An electrochemical genomagnetic assay for detection of SARS-CoV-2 and Influenza A viruses in saliva

Viral respiratory infections represent a major threat to the population's health globally. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 disease and in some cases the symptoms can be confused with Influenza disease caused by the Influenza A viruses. A simple, fast, and selective assay capable of identifying the etiological agent and differentiating the diseases is essential to provide the correct clinical management to the patient. Herein, we described the development of a genomagnetic assay for the selective capture of viral RNA from SARS-CoV-2 and Influenza A viruses in saliva samples and employing a simple disposable electrochemical device for gene detection and quantification. The proposed method showed excellent performance detecting RNA of SARS-CoV-2 and Influenza A viruses, with a limit of detection (LoD) and limit of quantification (LoQ) of 5.0 fmol L-1 and 8.6 fmol L-1 for SARS-CoV-2, and 1.0 fmol L-1 and 108.9 fmol L-1 for Influenza, respectively. The genomagnetic assay was employed to evaluate the presence of the viruses in 36 saliva samples and the results presented similar responses to those obtained by the real-time reverse transcription-polymerase chain reaction (RT-PCR), demonstrating the reliability and capability of a method as an alternative for the diagnosis of COVID-19 and Influenza with point-of-care capabilities.

Molecular test for COVID-19 diagnosis based on a colorimetric genomagnetic assay

The world is in a long pandemic period caused by the SARS-CoV-2 virus and massive diagnostic tests to assist efforts to control the spread of the disease and also to avoid new coronavirus variants are still needed. Herein, we propose a simple and accurate saliva-based colorimetric test for the diagnosis of COVID-19. Magnetic beads (MBs) modified with a sequence of single-strand DNA (ssDNA) complementary to the N gene of the SARS-CoV-2 RNA were developed and used for magnetic capture and separation from a complex saliva sample. A second biotinylated ssDNA sequence was applied, and the colorimetric detection was carried out by adding streptavidin-horseradish peroxidase conjugate, H₂O_2, and tetramethylbenzidine (TMB) as chromogenic substrate. The test does not require viral RNA isolation, transcription, or amplification steps and can be performed at room temperature. The molecular assay test can be run using 96-well microplates, allowing the diagnosis of a large number of samples in 90 min. A simple support for magnets was designed and constructed using a 3D printer that allows the magnetic separations directly in the 96-well microplate. The colorimetric test showed an excellent ability to discriminate between healthy individuals and patients infected with SARS-CoV-2, with 92% and 100% of clinical sensitivity and specificity, respectively. This performance was similar to that achieved using the gold standard RT-PCR technique. The proposed genomagnetic assay offers an opportunity to greatly increase population testing, contribute to controlling the spread of the virus, and improve health equity in testing for COVID-19.

A sensitive electrochemical detection of metronidazole in synthetic serum and urine samples using low-cost screen-printed electrodes modified with reduced graphene oxide and C60

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.

Disposable electrochemical microfluidic device for ultrasensitive detection of egg allergen in wine samples

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).

Electrochemical paper-based microfluidic device for high throughput multiplexed analysis

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.

Fast and flexible strategy to produce electrochemical paper-based analytical devices using a craft cutter printer to create wax barrier and screen-printed electrodes

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.

Abstract A53: [10]-gingerol interferes with the adhesion of MDA-MB-231 tumor cells to extracellular matrix

Breast cancer is one of the most common malignant diseases in women worldwide. In developing countries, it is the second highest cause of death in women. Triple-negative breast cancer (TNBC) represents the approximately 15% of breast cancers that lack expression of estrogen (ER) and progesterone receptors (PR) and do not exhibit amplification of the human epidermal growth factor receptor 2 (HER2) gene. Metastatic process is described as a cascade of events. Normal cells are transformed into tumor cells due to mutations in genes that regulate critical pathways, producing an imbalance between proliferation and cell death that eventually leads to the formation of a primary tumor. Further interactions with the stromal microenvironment surrounding tumor cells and extracellular matrix (ECM) proteins contribute to the formation of new vessels. These interactions facilitate tumor cell invasion of surrounding tissues, intravasation through newly formed vessels, and dissemination to other tissues, to form secondary tumors. To treat metastasis from breast and many other cancer types, chemotherapy is one of the most extensively used methods. However, its efficacy and safety remain a primary concern, as well as its toxicity and other side effects. Thus, there is increasing interest in naturally occurring cancer antitumor agents. Ginger (Zingiber officinale Roscoe) is widely used worldwide as a food, spice, and herb. Recently we have demonstrated that [10]-gingerol is able to revert malignant phenotype in breast cancer cells in 3D culture and, moreover, to inhibit the dissemination of TNBC to multiple organs including to lung, bone, and brain, in spontaneous and experimental in vivo metastasis assays. The aim of this work was to investigate the effects of [10]-gingerol on the adhesion properties of MDA-MB-231 cells to the extracellular matrix (ECM). We hypothesized that, at least in part, these effects are mediated through [10]-gingerol interactions with αVβ3 integrin. Human MDA-MB-231 breast tumor cells were obtained from ATCC and maintained at 37°C, 5% CO2 in Dulbecco’s Modified Eagle Medium, containing FBS 10%). Ninety-six well plates were coated vitronectin (1µg/well) dissolved in adhesion buffer at 4ºC overnight, blocked for 2h with 1% BSA, and the wells washed with 100μL of adhesion buffer. MDA-MB-231 cells (5x105/mL) were pretreated for 30min with [10]-gingerol (1-100μM) in a humidified incubator with 5% CO2 at 37°C and 100µL of cell suspension plated into wells and incubated as above for a further 1 hour. Nonadherent cells were gently removed by washing and adherent cells were fixed with 100µl of 4% paraformaldehyde solution for 20min, stopped with PBS-Glycine, stained with DAPI, and counted in a HCS microscope. Data from docking were analyzed in AutoDock plugin for PyMOL and the two-dimensional scheme of interaction was obtained by LiPlot+.The electrochemical study of the interaction between [10]-gingerol and αVβ3 integrin was performed using disposable electrochemical cells (DCell), which are composed by a carbon working electrode, an Ag|AgCl pseudo-reference electrode, and a carbon counter electrode. Measurements were carried out employing the potentiostat DropSens 8000 and Dropview software 8400. The interaction of [10]-gingerol and αVβ3 integrin was evaluated by the changes in the [10]-gingerol electrochemical responses. For this, different amounts of standard αVβ3 integrin solution in PBS pH 7.0 were added and mixed homogeneously with a solution composed of 10µM [10]-gingerol. The differences of peak current were used to demonstrate the changes of electrochemical responses. We found that [10]-gingerol was able to inhibit TNBC cell adhesion to vitronectin ECM with more specificity compared to the other ECM components investigated, demonstrating that this compound interferes in this step of the metastatic process. We proposed that these effects could be, at least in part, resulting from the interaction between [10]-gingerol and αVβ3 integrin, as demonstrated by electrochemical and docking studies.

Citation Format: Angelina Maria Fuzer, Ana Carolina B. M. Martin, Rebeka Tomasin, Carolina Venturini Uliana, Amanda Blanque Becceneri, Rafael L. Bressani Lino, James Almada da Silva, Paulo Cezar Vieira, Heloisa Sobreiro Selistre de Araújo, Rodolpho de Campos Braga, Ronaldo Censi Faria, Marcia Regina Cominetti. [10]-gingerol interferes with the adhesion of MDA-MB-231 tumor cells to extracellular matrix [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr A53.

Conductometric determination of propranolol hydrochloride in pharmaceuticals

In this paper the conductometric titration of propranolol hydrochloride in pharmaceutical formulations using silver nitrate as titrant is proposed. The method was based on the formation of an insoluble salt (AgCl(s)) between the chloride of propranolol hydrochloride molecule and Ag(I) ions of the titrant AgNO3. The effect of the PROP-AgNO3 concentrations and the interval of time between the successive additions of the titrant on the shape of the titration curve were studied. The obtained recoveries for four samples ranged from 96.8 to 105%. The proposed method was successfully applied in the determination of propranolol hydrochloride in several pharmaceutical formulations, with results in close agreement at a 95 % confidence level with those obtained using official spectrophotometric method.