A fluorometric assay for rapid enrichment and determination of bacteria by using zirconium-metal organic frameworks as both capture surface and signal amplification tag

Advances in signal amplification strategies applied in pathogenic bacteria apta-sensing analysis-A review

Pathogenic bacteria are primarily kinds of food hazards that provoke serious harm to human health via contaminated or spoiled food. Given that pathogenic bacteria continue to reproduce and expand once they contaminate food, pathogenic bacteria of high concentration triggers more serious losses and detriments. Hence, it is essential to detect low-dose pollution at an early stage with high sensitivity. Aptamers, also known as "chemical antibodies", are oligonucleotide sequences that have attracted much attention owing to their merits of non-toxicity, small size, variable structure as well as easy modification of functional group. Aptamer-based bioanalysis has occupied a critical position in the field of rapid detection of pathogenic bacteria. This is attributed to the unique advantage of using aptamers as recognition elements in signal amplification strategies. The signal amplification strategy is an effective means to improve the detection sensitivity. Some diverse signal amplification strategies emphasize the synthesis and assembly of nanomaterials with signal amplification capabilities, while others introduce various nucleic acid amplification techniques into the detection system. This review focuses on a variety of signal amplification strategies employed in aptamer-based detection approaches to pathogenic bacteria. Meanwhile, we provided a detailed introduction to the design principles and characteristics of signal amplification strategies, as well as the improvement of sensor sensitivity. Ultimately, the existing issues and development trends of applying signal amplification strategies in apta-sensing analysis of pathogenic bacteria are critically proposed and prospected. Overall, this review discusses from a new perspective and is expected to contribute to the further development of this field.

Nano-Biotechnology for Bacteria Identification and Potent Anti-bacterial Properties: A Review of Current State of the Art

Sepsis is a critical disease caused by the abrupt increase of bacteria in human blood, which subsequently causes a cytokine storm. Early identification of bacteria is critical to treating a patient with proper antibiotics to avoid sepsis. However, conventional culture-based identification takes a long time. Polymerase chain reaction (PCR) is not so successful because of the complexity and similarity in the genome sequence of some bacterial species, making it difficult to design primers and thus less suitable for rapid bacterial identification. To address these issues, several new technologies have been developed. Recent advances in nanotechnology have shown great potential for fast and accurate bacterial identification. The most promising strategy in nanotechnology involves the use of nanoparticles, which has led to the advancement of highly specific and sensitive biosensors capable of detecting and identifying bacteria even at low concentrations in very little time. The primary drawback of conventional antibiotics is the potential for antimicrobial resistance, which can lead to the development of superbacteria, making them difficult to treat. The incorporation of diverse nanomaterials and designs of nanomaterials has been utilized to kill bacteria efficiently. Nanomaterials with distinct physicochemical properties, such as optical and magnetic properties, including plasmonic and magnetic nanoparticles, have been extensively studied for their potential to efficiently kill bacteria. In this review, we are emphasizing the recent advances in nano-biotechnologies for bacterial identification and anti-bacterial properties. The basic principles of new technologies, as well as their future challenges, have been discussed.

Aptamer-based DNA-catalyzed amplification strategy for sensitive fluorescence resonance energy transfer detection of Acinetobacter baumannii

Acinetobacter baumannii (A. baumannii) is a common pathogen that causes hospital-acquired infections and is resistant to a wide variety of antibiotics. Consequently, the rapid and highly sensitive detection of A. baumannii is required during the early stages of infection. Therefore, we developed a DNA-catalyzed amplification mechanism based on aptamers, combined with a novel fluorescence resonance energy transfer (FRET) method based on graphene oxide (GO), for the detection of A. baumannii. In the presence of A. baumannii, an aptamer bound to A. baumannii, releasing the template strand, which triggered an entropy-driven catalysis (EDC) reaction. One EDC product was then used as the catalyst for catalytic hairpin assembly (CHA) on a GO nanosheet. Finally, the GO released a huge amount of FAM-labeled DNA duplices, which could be detected with FRET. This strategy circumvented the extraction of nucleic acids and was easy to execute, with a detection time of ≤1.5 h. The detection of A. baumannii with this method ranges from 5 cfu/mL to 1 × 10⁵ cfu/mL, with a detection limit of 1.1 cfu/mL. The method was sufficiently sensitive and specific to detect A. baumannii rapidly in cerebrospinal fluid. In summary, our strategy provides a new option for the early detection and point-of-care testing (POCT) of A. baumannii infections, allowing their earlier and more precise treatment.

Metal-Organic Framework-DNA Bio-Barcodes Amplified CRISPR/Cas12a Assay for Ultrasensitive Detection of Protein Biomarkers

CRISPR/Cas12a shows excellent potential in disease diagnostics. However, insensitive signal conversion strategies hindered its application in detecting protein biomarkers. Here, we report a metal-organic framework (MOF)-based DNA bio-barcode integrated with the CRISPR/Cas12a system for ultrasensitive detection of protein biomarkers. In this work, zirconium-based MOF nanoparticles were comodified with antibodies and bio-barcode phosphorylated DNA as an efficient signal converter, which not only recognized the protein biomarker to form the sandwich complex but also released the bio-barcode DNA activators after MOF dissociation to activate the trans-cleavage activity of Cas12a. Due to the obvious advantages, including numerous loaded oligonucleotides, a convenient release process, and the nontoxic release reagent, this MOF-DNA bio-barcode strategy could amplify the CRISPR/Cas12a system to achieve simple and highly sensitive detection of tumor protein biomarkers with detection limits of 0.03 pg/mL (PSA) and 0.1 pg/mL (CEA), respectively. Furthermore, this platform could detect PSA directly in clinical serum samples, offering a powerful tool for early disease diagnosis.

Xeno nucleic acid probes mediated methylation-specific PCR for single-base resolution analysis of N6-methyladenosine in RNAs

Reliable and cost-effective quantification of RNA modifications at a specific gene locus is essential to elucidate the pathogenic mechanism encoded by RNA epigenetics. Current methods to quantify N⁶-methyladenosine (m6A) at specific sites can hardly satisfy the requirement of clinical application because epigenetic information is easily lost through polymerase chain reaction (PCR) assay or other isothermal amplification methods unless tedious pretreatment is applied. Herein, we propose a simple xeno nucleic acid (XNA) as a blocker probe to mediate the methylation specific reverse transcription quantitative polymerase chain reaction (MsRT-qPCR) assay to directly magnify the minor differences between epigenetic bases and unmodified bases in RNA. Strand displacement reactions selectively initiated between the reverse transcription primer (RT-primer) and the XNA probe at the m6A template given the affinity differences between the blocker probes and the m6A-modified RNA (m6A-RNA) and unmodified RNA (A-RNA). Thus, preferential amplification of m6A-RNA was allowed. Integration of a well-established oligo-modified Fe₃O₄@UiO-66-NH₄ allowed purification of mRNA and lncRNA from cellular total RNA samples and greatly reduced the non-specific interference of m6A detection in real samples. Multiple specific sites of m6A in mRNA and lncRNA samples are also successfully quantified. The XNA probe-based m6A assay required only common and available lab equipment and materials, which can be applied in m6A-related fundamental studies and clinical diagnosis.

Metal-organic frameworks for diagnosis and therapy of infectious diseases

Infectious diseases are one of the leading cause of mortality and morbidity worldwide. Metal-Organic Frameworks (MOFs), which are porous coordination materials composed of bridging organic ligands and metallic ions or clusters, exhibits great potential to be used against several pathogens, such as bacteria, viruses, fungi and protozoa. MOFs can show sustained release capability, high surface area, adjustable pore size and structural flexibility, which makes them good candidates for new therapeutic systems. This review provides a detailed summary of the biological application of MOFs, focussing on diagnosis and treatment of infectious diseases. MOFs have been reported for usage as antimicrobial agents, drug delivery systems, therapeutic composites, nanozymes and phototherapies. Furthermore, different MOF-based biosensors have also been developed to detect specific pathogens by electrochemical, fluorometric and colorimetric assays. Finally, we present limitations and perspectives in this field.

Recent Advances and a Roadmap to Aptamer-Based Sensors for Bloodstream Infections

The present review is intended to describe bloodstream infections (BSIs), the major pathogens responsible for BSIs, conventional tests and their limitations, commercially available methods used, and the aptamer and nanomaterials-based approaches developed so far for the detection of BSIs. The advantages associated with aptamers and the aptamer-based sensors, the comparison between the aptamers and the antibodies, and the various types of aptasensors developed so far for the detection of bloodstream infections have been described in detail in the present review. Also, the future outlook and roadmap toward aptamer-based sensors and the challenges associated with the aptamer development have also been concluded in this review.

Aptamers and Aptamer-Coupled Biosensors to Detect Water-Borne Pathogens

Aptamers can serve as efficient bioreceptors for the development of biosensing detection platforms. Aptamers are short DNA or RNA oligonucleotides that fold into specific structures, which enable them to selectively bind to target analytes. The method used to identify aptamers is Systematic Evolution of Ligands through Exponential Enrichment (SELEX). Target properties can have an impact on aptamer efficiencies. Therefore, characteristics of water-borne microbial targets must be carefully considered during SELEX for optimal aptamer development. Several aptamers have been described for key water-borne pathogens. Here, we provide an exhaustive overview of these aptamers and discuss important microbial aspects to consider when developing such aptamers.

Recent Progress in the Identification of Aptamers Against Bacterial Origins and Their Diagnostic Applications

Aptamers have gained an increasing role as the molecular recognition element (MRE) in diagnostic assay development, since their first conception thirty years ago. The process to screen for nucleic acid-based binding elements (aptamers) was first described in 1990 by the Gold Laboratory. In the last three decades, many aptamers have been identified for a wide array of targets. In particular, the number of reports on investigating single-stranded DNA (ssDNA) aptamer applications in biosensing and diagnostic platforms have increased significantly in recent years. This review article summarizes the recent (2015 to 2020) progress of ssDNA aptamer research on bacteria, proteins, and lipids of bacterial origins that have implications for human infections. The basic process of aptamer selection, the principles of aptamer-based biosensors, and future perspectives will also be discussed.