Nanobody-Based Immunosensor Detection Enhanced by Photocatalytic-Electrochemical Redox Cycling

Singlet oxygen-based photoelectrochemical detection of miRNAs in prostate cancer patients' plasma: A novel diagnostic tool for liquid biopsy

Dysregulation of miRNA expression occurs in many cancers, making miRNAs useful in cancer diagnosis and therapeutic guidance. In a clinical context using methods such as polymerase chain reaction (PCR), the limited amount of miRNAs in circulation often limits their quantification. Here, we present a PCR-free and sensitive singlet oxygen (1O2)-based strategy for the detection and quantification of miRNAs in untreated human plasma from patients diagnosed with prostate cancer. A target miRNA is specifically captured by functionalised magnetic beads and a detection oligonucleotide probe in a sandwich-like format. The formed complex is concentrated at the sensor surface via magnetic beads, providing an interface for the photoinduced redox signal amplification. The detection oligonucleotide probe bears a molecular photosensitiser, which produces 1O2 upon illumination, oxidising a redox reporter and creating a redox cycling loop, allowing quantification of pM level miRNA in diluted human plasma within minutes after hybridisation and without target amplification.

Electrochemical Affinity Biosensors: Pervasive Devices with Exciting Alliances and Horizons Ahead

Electrochemical affinity biosensors are evolving at breakneck speed, strengthening and colonizing more and more niches and drawing unimaginable roadmaps that increasingly make them protagonists of our daily lives. They achieve this by combining their intrinsic attributes with those acquired by leveraging the significant advances that occurred in (nano)materials technology, bio(nano)materials and nature-inspired receptors, gene editing and amplification technologies, and signal detection and processing techniques. The aim of this Perspective is to provide, with the support of recent representative and illustrative literature, an updated and critical view of the repertoire of opportunities, innovations, and applications offered by electrochemical affinity biosensors fueled by the key alliances indicated. In addition, the imminent challenges that these biodevices must face and the new directions in which they are envisioned as key players are discussed.

Gold nanoclusters-manganese dioxide composite-based fluorescence immunoassay for sensitive monitoring of fenitrothion degradation in Chinese cabbage

Understanding the residues and degradation of organophosphorus pesticides (OPs) in crops has attracted increasing attention. Herein, we designed a sensitive fluorescence immunoassay (FIA) by employing nanobody-linked alkaline phosphatase (Nb-ALP) and gold nanoclusters anchored manganese dioxide (AuNCs-MnO₂) composite. In immunoassay protocol, Nb-ALP is used to competitively recognize the coating antigen and pesticide. After competitive immunoreaction, alkaline phosphatase catalyzes l-ascorbic acid-2-phosphate to produce ascorbic acid that can trigger the decomposition of the AuNCs-MnO₂ composite, regulating the fluorescence response. As a proof-of-concept, fenitrothion (FNT) is chosen as the target analyte. As a result, the developed FIA exhibits high detection sensitivity (IC₁₀ = 5.78 pg/mL), which is about 56-times higher than that of the conventional enzyme-linked immunosorbent assay. The developed FIA has been successfully applied for precisely monitoring the degradation of FNT in Chinese cabbage with excellent anti-interference ability and reproducibility, paving the way for the determination of pesticide residues in real food samples.

Recent Advances in the Development and Characterization of Electrochemical and Electrical Biosensors for Small Molecule Neurotransmitters

Neurotransmitters act as chemical messengers, determining human physiological and psychological function, and abnormal levels of neurotransmitters are related to conditions such as Parkinson's and Alzheimer's disease. Biologically and clinically relevant concentrations of neurotransmitters are usually very low (nM), so electrochemical and electronic sensors for neurotransmitter detection play an important role in achieving sensitive and selective detection. Additionally, these sensors have the distinct advantage to potentially be wireless, miniaturized, and multichannel, providing remarkable opportunities for implantable, long-term sensing capabilities unachievable by spectroscopic or chromatographic detection methods. In this article, we will focus on advances in the development and characterization of electrochemical and electronic sensors for neurotransmitters during the last five years, identifying how the field is progressing as well as critical knowledge gaps for sensor researchers.

Characterization of a Ruthenium(II) Complex in Singlet Oxygen-Mediated Photoelectrochemical Sensing

A water-soluble ruthenium(II) complex (L), capable of producing singlet oxygen (¹O₂) when irradiated with visible light, was used to modify the surface of an indium-tin oxide (ITO) electrode decorated with a nanostructured layer of TiO₂ (TiO₂/ITO). Singlet oxygen triggers the appearance of a cathodic photocurrent when the electrode is illuminated and biased at a proper reduction potential value. The L/TiO₂/ITO electrode was first characterized with cyclic voltammetry, impedance spectroscopy, NMR, and Raman spectroscopy. The rate constant of singlet oxygen production was evaluated by spectrophotometric measurements. Taking advantage of the oxidative process initiated by ¹O₂, the analysis of phenolic compounds was accomplished. Particularly, the ¹O₂-driven oxidation of hydroquinone (HQ) produced quinone moieties, which could be reduced back at the electrode surface, biased at -0.3 V vs Ag/AgCl. Such a light-actuated redox cycle produced a photocurrent dependent on the concentration of HQ in solution, exhibiting a limit of detection (LOD) of 0.3 μmol dm^-3. The L/TiO₂/ITO platform was also evaluated for the analysis of p-aminophenol, a commonly used reagent in affinity sensing based on alkaline phosphatase.

SARS-CoV-2 neutralizing camelid heavy-chain-only antibodies as powerful tools for diagnostic and therapeutic applications

Introduction

The ongoing COVID-19 pandemic situation caused by SARS-CoV-2 and variants of concern such as B.1.617.2 (Delta) and recently, B.1.1.529 (Omicron) is posing multiple challenges to humanity. The rapid evolution of the virus requires adaptation of diagnostic and therapeutic applications.

Objectives

In this study, we describe camelid heavy-chain-only antibodies (hcAb) as useful tools for novel in vitro diagnostic assays and for therapeutic applications due to their neutralizing capacity.

Methods

Five antibody candidates were selected out of a naïve camelid library by phage display and expressed as full length IgG2 antibodies. The antibodies were characterized by Western blot, enzyme-linked immunosorbent assays, surface plasmon resonance with regard to their specificity to the recombinant SARS-CoV-2 Spike protein and to SARS-CoV-2 virus-like particles. Neutralization assays were performed with authentic SARS-CoV-2 and pseudotyped viruses (wildtype and Omicron).

Results

All antibodies efficiently detect recombinant SARS-CoV-2 Spike protein and SARS-CoV-2 virus-like particles in different ELISA setups. The best combination was shown with hcAb B10 as catcher antibody and HRP-conjugated hcAb A7.2 as the detection antibody. Further, four out of five antibodies potently neutralized authentic wildtype SARS-CoV-2 and particles pseudotyped with the SARS-CoV-2 Spike proteins of the wildtype and Omicron variant, sublineage BA.1 at concentrations between 0.1 and 0.35 ng/mL (ND50).

Conclusion

Collectively, we report novel camelid hcAbs suitable for diagnostics and potential therapy.

A Novel Nanobody-Horseradish Peroxidase Fusion Based-Competitive ELISA to Rapidly Detect Avian Corona-Virus-Infectious Bronchitis Virus Antibody in Chicken Serum

Avian coronavirus-infectious bronchitis virus (AvCoV-IBV) is the causative agent of infectious bronchitis (IB) that has brought great threat and economic losses to the global poultry industry. Rapid and accurate diagnostic methods are very necessary for effective disease monitoring. At the present study, we screened a novel nanobody against IBV-N protein for development of a rapid, simple, sensitive, and specific competitive ELISA for IBV antibody detection in order to enable the assessment of inoculation effect and early warning of disease infection. Using the phage display technology and bio-panning, we obtained 7 specific nanobodies fused with horseradish peroxidase (HRP) which were expressed in culture supernatant of HEK293T cells. Out of which, the nanobody of IBV-N-Nb66-vHRP has highly binding with IBV-N protein and was easily blocked by the IBV positive serums, which was finally employed as an immunoprobe for development of the competitive ELISA (cELISA). In the newly developed cELISA, we reduce the use of enzyme-conjugated secondary antibody, and the time of whole operation process is approximately 1 h. Moreover, the IBV positive serums diluted at 1:1000 can still be detected by the developed cELISA, and it has no cross reactivity with others chicken disease serums including Newcastle disease virus, Fowl adenovirus, Avian Influenza Virus, Infectious bursal disease virus and Hepatitis E virus. The cut-off value of the established cELISA was 36%, and the coefficient of variation of intra- and inter-assay were 0.55–1.65% and 2.58–6.03%, respectively. Compared with the commercial ELISA (IDEXX kit), the agreement rate of two methods was defined as 98% and the kappa value was 0.96, indicating the developed cELISA has high consistency with the commercial ELISA. Taken together, the novel cELISA for IBV antibody detection is a simple, rapid, sensitive, and specific immunoassay, which has the potential to rapidly test IBV antibody contributing to the surveillance and control of the disease.