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In this paper we report on a modular design that allows one to fabricate electrochemical sensors upon combining 3D printing and screen printing. The usefulness of the design is showcased with graphene paste electrodes (GPE) coated with magnetic microspheres used to detect the drug nimesulide (NIM), biomarkers dopamine (DOP) and uric acid (UA). Under optimized conditions, the limit of detection was 0.0023 μmol L−1 in the range from 0.5 to 9 μmol L−1, 0.01 μmol L−1 within the range from 0.8 to 6 μmol L−1, and 0.0034 μmol L−1 from 0.7 to 10 μmol L−1 for dopamine, nimesulide, and uric acid, respectively. The three analytes could also be detected in blood serum and artificial urine samples within approximately 20 s, which is promising for clinical applications. With the modular design, the paste can be prepared with a variety of nanomaterials, functionalized with biomolecules and magnetic particles, and then stored for later use. The working electrode may also be polished to allow for reuse. Furthermore, in contrast to standard sensors made with carbon pastes, the electrochemical sensor proposed here requires small volumes (20–200 μL), which is crucial for drug monitoring and other biomedical applications.

Alzheimer's disease (AD) is a neurodegenerative condition that affects a large number of elderly people worldwide and has a high social and economic impact. The diagnosis of AD in early stage can significantly improve the evolution and prognosis of the disease. We report the use of A Disintegrin And Metalloprotease 10 (ADAM10) as a blood biomarker for the early diagnosis of AD. A simple, low-cost, sensitive, and disposable microfluidic platform (DμP) was developed for ADAM10 detection in plasma and cerebrospinal fluid based on electrochemical immunosensors. The assay was designed to accurately detect ADAM10 in serum, with a limit of detection of 0.35 fg/mL. ADAM10 was detected in subjects divided into cognitively healthy subjects, subjects with mild cognitive impairment, and AD patients in different disease stages. An increase in protein levels was found throughout the disease, and good DμP accuracy in differentiating individuals was observed. The DμP provided significantly better sensitivity than the well-established enzyme-linked immunosorbent assay test. ADAM10 and its detection using the DμP were proven to be an alternative tool for the early diagnosis and monitoring of AD, bringing new exciting possibilities to improve the quality of life of AD patients.

The outbreak of the COVID-19 pandemic, caused by Severe Acute Respiratory Syndrome of Coronavirus 2 (SARS-CoV-2), has fueled the search for diagnostic tests aiming at the control and reduction of the viral transmission. The main technique used for diagnosing the Coronavirus disease (COVID-19) is the reverse transcription-polymerase chain reaction (RT-PCR) technique. However, considering the high number of cases and the underlying limitations of the RT-PCR technique, especially with regard to accessibility and cost of the test, one does not need to overemphasize the need to develop new and less expensive testing techniques that can aid the early diagnosis of the disease. With that in mind, we developed an ultrasensitive magneto-assay using magnetic beads and gold nanoparticles conjugated to human angiotensin-converting enzyme 2 (ACE2) peptide (Gln24-Gln42) for the capturing and detection of SARS-CoV-2 Spike protein in human saliva. The technique applied involved the use of a disposable electrochemical device containing eight screen-printed carbon electrodes which allow the simultaneous analysis of eight samples. The magneto-assay exhibited an ultralow limit of detection of 0.35 ag mL−1 for the detection of SARS-CoV-2 Spike protein in saliva. The magneto-assay was tested in saliva samples from healthy and SARS-CoV-2-infected individuals. In terms of efficiency, the proposed technique – which presented a sensitivity of 100.0% and specificity of 93.7% for SARS-CoV-2 Spike protein-exhibited great similarity with the RT-PCR technique. The results obtained point to the application potential of this simple, low-cost magneto-assay for saliva-based point-of-care COVID-19 diagnosis., Graphical Abstract ga1

Diagnosis of cancer using electroanalytical methods can be achieved at low cost and in rapid assays, but this may require the combination with data treatment for determining biomarkers in real samples. In this paper, we report an immunomagnetic nanoparticle-based microfluidic sensor (INμ-SPCE) for the amperometric detection of the prostate-specific antigen (PSA) biomarker, the data of which were treated with information visualization methods. The INμ-SPCE consists of eight working electrodes, reference and counter electrodes. On the working electrodes, magnetic nanoparticles with secondary antibodies with the enzyme horseradish peroxidase were immobilized for the indirect detection of PSA in a sandwich-type procedure. Under optimal conditions, the immunosensor could operate within a wide range from 12.5 to 1111 fg·L−1, with a low detection limit of 0.062 fg·L−1. Multidimensional projections combined with feature selection allowed for the distinction of cell lysates with different levels of PSA, in agreement with results from the traditional enzyme-linked immunosorbent assay. The approaches for immunoassays and data processing are generic, and therefore the strategies described here may provide a simple platform for clinical diagnosis of cancers and other types of diseases.

A disposable microfluidic electrochemical paper-based device for multiplexed analysis based on sixteen independent microfluidic channels with electrochemical detection is proposed. A major advantage of this work was the non-necessary use of a wax printer for devices manufacturing which has a high cost of operation. In addition, a commercial multiplexing module was used that has the multiplexing capability of 8–16 channels and, for the first time using this module, the strategy of multiplexing both the working and reference electrodes were used. These sixteen channels with the respective sensors can be operated employing one or multiple electrochemical techniques with good repeatability and reproducibility for high throughput analysis. As a proof of concept, the electrochemical performance of device was tested with ferrocenecarboxylic acid solution employing cyclic voltammetry, square-wave voltammetry, differential-pulse voltammetry and chronoamperometry. This innovative sensing platform presented capacity of production in large scale and application for clinical tests with safety and short time of assays. A biosensor was constructed using glucose oxidase on the platform for the glucose determination in urine as a non-invasive strategy. The analytical curve was linear in the glucose concentration range from 1.0 × 10−4 mol L−1 to 4 × 10−2 mol L−1, with a limit of detection of 3 × 10−5 mol L−1.

Early diagnosis of cancer by biomarker detection has been widely studied since it can lead to an increase in patient survival rates. Magnetic nanoparticles (MNPs) play an important role in this field acting as a valuable tool in the biomarker immunocapture and detection. In this work, Co0.25Zn0.75Fe2O4 (CoZnFeONPs) nanoparticles were synthesized and applied as enzyme mimics of peroxidase-like catalysis in a disposable enzyme-free microfluidic immunoarray device (μID). The catalytic activity of CoZnFeONPs was evaluated by hydrogen peroxide detection using cyclic voltammetry and the apparent Michaelis-Menten constant was estimated by Lineweaver–Burk equation showing good Km values. In μID, the immunosensors were assembled with monoclonal antibody against CYFRA 21-1 covalently immobilized on graphene oxide previously deposited on the screen-printed carbon-based electrodes. Under optimized conditions, the method presented a good linear response for CYFRA 21-1 in the range of 3.9–1000 fg mL−1 achieving an ultralow limit of detection (LOD) of 0.19 fg mL−1. For comparison, Fe3O4 nanoparticles (FeONPs) was also synthetized and presented results slight inferior to that obtained with CoZnFeONPs. The methods developed using both MNPs exhibited countless advantages when compared with the immunosensors developed for CYFRA-21-1, previously reported in the literature. The methods were successful applied for the detection of CYFRA 21-1 in real serum samples of healthy and prostate cancer patients and showed good correlation with results obtained with the enzyme-linked immunosorbent assay (ELISA). The CoZnFeONPs associated with the disposable microfluidic immunoarray device provides a simple and effective method for biomarker detection that could satisfy the need for a low-cost and rapid test for early diagnosis of cancer.

This paper describes a simple, low-cost, and highly flexible rapid prototyping method to construct electrochemical paper-based analytical device (ePAD) for multiplexed analyte determinations. The ePAD was composed of two electrochemical cell (EC) compartments, separated by hydrophobic barriers of wax, and screen-printed electrodes (SPEs) deposited directly over the surface of the filter paper. The ePAD was entirely constructed using an inexpensive craft cutter printer with no needed of a wax printer. The rapid prototyping method involves two steps: the deposition of the SPEs and the creation of the wax barriers. In this case, the SPEs were screen-printed on filter paper by using adhesive tape as mask by cutting the electrodes pattern with the cutter printer. Following, the wax barriers were created using stamps made of filter paper also cut with the printer and impregnated with wax. In the ePAD, each ECs containing an array of 4-working electrodes, allowing up to 4 replicates in a single measurement. Both ECs shared one counter and one reference electrodes, permitting the simultaneous multianalysis. The ePAD was successfully applied to simultaneous detection of paracetamol (PAR), caffeine (CAF), and ascorbic acid (AA) in drugs. PAR and CAF were detected in a sample using one EC and AA was detected, in a different sample, on the other EC, both with no chemical modifications in the working electrodes. Limits of detection of 0.04 mmol L−1 for PAR, 0.22 mmol L−1 for CAF, and 0.40 mmol L−1 for AA were obtained. The construction process proposed provide an easy way to implement screen-printing electrodes and wax barriers in filter paper to create electrochemical devices for fast and simultaneous multianalysis.

Monitoring the concentration of antibiotics in body fluids is essential to optimizing the therapy and minimizing the risk of bacteria resistance, which can be made with electrochemical sensors tailored with appropriate materials. In this paper, we report on sensors made with screen-printed electrodes (SPE) coated with fullerene (C60), reduced graphene oxide (rGO) and Nafion (NF) (C60-rGO-NF/SPE) to determine the antibiotic metronidazole (MTZ). Under optimized conditions, the C60-rGO-NF/SPE sensor exhibited a linear response in square wave voltammetry for MTZ concentrations from 2.5 × 10−7 to 34 × 10−6 mol/L, with a detection limit of 2.1 × 10−7 mol/L. This sensor was also capable of detecting MTZ in serum and urine, with recovery between 94% and 100%, which are similar to those of the standard chromatographic method (HPLC-UV). Because the C60-rGO-NF/SPE sensor is amenable to mass production and allows for MTZ determination with simple principles of detection, it fulfills the requirements of therapeutic drug monitoring programs., Graphical abstract Image 1, Highlights • Determination of metronidazole (MTZ) in urine and synthetic serum sample. • The MTZ is a synthetic antibiotic widely used for surgical prophylaxis, in patients with burn wounds and other pathologies. • The detection of MTZ is relevant to minimize its side effects and avoid acquired resistance. • We employed fullerene C60-rGO and nafion in low-cost screen-printed electrode (SPE). • Electrochemical sensor is amenable to mass production.

Boron nitride allotropes are 2D nanomaterials with hexagonal form, sometimes referred to as “white graphene.” In contrast to graphene, boron nitride is a dielectric material with a well-defined energy gap, being therefore suitable for several electronic devices. Its use in sensors and biosensors has been relatively little explored though. In this chapter, we present the recent advances of 2D boron nitride nanomaterials as sensors and biosensors. Surface functionalization and combination with other nanomaterials are key for tuning the sensitivity and selectivity of boron nitride-based sensors. One of the main challenges to extend applications of boron nitride and its composites is the identification of reaction mechanisms responsible for detection, which is being pursued by several research groups using first-principle calculations. With the wide variability of properties that can be obtained via functionalization, the discovery of new boron nitride composites suitable for target analytes may be performed in the near future with machine learning and other artificial intelligence approaches.

The inability to distinguish aggressive from indolent prostate cancer is a longstanding clinical problem. Prostate specific antigen (PSA) tests and digital rectal exams cannot differentiate these forms. Because only ∼10% of diagnosed prostate cancer cases are aggressive, existing practice often results in overtreatment including unnecessary surgeries that degrade patients' quality of life. Here, we describe a fast microfluidic immunoarray optimized to determine 8-proteins simultaneously in 5 μL of blood serum for prostate cancer diagnostics. Using polymeric horseradish peroxidase (poly-HRP, 400 HRPs) labels to provide large signal amplification and limits of detection in the sub-fg mL-1 range, a protocol was devised for the optimization of the fast, accurate assays of 100-fold diluted serum samples. Analysis of 130 prostate cancer patient serum samples revealed that some members of the protein panel can distinguish aggressive from indolent cancers. Logistic regression was used to identify a subset of the panel, combining biomarker proteins ETS-related gene protein (ERG), insulin-like growth factor-1 (IGF-1), pigment epithelial-derived factor (PEDF), and serum monocyte differentiation antigen (CD-14) to predict whether a given patient should be referred for biopsy, which gave a much better predictive accuracy than PSA alone. This represents the first prostate cancer blood test that can predict which patients will have a high biopsy Gleason score, a standard pathology score used to grade tumors.

Extracellular vesicles (EVs) are a frontier class of circulating biomarkers for the diagnosis and prognosis of different diseases. These lipid structures afford various biomarkers such as the concentrations of the EVs (CV) themselves and carried proteins (CP). However, simple, high-throughput, and accurate determination of these targets remains a key challenge. Herein, we address the simultaneous monitoring of CV and CP from a single impedance spectrum without using recognizing elements by combining a multidimensional sensor and machine learning models. This multidetermination is essential for diagnostic accuracy because of the heterogeneous composition of EVs and their molecular cargoes both within the tumor itself and among patients. Pencil HB cores acting as electric double-layer capacitors were integrated into a scalable microfluidic device, whereas supervised models provided accurate predictions, even from a small number of training samples. User-friendly measurements were performed with sample-to-answer data processing on a smartphone. This new platform further showed the highest throughput when compared with the techniques described in the literature to quantify EVs biomarkers. Our results shed light on a method with the ability to determine multiple EVs biomarkers in a simple and fast way, providing a promising platform to translate biofluid-based diagnostics into clinical workflows.

A fast and simple magnetogenoassay is proposed for diagnosis of metastatic lymph nodes in patients with head and neck squamous cell carcinoma (HNSCC). The developed method involved the construction of a low-cost disposable electrochemical sensor (DES) for the detection of microRNA-203 (miRNA-203) as a biomarker in lymph node samples from patients with HNSCC. A hairpin DNA designed for selectively binding the miRNA-203 was immobilized in magnetic particles (MPs) and used to capture and separate the biomarker from the sample solution. Gold nanoparticles (AuNPs) decorated with single-stranded DNA with a sequence complementary to the hairpin terminal section were prepared and used for biomarker detection. The miRNA-203 magneto-bioconjugate obtained was added to the DES and the biomarker was quantitatively determined by means of the redox properties of the gold present in the AuNPs, using square-wave voltammetry in 0.2 mol L-1 HCl. The proposed method presented a linear range from 1.0 to 500.0 fmol L−1, with a limit of detection of 0.52 fmol L−1. The magnetogenoassay was able to detect the miRNA-203 in 90 min, showing similar results when compared with qRT-PCR for the discrimination of positive and negative metastatic lymph nodes from HNSCC patients. The proposed molecular test requires no amplification steps, offering an effective, simple, and fast alternative for the detection of microRNAs as biomarkers for cancer diagnosis.

Herein, we describe the construction of a simple, low-cost, and fully disposable microfluidic device (DμFD) for ultrasensitive Salmonella typhimurium ( S. typhi ) detection. The DμFD is based on unmodified carbon electrode array for rapid detection of S. typhi in milk samples by magneto-immunoassay using gold nanoparticles (AuNPs) as a label. In the method proposed, S. typhi was magnetically captured and separated from samples using magnetic beads modified with a monoclonal anti- Salmonella antibody followed by the addition of polyclonal anti- Salmonella antibody labeling with AuNPs. The magneto-immunoconjugate formed was injected into the DμFD and captured on the electrode surface by placing magnets behind the unmodified working electrodes. The S. typhi detection was carried out by the electrochemical response of the gold from AuNPs. A single DμFD was used for rapid and full S. typhi analysis by measuring standards and samples simultaneously. A low limit of detection (LOD) of 7.7 cells mL −1 for S. typhi in a linear range from 10.0 to 100.0 cells mL −1 was obtained. The DμFD proved to be fast, accurate, and inexpensive for S. typhi detection and has great potential to multiplex detection of different food contaminants.

Glutathione-s-transferase is believed to be involved in the resistance to chemotherapeutic drugs, which depends on the interaction with the cell membranes. In this study, we employed Langmuir monolayers of a mixture of phospholipids and cholesterol (MIX) as models for tumor cell membranes and investigated their interaction with the anticancer drugs cisplatin (CDDP) and doxorubicin (DOX). We found that both DOX and CDDP expand and affect the elasticity of MIX monolayers, but these effects are hindered when glutathione-s-transferase (GST) and its cofactor glutathione (GSH) are incorporated. Changes are induced by DOX or CDDP on the polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) data for MIX/GST/GSH monolayers, thus denoting some degree of interaction that is not sufficient to alter the monolayer mechanical properties. Overall, the results presented here give support to the hypothesis of the inactivation of DOX and CDDP by GST and point to possible directions to detect and fight drug resistance.

Food allergies have been increasing all over the world. Egg is an important component in the food industries and the second most common cause of food allergy, shortly after milk. In the wine industry, egg white is applied as a fining agent for tannin removal. In this study, a sandwich-based immunoassay for ultrasensitive detection of ovalbumin (OVA) in wine samples was developed. The assay involves the use of magnetic beads (MBs) decorated with a polyclonal anti-OVA antibody (Ab2) and horseradish peroxidase (HRP), used as label for the quantification in a disposable electrochemical microfluidic device (DEμD) here developed. The Ab2-MB-HRP prepared was applied to capture, separate, and pre-concentrate OVA from wine samples. In the DEμD, OVA was immune-magnetically captured (OVA-Ab2-MB-HRP), producing a sandwich structure (GO-Ab1-OVA-Ab2-MB-HRP) on the electrode's surface. This arrangement results in an ultrasensitive device, achieving the ultralow limit of detection of 0.2 fg mL−1 OVA. Five samples of wines were analyzed by using the immuno-magneto-assay which presents excellent accuracy compared with enzyme-linked immunosorbent assay (ELISA).

ArtinM, a D-mannose-binding lectin from Artocarpus heterophyllus (jackfruit), interacts with N-glycosylated receptors on the surface of several cells of hematopoietic origin, triggering cell migration, degranulation, and cytokine release. Because malignant transformation is often associated with altered expression of cell surface glycans, we evaluated the interaction of ArtinM with human myelocytic leukemia cells by Quartz Cristal Microbalance (QCM) and cross compared this investigation with cellular responses (cytotoxicity) to lectin binding by the colorimetric assay MTT, which is a standard method in biology. QCM analysis was able to provide additional information (not possible to be obtained by MTT) that impact on the knowledge of medical biology related to leukemic cells. For instance, it was shown that association rate constant of ArtinM and cellular membranes (obtained from QCM) of leukemia cell varies across the myeloid leukemia cell lines, decreasing as cytotoxic effect increases. Meanwhile no differences were observed for dissociation rate constants so that the equilibrium binding affinity constant was observed to be a direct function of the association rate event. It was supposed that ArtinM cytotoxicity is affected by the association time with glycans on the cellular membranes of leukemia cells in a way that the higher it is the association time (the lower was the association rate constant) the higher is the ArtinM cytotoxicity over the leukemia cell lines.

The rapid population growth and industrialization have led to widespread use of pesticides, drugs, personal care products, and dyes, some of which are so-called emerging contaminants (ECs). These compounds have obviously brought great benefits in controlling diseases and for increasing agricultural and industrial production, but their indiscriminate use has caused problems to human health and the environment. They can be found in surface water and groundwater at concentrations from ng L−1 to mg L−1, which may seem negligible. However, some contaminants can accumulate or transform in other more toxic products in the human body and induce such problems as antibiotic resistance. Unfortunately, since there is no regulation for some emerging contaminants, they are not monitored in the environment or cannot be detected with conventional analytical techniques.

A low-cost and disposable microcell was constructed with a screen-printed electrode for the non-enzymatic electrochemical determination of creatinine. The working electrode was modified with carbon black and maintained in contact with paper-adsorbed iron (III) ions. A small sample volume of 3 μL was required for the device operation. Then, iron (III) ions were complexed in the presence of creatinine in a chemical step, followed by an electrochemical reduction of non-complexed metallic ions in excess. Cyclic voltammetry and differential-pulse voltammetry experiments were employed for the electrochemical characterizations and analytical performance evaluation of the microcell. The working electrode modification with carbon black provided a significant increase of analytical signal. The sensor presented a linear response for creatinine concentrations ranging from 0.10 to 6.5 mmol L−1, with a limit of detection of 0.043 mmol L−1. Experiments for creatinine determination in real samples were successful performed through of standard recovery in urine.

Tristeza is a disease that affects citrus crops in general, caused by the Citrus tristeza virus (CTV). It is considered an economically important virus diseases in citrus, which is present in the main citrus producing regions all around the world. Early detection of CTV is crucial to avoid any epidemics and substantial economic losses for the citrus growers. Consequently, the development of rapid, accurate, and sensitive methods capable of detecting the virus in the early stages of the disease is highly desired. Based on that, a low-cost and rapid magneto-immunoassay methodology to detect the capsid protein from CTV (CP-CTV) was proposed. For this, magnetic beads were decorated with antibodies anti-CP-CTV and horseradish peroxidase enzyme (HRP) and applied for the capture and separation of CP-CTV from the sample solutions. The magnetically captured biomarker was detected using a simple disposable microfluidic electrochemical device (DμFED) constructed by rapid prototyping technique and composed by an array of immunosensors. In DμFED, the electrodes were modified with monoclonal antibody anti-CP-CTV and the detection was carried out using amperometry, based on the hydroquinone/H2O2 catalytic redox reaction due to the presence of HRP label in an immune-sandwich structure. The proposed immunoassay presented excellent linearity with a wide linear range of concentration of 1.95–10.0 × 103 fg mL−1 and ultralow detection limit of 0.3 fg mL−1. The disposable device was successfully applied for the detection of Citrus tristeza virus in healthy and infected plant samples, where it showed good agreements with the comparative method of enzyme-linked immunosorbent assay (ELISA). The developed immunoassay methodology showed a sensitive and selective way in the detection of CTV. Hence, it can be considered as a promising analytical alternative for rapid and low-cost diagnosis of Tristeza disease in citrus.

The fight against drug resistance in chemotherapy requires a molecular-level understanding of the drug interaction with cell membranes, which today is feasible with membrane models. In this study, we report on the interaction of gemcitabine (GEM), a pyrimidine nucleoside antimetabolite used to treat pancreatic cancer, with Langmuir films that mimic healthy and cancerous cell membranes. The cell membrane models were made with eight compositions of a quaternary mixture containing 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphoserine (DPPS), sphingomyelin (SM), and cholesterol (CHOL). The relative concentration of SM was increased so that four of these compositions represented cancerous cells. GEM was found to increase the mean molecular area, also increasing their surface elasticity, with stronger interactions being observed for membranes corresponding to cancerous cells. More specifically, GEM penetrated deepest in the membrane with the highest SM concentration (40 mol%), as inferred from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). This finding was confirmed with molecular dynamics simulations that also indicated how GEM approaches the membrane, which could be useful for guiding the design of drug delivery systems. The experimental and simulation results are consistent with the preferential attachment of GEM onto cancerous cells and highlight the role of SM on drug-cell interactions.

A novel approach for the detection of hydrogen peroxide as a milk adulterant via a colorimetric spot test and smartphone-based photometry is proposed. The procedure is based on analyte oxidation of iron(II) followed by formation of a red iron(III)-thiocyanate complex. The acid medium required for complex formation doubles as a protein precipitation solution, while digital images are taken directly in disposable microtubes under controlled illumination conditions without sample pretreatment. Determination of the adulterant takes about 2 min and generates as little as 350 μL of waste per determination. A linear response was attained from 2.5 to 25.0 mg L−1, with a limit of detection of 1.7 mg L−1 at a 95% confidence level. Repeatability and reproducibility, expressed as coefficients of variation, were 4.8% and 6.8%, respectively. Due to these characteristics, along with the portability and wide availability of smartphones, the proposed method is attractive for determination of hydrogen peroxide adulterant at different stages of production chain.

Early diagnosis of cancer by biomarker detection has been widely studied since it can lead to an increase in patient survival rates. Magnetic nanoparticles (MNPs) play an important role in this field acting as a valuable tool in the biomarker immunocapture and detection. In this work, Co

Outbreaks of foodborne diseases demand simple, rapid techniques for detecting pathogenic bacteria beyond the standard methods that are not applicable to routine analysis in the food industry and in the points of food consumption. In this work, we developed a sensitive, rapid and low-cost assay for detecting Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Salmonella typhimurium (S. typhi) in potable water and apple juice. The assay is based on electrical impedance spectroscopy measurements with screen-printed interdigitated electrodes coupled with magnetite nanoparticles functionalized with the antimicrobial peptide melittin (MLT). The data were analyzed with the information visualization methods Sammon's Mapping and Interactive Document Map to distinguish samples at two levels of contamination from food suitable for consumption. With this approach it has been possible to detect E. coli concentration down to 1 CFU mL−1 in potable water and 3.5 CFU mL−1 in apple juice without sample preparation, within only 25 min. This approach may serve as a low-cost, quick screening procedure to detect bacteria-related food poisoning, especially if the impedance data of several sensing units are combined.

The evaluation of interaction between small molecules and protein is an important step in the discovery of new drugs and to study complex biological systems. In this work, an alternative method was presented to evaluate small-molecule-protein interaction by using ligand capture by protein-coated magnetic particles (MPs) and disposable electrochemical cells. The interaction study was conducted using [10]-gingerol from ginger rhizome and a transmembrane protein αVβ3 integrin. Initially, the electrochemical behavior of the natural compound [10]-gingerol was evaluated with the disposable carbon-based electrodes and presented an irreversible oxidation process controlled by diffusion. The analytical curve for [10]-gingerol was obtained in the range of 1.0 to 20.0 μmol L-1, with limit of detection of 0.26 μmol L-1. Then MPs coated with αVβ3 integrin were incubated with standard solutions and extracts of ginger rhizome for [10]-gingerol capture and separation. The bioconjugate obtained was dropped to the disposable electrochemical cells, keeping a permanent magnet behind the working electrode, and the binding process was evaluated by the electrochemical detection of [10]-gingerol. The assay method proposed was also employed to calculate the [10]-gingerol-αVβ3 integrin association constant, which was calculated as 4.3 × 107 M-1. The method proposed proved to be a good label-free alternative to ligand-protein interaction studies. Graphical abstract ᅟ.

A new disposable microfluidic electrochemical paper-based device (ePAD) consisting of two spot sensors in the same working electrode for the simultaneous determination of uric acid and creatinine was developed. The spot 1 surface was modified with graphene quantum dots for direct uric acid oxidation and spot 2 surface modified with graphene quantum dots, creatininase and a ruthenium electrochemical mediator for creatinine oxidation. The ePAD was employed to construct an electrochemical sensor (based on square wave voltammetry analysis) for the simultaneous determination of uric acid and creatinine in the 0.010-3.0 µmol L-1 range. The device showed excellent analytical performance with a very low simultaneous detection limit of 8.4 nmol L-1 to uric acid and 3.7 nmol L-1 to creatinine and high selectivity. The ePAD was applied to the rapid and successful determination of those clinical biomarkers in human urine samples.

This technical note describes a new microfluidic sensor that combines low-cost (USD $0.97) with rapid fabrication and user-friendly, fast, sensitive, and accurate quantification of a breast cancer biomarker. The electrodes consisted of cost-effective bare stainless-steel capillaries, whose mass production is already well-established. These capillaries were used as received, without any surface modification. Microfluidic chips containing electrical double-layer capillary capacitors (μEDLC) were obtained by a cleanroom-free prototyping that allows the fabrication of dozens to hundreds of chips in 1 h. This sensor provided the successful quantification of CA 15-3, a biomarker protein for breast cancer, in serum samples from cancer patients. Antibody-anchored magnetic beads were utilized for immunocapture of the marker, and then, water was added to dilute the protein. Next, the CA 15-3 detection (2 min) was made without using redox probes, antibody on electrode (sandwich immunoassay), or signal amplification strategies. In addition, the capacitance tests eliminated external pumping systems and precise volumetric sampling steps, as well as presented low sample volume (5 μL) and high sensitivity using bare capillaries in a new design for double-layer capacitors. The achieved limit-of-detection (92.0 μU mL

The hemoglobin (Hb) released from erythrocytes is a primary nutritive component for many blood-feeding parasites. The aspartic protease cathepsin D is a hemoglobinase that is involved in the Hb degradation process and is considered an interesting target for chemotherapy intervention. However, traditional enzymatic assays for studying Hb degradation utilize spectrophotometric techniques, which do not allow real-time monitoring and can present serious interference problems. Herein, we describe a biosensor using simple approach for the real-time monitoring of Hb hydrolysis as well as an efficient screening method for natural products as enzymatic inhibitors using a quartz crystal microbalance (QCM) technique. Hemoglobin was anchored on the quartz crystal surface using mixed self-assembled monolayers. The addition of the enzyme caused a mass change (frequency shift) due to Hb hydrolysis, which was monitored in real time. From the frequency change patterns of the Hb-functionalized QCM, we evaluated the enzymatic reaction by determining the kinetic parameters of product formation ( k cat ). The QCM enzymatic assay using immobilized human Hb was shown to be an excellent approach for screening possible inhibitors in complex mixtures, opening up a new avenue for the discovery of novel inhibitors.

An electrochemical analyzer based on a potentiostat/galvanostat (PG004) was developed and applied to perform in situ Pb2+ and Cd2+ determination in water samples with on-line data transmission, and a global positioning system (GPS), to acquire the geographical coordinate of the place being monitored. For this, a flow-batch analysis (FBA) and a thermostated electrochemical flow cell (EFC) coupled with a boron-doped diamond electrode (BDD) were developed to measure these ions by employing square-wave anodic stripping voltammetry (SWASV). To study the Pb2+ and Cd2+ ions by in situ analysis, mainly for temperature variation, the PG004 was evaluated and the limits of detection were 0.08 μg L−1 and 0.18 μg L−1, respectively, for simultaneous analysis. Then, the PG004 was used for in situ determination of analytes in lake water samples, and voltammograms with good resolution and low noise were obtained. Recoveries ranged from 93.3% to 109%, and the waste generated was as low as 700 μL per determination. The accuracy of the method was checked by determination of Cd2+ and Pb2+ in certified water (NIST), t-unpaired test was applied for n = 3, and the values found were in close agreement at a confidence level of 95%. Besides the geographical coordinates obtained by using a GPS receiver, and experimental data sent via wireless, the device used a solar board as renewable energy. The developed system proved to be a useful tool to measure Pb2+ and Cd2+ in lake samples with a fast, on-line, and environmentally friendly analytical method.

Breast cancer is the most common cancer in women worldwide. The detection of biomarkers has played a significant role in the early diagnosis and prognosis of breast cancer. Herein, we describe the construction of a disposable microfluidic immunoarray device (DμID) for the rapid and low-cost detection of CA15-3 (carbohydrate antigen 15-3), a protein biomarker for breast cancer. The DμID was constructed using a simple and rapid prototyping technique and was applied to detect CA15-3 in cancer patients. The DμID construction was based on the use of a double-sided adhesive card with a microfluidic channel and a screen-printed array with 8 electrodes. Both the immunoarray and microfluidic channel were designed using an inexpensive home cutter printer and using low-cost materials. The immunoarray was modified using the layer-by-layer technique aiming at immobilizing the primary antibody. For the biomarker detection, magnetic particles (MPs) modified with polyclonal antibodies and peroxidase enzymes were used as a strategy for capture, separation, and preconcentration of the biomarker, in addition to amplification of the electroanalytical signal. The preconcentration and amplification strategies integrated with the nanostructured immunosensors of the DμID meaningfully contributed toward the detection of CA15-3 with a limit of detection (LoD) of 6 μU mL

Submitted by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2017-08-10T18:13:59Z No. of bitstreams: 1 teste.txt: 5 bytes, checksum: 698dc19d489c4e4db73e28a713eab07b (MD5) Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2017-08-10T18:14:18Z (GMT) No. of bitstreams: 1 teste.txt: 5 bytes, checksum: 698dc19d489c4e4db73e28a713eab07b (MD5) Made available in DSpace on 2017-08-10T18:14:18Z (GMT). No. of bitstreams: 1 teste.txt: 5 bytes, checksum: 698dc19d489c4e4db73e28a713eab07b (MD5) Previous issue date: 2017-07-20 A novel fully disposable microfluidic electrochemical array device (?FED) was developed and successfully applied for detection of the biomarker estrogen receptor alpha (ER?). The ?FED was constructed using low-cost materials and an inexpensive home cutter printer enabled the manufacture of dozens of ?FEDs in less than 2h, at a cost of less than US$ 0.20 in material per device. The ?FED incorporates counter and reference electrodes and eight carbon-based working electrodes, which were modified with DNA sequences known as estrogen response elements (DNA-ERE), where ER? binds specifically. Paramagnetic particles heavily decorated with anti-ER? antibody and horseradish peroxidase (MP-Ab-HRP) were used to efficiently capture ER? from the sample solution. The ER?-MP-Ab-HRP bioconjugate formed was injected into the ?FED and incubated with the DNA-ERE-modified electrodes, followed by amperometric detection with application of -0.2V vs. Ag|AgCl while a mixture of H2O2 and hydroquinone was injected into the microfluidic device. An ultralow limit of detection of 10.0 fg mL(-1) was obtained with the proposed method. The performance of the assay, in terms of sensitivity and reproducibility, was studied using undiluted calf serum, and excellent recoveries in the range of 94.7-108% were achieved for the detection of ER? in MCF-7 cell lysate. The ?FED system can be easily constructed and applied for multiplex biomarker detection, making the device an excellent cost-effective alternative for cancer diagnosis, especially in developing countries.

In this work, an alternative voltammetric procedure for the determination of Pb(II) was developed using a carbon nanotube paste electrode modified with crosslinked chitosan with glutaraldehyde (GA-CTS-CNTPE). Square-wave adsorptive stripping voltammetry (SWAdSV) was used and the relevant experimental parameters were optimized. Under optimal experimental conditions, the voltammetric response was linear in the range of 9.90 × 10 − 8 to 2.00 × 10 − 6 mol L − 1 with a detection limit of 5.70 × 10 − 8 mol L − 1 . The proposed voltammetric method showed good repeatability and low interference from other metallic species. It was successfully applied in the determination of Pb(II) in natural water samples and the results were in very close agreement with those obtained using a comparative method (inductively coupled plasma optical emission spectrometry (ICP-OES)).

In order to reduce the sample consumption and waste generation for electrochemical purposes, a screen-printed electrode (SPE) used for electrodeposition of bismuth film (SPE-BiFE) and a thermostated electrochemical flow cell (EFC) were developed. The SPE-BiFE with the EFC was employed to determine Cd 2+ and Pb 2+ ions in natural, wastewater and tap water samples by square-wave anodic stripping voltammetry (SWASV). For this, the flow-batch analysis (FBA) approach based on solenoid micro-pumps and three-way valves was developed to carry out a fully automated procedure with temperature control. Furthermore, the FBA and the SWASV parameters were optimized, on line simultaneous determination of Cd 2+ and Pb 2+ ions was performed and two analytical curves were linearly acquired in the concentration ranges from 6.30 to 75.6 µg L −1 and from 3.20 to 38.4 µg L −1 , respectively. Moreover, limits of detection of 0.60 µg L −1 and 0.10 µg L −1 for Cd 2+ and Pb 2+ , respectively, were obtained. Studies of precision for the same SPE-BiFE and repeatability for five built SPE-BiFE were carried out for Cd 2+ and Pb 2+ ion measurements and RSD of 4.1% and 2.9% ( n =3) with repeatabilities ( n =5) of 6.5% and 8.0% were respectively obtained for both analytes. Besides, a low consumption of 700 µL of reagents and a sampling frequency of 13 h −1 were acquired. Simplicity, fast response, accuracy, high portability, robustness and suitability for in loco analyses are the main features of the proposed electroanalytical method.

Multivariate linear regression aided by a successive projections algorithm (SPA-MLR) was applied in the evaluation of anodic stripping voltammetry data obtained in the simultaneous determination of metals under conditions where there were significant complications due to interference processes such as the formation of intermetallic compounds and overlapping peaks. Using simulated data, modeled from complex interactions experimentally observed in samples containing Cu and Zn, as well as Co and Zn, it was demonstrated that SPA-MLR selected variables that allow chemical interpretation. This feature was used to make inferences about the underlying electrochemical processes during the simultaneous determination of four metals (Cu, Pb, Cd, and Co) in a concentration range where all responses were complicated by interference processes (10-100 ng mL −1 ). Additionally, the analytical performances of MLR models for quantitative predictions were excellent despite the complexity of the system under study.

Graphene is a material that has attracted attention with regard to sensing and biosensing applications in recent years. Here, we report a novel treatment (using ultrasonic bath and ultrasonic tip) to obtain graphene oxide (GO) and a new stable conducting film using reduced graphene oxide (RGO) and dihexadecylphosphate film (DHP). The GO was obtained by chemical exfoliation and it was reduced using NaBH4. Subsequently, RGO–DHP dispersion was prepared and it was dropped onto a glassy carbon electrode by casting technique. The electrode was characterized by cyclic voltammetry and electrochemical spectroscopy impedance. The voltammetric behavior of the RGO–DHP/GC electrode in the presence of estradiol was studied, and the results reported an irreversible oxidation peak current at 0.6 V. Under the optimal experimental conditions, using linear sweep adsorptive stripping voltammetry, the detection limit obtained for this hormone was 7.7 × 10−8 mol L−1 . The proposed electrode can be attractive for applications as electrochemical sensors and biosensors.

An automated flow analyzer based on low temperature co-fired ceramic (LTCC), a solid-phase reactor (SPR) and a low-cost photometer was designed for ascorbic acid (AA) determination in pharmaceutical formulations. It consists of a peristaltic pump, three-way solenoid valves, SPR to chemically convert Cu(II) into Cu(I), and a LTCC device for mixing the liberated copper with bathocuproine and detection. The flow cell in the LTCC employed an ultrabright LED — photodiode photometer. The analyzer successfully determined AA in pharmaceutical formulations. The analytical curve from 8.5×10−6 to 7.0×10−4 M gave a detection limit of 7.0×10−7 M and a RSD of 2.1% for a 2.0×10−4 M AA solution (n = 10). A high sampling frequency of 102 h−1 and low reagent and sample consumption (150 µL) resulted.

A versatile and robust thermostatted electrochemical flow cell (EFC) with a boron-doped diamond electrode (BDD) detector was employed to perform two distinct flow-injection electrochemical approaches. In the first approach, differential pulse anodic stripping voltammetry (DPASV) using a flow-batch analysis (FBA) is proposed. In the second approach, multiple pulse amperometry (MPA) employing multicommutation flow analysis (MCFA) is also presented. Both approaches were employed to simultaneously determine Zn2+ and Pb2+ in water samples. For this, a screen-printed electrode (SPE) was developed, and a BDD electrode was coupled to it and was inserted into the EFC. By employing the FBA with the DPASV technique, two analytical curves in concentration ranges from 11.5 to 80.6 μg L−1 and 0.64 to 10.9 μg L−1 for simultaneous determination of Zn2+ and Pb2+, respectively, were obtained. Moreover, limits of detection (LDs) of 0.62 μg L−1 and 0.19 μg L−1 were estimated respectively and a sampling frequency of 12 h−1 was obtained. For MCFA with MPA, analytical curves from 830 to 4980 μg L−1 and 140 to 820 μg L−1 for simultaneous determination of Zn2+ and Pb2+ with LDs of 220.0 μg L−1 and 41.0 μg L−1 and a sampling frequency of 67 h−1 were obtained. The developed EFC allowed a full on-line automation of the methods, covering the pretreatment of BDD, addition of standard solutions, dilutions, thermostatted control, and detection with and without electrochemical preconcentration. In addition, the low waste generation of only 700 μL may be useful for green chemistry purposes and sustainable research.

A simple and sensitive method for simultaneously measuring dopamine (DA), ascorbic acid (AA), and uric acid (UA) using a poly(1-aminoanthracene) and carbon nanotubes nanocomposite electrode is presented. The experimental parameters for composite film synthesis as well as the variables related to simultaneous determination of DA, AA, and UA were optimized at the same time using fractional factorial and Doehlert designs. The use of carbon nanotubes and poly(1-aminoanthracene) in association with a cathodic pretreatment led to three well-defined oxidation peaks at potentials around −0.039, 0.180 and 0.351 V (vs. Ag/AgCl) for AA, DA, and UA, respectively. Using differential pulse voltammetry, calibration curves for AA, DA, and UA were obtained over the range of 0.16–3.12×10−3 mol L−1, 3.54–136×10−6 mol L−1, and 0.76–2.92×10−3 mol L−1, with detection limits of 3.95×10−5 mol L−1, 2.90×10−7 mol L−1, and 4.22×10−5 mol L−1, respectively. The proposed method was successfully applied to determine DA, AA, and UA in biological samples with good results.

A disposable immunosensor for Salmonella enterica subsp. enterica serovar Typhimurium LT2 (S) detection using a magneto-immunoassay and gold nanoparticles (AuNPs) as label for electrochemical detection is developed. The immunosensor is based on the use of a screen-printed carbon electrode (SPCE) that incorporates a permanent magnet underneath. Salmonella containing samples (i.e. skimmed milk) have been tested by using anti-Salmonella magnetic beads (MBs-pSAb) as capture phase and sandwiching afterwards with AuNPs modified antibodies (sSAb-AuNPs) detected using differential pulse voltammetry (DPV). A detection limit of 143 cellsmL -1 and a linear range from 10 3 to 10 6 cellsmL -1 of Salmonella was obtained, with a coefficient of variation of about 2.4%. Recoveries of the sensor by spiking skimmed milk with different quantities of Salmonella of about 83% and 94% for 1.5×10 3 and 1.5×10 5 cellsmL -1 were obtained, respectively. This AuNPs detection technology combined with magnetic field application reports a limit of detection lower than the conventional commercial method carried out for comparison purposes in skimmed milk samples. © 2012 Elsevier B.V., We acknowledge MICINN (Madrid) for the projects PIB2010JP- 00278 and IT2009-0092, and the NATO Science for Peace and Security Programme's support under the project SfP 983807 and to the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brasil for the scholarship given to André Santiago Afonso, grant number 200826/2011-5 and also Torres Quevedo scholarship given to Briza Pérez-López.