A single cell droplet microfluidic system for quantitative determination of food-borne pathogens

Biosensor in smart food traceability system for food safety and security

The burden of food contamination and food wastage has significantly contributed to the increased prevalence of foodborne disease and food insecurity all over the world. Due to this, there is an urgent need to develop a smarter food traceability system. Recent advancements in biosensors that are easy-to-use, rapid yet selective, sensitive, and cost-effective have shown great promise to meet the critical demand for onsite and immediate diagnosis and treatment of food safety and quality control (i.e. point-of-care technology). This review article focuses on the recent development of different biosensors for food safety and quality monitoring. In general, the application of biosensors in agriculture (i.e. pre-harvest stage) for early detection and routine control of plant infections or stress is discussed. Afterward, a more detailed advancement of biosensors in the past five years within the food supply chain (i.e. post-harvest stage) to detect different types of food contaminants and smart food packaging is highlighted. A section that discusses perspectives for the development of biosensors in the future is also mentioned.

Advances in AI-assisted biochip technology for biomedicine

The integration of biochips with AI opened up new possibilities and is expected to revolutionize smart healthcare tools within the next five years. The combination of miniaturized, multi-functional, rapid, high-throughput sample processing and sensing capabilities of biochips, with the computational data processing and predictive power of AI, allows medical professionals to collect and analyze vast amounts of data quickly and efficiently, leading to more accurate and timely diagnoses and prognostic evaluations. Biochips, as smart healthcare devices, offer continuous monitoring of patient symptoms. Integrated virtual assistants have the potential to send predictive feedback to users and healthcare practitioners, paving the way for personalized and predictive medicine. This review explores the current state-of-the-art biochip technologies including gene-chips, organ-on-a-chips, and neural implants, and the diagnostic and therapeutic utility of AI-assisted biochips in medical practices such as cancer, diabetes, infectious diseases, and neurological disorders. Choosing the appropriate AI model for a specific biomedical application, and possible solutions to the current challenges are explored. Surveying advances in machine learning models for biochip functionality, this paper offers a review of biochips for the future of biomedicine, an essential guide for keeping up with trends in healthcare, while inspiring cross-disciplinary collaboration among biomedical engineering, medicine, and machine learning fields.

Ag-coated tetrapod gold nanostars (Au@AgNSs) for acetamiprid determination in tea using SERS combined with microfluidics

Acetamiprid is an organic and highly toxic compound. Despite being widely used as a pesticide agent on a large scale, acetamiprid poses numerous health risks to living organisms, particularly humans. Herein, a strategy for the detection of acetamiprid in tea employing surface-enhanced Raman scattering (SERS) technology incorporated with a microfluidic chip was developed. Significantly, a seed-mediated growth approach was utilized to engineer Ag-coated tetrapod gold nanostars (core-shell Au@AgNSs) with four sharp tips. The synthesized Au@AgNSs showed an enhancement factor of 7.2 × 106. Solid works was used to figure out the two-channel microfluidic chip featuring four circular split hybrid structures, and COMSOL (Software for Multiphysics Simulation) was utilized to model the fusion effect between the substrate (Au@AgNSs) and the sample (acetamiprid). For the first time, the core-shell Au@AgNSs and acetamiprid were fused in the microfluidic channel to facilitate the detection of acetamiprid using SERS. The outcomes pointed out that the standard curve correlation coefficient between SERS intensity (876 cm-1) and the concentration of acetamiprid in tea specimens was calculated as 0.991, while the limit of detection (LOD) was 0.048 ng mL-1, which is well below the minimum limit set by the European Union (10 ng mL-1). Thus, the developed technique combining SERS and microfluidics demonstrated high potential for the rapid and efficient detection of acetamiprid in tea.

μMET: A Novel Reusable Microfluidic Chip for Precision Microbial Enumeration Tests

This work describes μMET, a novel microfluidic device for precise microbial enumeration tests (MET), essential in pharmaceutical, cosmetic, and food industries for ensuring microbiological safety standards. The μMET chip, comprising two hydrophobic glass plates, features a 15-μm deep μMET chamber enhanced by nanopillars and air supply units, facilitating both immediate and growth-dependent MET. Experimental results, with E. coli as a model bacterium, demonstrate that μMET provides counting linearity that outperforms traditional hemocytometers. The chip's design mitigates challenges like evaporation and ensures high-resolution imaging, making it a cost-effective and reusable alternative to conventional methods. Notably, bright-field μMET eliminates the need for fluorescent staining, streamlining operations with deep-learning algorithms for bacterial counts. Furthermore, we have developed a high-parallel μMET chip featuring 16 counting chambers, enhancing throughput and accommodating immediate and growth-dependent MET approaches. Its innovative design and adaptability render the μMET chip as a valuable tool for microbiology, medicine, and industry applications.

Culturing the unculturables: strategies, challenges, and opportunities for gut microbiome study

Metagenome sequencing techniques revolutionized the field of gut microbiome study. However, it is equipped with experimental and computational biases, which affect the downstream analysis results. Also, live microbial strains are needed for a better understanding of host-microbial crosstalks and for designing next-generation treatment therapies based on probiotic strains and postbiotic molecules. Conventional culturing methodologies are insufficient to get the dark gut matter on the plate; therefore, there is an urgent need to propose novel culturing methods that can fill the limitations of metagenomics. The current work aims to provide a consolidated evaluation of the available methods for host-microbe interaction with an emphasis on in vitro culturing of gut microbes using organoids, gut on a chip, and gut bioreactor. Further, the knowledge of microbial crosstalk in the gut helps us to identify core microbiota, and key metabolites that will aid in designing culturing media and co-culturing systems for gut microbiome study. After the deeper mining of the current culturing methods, we recommend that 3D-printed intestinal cells in a multistage continuous flow reactor equipped with an extended organoid system might be a good practical choice for gut microbiota-based studies.

Emergent Molecular Techniques Applied to the Detection of Porcine Viruses

Molecular diagnostic tests have evolved very rapidly in the field of human health, especially with the arrival of the recent pandemic caused by the SARS-CoV-2 virus. However, the animal sector is constantly neglected, even though accurate detection by molecular tools could represent economic advantages by preventing the spread of viruses. In this regard, the swine industry is of great interest. The main viruses that affect the swine industry are described in this review, including African swine fever virus (ASFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and porcine circovirus (PCV), which have been effectively detected by different molecular tools in recent times. Here, we describe the rationale of molecular techniques such as multiplex PCR, isothermal methods (LAMP, NASBA, RPA, and PSR) and novel methods such as CRISPR-Cas and microfluidics platforms. Successful molecular diagnostic developments are presented by highlighting their most important findings. Finally, we describe the barriers that hinder the large-scale development of affordable, accessible, rapid, and easy-to-use molecular diagnostic tests. The evolution of diagnostic techniques is critical to prevent the spread of viruses and the development of viral reservoirs in the swine industry that impact the possible development of future pandemics and the world economy.

Recent Progress in Spectroscopic Methods for the Detection of Foodborne Pathogenic Bacteria

Detection of foodborne pathogens at an early stage is very important to control food quality and improve medical response. Rapid detection of foodborne pathogens with high sensitivity and specificity is becoming an urgent requirement in health safety, medical diagnostics, environmental safety, and controlling food quality. Despite the existing bacterial detection methods being reliable and widely used, these methods are time-consuming, expensive, and cumbersome. Therefore, researchers are trying to find new methods by integrating spectroscopy techniques with artificial intelligence and advanced materials. Within this progress report, advances in the detection of foodborne pathogens using spectroscopy techniques are discussed. This paper presents an overview of the progress and application of spectroscopy techniques for the detection of foodborne pathogens, particularly new trends in the past few years, including surface-enhanced Raman spectroscopy, surface plasmon resonance, fluorescence spectroscopy, multiangle laser light scattering, and imaging analysis. In addition, the applications of artificial intelligence, microfluidics, smartphone-based techniques, and advanced materials related to spectroscopy for the detection of bacterial pathogens are discussed. Finally, we conclude and discuss possible research prospects in aspects of spectroscopy techniques for the identification and classification of pathogens.

Emerging Bioanalytical Devices and Platforms for Rapid Detection of Pathogens in Environmental Samples

The development of robust bioanalytical devices and biosensors for infectious pathogens is progressing well with the advent of new materials, concepts, and technology. The progress is also stepping towards developing high throughput screening technologies that can quickly identify, differentiate, and determine the concentration of harmful pathogens, facilitating the decision-making process for their elimination and therapeutic interventions in large-scale operations. Recently, much effort has been focused on upgrading these analytical devices to an intelligent technological platform by integrating them with modern communication systems, such as the internet of things (IoT) and machine learning (ML), to expand their application horizon. This review outlines the recent development and applications of bioanalytical devices and biosensors to detect pathogenic microbes in environmental samples. First, the nature of the recent outbreaks of pathogenic microbes such as foodborne, waterborne, and airborne pathogens and microbial toxins are discussed to understand the severity of the problems. Next, the discussion focuses on the detection systems chronologically, starting with the conventional methods, advanced techniques, and emerging technologies, such as biosensors and other portable devices and detection platforms for pathogens. Finally, the progress on multiplex assays, wearable devices, and integration of smartphone technologies to facilitate pathogen detection systems for wider applications are highlighted.

Micro-/nano-fluidic devices and in vivo fluorescence imaging based on quantum dots for cytologic diagnosis

Semiconductor quantum dots (QDs) possess attractive merits over traditional organic dyes, such as tunable emission, narrow emission spectra and good resistance against optical bleaching, and play a vital role in biosensing and bioimaging for cytologic diagnoses. Microfluidic technology is a potentially useful strategy, as it provides a rapid platform for tracing of disease markers. In vivo fluorescence imaging (FI) based on QDs has become popular for the analysis of complex biological processes. We herein report the applications of multifunctional fluorescent QDs as sensitive probes for diagnoses on cancer medicine and stem cell therapy via microfluidic chips and in vivo imaging.

Current development of bioanalytical sample preparation techniques in pharmaceuticals

Sample preparation is considered as the bottleneck step in bioanalysis because each biological matrix has its own unique challenges and complexity. Competent sample preparation to extract the desired analytes and remove redundant components is a crucial step in each bioanalytical approach. The matrix effect is a key hurdle in bioanalytical sample preparation, which has gained extensive consideration. Novel sample preparation techniques have advantages over classical techniques in terms of accuracy, automation, ease of sample preparation, storage, and shipment and have become increasingly popular over the past decade. Our objective is to provide a broad outline of current developments in various bioanalytical sample preparation techniques in chromatographic and spectroscopic examinations. In addition, how these techniques have gained considerable attention over the past decade in bioanalytical research is mentioned with preferred examples. Modern trends in bioanalytical sample preparation techniques, including sorbent-based microextraction techniques, are primarily emphasized.

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Bioanalytical sampling techniques are described with suitable applications in pharmaceuticals.

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The pros and cons of each bioanalytical sampling techniques are described.

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Relevant biological matrices are outlined.

A large-scale pico-droplet array for viable bacteria digital counting and dynamic tracking based on a thermosetting oil

A simple and rapid method was developed for real-time monitoring and digital counting of bacterial growth, and it can provide dynamic information at high resolution in the process.

Single-cell droplet microfluidics for biomedical applications

This review focuses on the recent advances in the fundamentals of single-cell droplet microfluidics and its applications in biomedicine, providing insights into design and establishment of single-cell microsystems and their further performance.

Single-Conidium Encapsulation in Oil-in-Water Pickering Emulsions at High Encapsulation Yield

This study presents an individual encapsulation of fungal conidia in an oil-in-water Pickering emulsion at a single-conidium encapsulation yield of 44%. The single-conidium encapsulation yield was characterized by analysis of confocal microscopy micrographs. Mineral oil-in-water emulsions stabilized by amine-functionalized titania dioxide (TiO₂-NH₂ or titania-NH₂) particles were prepared. The structure and the stability of the emulsions were investigated at different compositions by confocal microscopy and a LUMiSizer^® respectively. The most stable emulsions with a droplet size suitable for single-conidium encapsulation were further studied for their individual encapsulation capabilities. The yields of individual encapsulation in the emulsions; i.e., the number of conidia that were individually encapsulated out of the total number of conidia, were characterized by confocal microscopy assay. This rapid, easy to use approach to single-conidium encapsulation, which generates a significantly high yield with eco-friendly titania-based emulsions, only requires commonly used emulsification and agitation methods.

Recent Advancements in the Technologies Detecting Food Spoiling Agents

To match the current life-style, there is a huge demand and market for the processed food whose manufacturing requires multiple steps. The mounting demand increases the pressure on the producers and the regulatory bodies to provide sensitive, facile, and cost-effective methods to safeguard consumers' health. In the multistep process of food processing, there are several chances that the food-spoiling microbes or contaminants could enter the supply chain. In this contest, there is a dire necessity to comprehend, implement, and monitor the levels of contaminants by utilizing various available methods, such as single-cell droplet microfluidic system, DNA biosensor, nanobiosensor, smartphone-based biosensor, aptasensor, and DNA microarray-based methods. The current review focuses on the advancements in these methods for the detection of food-borne contaminants and pathogens.

Lab-on-a-chip technologies for food safety, processing, and packaging applications: a review

The advent of microfluidic systems has led to significant developments in lab-on-a-chip devices integrating several functions onto a single platform. Over the years, these miniature devices have become a promising tool for faster analytical testing, displaying high precision and efficiency. Nonetheless, most microfluidic systems are not commercially available. Research is actually undergoing on the application of these devices in environmental, food, biomedical, and healthcare industries. The lab-on-a-chip industry is predicted to grow annually by 20%. Here, we review the use of lab-on-a-chip devices in the food sector. We present fabrication technologies and materials to developing lab-on-a-chip devices. We compare electrochemical, optical, colorimetric, chemiluminescence and biological methods for the detection of pathogens and microorganisms. We emphasize emulsion processing, food formulation, nutraceutical development due to their promising characteristics. Last, smart packaging technologies like radio frequency identification and indicators are highlighted because they allow better product identification and traceability.

Multi-Organs-on-Chips for Testing Small-Molecule Drugs: Challenges and Perspectives

Organ-on-a-chip technology has been used in testing small-molecule drugs for screening potential therapeutics and regulatory protocols. The technology is expected to boost the development of novel therapies and accelerate the discovery of drug combinations in the coming years. This has led to the development of multi-organ-on-a-chip (MOC) for recapitulating various organs involved in the drug-body interactions. In this review, we discuss the current MOCs used in screening small-molecule drugs and then focus on the dynamic process of drug absorption, distribution, metabolism, and excretion. We also address appropriate materials used for MOCs at low cost and scale-up capacity suitable for high-performance analysis of drugs and commercial high-throughput screening platforms.

Single-cell analysis for the study of viral inhibitors

Stochastic outcomes of viral infections are attributed in large part to multiple layers of intrinsic and extrinsic heterogeneity that exist within a population of cells and viruses. Traditional methods in virology often lack the ability to demonstrate cell-to-cell variability in response to the invasion of viruses, and to decipher the sources of heterogeneities that are reflected in the variable infection dynamics. To overcome this challenge, the field of single-cell virology emerged less than a decade ago, enabling researchers to reveal the behavior of single, isolated, infected cells that has been masked in population-based assays. The use of microfluidics in single-cell virology, in particular, has resulted in the development of high-throughput devices that are capable of capturing, isolating, and monitoring single infected cells over the duration of an infection. Results from the studies of viral infection dynamics presented in this chapter indicate how single-cell data provide a more accurate prediction of the start time, replication rate, duration, and yield of infection when compared to population-based data. Additionally, single-cell analysis reveals striking differences between genetically distinct viruses that are almost indistinguishable in population methods. Importantly, both the efficacy and distinct mechanisms of action of antiviral compounds can be elucidated by using single-cell analysis.

Recent advances in single-cell analysis: Encapsulation materials, analysis methods and integrative platform for microfluidic technology

Traditional cell biology researches on cell populations by their origin, tissue, morphology, and secretions. Because of the heterogeneity of cells, research at the single-cell level can obtain more accurate and comprehensive information that reflects the physiological state and process of the cell, increasing the significance of single-cell analysis. The application of single-cell analysis is faced with the problem of contaminated or damaged cells caused by cell sample transportation. Reversible encapsulation of a single cell can protect cells from the external environment and open the encapsulation shell to release cells, thus preserving cell integrity and improving extraction efficiency of analytes. Meanwhile, microfluidic single cell analysis (MSCA) exhibits integration, miniaturization, and high throughput, which can considerably improve the efficiency of single-cell analysis. The researches on single-cell reversible encapsulation materials, single-cell analysis methods, and the MSCA integration platform are analyzed and summarized in this review. The problems of single-cell viability, network of single-cell signal, and simultaneous detection of multiple biotoxins in food based on single-cell are proposed for future research.

Recent Advances in Microfluidic Devices for Contamination Detection and Quality Inspection of Milk

Milk is a necessity for human life. However, it is susceptible to contamination and adulteration. Microfluidic analysis devices have attracted significant attention for the high-throughput quality inspection and contaminant analysis of milk samples in recent years. This review describes the major proposals presented in the literature for the pretreatment, contaminant detection, and quality inspection of milk samples using microfluidic lab-on-a-chip and lab-on-paper platforms in the past five years. The review focuses on the sample separation, sample extraction, and sample preconcentration/amplification steps of the pretreatment process and the determination of aflatoxins, antibiotics, drugs, melamine, and foodborne pathogens in the detection process. Recent proposals for the general quality inspection of milk samples, including the viscosity and presence of adulteration, are also discussed. The review concludes with a brief perspective on the challenges facing the future development of microfluidic devices for the analysis of milk samples in the coming years.

Modernization of Control of Pathogenic Micro-Organisms in the Food-Chain Requires a Durable Role for Immunoaffinity-Based Detection Methodology-A Review

Food microbiology is deluged by a vastly growing plethora of analytical methods. This review endeavors to color the context into which methodology has to fit and underlines the importance of sampling and sample treatment. The context is that the highest risk of food contamination is through the animal and human fecal route with a majority of foodborne infections originating from sources in mass and domestic kitchens at the end of the food-chain. Containment requires easy-to-use, failsafe, single-use tests giving an overall risk score in situ. Conversely, progressive food-safety systems are relying increasingly on early assessment of batches and groups involving risk-based sampling, monitoring environment and herd/flock health status, and (historic) food-chain information. Accordingly, responsible field laboratories prefer specificity, multi-analyte, and high-throughput procedures. Under certain etiological and epidemiological circumstances, indirect antigen immunoaffinity assays outperform the diagnostic sensitivity and diagnostic specificity of e.g., nucleic acid sequence-based assays. The current bulk of testing involves therefore ante- and post-mortem probing of humoral response to several pathogens. In this review, the inclusion of immunoglobulins against additional invasive micro-organisms indicating the level of hygiene and ergo public health risks in tests is advocated. Immunomagnetic separation, immunochromatography, immunosensor, microsphere array, lab-on-a-chip/disc platforms increasingly in combination with nanotechnologies, are discussed. The heuristic development of portable and ambulant microfluidic devices is intriguing and promising. Tant pis, many new platforms seem unattainable as the industry standard. Comparability of results with those of reference methods hinders the implementation of new technologies. Whatever the scientific and technological excellence and incentives, the decision-maker determines this implementation after weighing mainly costs and business risks.

Public-Health-Driven Microfluidic Technologies: From Separation to Detection

Separation and detection are ubiquitous in our daily life and they are two of the most important steps toward practical biomedical diagnostics and industrial applications. A deep understanding of working principles and examples of separation and detection enables a plethora of applications from blood test and air/water quality monitoring to food safety and biosecurity; none of which are irrelevant to public health. Microfluidics can separate and detect various particles/aerosols as well as cells/viruses in a cost-effective and easy-to-operate manner. There are a number of papers reviewing microfluidic separation and detection, but to the best of our knowledge, the two topics are normally reviewed separately. In fact, these two themes are closely related with each other from the perspectives of public health: understanding separation or sorting technique will lead to the development of new detection methods, thereby providing new paths to guide the separation routes. Therefore, the purpose of this review paper is two-fold: reporting the latest developments in the application of microfluidics for separation and outlining the emerging research in microfluidic detection. The dominating microfluidics-based passive separation methods and detection methods are discussed, along with the future perspectives and challenges being discussed. Our work inspires novel development of separation and detection methods for the benefits of public health.

Development of a rapid method for assessing the efficacy of antibacterial photocatalytic coatings

Visible-light activated photocatalytic coatings may represent an attractive antimicrobial solution in domains such as food, beverage, pharmaceutical, biomedical and wastewater remediation. However, testing methods to determine the antibacterial effects of photocatalytic coatings are limited and require specialist expertise. This paper describes the development of a method that enables rapid screening of coatings for photocatalytic-antibacterial activity. Relying on the ability of viable microorganisms to reduce the dye resazurin from a blue to a pink colour, the method relates the time taken to detect this colour change with number of viable microorganisms. The antibacterial activity of two photocatalytic materials (bismuth oxide and titanium dioxide) were screened against two pathogenic organisms (Escherichia coli and Klebsiella pneumoniae) that represent potential target microorganisms using traditional testing and enumeration techniques (BS ISO 27447:2009) and the novel rapid method. Bismuth oxide showed excellent antibacterial activity under ambient visible light against E. coli, but was less effective against K. pneumoniae. The rapid method showed excellent agreement with existing tests in terms of number of viable cells recovered. Due to advantages such as low cost, high throughput, and less reliance on microbiological expertise, this method is recommended for researchers seeking an inexpensive first-stage screen for putative photocatalytic-antibacterial coatings.

Highly sensitive real-time detection of intracellular oxidative stress and application in mycotoxin toxicity evaluation based on living single-cell electrochemical sensors

Single-cell electrochemical sensor is widely used in the local selective detection of single living cells because of its high spatial-temporal resolution and sensitivity, as well as its ability to obtain comprehensive cellular physiological states and processes with increased accuracy. Functionalized nanoprobes can detect the oxidative stress response of cells in single-cell electrochemical sensors. Moreover, the T-2 toxin is one of the most toxic mycotoxins and widely occurs in field crops. T-2 toxin can cause mitochondrial damage in cells and increase intracellular reactive oxygen species (ROS) in various cells. As the most representative free radical of intracellular ROS, H₂O₂ can effectively reflect the toxic effects of intracellular T-2 toxin. In this study, a functionalized gold nanoprobe was used to dynamically monitor the production of H₂O₂ in a single live human hepatoma cell HepG2 stimulated by mycotoxin T-2. The concentration of H₂O₂ produced by HepG2 cells stimulated by T-2 toxin at 1 ppb-1 ppm was linearly correlated, R² = 0.99055, and LOD = 0.13807 ng mL^-1. Sample spiking experiments were conducted, and the recovery rate of spiking was 81.19%-130.17%. A comparative analysis of differences in the current produced by multiple toxins, HT-29 cells, as well as single cells in cell populations, was performed. This method can be applied in real-time monitoring of mycotoxin toxicity during food processing in living cells and provides a novel idea for enhancing food quality and safety in a nanoenvironment.

Enhanced single-cell encapsulation in microfluidic devices: From droplet generation to single-cell analysis

Single-cell analysis to investigate cellular heterogeneity and cell-to-cell interactions is a crucial compartment to answer key questions in important biological mechanisms. Droplet-based microfluidics appears to be the ideal platform for such a purpose because the compartmentalization of single cells into microdroplets offers unique advantages of enhancing assay sensitivity, protecting cells against external stresses, allowing versatile and precise manipulations over tested samples, and providing a stable microenvironment for long-term cell proliferation and observation. The present Review aims to give a preliminary guidance for researchers from different backgrounds to explore the field of single-cell encapsulation and analysis. A comprehensive and introductory overview of the droplet formation mechanism, fabrication methods of microchips, and a myriad of passive and active encapsulation techniques to enhance single-cell encapsulation efficiency were presented. Meanwhile, common methods for single-cell analysis, especially for long-term cell proliferation, differentiation, and observation inside microcapsules, are briefly introduced. Finally, the major challenges faced in the field are illustrated, and potential prospects for future work are discussed.

Application of Microfluidic Chip Technology in Food Safety Sensing

Food safety analysis is an important procedure to control food contamination and supervision. It is urgently needed to construct effective methods for on-site, fast, accurate and popular food safety sensing. Among them, microfluidic chip technology exhibits distinguish advantages in detection, including less sample consumption, fast detection, simple operation, multi-functional integration, small size, multiplex detection and portability. In this review, we introduce the classification, material, processing and application of the microfluidic chip in food safety sensing, in order to provide a good guide for food safety monitoring.