Commercialized diagnostic technologies to combat SARS-CoV2: Advantages and disadvantages.

The current situation of the Covid-19 pandemic is indicated by a huge number of infections, high lethality, and rapid spread. These circumstances have stopped the activity of almost the entire world, affecting severely the global economy. A rapid diagnosis of the Covid-19 and a generalized testing protocol is essential to fight against the pandemic and to maintain health control in the population. Principal biosensing and diagnostic technologies used to monitor the spread of the SARS-CoV-2 are based on specific genomic analysis and rapid immune tests, both with different technology platforms that include advantages and disadvantages. Most of the in vitro diagnosis companies are competing to be the first on validating under different regulations their technology for placing their platforms for Covid-19 detection as fast as possible in this big international market. A comprehensive analysis of the commercialized technologies for the genomic based sensing and the antibody/antigen detection methods devoted to Covid-19 diagnosis is described in this review, which have been detailed and listed under different countries regulations. The effectiveness of the described technologies throughout the different stages of the disease and a critical comparison of the emerging technologies in the market to counterattack this pandemic have been discussed.

Electrocatalytic tuning of biosensing response through electrostatic or hydrophobic enzyme-graphene oxide interactions.

The effect of graphene oxidative grades upon the conductivity and hydrophobicity and consequently the influence on an enzymatic biosensing response is presented. The electrochemical responses of reduced graphene oxide (rGO) have been compared with the responses obtained from the oxide form (oGO) and their performances have been accordingly discussed with various evidences obtained by optical techniques. We used tyrosinase enzyme as a proof of concept receptor with interest for phenolic compounds detection through its direct adsorption onto a screen-printed carbon electrode previously modified with oGO or rGO with a carbon-oxygen ratio of 1.07 or 1.53 respectively. Different levels of oGO directly affect the (bio)conjugation properties of the biosensor due to changes at enzyme/graphene oxide interface coming from the various electrostatic or hydrophobic interactions with biomolecules. The developed biosensor was capable of reaching a limit of detection of 0.01 nM catechol. This tuning capability of the biosensor response can be of interest for building several other biosensors, including immunosensors and DNA sensors for various applications.

Electrochemical detection of Salmonella using gold nanoparticles.

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 cells mL(-1) and a linear range from 10(3) to 10(6) cells mL(-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) cells mL(-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.

Nanoparticles for the development of improved (bio)sensing systems.

Nanoparticles serve as fundamental building blocks for nanobiotechnology, especially in several applications in the development of novel (bio)sensing systems. Nanoparticles can be used for modification of the surfaces of (bio)sensing transducers or as optical or electroactive labels to improve different aspects of performance, for example sensitivity, detection limit, multidetection capability, and response stability. Nanoparticles can be integrated into the transducer materials on an individual basis or inside other matrices to ensure the immobilization of recognition biomolecules and/or receptors which are the principal components of the (bio)sensing systems. Incorporation of nanoparticles into optical and electrochemical (bio)sensing systems, including their use in microfluidic based systems has the advantages of enabling the design of robust, easy to use, portable, and cost-effective devices.

Structural characterization by confocal laser scanning microscopy and electrochemical study of multi-walled carbon nanotube tyrosinase matrix for phenol detection.

A novel visualization methodology based on the use of immunofluorescence and Confocal Laser Scanning Microscopy (CLSM) was used to quantify and visualize tyrosinase enzyme within a MWCNTs matrix immobilized onto carbon based screen-printed electrodes. CLSM was shown to be an extremely powerful technique which allowed a clear visualization of the distribution of the enzyme within both the MWCNTs and carbon based layers and provided additional and useful morphological data for a better understanding of the interaction between biomolecules and electrode materials. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were also employed to fully characterize the system components. The proposed MWCNT/Tyrosinase matrix was applied to the detection of phenol, as an alternative biosensor material. Electrochemical analytical performances of the biosensor were investigated in order to determine the optimal fabrication design along with the enzyme stability. The biosensor based on the developed biomaterial matrix proved promising results in terms of cost, simplicity and analytical performance. A detection limit of 1.35 microM and a sensitivity of 47.4 microA mM(-1) within a linear response range of 2.5 to 75 microM phenol were obtained. The biosensor performed well as a disposable device and could be stored in a refrigerator (-18 degrees C) without loss of activity for up to 2 months.