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Here, a novel biosensing platform for the detection of SARS‐CoV‐2 usable both at voltammetric and impedimetric mode is reported. The platform was constructed on a multi‐walled carbon nanotubes (MWCNTs) screen‐printed electrode (SPE) functionalized by methylene blue (MB), antibodies against SARS‐CoV‐2 spike protein (SP), a bioactive layer of chitosan (CS) and protein A (PrA). The voltammetric sensor showed superior performances both in phosphate buffer solution (PBS) and spiked‐saliva samples, with LOD values of 5.0±0.1 and 30±2.1 ng/mL, compared to 20±1.8 and 50±2.5 ng/mL for the impedimetric sensor. Moreover, the voltammetric immunosensor was tested in real saliva, showing promising results. [ABSTRACT FROM AUTHOR]

In this work, we report on the development of a simple electrochemical immunosensor for the detection of D-dimer protein in human plasma samples. The immunosensor is built by a simple drop-casting procedure of chitosan nanoparticles (CSNPs) as biocompatible support, Protein A (PrA), to facilitate the proper orientation of the antibody sites to epitopes as a capture biomolecule, and the D-dimer antibody onto a carboxyl functionalized multi-walled carbon nanotubes screen printed electrode (MWCNTs-SPE). The CSNPs have been morphologically characterized by Scanning Electron Microscopy (SEM) and Dynamic Light Scattering (DLS) techniques. Successively, the electrochemical properties of the screen-printed working electrode after each modification step have been characterized by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The resulting MWCNTs-CSNPs-PrA-D-dimer Ab immunosensor displays an optimal and promising platform for antibody immobilization and specific D-dimer detection. DPV has been used to investigate the antigen/antibody interaction at different D-dimer concentrations. The proposed voltammetric immunosensor allowed a linear range from 2 to 500 μg L−1 with a LOD of 0.6 μg L−1 and a sensitivity of 1.3 μA L μg−1 cm−2. Good stability and a fast response time (5 s) have been reported. Lastly, the performance of the voltammetric immunosensor has been tested in human plasma samples, showing satisfactory results, thus attesting to the promising feasibility of the proposed platform for detecting D-dimer in physiological samples. [ABSTRACT FROM AUTHOR]

Bifunctional hydroxyl/thiol-functionalized fourth-generation polyamidoamine dendrimer (G4-PAMAM)-encapsulated Au nanoparticle (NP) was synthesized and immobilized on a mixed self-assembled monolayer (SAM)modified gold surface. This modified surface was resistant to nonspecific adsorption of proteins having a wide range of molecular weight and isoelectric points. Part of the dendrimer thiol groups were converted to hydrazide functionalities providing an activated surface available to subsequently immobilize the receptor for developing a sensor surface to immunoaffinity reaction. Herein, the surface plasmon resonance (SPR) detection of insulin was obtained by means of a competitive immunoassay principle. The resulting Au NP dendrimer-modified surface provided an assay with high stability, significantly enhanced sensitivity, and a detection limit for analyzing insulin of 0.5 pM. The SPR detection of insulin was amplified due to the changes in the dielectric properties of the matrixes, occurring upon the biorecognition processes on the sensor surface, through the coupling of the localized plasmon of the NPs with the surface plasmon wave. The developed sensor chip was used to analyze insulin in human serum samples from healthy and diabetic patients. The results showed good correlation to the reference method. The specificity and the improved sensitivity of this biosensing platform could have significant implications for the detection of a wide range of molecules and biomarkers in complex biological media. 10.1021/ac101319k

Host-guest supramolecular copolymers, formed by an adamantane dimer and two [beta]-cyclodextrin trimers in aqueous solution, are characterized by using small angle X-ray scattering and light scattering experiments. The studies have shown a growth by increasing the concentration involving an increase of both the length and the thickness of the aggregates.