Impedance based detection of pathogenic E. coli O157:H7 using a ferrocene-antimicrobial peptide modified biosensor

Ultrasensitive and rapid count of Escherichia coli using magnetic nanoparticle probe under dark-field microscope

Background

Escherichia coli (E. coli) is one of the best-known zoonotic bacterial species, which pathogenic strain can cause infections in humans and animals. However, existing technologies or methods are deficient for quickly on-site identifying infection of E. coli before they breakout. Herein, we present an ultrasensitive and on-site method for counting E. coli using magnetic nanoparticle (MNP) probe under a dark-field in 30 min.

Results

The antibodies functionalized MNP, binding to E. coli to form a golden ring-like structure under a dark-field microscope, allowing for counting E. coli. This method via counting MNP-conjugated E. coli under dark-field microscope demonstrated the sensitivity of 6 CFU/μL for E. coli detection. Importantly, due to the advantages such as time-saving (only 30 min) and almost free of instrument (only require a portable microscope), our MNP-labeled dark-field counting strategy has the potential of being a universal tool for on-site quantifying a variety of pathogens with size ranges from a few hundreds of nanometers to a few micrometers.

Conclusion

In summary, the MNP-labeled dark-field counting strategy is a rapid, simple, sensitive as well as low-cost assay strategy, which has the potential of being a universal tool for on-site quantification of micrometer-size pathogens like E. coli.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1241-5) contains supplementary material, which is available to authorized users.

Photoelectrochemical Strategy for Discrimination of Microbial Pathogens Using Conjugated Polymers

A photoelectrochemical (PEC) biosensor for facile and sensitive identification of pathogenic microorganisms was developed. Cationic poly(phenylene vinylene) derivative (PPV) as photoelectrochemical active species was modified on the electrode. Under light irradiation, PPV could be excited and generate efficient photocurrent. PPV also had the ability to bind with negatively charged membrane of pathogenic microorganisms, which hindered the electron transfer between electrode and electrolyte. As a result, the photocurrent would decrease obviously. For E. coli, B. subtilis and C. albicans, the photocurrent density was reduced by 18, 33 and 59 %, respectively. Based on the reduction degree of the photocurrent after capturing different types of species of pathogenic microorganisms, a PEC sensor for discrimination of pathogenic microorganisms was realized.

Antimicrobial Peptides: Powerful Biorecognition Elements to Detect Bacteria in Biosensing Technologies

Bacterial infections represent a serious threat in modern medicine. In particular, biofilm treatment in clinical settings is challenging, as biofilms are very resistant to conventional antibiotic therapy and may spread infecting other tissues. To address this problem, biosensing technologies are emerging as a powerful solution to detect and identify bacterial pathogens at the very early stages of the infection, thus allowing rapid and effective treatments before biofilms are formed. Biosensors typically consist of two main parts, a biorecognition moiety that interacts with the target (i.e., bacteria) and a platform that transduces such interaction into a measurable signal. This review will focus on the development of impedimetric biosensors using antimicrobial peptides (AMPs) as biorecognition elements. AMPs belong to the innate immune system of living organisms and are very effective in interacting with bacterial membranes. They offer unique advantages compared to other classical bioreceptor molecules such as enzymes or antibodies. Moreover, impedance-based sensors allow the development of label-free, rapid, sensitive, specific and cost-effective sensing platforms. In summary, AMPs and impedimetric transducers combine excellent properties to produce robust biosensors for the early detection of bacterial infections.

Electrochemical Methodologies for the Detection of Pathogens

Bacterial infections remain one of the principal causes of morbidity and mortality worldwide. The number of deaths due to infections is declining every year by only 1% with a forecast of 13 million deaths in 2050. Among the 1400 recognized human pathogens, the majority of infectious diseases is caused by just a few, about 20 pathogens only. While the development of vaccinations and novel antibacterial drugs and treatments are at the forefront of research, and strongly financially supported by policy makers, another manner to limit and control infectious outbreaks is targeting the development and implementation of early warning systems, which indicate qualitatively and quantitatively the presence of a pathogen. As toxin contaminated food and drink are a potential threat to human health and consequently have a significant socioeconomic impact worldwide, the detection of pathogenic bacteria remains not only a big scientific challenge but also a practical problem of enormous significance. Numerous analytical methods, including conventional culturing and staining techniques as well as molecular methods based on polymerase chain reaction amplification and immunological assays, have emerged over the years and are used to identify and quantify pathogenic agents. While being highly sensitive in most cases, these approaches are highly time, labor, and cost consuming, requiring trained personnel to perform the frequently complex assays. A great challenge in this field is therefore to develop rapid, sensitive, specific, and if possible miniaturized devices to validate the presence of pathogens in cost and time efficient manners. Electrochemical sensors are well accepted powerful tools for the detection of disease-related biomarkers and environmental and organic hazards. They have also found widespread interest in the last years for the detection of waterborne and foodborne pathogens due to their label free character and high sensitivity. This Review is focused on the current electrochemical-based microorganism recognition approaches and putting them into context of other sensing devices for pathogens such as culturing the microorganism on agar plates and the polymer chain reaction (PCR) method, able to identify the DNA of the microorganism. Recent breakthroughs will be highlighted, including the utilization of microfluidic devices and immunomagnetic separation for multiple pathogen analysis in a single device. We will conclude with some perspectives and outlooks to better understand shortcomings. Indeed, there is currently no adequate solution that allows the selective and sensitive binding to a specific microorganism, that is fast in detection and screening, cheap to implement, and able to be conceptualized for a wide range of biologically relevant targets.

Fiber optic surface plasmon resonance sensor for detection of E. coli O157:H7 based on antimicrobial peptides and AgNPs-rGO

A fiber optic surface plasmon resonance (FOSPR) sensor was developed for detection of Escherichia coli O157:H7 (E. coli O157:H7) in water and juice, based on antimicrobial peptides (AMP), Magainin I, as recognition elements and silver nanoparticles-reduced graphene oxide (AgNPs-rGO) nanocomposites assisted signal amplification. The uniform AgNPs-rGO was fixed on the surface of optical fiber and covered with gold film. Not only was the SPR response greatly enhanced, but also the AgNPs was prevented from being oxidized. The FOSPR showed a sensitivity of about 1.5 times higher than that fabricated only with gold film. In the assay, Magainin I, immobilized on the surface of gold film, could specifically capture E. coli O157:H7, resulting in the wavelength shift of the SPR absorption peak. Under the optimized conditions, the SPR resonance wavelength exhibited a good linear relationship with natural logarithm of the target bacteria concentration in the range of 1.0 × 10³ to 5.0 × 10⁷ cfu/mL with the detection limit of 5.0 × 10² cfu/mL (S/N = 3). The FOSPR sensor showed good specificity for E. coli O157:H7 detection compared to other bacteria similar to the target bacterial species. Furthermore, the FOSPR sensor was successfully applied to the detection of E. coli O157:H7 in water, fruit and vegetable juice with the satisfactory recoveries of 88-110%. This assay for E. coli O157:H7 detection possesses high sensitivity, good selectivity, reproducibility and stability. In addition, the AMP based SPR biosensing methodology could be extended to detect a wide variety of foodborne pathogens. Therefore, the versatile method might become a potential alternative tool in food analysis and early clinical diagnosis.

Selective biosensing of Staphylococcus aureus using chitosan quantum dots

Selective biosensing of Staphylococcus aureus (S. aureus) using chitosan modified quantum dots (CTS@CdS QDs) in the presence of hydrogen peroxide is reported. The method is based on the intrinsic positive catalase activity of S. aureus. CTS@CdS quantum dots provide high dispersion in aqueous media with high fluorescence emission. Staphylococcus aureus causes a selective quenching of the fluorescence emission of CTS@CdS QDs in the presence of H₂O₂ compared to other pathogens such as Escherichia coli and Pseudomonas aeruginosa. The intrinsic enzymatic character of S. aureus (catalase positive) offers selective and fast biosensing. The present method is highly selective for positive catalase species and requires no expensive reagents such as antibodies, aptamers or microbeads. It could be extended for other species that are positive catalase.

A fully automated microfluidic-based electrochemical sensor for real-time bacteria detection

A fully automated microfluidic-based electrochemical biosensor was designed and manufactured for pathogen detection. The quantification of Escherichia coli was investigated with standard and nanomaterial amplified immunoassays in the concentration ranges of 0.99 × 10⁴3.98 × 10⁹ cfu mL^-1 and 103.97 × 10⁷ cfu mL^-1 which resulted in detection limits of 1.99 × 10⁴ cfu mL^-1 and 50 cfu mL^-1, respectively. The developed methodology was then applied for E. coli quantification in water samples using nanomaterial modified assay. Same detection limit for E. coli was achieved for real sample analysis with a little decrease on the sensor signal. Cross-reactivity studies were conducted by testing Shigella, Salmonella spp., Salmonella typhimurium and Staphylococcus aureus on E. coli specific antibody surface that confirmed the high specificity of the developed immunoassays. The sensor surface could be regenerated multiple times which significantly reduces the cost of the system. Our custom-designed biosensor is capable of detecting bacteria with high sensitivity and specificity, and can serve as a promising tool for pathogen detection.

Bridged Rebar Graphene functionalized aptasensor for pathogenic E. coli O78:K80:H11 detection

We report a novel fabrication method of functionalised Bridged Rebar Graphene (BRG) onto newly designed nanostructured aptasensor for label free impedimetric sensing of pathogenic bacteria E. coli O78:K80:H11. The chemical facilitated unscrolling of MWCNT and subsequent bridging with terephthalaldehyde (TPA) to form 3D-hierarchical BRG nanoconstruct exhibited synergistic effect by combining enhanced electrical properties and facile chemical functionality for stable bio-interface. The bacteria-DNA interactions were captured on BRG nanostructured electrode by using specific anti-E.coli DNA aptamer (K_d~ 14nM), screened by new in-situ developed SELEX method using phenylboronic acid on microtitre plate. The developed nanostructured aptasensor demonstrated a low detection limit and sensitivity of ~ 10¹cfu/mL towards E. coli O78:K80:H11 with a dynamic response range from 10¹ to 10⁶cfu/mL in water, juice and milk samples.

Charge-Directed Immobilization of Bacteriophage on Nanostructured Electrode for Whole-Cell Electrochemical Biosensors

A new type of carbon nanotube (CNT)-based impedimetric biosensing method has been developed for rapid and selective detection of live bacterial cells. A proof-of-concept study was conducted using T2 bacteriophage-based biosensors for electrochemical detection of Escherichia coli B. The T2 bacteriophage (virus) served as the biorecognition element, which was immobilized on polyethylenimine (PEI)-functionalized carbon nanotube transducer on glassy carbon electrode. Charge-directed, orientated immobilization of bacteriophage particles on carbon nanotubes was achieved through covalent linkage of phage capsid onto the carbon nanotubes. The presence of the immobilized phage on carbon nanotube-modified electrode was confirmed by fluorescence microscopy. Electrochemical impedance spectroscopy (EIS) was used to monitor the changes in the interfacial impedance due to the binding of E. coli B to T2 phage on the CNT-modified electrode. The detection was highly selective toward the B strain of E. coli as no signal was observed for the nonhost K strain of E. coli. The present achievable detection limit of the biosensor is 10³ CFU/mL.

An electrochemical immunosensor for sensitive detection of Escherichia coli O157:H7 by using chitosan, MWCNT, polypyrrole with gold nanoparticles hybrid sensing platform

An electrochemical immunosensor for the common food pathogen Escherichia coli O157:H7 was developed. This novel immunosensor based on the PPy/AuNP/MWCNT/Chi hybrid bionanocomposite modified pencil graphite electrode (PGE). This hybrid bionanocomposite platform was modified with anti-E. coli O157:H7 monoclonal antibody. The prepared bionanocomposite platform and immunosensor was characterized by using cyclic voltammetry (CV). Under the optimum conditions, the results have shown the order of the preferential selectivity of the method is gram negative pathogenic species E. coli O157:H7. Concentrations of E. coli O157:H7 from 3×10¹ to 3×10⁷cfu/mL could be detected. The detection limit was ∼30cfu/mL in PBS buffer. Briefly, we developed a high sensitive electrochemical immunosensor for specific detection of E. coli O157:H7 contamination with the use of sandwich assay evaluated in this study offered a reliable means of quantification of the bacteria. For the applications in food quality and safety control, our immunosensor showed reproducibility and stability.

An antimicrobial peptide-based colorimetric bioassay for rapid and sensitive detection of E. coli O157:H7

A colorimetric bioassay for sensitive detection ofE. coliO157:H7 using horseradish peroxidase labeled antimicrobial peptide as the signal reporter.

CdTe/CdS quantum dot-labeled fluorescent immunochromatography test strips for rapid detection of Escherichia coli O157:H7

Immunochromatography test strips have been widely used to detect foodborne pathogens due to their high sensitivity, stability and specificity, and the selection of the label is an important factor.

An unexpected use of ferrocene. A scanning electrochemical microscopy study of a toll-like receptor array and its interaction with E. coli

Toll-like receptor microarrays were investigated by scanning electrochemical microscopy with enhanced contrast from using ferrocene derivatives.

A novel method for the rapid detection of microbes in blood using pleurocidin antimicrobial peptide functionalized piezoelectric sensor

The rapid detection of microbes is critical in clinical diagnosis and food safety. Culture-dependent assays are the most widely used microbial detection methods, but these assays are time-consuming. In this study, a rapid microbial detection method was proposed using a pleurocidin/single-walled carbon nanotubes/interdigital electrode-multichannel series piezoelectric quartz crystal (pleurocidin/SWCNT/IDE-MSPQC) sensor. The selected pleurocidin antimicrobial peptide served as a recognition probe that exhibits broad-spectrum antimicrobial activity and the SWCNT acted as the electronic transducer and cross-linker for the immobilization of pleurocidin on the IDE. The response mechanism of the sensor was based on the specific interaction between pleurocidin and the microbe causing pleurocidin to detach from the SWCNT modified IDE, resulting in a sensitive frequency shift response of the MSPQC. Microbes that may be clinically present in the bloodstream during an infection were successfully detected by the proposed method within 15min. The developed strategy provides a new universal platform for the rapid detection of microbes.

Cell-SELEX Based Identification of an RNA Aptamer for Escherichia coli and Its Use in Various Detection Formats

Escherichia coli are important indicator organisms, used routinely for the monitoring of water and food safety. For quick, sensitive and real-time detection of E. coli we developed a 2'F modified RNA aptamer Ec3, by Cell-SELEX. The 31 nucleotide truncated Ec3 demonstrated improved binding and low nano-molar affinity to E. coli. The aptamer developed by us out-performs the commercial antibody and aptamer used for E. coli detection. Ec3(31) aptamer based E. coli detection was done using three different detection formats and the assay sensitivities were determined. Conventional Ec3(31)-biotin-streptavidin magnetic separation could detect E. coli with a limit of detection of 1.3 × 106 CFU/ml. Although, optical analytic technique, biolayer interferometry, did not improve the sensitivity of detection for whole cells, a very significant improvement in the detection was seen with the E. coli cell lysate (5 × 104 CFU/ml). Finally we developed Electrochemical Impedance Spectroscopy (EIS) gap capacitance biosensor that has detection limits of 2 × 104 CFU/mL of E. coli cells, without any labeling and signal amplification techniques. We believe that our developed method can step towards more complex and real sample application.

Bioinspired Synthesis of All-in-One Organic-Inorganic Hybrid Nanoflowers Combined with a Handheld pH Meter for On-Site Detection of Food Pathogen

With a mild elaborately bioinspired one-pot process, Con A-GOx-CaHPO4 nanoflowers are prepared. Employing the as-prepared all-in-one hybrid nanoflowers as signal tags, a simple but potentially powerful amplification biosensing technology for the detection of food pathogen with excellent simplicity, portability, sensitivity, and adaptability is achieved.

Design and Application of Antimicrobial Peptide Conjugates

Antimicrobial peptides (AMPs) are an interesting class of antibiotics characterized by their unique antibiotic activity and lower propensity for developing resistance compared to common antibiotics. They belong to the class of membrane-active peptides and usually act selectively against bacteria, fungi and protozoans. AMPs, but also peptide conjugates containing AMPs, have come more and more into the focus of research during the last few years. Within this article, recent work on AMP conjugates is reviewed. Different aspects will be highlighted as a combination of AMPs with antibiotics or organometallic compounds aiming to increase antibacterial activity or target selectivity, conjugation with photosensitizers for improving photodynamic therapy (PDT) or the attachment to particles, to name only a few. Owing to the enormous resonance of antimicrobial conjugates in the literature so far, this research topic seems to be very attractive to different scientific fields, like medicine, biology, biochemistry or chemistry.

Enzymatically Regulated Peptide Pairing and Catalysis for the Bioanalysis of Extracellular Prometastatic Activities of Functionally Linked Enzymes

Diseases such as cancer arise from systematical reconfiguration of interactions of exceedingly large numbers of proteins in cell signaling. The study of such complicated molecular mechanisms requires multiplexed detection of the inter-connected activities of several proteins in a disease-associated context. However, the existing methods are generally not well-equipped for this kind of application. Here a method for analyzing functionally linked protein activities is developed based on enzyme controlled pairing between complementary peptide helix strands, which simultaneously enables elaborate regulation of catalytic activity of the paired peptides. This method has been used to detect three different types of protein modification enzymes that participate in the modification of extracellular matrix and the formation of invasion front in tumour. In detecting breast cancer tissue samples using this method, up-regulated activity can be observed for two of the assessed enzymes, while the third enzyme is found to have a subtle fluctuation of activity. These results may point to the application of this method in evaluating prometastatic activities of proteins in tumour.

An Improved Ultrasensitive Enzyme-Linked Immunosorbent Assay Using Hydrangea-Like Antibody-Enzyme-Inorganic Three-in-One Nanocomposites

Protein-inorganic nanoflowers, composed of protein and copper(II) phosphate (Cu3(PO4)2), have recently grabbed people's attention. Because the synthetic method requires no organic solvent and because of the distinct hierarchical nanostructure, protein-inorganic nanoflowers display enhanced catalytic activity and stability and would be a promising tool in biocatalytical processes and biological and biomedical fields. In this work, we first coimmobilized the enzyme, antibody, and Cu3(PO4)2 into a three-in-one hybrid protein-inorganic nanoflower to enable it to possess dual functions: (1) the antibody portion retains the ability to specifically capture the corresponding antigen; (2) the nanoflower has enhanced enzymatic activity and stability to produce an amplified signal. The prepared antibody-enzyme-inorganic nanoflower was first applied in an enzyme-linked immunosorbent assay to serve as a novel enzyme-labeled antibody for Escherichia coli O157:H7 (E. coli O157:H7) determination. The detection limit is 60 CFU L(-1), which is far superior to commercial ELISA systems. The three-in-one antibody (anti-E. coli O157:H7 antibody)-enzyme (horseradish peroxidase)-inorganic (Cu3(PO4)2) nanoflower has some advantages over commercial enzyme-antibody conjugates. First, it is much easier to prepare and does not need any complex covalent modification. Second, it has fairly high capture capability and catalytic activity because it is presented as aggregates of abundant antibodies and enzymes. Third, it has enhanced enzymatic stability compared to the free form of enzyme due to the unique hierarchical nanostructure.

Biosensors based on modularly designed synthetic peptides for recognition, detection and live/dead differentiation of pathogenic bacteria

Rapid and sensitive detection of bacterial pathogens is critical for assessing public health, food and environmental safety. We report the use of modularly designed and site-specifically oriented synthetic antimicrobial peptides (sAMPs) as novel recognition agents enabling detection and quantification of bacterial pathogens. The oriented assembly of the synthetic peptides on electrode surfaces through an engineered cysteine residue coupled with impedimetric detection facilitated rapid and sensitive detection of bacterial pathogens with a detection limit of 10(2)CFU/mL for four bacterial strains including Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). The approach enabled differentiation between live and dead bacteria. The fabrication of the sAMPs functionalized surface and the importance of the sAMPs orientation for providing optimum recognition and detection ability against pathogens are discussed. The proposed methodology provides a universal platform for the detection of bacterial pathogens based on engineered peptides, as alternative to the most commonly used immunological and gene based assays. The method can also be used to fabricate antimicrobial coatings and surfaces for inactivation and screening of viable bacteria.

One-step immobilization antibodies using ferrocene-containing thiol aromatic aldehyde for the fabrication of a label-free electrochemical immunosensor

This work focuses on a facile method for antibody immobilization to fabricate a label-free electrochemical immunosensor using ferrocene-containing thiol aromatic aldehyde (FcSA) synthesized by us.

Immunosensor for the ultrasensitive and quantitative detection of bladder cancer in point of care testing

An ultrasensitive and real-time impedance based immunosensor has been fabricated for the quantitative detection of Galectin-1 (Gal-1) protein, a biomarker for the onset of multiple oncological conditions, especially bladder cancer. The chip consists of a gold annular interdigitated microelectrode array (3×3 format with a sensing area of 200µm) patterned using standard microfabrication processes, with the ability to electrically address each electrode individually. To improve sensitivity and immobilization efficiency, we have utilized nanoprobes (Gal-1 antibodies conjugated to alumina nanoparticles through silane modification) that are trapped on the microelectrode surface using programmable dielectrophoretic manipulations. The limit of detection of the immunosensor for Gal-1 protein is 0.0078mg/ml of T24 (Grade III) cell lysate in phosphate buffered saline, artificial urine and human urine samples. The normalized impedance variations show a linear dependence on the concentration of cell lysate present while specificity is demonstrated by comparing the immunosensor response for two different grades of bladder cancer cell lysates. We have also designed a portable impedance analyzing device to connect the immunosensor for regular checkup in point of care testing with the ability to transfer data over the internet using a personal computer. We believe that this diagnostic system would allow for improved public health monitoring and aid in early cancer diagnosis.

Sensitive detection of Escherichia coli O157:H7 using Pt-Au bimetal nanoparticles with peroxidase-like amplification

Escherichia coli O157:H7 is one of the most notorious foodborne pathogens causing serious disease at low infectious dose. To protect consumers from deadly foodborne E. coli O157:H7 infection, it is vital to develop a simple, reliable, sensitive and rapid method which can detect low level E. coli O157:H7 in foods at real-time. We have successfully developed a novel immunochromatographic assay (ICA) with enhanced sensitivity for the visual and quantitative detection of E. coli O157:H7. Sandwich-type immunoreactions were performed on the ICA, and Pt-Au bimetal nanoparticles (NPs) were accumulated on the test zone. The signal amplification is based on Pt-Au bimetal NPs possessing high peroxidase activity toward 3,3',5,5'-tetramethylbenzidine, which can produce characteristic colored bands and thus, enable visual detection of E. coli O157:H7 without instrumentation. The innovative aspect of this approach lies in the visualization and quantification of target pathogen through the detection of color intensity. Due to the excellent peroxidase activity of Pt-Au NPs, they emit strong visible color intensity in less than 1 min for visual observation even in low concentration range of E. coli O157:H7. Quantification was performed using a commercial assay meter. The sensitivity was improved more than 1000-folds compared to the conventional test strip based on colored gold-colloids. Although the feasibility was demonstrated using E. coli O157:H7 as a model analyte, this approach could be easily developed to be a universal signal amplification technique and applied to detection of a wide variety of foodborne pathogens and protein biomarkers.

Titanium Dioxide Nanoparticle-Based Interdigitated Electrodes: A Novel Current to Voltage DNA Biosensor Recognizes E. coli O157:H7

Nanoparticle-mediated bio-sensing promoted the development of novel sensors in the front of medical diagnosis. In the present study, we have generated and examined the potential of titanium dioxide (TiO₂) crystalline nanoparticles with aluminium interdigitated electrode biosensor to specifically detect single-stranded E.coli O157:H7 DNA. The performance of this novel DNA biosensor was measured the electrical current response using a picoammeter. The sensor surface was chemically functionalized with (3-aminopropyl) triethoxysilane (APTES) to provide contact between the organic and inorganic surfaces of a single-stranded DNA probe and TiO₂ nanoparticles while maintaining the sensing system’s physical characteristics. The complement of the target DNA of E. coli O157:H7 to the carboxylate-probe DNA could be translated into electrical signals and confirmed by the increased conductivity in the current-to-voltage curves. The specificity experiments indicate that the biosensor can discriminate between the complementary sequences from the base-mismatched and the non-complementary sequences. After duplex formation, the complementary target sequence can be quantified over a wide range with a detection limit of 1.0 x 10^-13M. With target DNA from the lysed E. coli O157:H7, we could attain similar sensitivity. Stability of DNA immobilized surface was calculated with the relative standard deviation (4.6%), displayed the retaining with 99% of its original response current until 6 months. This high-performance interdigitated DNA biosensor with high sensitivity, stability and non-fouling on a novel sensing platform is suitable for a wide range of biomolecular interactive analyses.

Peptide Functionalized Nanoplasmonic Sensor for Explosive Detection

In this study, a nanobiosensor for detecting explosives was developed, in which the peptide was synthesized with trinitrotoluene (TNT)-specific sequence and immobilized on nanodevice by Au-S covalent linkage, and the nanocup arrays were fabricated by nanoimprint and deposited with Au nanoparticles to generate localized surface plasmon resonance (LSPR). The device was used to monitor slight change from specific binding of 2,4,6-TNT to the peptide. With high refractive index sensing of ~104 nm/RIU, the nanocup device can detect the binding of TNT at concentration as low as 3.12 × 10-7 mg mL-1 by optical transmission spectrum modulated by LSPR. The nanosensor is also able to distinguish TNT from analogs of 2,4-dinitrotoluene and 3-nitrotoluene in the mixture with great selectivity. The peptide-based nanosensor provides novel approaches to design versatile biosensor assays by LSPR for chemical molecules.

Magnetic molecularly imprinted polymer nanoparticles based electrochemical sensor for the measurement of Gram-negative bacterial quorum signaling molecules (N-acyl-homoserine-lactones)

We have developed a novel and economical electrochemical sensor to measure Gram-negative bacterial quorum signaling molecules (AHLs) using magnetic nanoparticles and molecularly imprinted polymer (MIP) technology. Magnetic molecularly imprinted polymers (MMIPs) capable of selectively absorbing AHLs were successfully synthesized by surface polymerization. The particles were deposited onto a magnetic carbon paste electrode (MGCE) surface, and characterized by electrochemical measurements. Differential Pulse Voltammetry (DPV) was utilized to record the oxidative current signal that is characteristic of AHL. The detection limit of this assay was determined to be 8×10(-10)molL(-1) with a linear detection range of 2.5×10(-9)molL(-1) to 1.0×10(-7)molL(-1). This Fe3O4@SiO2-MIP-based electrochemical sensor is a valuable new tool that allows quantitative measurement of Gram-negative bacterial quorum signaling molecules. It has potential applications in the fields of clinical diagnosis or food analysis with real-time detection capability, high specificity, excellent reproducibility, and good stability.

Novel strategies to enhance lateral flow immunoassay sensitivity for detecting foodborne pathogens

Food contaminated by foodborne pathogens causes diseases, affects individuals, and even kills those affected individuals. As such, rapid and sensitive detection methods should be developed to screen pathogens in food. One current detection method is lateral flow immunoassay, an efficient technique because of several advantages, including rapidity, simplicity, stability, portability, and sensitivity. This review presents the format and principle of lateral flow immunoassay strip and the development of conventional lateral flow immunoassay for detecting foodborne pathogens. Furthermore, novel strategies that can be applied to enhance the sensitivity of lateral flow immunoassay to detect foodborne pathogens are presented; these strategies include innovating new label application, designing new formats of lateral flow immunoassay, combining with other methods, and developing signal amplification systems. With these advancements, detection sensitivity and detection time can be greatly improved.

Optical and dielectric sensors based on antimicrobial peptides for microorganism diagnosis

Antimicrobial peptides (AMPs) are natural compounds isolated from a wide variety of organisms that include microorganisms, insects, amphibians, plants, and humans. These biomolecules are considered as part of the innate immune system and are known as natural antibiotics, presenting a broad spectrum of activities against bacteria, fungi, and/or viruses. Technological innovations have enabled AMPs to be utilized for the development of novel biodetection devices. Advances in nanotechnology, such as the synthesis of nanocomposites, nanoparticles, and nanotubes have permitted the development of nanostructured platforms with biocompatibility and greater surface areas for the immobilization of biocomponents, arising as additional tools for obtaining more efficient biosensors. Diverse AMPs have been used as biological recognition elements for obtaining biosensors with more specificity and lower detection limits, whose analytical response can be evaluated through electrochemical impedance and fluorescence spectroscopies. AMP-based biosensors have shown potential for applications such as supplementary tools for conventional diagnosis methods of microorganisms. In this review, conventional methods for microorganism diagnosis as well new strategies using AMPs for the development of impedimetric and fluorescent biosensors are highlighted. AMP-based biosensors show promise as methods for diagnosing infections and bacterial contaminations as well as applications in quality control for clinical analyses and microbiological laboratories.