Anti-CCP biosensors in rheumatoid arthritis.

Biosensors are unique analytical tools for the detection of biomarkers. Of these, autoantibodies against citrullinated proteins (ACPA) are useful for the differential diagnosis of rheumatoid arthritis (RA). The autoantibodies may be detected by immunoassay technology using synthetic cyclic citrullinated peptides (CCP), ie, anti-CCP. Recently, several biosensors have been developed for anti-CCP using CCP and mutated citrullinated vimentin (MCV) as recognition elements. In this review we highlight all currently available ACPA biosensor technology including those based on fluorescence, chemiluminescence, electrochemiluminescence (ECL), surface-enhanced Raman scattering (SERS)-based, surface plasmon resonance (SPR), lateral flow immunoassays (LFIA), and electrochemical. We explore various peptides as recognition elements, electrode modifiers and signal amplification systems thus providing new opportunities for next-generation biosensor design in RA.

Electrochemical immunoassay for one-pot detection of thyroxin (T4) and thyroid-stimulating hormone (TSH) using magnetic and Janus nanoparticles.

Concurrent measurement of thyroid-stimulating hormone (TSH) and thyroxine (T4) hormones profoundly help clinicians diagnose hyper- and hypothyroidism. This work demonstrates the development of a sandwich-type electrochemical immunoassay using Janus and magnetic nanoparticles for one-pot detection of thyroxine (T4) and thyroid-stimulating hormone (TSH). The signaling probe was developed by preparing Janus cadmium (CdO) and zinc oxide (ZnO) NPs decorated by T4/TSH-specific molecularly imprinted polymers (MIPT4-CdO and MIPTSH-ZnO). The capture probe was obtained by coating magnetic Fe3O4 NPs with 1,3-Bis(3-carboxy propyl) tetramethyl disiloxane and activating using N-hydroxy succinimide (NHS) and 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC), and finally conjugating with T4/TSH-specific antibodies. To analyze T4 and TSH in actual samples, MIPT4-CdO and MIPTSH-ZnO were added to the sample solutions, and after incubation, capture probes (Fe3O4-AbTSH and Fe3O4-AbT4) were added. An external magnetic field was used to separate the sandwiched nanosystem, followed by adding a dilute solution of nitric acid (HNO3) to dissolve CdO and ZnO NPs and free Cd(II) and Zn(II) cations. The concentration of these cations was determined using constant-current potentiometric stripping analysis (cc-PSA) on screen-printed electrodes (SPE) modified with multi-walled carbon nanotubes (MWCNT). The obtained signals for Cd(II) and Zn(II) were proportional to T4 and TSH concentrations. Limits of detection (LOD) for T4 and TSH analyses were respectively 0.02 ng.dL-1 and 0.0002 µU.mL-1 with a linear range of 0.05-50 ng.dL-1 and 0.001-100 µU.mL-1. The proposed nanosystem's main advantage is the simultaneous detection of T4 and TSH in clinical samples with high sensitivity, selectivity, and stability.

Highly sensitive photoelectrochemical immunosensor for detecting cancer marker CA19-9 based on a new SnSe quantum dot.

A sandwich-type photoelectrochemical (PEC) immunosensor was constructed on a screen-printed electrode (SPE) using gold-coated tin selenide quantum dots (Au-SnSe QDs) to determine the carbohydrate antigen 19 9 (CA19-9). Water-soluble Au-SnSe QDs were prepared by coating low-cost SnSe QDs, prepared by reacting tin(II) 2-ethyl hexanoate with selenium ions (HNaSe) without needing to add an external capping agent (SnSe QDs). SnSe-based QDs were characterized using high-resolution transmission electron microscopy (HR-TEM) and dynamic light scattering (DLS). DSP (dithio-bis (succinimidyl propionate)) as a linker was attached on Au@SnSe QDs and conjugated with CA19-9 monoclonal antibodies (Ab2-DSP-Au@SnSE QD). For capture probe assembling, an Au nano-layer was electrochemically deposited on a SPE by HAuCl4 reduction using 12 cycles of cyclic voltammetry (0 to - 1.4 V) at the scan rate of 50 mV s-1, then covered by self-assembly of DSP and covalent conjugation of CA19-9 Ab1. Our developed PEC immunosensor showed a significant photoelectrochemical response, recorded using chronoamperometry (0.3 V), for the presence of CA19-9 antigen in serum samples under light irradiation, with a detection limit (LOD) of 0.0011 U mL-1 and a dynamic range of 0.005-100 U mL-1. The recovery of CA19-9 determination from serum samples was 101 to 113%.

Electrochemiluminescent immunoassay for the determination of CA15-3 and CA72-4 using graphene oxide nanocomposite modified with CdSe quantum dots and Ru(bpy)3 complex.

A novel immunoassay is introduced based on co-reactant enhancing strategy for the electrochemiluminescent (ECL) determination of CA15-3 and CA72-4 tumor markers in real samples. For the preparation of the signaling probe, CA15-3 and CA72-4 antibodies first were labeled using Ru(bpy)32+-N-hydroxysuccinimide ester (Ru(bpy)32+-NHS) and conjugated with L-cysteine capped cadmium selenide (CdSe) quantum dots. Finally, it was cross-linked with chitosan-grafted graphene oxide (GO@CS) nanocomposite. The capture probe was constructed by deposition of multi-walled carbon nanotubes (MWCNT) at the surface of dual-working gold screen-printed electrodes (MWCNT-dwSPE) and covalent attachment of capture CA15-3 and CA72-4 antibodies to MWCNT-dwSPE. ECL signals were recorded by applying cyclic potential ranging from 0.3 to 1.1 V (vs. pseudo-reference Ag/AgCl) at the scan rate of 100 mV.s-1. This immunoassay was used for determination of CA15-3 and CA72-4 in real samples the detection limits of 9.2 µU.ml-1 and 89 µU.ml-1 within linear ranges of 10 µU.ml-1-500 U.ml-1 and 100 µU.ml-1-150 U.ml-1, respectively. This immunoassay also showed acceptable accuracy with recoveries in the range 96.5-108 % and high reproducibility with RSD of 3.1 and 4.9.

Identification of a potential SARS-CoV2 inhibitor via molecular dynamics simulations and amino acid decomposition analysis.

Considering lack of validated therapeutic drugs or vaccines against contagious SARS-CoV2, various efforts have been focused on repurposing of existing drugs or identifying new agents. In an attempt to identify new and potential SARS-CoV2 inhibitors targeting specific enzyme of the pathogen, a few induced fit models of SARS-CoV2 main protease (Mpro) including N-aryl amide and aryl sulfonamide based fragments were subjected to a multi-step in silico strategy. Sub-structure query of co-crystallographic fragments provided numerous ZINC15 driven commercially available compounds that entered molecular docking stage to find binding interactions/modes inside Mpro active site. Docking results were reevaluated through time dependent stability of top-ranked ligand-protease complexes by molecular dynamics (MD) simulations within 50 ns. Relative contribution of interacted residues in binding to the most probable binding pose was estimated through amino acid decomposition analysis in B3LYP level of theory with Def2-TZVPP split basis set. In confirmation of docking results, MD simulations revealed less perceptible torsional distortions (more stable binding mode) in binding of ZINC_252512772 (ΔGb -9.18 kcal/mol) into Mpro active site. H-bond interactions and hydrophobic contacts were determinant forces in binding interactions of in silico hit. Quantum chemical calculations confirmed MD results and proved the pivotal role of a conserved residue (Glu166) in making permanent hydrogen bond (98% of MD simulations time) with ZINC_252512772. Drug-like physicochemical properties as well as desirable target binding interactions nominated ZINC_252512772 as a desirable in silico hit for further development toward SARS-CoV2 inhibitors. HighlightsA few N-aryl amide/aryl sulfonamide based fragments were subjected to a multi-step in silico strategy to afford potential SARS-CoV2 Mpro inhibitors.MD simulations revealed less perceptible torsional distortions (more stable binding mode) in binding of ZINC_252512772 (ΔGb -9.18 kcal/mol) into Mpro active site.H-bond interactions and hydrophobic contacts were determinant forces in binding interactions of in silico hit.Quantum chemical calculations confirmed MD results and proved pivotal role of a conserved residue (Glu166) in making permanent hydrogen bond (98% of MD simulations time) with ZINC_252512772.Communicated by Ramaswamy H. Sarma.