Ultrasensitive Detection of Multidrug-Resistant Bacteria Based on Boric Acid-Functionalized Fluorescent MOF@COF

Live bacteria detection with high specificity by utilizing Eu3+@MIL-53 (Al) and bacteriophages-based fluorescence biosensor

Pseudomonas aeruginosa (PA) infection poses a significant threat to human health and the economy, with the issue of drug resistance becoming increasingly severe. How to quickly, accurately, and inexpensively detect PA and differentiate live bacteria from dead ones is crucial for clinical follow-up treatment. To this end, we have developed a biosensor based on fluorescent metal-organic frameworks (MOFs) (Eu3+@MIL-53(Al)) and specific-phages for PA detection, where the Eu3+@MIL-53(Al) prepared by one-pot method exhibits excellent fluorescence properties. By covalently binding specific phages isolated from hospital wastewater to the EuMOF surface, we constructed a fluorescent biosensor capable of detecting PA within 15 min, with a sensitivity threshold of 2 CFU/mL. Notably, this biosensor demonstrates high specificity, accurately quantifying live PA in complex bacterial mixtures and distinguishing live from dead bacteria. Its practical application has been validated in clinical blood and stool samples. As a novel platform for clinical microbial monitoring, the Eu3+@MIL-53(Al)-phage biosensor not only holds substantial economic potential but also carries significant public health implications.

Progress in the application of functionalized covalent organic framework for bioanalysis

As a new type of crystalline porous polymer materials, covalent organic frameworks (COFs) with their unique features such as large surface area, tunable pore sizes, strong π-π stacking effect and size exclusion effects, have attracted wide attention in the analytical field. Due to the lack of catalytically active metal centers in bare COFs, functionalized COFs that are hybridized or modified with nanomaterials improve reactive activation and show better analytical performance for a variety of detection scenarios with complex analytes. Herein, we focused on the functionalized COFs used in bioanalysis ranging from nucleic acids, peptides, and proteins, to microorganisms, and discussed the functionalization strategy and unique structures and properties applied in the different stages of biosensing and advantages compared to other hybrid materials. Finally, challenges and future research directions of functionalized COFs in bioanalysis are discussed.

A Highly Sensitive Giant Magnetoresistive (GMR) Biosensor Based on the Magnetic Flux Concentrator Effect

Magnetic biosensors have wide applications in biological target detection due to their advantages such as low background noise, convenient detection, and low requirements for sample pretreatment. However, existing magnetic biosensors still have the drawback of low sensitivity compared to optical and electrochemical biosensors. This paper presents the novel design of a high-sensitivity magnetic biosensor by utilizing the magnetic field line convergence effect, which was applied to bacterial detection. The results indicate that it can achieve a detection limitation of 10 CFU/mL, demonstrating that it can be implemented in high-sensitivity biological target detection.

Curcumin - a natural colorant-based pH indicator for molecular diagnostics

Loop-mediated isothermal amplification (LAMP) provides highly selective and sensitive DNA amplification and generates hydrogen ions as a byproduct under weakly buffered conditions, causing the solutions' pH to decrease from the initial basic to an acidic environment. This distinctive feature allows the color of the amplified DNA solution to change readily when suitable pH indicators are employed. In this study, curcumin, a biodegradable, non-toxic, and natural colorant, was used as a pH indicator to visually identify LAMP-amplified Staphylococcus aureus (S. aureus) and Streptococcus pneumoniae (S. pneumoniae). Curcumin (10 mM) displayed a unique color difference between negative (red) and positive (yellow) samples, and the detection process was completed within 30 s, demonstrating the effectiveness of using curcumin for on-site diagnostics. Under optimum conditions, curcumin enabled S. aureus and S. pneumoniae detection as low as 10 fg μL-1 and 1 pg μL-1, respectively, due to its unique halochromic properties. Owing to its adaptability, ease of use, and rapid visual detection, the introduced colorimetric pH-based LAMP method can be employed as a practical alternative to conventional colorimetry for infectious pathogen identification in both laboratory and field settings.

Ultrasensitive detection of Vibrio parahaemolyticus based on boric acid-functionalized Eu (III)-based metal-organic framework

This study intends to create a ratiometric fluorescence probe utilizing aptamers for the detection of Vibrio parahaemolyticus (V. parahaemolyticus) in aquatic products. In this design, aptamer-functionalized magnetic nanoparticles specifically capture V. parahaemolyticus, while boric acid on Eu (III)-Based Metal-Organic Framework (Eu-MOF) interacts with glycolipids present on bacterial cells, thereby achieving dual recognition of V. parahaemolyticus. This fluorescent probe quantitatively detects V. parahaemolyticus by measuring the intensity of ratio fluorescence. The sensor demonstrates a detection range from 77 to 7.7 × 107 CFU/mL, possessing a detection threshold down to 1 CFU/mL. Moreover, the developed method based on Eu-MOF had been successfully applied to real samples. To achieve rapid on-site detection of V. parahaemolyticus, the study designed a portable smartphone sensor that confirms its capability for rapidly detecting pathogens and contributes significantly to establishing a system for regulating safety in detecting food and environment.

A review of research progress on COF-based biosensors in pathogen detection

Despite the availability of various detection tools, the rapid identification and accurate detection of pathogens remain a major challenge in public health management. Covalent organic frameworks (COFs), which are crystalline conjugated organic polymers with considerable application potential, offer unique advantages in several fields owing to their highly ordered structure, large specific surface area, stable chemical properties, and tunable pore microenvironment. In recent years, with the rapid development of biosensing technology, COF application in the field of pathogen detection has attracted extensive attention. Herein, the properties, applications, and synthesis methods of COFs are briefly described, and the application types and basic principles of COFs in building an efficient and sensitive pathogen detection platform are emphatically discussed. Overall, we analyze the current challenges associated with COF-based biosensors in pathogen detection and look forward to their broad application prospects in biomedicine and public health in future.

Aptamer-Modified MOFs (Aptamer@MOF) for Efficient Detection of Bacterial Pathogens: A Review

Detecting pathogenic bacteria is crucial for controlling infectious diseases, safeguarding public health, and ensuring food and water safety. The integration of metal-organic frameworks (MOFs) with aptamers offers a promising approach to enhance bacterial detection. Aptamers provide high specificity for target recognition, while MOFs contribute tunable porous structures and stability, forming robust biosensors. This synergy improves sensitivity, selectivity, and versatility, enabling real-time and quantitative detection. Applications span food safety, environmental monitoring, and point-of-care diagnostics. This review highlights the significance of aptamer@MOF biosensors, discussing various detection techniques and aptamer immobilization methods. It also addresses challenges like enhancing sensitivity, improving selectivity, minimizing interference, ensuring stability, and advancing scalability for real-world applications. Additionally, limitations such as the need for miniaturization, multimode detection, and multiplex analysis are highlighted. Future directions focus on optimizing the design and expanding applications to overcome these limitations. The versatility and potential of aptamer@MOF biosensors underscore their promise as high-performance platforms for bacterial detection in diverse fields.

Ratiometric fluorescence sensor for Escherichia coli detection using fluorescein isothiocyanate-labeled metal-organic frameworks

A ratiometric fluorescence sensor for detecting Escherichia coli (E. coli) was fabricated based on the fluorescein isothiocyanate (FITC)-labeled zirconium (Zr)-tetraphenylporphyrin tetrasulfonic acid (TPPS) hydrate metal-organic frameworks (ZTMs@FITC). The ZTMs have strong red fluorescence emission at 683 nm, which can be quenched by Cu2+. E. coli can capture and convert external Cu2+ into Cu+ through its distinctive metabolic activities. To minimize environmental and instrumental influences and enhance detection precision, green FITC with an emission peak at 515 nm was utilized as the fluorescence labeling agent to fabricate the ratiometric fluorescence probe (ZTMs@FITC). The prepared ZTMs@FITC probe showed excellent performance in the detection of E. coli. As the concentration of E. coli increased, the fluorescence intensity at 683 nm (ZTMs, F683) increased considerably, while the fluorescence intensity at 515 nm (FITC, F515) decreased. By monitoring the increase in the ratio of F683 to F515, this sensor achieved rapid and sensitive detection of E. coli within the concentration range from 1.0 × 101 to 5.0 × 105 CFU/mL. The limit of detection was 6 CFU/mL. When observed under a 365 nm ultraviolet lamp, the fluorescence color of the solution changed from yellow to red. Additionally, the dual-signal ratiometric fluorescence method exhibited high selectivity for E. coli and was successfully utilized to detect E. coli in juice samples, demonstrating its practical application potential in food analysis.

Boronic acid-functionalized Fe3O4 nanoparticles for activity-preserved enrichment of low-abundance bacteria from real samples

Pathogenic bacterial infections represent a significant and ongoing threat to public health. The development of a sensitive, convenient, and accurate method for diagnosing pathogenic bacteria is a formidable challenge due to their low abundance in complex biological samples, especially in the early stages of diseases. In this study, a kind of phenylboronic acid-functionalized Fe3O4 nanoparticles (NPs), known as Fe3O4@poly(PEGDA-co-MAAPBA) NPs, was developed for effectively enriching low levels of pathogenic bacteria from complex samples and then diagnosing them through microbiological cultures. In this design, the resultant Fe3O4@poly(PEGDA-co-MAAPBA) NPs could recognize pathogenic bacteria because of the reversible reactions between the phenylboronic acid groups on the NPs and the cis-diol structures outside of the bacterial cells. By exploiting the magnetic properties of Fe3O4 NPs, bacteria were able to anchored onto the resulting NPs (NPs@bacteria) for easy enrichment. Utilizing microbiological culture techniques, successful cultivation of NPs@bacteria was achieved, demonstrating that bacterial activity remained unaffected during the enrichment process. The proposed method exhibited a limit of detection as low as 0.4 colony-forming units per milliliter. The Fe3O4@poly(PEGDA-co-MAAPBA) NPs were applied successfully for testing Staphylococcus aureus in urine samples which were typically considered to be free of bacterial contamination, indicating excellent selectivity and enrichment capability of the prepared NPs in complex samples. It suggests that the Fe3O4@poly(PEGDA-co-MAAPBA) NPs have the potential to become a powerful tool for early diagnosis of pathogenic bacteria in the clinic.

Specific gFET-Based Aptasensors for Monitoring of Microbiome Quality: Quantification of the Enteric Health-Relevant Bacterium Roseburia Intestinalis

Roseburia intestinalis, enriched in the gut, is closely associated with obesity, intestinal inflammation, and other diseases. A novel detection method for R. intestinalis to replace the commonly used 16S rRNA sequencing technique is aim to developed, thus enabling real-time and low-cost monitoring of gut microbiota. The optimal solution is to utilize rGO-FET (reduced graphene oxide field-effect transistor) functionalized with aptamers. Due to the high sensitivity of graphene sensors to electronic changes in the system, it is anticipated to achieve detection sensitivity that traditional fluorescence detection techniques cannot attain. The previous work reported a nucleic acid aptamer library, Ri 7_2, capable of quantitatively tracking R. intestinalis in complex systems. However, due to the complexity of the aptamer library itself, large-scale industrial synthesis is challenging, significantly limiting its further commercial application potential. Therefore, in this study, through Next-Generation Sequencing analysis, four representative single aptamers from the aptamer library is strategically selected, named A-Rose 1, A-Rose 2, A-Rose 3, and A-Rose 4, and confirmed their excellent performance similar to the aptamer library Ri 7_2. Furthermore, aptamer-modified rGO-FET demonstrated universality in detecting R. intestinalis in a series of biochemical analyses, providing a novel and powerful diagnostic tool for the clinical diagnosis of R. intestinalis.

A critical review on metal organic frameworks (MOFs)-based sensors for foodborne pathogenic bacteria detection

The pervasive threat of foodborne pathogenic bacteria necessitates advancements in rapid and reliable detection methods. Traditional approaches suffer from significant limitations including prolonged processing times, limited sensitivity and specificity. This review comprehensively examines the integration of metal organic frameworks (MOFs) with sensor technologies for the enhanced detection of foodborne pathogens. MOFs, with their unique properties such as high porosity, tunable pore sizes, and ease of functionalization, offer new avenues for sensor enhancement. This paper provides a comprehensive analysis of recent developments in MOFs-based sensors, particularly focusing on electrochemical, fluorescence, colorimetric, and surface-enhanced Raman spectroscopy sensors. We have provided a detailed introduction for the operational principles of these sensors, highlighting the role of MOFs play in enhancing their performance. Comparative analyses demonstrate MOFs' superior capabilities in enhancing signal response, reducing response time, and expanding detection limits. This review culminates in presenting MOFs as transformative materials in the detection of foodborne pathogens, paving the way for their broader application in ensuring food safety.

A press-actuated slidable microfluidic colorimetric biosensor for Salmonella detection utilizing nickel mesh sheet and MIL-88@Pd/Pt nanoparticles

A press-actuated slidable microfluidic colorimetric biosensor was designed for rapid, sensitive and multi-channel detection of Salmonella. The nickel mesh sheet (NMS) modified with capture antibodies was employed for capturing target bacteria, and metal organic frameworks decorated with palladium (Pd) and platinum (Pt) nanoparticles (MIL-88@Pd/Pt NPs) modified with detection antibodies were used for amplifying colorimetric signals. The capture efficiency of the immune NMS reached 83 %, and the detection limit of this colorimetric biosensor was 35 CFU/mL in 20 min. The average recoveries for Salmonella in spiked chicken meats ranged from 92.2 % to 102.5 % with a variation from 3.7 % to 7.2 %. The press-actuated slidable microfluidic chip was elaboratively developed with multiple functions, including mixing, separation, washing, catalysis and detection.

Highly sensitive and rapid detection of Vibrio parahaemolyticus using a dual-recognition platform based on functionalized quantum dots and aptamer

As one of the most harmful pathogenic bacteria in shrimp aquaculture, Vibrio parahaemolyticus often causes massive mortality in shrimp. Accurate and rapid detection of V. parahaemolyticus in shrimp farming is essential for avoiding huge economic losses caused by related diseases. In this study, we designed a dual-recognition platform for efficient identification and quantification of V. parahaemolyticus. First, the target bacterium was captured with magnetic beads functionalized by aptamers (Apt-MBs), and then, the broad-spectrum fluorescent probe FcMBL@CdSe-ZnS was used to detect the bacterium based on the interactions between fragment crystallizable mannose-binding lectin (FcMBL) and pathogenic bacteria. The proposed dual-recognition strategy centered around aptamers and FcMBL@CdSe-ZnS was applied to definite quantification of V. parahaemolyticus over a wide range of 10-108 CFU/mL with a limit of detection of 4 CFU/mL within 55 min. The feasibility was demonstrated by using the platform to detect V. parahaemolyticus from shrimp intestine, aquaculture water, and seawater.

Multifunctional SERS Substrate for Simultaneous Detection of Multiple Contaminants and Photothermal Removal of Pathogenic Bacteria

In this work, a boric-acid-modified Fe3O4@Au@BA-MOF composite material as a multifunctional SERS substrate was ingeniously constructed for detecting both pathogens and antibiotics as well as photothermally inactivating the pathogens. Through improving the dispersity and stability of gold nanoparticles (Au NPs), leveraging the specificity of boric acid (BA) groups in recognizing cis-diol structures, and the ability of SERS technology to provide unique fingerprint spectra of targets, the sensitive and stable detection of pathogens and antibiotics was achieved. Compared with Au NPs and Fe3O4@Au, the SERS enhancement factor of Fe3O4@Au@BA-MOF was 4.31 × 106, which was about 400 times and 16 times higher than the former two, respectively. Among the existing work, the limit of detection for pathogens was lower or comparable, and it exhibited good stability, maintaining consistent performance for 23 days. Additionally, this substrate achieved efficient photothermal inactivation of pathogens under both near-infrared light and natural light excitation. Within 8 min of near-infrared light irradiation, the bactericidal rates for Staphylococcus aureus and Escherichia coli reach 100% and 99.3%, respectively.

Emerging Biomimetic Sensor Technologies for the Detection of Pathogenic Bacteria: A Commercial Viability Study

Ensuring a rapid and accurate identification of harmful bacteria is crucial in various fields including environmental monitoring, food safety, and clinical diagnostics. Conventional detection methods often suffer from limitations such as long analysis time, complexity, and the need for qualified personnel. Therefore, a lot of research effort is devoted to developing technologies with the potential to revolutionize the detection of pathogenic bacteria by offering rapid, sensitive, and user-friendly platforms for point-of-care analysis. In this light, biosensors have gained significant commercial attention in recent years due to their simplicity, portability, and rapid analysis capabilities. The purpose of this review is to identify a trend by analyzing which biosensor technologies have become commercially successful in the field of bacteria detection. Moreover, we highlight the characteristics that a biosensor must possess to finally arrive in the market and therefore in the hands of the end-user, and we present critical examples of the market applications of various technologies. The aim is to investigate the reason why certain technologies have achieved commercial success and extrapolate these trends to the future economic viability of a new subfield in the world of biosensing: the development of biomimetic sensor platforms. Therefore, an overview of recent advances in the field of biomimetic bacteria detection will be presented, after which the challenges that need to be addressed in the coming years to improve market penetration will be critically evaluated. We will zoom into the current shortcomings of biomimetic sensors based on imprinting technology and aptamers and try to come up with a recommendation for further development based on the trends observed from previous commercial success stories in biosensing.

Argonaute-DNAzyme tandem biosensing for highly sensitive and simultaneous dual-gene detection of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA), a common zoonotic multidrug-resistant bacterium, puts a great threat to public health and food safety. Rapid and reliable detection of MRSA is crucial to guide effective patient treatment at early stages of infection and control the spread of MRSA infections. Herein, we developed a Simultaneous dual-gene and ulTra-sensitive detection for methicillin-resistant Staphylococcus aureus using Argonaute-DNAzyme tandem Detection (STAND). Simply, loop-mediated isothermal amplification (LAMP) was used for the amplification of the species-specific mecA and nuc gene, followed by STAND enabled by the site-specific cleavage of programable Argonaute. The Argonaute-DNAzyme tandem reaction rendered a conceptually novel signal amplification and transduction module that was more sensitive (1 or 2 order of magnitude higher) than the original Argonaute-based biosensing. With the strategy, the target nucleic acid signals gene were dexterously converted into fluorescent signals. STAND could detect the nuc gene and mecA gene simultaneously in a single reaction with 1 CFU/mL MRSA and a dynamic range from 1 to 108 CFU/mL. This method was confirmed by clinical samples and challenged by identifying contaminated foods and MRSA-infected animals. This work enriches the arsenal of Argonaute-mediated biosensing and presents a novel biosensing strategy to detect pathogenic bacteria with ultra-sensitivity, specificity and on-site capability.

Rapid detection of Saccharomyces cerevisiae with boronic acid-decorated multivariate metal-organic frameworks and aptamers

Liquor brewing is a classic solid-substrate fermentation process with a unique brewing microbiome. As one of the most common fungi, Saccharomyces cerevisiae ferments saccharides and has been extensively applied in brewing production. Here, we present the facile fabrication of a selective, sensitive, and integrated fluorescent biosensor for S. cerevisiae detection. The proposed biosensor used aptamer-modified magnetic beads to specifically capture S. cerevisiae, and the enriched fungi were recognized and detected with boronic acid-decorated multivariate metal-organic frameworks. The biosensor allows rapid quantification of S. cerevisiae in the range of 10-106 CFU mL-1, showing excellent specificity and repeatability, and maintaining stable biosensing performance in long-term storage. The analytical ability of the proposed biosensor was successfully verified in distilled yeast and fermented grain samples spiked with S. cerevisiae.