Search Results (5)

Sweat analysis by means of minimally invasive wearable sensors is considered a potentially disruptive method for assessing clinical parameters, with exciting applications in early medical diagnostics and high-performance sports. Electrochemical sensors and biosensors are especially attractive because of the possibility of the electronic integration of wearable devices. In this article, we review several aspects regarding the potentialities and present limitations of electrochemical sweat (bio)sensors, including: the main target analytes and their relationships with clinical conditions; most usual electrochemical techniques of transduction used according to the nature of the target analytes; issues connected to the collection of representative sweat samples; aspects regarding the associated, miniaturized electronic instrumentation used for signal processing and communication; and signal processing by machine learning. Full article

The flow at low Mach numbers and high angles of attack over axisymmetric configurations is not symmetric. The mechanism that triggers the asymmetry is a combination of a global (temporal) instability and a convective (spatial) instability. This latter instability is caused by roughness and other geometrical imperfections, which lead to roll angle dependent forces. The flow at these conditions has a complex vortex sheet structure, with two or three different flow regions. An accurate simulation by means of Computational Flow Dynamics (CFD) is thus very challenging, and many researchers have therefore employed Large Eddy Simulation (LES) codes. This study demonstrates that Unsteady Reynolds Averaged Navier-Stokes (URANS) methods are a suitable alternative, if Scale Adaptive Simulation (SAS) is used. This method is capable of capturing the main flow features, provided that fine meshes, which achieve geometrical similarity between the meshed geometry and the real object, and small-time steps are used. It is also demonstrated that, by using URANS methods in combination with SAS, strong differences in the global and local forces depending on the surface roughness of the model are obtained, a result which coincides with several wind tunnel tests. Full article

Enzyme inks can be inkjet printed to fabricate enzymatic biosensors. However, inks containing enzymes present a low shelf life because enzymes in suspension rapidly lose their catalytic activity. Other major problems of printing these inks are the non-specific adsorption of enzymes onto the chamber walls and stability loss during printing as a result of thermal and/or mechanical stress. It is well known that the catalytic activity can be preserved for significantly longer periods of time and to harsher operational conditions when enzymes are immobilized onto adequate surfaces. Therefore, in this work, horseradish peroxidase was covalently immobilized onto silica nanoparticles. Then, the nanoparticles were mixed into an aqueous ink containing single walled carbon nanotubes. Electrodes printed with this specially formulated ink were characterized, and enzyme electrodes were printed. To test the performance of the enzyme electrodes, a complete amperometric hydrogen peroxide biosensor was fabricated by inkjet printing. The electrochemical response of the printed electrodes was evaluated by cyclic voltammetry in solutions containing redox species, such as hexacyanoferrate (III/II) ions or hydroquinone. The response of the enzyme electrodes was studied for the amperometric determination of hydrogen peroxide. Three months after the ink preparation, the printed enzyme electrodes were found to still exhibit similar sensitivity, demonstrating that catalytic activity is preserved in the proposed ink. Thus, enzyme electrodes can be successfully printed employing highly stable formulation using nanoparticles as carriers. Full article

Antibodies are the most used technological tool in histochemistry. However, even with monoclonal antibodies, their standardization is difficult due to variation of biological systems as well as to variability due to the affinity and amplification of the signal arising from secondary peroxidase detection systems. In this article we combined two synthetic molecules to facilitate the standardization of a detection protocol of protein markers in histological sections. The first molecule was an aptamer, a 50-base single-stranded DNA fragment, which recognizes a PTEN tumor suppressor. The second molecule used was also another single stranded 18-base aptamer DNA fragment, which forms a quadruplex structure guanine box. This G-quadruplex recognizes and attaches a molecule of hemin, increasing the catalytic capacity for the hydrogen peroxide. Our results show how the correct structural design of DNA combining an aptamer together with the peroxidase-like DNAzyme allows to detect proteins in histological sections. This tool offers the standardization of the detection of prognostic markers in cancer, in quality and quantity, due to its synthetic nature and its 1:1 antigen:enzyme ratio. This is the first time that reproducible results have been presented in histological sections staining a cancer marker using a single-stranded DNA molecule with dual function. Full article

In this article, we introduce the use of a carboxy-functionalized waterborne carbon nanotube ink for the fabrication of an amperometric biosensor aimed at the quantification of β-lactoglobulin. Detection of this protein from cow’s milk was performed by a sandwich immunoassay onto printed carbon nanotube electrodes. The electrodes were printed using a carbon nanotube ink modified with polystyrene beads containing a high amount of carboxylic groups for protein immobilization. This strategy showed enhanced sensing performance compared to the use of oxidative treatments for the functionalization of electrodes. These electrodes showed an excellent electrochemical behavior, and proteins could be immobilized on their surface via the carbodiimide reaction. These antibody-immobilized carbon nanotube electrodes allowed for the detection of β-lactoglobulin in sub-ppm concentrations. Full article