Advance methods for the qualitative and quantitative determination of microorganisms

Hazardous Materials from Threats to Safety: Molecularly Imprinted Polymers as Versatile Safeguarding Platforms

Hazards associated with highly dangerous pollutants/contaminants in water, air, and land resources, as well as food, are serious threats to public health and the environment. Thus, it is imperative to detect or decontaminate, as risk-control strategies, the possible harmful substances sensitively and efficiently. In this context, due to their capacity to be specifically designed for various types of hazardous compounds, the synthesis and use of molecularly imprinted polymers (MIPs) have become widespread. By molecular imprinting, affinity sites with complementary shape, size, and functionality can be created for any template molecule. MIPs' unique functions in response to external factors have attracted researchers to develop a broad range of MIP-based sensors with increased sensitivity, specificity, and selectivity of the recognition element toward target hazardous compounds. Therefore, this paper comprehensively reviews the very recent progress of MIPs and smart polymer applications for sensing or decontamination of hazardous compounds (e.g., drugs, explosives, and biological or chemical agents) in various fields from 2020 to 2024, providing researchers with a rapid tool for investigating the latest research status.

Recent Development in Detection and Control of Psychrotrophic Bacteria in Dairy Production: Ensuring Milk Quality

Milk is an ideal environment for the growth of microorganisms, especially psychrotrophic bacteria, which can survive under cold conditions and produce heat-resistant enzymes. Psychrotrophic bacteria create the great problem of spoiling milk quality and safety. Several ways that milk might get contaminated by psychrotrophic bacteria include animal health, cowshed hygiene, water quality, feeding strategy, as well as milk collection, processing, etc. Maintaining the quality of raw milk is critically essential in dairy processing, and the dairy sector is still affected by the premature milk deterioration of market-processed products. This review focused on the recent detection and control strategies of psychrotrophic bacteria and emphasizes the significance of advanced sensing methods for early detection. It highlights the ongoing challenges in the dairy industry caused by these microorganisms and discusses future perspectives in enhancing milk quality through innovative rapid detection methods and stringent processing controls. This review advocates for a shift towards more sophisticated on-farm detection technologies and improved control practices to prevent spoilage and economic losses in the dairy sector.

Sensitive and on-Site Detection of Staphylococcus aureus Based on CRISPR/Cas 13a-Assisted Chemiluminescence Resonance Energy Transfer

Developing a specific, sensitive, rapid, and on-site method for detecting pathogenic bacteria in food samples is critical to ensuring public safety. This article demonstrates a CRISPR/Cas13a system and a chemiluminescence resonance energy transfer (CRET) (CRISPR/Cas 13a-assisted CRET)-based strategy for sensitive and on-site detection of pathogenic bacteria in real samples. Once the hybrid double strand of aptamerS. aureus-cRNA recognizes the target model bacteria of Staphylococcus aureus (S. aureus), the released cRNA would bind with CRISPR/Cas 13a to form a complex of cRNA-CRISPR/Cas 13a, which could cleave the RNA molecule in the detecting probe of horseradish peroxidase (HRP) modified-gold nanoparticles (AuNPs) linked by RNA (AuNPs-RNA-HRP), resulting in an enhanced chemiluminescence signal due to the CRET "OFF" phenomenon after introducing the chemiluminescence substrate of luminol. The CRISPR/Cas 13a-assisted CRET strategy successfully detected S. aureus in drinking water and milk with detection limits of 20 and 30 cfu/mL, respectively, within the recovery of 90.07-105.50%. Furthermore, after integrating with an immunochromatographic test strip (ICTS), the CRISPR/Cas 13a-assisted CRET strategy achieved the on-site detection of as low as 102 cfu/mL of S. aureus in drinking water and milk via a smartphone, which is about 10 times lower than that in the previously reported AuNPs-based colorimetric ICTS, demonstrating a convenient and sensitive detection method for S. aureus in real samples.

Bilayer Actuator Film for Urea Biosensing with Dual Responsiveness: Bending Actuation and Photonic Color Change

A noninvasive sweat-based biosensor was developed for urea detection using a photonic bilayer actuator film (BAF) consisting of an interpenetrating polymer network (IPN) as the active layer and a flexible poly(ethylene terephthalate) (PET) substrate as the passive layer (IPN/PET). The active IPN layer comprises intertwined solid-state cholesteric liquid crystal and poly(acrylic acid) (PAA) networks. Urease was immobilized in the PAA network in the IPN layer of the photonic BAF. The interaction with aqueous urea altered the curvature and photonic color of the photonic urease-immobilized IPN/PET (IPNurease/PET) BAF. The curvature (and wavelength of the photonic color) of the IPNurease/PET BAF increased linearly with urea concentration (Curea) in the range of Curea = 20-65 (and 30-65) mM with a limit of detection value of 1.42 (and 1.34) mM. The developed photonic IPNurease/PET BAF exhibited high selectivity toward urea and excellent spike test results with real human sweat. This novel IPNurease/PET BAF is promising because it enables battery-free, cost-effective, and visual detection-based analysis without the use of sophisticated instruments. Furthermore, the application of this photonic IPN/PET BAF can be easily extended to other biosensors by immobilizing other receptors on the IPN.

Genetic engineering of bacteriophages: Key concepts, strategies, and applications

Bacteriophages are the most abundant biological entity in the world and hold a tremendous amount of unexplored genetic information. Since their discovery, phages have drawn a great deal of attention from researchers despite their small size. The development of advanced strategies to modify their genomes and produce engineered phages with desired traits has opened new avenues for their applications. This review presents advanced strategies for developing engineered phages and their potential antibacterial applications in phage therapy, disruption of biofilm, delivery of antimicrobials, use of endolysin as an antibacterial agent, and altering the phage host range. Similarly, engineered phages find applications in eukaryotes as a shuttle for delivering genes and drugs to the targeted cells, and are used in the development of vaccines and facilitating tissue engineering. The use of phage display-based specific peptides for vaccine development, diagnostic tools, and targeted drug delivery is also discussed in this review. The engineered phage-mediated industrial food processing and biocontrol, advanced wastewater treatment, phage-based nano-medicines, and their use as a bio-recognition element for the detection of bacterial pathogens are also part of this review. The genetic engineering approaches hold great potential to accelerate translational phages and research. Overall, this review provides a deep understanding of the ingenious knowledge of phage engineering to move them beyond their innate ability for potential applications.

Pseudomonas aeruginosa Detection Using Conventional PCR and Quantitative Real-Time PCR Based on Species-Specific Novel Gene Targets Identified by Pangenome Analysis

Mining novel specific molecular targets and establishing efficient identification methods are significant for detecting Pseudomonas aeruginosa, which can enable P. aeruginosa tracing in food and water. Pangenome analysis was used to analyze the whole genomic sequences of 2017 strains (including 1,000 P. aeruginosa strains and 1,017 other common foodborne pathogen strains) downloaded from gene databases to obtain novel species-specific genes, yielding a total of 11 such genes. Four novel target genes, UCBPP-PA14_00095, UCBPP-PA14_03237, UCBPP-PA14_04976, and UCBPP-PA14_03627, were selected for use, which had 100% coverage in the target strain and were not present in nontarget bacteria. PCR primers (PA1, PA2, PA3, and PA4) and qPCR primers (PA12, PA13, PA14, and PA15) were designed based on these target genes to establish detection methods. For the PCR primer set, the minimum detection limit for DNA was 65.4 fg/μl, which was observed for primer set PA2 of the UCBPP-PA14_03237 gene. The detection limit in pure culture without pre-enrichment was 10⁵ colony-forming units (CFU)/ml for primer set PA1, 10³ CFU/ml for primer set PA2, and 10⁴ CFU/ml for primer set PA3 and primer set PA4. Then, qPCR standard curves were established based on the novel species-specific targets. The standard curves showed perfect linear correlations, with R² values of 0.9901 for primer set PA12, 0.9915 for primer set PA13, 0.9924 for primer set PA14, and 0.9935 for primer set PA15. The minimum detection limit of the real-time PCR (qPCR) assay was 10² CFU/ml for pure cultures of P. aeruginosa. Compared with the endpoint PCR and traditional culture methods, the qPCR assay was more sensitive by one or two orders of magnitude. The feasibility of these methods was satisfactory in terms of sensitivity, specificity, and efficiency after evaluating 29 ready-to-eat vegetable samples and was almost consistent with that of the national standard detection method. The developed assays can be applied for rapid screening and detection of pathogenic P. aeruginosa, providing accurate results to inform effective monitoring measures in order to improve microbiological safety.