2D graphene oxide–aptamer conjugate materials for cancer diagnosis

Abstract 2D graphene oxide (GO) with large surface area, multivalent structure can easily bind single-stranded DNA/RNA (aptamers) through hydrophobic/π-stacking interactions, whereas aptamers having small size, excellent chemical stability and low immunogenicity bind to their targets with high affinity and specificity. GO–aptamer conjugate materials synthesized by integrating aptamers with GO can thus provide a better alternative to antibody-based strategies for cancer diagnostic and therapy. Moreover, GO’s excellent fluorescence quenching properties can be utilized to develop efficient fluorescence-sensing platforms. In this review, recent advances in GO–aptamer conjugate materials for the detection of major cancer biomarkers have been discussed

Cyclophilin A‐mediated mitigation of coronavirus SARS‐CoV‐2

Abstract Human cyclophilin A (hCypA) is important for the replication of multiple coronaviruses (CoVs), and cyclosporine A inhibitors can suppress CoVs. The emergence of rapidly spreading severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) variants has sparked concerns that mutations affect the binding ability of the spike (S) protein to the angiotensin‐converting enzyme 2 (ACE2) cell receptor, affecting the severity of coronavirus disease (COVID‐19). Far‐western blotting and surface plasmon resonance (SPR) results revealed that hCypA interacts strongly with the viral SARS‐CoV‐2 receptor‐binding domain (RBD), with a binding affinity of 6.85 × 10−8 M. The molecular interaction between hCypA and the viral protein interface was shown using three‐dimensional structural analysis, which revealed the blocking of key residues on the RBD interface by hCypA. The RBD facilitates binding to the ACE2 receptor. The hCypA–S protein complex suppressed the binding of RBD to the ACE2 receptor, which a required event for CoV entry into the host cell. The reliability of this postulated blocking mechanism of the hCypA–SARS‐CoV2 RBD complex with ACE was confirmed by SPR and molecular interaction lateral flow (MILF) strip assay, which offers the immunochromatographic signal read‐outs. The emergence of new SARS‐CoV‐2 variants with key mutations in RBD had a negligible effect on the binding of the RBD variants to hCypA, indicating an effective mitigation strategy for SARS‐CoV‐2 variants. The MILF strip assay results also highlight the neutralizing effect of hCypA by effectively blocking RBD (wild type and its variants) from binding ACE2. Given the importance of hCypA in viral entry regulation, it has the potential to be used as a target for antiviral therapy

Molecular Docking Analysis and Biochemical Evaluation of Levansucrase from <i>Sphingobium chungbukense</i> DJ77

Bacterial exopolymer Levan (β-(2,6) polyfructan) synthesized by levansucrase has attracted interest for various applications due to its low intrinsic viscosity compared with other polysaccharides. We report a novel levansucrase (Lsc) isolated from <i>Sphingobium chunbukense</i> DJ77 and verify its biochemical characteristics by comparative analysis of molecular docking analysis (MOE) and catalytic residue analysis. The complete sequence of the Lsc encoding gene (<i>lsc</i>) was cloned under the direction of the T7 promoter and purified in an <i>Escherichia coli</i> BL21 (DE3) protein expression system. The enzyme activity analysis and ligand docking MOE study of <i>S. chungbukense</i> DJ77 Lsc revealed that Arg 77, Ser112, Arg 195, Asp196, Glu257, and Gln275 were involved in the sucrose binding and splitting as well as transfructosylation activity. A catalytic comparison of Lsc of <i>S. chungbukense</i> DJ77 with the results of site-directed mutational analysis indicated that Gln275 may coordinate a favorable substrate binding environment, offering broad pH resistance in the range of 5–10. The results suggest that the recombinant <i>E. coli</i> carrying <i>S. chungbukense</i> DJ77 Lsc might produce levan under the regular growth conditions with less need for pH manipulation

Aptamer-Based Paper Strip Sensor for Detecting <i>Vibrio fischeri</i>

Aptamer-based paper strip sensor for detecting <i>Vibrio fischeri</i> was developed. Our method was based on the aptamer sandwich assay between whole live cells, <i>V. fischeri</i> and DNA aptamer probes. Following 9 rounds of Cell-SELEX and one of the negative-SELEX, <i>V. fischeri</i> Cell Aptamer (VFCA)-02 and -03 were isolated, with the former showing approximately 10-fold greater avidity (in the subnanomolar range) for the target cells when arrayed on a surface. The colorimetric response of a paper sensor based on VFCA-02 was linear in the range of 4 × 10¹ to 4 × 10⁵ CFU/mL of target cell by using scanning reader. The linear regression correlation coefficient (<i>R</i>²) was 0.9809. This system shows promise for use in aptamer-conjugated gold nanoparticle probes in paper strip format for in-field detection of marine bioindicating bacteria