset yellow widely used as a food colorant. Hydrothermal synthesis was adopted for the preparation of lettuce-like spinel Co3O4 nanoparticles and Ni-Co3O4 NPs/GO nanocomposite was prepared using ecofriendly and economical sonochemical method. The prepared ternary nanocomposite meticulously fabricated on a screen-printed carbon electrode exhibited remarkable electrocatalytic activity towards sunset yellow determination. This is apparent from the resultant well-defined and intense redox peak currents of Ni-Co3O4 NPs/GO nanocomposite modified electrode at very low potentials. The developed sunset yellow sensor exhibited a high sensitivity of 4.16 μA μM-1 cm-2 and a nanomolar detection limit of 0.9 nM in the linear range 0.125-108.5 μM. Furthermore, experiments were conducted to affirm excellent stability, reproducibility, repeatability, and selectivity of proposed sensor. The practicality of sunset yellow determination using the developed sensor was analyzed in different varieties of food samples including jelly, soft drink, ice cream, and candy resulting in recovery in the range of 96.16%-102.56%.
- MeSH
- Azo Compounds analysis MeSH
- Electrochemical Techniques methods MeSH
- Graphite MeSH
- Cobalt chemistry MeSH
- Metal Nanoparticles chemistry MeSH
- Limit of Detection MeSH
- Linear Models MeSH
- Nanocomposites chemistry MeSH
- Nickel chemistry MeSH
- Aluminum Oxide chemistry MeSH
- Magnesium Oxide chemistry MeSH
- Oxides chemistry MeSH
- Food Coloring Agents analysis MeSH
- Reproducibility of Results MeSH
- Publication type
- Journal Article MeSH
With the increased demand for beef in emerging markets, the development of quality-control diagnostics that are fast, cheap and easy to handle is essential. Especially where beef must be free from pork residues, due to religious, cultural or allergic reasons, the availability of such diagnostic tools is crucial. In this work, we report a label-free impedimetric genosensor for the sensitive detection of pork residues in meat, by leveraging the biosensing capabilities of graphene acid - a densely and selectively functionalized graphene derivative. A single stranded DNA probe, specific for the pork mitochondrial genome, was immobilized onto carbon screen-printed electrodes modified with graphene acid. It was demonstrated that graphene acid improved the charge transport properties of the electrode, following a simple and rapid electrode modification and detection protocol. Using non-faradaic electrochemical impedance spectroscopy, which does not require any electrochemical indicators or redox pairs, the detection of pork residues in beef was achieved in less than 45 min (including sample preparation), with a limit of detection of 9% w/w pork content in beef samples. Importantly, the sample did not need to be purified or amplified, and the biosensor retained its performance properties unchanged for at least 4 weeks. This set of features places the present pork DNA sensor among the most attractive for further development and commercialization. Furthermore, it paves the way for the development of sensitive and selective point-of-need sensing devices for label-free, fast, simple and reliable monitoring of meat purity.
- MeSH
- Biosensing Techniques * MeSH
- DNA MeSH
- Electrochemical Techniques MeSH
- Electrodes MeSH
- Graphite * MeSH
- Meat MeSH
- Cattle MeSH
- Animals MeSH
- Check Tag
- Cattle MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
New screen-printed sensor with a boron-doped diamond working electrode (SP/BDDE) was fabricated using a large-area linear antenna microwave chemical deposition vapor system (LA-MWCVD) with a novel precursor composition. It combines the advantages of disposable printed sensors, such as tailored design, low cost, and easy mass production, with excellent electrochemical properties of BDDE, including a wide available potential window, low background currents, chemical resistance, and resistance to passivation. The newly prepared SP/BDDEs were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Their electrochemical properties were investigated by cyclic voltammetry and electrochemical impedance spectroscopy using inner sphere ([Fe(CN)6]4-/3-) and outer sphere ([Ru(NH3)6]2+/3+) redox probes. Moreover, the applicability of these new sensors was verified by analysis of the anti-inflammatory drug lornoxicam in model and pharmaceutical samples. Using optimized differential pulse voltammetry in Britton-Robinson buffer of pH 3, detection limits for lornoxicam were 9 × 10-8 mol L-1. The oxidation mechanism of lornoxicam was investigated using bulk electrolysis and online electrochemical cell with mass spectrometry; nine distinct reaction steps and corresponding products and intermediates were identified.
- MeSH
- Boron * chemistry MeSH
- Electrodes MeSH
- Electrolysis * MeSH
- Oxidation-Reduction MeSH
- Spectrum Analysis, Raman MeSH
- Publication type
- Journal Article MeSH
The review describes fentanyl and its analogs as new synthetic opioids and the possibilities of their identification and determination using electrochemical methods (e.g., voltammetry, potentiometry, electrochemiluminescence) and electrochemical methods combined with various separation methods. The review also covers the analysis of new synthetic opioids, their parent compounds, and corresponding metabolites in body fluids, such as urine, blood, serum, and plasma, necessary for a fast and accurate diagnosis of intoxication. Identifying and quantifying these addictive and illicit substances and their metabolites is necessary for clinical, toxicological, and forensic purposes. As a reaction to the growing number of new synthetic opioid intoxications and increasing fatalities observed over the past ten years, we provide thorough background for developing new biosensors, screen-printed electrodes, or other point-of-care devices.
- MeSH
- Fentanyl * MeSH
- Analgesics, Opioid * MeSH
- Publication type
- Journal Article MeSH
- Review MeSH
Objective.Understanding how the retina converts a natural image or an electrically stimulated one into neural firing patterns is the focus of on-going research activities.Ex vivo, the retina can be readily investigated using multi electrode arrays (MEAs). However, MEA recording and stimulation from an intact retina (in the eye) has been so far insufficient.Approach.In the present study, we report new soft carbon electrode arrays suitable for recording and stimulating neural activity in an intact retina. Screen-printing of carbon ink on 20μm polyurethane (PU) film was used to realize electrode arrays with electrodes as small as 40μm in diameter. Passivation was achieved with a holey membrane, realized using laser drilling in a thin (50μm) PU film. Plasma polymerized 3.4-ethylenedioxythiophene was used to coat the electrode array to improve the electrode specific capacitance. Chick retinas, embryonic stage day 13, both explanted and intact inside an enucleated eye, were used.Main results.A novel fabrication process based on printed carbon electrodes was developed and yielded high capacitance electrodes on a soft substrate.Ex vivoelectrical recording of retina activity with carbon electrodes is demonstrated. With the addition of organic photo-capacitors, simultaneous photo-electrical stimulation and electrical recording was achieved. Finally, electrical activity recordings from an intact chick retina (inside enucleated eyes) were demonstrated. Both photosensitive retinal ganglion cell responses and spontaneous retina waves were recorded and their features analyzed.Significance.Results of this study demonstrated soft electrode arrays with unique properties, suitable for simultaneous recording and photo-electrical stimulation of the retina at high fidelity. This novel electrode technology opens up new frontiers in the study of neural tissuein vivo.
- MeSH
- Electric Stimulation methods MeSH
- Microelectrodes MeSH
- Retina * physiology MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The detection of cancer antigens is a major aim of cancer research in order to develop better patient management through early disease detection. Many cancers including prostate, lung, and ovarian secrete a protein disulfide isomerase protein named AGR2 that has been previously detected in urine and plasma using mass spectrometry. Here we determine whether a previously developed monoclonal antibody targeting AGR2 can be adapted from an indirect two-site ELISA format into a direct detector using solid-phase printed gold electrodes. The screen-printed gold electrode was surface functionalized with the anti-AGR2 specific monoclonal antibody. The interaction of the recombinant AGR2 protein and the anti-AGR2 monoclonal antibody functionalized electrode changed its electrochemical impedance spectra. Nyquist diagrams were obtained after incubation in an increasing concentration of purified AGR2 protein with a range of concentrations from 0.01 fg/mL to 10 fg/mL. In addition, detection of the AGR2 antigen can be achieved from cell lysates in medium or artificial buffer. These data highlight the utility of an AGR2-specific monoclonal antibody that can be functionalized onto a gold printed electrode for a one-step capture and quantitation of the target antigen. These platforms have the potential for supporting methodologies using more complex bodily fluids including plasma and urine for improved cancer diagnostics.
- MeSH
- Biosensing Techniques * MeSH
- Electrochemical Techniques MeSH
- Electrodes MeSH
- Metal Nanoparticles MeSH
- Humans MeSH
- Limit of Detection MeSH
- Antibodies, Monoclonal MeSH
- Mucoproteins analysis MeSH
- Neoplasms MeSH
- Oncogene Proteins analysis MeSH
- Gold MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Leptospirosis is an underestimated tropical disease caused by the pathogenic Leptospira species and responsible for several serious health problems. Here, we aimed to develop an ultrasensitive DNA biosensor for the rapid and on-site detection of the Loa22 gene of Leptospira interrogans using a gold nanoparticle-carbon nanofiber composite (AuN/CNF)-based screen-printed electrode. Cyclic voltammetry and electrochemical impedance were performed for electrochemical analysis. The sensitivity of the sensor was 5431.74 μA/cm2/ng with a LOD (detection limit) of 0.0077 ng/μL using cyclic voltammetry. The developed DNA biosensor was found highly specific to the Loa22 gene of L. interrogans, with a storage stability at 4 °C for 180 days and a 6% loss of the initial response. This DNA-based sensor only takes 30 min for rapid detection of the pathogen, with a higher specificity and sensitivity. The promising results obtained suggest the application of the developed sensor as a point of care device for the diagnosis of leptospirosis.
- MeSH
- Metal Nanoparticles * MeSH
- Leptospira interrogans * genetics MeSH
- Leptospirosis * diagnosis MeSH
- Humans MeSH
- Membrane Proteins MeSH
- Gold MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
This paper reports a simple electrochemical strategy for the determination of microRNAs (miRNAs) using a commercial His-Tag-Zinc finger protein (His-Tag-ZFP) that binds preferably (but non-sequence specifically) RNA hybrids over ssRNAs, ssDNAs, and dsDNAs. The strategy involves the use of magnetic beads (His-Tag-Isolation-MBs) as solid support to capture the conjugate formed in homogenous solution between His-Tag-ZFP and the dsRNA homohybrid formed between the target miRNA (miR-21 selected as a model) and a biotinylated synthetic complementary RNA detector probe (b-RNA-Dp) further conjugated with a streptavidin-horseradish peroxidase (Strep-HRP) conjugate. The electrochemical detection is carried out by amperometry at disposable screen-printed carbon electrodes (SPCEs) (- 0.20 V vs Ag pseudo-reference electrode) upon magnetic capture of the resultant magnetic bioconjugates and H2O2 addition in the presence of hydroquinone (HQ). The as-prepared biosensor exhibits a dynamic concentration range from 3.0 to 100 nM and a detection limit (LOD) of 0.91 nM for miR-21 in just ~ 2 h. An acceptable discrimination was achieved between the target miRNA and other non-target nucleic acids (ssDNA, dsDNA, ssRNA, DNA-RNA, miR-122, miR-205, and single central- or terminal-base mismatched sequences). The biosensor was applied to the analysis of miR-21 from total RNA (RNAt) extracted from epithelial non-tumorigenic and adenocarcinoma breast cells without target amplification, pre-concentration, or reverse transcription steps. The versatility of the methodology due to the ZFP's non-sequence-specific binding behavior makes it easily extendable to determine any target RNA only by modifying the biotinylated detector probe.
A new electroanalytical methodology was developed for the sensitive and selective determination of formaldehyde in wood-based products (WBPs), featuring an extraction process using a Headspace Liquid Acceptor System (HLAS), and detection by square-wave voltammetry (SWV) on unmodified screen-printed carbon electrodes (SPCEs). HLAS, here presented for the first time, captures and derivatizes formaldehyde released from the sample by using the acetylacetone reagent as acceptor solution. The product of formaldehyde with acetylacetone, in the presence of ammonium salt, is 3,5-diacetyl-1,4-dihydrolutidine (DDL) which we have found to be electrochemically active at unmodified SPCEs, generating a selective oxidation peak at +0.4 V. Detection and quantification limits of 0.57 and 1.89 mg kg-1 were obtained, together with intra- and inter-day precisions below 10% (as relative standard deviation, RSD). The methodology was used to determine formaldehyde content in seven WBPs, with similar results being obtained by the developed HLAS-SPCE method and the European standard method EN 717-3, with a profound reduction of total analysis time. The developed HLAS-SPCE combines the use of a new sample preparation procedure for volatiles with, as far as we know, the first determination of formaldehyde (as the derivative product, DDL) on unmodified SPCEs, offering a promising alternative for the determination of formaldehyde in WBPs and other samples.
- Publication type
- Journal Article MeSH
