A sensitive gold-nanorods-based nanobiosensor for specific detection of Campylobacter jejuni and Campylobacter coli

Nanobiosensors and their role in detection of adulterants and contaminants in food products

Nanotechnology is a multifaceted technical and scientific field undergoing a fast expansion. Nanoparticles, quantum dots, nanotubes, nanorods, nanowires, nanochips and many more are being increasingly used for fabrication of nanosensors and nanobiosensors to increase the sensitivity and selectivity of reactions. Food safety is an extremely important concern in food industries since it is directly associated with effect of food on human health. Here in our review, we have not only described the newest information regarding methods and use of nanomaterials for construction of nanosensors but also their detection range, limit of detection (LOD) and applications for food safety. Precise nanosensors having improved sensitivity and low limit of detection were discussed in brief. Review is primarily focused on nanosensors employed for detection of adulterants and contaminants in food products such as meat products, milk, fruit juices and water samples.

Evaluation of the prevalence of Aeromonas spp., Campylobacter spp., and Clostridioides difficile in immunocompromised children with diarrhea

AIM

Diarrhea is a common disease in immunocompromised patients and can be associated with greater morbidity and even mortality. Therefore, the present study was designed to determine the prevalence of Aeromonas spp., Campylobacter spp., and C. difficile among immunocompromised children.

METHODS

This study was conducted on 130 stool samples from patients with diarrhea who had defects in the immune system and were referred to Hazrat Masoumeh Children's Hospital in Qom. Demographic information, clinical symptoms, immune status, and duration of chemotherapy were also recorded for each child. DNAs were extracted from the stool, and then direct PCR assays were done by specific primers for the detection of Aeromonas spp., Campylobacter spp., and toxigenic C. difficile, including tcdA/B and cdtA/B genes. Co-infection in patients was also evaluated.

RESULTS

60.8% and 39.2% were male and female, respectively, with a m ± SD age of 56.72 ± 40.49 months. Most cases of immunocompromised states were related to Acute Lymphocytic Leukemia (77.7%) and Non-Hodgkin Lymphoma (14.6%). 93.1% of patients were undergoing chemotherapy during the study. Among patients, most clinical symptoms were related to bloody diarrhea (98.5%) and fever (92.3%). Based on PCR, 14.6, 9.2, and 1.5% were positive for Aeromonas spp., C. difficile, and C. jejuni, respectively. Among the C. difficile-positive cases, the tcdA gene was only detected in one patient. In total, three co-infections were identified, which included Aeromonas spp./C. difficile (tcdA+), C. jejuni/C. difficile, and C. jejuni/Aeromonas spp.

CONCLUSIONS

This is the first study in Iran to investigate the simultaneous prevalence of some pathogens in immunocompromised children with diarrhea. Because Aeromonas spp., Campylobacter spp., and C. difficile are not routinely detected in some laboratories, infections caused by them are underappreciated in the clinic. Our results showed that these pathogens are present in our region and can cause gastroenteritis in children, especially those with underlying diseases. Therefore, increasing the level of hygiene in some areas and controlling bacterial diarrheal diseases should be given more attention by health officials.

Review of Detection Limits for Various Techniques for Bacterial Detection in Food Samples

Foodborne illnesses can be infectious and dangerous, and most of them are caused by bacteria. Some common food-related bacteria species exist widely in nature and pose a serious threat to both humans and animals; they can cause poisoning, diseases, disabilities and even death. Rapid, reliable and cost-effective methods for bacterial detection are of paramount importance in food safety and environmental monitoring. Polymerase chain reaction (PCR), lateral flow immunochromatographic assay (LFIA) and electrochemical methods have been widely used in food safety and environmental monitoring. In this paper, the recent developments (2013-2023) covering PCR, LFIA and electrochemical methods for various bacterial species (Salmonella, Listeria, Campylobacter, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli)), considering different food sample types, analytical performances and the reported limit of detection (LOD), are discussed. It was found that the bacteria species and food sample type contributed significantly to the analytical performance and LOD. Detection via LFIA has a higher average LOD (24 CFU/mL) than detection via electrochemical methods (12 CFU/mL) and PCR (6 CFU/mL). Salmonella and E. coli in the Pseudomonadota domain usually have low LODs. LODs are usually lower for detection in fish and eggs. Gold and iron nanoparticles were the most studied in the reported articles for LFIA, and average LODs were 26 CFU/mL and 12 CFU/mL, respectively. The electrochemical method revealed that the average LOD was highest for cyclic voltammetry (CV) at 18 CFU/mL, followed by electrochemical impedance spectroscopy (EIS) at 12 CFU/mL and differential pulse voltammetry (DPV) at 8 CFU/mL. LOD usually decreases when the sample number increases until it remains unchanged. Exponential relations (R2 > 0.95) between LODs of Listeria in milk via LFIA and via the electrochemical method with sample numbers have been obtained. Finally, the review discusses challenges and future perspectives (including the role of nanomaterials/advanced materials) to improve analytical performance for bacterial detection.

Progress of Mesoporous Silica Coated Gold Nanorods for Biological Imaging and Cancer Therapy

For unique surface plasmon absorption and fluorescence characteristics, gold nanorods have been developed and widely employed in the biomedical field. However, limitations still exist due their low specific surface area, instability and tendency agglomerate in cytoplasm. Mesoporous silica materials have been broadly applied in field of catalysts, adsorbents, nanoreactors, and drug carriers due to its unique mesoporous structure, highly comparative surface area, good stability and biocompatibility. Therefore, coating gold nanorods with a dendritic mesopore channels can effectively prevent particle agglomeration, while increasing the specific surface area and drug loading efficiency. This review discusses the advancements of GNR@MSN in synthetic process, bio-imaging technique and tumor therapy. Additionally, the further application of GNR@MSN in imaging-guided treatment modalities is explored, while its promising superior application prospect is highlighted. Finally, the issues related to in vivo studies are critically examined for facilitating the transition of this promising nanoplatform into clinical trials.

Design of dot-blot hybridization assay for simultaneous detection of Campylobacter jejuni and Campylobacter coli: a preliminary study

Objectives

Campylobacters are a major cause of gastroenteritis worldwide. These are fastidious in culture and false negative results are seen in many clinical laboratories. Among molecular methods, the dot-blot technique is widely used for a variety of purposes, especially diagnostics. So, the authors aimed to detect C. jejuni and C. coli simultaneously using a dot-blot assay.

Methods

After evaluating the bioinformatics studies, a cadF-conserved fragment was selected for the design of primers and probe. DNAs from standard strains and a recombinant plasmid, prepared in this study, were used to assess the technique. The specificity of the method was also surveyed using DNAs from other enteric bacteria. The limit of detection was evaluated by recombinant plasmid and different concentrations of the designed probe.

Results

A 95-bp fragment of cadF was selected, and in silico analysis studies showed that it is conserved between both species. Also, the non-specific annealing of the primers and probe with other bacteria was not seen theoretically. The technique with recombinant plasmid as well as DNAs of standard strains created black spots on the membrane, confirming that the probe was correctly synthesized. No non-specific reactions with other bacterial species were observed (specificity=100%). The limit of detection of the test was determined to be 50 µg/ml.

Conclusions

This is the first study to simultaneously detect two important pathogens in the Campylobacter genus and was able to detect C. jejuni and C. coli with acceptable sensitivity and specificity.

Aptasensor for ovarian cancer biomarker detection using nanostructured gold electrodes

The development of an electrochemical aptasensor for the detection of CA125 as an ovarian cancer biomarker using gold nanostructures (GNs) modified electrodes is reported. The GNs were deposited on the surface of fluorine-doped tin oxide electrodes using a simple electrochemical method and the effects of pH and surfactant concentration on the topography and electrochemical properties of the resulting GNs modified electrodes were investigated. The electrodes were characterized using field-emission scanning electron microscopy and X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. The best electrode, in terms of the uniformity of the deposited GNs and the increase in electroactive surface area, was used for development of an aptasensor for CA125 tumor marker detection in human serum. Signal amplification was done by using aptamer-conjugated gold nanorods resulting in the detection limit of 2.6 U/ml and a linear range of 10 to 800 U/ml. The results showed that without the need for expensive antibodies, the developed aptasensor could specifically measure the clinically relevant concentrations of the tumor marker in human serum.

Nanomaterial Gas Sensors for Biosensing Applications: A Review

BACKGROUND

Nanomaterial is one of the most used materials for various gas sensing applications to detect toxic gases, human breath, and other specific gas sensing. One of the most important applications of nanomaterial based gas sensors is biosensing applications. In this review article, the gas sensors for biosensing are discussed on the basis of crystalline structure and different categories of nanomaterial.

METHODS

In this paper, firstly, rigorous efforts have been made to find out research questions by going through a structured and systematic survey of available peer reviewed high quality articles in this field. The papers related to nanomaterial based biosensors are then reviewed qualitatively to provide substantive findings from the recent developments in this field.

RESULTS

In this mini-review article, firstly, classifications of nanomaterial gas sensors have been presented on the basis of the crystalline structure of nanomaterial and different types of nanomaterial available for biosensing applications. Further, the gas sensors based on nanomaterial for biosensing applications are collected and reviewed in terms of their performance parameters such as sensing material used, target gas component, detection ranges (ppm-ppb), response time, operating temperature and method of detection, etc. The different nanomaterials possess slightly different sensing and morphological properties due to their structure; therefore, it can be said that a nanomaterial must be selected carefully for a particular application. The 1D nanomaterials show the best selectivity and sensitivity for gases available in low concentration ranges due to their miniaturised structure compared to 2D and 3D nanomaterials. However, these 2D and 3D nanomaterials also so good sensing properties compared to bulk semiconductor materials. The polymer and nanocomposites which are also discussed in this patent article have opened the door for future research and have great potential for new generation gas sensors for detecting biomolecules.

CONCLUSION

These nanomaterials extend great properties towards sensing the application of different gases for a lower concentration of particular gas particles. Nano polymer and nanocomposites have great potential to be used as gas sensors for the detection of biomolecules.

Gold Nanoparticle and Polymerase Chain Reaction (PCR)-Based Colorimetric Assay for the Identification of Campylobacter spp. in Chicken Carcass

Campylobacteriosis is a common cause of gastrointestinal disease. In this study, we suggest a general strategy of applying gold nanoparticles (AuNPs) in colorimetric biosensors to detect Campylobacter in chicken carcass. Polymerase chain reaction (PCR) was utilized for the amplification of the target genes, and the thiolated PCR products were collected. Following the blending of colloid AuNPs with PCR products, the thiol bound to the surface of AuNPs, forming AuNP-PCR products. The PCR products had a sufficient negative charge, which enabled AuNPs to maintain a dispersed formation under electrostatic repulsion. This platform presented a color change as AuNPs aggregate. It did not need additional time and optimization of pH for PCR amplicons to adhere to the AuNPs. The specificity of AuNPs of modified primer pairs for mapA from Campylobacter jejuni and ceuE from Campylobacter coli was activated perfectly (C. jejuni, p-value: 0.0085; C. coli, p-value: 0.0239) when compared to Salmonella Enteritidis and Escherichia coli as non-Campylobacter species. Likewise, C. jejuni was successfully detected from artificially contaminated chicken carcass samples. According to the sensitivity test, at least 15 ng/μL of Campylobacter PCR products or 1×10³ CFU/mL of cells in the broth was needed for the detection using the optical method.

Detection of Campylobacter jejuni Based on a Real-Time Fluorescence Loop-Mediated Isothermal Amplification Method

Campylobacter jejuni (C. jejuni), a foodborne pathogenic bacterium, is among the most prevalent causes of human gastroenteritis globally. We developed and evaluated a loop-mediated isothermal amplification (LAMP) method to detect C. jejuni. Outer primers and inner primers were designed based on the hipO gene. The ratio between the concentrations of the inner and outer primers and the reaction temperature were then optimized to achieve optimal assay conditions. The analytical specificity tests showed that, among 12 genera of 74 pure bacterial culture strains, only four C. jejuni isolates could be detected, whereas no amplification was observed in C. coli, C. lari, and the other 11 genera of foodborne pathogens (n = 70). Moreover, the LAMP assay showed a higher analytical sensitivity (34.2 fg μL⁻¹) than the conventional PCR method (342 fg μL⁻¹). The limit of detection of C. jejuni based on the LAMP assay was 10³ CFU g⁻¹ in the artificially spiked samples of chicken meat. In conclusion, the developed LAMP assay will be a powerful and practical tool for the fast, specific, and sensitive detection of C. jejuni.

Probe-free nanosensor for the detection of Salmonella using gold nanorods as an electroactive modulator

Salmonellosis is a symptomatic infection, a foodborne disease, caused by Salmonella that enters the body through the ingestion of contaminated food. In this study, a novel electrochemical biosensor integrated with gold nanorods (GNRs) was used to explore the interaction between in-house generated antibodies with Salmonella serovars. Under optimal conditions, the proposed immunosensor depicted a linear range of detection (1-1 × 10⁵) CFU/mL witha detection limit of 105 and 23 colony forming units (CFU) ofS. entandS. typhirespectively. The designed GNR/S. ent/S. typhi/Ab immunosensor was able to successfully detectS. ent/S. typhiin spiked meat and milk samples respectively, with a long shelf life, good repeatability, as well as reproducibility under optimised conditions. Along with the ease of fabrication, the developed electrode produced a highly specific response, and displayed negligible cross reactivity with other Salmonella species. Moreover, the established detection technique may be used as an alternative to conventional analytical approaches for rapid and sensitivediagnosis of Salmonellosis.

Transcriptome analysis of biofilm formation under aerobic and microaerobic conditions in clinical isolates of Campylobacter spp

It has been well documented that Campylobacter is the leading cause of foodborne infections and bacterial enteritis in high-income countries. The gastrointestinal tract of most warm-blooded animals, such as mammals and poultry, is prone to this pathogen. Infections caused by this bacterium in humans have usually been associated with the consumption of contaminated poultry meat. The important point about Campylobacter is that this bacterium has adapted to harsh environmental conditions along the food chain (poultry digestive tract to the consumer's plate) and developed an adapted mechanism to those conditions. This study aimed to compare the ability of Campylobacter jejuni and Campylobacter coli strains to form biofilms under aerobic and microaerobic conditions. The presence and expression of flab, FliS, DnaK, luxs, CsrA, Cj0688, and cosR genes involved in biofilm formation were investigated. Finally, the correlation between the biofilm forming ability of Campylobacter isolates and the presence/expression of selected genes has been explored. A significant correlation was observed between the presence and expression of some genes and the degree of biofilm formation in C. jejuni and C. coli isolates. A strong biofilm production was detected in strains harboring all selected genes with greater expression levels. The ability of C. jejuni and C. coli strains in biofilm formation is associated with the coordinated function and convergent expression of the selected genes. Seemingly, stress response- and motility-related genes have the most involvement in biofilm formation of C. jejuni and C. coli strains, while other genes have an accessory role in this phenomenon.

The application of DNA polymerases and Cas9 as representative of DNA-modifying enzymes group in DNA sensor design (review)

Rapid detection of nucleic acids (DNA or RNA) by inexpensive, selective, accurate, and highly sensitive methods is very important for biosensors. DNA-sensors based on DNA-modifying enzymes for fast determination and monitoring of pathogenic (Zika, Dengue, SARS-Cov-2 (inducer of COVID-19), human papillomavirus, HIV, etc.) viruses and diagnosis of virus-induced diseases is a key factor of this overview. Recently, DNA-modifying enzymes (Taq DNA polymerase, Phi29 DNA polymerase) have been widely used for the diagnosis of virus or pathogenic disease by gold standard (PCR, qPCR, RT-qPCR) methods, therefore, alternative methods have been reviewed. The main mechanisms of DNA metabolism (replication cycle, amplification) and the genomeediting tool CRISPR-Cas9 are purposefully discussed in order to address strategic possibility to design DNA-sensors based on immobilized DNA-enzymes. However, the immobilization of biologically active proteins on a gold carrier technique with the ability to detect viral or bacterial nucleic acids is individual for each DNA-modifying enzyme group, due to a different number of active sites, C and N terminal locations and arrangement, therefore, individual protocols based on the 'masking' of active sites should be elaborated for each enzyme.

A genomic concept in cellular interaction of clinical Campylobacter spp. with human epithelial colorectal adenocarcinoma cells

This study aimed to realize the genomic concept of cellular interaction of clinical Campylobacter spp. with human epithelial colorectal adenocarcinoma cells. It was indicated that the mean adherence and invasion rate of C.jejuni isolates was significantly higher than C.coli and the highest adhesion rate among the C.jejuni and C.coli belonged to strains harboring 4 (flaA, cadF, peb1A, and flpA) and 3 (flaA, cadF, and peb1A) adherence genes, respectively, which indicates that the adhesion potential of C.coli and C.jejuni strains is associated with the coordinate function and cumulative effect of selected virulence-associated genes. The highest invasion rate in C.jejuni (10.3%) and C.coli (8.4%) isolates belonged to strains which concomitantly contained 3 (ciaB, iamA, and tlp1) and 2 (ciaB and iamA) invasion-associated genes which emphasizes on the cooperative roles of these genes in C.jejuni and C.coli invasion to Caco-2 cells. The toxicity of C.jejuni for Caco-2 cells was proved higher than that of C.coli. There was a positive correlation between adherence, invasion and toxicity of both C.jejuni and C.coli isolates. Moreover, the expression levels of CDT-producing genes in C.jejuni strains was significantly higher than that of C.coli. The average cytotoxicity of the strains with all three CDT-encoding genes (cdtA, cdtB and cdtC) was statistically higher than those lacking one or more CDT subunits. A crucial contribution of CdtB to the cytotoxicity of Campylobacter strains was detected. Following the treatment of epithelial cells with C.jejuni or C.coli, IL-8 and TNF-α were significantly increased compared to untreated Caco-2 cells, and the highest IL-8 expression was observed in both C.jejuni and C.coli expressing all CDTs (cdtA, cdtB, and cdtC). We, for the first time, indicated the major contribution of TLR2 and TLR4 in campylobacter initiation of pathogenesis, while increased invasiveness and cytotoxicity was significantly associated with the increased expression of TLR4 in C.jejuni isolates.

Gold Nanorods for LSPR Biosensing: Synthesis, Coating by Silica, and Bioanalytical Applications

Nanoparticles made of coinage metals are well known to display unique optical properties stemming from the localized surface plasmon resonance (LSPR) phenomenon, allowing their use as transducers in various biosensing configurations. While most of the reports initially dealt with spherical gold nanoparticles owing to their ease of synthesis, the interest in gold nanorods (AuNR) as plasmonic biosensors is rising steadily. These anisotropic nanoparticles exhibit, on top of the LSPR band in the blue range common with spherical nanoparticles, a longitudinal LSPR band, in all respects superior, and in particular in terms of sensitivity to the surrounding media and LSPR-biosensing. However, AuNRs synthesis and their further functionalization are less straightforward and require thorough processing. In this paper, we intend to give an up-to-date overview of gold nanorods in LSPR biosensing, starting from a critical review of the recent findings on AuNR synthesis and the main challenges related to it. We further highlight the various strategies set up to coat AuNR with a silica shell of controlled thickness and porosity compatible with LSPR-biosensing. Then, we provide a survey of the methods employed to attach various bioreceptors to AuNR. Finally, the most representative examples of AuNR-based LSPR biosensors are reviewed with a focus put on their analytical performances.

Recent progress on developing of plasmon biosensing of tumor biomarkers: Efficient method towards early stage recognition of cancer

Cancer is the second most extended disease with an improved death rate over the past several time. Due to the restrictions of cancer analysis methods, the patient's real survival rate is unknown. Therefore, early stage diagnosis of cancer is crucial for its strong detection. Bio-analysis based on biomarkers may help to overcome the problem Biosensors with high sensitivity and specificity, low-cost, high analysis speed and minimum limit of detection are practical alternatives for laboratory tests. Surface plasmon resonance (SPR) is reaching a maturity level sufficient for their application in detection and determination cancer biomarkers in clinical samples. This review discusses main concepts and performance characteristics of SPR biosensor. Mainly, it focuses on newly emerged enhanced SPR biosensors towards high-throughput and ultrasensitive screening of cancer biomarkers such as PSA, α-fetoprotein, CEA, CA125, CA 15-3, HER2, ctDNA, ALCAM, hCG, VEGF, TNF, Interleukin, IFN-γ, CD24, CD44, Ferritin, COLIV using labeling processes with focusing on the future application in biomedical research and clinical diagnosis. This article reviews current status of the field, showcasing a series of early successes in the application of SPR for clinical bioanalysis of cancer related biomolecules and detailing a series of considerations regarding sensing schemes, exposing issues with analysis in biofluids, while providing an outlook of the challenges currently associated with plasmonic materials, bioreceptor selection, microfluidics, and validation of a clinical bioassay for applying SPR biosensors to clinical samples. Research opportunities are proposed to further advance the field and transition SPR biosensors from research proof-of-concept stage to actual clinical usage.

Electrochemical and Optical Biosensors for the Detection of Campylobacter and Listeria: An Update Look

Foodborne safety has aroused tremendous research interest in recent years because of a global public health problem. The rapid and precise detection of foodborne pathogens can reduce significantly infection diseases and save lives by the early initiation of an effective treatment. This review highlights current advances in the development of biosensors for detection of Campylobacter spp. and Listeria monocytogenes that are the most common causes of zoonosis. The consumption of pathogen contaminated food is responsible for humans hospitalization and death. The attention focused on the recognition elements such as antibodies (Ab), DNA probes and aptamers able to recognize cells, amplicons, and specific genes from different samples like bacteria, food, environment and clinical samples. Moreover, the review focused on two main signal-transducing mechanisms, i.e., electrochemical, measuring an amperometric, potentiometric and impedimetric signal; and optical, measuring a light signal by OLED (Organic Light Emitting Diode), SPR (Surface Plasmon Resonance), and Optical fiber. We expect that high-performance of devices being developed through basic research will find extensive applications in environmental monitoring, biomedical diagnostics, and food safety.