Microfluidics and nanoparticles based amperometric biosensor for the detection of cyanobacteria (Planktothrix agardhii NIVA-CYA 116) DNA

A rapid field-ready electrical biosensor consisting of bismuthine-derived Au island decorated BiOCl nanosheets for Raphidiopsis raciborskii detection in freshwater

Cyanobacteria play an essential role in nutrient cycling in aquatic ecosystems. However, certain species adversely affect the environment and human health by causing harmful cyanobacterial algal blooms (cyanoHABs) and producing cyanotoxins. To address this issue, continuous cyanoHAB monitoring has been considered; however, a gold standard has not yet been established. In this study, we aimed to develop a dual DNA-targeting capacitive-type biosensor for rapid field-ready monitoring of Raphidiopsis raciborskii, a causative species of cyanoHAB. To enhance the sensing signal, a plate-like Au-BiOCl nanocomposite was synthesized using a spontaneous carbonation process without additional additives. The alternating-current electrothermal flow (ACEF) technique was applied to enable rapid DNA and probe binding within 10 min. The limits of detection (LODs) for R. raciborskii RubisCO large subunit (rbcL) and RNA polymerase beta subunit (rpoB) genes diluted in deionized (DI) water were 4.89 × 10-17 and 3.89 × 10-17 M, respectively. Furthermore, the LODs of R. raciborskii rbcl and rpoB diluted in freshwater containing HAB were 2.55 × 10-16 and 3.84 × 10-16 M, respectively, demonstrating the field-ready applicability of the device. The fabricated cyanobacterial DNA-sensing platform enabled powerful species-specific detection using a small sample volume and low target concentration without a nucleic acid amplification step, dramatically reducing the detection time. This study has considerable implications for detecting HABs, early warning systems, and species-specific environmental monitoring technology.

Pre-enrichment-free detection of hepatocellular carcinoma-specific ctDNA via PDMS and MEMS-based microfluidic sensor

The growing interest in microfluidic biosensors has led to improvements in the analytical performance of various sensing mechanisms. Although various sensors can be integrated with microfluidics, electrochemical ones have been most commonly employed due to their ease of miniaturization, integration ability, and low cost, making them an established point-of-care diagnostic method. This concept can be easily adapted to the detection of biomarkers specific to certain cancer types. Pathological profiling of hepatocellular carcinoma (HCC) is heterogeneous and rather complex, and biopsy samples contain limited information regarding the tumor and do not reflect its heterogeneity. Circulating tumor DNAs (ctDNAs), which can contain information regarding cancer characteristics, have been studied tremendously since liquid biopsy emerged as a new diagnostic method. Recent improvements in the accuracy and sensitivity of ctDNA determination also paved the way for genotyping of somatic genomic alterations. In this study, three-electrode (Au-Pt-Ag) glass chips were fabricated and combined with polydimethylsiloxane (PDMS) microchannels to establish an electrochemical microfluidic sensor for detecting c.747G > T hotspot mutations in the TP53 gene of ctDNAs from HCC. The preparation and analysis times of the constructed sensor were as short as 2 h in total, and a relatively high flow rate of 30 µl/min was used during immobilization and hybridization steps. To the best of our knowledge, this is the first time a PDMS-based microfluidic electrochemical sensor has been developed to target HCC ctDNAs. The system exhibited a limit of detection (LOD) of 24.1 fM within the tested range of 2-200 fM. The sensor demonstrated high specificity in tests conducted with fully noncomplementary and one-base mismatched target sequences. The developed platform is promising for detecting HCC-specific ctDNA at very low concentrations without requiring pre-enrichment steps.

Rapid method for detection of Vibrio cholerae from drinking water with nanomaterials enhancing electrochemical biosensor

Cholera is a potentially fatal diarrheal disease caused by Vibrio cholerae and is spread to humans from contaminated food and water. In order to prevent spread of epidemic chlorea, the development of novel sensitive, selective, user-friendly, cost-effective and rapid detection systems to detect of V. cholerae are necessary. Therefore, in this study, it was aimed to develop a specific, electrochemical immunoassay with high selectivitiy and sensitivity for detection of V. cholerae from drinking water using in house synthesized Gold Nanoparticles (AuNPs). The synthesized AuNPs were characterized by UV/Vis spectroscopy, Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM) and electrochemical techniques were applied to confirm the succesful fabrication of the immunosensor. Also, this study focuses on the development of an antibody sensor for V. cholerae detection using a standard immunoassay without using nanoparticle. To accomplish that, in house spherical synthesized AuNPs at various sizes were synthesized, conjugated with secondary antibody-horseradish peroxidase enzyme (HRP) complex and their possible effect on the lowest detection limit of V. cholerae was investigated in comparison to commercially available AuNPs. The AuNPs-immunosensor on the results enabled the quantification of V. cholerae in a wide concentration range with a high sensitivity limit of detection (1 Colony-Forming Units/Milliliter) and specificity. Although the effect of 33 and 54 nm AuNPs on the process is close to each other, it has been observed that there is a 34% loss of efficiency when the size of the nanoparticle increases. With this study, a novel V. cholerae specific immunosensor was developed and the effects of in house synthesized AuNPs with various diameter on this developed biosensor were investigated in detail.

Cyanobacterial Algal Bloom Monitoring: Molecular Methods and Technologies for Freshwater Ecosystems

Cyanobacteria (blue-green algae) can accumulate to form harmful algal blooms (HABs) on the surface of freshwater ecosystems under eutrophic conditions. Extensive HAB events can threaten local wildlife, public health, and the utilization of recreational waters. For the detection/quantification of cyanobacteria and cyanotoxins, both the United States Environmental Protection Agency (USEPA) and Health Canada increasingly indicate that molecular methods can be useful. However, each molecular detection method has specific advantages and limitations for monitoring HABs in recreational water ecosystems. Rapidly developing modern technologies, including satellite imaging, biosensors, and machine learning/artificial intelligence, can be integrated with standard/conventional methods to overcome the limitations associated with traditional cyanobacterial detection methodology. We examine advances in cyanobacterial cell lysis methodology and conventional/modern molecular detection methods, including imaging techniques, polymerase chain reaction (PCR)/DNA sequencing, enzyme-linked immunosorbent assays (ELISA), mass spectrometry, remote sensing, and machine learning/AI-based prediction models. This review focuses specifically on methodologies likely to be employed for recreational water ecosystems, especially in the Great Lakes region of North America.

Rapid electrochemical biosensor composed of DNA probe/iridium nanoparticle bilayer for Aphanizomenon flos-aquae detection in fresh water

Toxic cyanobacteria pose a serious threat to aquatic ecosystems and require adequate detection and control systems. Aphanizomenon flos-aquae is a harmful cyanobacterium that produces the toxicant saxitoxin. Therefore, it is necessary to detect the presence of A. flos-aquae in lakes and rivers. We proposed a rapid electrochemical biosensor composed of DNA primer/iridium nanoparticles (IrNP) bilyer for the detection of A. flos-aquae in freshwater. The extracted A. flos-aquae gene (rbcL-rbcX) is used as a target, and it was fixed to the electrode using a 5'-thiolated DNA primer (capture probe). Then, Avidin@IrNPs complex for amplification of electrical signals was bound to the target through a 3'-biotinylated DNA primer (detection probe). To rapidly detect the target, an alternating current electrothermal flow technique was introduced in the detection step, which could reduce the detection time to within 20 min. To confirm the biosensor fabrication, atomic force microscopy was used to investigate the surface morphology. To evaluate the biosensor performance, cyclic voltammetry and electrochemical impedance spectroscopy were used. The target gene was detected at a concentration of 9.99 pg/mL in tap water, and the detection range was 0.1 ng/mL to 10³ ng/mL with high selectivity. Based on the combined system, we employed A. flos-aquae in tap water. This rapid cyanobacteria detection system is a powerful tool for CyanoHABs in the field.

Microchip coupled with MALDI-TOF MS for the investigation of bacterial contamination of fish muscle products

Bacterial contamination is a significant concern in food safety. Traditional methods, though being a gold standard for bacterial detection, are time-consuming. In this work, we managed to establish a simple and versatile magnetic-assisted microfluidic method for rapid bacterial detection of fish muscle products, by manipulating anti-human IgG functionalized magnetic beads in a zig-zag shaped microfluidic channel, increasing the probability for bacteria capture. The captured bacteria were characterized by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). This method is capable of isolating Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae from 5 μL of sablefish sarcoplasmic protein sample, and detecting Escherichia coli in the range of 6.0 to 6.0×10⁴ CFU/mL with a detection limit of 6 CFU/mL. Bacterial growth on salmon sashimi during its period of storage was successfully monitored. The current protocol holds great potential for pathogen detection and microbial control in the food industry.

Applications of biosensors for bacteria and virus detection in food and water-A systematic review

Biosensors for sensitive and specific detection of foodborne and waterborne pathogens are particularly valued for their portability, usability, relatively low cost, and real-time or near real-time response. Their application is widespread in several domains, including environmental monitoring. The main limitation of currently developed biosensors is a lack of sensitivity and specificity in complex matrices. Due to increased interest in biosensor development, we conducted a systematic review, complying with the PRISMA guidelines, covering the period from January 2010 to December 2019. The review is focused on biosensor applications in the identification of foodborne and waterborne microorganisms based on research articles identified in the Pubmed, ScienceDirect, and Scopus search engines. Efforts are still in progress to overcome detection limitations and to provide a rapid detection system which will safeguard water and food quality. The use of biosensors is an essential tool with applicability in the evaluation and monitoring of the environment and food, with great impact in public health.

Pivotal role of electrospun nanofibers in microfluidic diagnostic systems - a review

Recently, the usage of electrospinning technology for the fabrication of fine fibers with a good deal of variation in morphology and structure has drawn the attention of many researchers around the world. These fibers have found their way in the many fields of science including medical diagnosis, tissue engineering, drug delivery, replica molding, solar cells, catalysts, energy conversion and storage, physical and chemical sensors and other applications. Among all applications, biosensing with the aim of rapid and sensitive biomarker detection is an area that warrants attention. Electrospun nanofibrous membranes enjoy numerous factors which benefit them to be used as potential candidates in biosensing platforms. Some of these factors include a high surface to volume ratio, analogous scale compared to bioactive molecules and relatively defect-free properties of nanofibers (NFs). In this review, we focused on the recent advances in electrospun nanofibrous membrane-based micro-analytical devices with an application as diagnostic systems. Hence, a study on the electrospun nanofiber usage in lab-on-a-chip and paper-based point-of-care devices, with an opening introduction to biosensors, nanofibers, the electrospinning method, and microfluidics as the principles of the intended subject, is provided. It is anticipated that the given examples in this paper will provide sufficient evidence for the potential of electrospun NFs for being used as a substrate in the commercial fabrication of highly sensitive and selective biosensors.

Automated DNA hybridization transfer with movable super-paramagnetic microbeads in a microflow reactor

An automated DNA hybridization transfer in a microflow reactor is demonstrated by moving paramagnetic beads between two spatially separate solutions with different pH values. The microbeads-based microfluidic platform is fully automated and programmable. It employs a robust chemical procedure for specific DNA hybridization transfer in microfluidic devices under isothermal conditions based on reversible pH alterations. The method takes advantage of high-speed DNA hybridization and denaturation on beads under flow conditions, high fidelity of DNA hybridization, and small sample volumes. The microfluidic platform presented is saleable and applicable to many areas of modern biotechnology such as DNA hybridization chip microarrays, molecular computation, on-chip selection of functional nucleic acids, high-throughput screening of chemical libraries for drug discovery, and DNA amplification and sequencing.

Advances in Chemical and Biological Methods to Identify Microorganisms-From Past to Present

Fast detection and identification of microorganisms is a challenging and significant feature from industry to medicine. Standard approaches are known to be very time-consuming and labor-intensive (e.g., culture media and biochemical tests). Conversely, screening techniques demand a quick and low-cost grouping of bacterial/fungal isolates and current analysis call for broad reports of microorganisms, involving the application of molecular techniques (e.g., 16S ribosomal RNA gene sequencing based on polymerase chain reaction). The goal of this review is to present the past and the present methods of detection and identification of microorganisms, and to discuss their advantages and their limitations.

Poly(azomethine-urethane) and zeolite-based composite: Fluorescent biosensor for DNA detection

In the present paper, a highly selective and sensitive fluorescent biosensor based on poly(azomethine-urethane) and zeolite for the determination of DNA molecules was developed. Zeolite was chosen to enhance with anionic or cationic functional groups in polymer matrix and interaction between polymer and DNA. Several parameters such as polymer concentration, pH and incubation time effect on the sensitivity of the fluorescent biosensor were optimized. Linear range was determined between 2.50 and 25.00 nmol/L DNA concentration and limit of detection (LOD) of the biosensor was calculated as 0.095 nmol/L under the optimal conditions. Interference study was also performed in the presence of different amino acids, cations and organic compounds. The results clearly indicated that the tested cations and compounds were not induced a significant fluorescence change and the proposed zeolite-based biosensor was shown a good selectivity for DNA.

Detection of Pathogenic Microorganisms by Microfluidics Based Analytical Methods

Microfluidics based biochemical analysis shows distinctive advantages for fast detection of pathogenic microorganisms. This Feature summarizes the progress in the past decade on microfluidic methods for purification and detection of pathogenic bacteria and viruses as well as their applications in food safety control, environmental monitoring, and clinical diagnosis.

Enabling miniaturised personalised diagnostics: from lab-on-a-chip to lab-in-a-drop

The concept of personalised diagnostics is to direct accurate clinical decisions based on an individual's unique disease molecular profile. Lab-on-a-chip (LOC) systems are prime personalised diagnostics examples which seek to perform an entire sample-to-outcome detection of disease nucleic acid (NA) biomarkers on a single miniaturised platform with minimal user handling. Despite the great potential of LOC devices in providing rapid, portable, and inexpensive personalised diagnosis at the point-of-care (POC), the translation of this technology into widespread use has still been hampered by the need for sophisticated and complex engineering. As an alternative miniaturised diagnostics platform free of precision fabrication, there have been recent developments towards a solution-based lab-in-a-drop (LID) system by which an entire laboratory-based diagnostics workflow could be downscaled and integrated within a singular fluid droplet for POC detection of NA biomarkers. In contrast to existing excellent reviews on miniaturised LOC fabrication and individual steps of NA biomarker sensing, we herein focus on miniaturised solution-based NA biosensing strategies suited for integrated LID personalised diagnostics development. In this review, we first evaluate the three fundamental bioassay steps for miniaturised NA biomarker detection: crude sample preparation, isothermal target amplification, and detection readout of amplicons. Then, we provide insights into research advancements towards a functional LID system which integrates all three of the above-mentioned fundamental steps. Finally, we discuss perspectives and future directions of LID diagnostic platforms in personalised medicine applications.

Gold Nanoparticles for Diagnostics: Advances towards Points of Care

The remarkable physicochemical properties of gold nanoparticles (AuNPs) have prompted developments in the exploration of biomolecular interactions with AuNP-containing systems, in particular for biomedical applications in diagnostics. These systems show great promise in improving sensitivity, ease of operation and portability. Despite this endeavor, most platforms have yet to reach maturity and make their way into clinics or points of care (POC). Here, we present an overview of emerging and available molecular diagnostics using AuNPs for biomedical sensing that are currently being translated to the clinical setting.

First paraben substituted cyclotetraphosphazene compounds and DNA interaction analysis with a new automated biosensor

Cancer, as one of the leading causes of death in the world, is caused by malignant cell division and growth that depends on rapid DNA replication. To develop anti-cancer drugs this feature of cancer could be exploited by utilizing DNA-damaging molecules. To achieve this, the paraben substituted cyclotetraphosphazene compounds have been synthesized for the first time and their effect on DNA (genotoxicity) has been investigated. The conventional genotoxicity testing methods are laborious, take time and are expensive. Biosensor based assays provide an alternative to investigate this drug/compound DNA interactions. Here for the first time, a new, easy and rapid screening method has been used to investigate the DNA damage, which is based on an automated biosensor device that relies on the real-time electrochemical profiling (REP™) technology. Using both the biosensor based screening method and the in vitro biological assay, the compounds 9 and 11 (propyl and benzyl substituted cyclotetraphosphazene compounds, respectively), have resulted in higher DNA damage than the others with 65% and 80% activity reduction, respectively.

Improving detection sensitivity by oriented bioconjugation of antibodies to quantum dots with a flexible spacer arm for immunoassay

The impacts of conjugation method and spacer arm for antibody covalent coupling with quantum dots on their biodetection performance are experimentally disclosed.