Selection of single-chain variable fragment antibodies against fenitrothion by ribosome display

Chitosan-platinum nanozyme-mediated ratiometric fluorescent immunosensor with dual catalytic cascades for sensitive detection of fenitrothion

Organophosphorus pesticide residues pose significant threats to food safety and environmental health, and their monitoring methods demand sensitivity and anti-interference capability. In this study, we developed a novel ratiometric fluorescent immunosensor for fenitrothion (FN) detection by employing chitosan-modified platinum nanoparticles (Ch-Pt NPs) as catalytic nanozymes. Ch-Pt NPs exhibit oxidase-mimicking activity, enabling the oxidation of ascorbic acid (AA) and o-phenylenediamine (OPD) to produce dehydroascorbic acid (DHAA) and 2,3-diaminophenazine (DAP, Em = 568 nm), respectively. Then, DHAA further reacted with the remaining OPD to generate quinoxaline derivatives (DFQ, Em = 430 nm). These two products further form ratiometric fluorescent signals. Taking AA as a breakthrough point, the dual-catalytic cascade of natural enzymes and nanozymes was achieved by the combination with the alkaline phosphatase (ALP) -based enzyme-linked immunosorbent assay (ALP-ELISA). Compared with the conventional colorimetric ELISA, the proposed sensor demonstrated a nearly 20-fold enhancement in sensitivity (detection limit: 0.48 ng/mL) and achieved satisfactory recoveries of 80.0-108.3 % in spiked samples. The ratiometric fluorescent immunosensor demonstrates outstanding performance and holds great potential for extensive applications in the field of pesticide monitoring.

Production of a Ribosome-Displayed Mouse scFv Antibody Against CD133, Analysis of Its Molecular Docking, and Molecular Dynamic Simulations of Their Interactions

The pentaspan transmembrane glycoprotein CD133, prominin-1, is expressed in cancer stem cells in many tumors and is promising as a novel target for the delivery of cytotoxic drugs to cancer-initiating cells. In this study, we prepared a mouse library of single-chain variable fragment (scFv) antibodies using mRNAs isolated from mice immunized with the third extracellular domain of a recombinant CD133 (D-EC3). First, the scFvs were directly exposed to D-EC3 to select a new specific scFv with high affinity against CD133 using the ribosome display method. Then, the selected scFv was characterized by the indirect enzyme-linked immunosorbent assay (ELISA), immunocytochemistry (ICC), and in silico analyses included molecular docking and molecular dynamics simulations. Based on ELISA results, scFv 2 had a higher affinity for recombinant CD133, and it was considered for further analysis. Next, the immunocytochemistry and flow cytometry experiments confirmed that the obtained scFv could bind to the CD133 expressing HT-29 cells. Furthermore, the results of in silico analysis verified the ability of the scFv 2 antibody to bind and detect the D-EC3 antigen through key residues employed in antigen-antibody interactions. Our results suggest that ribosome display could be applied as a rapid and valid method for isolation of scFv with high affinity and specificity. Also, studying the mechanism of interaction between CD133's scFv and D-EC3 with two approaches of experimental and in silico analysis has potential importance for the design and development of antibody with improved properties.

Development of a bioluminescence resonance energy transfer Quenchbody sensor for the detection of organophosphorus pesticides in water bodies

Rapid and precise quantification of organophosphorus pesticides (OPPs) in environmental water bodies is crucial for evaluating ecological risks and safeguarding human health. Traditional instrumental methods are complex, time-consuming, and expensive, while enzyme-based biosensors suffer from instability and require a constant supply of substrates. Hence, there is an urgent need for a fast, simple, and sensitive biosensor for OPPs. In this study, we developed a novel non-enzymatic biosensor for the detection of methyl parathion (MP) by employing the bioluminescence resonance energy transfer (BRET) Q-body strategy. Optimizing the spacer arm and screening fluorescent dyes identified the R6G BRET MP Q-body sensor with the best performance. Key parameters affecting the sensor's detection performance were optimized by using single-factor experiments. Under optimal conditions, the detection exhibited a detection limit of 5.09 ng·mL-1 and a linear range of 16.21-848.81 ng·mL-1. The sensor's accuracy was validated using standard recovery experiments, yielding a recovery rate of 84.47 %-102.08 % with a standard deviation of 1.93 %-9.25 %. The detection results of actual water samples demonstrate that this fast, simple, and highly sensitive BRET Q-body sensor holds great promise for practical water quality monitoring.

Eukaryotic ribosome display for antibody discovery: A review

Monoclonal antibody biologics have significantly transformed the therapeutic landscape within the biopharmaceutical industry, partly due to the utilisation of discovery technologies such as the hybridoma method and phage display. While these established platforms have streamlined the development process to date, their reliance on cell transformation for antibody identification faces limitations related to library diversification and the constraints of host cell physiology. Cell-free systems like ribosome display offer a complementary approach, enabling antibody selection in a completely in vitro setting while harnessing enriched cellular molecular machinery. This review aims to provide an overview of the fundamental principles underlying the ribosome display method and its potential for advancing antibody discovery and development.

EGFR-targeted humanized single chain antibody fragment functionalized silica nanoparticles for precision therapy of cancer

The combination of highly specific targeting ability and potent killing effect has made antibody-drug conjugates (ADCs) a popular area of focus in the development of anti-cancer drugs. However, the large molecular weight of IgG antibodies (∼ 150 kDa) often faces challenges in penetrating capillaries and stroma in tumor tissue. Moreover, when the drug-antibody ratio (DAR) is too low (DAR < 2) or too high (DAR > 6) it decreases the effectiveness of the ADC and further increases the potential for aggregation, overall clearance of the early system payload, and release rate. In this study, an EGFR-based single-chain antibody fragment (husA)-human serum albumin (HSA)-coupled FITC-labeled mesoporous silica nanoparticle (FMSN-DOX-H-husA) was developed. Chinese hamster ovarian cells express the husA, which is a single chain antibody fragment of the EGFR that has been humanized. The small molecular weight of the single chain antibody allows for shorter penetration into solid tumors and the absence of adverse effects of the Fc fragment. The modification of HSA improves the safety of the antibody nanoparticle couples by both improving the biocompatibility of the nanoparticles, prolonging the circulation time of the nanoparticles, and avoiding early release of the payload. Also, the humanization substantially reduces the immunogenicity. More importantly, the ratio of drug antibodies on nanoparticles was experimentally and computationally derived to be 11.8, providing a more accurate guide for clinical trials. The results of both in vivo and in vitro experiments indicated promising antitumor activity and safety of FMSN-DOX-H-husA. Thus, this antibody-drug conjugate provided a hopeful option for cancer treatment.

Single-chain fragment variable produced by phage display technology: Construction, selection, mutation, expression, and recent applications in food safety

Immunoassays are reliable, efficient, and accurate methods for the analysis of small-molecule harmful substances (such as pesticides, veterinary drugs, and biological toxins) that may be present in food. However, traditional polyclonal and monoclonal antibodies are limited by animal hosts and hinder further development of immunoassays. With the gradual application of phage display technology as an efficient in vitro selection technology, the single-chain fragment variable (scFv) now provides an exciting alternative to traditional antibodies. Efficiently constructed scFv source libraries and specifically designed biopanning schemes can now yield scFvs possessing specific recognition capabilities. A rational mutation strategy further enhances the affinity of scFv, and allows it to reach a level that cannot be achieved by immunization. Finally, appropriate prokaryotic expression measures ensure stable and efficient production of scFv. Therefore, when developing excellent scFvs, it is necessary to focus on three key aspects of this process that include screening, mutation, and expression. In this review, we analyze in detail the preparation and affinity improvement process for scFv and provide insights into the research progress and development trend of scFv-based immunoassay methods for monitoring small-molecule harmful substances.

Recognition elements based on the molecular biological techniques for detecting pesticides in food: A review

Excessive use of pesticides can cause contamination of the environment and agricultural products that are directly threatening human life and health. Therefore, in the process of food safety supervision, it is crucial to conduct sensitive and rapid detection of pesticide residues. The recognition element is the vital component of sensors and methods for fast testing pesticide residues in food. Improper recognition elements may lead to defects of testing methods, such as poor stability, low sensitivity, high economic costs, and waste of time. We can use the molecular biological technique to address these challenges as a good strategy for recognition element production and modification. Herein, we review the molecular biological methods of five specific recognition elements, including aptamers, genetic engineering antibodies, DNAzymes, genetically engineered enzymes, and whole-cell-based biosensors. In addition, the application of these identification elements combined with biosensor and immunoassay methods in actual detection was also discussed. The purpose of this review was to provide a valuable reference for further development of rapid detection methods for pesticide residues.

Isolation and characterization of a novel GRP78-specific single-chain variable fragment (scFv) using ribosome display method

Glucose-regulated protein 78 (GRP78) is a well-characterized endoplasmic reticulum (ER) chaperon frequently overexpressed at the surface of tumor cells and associated with tumor survival, metastasis, and chemoresistance. Hence, potential GRP78 binders emerge as promising candidates for cancer therapy and diagnosis. We applied ribosome display to isolate a single-chain variable domain (scFv) specific for the C-terminal domain of a recombinant human GRP78 (CGRP). Six female BALB/c mice were immunized and then splenocyte mRNA was extracted. An scFv-ribosome display library was established by joining the amplified V_H/Vκ fragments through a 72-bp linker using overlap extension PCR. Then, selection was performed by applying two rounds of eukaryotic ribosome display panning with stepwise decreased amount of CGRP. Ultimately, the selected scFv was characterized using the indirect-ELISA assay, competitive-ELISA assay, Western blotting, Surface Plasmon Resonance (SPR), and in-silico analyses. The constructed library had a length of ~ 1100 bp and the high-affinity scFvs were isolated using the outputs of the final panning round. Among 60 positive clones, GSF3 was selected and its expression, purification, and binding capacity was confirmed by SDS-PAGE and Western blotting. GSF3 exhibited an affinity of 13 × 10⁷ M^-1 to CGRP as assessed by SPR. Moreover, the in-silico analyses indicated that GSF3 binds the C-terminal domain of GRP78 through key residues engaged in antibody-antigen interactions. We found that ribosome display is a swift and reliable technique for specific and high-affinity scFv isolation. Moreover, our results suggest that GSF3 might be applied as a potential cancer immunotherapeutic and diagnostic tool if this approach is carefully followed by successful preclinical and clinical evaluations to validate the findings for further confirmation.

Immunoassay-based approaches for development of screening of chlorpyrifos

Chlorpyrifos (CPF) is an extensively used organophosphate pesticide for crop protection. However, there are concerns of it contaminating the environment and human health with estimated three lakh deaths annually. Detection of CPF in blood samples holds significance to avoid severe health outcomes due to continuous exposure. The most common techniques for CPF detection are Gas chromatography (GC) and high-performance liquid chromatography (HPLC). However, these techniques might not be feasible at the community healthcare level due to high-cost instrumentation, time-consuming sample preparation protocol and skilled analysts. Therefore, rapid, effective and economical methods such as immunoassay would be imperative for CPF detection in biological samples. The vital step in immunoassay development is the design of a potent immunogen from non-immunogenic molecules. The molecular modelling protocol could assist in redesigning known CPF linkers and inserting them at different substitutable positions of CPF to get distinctive CPF derivatives. Molecular docking and binding free energy analysis can be used to identify the CPF derivatives having a better binding affinity with carrier protein compared to CPF. The top-ranked CPF derivatives based on docking score and binding energy could be ideal for synthesis and immunogen development. The present review will comprehend technological trends in immunoassay kits for detecting chlorpyrifos from biological samples.

Identification and characterization of a novel single-chain variable fragment (scFv) antibody against Neisseria meningitidis factor H-binding protein (fHbp)

Purpose. Neisseria meningitidis is the leading global cause of meningitis and sepsis. Detection, followed by identification, of bacterial pathogens is important in medicine and public health. In the present study, we used the ribosome display technique to select single-chain variable fragments (scFv) that are specific to the surface-exposed fHbp antigen of N. meningitidis. Methodology. The recombinant fHbp protein was used as the antigen for the immunization of BALB/c mice. Anti-fHbp VH/k chain ribosome display libraries were assembled by joining VH and k into the VH/k chain with a specially constructed linker by PCR overlap extension. The scFv library was panned against the recombinant fHbp protein by using a single round of the ribosome display method via a rabbit reticulocyte lysate system.Results/Key findings. The selected anti-fHbp antibody exhibited high affinity and specificity in the enzyme-linked immunosorbent assay (ELISA) and the whole bacterial cell enzyme-linked immunosorbent assay (Bact-ELISA).Conclusion. The affinity of the selected scFv was ~8.65×10⁹ M^-1. The isolated scFv can provide the basis for developing a diagnostic kit.

Expression and Functional Properties of an Anti-Triazophos High-Affinity Single-Chain Variable Fragment Antibody with Specific Lambda Light Chain

Triazophos is a widely used organophosphorous insecticide that has potentially adverse effects to organisms. In the present study, a high-affinity single-chain variable fragment (scFv) antibody with specific lambda light chain was developed for residue monitoring. First, the specific variable regions were correctly amplified from a hybridoma cell line 8C10 that secreted monoclonal antibody (mAb) against triazophos. The regions were then assembled as scFv via splicing by overlap extension polymerase chain reaction. Subsequently, the recombinant anti-triazophos scFv-8C10 was successfully expressed in Escherichia coli strain HB2151 in soluble form, purified through immobilized metal ion affinity chromatography, and verified via Western blot and peptide mass fingerprinting analyses. Afterward, an indirect competitive enzyme-linked immunosorbent assay was established based on the purified anti-triazophos scFv-8C10 antibody. The assay exhibited properties similar to those based on the parent mAb, with a high sensitivity (IC50 of 1.73 ng/mL) to triazophos and no cross reaction for other organophosphorus pesticides; it was reliable in detecting triazophos residues in spiked water samples. Moreover, kinetic measurement using a surface plasmon resonance biosensor indicated that the purified scFv-8C10 antibody had a high affinity of 1.8 × 10(-10) M and exhibited good binding stability. Results indicated that the recombinant high-affinity scFv-8C10 antibody was an effective detection material that would be promising for monitoring triazophos residues in environment samples.