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The interest in sustainable and low-cost materials for the production of new sensing platforms has been increasing over the time. The possibility of obtaining reliable sensors, on a large scale, easy-to-produce, and cost-effective allows for the development of analytical devices with adequate characteristics for point-of-care analysis. In this context, we present the development of a new low-cost and easy-to-produce disposable electrochemical device composed of a conductive ink modified with Prussian blue for the detection of uric acid, hydrogen peroxide, and glucose. The electrode surface was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy, Fourier-transform infrared spectroscopy, and cyclic voltammetric techniques. Also, the proposed sensors and biosensors were applied for the electrochemical determination of uric acid, hydrogen peroxide, and glucose. The device achieved a linear response ranging from 5.0 to 150.0 μmol L−1 for uric acid, with a limit of detection of 0.70 μmol L−1 using differential pulse voltammetry. The detection of hydrogen peroxide and glucose was performed using amperometry at a working potential of −0.3 V, which. Hydrogen peroxide sensing presented a linear range varying from 100.0 to 800.0 µmol L−1, with a LOD of 31.6 μmol L−1. A glucose biosensor was developed after modification of the electrode with a film composed of chitosan, glutaraldehyde, and glucose oxidase, which presented a linear range varying from 50.0 to 500.0 μmol L−1, with a LOD of 9.20 μmol L−1. Also, the construction of a 3D printed wearable wristband was proposed facing uric acid determination, to show the versatility of the sensor.

Silver materials are known to present excellent properties, such as high electrical and thermal conductivity as well as chemical stability. Silver-based inks have drawn a lot of attention for being compatible with various substrates, which can be used in the production uniform and stable pseudo-reference electrodes with low curing temperatures. Furthermore, the interest in the use of disposable electrodes has been increasing due to the low cost and the possibility of their use in point-of-care and point-of-need situations. Thus, in this work, two new inks were developed using Ag as conductive material and colorless polymers (nail polish (NP) and shellac (SL)), and applied to different substrates (screen-printed electrodes, acetate sheets, and 3D-printed electrodes) to verify the performance of the proposed inks. Measurements attained with open circuit potential (OCP) attested to the stability of the potential of the pseudo-reference proposed for 1 h. Analytical curves for β-estradiol were also obtained using the devices prepared with the proposed inks as pseudo-references electrodes, which presented satisfactory results concerning the potential stability (RSD < 2.6%). These inks are simple to prepare and present great alternatives for the development of pseudo-reference electrodes useful in the construction of disposable electrochemical systems.

To help meet the global demand for reliable and inexpensive COVID-19 testing and environmental analysis of SARS-CoV-2, the present work reports the development and application of a highly efficient disposable electrochemical immunosensor for the detection of SARS-CoV-2 in clinical and environmental matrices. The sensor developed is composed of a screen-printed electrode (SPE) array which was constructed using conductive carbon ink printed on polyethylene terephthalate (PET) substrate made from disposable soft drink bottles. The recognition site (Spike S1 Antibody (anti-SP Ab)) was covalently immobilized on the working electrode surface, which was effectively modified with carbon black (CB) and gold nanoparticles (AuNPs). The immunosensing material was subjected to a multi-technique characterization analysis using X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) with elemental analysis via energy dispersive spectroscopy (EDS). The electrochemical characterization of the electrode surface and analytical measurements were performed using cyclic voltammetry (CV) and square-wave voltammetry (SWV). The immunosensor was easily applied for the conduct of rapid diagnoses or accurate quantitative environmental analyses by setting the incubation period to 10 min or 120 min. Under optimized conditions, the biosensor presented limits of detection (LODs) of 101 fg mL−1 and 46.2 fg mL−1 for 10 min and 120 min incubation periods, respectively; in addition, the sensor was successfully applied for SARS-CoV-2 detection and quantification in clinical and environmental samples. Considering the costs of all the raw materials required for manufacturing 200 units of the AuNP-CB/PET-SPE immunosensor, the production cost per unit is 0.29 USD.