Lab-on-a-Chip Technology for Environmental Monitoring of Microorganisms

The Biomedical Applications of Biomolecule Integrated Biosensors for Cell Monitoring

Cell monitoring is essential for understanding the physiological conditions and cell abnormalities induced by various stimuli, such as stress factors, microbial invasion, and diseases. Currently, various techniques for detecting cell abnormalities and metabolites originating from specific cells are employed to obtain information on cells in terms of human health. Although the states of cells have traditionally been accessed using instrument-based analysis, this has been replaced by various sensor systems equipped with new materials and technologies. Various sensor systems have been developed for monitoring cells by recognizing biological markers such as proteins on cell surfaces, components on plasma membranes, secreted metabolites, and DNA sequences. Sensor systems are classified into subclasses, such as chemical sensors and biosensors, based on the components used to recognize the targets. In this review, we aim to outline the fundamental principles of sensor systems used for monitoring cells, encompassing both biosensors and chemical sensors. Specifically, we focus on biosensing systems in terms of the types of sensing and signal-transducing elements and introduce recent advancements and applications of biosensors. Finally, we address the present challenges in biosensor systems and the prospects that should be considered to enhance biosensor performance. Although this review covers the application of biosensors for monitoring cells, we believe that it can provide valuable insights for researchers and general readers interested in the advancements of biosensing and its further applications in biomedical fields.

Current and emerging nanotechnology for sustainable development of agriculture: Implementation design strategy and application

Recently, agriculture systems have faced numerous challenges involving sustainable nutrient use efficiency and feeding, environmental pollution especially heavy metals (HMs), infection of harmful microorganisms, and maintenance of crop production quality during postharvesting and packaging. Nanotechnology and nanomaterials have emerged as powerful tools in agriculture applications that provide alternatives or support traditional methods. This review aims to address and highlight the current overarching issue and various implementation strategies of nanotechnology for sustainable agriculture development. In particular, the current progress of different nano-fertilizers (NFs) systems was analyzed to show their advances in enhancing the uptake and translocations in plants and improving nutrient bioavailability in soil. Also, the design strategy and application of nanotechnology for rapid detection of HMs and pathogenic diseases in plant crops were emphasized. The engineered nanomaterials have great potential for biosensors with high sensitivity and selectivity, high signal throughput, and reproducibility through various detection approaches such as Raman, colorimetric, biological, chemical, and electrical sensors. We obtain that the development of microfluidic and lab-on-a-chip (LoC) technologies offers the opportunity to create on-site portable and smart biodevices and chips for real-time monitoring of plant diseases. The last part of this work is a brief introduction to trends in nanotechnology for harvesting and packaging to provide insights into the overall applications of nanotechnology for crop production quality. This review provides the current advent of nanotechnology in agriculture, which is essential for further studies examining novel applications for sustainable agriculture.

Seamless integration of Internet of Things, miniaturization, and environmental chemical surveillance

IoT is a game-changer across all fields, including chemistry. Embracing sustainable practices and green chemistry, the miniaturization and automation of systems, and their integration into IoT is key to achieving these principles, as a rising trend with momentum. Particularly, IoT and analytical chemistry are linked in the rapid exchange of analytical data for environmental, industrial, healthcare, and educational applications. Meanwhile, cooperation with other fields of science is evident, and there is a prompt and subjective analysis of information related to analytical systems and methodologies. This paper will review the concepts, requirements, and architecture of IoT and its role in the miniaturization and automation of analytical tools using electronic modules and sensors. The aim is to explore the standards and perspectives of IoT and its interaction with different aspects of analytical chemistry. Additionally, it aimed to explain the basics and applications of IoT for chemists, and its relevance to different subfields of analytical chemistry, particularly in the field of environmental chemical surveillance. The article also covers updating IoT devices and creating DIY-based degradation devices to enhance the educational aspect of chemistry and reduce barriers to lab facilities and equipment. Lastly, it will explore how IoT is really important and how it's going to significantly impact analytical chemistry.

Microfluidics in environmental analysis: advancements, challenges, and future prospects for rapid and efficient monitoring

Microfluidic devices have emerged as advantageous tools for detecting environmental contaminants due to their portability, ease of use, cost-effectiveness, and rapid response capabilities. These devices have wide-ranging applications in environmental monitoring of air, water, and soil matrices, and have also been applied to agricultural monitoring. Although several previous reviews have explored microfluidic devices' utility, this paper presents an up-to-date account of the latest advancements in this field for environmental monitoring, looking back at the past five years. In this review, we discuss devices for prominent contaminants such as heavy metals, pesticides, nutrients, microorganisms, per- and polyfluoroalkyl substances (PFAS), etc. We cover numerous detection methods (electrochemical, colorimetric, fluorescent, etc.) and critically assess the current state of microfluidic devices for environmental monitoring, highlighting both their successes and limitations. Moreover, we propose potential strategies to mitigate these limitations and offer valuable insights into future research and development directions.

Innovative, Flexible, and Miniaturized Microfluidic Paper-Based Plasmonic Chip for Efficient Near-Infrared Metal Enhanced Fluorescence Biosensing and Imaging

The implementation of metal enhanced fluorescence (MEF) as an efficient detection tool, especially in the near-infrared region of the electromagnetic spectrum, is a rather new direction for diagnostic analytical technologies. In this context, we propose a novel microfluidic plasmonic design based on paper for efficient MEF detection of the "proof-of-concept" biotin-streptavidin recognition interaction. Our design made use of the benefits of gold nanobipyramids (AuBPs), considering the strong enhanced electromagnetic field present at their sharp tips, and filter paper to operate as a natural microfluidic channel due to excellent wicking abilities. The calligraphed plasmonic paper, obtained using a commercial pen filled with AuBPs, was integrated in a robust sandwich optically transparent polydimethylsiloxane chip, exhibiting portability and flexibility while preserving the chip's properties. To place the Alexa 680 fluorophore at an optimal distance from the nanobipyramid substrate, the human IgG-anti-IgG-conjugated biotin sandwich reaction was employed. Thus, upon the capture of Alexa 680-conjugated streptavidin by the biotinylated system, a 1.3-fold average enhancement of the fluorophore's emission was determined by bulk fluorescence measurements. However, the local enhancement factor was considerably higher with values spanning from 5 to 6.3, as proven by mapping the fluorescence emission under both re-scan microscopy and fluorescence lifetime imaging, endorsing the proposed chip's feasibility for bulk MEF biosensing as well as high-resolution MEF bioimaging. Finally, the versatility of our chip was demonstrated by adapting the biosensing protocol for cardiac troponin I biomarker detection, validated using 10 plasma samples collected from pediatric patients and corroborated with a conventional ELISA assay.

Innovative Real-Time Flow Sensor Using Detergent-Free Complex Emulsions with Dual-Emissive Semi-Perfluoroalkyl Substituted Α-Cyanostilbene

In this study, the potential of complex emulsions is investigated as transducers in sensing applications. Complex emulsions are stabilized without external detergents by developing a novel α-cyanostilbene substituted with PEG and semi-perfluoroalkyl chain (CNFCPEG). CNFCPEG exhibits unique variable emission properties depending on its aggregation state, allowing dual blue and green emissions in complex emulsions with hydrocarbon-in-fluorocarbon-in-water (H/F/W) morphology. The green excimer emissions result from the self-assembly of CNFCPEG at the fluorocarbon/water interface, while the blue emission observed is due to aggregation in the organic phase. A novel flow-injection method is developed by incorporating complex emulsions with CNFCPEG into multiple-well flow chips (MWFC). Iodine is successfully detected in a mobile aqueous solution by monitoring morphology changes. The findings demonstrate that self-stabilized complex emulsions with MWFC hold great promise for real-time sensing without costly instruments.

Recent Advances in Biosensor Development for the Detection of Viral Particles in Foods: A Comprehensive Review

Viral foodborne diseases cause serious harm to human health and the economy. Rapid, accurate, and convenient approaches for detecting foodborne viruses are crucial for preventing diseases. Biosensors integrating electrochemical and optical properties of nanomaterials have emerged as effective tools for the detection of viruses in foods. However, they still face several challenges, including substantial sample preparation and relatively poor sensitivity due to complex food matrices, which limit their field applications. Hence, the purpose of this review is to provide an overview of recent advances in biosensing techniques, including electrochemical, SERS-based, and colorimetric biosensors, for detecting viral particles in food samples, with emerging techniques for extraction/concentration of virus particles from food samples. Moreover, the principle, design, and advantages/disadvantages of each biosensing method are comprehensively described. This review covers the recent development of rapid and sensitive biosensors that can be used as new standards for monitoring food safety and food quality in the food industry.

Artificial intelligence-driven electrochemical immunosensing biochips in multi-component detection

Electrochemical Immunosensing (EI) combines electrochemical analysis and immunology principles and is characterized by its simplicity, rapid detection, high sensitivity, and specificity. EI has become an important approach in various fields, such as clinical diagnosis, disease prevention and treatment, environmental monitoring, and food safety. However, EI multi-component detection still faces two major bottlenecks: first, the lack of cost-effective and portable detection platforms; second, the difficulty in eliminating batch differences and accurately decoupling signals from multiple analytes. With the gradual maturation of biochip technology, high-throughput analysis and portable detection utilizing the advantages of miniaturized chips, high sensitivity, and low cost have become possible. Meanwhile, Artificial Intelligence (AI) enables accurate decoupling of signals and enhances the sensitivity and specificity of multi-component detection. We believe that by evaluating and analyzing the characteristics, benefits, and linkages of EI, biochip, and AI technologies, we may considerably accelerate the development of EI multi-component detection. Therefore, we propose three specific prospects: first, AI can enhance and optimize the performance of the EI biochips, addressing the issue of multi-component detection for portable platforms. Second, the AI-enhanced EI biochips can be widely applied in home care, medical healthcare, and other areas. Third, the cross-fusion and innovation of EI, biochip, and AI technologies will effectively solve key bottlenecks in biochip detection, promoting interdisciplinary development. However, challenges may arise from AI algorithms that are difficult to explain and limited data access. Nevertheless, we believe that with technological advances and further research, there will be more methods and technologies to overcome these challenges.

Multiplexed and continuous microfluidic sensors using dynamic complex droplets

Emissive complex droplets with reconfigurable morphology and dynamic optical properties offer exciting opportunities as chemical sensors due to their stimuli-responsive characteristics. In this work, we demonstrated a real-time optical sensing platform that combines poly(dimethylsiloxane) (PDMS) microfluidics and complex droplets as sensing materials. We utilized a mechanism, called directional emission, to transduce changes in interfacial tension into optical signals. We discuss the fabrication and integration of PDMS microfluidics with complex emulsions to facilitate continuous measurement of fluorescent emission and, ultimately, the interfacial tensions. Furthermore, by varying the interfacial functionalization and fluorescent dye with characteristic wavelength, we generate multiple formulations of droplets and obtain differential responses to stimuli that alter interfacial tensions (i.e., composition of surfactants, pH). Our results illustrate a proof-of-concept multiplexed and continuous sensing platform with potential applications in miniaturized, on-site environmental monitoring and biosensing.

3D-Printed Microfluidic Chip for Real-Time Glucose Monitoring in Liquid Analytes

The connection of macrosystems with microsystems for in-line measurements is important in different biotechnological processes as it enables precise and accurate monitoring of process parameters at a small scale, which can provide valuable insights into the process, and ultimately lead to improved process control and optimization. Additionally, it allows continuous monitoring without the need for manual sampling and analysis, leading to more efficient and cost-effective production. In this paper, a 3D printed microfluidic (MF) chip for glucose (Glc) sensing in a liquid analyte is proposed. The chip made in Poly(methyl methacrylate) (PMMA) contains integrated serpentine-based micromixers realized via stereolithography with a slot for USB-like integration of commercial DropSens electrodes. After adjusting the sample's pH in the first micromixer, small volumes of the sample and enzyme are mixed in the second micromixer and lead to a sensing chamber where the Glc concentration is measured via chronoamperometry. The sensing potential was examined for Glc concentrations in acetate buffer in the range of 0.1-100 mg/mL and afterward tested for Glc sensing in a cell culturing medium. The proposed chip showed great potential for connection with macrosystems, such as bioreactors, for direct in-line monitoring of a quality parameter in a liquid sample.

Towards the fully automated monitoring of ecological communities

High-resolution monitoring is fundamental to understand ecosystems dynamics in an era of global change and biodiversity declines. While real-time and automated monitoring of abiotic components has been possible for some time, monitoring biotic components-for example, individual behaviours and traits, and species abundance and distribution-is far more challenging. Recent technological advancements offer potential solutions to achieve this through: (i) increasingly affordable high-throughput recording hardware, which can collect rich multidimensional data, and (ii) increasingly accessible artificial intelligence approaches, which can extract ecological knowledge from large datasets. However, automating the monitoring of facets of ecological communities via such technologies has primarily been achieved at low spatiotemporal resolutions within limited steps of the monitoring workflow. Here, we review existing technologies for data recording and processing that enable automated monitoring of ecological communities. We then present novel frameworks that combine such technologies, forming fully automated pipelines to detect, track, classify and count multiple species, and record behavioural and morphological traits, at resolutions which have previously been impossible to achieve. Based on these rapidly developing technologies, we illustrate a solution to one of the greatest challenges in ecology: the ability to rapidly generate high-resolution, multidimensional and standardised data across complex ecologies.

Thin-Film-Based Multifunctional System for Optical Detection and Thermal Treatment of Biological Samples

In this work, we present a multifunctional Lab-on-Chip (LoC) platform based on hydrogenated amorphous silicon sensors suitable for a wide range of application in the fields of biochemical and food quality control analysis. The proposed system includes a LoC fabricated on a 5 cm × 5 cm glass substrate and a set of electronic boards for controlling the LoC functionalities. The presented Lab-on-Chip comprises light and temperature sensors, a thin film resistor acting as a heating source, and an optional thin film interferential filter suitable for fluorescence analysis. The developed electronics allows to control the thin film heater, a light source for fluorescence and absorption measurements, and the photosensors to acquire luminescent signals. All these modules are enclosed in a black metal box ensuring the portability of the whole platform. System performances have been evaluated in terms of sensor optical performances and thermal control achievements. For optical sensors, we have found a minimum number of detectable photons of 8 × 10⁴ s^-1·cm^-2 at room temperature, 1.6 × 10⁶ s^-1·cm^-2 in presence of fluorescence excitation source, and 2.4 × 10⁶ s^-1·cm^-2 at 90 °C. From a thermal management point of view, we have obtained heating and cooling rates both equal to 2.2 °C/s, and a temperature sensor sensitivity of about 3 mV/°C even in presence of light. The achieved performances demonstrate the possibility to simultaneously use all integrated sensors and actuators, making promising the presented platform for a wide range of application fields.

Mixing Performance of a Planar Asymmetric Contraction-and-Expansion Micromixer

Micromixers are one of the critical components in microfluidic devices. They significantly affect the efficiency and sensitivity of microfluidics-based lab-on-a-chip systems. This study introduces an efficient micromixer with a simple geometrical feature that enables easy incorporation in a microchannel network without compromising the original design of microfluidic devices. The study proposes a newly designed planar passive micromixer, termed a planar asymmetric contraction-and-expansion (P-ACE) micromixer, with asymmetric vertical obstacle structures. Numerical simulation and experimental investigation revealed that the optimally designed P-ACE micromixer exhibited a high mixing efficiency of 80% or more within a microchannel length of 10 mm over a wide range of Reynolds numbers (0.13 ≤ Re ≤ 13), eventually attaining approximately 90% mixing efficiency within a 20 mm microchannel length. The highly asymmetric geometric features of the P-ACE micromixers enhance mixing because of their synergistic effects. The flow velocities and directions of the two fluids change differently while alternately crossing the longitudinal centerline of the microchannel, with the obstacle structures asymmetrically arranged on both sidewalls of the rectangular microchannel. This flow behavior increases the interfacial contact area between the two fluids, thus promoting effective mixing in the P-ACE micromixer. Further, the pressure drops in the P-ACE micromixers were experimentally investigated and compared with those in a serpentine micromixer with a perfectly symmetric mixing unit.

Research Progress and Future Trends of Microfluidic Paper-Based Analytical Devices in In-Vitro Diagnosis

In vitro diagnosis (IVD) has become a hot topic in laboratory research and achievement transformation. However, due to the high cost, and time-consuming and complex operation of traditional technologies, some new technologies are being introduced into IVD, to solve the existing problems. As a result, IVD has begun to develop toward point-of-care testing (POCT), a subdivision field of IVD. The pandemic has made governments and health institutions realize the urgency of accelerating the development of POCT. Microfluidic paper-based analytical devices (μPADs), a low-cost, high-efficiency, and easy-to-operate detection platform, have played a significant role in advancing the development of IVD. μPADs are composed of paper as the core material, certain unique substances as reagents for processing the paper, and sensing devices, as auxiliary equipment. The published reviews on the same topic lack a comprehensive and systematic introduction to μPAD classification and research progress in IVD segmentation. In this paper, we first briefly introduce the origin of μPADs and their role in promoting IVD, in the introduction section. Then, processing and detection methods for μPADs are summarized, and the innovative achievements of μPADs in IVD are reviewed. Finally, we discuss and prospect the upgrade and improvement directions of μPADs, in terms of portability, sensitivity, and automation, to help researchers clarify the progress and overcome the difficulties in subsequent μPAD research.

A microfluidic device and instrument prototypes for the detection of Escherichia coli in water samples using a phage-based bioluminescence assay

Current quantification methods of Escherichia coli (E. coli) contamination in water samples involve long incubation, laboratory equipment and facilities, or complex processes that require specialized training for accurate operation and interpretation. To address these limitations, we have developed a microfluidic device and portable instrument prototypes capable of performing a rapid and highly sensitive bacteriophage-based assay to detect E. coli cells with detection limit comparable to traditional methods in a fraction of the time. The microfluidic device combines membrane filtration and selective enrichment using T7-NanoLuc-CBM, a genetically engineered bacteriophage, to identify 4.1 E. coli CFU in 100 mL of drinking water within 5.5 hours. The microfluidic device was designed and tested to process up to 100 mL of real-world drinking water samples with turbidities below 10 NTU. Prototypes of custom instrumentation, compatible with our valveless microfluidic device and capable of performing all of the assay's units of operation with minimal user intervention, demonstrated similar assay performance to that obtained on the benchtop assay. This research is the first step towards a faster, portable, and semi-automated, phage-based microfluidic platform for improved in-field water quality monitoring in low-resource settings.

Conventional and Microfluidic Methods for the Detection of Nucleic Acid of SARS-CoV-2

Nucleic acid testing (NAT) played a crucial role in containing the spread of SARS-CoV-2 during the epidemic. The gold standard technique, the quantitative real-time polymerase chain reaction (qRT-PCR) technique, is currently used by the government and medical boards to detect SARS-CoV-2. Due to the limitations of this technology, it is not capable of meeting the needs of large-scale rapid detection. To solve this problem, many new techniques for detecting nucleic acids of SARS-CoV-2 have been reported. Therefore, a review that systematically and comprehensively introduces and compares various detection technologies is needed. In this paper, we not only review the traditional NAT but also provide an overview of microfluidic-based NAT technologies and summarize and discuss the characteristics and development prospects of these techniques.

Diagnostic assay and technology advancement for detecting SARS-CoV-2 infections causing the COVID-19 pandemic

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-caused COVID-19 pandemic has transmitted to humans in practically all parts of the world, producing socio-economic turmoil. There is an urgent need for precise, fast, and affordable diagnostic testing to be widely available for detecting SARS-CoV-2 and its mutations in various phases of the disease. Early diagnosis with great precision has been achieved using real-time polymerase chain reaction (RT-PCR) and similar other molecular methods, but theseapproaches are costly and involve rigorous processes that are not easily obtainable. Conversely, immunoassays that detect a small number of antibodies have been employed for quick, low-cost tests, but their efficiency in diagnosing infected people has been restricted. The use of biosensors in the detection of SARS-CoV-2 is vital for the COVID-19 pandemic’s control. This review gives an overview of COVID-19 diagnostic approaches that are currently being developed as well as nanomaterial-based biosensor technologies, to aid future technological advancement and innovation. These approaches can be integrated into point-of-care (POC) devices to quickly identify a large number of infected patients and asymptomatic carriers. The ongoing research endeavors and developments in complementary technologies will play a significant role in curbing the spread of the COVID-19 pandemic and fill the knowledge gaps in current diagnostic accuracy and capacity.

Portable on-chip colorimetric biosensing platform integrated with a smartphone for label/PCR-free detection of Cryptosporidium RNA

Cryptosporidium, a protozoan pathogen, is a leading threat to public health and the economy. Herein, we report the development of a portable, colorimetric biosensing platform for the sensitive, selective and label/PCR-free detection of Cryptosporidium RNA using oligonucleotides modified gold nanoparticles (AuNPs). A pair of specific thiolated oligonucleotides, complementary to adjacent sequences on Cryptosporidium RNA, were attached to AuNPs. The need for expensive laboratory-based equipment was eliminated by performing the colorimetric assay on a micro-fabricated chip in a 3D-printed holder assembly. A smartphone camera was used to capture an image of the color change for quantitative analysis. The detection was based on the aggregation of the gold nanoparticles due to the hybridization between the complementary Cryptosporidium RNA and the oligonucleotides immobilized on the AuNPs surface. In the complementary RNA's presence, a distinctive color change of the AuNPs (from red to blue) was observed by the naked eye. However, in the presence of non-complementary RNA, no color change was observed. The sensing platform showed wide linear responses between 5 and 100 µM with a low detection limit of 5 µM of Cryptosporidium RNA. Additionally, the sensor developed here can provide information about different Cryptosporidium species present in water resources. This cost-effective, easy-to-use, portable and smartphone integrated on-chip colorimetric biosensor has great potential to be used for real-time and portable POC pathogen monitoring and molecular diagnostics.

Role of nanotechnology in animal production and veterinary medicine

Nanotechnology is the discipline and technology of small and specific things that are < 100 nm in size. Because of their extremely miniscule size, any changes in their chemical and physical structure may show higher reactivity and solubility than larger particles. Nanotechnology plays a vital role in every field of life. It is considered one of the most bleeding edge field of scientific research. It has already several applications in a myriad of disciplines while its application in the field of animal production and veterinary medicine is still experimental in nature. But, in recent years, the role of nanotechnology in the aforementioned fields of scientific inquiry has shown great progress. These days, nanotechnology has been employed to revolutionize drug delivery systems and diagnose atypical diseases. Applications of nanoparticle technology in the field of animal reproduction and development of efficacious vaccines have been at the forefront of scientific endeavors. Additionally, their impacts on meat and milk quality are also being judiciously inquired in recent decades. Veterinary nanotechnology has great potential to improve diagnosis and treatment, and provide new tools to this field. This review focuses on some noteworthy applications of nanoparticles in the field of animal production and their future perspectives.

Microfluidic electrical cell lysis for high-throughput and continuous production of cell-free varicella-zoster virus

Varicella-zoster virus (VZV), the causative agent of varicella and herpes zoster, is highly cell-associated and spreads via cell-to-cell contact in tissue culture. The lack of cell-free VZV hampers studies on VZV biology as well as antiviral and vaccine development. In the present study, a poly(methylmethacrylate) microfluidic device integrated with arrays of microelectrode was fabricated to continuously electrolyse VZV-infected cells to produce cell-free viruses. By designing multiple constrictions and microelectrode arrays, a high electric field is focused on the constricted region of the microchannel to disrupt large numbers of virus-infected cells with high-throughput on a microfluidic platform. Plaque assay and scanning electron microscopy were conducted to quantify and characterize cell-free VZV produced using the microfluidic continuous-flow electrical cell lysis device. The process of microfluidic electrical cell lysis followed by subsequent filtration and virus concentration process yielded a 1.4-2.1 × 10⁴ plaque-forming units (PFUs) per mL of cell-free VZV from 7.0 × 10⁶ VZV-infected human foreskin fibroblasts (HFF) cells. The high electric field formed inside a microfluidic channel combined with the continuous-flow of virus-infected cells within the microchannel enabled the rapid and efficient production of high-titer cell-free virus in large quantities with relatively low input of the voltage.

Development of sponge-like cellulose colorimetric swab immobilized with anthocyanin from red-cabbage for sweat monitoring

Novel sponge-like biochromic swab was developed via immobilization of natural anthocyanin (Cy) biomolecular probe into microporous cellulose aerogel. The current biosensor is characterized with simple preparation, environmentally-friendly, biocompatibility, biodegradability, flexibility, portability and reversibility. This biochromic sponge-like aerogel detector displayed a color change from pink to green-yellow in response to the biochemical changes occurs to sweat. This could be ascribed to intramolecular charge transfer occurs to the molecular system of Cy. Thus, the anthocyanin probe displayed colorimetric variations in UV-Vis absorption spectra via a blue shifting from 620 to 529 nm when raising the pH value of the prepared mimic sweat solution. Natural pH sensitive anthocyanin spectroscopic probe was extracted from red-cabbage plant, characterized by HPLC, and encapsulated into microporous cellulose. The microporous sponge-like cellulose swab was prepared by activating wood pulp utilizing phosphoric acid, and then subjected to freeze-drying. This anthocyanin probe is highly soluble in water. Thus, it was encapsulated as a direct dye into cellulose substrate during the freeze-drying process. To allow a better fixation of this water-soluble anthocyanin probe to the cellulose substrate, potash alum was added to the freeze-dried mixture to act as a fixing agent or mordant (M) generating Cy/M coordination complex. The produced Cy/M nanoparticles (NPs) were explored by transmission electron microscopy (TEM). The morphological features of the generated aerogels were investigated by scan electron microscope (SEM), energy-dispersive X-ray (EDX) spectra, and Fourier-transform infrared spectra (FT-IR). The cytotoxicity of the prepared aerogel-based biosensor was also evaluated. The naked-eye colorimetric changes were studied by exploring color strength, UV-Vis spectra and CIE Lab colorimetric coordinates.

Point-of-Care Pathogen Detection with CRISPR-based Programmable Nucleic Acid Binding Proteins

The contemporary discovery of extremely versatile engineered nucleic acid-binding proteins has transformed a brave new world in the genome-editing scientific area. Clustered regularly interspaced short palindromic repeats (CRISPR)-mediated programmable nucleic acid-binding proteins have brought about a revolution in diagnostic platforms. The groundbreaking finding that bacteria and archaea that harbored prokaryotes have transmitted adaptive immunity through CRISPR and CRISPR-associated (Cas) proteins has driven revolutionary advances in molecular biology. Importantly, advances in gene editing focus how expanding visions in CRISPR-Cas biology are revolutionizing the area of molecular diagnostics for identifying DNA and RNA in emerging microbiological pathogens, for single nucleotide polymorphism (SNP) identifications, and for cell-free mutation. Recent advances, such as improvements in multiplexing and quantitative capabilities as well as instrument-free detection of nucleic acids, will potentially leverage the introduction of these novel technologies to detecting bacteria and viruses at the point of care (POC). In this review, we highlight the fundamental features of CRISPR/Cas-based molecular diagnostic technologies and summarize a vision of the next applications for identifying pathogens in POC settings.

SARS-CoV-2 in environmental perspective: Occurrence, persistence, surveillance, inactivation and challenges

The unprecedented global spread of the severe acute respiratory syndrome (SARS) caused by SARS-CoV-2 is depicting the distressing pandemic consequence on human health, economy as well as ecosystem services. So far novel coronavirus (CoV) outbreaks were associated with SARS-CoV-2 (2019), middle east respiratory syndrome coronavirus (MERS-CoV, 2012), and SARS-CoV-1 (2003) events. CoV relates to the enveloped family of Betacoronavirus (βCoV) with positive-sense single-stranded RNA (+ssRNA). Knowing well the persistence, transmission, and spread of SARS-CoV-2 through proximity, the faecal-oral route is now emerging as a major environmental concern to community transmission. The replication and persistence of CoV in the gastrointestinal (GI) tract and shedding through stools is indicating a potential transmission route to the environment settings. Despite of the evidence, based on fewer reports on SARS-CoV-2 occurrence and persistence in wastewater/sewage/water, the transmission of the infective virus to the community is yet to be established. In this realm, this communication attempted to review the possible influx route of the enteric enveloped viral transmission in the environmental settings with reference to its occurrence, persistence, detection, and inactivation based on the published literature so far. The possibilities of airborne transmission through enteric virus-laden aerosols, environmental factors that may influence the viral transmission, and disinfection methods (conventional and emerging) as well as the inactivation mechanism with reference to the enveloped virus were reviewed. The need for wastewater epidemiology (WBE) studies for surveillance as well as for early warning signal was elaborated. This communication will provide a basis to understand the SARS-CoV-2 as well as other viruses in the context of the environmental engineering perspective to design effective strategies to counter the enteric virus transmission and also serves as a working paper for researchers, policy makers and regulators.

Ozonation enhancement of low cost double-stranded DNA binding dye based fluorescence measurement of total bacterial load in water

We demonstrated the feasibility of using ozonation to enhance the performance of dsDNA binding dye SYBR Green I in the fluorescence measurement of total bacterial load in water. Unlike its membrane permeable but expensive equivalent such as SYTO82 dye, SYBR Green I is many times cheaper but membrane impermeable. Ozonation allowed SYBR Green I dye to permeate the membrane and bind with the dsDNA within by first breaching it. Using E. coli K12 bacteria at serial dilution ratios from 1/1 (980 CFU mL⁻¹) to 1/200, we achieved corresponding quantification from 618.7 ± 9.4 to 68.0 ± 1.9 RFU (100 to 11.00% normalized RFU). In comparison, plate counting and optical density measurement were only able to quantify up till a serial dilution ratio of 1/50 (40 CFU mL⁻¹ and 0.0421, respectively). Most importantly with ozonation, the sensitivity of SYBR Green I dye based fluorescence measurement was improved by ∼140 to 210% as compared to that without ozonation. Given its low electrical power consumption, lab-on-chip compatibility and reagent-less nature, ozonation is highly compatible with portable fluorimeters to realize low-cost monitoring of total bacterial load in water.

Principle of ozonation enhanced dsDNA binding dye based fluorescence measurement of total bacterial load in water.

Opportunities for the application of real-time bacterial cell analysis using flow cytometry for the advancement of sterilization microbiology

Medical devices provide critical care and diagnostic applications through patient contact. Sterility assurance level (SAL) may be defined as the probability of a single viable micro-organism occurring on an item after a sterilization process. Sterilization microbiology often relies upon using an overkill validation method where a 12-log reduction in recalcitrant bacterial endospore population occurs during the process that exploits conventional laboratory-based culture media for enumeration. This timely review explores key assumptions underpinning use of conventional culture-based methods in sterilization microbiology. Consideration is given to how such methods may limit the ability to fully appreciate the inactivation kinetics of a sterilization process such as vaporized hydrogen peroxide (VH2O2) sterilization, and consequently design efficient sterilization processes. Specific use of the real-time flow cytometry (FCM) is described by way of elucidating the practical relevance of these limitation factors with implications and opportunities for the sterilization industry discussed. Application of FCM to address these culture-based limitation factors will inform real-time kinetic inactivation modelling and unlock potential to embrace emerging opportunities for pharma, medical device and sterilization industries including potentially disruptive applications that may involve reduced usage of sterilant.

Chemically robust succinimide-group-assisted irreversible bonding of poly(dimethylsiloxane)-thermoplastic microfluidic devices at room temperature

This study investigates surface chemical modification using anhydride silane and amino silane reagents at room temperature (RT) to realize bonding between silicon-based PDMS and non-silicon thermoplastics. The anhydride silane shows vigorous activity against water, forming a terminal dicarboxylic acid in the plasma-activated elastomeric poly(dimethylsiloxane) (PDMS) surface, and it can readily react with amino-silane-modified thermoplastic surfaces, resulting in a permanent bond via the formation of a stable succinimide group without the requirement for high temperature or additional pressure to initiate the bonding. The modified surfaces of PDMS and thermoplastics were successfully characterized by water contact angle measurement, fluorescence measurement, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The bond strength values of PDMS-thermoplastic assemblies, measured by the tensile test for PDMS-polystyrene (PS), PDMS-poly(methyl methacrylate) (PMMA), PDMS-polycarbonate (PC), and PDMS-poly(ethyl terephthalate) (PET) assemblies, were found to be approximately 519.5 ± 6, 259 ± 15, 476.6 ± 8, and 458.2 ± 27 kPa, respectively. Moreover, the bond strength was further examined by performing a burst test for PDMS-PMMA, PDMS-PS, PDMS-PC, and PDMS-PET microfluidic devices, which were found to have the maximum pressure values at approximately 344.73, 448.15, 413.68, and 379.21 kPa, respectively. Based on these results, the hybrid microfluidic devices can be used for high-pressure experiments such as blood plasma separation and continuous-flow polymerase chain reaction (CF-PCR). We have also performed the large area bonding of the PDMS-PC assembly (10 × 10 cm2), ensuring the high robustness and reliability of the proposed surface chemical bonding method.

Viral indicators for tracking domestic wastewater contamination in the aquatic environment

Waterborne enteric viruses are an emerging cause of disease outbreaks and represent a major threat to global public health. Enteric viruses may originate from human wastewater and can undergo rapid transport through aquatic environments with minimal decay. Surveillance and source apportionment of enteric viruses in environmental waters is therefore essential for accurate risk management. However, individual monitoring of the >100 enteric viral strains that have been identified as aquatic contaminants is unfeasible. Instead, viral indicators are often used for quantitative assessments of wastewater contamination, viral decay and transport in water. An ideal indicator for tracking wastewater contamination should be (i) easy to detect and quantify, (ii) source-specific, (iii) resistant to wastewater treatment processes, and (iv) persistent in the aquatic environment, with similar behaviour to viral pathogens. Here, we conducted a comprehensive review of 127 peer-reviewed publications, to critically evaluate the effectiveness of several viral indicators of wastewater pollution, including common enteric viruses (mastadenoviruses, polyomaviruses, and Aichi viruses), the pepper mild mottle virus (PMMoV), and gut-associated bacteriophages (Type II/III FRNA phages and phages infecting human Bacteroides species, including crAssphage). Our analysis suggests that overall, human mastadenoviruses have the greatest potential to indicate contamination by domestic wastewater due to their easy detection, culturability, and high prevalence in wastewater and in the polluted environment. Aichi virus, crAssphage and PMMoV are also widely detected in wastewater and in the environment, and may be used as molecular markers for human-derived contamination. We conclude that viral indicators are suitable for the long-term monitoring of viral contamination in freshwater and marine environments and that these should be implemented within monitoring programmes to provide a holistic assessment of microbiological water quality and wastewater-based epidemiology, improve current risk management strategies and protect global human health.

From hazard analysis to risk control using rapid methods in microbiology: A practical approach for the food industry

The prevention of foodborne diseases is one of the main objectives of health authorities. To this effect, analytical techniques to detect and/or quantify the microbiological contamination of foods prior to their release onto the market are required. Management and control of foodborne pathogens have generally been based on conventional detection methodologies, which are not only time-consuming and labor-intensive but also involve high consumable materials costs. However, this management perspective has changed over time given that the food industry requires efficient analytical methods that obtain rapid results. This review covers the historical context of traditional methods and their passage in time through to the latest developments in rapid methods and their implementation in the food sector. Improvements and limitations in the detection of the most relevant pathogens are discussed from a perspective applicable to the current situation in the food industry. Considering efforts that are being done and recent developments, rapid and accurate methods already used in the food industry will be also affordable and portable and offer connectivity in near future, which improves decision-making and safety throughout the food chain.

Integrated Electrochemical Biosensors for Detection of Waterborne Pathogens in Low-Resource Settings

More than 783 million people worldwide are currently without access to clean and safe water. Approximately 1 in 5 cases of mortality due to waterborne diseases involve children, and over 1.5 million cases of waterborne disease occur every year. In the developing world, this makes waterborne diseases the second highest cause of mortality. Such cases of waterborne disease are thought to be caused by poor sanitation, water infrastructure, public knowledge, and lack of suitable water monitoring systems. Conventional laboratory-based techniques are inadequate for effective on-site water quality monitoring purposes. This is due to their need for excessive equipment, operational complexity, lack of affordability, and long sample collection to data analysis times. In this review, we discuss the conventional techniques used in modern-day water quality testing. We discuss the future challenges of water quality testing in the developing world and how conventional techniques fall short of these challenges. Finally, we discuss the development of electrochemical biosensors and current research on the integration of these devices with microfluidic components to develop truly integrated, portable, simple to use and cost-effective devices for use by local environmental agencies, NGOs, and local communities in low-resource settings.

Microfluidic device fabrication mediated by surface chemical bonding

This review discusses on various bonding techniques for fabricating microdevices with a special emphasis on the modification of surface assisted by the use of chemicals to assemble microfluidic devices at room temperature under atmospheric pressure.

iso-μmGene: an isothermal amplification-based portable microfluidic system for simple, reliable and flexibly multiplexed genetic identification and quantification

We present a portable microfluidic LAMP system (iso-μmGene) with features of multi-well chips for convenient filling and reliable sealing, flexible detection throughput, and stand-alone and well-performing point of care device for genetic testing.

A 3D mixing-based portable magnetic device for fully automatic immunofluorescence staining of γ-H2AX in UVC-irradiated CD4+ cells

Immunofluorescence (IF) is a common method used in cell biology. The conventional protocol for IF staining is time and labor-intensive, operator dependent and reagent-consuming. Magnetic Bead (MB)-based microdevices are frequently utilized in cellular assays, but integration of simple and efficient mixing with downstream multi-step manipulation of MBs for automatic IF staining is still challenging. We herein present a portable, inexpensive and integratable device for MB-based automatic IF staining. First, a front-end cell capture step is performed using a 3D-mixing module, which is built upon a novel mechanism named ec-2MagRotors and generates periodically changing 3D magnetic fields. A 5-fold enhancement of cell capture efficiency was attained even with a low bead-to-cell concentration ratio (5 : 1), when conducting magnetic 3D mixing. Second, a 1D-moving module is employed downstream to automatically manipulate MB–cell complexes for IF staining. Further, a simplified protocol for staining of γ-H2AX, a biomarker widely used in evaluation of cell radiation damage, is presented for proof-of-principle study of the magnetic device. Using UVC-irradiated CD4⁺ cells as samples, our device achieved fully automatic γ-H2AX staining within 40 minutes at room temperature and showed a linear dose–response relationship. The developed portable magnetic device is automatic, efficient, cost-effective and simple-to-use, holding great potential for applications in different IF assays.

A 3D mixing-based portable magnetic device to perform on-chip efficient cell capture and automatic intracellular immunofluorescence (IF) staining is presented.

Recent Progress in Lab-On-a-Chip Systems for the Monitoring of Metabolites for Mammalian and Microbial Cell Research

Lab-on-a-chip sensing technologies have changed how cell biology research is conducted. This review summarises the progress in the lab-on-a-chip devices implemented for the detection of cellular metabolites. The review is divided into two subsections according to the methods used for the metabolite detection. Each section includes a table which summarises the relevant literature and also elaborates the advantages of, and the challenges faced with that particular method. The review continues with a section discussing the achievements attained due to using lab-on-a-chip devices within the specific context. Finally, a concluding section summarises what is to be resolved and discusses the future perspectives.

Fully Integrated and Foldable Microdevice Encapsulated with Agarose for Long-Term Storage Potential for Point-of-Care Testing of Multiplex Foodborne Pathogens

In this study, we fabricated a fully integrated and foldable microdevice encapsulated with 2-hydroxyethyl agarose for long-term storage of reagents for the integration of isothermal amplification and subsequent colorimetric detection for the monitoring of multiplex foodborne pathogens. The microdevice comprises a reaction zone and a detection zone. Both zones were made of a thin polycarbonate film and sealed by an adhesive film to make the microdevice foldable. The 2-hydroxyethyl agarose with loop-mediated isothermal amplification (LAMP) reagents and silver nitrate were deposited in the reaction and detection chambers, respectively, for long-term maintenance of reagent activity. A thin graphene-based heater associated with a handheld battery was employed to supply a constant temperature for on-chip amplification for 30 min. To simplify the sample manipulation process, a folding motion was adopted to allow the loading of LAMP amplicons from the reaction to the detection chambers and a colorimetric strategy was used for simple visual read-out of the results on-site. Using the agarose, the reagents were successfully stored and the reagent activity was maintained for at least 45 days. Prior to performing multiplex detections, the spiked juice was thermally lysed and purified with polydopamine-coated paper. The amplifications of Salmonella spp. and Escherichia coli O157:H7 (E. coli O157:H7) were successfully demonstrated based on the stable isothermal condition attained by the heater. The microdevice can detect the low concentration of E. coli O157:H7 at 2.5 × 10² copies per mL. The introduced microdevice acts as a simple and user-friendly platform for the identification of foodborne pathogens, paving the way for the construction of a truly portable, read-out microdevice for use as a public healthcare monitoring device.

Vacuum pouch microfluidic system and its application for thin-film micromixers

In this paper, a new type of lab-on-a-chip system, called vacuum pouch microfluidic (VPM) system, is reported. The core of this technology is a thin-film vacuum pouch that provides negative pumping pressure once it is activated. It is a degassed plastic bag that encloses a microfluidic chip. To demonstrate its performance, a passive thin-film micromixer is developed to integrate with the vacuum pouch. Since both the vacuum pouch and the thin-film micromixer are made of plastic film, they can be laminated together to construct a multi-layered microfluidic system. Excluding the storage reservoir, the overall thickness is 0.4 mm and the total weight is 0.3 g. This system provides a simple and straightforward strategy to construct a standalone, portable, flexible and low cost microfluidic system. The thin-film micromixer uses a serpentine channel to perform the mixing process, and it is found to have distinct mixing mechanisms under different Reynolds (Re) numbers, where lateral diffusion dominates for Re < 1 and chaotic mixing starts to contribute for Re > 10. Integrating this thin-film micromixer with the vacuum pouch, it is demonstrated that the negative pumping pressure can be adjusted by different storage reservoirs being placed at the channel exit. Reynolds numbers ranging from 0.0064 to 45.2 can be achieved. It also is verified that the VPM micromixer can be stored for 4 weeks to provide a sufficient flow rate for mixing applications. Finally, to demonstrate the feasibility of applying this VPM-based thin-film micromixer for on-site detection, this system is integrated with the colorimetric method. It is verified that a 10 μl ferrous ion solution and a 10 μl potassium ferricyanide solution can be mixed in 12 seconds, and concentrations of 10 ppm to 1000 ppm can be quantified by analyzing the colorimetric signal in hue values.

Fully integrated and slidable paper-embedded plastic microdevice for point-of-care testing of multiple foodborne pathogens

This study presents a slidable paper-embedded plastic microdevice fully integrated with DNA extraction, loop-mediated isothermal amplification (LAMP), and colorimetric detection functionalities. The developed microdevice consists of three layers that allow a sliding movement to mix the sample and reagents for DNA purification, amplification, and detection in a sequential manner. An FTA card was employed in the main chamber for DNA extraction and purification from intact bacterial cells. Subsequently, LAMP reagents and fuchsin-stored chambers were pulled toward the main chambers for DNA amplifications at 65 °C. After 30 min, the detection reagents-stored chambers were then moved to main chambers for result analysis. For the detection of LAMP amplicons, a novel colorimetric fuchsin-based method was employed. The wide applicability of the integrated microdevice was demonstrated by successfully screening three major foodborne pathogens, namely Salmonella spp., Staphylococcus aureus, and Escherichia coli O157:H7 in food, enabling highly sensitive detection of 3.0 × 10¹ CFU/sample of Gram-negative bacteria (Salmonella spp. and Escherichia coli O157:H7) and 3.0 × 10² CFU/sample of Gram-positive bacteria (Staphylococcus aureus) within 75 min. The portable and integrated microdevice presented in this study holds significant promise for point-of-care applications to accurately and rapidly diagnose and control diseases.