Immunosensor based on electrodeposition of gold-nanoparticles and ionic liquid composite for detection of Salmonella pullorum

Recent Advances in Signal Amplification to Improve Electrochemical Biosensing for Infectious Diseases

The field of infectious disease diagnostics is burdened by inequality in access to healthcare resources. In particular, “point-of-care” (POC) diagnostics that can be utilized in non-laboratory, sub-optimal environments are appealing for disease control with limited resources. Electrochemical biosensors, which combine biorecognition elements with electrochemical readout to enable sensitive and specific sensing using inexpensive, simple equipment, are a major area of research for the development of POC diagnostics. To improve the limit of detection (LOD) and selectivity, signal amplification strategies have been applied towards these sensors. In this perspective, we review recent advances in electrochemical biosensor signal amplification strategies for infectious disease diagnostics, specifically biosensors for nucleic acids and pathogenic microbes. We classify these strategies into target-based amplification and signal-based amplification. Target-based amplification strategies improve the LOD by increasing the number of detectable analytes, while signal-based amplification strategies increase the detectable signal by modifying the transducer system and keep the number of targets static. Finally, we argue that signal amplification strategies should be designed with application location and disease target in mind, and that the resources required to produce and operate the sensor should reflect its proposed application, especially when the platform is designed to be utilized in low-resource settings. We anticipate that, based on current technologies to diagnose infectious diseases, incorporating signal-based amplification strategies will enable electrochemical POC devices to be deployed for illnesses in a wide variety of settings.

Electrochemical immunosensor for detection of avian Salmonellosis based on electroactive reduced graphene oxide (rGO) modified electrode

A novel reduced graphene oxide based (rGO) fluorine doped tin oxide (FTO) electrode was fabricated to explore the interaction of Salmonella serovars (Salmonella gallinarum, and Salmonella pullorum) with specific antibodies. Reduced graphene oxide (rGO) was labelled with S. gal and S. pul-Ab via carbodiimide activation. The biophysical characterization of fabricated electrode was done by Fourier-transform infrared spectroscopy (FT-IR), Raman Spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDX), cyclic voltammetry (CV), and differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The optimization of fabricated electrode was done for various physico-chemical parameters. Under optimum conditions, the immunosensor exhibited a linear detection range (1- 1 × 105 cells) with 37 and 25 viable cells of S. gal and S. pul, respectively. The developed FTO/rGO/S.gal or S.pul-Ab/Ag immunosensor successfully detected S. gal or S. pul up to 51 and 37 cells, respectively in faecal samples and 218 and 173 cells, respectively in meat samples. FTO/rGO/S.gal or S.pul-Ab/Ag immunosensor revealed satisfactory response, and exhibited relatively low detection limit along with reproducibility. The proposed sensing model can be used as an alternative quantitative tool for the rapid and sensitive detection of Salmonellosis in meat and faecal samples.

New analytical methods using carbon-based nanomaterials for detection of Salmonella species as a major food poisoning organism in water and soil resources

Salmonella is one of the most prevalent causing agents of food- and water-borne illnesses, posing an ongoing public health threat. These food-poisoning bacteria contaminate the resources at different stages such as production, aggregation, processing, distribution, as well as marketing. According to the high incidence of salmonellosis, effective strategies for early-stage detection are required at the highest priority. Since traditional culture-dependent methods and polymerase chain reaction are labor-intensive and time-taking, identification of early and accurate detection of Salmonella in food and water samples can prevent significant health economic burden and lessen the costs. The immense potentiality of biosensors in diagnosis, such as simplicity in operation, the ability of multiplex analysis, high sensitivity, and specificity, have driven research in the evolution of nanotechnology, innovating newer biosensors. Carbon nanomaterials enhance the detection sensitivity of biosensors while obtaining low levels of detection limits due to their possibility to immobilize huge amounts of bioreceptor units at insignificant volume. Moreover, conjugation and functionalization of carbon nanomaterials with metallic nanoparticles or organic molecules enables surface functional groups. According to these remarkable properties, carbon nanomaterials are widely exploited in the development of novel biosensors. To be specific, carbon nanomaterials such as carbon nanotubes, graphene and fullerenes function as transducers in the analyte recognition process or surface immobilizers for biomolecules. Herein the potential application of carbon nanomaterials in the development of novel Salmonella biosensors platforms is reviewed comprehensively. In addition, the current problems and critical analyses of the future perspectives of Salmonella biosensors are discussed.

Current State of Development of Biosensors and Their Application in Foodborne Pathogen Detection

ABSTRACT

Foodborne disease outbreaks continue to be a major public health and food safety concern. Testing products promptly can protect consumers from foodborne diseases by ensuring the safety of food before retail distribution. Fast, sensitive, and accurate detection tools are in great demand. Therefore, various approaches have been explored recently to find a more effective way to incorporate antibodies, oligonucleotides, phages, and mammalian cells as signal transducers and analyte recognition probes on biosensor platforms. The ultimate goal is to achieve high specificity and low detection limits (1 to 100 bacterial cells or piconanogram concentrations of toxins). Advancements in mammalian cell-based and bacteriophage-based sensors have produced sensors that detect low levels of pathogens and differentiate live from dead cells. Combinations of biotechnology platforms have increased the practical utility and application of biosensors for detection of foodborne pathogens. However, further rigorous testing of biosensors with complex food matrices is needed to ensure the utility of these sensors for point-of-care needs and outbreak investigations.

HIGHLIGHTS

Self-made Salmonella Pullorum agglutination antigen development and its potential practical application

Pullorum disease caused by Salmonella Pullorum is one of the most important infectious diseases in the poultry industry worldwide, which leads to serious economic losses in many developing countries because of its high mortality rate in young chicks. The traditional slide agglutination test with low cost, fast reaction, and on-site detection has been widely used in the diagnosis of Pullorum disease. However, in practice, the test performance is with the disadvantages of false positive results and unstable detection results. In this paper, we developed self-made agglutination antigens prepared by local isolates in the poultry farm and compare the detection performance with commercial agglutination antigens (China Institute of Veterinary Drug Control) and Group D Salmonella ELISA kit (BioChek UK Ltd). The results of detecting 200 serum samples indicated that the consistency of commercial agglutination antigen detecting in 2 times was only 79.5%. Using the ELISA kit as the reference method, the commercial agglutination antigen detecting results of the Kappa test were only moderately consistent (0.58 ∼ 0.59). Meanwhile, positive and total coincidence rates of the self-made agglutination antigen test with more reliable repeat could reach 97.4 and 88%, respectively, and the result of Kappa test was highly consistent (0.75). The Receiver Operating Characteristic curve analysis clarified that the area under the receiver-operating-characteristic curve values of self-made and commercial agglutination antigen tests could reach 0.861 and 0.804, respectively. These results were coincident when detecting known positive serum from the infected chickens. It's worth mentioning that the visible positive reaction of self-made agglutination antigen test appeared faster and stronger than commercial antigen test. In conclusion, self-made Salmonella Pullorum agglutination antigen developed in this study was much better than commercial agglutination antigen and is expected to be a valuable tool in the diagnosis of the epidemiology of Salmonella Pullorum.

An electrochemical immunosensor for the corona virus associated with the Middle East respiratory syndrome using an array of gold nanoparticle-modified carbon electrodes

The Middle East respiratory syndrome corona virus (MERS-CoV) is highly pathogenic. An immunosensor for the determination of MERS-CoV is described here. It is based on a competitive assay carried out on an array of carbon electrodes (DEP) modified with gold nanoparticles. Recombinant spike protein S1 was used as a biomarker for MERS CoV. The electrode array enables multiplexed detection of different CoVs. The biosensor is based on indirect competition between free virus in the sample and immobilized MERS-CoV protein for a fixed concentration of antibody added to the sample. Voltammetric response is detected by monitoring the change in the peak current (typically acquired at a working potential of −0.05 V vs. Ag/AgCl) after addition of different concentrations of antigen against MERS-CoV. Electrochemical measurements using ferrocyanide/ferricyanide as a probe were recorded using square wave voltammetry (SWV). Good linear response between the sensor response and the concentrations from 0.001 to 100 ng.mL⁻¹ and 0.01 to 10,000 ng.mL⁻¹ were observed for MERS-CoV and HCoV, respectively. The assay was performed in 20 min with detection limit as low as 0.4 and 1.0 pg.mL⁻¹ for HCoV and MERS-CoV, respectively. The method is highly selective over non-specific proteins such as Influenza A and B. The method is single-step, sensitive and accurate. It was successfully applied to spiked nasal samples.

Graphical abstract

An electrochemical immunosensor for the corona virus associated with the Middle East respiratory syndrome using an array of gold nanoparticle-modified carbon electrodes

The Middle East respiratory syndrome corona virus (MERS-CoV) is highly pathogenic. An immunosensor for the determination of MERS-CoV is described here. It is based on a competitive assay carried out on an array of carbon electrodes (DEP) modified with gold nanoparticles. Recombinant spike protein S1 was used as a biomarker for MERS CoV. The electrode array enables multiplexed detection of different CoVs. The biosensor is based on indirect competition between free virus in the sample and immobilized MERS-CoV protein for a fixed concentration of antibody added to the sample. Voltammetric response is detected by monitoring the change in the peak current (typically acquired at a working potential of -0.05 V vs. Ag/AgCl) after addition of different concentrations of antigen against MERS-CoV. Electrochemical measurements using ferrocyanide/ferricyanide as a probe were recorded using square wave voltammetry (SWV). Good linear response between the sensor response and the concentrations from 0.001 to 100 ng.mL^-1 and 0.01 to 10,000 ng.mL^-1 were observed for MERS-CoV and HCoV, respectively. The assay was performed in 20 min with detection limit as low as 0.4 and 1.0 pg.mL^-1 for HCoV and MERS-CoV, respectively. The method is highly selective over non-specific proteins such as Influenza A and B. The method is single-step, sensitive and accurate. It was successfully applied to spiked nasal samples. Graphical abstract An electrochemical immunoassay is described for the Middle East Respiratory Syndrome Corona Virus (MERS-CoV). The method is based on a competitive assay carried out on a carbon array electrodes (DEP) nanostructured with gold nanoparticles. The array electrodes enable the multiplexed detection of different types of Corona Virus.

Biosensor Applications of Electrodeposited Nanostructures

The development of biosensors for a range of analytes from small molecules to proteins to oligonucleotides is an intensely active field. Detection methods based on electrochemistry or on localized surface plasmon responses have advanced through using nanostructured electrodes prepared by electrodeposition, which is capable of preparing a wide range of different structures. Supported nanoparticles can be prepared by electrodeposition through applying fixed potentials, cycling potentials, and fixed current methods. Nanoparticle sizes, shapes, and surface densities can be controlled, and regular structures can be prepared by electrodeposition through templates. The incorporation of multiple nanomaterials into composite films can take advantage of the superior and potentially synergistic properties of each component. Nanostructured electrodes can provide supports for enzymes, antibodies, or oligonucleotides for creating sensors against many targets in areas such as genomic analysis, the detection of protein antigens, or the detection of small molecule metabolites. Detection can also be performed using electrochemical methods, and the nanostructured electrodes can greatly enhance electrochemical responses by carefully designed schemes. Biosensors based on electrodeposited nanostructures can contribute to the advancement of many goals in bioanalytical and clinical chemistry.

Colorimetric determination of melamine in milk using unmodified silver nanoparticles

Melamine is nitrogen rich chemical compound used as an adulterant in dairy products by unscrupulous people to increase the apparent protein content. This incident prompted the researchers to develop simple methods for easy detection of melamine in food samples. In the present paper, we report a simple and sensitive colorimetric method for detection of melamine in milk based on silver nanoparticles. This method relies upon the principle that melamine causes the aggregation of silver nanoparticles, resulting in abrupt color change from yellow to red under optimized conditions. The concentration of melamine in adulterated sample can be quantitated by monitoring the absorption spectra of silver nanoparticles using ultraviolet-visible (UV-Vis) spectrometer. The present colorimetric method which utilizes silver nanoparticles of 35 nm can reliably detect melamine down to a concentration of 0.04 mg l(-1).

Electrochemical immunosensors and their recent nanomaterial-based signal amplification strategies: a review

In recent years, tremendous advances have been made in biosensors based on nanoscale electrochemical immunosensors for use in the fields of agriculture, food safety, biomedicine, quality control, and environmental and industrial monitoring.

A sandwich electrochemical immunoassay for Salmonella pullorum and Salmonella gallinarum based on a AuNPs/SiO2/Fe3O4adsorbing antibody and 4 channel screen printed carbon electrode electrodeposited gold nanoparticles

A: The synthesis of Fe₃O₄/SiO₂–SH; B: AuNPs and the Ab₁link with Fe₃O₄/SiO₂–SH; C: functions of IMB for antigen enrichment and separation from the sample, and HRP-antibody for the immunoreaction; D: the principle of the electrochemical detection.