Detection of Various Traditional Chinese Medicinal Metabolites as Angiotensin-Converting Enzyme Inhibitors: Molecular Docking, Activity Testing, and Surface Plasmon Resonance Approaches

Angiotensin-converting enzyme 1 (ACE1) is a peptide involved in fluid and blood pressure management. It regulates blood pressure by converting angiotensin I to angiotensin II, which has vasoconstrictive effects. Previous studies have shown that certain compounds of natural origin can inhibit the activity of angiotensin-converting enzymes and exert blood pressure-regulating effects. Surface Plasmon Resonance (SPR) biosensor technology is the industry standard method for observing biomolecule interactions. In our study, we used molecular simulation methods to investigate the docking energies of various herbal metabolites with ACE1 proteins, tested the real-time binding affinities between various herbal metabolites and sACE1 by SPR, and analyzed the relationship between real-time binding affinity and docking energy. In addition, to further explore the connection between inhibitor activity and real-time binding affinity, several herbal metabolites' in vitro inhibitory activities were tested using an ACE1 activity test kit. The molecular docking simulation technique's results and the real-time affinity tested by the SPR technique were found to be negatively correlated, and the virtual docking technique still has some drawbacks as a tool for forecasting proteins' affinities to the metabolites of Chinese herbal metabolites. There may be a positive correlation between the enzyme inhibitory activity and the real-time affinity detected by the SPR technique, and the results from the SPR technique may provide convincing evidence to prove the interaction between herbal metabolites and ACE1 target proteins.

Pesticide biosensors: trends and progresses

Pesticides, chemical substances extensively employed in agriculture to optimize crop yields, pose potential risks to human and environmental health. Consequently, regulatory frameworks are in place to restrict pesticide residue concentrations in water intended for human consumption. These regulations are implemented to safeguard consumer safety and mitigate any adverse effects on the environment and public health. Although gas chromatography- and liquid chromatography-mass spectrometry (GC-MS and LC-MS) are highly efficient techniques for pesticide quantification, their use is not suitable for real-time monitoring due to the need for sophisticated laboratory pretreatment of samples prior to analysis. Since they would enable analyte detection with selectivity and sensitivity without sample pretreatment, biosensors appear as a promising alternative. These consist of a bioreceptor allowing for specific recognition of the target and of a detection platform, which translates the biological interaction into a measurable signal. As early detection systems remain urgently needed to promptly alert and act in case of pollution, we review here the biosensors described in the literature for pesticide detection to advance their development for use in the field.

Conducting Polymer-Infused Electrospun Fibre Mat Modified by POEGMA Brushes as Antifouling Biointerface

Biofouling on surfaces, caused by the assimilation of proteins, peptides, lipids and microorganisms, leads to contamination, deterioration and failure of biomedical devices and causes implants rejection. To address these issues, various antifouling strategies have been extensively studied, including polyethylene glycol-based polymer brushes. Conducting polymers-based biointerfaces have emerged as advanced surfaces for interfacing biological tissues and organs with electronics. Antifouling of such biointerfaces is a challenge. In this study, we fabricated electrospun fibre mats from sulphonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (sSEBS), infused with conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) (sSEBS-PEDOT), to produce a conductive (2.06 ± 0.1 S/cm), highly porous, fibre mat that can be used as a biointerface in bioelectronic applications. To afford antifouling, here the poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) brushes were grafted onto the sSEBS-PEDOT conducting fibre mats via surface-initiated atom transfer radical polymerization technique (SI-ATRP). For that, a copolymer of EDOT and an EDOT derivative with SI-ATRP initiating sites, 3,4-ethylenedioxythiophene) methyl 2-bromopropanoate (EDOTBr), was firstly electropolymerized on the sSEBS-PEDOT fibre mat to provide sSEBS-PEDOT/P(EDOT-co-EDOTBr). The POEGMA brushes were grafted from the sSEBS-PEDOT/P(EDOT-co-EDOTBr) and the polymerization kinetics confirmed the successful growth of the brushes. Fibre mats with 10-mers and 30-mers POEGMA brushes were studied for antifouling using a BCA protein assay. The mats with 30-mers grafted brushes exhibited excellent antifouling efficiency, ~82% of proteins repelled, compared to the pristine sSEBS-PEDOT fibre mat. The grafted fibre mats exhibited cell viability >80%, comparable to the standard cell culture plate controls. Such conducting, porous biointerfaces with POEGMA grafted brushes are suitable for applications in various biomedical devices, including biosensors, liquid biopsy, wound healing substrates and drug delivery systems.

Critical reagent screening and characterization: benefits and approaches for protein biomarker assays by hybrid LC–MS

In recent years, hybrid ligand-binding assays (LBAs)/LC–MS assays have been increasingly used for quantitation of protein biomarkers in biological matrices. However, unlike in LBAs where the importance of critical reagent screening and characterization is well understood and widely reported, benefits of well-characterized hybrid LC–MS assay reagents are frequently underestimated. Two groups of analyte-specific reagents, binding reagents and assay calibrators, are considered the critical reagents for biomarker assays. In this article, we summarize the similarities and differences of critical reagents used in LBAs and hybrid LC–MS assays, overview the benefits and approaches of critical reagent screening, characterization, antibody conjugation and discuss bioanalytical considerations in hybrid LC–MS assay development for robust measurements of protein biomarkers in biological matrices.

SPR Biosensor for Quantification of Fetuin-A as a Promising Multibiomarker

Early diagnosis of ongoing malignant disease is crucial to improve survival rate and life quality of the patients and requires sensitive detection of specific biomarkers e.g. prostate-specific antigen (PSA), carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), etc. In spite of current technological advances, malignant diseases are still identified in rather late stages, which have detrimental effect on the prognosis and treatment of the disease. Here, we present a biosensor able to detect fetuin-A, a potential multibiomarker. The biosensing platform is based on polymer brush combining antifouling monomer units of N-(2-hydroxypropyl)methacrylamide (HPMA) and carboxybetaine methacrylamide (CBMAA), statistically copolymerized by surface-initiated atom transfer radical polymerization. The copolymer poly(HPMA-co-CBMAA) exhibits excellent non-fouling properties in the most relevant biological media (i.e. blood plasma) as well as antithrombogenic surface properties by preventing the adhesion of blood components (i.e. leukocytes; platelets; and erythrocytes). Moreover, the polymer brush can be easily functionalized with biorecognition elements maintaining high resistance to blood fouling and the binding capacity can be regulated by tuning the ratio between CBMAA and HPMA units. The superior antifouling properties of the copolymer even after biofunctionalization were exploited to fabricate a new plasmonic biosensor for the analysis of fetuin-A in real clinical blood plasma samples. The assay used in this work can be explored as label-free affinity biosensor for diagnostics of different biomarkers in real clinical plasma samples and to shift the early biomarker detection toward novel biosensor technologies allowing point of care analysis.

Surface plasmon resonance as a tool for ligand-binding assay reagent characterization in bioanalysis of biotherapeutics

Ligand-binding assay (LBA) performance depends on quality reagents. Strategic reagent screening and characterization is critical to LBA development, optimization and validation. Application of advanced technologies expedites the reagent screening and assay development process. By evaluating surface plasmon resonance technology that offers high-throughput kinetic information, this article aims to provide perspectives on applying the surface plasmon resonance technology to strategic LBA critical reagent screening and characterization supported by a number of case studies from multiple biotherapeutic programs.

A non-competitive surface plasmon resonance immunosensor for rapid detection of triazophos residue in environmental and agricultural samples

The wide application of an organophosphate pesticide triazophos raises concern on the environmental pollution and the potential risk to human health. Thus, it is crucial to regularly monitor triazophos residue in the environment and agro-products. Herein we described a non-competitive immunoassay for trace detection of triazophos using a direct surface plasmon resonance (SPR) biosensor. Two anti-triazophos monoclonal antibodies (mAbs) were immobilized on the sensor chip and characterized by SPR-based kinetic analysis. The mAb with relatively slow dissociation rate was used for direct immunosensing of triazophos. The biosensor assay showed a high specificity and a low detection limit of 0.096ngmL^-1 to triazophos, with the linear detection range of 0.98-8.29ngmL^-1. Under the optimal condition, the sensor chip could be regenerated for 160cycles at least. Moreover, the sensitive method was applied to determine triazophos in the spiked environmental water and agricultural products, as well as in unknown real-life samples (including Chinese cabbage, cucumber, and apple). Desirable results demonstrated that the newly-developed immunosensor could be used as a rapid, convenient, and reliable tool to regularly monitor triazophos and meet the detection requirement of its maximum residue limits.

Quantitative investigation of the direct interaction between Hemagglutinin and fusion proteins of Peste des petits ruminant virus using surface Plasmon resonance

Background

The specific and dynamic interaction between the hemagglutinin (H) and fusion (F) proteins of morbilliviruses is a prerequisite for the conformational rearrangements and membrane fusion during infection process. The two heptad repeat regions (HRA and HRB) of F protein are both important for the triggering of F protein.

Methods

In this study, the direct interactions of Peste des petits ruminants virus (PPRV) H with F, HRA and HRB were quantitatively evaluated using biosensor surface plasmon resonance (SPR).

Results

The binding affinities of immobilized pCMV-HA-H (HA-H) interacted with proteins pCMV-HA-F (HA-F) and pCMV-HA-HRB (HA-HRB) (K_D = 1.91 × 10^− 8 M and 2.60 × 10^− 7 M, respectively) reacted an order of magnitude more strongly than that of pCMV-HA-HRA (HA-HRA) and pCMV-HA-Tp IGFR-LD (HA) (K_D = 1.08 × 10^− 4 M and 1.43 × 10^− 4 M, respectively).

Conclusions

The differences of the binding affinities suggested that HRB is involved in functionally important intermolecular interaction in the fusion process.

Characterization of labeled reagents in ligand-binding assays by a surface plasmon resonance biosensor

Aim: Ligand-binding assay (LBA) reagent labeling may change the binding characteristics of the reagent to its target and degrade its performance in LBAs. Results: A surface plasmon resonance (SPR) biosensor was used to evaluate the impact of the biotin labeling process on reagent-binding kinetics and affinity for a specific target. The SPR results demonstrate that the biotin molar challenge ratio affects both association and dissociation rates for the labeled reagent binding to its target. The SPR results also predict the labeled reagent performance in LBAs. Conclusion: The methodology used in this study provides an example of using an SPR biosensor as an efficient way to analytically and functionally characterize critical reagents and to understand their performance postmodification in LBAs.

Hepatitis B plasmonic biosensor for the analysis of clinical serum samples

A plasmonic biosensor for rapid detection of protein biomarkers in complex media is reported. Clinical serum samples were analyzed by using a novel biointerface architecture based on poly[(N-(2-hydroxypropyl) methacrylamide)-co-(carboxybetaine methacrylamide)] brushes functionalized with bioreceptors. This biointerface provided an excellent resistance to fouling even after the functionalization and allowed for the first time the direct detection of antibodies against hepatitis B surface antigen (anti-HBs) in clinical serum samples using surface plasmon resonance (SPR). The fabricated SPR biosensor allowed discrimination of anti-HBs positive and negative clinical samples in 10min. Results are validated by enzyme-linked immunoassays of the sera in a certified laboratory. The sensor could be regenerated by simple treatment with glycine buffer.