Rapid enrichment and detection of Staphylococcus aureus in milk using polyethyleneimine functionalized magnetic nanoparticles

Enhanced detection of Listeria monocytogenes using tetraethylenepentamine-functionalized magnetic nanoparticles and LAMP-CRISPR/Cas12a-based biosensor

BACKGROUND

Listeria monocytogenes is a pathogenic bacterium that can lead to severe illnesses, especially among vulnerable populations. Therefore, the development of rapid and sensitive detection methods is vital to prevent and manage foodborne diseases. In this study, we used tetraethylenepentamine (TEPA)-functionalized magnetic nanoparticles (MNPs) and a loop-mediated isothermal amplification (LAMP)-based CRISPR/Cas12a-based biosensor to concentrate and detect, respectively, L. monocytogenes. LAMP enables DNA amplification at a constant temperature, providing a highly suitable approach for point-of-care testing (POCT). The ability of CRISPR/Cas12a to cleave ssDNA reporter, coupled with TEPA-functionalized MNPs effective attachment to negatively charged bacteria, forms a promising biosensor.

RESULTS

The LAMP assay was meticulously developed by selecting specific primers and designing crRNA sequences targeting a specific region within the hly gene of L. monocytogenes. We selected primer and refined the amplification conditions by systematically exploring a temperature range from 59 °C to 69 °C, ensuring the attainment of optimal performance. This process was complemented by systematic optimization of LAMP-CRISPR/Cas12a system parameters. In particular, we successfully established the optimal ssDNA reporter concentrations (0-1.2 μM) and Cas12a-mediated trans-cleavage times (0-20 min), crucial components that underpin the effectiveness of the LAMP-CRISPR/Cas12a-based biosensor. For optimizing parameters in capturing L. monocytogenes using TEPA-functionalized MNPs, capture efficiency was significantly enhanced through adjustments in TEPA-functionalized MNPs concentration, incubation times, and magnetic separation duration. Large-volume (20 mL) magnetic separation exhibited a 10-fold sensitivity improvement over conventional methods. Utilizing TEPA-functionalized MNPs, the LAMP-CRISPR/Cas12a-based biosensor achieved detection limits of 100 CFU mL-1 in pure cultures and 100 CFU g-1 in enoki mushrooms.

SIGNIFICANCE

The integration of this novel technique with the LAMP-CRISPR/Cas12a-based biosensor enhances the accuracy and sensitivity of L. monocytogenes detection in foods, and it can be a promising biosensor for POCT. The 10-fold increase in sensitivity compared to conventional methods makes this approach a groundbreaking advancement in pathogenic bacteria detection for food safety and public health.

Multi-Probe Nano-Genomic Biosensor to Detect S. aureus from Magnetically-Extracted Food Samples

One of the most prevalent causes of foodborne illnesses worldwide is staphylococcal food poisoning. This study aimed to provide a robust method to extract the bacteria Staphylococcus aureus from food samples using glycan-coated magnetic nanoparticles (MNPs). Then, a cost-effective multi-probe genomic biosensor was designed to detect the nuc gene of S. aureus rapidly in different food matrices. This biosensor utilized gold nanoparticles and two DNA oligonucleotide probes combined to produce a plasmonic/colorimetric response to inform users if the sample was positive for S. aureus. In addition, the specificity and sensitivity of the biosensor were determined. For the specificity trials, the S. aureus biosensor was compared with the extracted DNA of Escherichia coli, Salmonella enterica serovar Enteritidis (SE), and Bacillus cereus. The sensitivity tests showed that the biosensor could detect as low as 2.5 ng/µL of the target DNA with a linear range of up to 20 ng/µL of DNA. With further research, this simple and cost-effective biosensor can rapidly identify foodborne pathogens from large-volume samples.

Cefepime-modified magnetic nanoparticles and enzymatic colorimetry for the detection of Listeria monocytogenes in lettuces

A novel sandwich assay for the detection of L. monocytogenes was designed based on antibiotic magnetic separation and enzymatic colorimetry. PEG-mediated cefepime functionalized magnetic nanoparticles (Cefe-PEG-MNPs) was reported for the first time to anchor L. monocytogenes cells with excellent bacterial capture capacity. The capture efficiency of L. monocytogenes in lettuce sample with high concentration (3.1 × 106 CFU/mL) was more than 73.8%. Anti-L. monocytogenes monoclonal antibody was adopted as the second anchoring agent to ensure the specificity for L. monocytogenes, which was co-modified with HRP on the surface of gold nanoparticles (AuNPs-HRP/mAb) to form AuNPs-HRP/mAb@L. monocytogenes@Cefe-PEG-MNPs sandwich complexes, and TMB was added to generate a colorimetric signal. The limit of detection in contaminated lettuce, watermelon juice, and fresh meat samples were both 3.1 × 102 CFU/mL, and the whole assay takes about 110 min. Based on the above facts, the proposed method has great potential for rapid separation and detection of pathogenic bacteria in food.

Magnetic Nanoseparation Technology for Efficient Control of Microorganisms and Toxins in Foods: A Review

Outbreaks of foodborne diseases mediated by food microorganisms and toxins remain one of the leading causes of disease and death worldwide. It not only poses a serious threat to human health and safety but also imposes a huge burden on health care and socioeconomics. Traditional methods for the removal and detection of pathogenic bacteria and toxins in various samples such as food and drinking water have certain limitations, requiring a rapid and sensitive strategy for the enrichment and separation of target analytes. Magnetic nanoparticles (MNPs) exhibit excellent performance in this field due to their fascinating properties. The strategy of combining biorecognition elements with MNPs can be used for fast and efficient enrichment and isolation of pathogens. In this review, we describe new trends and practical applications of magnetic nanoseparation technology in the detection of foodborne microorganisms and toxins. We mainly summarize the biochemical modification and functionalization methods of commonly used magnetic nanomaterial carriers and discuss the application of magnetic separation combined with other instrumental analysis techniques. Combined with various detection techniques, it will increase the efficiency of detection and identification of microorganisms and toxins in rapid assays.

Advances in magnetic nanoparticles for the separation of foodborne pathogens: Recognition, separation strategy, and application

Foodborne pathogens contamination is one of the main sources of food safety problems. Although the existing detection methods have been developed for a long time, the complexity of food samples is still the main factor affecting the detection time and sensitivity, and the rapid separation and enrichment of pathogens is still an objective to be studied. Magnetic separation strategy based on magnetic nanoparticles (MNPs) is considered to be an effective tool for rapid separation and enrichment of foodborne pathogens in food. Therefore, this study comprehensively reviews the development of MNPs in the separation of foodborne pathogens over the past decade. First, various biorecognition reagents for identification of foodborne pathogens and their modifications on the surface of MNPs are introduced. Then, the factors affecting the separation of foodborne pathogens, including the size of MNPs, modification methods, separation strategies and separation forms are discussed. Finally, the application of MNPs in integrated detection methods is reviewed. Moreover, current challenges and prospects of MNPs for the analysis of foodborne pathogens are discussed. Further research should focus on the design of multifunctional MNPs, the processing of large-scale samples, the simultaneous analysis of multiple targets, and the development of all-in-one small analytical device with separation and detection.

Rapid-Response Magnetic Enrichment Strategy for Significantly Improving Sensitivity of Multiplex PCR Analysis of Pathogenic Listeria Species

Listeria monocytogenes and Listeria ivanovii are important pathogenic Listeria spp. that cause infections in humans and animals. Establishing a rapid and sensitive method for the simultaneous screening of pathogenic Listeria spp. is of great significance for ensuring food safety. Multiplex polymerase chain reaction (mPCR) has been extensively reported to simultaneously detect several pathogens in food with high sensitivity, but a time-consuming pre-enrichment process is necessary. In this study, we report the usage of surface-modified polyethyleneimine-coated positively charged magnetic nanoparticles (PEI-MNPs) for rapid enrichment of pathogenic Listeria spp. through electrostatic interactions. The enrichment process takes only 10 min with high capture efficiency (more than 70%) at a wide pH range and ionic strength. Combined with mPCR analysis, the PEI-MNPs-mPCR strategy can simultaneously, rapidly, and sensitively detect pathogenic Listeria spp. without a time-consuming pre-concentration process. Under the optimal conditions, the detection limits of L. monocytogenes and L. ivanovii in lettuce were both as low as 101 CFU/mL, which was a hundred times lower than that without magnetic enrichment. In conclusion, the magnetic enrichment strategy based on charge interaction combined with mPCR analysis has great application potential in shortening the pre-concentration time of foodborne pathogens and improving the detection sensitivity.