Serological determination of Helicobacter pylori infection using sandwiched and enzymatically amplified piezoelectric biosensor

Biosensors for point-of-care testing and personalized monitoring of gastrointestinal microbiota

The gastrointestinal (GI) microbiota is essential in maintaining human health. Alteration of the GI microbiota or gut microbiota (GM) from homeostasis (i.e., dysbiosis) is associated with several communicable and non-communicable diseases. Thus, it is crucial to constantly monitor the GM composition and host-microbe interactions in the GI tract since they could provide vital health information and indicate possible predispositions to various diseases. Pathogens in the GI tract must be detected early to prevent dysbiosis and related diseases. Similarly, the consumed beneficial microbial strains (i.e., probiotics) also require real-time monitoring to quantify the actual number of their colony-forming units within the GI tract. Unfortunately, due to the inherent limitations associated with the conventional methods, routine monitoring of one's GM health is not attainable till date. In this context, miniaturized diagnostic devices such as biosensors could provide alternative and rapid detection methods by offering robust, affordable, portable, convenient, and reliable technology. Though biosensors for GM are still at a relatively preliminary stage, they can potentially transform clinical diagnosis in the near future. In this mini-review, we have discussed the significance and recent advancements of biosensors in monitoring GM. Finally, the progresses on future biosensing techniques such as lab-on-chip, smart materials, ingestible capsules, wearable devices, and fusion of machine learning/artificial intelligence (ML/AI) have also been highlighted.

Evolution of Diagnostic Methods for Helicobacter pylori Infections: From Traditional Tests to High Technology, Advanced Sensitivity and Discrimination Tools

Rapid diagnosis and treatment application in the early stages of H. pylori infection plays an important part in inhibiting the transmission of this infection as this bacterium is involved in various gastric pathologies such as gastritis, gastro-duodenal ulcer, and even gastric neoplasia. This review is devoted to a quick overview of conventional and advanced detection techniques successfully applied to the detection of H. pylori in the context of a compelling need to upgrade the standards of the diagnostic methods which are currently being used. Selecting the best diagnostic method implies evaluating different features, the use of one or another test depending on accessibility, laboratories equipment, and the clinical conditions of patients. This paper aims to expose the diagnosis methods for H. pylori that are currently available, highlighting their assets and limitations. The perspectives and the advantages of nanotechnology along with the concept of nano(bio)sensors and the development of lab-on-chip devices as advanced tools for H. pylori detection, differentiation, and discrimination is also presented, by emphasizing multiple advantages: simple, fast, cost-effective, portable, miniaturized, small volume of samples required, highly sensitive, and selective. It is generally accepted that the development of intelligent sensors will completely revolutionize the acquisition procedure and medical decision in the framework of smart healthcare monitoring systems.

Advances in diagnosis of Helicobacter pylori through biosensors: Point of care devices

Invasive as well as non-invasive conventional techniques for the detection of Helicobacter pylori (H. pylori) have several limitations that are being overcome by the development of novel, rapid and reliable biosensors. Herein, we describe several biosensors fabricated for the detection of H. pylori. This review aims to provide the principles of biosensors and their components including in the context to H. pylori detection. The major biorecognition elements in H. pylori detection include antigen/antibodies, oligonucleotides and enzymes. Furthermore, the review describes the transducers, such as electrochemical, optical and piezoelectric, also including microfluidics approaches. An overview of the biomarkers associated with H. pylori pathogenesis is also discussed. Finally, the prospects of advancement and commercialization of point-of-care tools are summarized.

Triple-nanostructuring-based noninvasive electro-immune sensing of CagA toxin for Helicobacter pylori detection

BACKGROUND

Helicobacter pylori (H pylori) is gram-negative, spiral, and microaerophilic bacteria which can survive in ~2%-10% oxygen level. It was reported to populate in human gastric mucosa and leads to gastric cancer without any age or gender difference.

MATERIALS AND METHODS

In this study, we are targeting label-free electrochemical immunosensor development for rapid H pylori detection after covalently immobilizing the antibody (CagA) over the nanomaterials modified Au electrode. Titanium oxide nanoparticles (TiO₂ NPs), carboxylated multi-walled carbon nanotubes (c-MWCNT), and conducting polymer polyindole carboxylic acid (Pin5COOH) composites (TiO₂ NPs/c-MWCNT/Pin5COOH) were synthesized and further utilized in immunosensor development as an electrochemical interface onto Au electrode. The stepwise modifications of CagAantibody/TiO₂ NPs/c-MWNCT/Pin5COOH/Au electrode were electrochemically studied.

RESULTS

Possessing the unique features of advanced materials, the proposed immunosensor reported low sensing limit of 0.1 ng/mL in dynamic linear range of 0.1-8.0 ng/mL with higher stability and reproducibility. Furthermore, developed sensor-based determination of H pylori in five human stool specimens has shown good results with suitable accuracy.

CONCLUSIONS

This work lays strong foundation toward developing nanotechnology-enabled electrochemical sensor for ultrasensitive and early detection of H pylori in noninvasively collected clinical samples.

A novel fluorescent DNA sensor for ultrasensitive detection of Helicobacter pylori

In this work, a novel fluorescent DNA sensor for ultrasensitive detection of Helicobacter pylori (H. pylori) DNA was developed. This strategy took advantage of DNA hybridization between single-stranded DNA (ssDNA, which had been designed as an aptamer specific for H. pylori DNA) and the complementary target H. pylori DNA, and the feature that ssDNA bound to graphene oxide (GO) with significantly higher affinity than double-stranded DNA (dsDNA). ssDNA were firstly covalent conjugated with CuInS₂ quantum dots (QDs) by reaction between the carboxy group of QDs and amino group modified ssDNA, forming ssDNA-QDs genosensor. In the absence of the complementary target H. pylori DNA, GO could adsorb ssDNA-QDs DNA sensor and efficiently quench the fluorescence of ssDNA-QDs. While the complementary target H. pylori DNA was introduced, the ssDNA-QDs preferentially bound with the H. pylori DNA. The formation of dsDNA would alter the conformation of ssDNA and disturb the interaction between ssDNA and GO. Thus, the dsDNA-QDs/GO system exhibited a stronger fluorescence emission than that of the ssDNA-QDs/GO system. Under the optimized conditions, a linear correlation was established between the fluorescence intensity ratio I/I₀ and the concentration of H. pylori DNA in the range of 1.25-875pmolL^-1 with a detection limit of 0.46pmolL^-1. The proposed method was applied to the determination of H. pylori DNA sequence in milk samples with satisfactory results.

EQCM immunoassay for phosphorylated acetylcholinesterase as a biomarker for organophosphate exposures based on selective zirconia adsorption and enzyme-catalytic precipitation

A zirconia (ZrO(2)) adsorption-based immunoassay by electrochemical quartz crystal microbalance (EQCM) has been initially developed, aiming at the detection of phosphorylated acetylcholinesterase (Phospho-AChE) as a potential biomarker for bio-monitoring exposures to organophosphate (OP) pesticides and chemical warfare agents. Hydroxyl-derivatized monolayer was preferably chosen to modify the crystal serving as the template for directing the electro-deposition of ZrO(2) film with uniform nanostructures. The resulting ZrO(2) film was utilized to selectively capture Phospho-AChE from the sample media. Horseradish peroxidase (HRP)-labeled anti-AChE antibodies were further employed to recognize the captured phosphorylated proteins. Enzyme-catalytic oxidation of the benzidine substrate resulted in the accumulation of insoluble product on the functionalized crystal. Ultrasensitive EQCM quantification by mass-amplified frequency responses as well as rapid qualification by visual color changes of product could be thus, achieved. Moreover, 4-chloro-1-naphthol (CN) was studied as an ideal chromogenic substrate for the enzyme-catalytic precipitation. Experimental results show that the developed EQCM technique can allow for the detection of Phospho-AChE in human plasma with a detection limit of 0.020 nM. Such an EQCM immunosensing format opens a new door towards the development of simple, sensitive, and field-applicable biosensor for biologically monitoring low-level OP exposures.

Acoustic Wave (TSM) Biosensors: Weighing Bacteria

This chapter is focused on the development and use of acoustic wave biosensor platforms for the detection of bacteria, specifically those based on the thickness shear mode (TSM) resonator. We demonstrated the mechanical and electrical implications of bacterial positioning at the solid-liquid interface of a TSM biosensor and presented a model of the TSM with bacteria attached operating as coupled oscillators. The experiments and model provide an understanding of the nature of the signals produced by acoustic wave devices when they are used for testing bacteria. The paradox of “negative mass” could be a real threat to the interpretation of experimental results related to the detection of bacteria. The knowledge of the true nature of “negative mass” linked to the strength of bacteria attachment will contribute significantly to our understanding of the results of “weighing bacteria.” The results of this work can be used for bacterial detection and control of processes of bacterial settlement, bacterial colonization, biofilm formation, and bacterial infection in which bacterial attachment plays a role.

Electrochemical Detection of a Dengue-related Oligonucleotide Sequence Using Ferrocenium as a Hybridization Indicator

A simple method for electrochemical detection of a synthetic 20-bpoligonucleotide sequence related with dengue virus genome was developed. Acomplimentary DNA probe sequence was electrostatically immobilized onto a glassycarbon electrode modified with chitosan. Electrochemical detection of hybridizationbetween probe and target was performed by cyclic voltammetry, using ferrocene (Fc ) as ahybridization label. After hybridization, the peak current response of Fc oxidationincreased around 26%. A higher voltammetric decay rate constant (kd) and a lower half-lifeperiod (t_1/2) for the interaction of Fc with dsDNA compared to those with ssDNAquantitatively characterize the different strengths of interaction with both types of DNA.By combining the simplicity of DNA immobilization onto a chitosan film and suitablevoltammetric detection of hybridization concomitant with ferrocene attachment, a gooddiscrimination between ssDNA and dsDNA was obtained.

A survey of the 2001 to 2005 quartz crystal microbalance biosensor literature: applications of acoustic physics to the analysis of biomolecular interactions

The widespread exploitation of biosensors in the analysis of molecular recognition has its origins in the mid-1990s following the release of commercial systems based on surface plasmon resonance (SPR). More recently, platforms based on piezoelectric acoustic sensors (principally 'bulk acoustic wave' (BAW), 'thickness shear mode' (TSM) sensors or 'quartz crystal microbalances' (QCM)), have been released that are driving the publication of a large number of papers analysing binding specificities, affinities, kinetics and conformational changes associated with a molecular recognition event. This article highlights salient theoretical and practical aspects of the technologies that underpin acoustic analysis, then reviews exemplary papers in key application areas involving small molecular weight ligands, carbohydrates, proteins, nucleic acids, viruses, bacteria, cells and lipidic and polymeric interfaces. Key differentiators between optical and acoustic sensing modalities are also reviewed.

Enzyme immobilization on poly(ethylene-co-acrylic acid) films studied by quartz crystal microbalance with dissipation monitoring

In this study, we use the quartz crystal microbalance with dissipation monitoring (QCM-D) to study the immobilization of the enzyme horseradish peroxidase (HRP) on poly(ethylene-co-acrylic acid) (PEAA) films. The surface polarity of spin-coated PEAA films was varied by heat treatments in air or in a 30% NaOH aqueous solution leading to COOH-depleted or COOH-enriched surfaces, respectively. Two reaction schemes, direct adsorption and amine coupling, were employed for HRP immobilization on the two surfaces. The shifts in frequency and dissipation, Deltaf and DeltaD, measured by QCM-D and the ratio DeltaD/Deltaf were used to evaluate the binding amount and the conformation of the adsorbed enzyme. It is found that HRP immobilized via covalent linkages forms rigid and little dissipative films. In contrast, directly adsorbed HRP films exhibit a highly dissipative structure. HRP-catalyzed oxidation of the 4-chloro-1-naphthol in the presence of H(2)O(2) was used to characterize the catalytic activity of the HRP films. The results show that the enzymatic activity of the covalently immobilized HRP tends to be higher.

QCM–FIA with PGMA coating for dynamic interaction study of heparin and antithrombin III

In this work, we describe a method of constructing a film of linear poly(glycidyl methacrylate) (PGMA) polymer onto the surface of quartz crystal microbalance (QCM) electrode as a coating material that allows easy coupling of heparin molecules onto the electrode and facilitates the determination of the interaction between heparin and antithrombin III (AT III). The PGMA film was characterized with atomic force microscopy (AFM) and infra-red spectroscopy. The coupling of heparin was accomplished in one step solution reaction. A home-made quartz crystal microbalance-flow injection analysis (QCM-FIA) system with data analysis software developed in our laboratory was used to determine the interaction. The interactions between immobilized heparin and AT III were studied with various concentrations under various conditions. The obtained constants are kass=(1.49+/-0.12)x10(3)mol-1ls-1, kdiss=(3.94+/-0.63)x10(-2)s-1, KA=(3.82+/-0.33)x10(4)mol-1l.

Optimisation of the enzyme-based determination of hydrogen peroxide using the quartz crystal microbalance

The benzidines, 3,3'-diaminobenzidine (DAB), 3,3'-dimethoxybenzidine (DMOB) and 3,3',5,5'-tetramethylbenzidine (TMB) were enzymatically oxidised to detect hydrogen peroxide, using the quartz crystal. The oxidised product mainly remains in suspension, resulting in a limited quartz sensor signal. We have used two non-ionic surfactants, Tween 80 and Triton X-100 to interact with the oxidised amphiphilic products to increase their solubility and surface activity, and their ability to adsorb to the crystal surface. Tween 80 exhibits optimised response effects for DAB, DMOB and TMB at 0.012, 0.005, and 0.002% (v/v), respectively, whereas Triton X-100 is optimum at 0.1, 0.2, and 0.006% (v/v), respectively. As a result, we have improved the quartz crystal sensor sensitivity to peroxide. The use of Triton X-100 gave an improved response time.

Determination of monoenzyme- and bienzyme-stimulated precipitation by a cuvette-based surface plasmon resonance instrument

This paper describes the use of a cuvette-based surface plasmon resonance (SPR) instrument to measure biocatalyzed precipitation reactions. Enzyme-modified SPR sensor disk forms the base of a cuvette, in which the substrate solution is added with stirring. The determination of the substrate concentration relies on the measurement of SPR angle shift (Deltatheta(SPR)) induced by the deposition of the insoluble products without involving in any electrochemical reactions. As examples, horseradish peroxidase (HRP)-modified monoenzyme SPR sensor and HRP-glucose oxidase bienzyme-layered sensor are created to determine hydrogen peroxide and glucose via the catalyzed oxidation of 4-chloro-1-naphthol (4-CN). The deposition of the oxidized 4-CN-insoluble products leads to SPR angle shifts, which are linear to H(2)O(2) and glucose in the concentration ranges of 0.067-7.24 x 10(-5) and 0.7-8.3 x 10(-4) mM, respectively. The SPR sensitivities are greater than those of nonelectrochemical quartz crystal microbalance (QCM) (the parallel results in this study) and compare favorable with those of electrochemical QCM and electrochemical SPR methods. This study opens the field for enhanced SPR measurements by using biocatalyzed precipitation as a signal amplification method.