Contributing to the management of viral infections through simple immunosensing of the arachidonic acid serum level

A trendsetting direct competitive-based biosensing tool has been developed and implemented for the determination of the polyunsaturated fatty acid arachidonic acid (ARA), a highly significant biological regulator with decisive roles in viral infections. The designed methodology involves a competitive reaction between the target endogenous ARA and a biotin-ARA competitor for the recognition sites of anti-ARA antibodies covalently attached to the surface of carboxylic acid-coated magnetic microbeads (HOOC-MµBs), followed by the enzymatic label of the biotin-ARA residues with streptavidin-horseradish peroxidase (Strep-HRP) conjugate. The resulting bioconjugates were magnetically trapped onto the sensing surface of disposable screen-printed carbon transducers (SPCEs) to monitor the extent of the biorecognition reaction through amperometry. The operational functioning of the exhaustively optimized and characterized immunosensing bioplatform was highly convenient for the quantitative determination of ARA in serum samples from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2-) and respiratory syncytial virus (RSV)-infected individuals in a rapid, affordable, trustful, and sensitive manner.

Concept of the "Universal Slope": Toward Substantially Shorter Decentralized Insulin Immunoassays

Decentralized sensing of analytes in remote locations is today a reality. However, the number of measurable analytes remains limited, mainly due to the requirement for time-consuming successive standard additions calibration used to address matrix effects and resulting in greatly delayed results, along with more complex and costly operation. This is particularly challenging in commonly used immunoassays of key biomarkers that typically require from 60 to 90 min for quantitation based on two standard additions, hence hindering their implementation for rapid and routine diagnostic applications, such as decentralized point-of-care (POC) insulin testing. In this work we have developed and demonstrated the theoretical framework for establishing a universal slope for direct calibration-free POC insulin immunoassays in serum samples using an electrochemical biosensor (developed originally for extended calibration by standard additions). The universal slope is presented as an averaged slope constant, relying on 68 standard additions-based insulin determinations in human sera. This new quantitative analysis approach offers reliable sample measurement without successive standard additions, leading to a dramatically simplified and faster assay (30 min vs 90 min when using 2 standard additions) and greatly reduced costs, without compromising the analytical performance while significantly reducing the analyses costs. The substantial improvements associated with the new universal slope concept have been demonstrated successfully for calibration-free measurements of serum insulin in 30 samples from individuals with type 1 diabetes using meticulous statistical analysis, supporting the prospects of applying this immunoassay protocol to routine decentralized POC insulin testing.

3D printed enzymatic microchip for multiplexed electrochemical biosensing

The low-cost e-fabrication of specialized multianalyte biosensors within the point-of-care (POC) settings in a few minutes remains a great challenge. Unlike prefabricated biosensors, 3D printing seems to be able to meet this challenge, empowering the end user with the freedom to create on-demand devices adapted to immediate bioanalytical need. Here, we describe a novel miniature all-3D-printed 4-electrode biochip, capable of the simultaneous determination of different biomarkers in a single assay. The chip is utterly fabricated via an one-step 3D printing process and it is connected to a mini portable bi-potentiostant, permitting simultaneous measurements. The bioanalytical capability of the microchip is demonstrated through the simultaneous amperometric determination of two cardiac biomarkers (cholesterol and choline) in the same blood droplet, via enzymatic assays developed on its two tiny integrated electrodes. The simultaneous determination of cholesterol and choline is free from cross-talk phenomena and interferences offering limits of detection much lower than the cut-off levels of these biomarkers in blood for coronary syndromes. The biodevice is an easy-constructed, low-cost, sensitive and e-transferable POC chip with wide scope of applicability to other enzymatic bioassays.

Simultaneous determination of four fertility-related hormones in saliva using disposable multiplexed immunoplatforms coupled to a custom-designed and field-portable potentiostat

This work reports the first amperometric immunosensor for the simultaneous determination of four fertility-related hormones in saliva: progesterone (P4), luteinizing hormone (LH), estradiol (E2), and prolactin (PRL). The immune platform involves direct competitive (P4 and E2), and sandwich (LH and PRL) assays implemented onto functionalized magnetic microbeads (MBs). The amperometric transduction was performed upon placing the MBs-immunoconjugates onto each of the four working electrodes of the SPCE array (SP4CEs) and applying a detection potential of -0.20 V (vs. Ag pseudo-reference electrode) using the H2O2/hydroquinone (HQ) system. The achieved analytical and operational characteristics of the developed multiplexed immunoplatform showed a sensitivity that allows the determination of these hormones in saliva, and an adequate selectivity to analyse complex clinical samples. The bioplatform was employed for the determination of the set of four hormones in human saliva samples collected from individuals with different hormonal profiles. The results obtained using a conventional potentiostat were compared with those provided employing a novel low-cost custom-designed and field-portable quadruple potentiostat. Similar results were found which also agreed with those obtained by applying ELISA methods for the determination of single hormones.