An ELISA Lab-on-a-Chip (ELISA-LOC)

Polymeric and Paper-Based Lab-on-a-Chip Devices in Food Safety: A Review

Food quality and safety are important to protect consumers from foodborne illnesses. Currently, laboratory scale analysis, which takes several days to complete, is the main way to ensure the absence of pathogenic microorganisms in a wide range of food products. However, new methods such as PCR, ELISA, or even accelerated plate culture tests have been proposed for the rapid detection of pathogens. Lab-on-chip (LOC) devices and microfluidics are miniaturized devices that can enable faster, easier, and at the point of interest analysis. Nowadays, methods such as PCR are often coupled with microfluidics, providing new LOC devices that can replace or complement the standard methods by offering highly sensitive, fast, and on-site analysis. This review's objective is to present an overview of recent advances in LOCs used for the identification of the most prevalent foodborne and waterborne pathogens that put consumer health at risk. In particular, the paper is organized as follows: first, we discuss the main fabrication methods of microfluidics as well as the most popular materials used, and then we present recent literature examples for LOCs used for the detection of pathogenic bacteria found in water and other food samples. In the final section, we summarize our findings and also provide our point of view on the challenges and opportunities in the field.

Intervention of 3D printing in health care: transformation for sustainable development

INTRODUCTION

Three-dimensional (3D) technology is the practice of dropping material layer-by-layer in the construction of the desired object. The application of the 3D printing technique has been observed in miscellaneous domains. Personalized medicine becomes the most demanding trend in the health-care segment. Several advancements have been observed in the progress of 3D printing. However, the availability of finished products in the marketplace is very less. There is an utmost requirement to improve the knowledge and skills in the sustainable development of pharmaceutical and medical products by selecting suitable techniques and materials.

AREAS COVERED

This article covers the fundamental process of 3D printing, types, pharmaceutical-medical application, benefits, and challenges.

EXPERT OPINION

This technology is capable of designing the complex geometry of an organ. It is feasible to produce drug products by incorporating multiple drugs in various compartments in such a fashion that these drugs can release from the compartment at a predetermined rate. Additionally, this 3D process has the potential to revolutionize personalized therapy to different age-groups through design flexibility and accurate dosing. In the upcoming years, the potential application of this technology can be seen in a clinical setting where patients will get individualized medicine as per their needs.

Smartphone-Based Fully Automated Optofluidic Device with Laser Irradiation-Induced Image Whitening

Herein, we have developed a fully automated optofluidic device to execute enzyme-linked immunosorbent assay (ELISA) using an active 96-well hybrid lab-on-a-chip (LOC) device. To automate the solution loading into the reaction zone of the device and the post-assayed signal analysis, laser irradiation-induced image whitening was utilized with a smartphone-based optical platform. Two optical phenomena were utilized in our platform to detect the liquid in the reaction chamber using a smartphone. First, by Fresnel's equation, the refraction difference between air and water resulted in the intensity change of the reflected light from the reaction chamber. Therefore, when the liquid was entering into the reaction chamber, the intensity of the reflected light was changed. Second, when the light intensity increases, the smartphone-captured image whitens out due to saturation, even when the red color light was incident. Therefore, by measuring the RGB value of the smartphone image, the intensity changes by the liquid movement in the reaction chamber were successfully monitored. Our platform showed a low detection limit of 7.81 pg/mL for the detection of the NT-proBNP human cardiac biomarker with almost a half standard deviation, compared to the manually operated LOC-based ELISA. As a fully automated LOC adopting a conventional 96-well ELISA platform, we thus concluded that the developed platform can be widely applied for point-of-care clinical tests.

Point-of-Need Diagnostics for Foodborne Pathogen Screening

Foodborne illness is a major public health issue that results in millions of global infections annually. The burden of such illness sits mostly with developing countries, as access to advanced laboratory equipment and skilled lab technicians, as well as consistent power sources, is limited and expensive. Current gold standards in foodborne pathogen screening involve labor-intensive sample enrichment steps, pathogen isolation and purification, and costly readout machinery. Overall, time to detection can take multiple days, excluding the time it takes to ship samples to off-site laboratories. Efforts have been made to simplify the workflow of such tests by integrating multiple steps of foodborne pathogen screening procedures into a singular device, as well as implementing more point-of-need readout methods. In this review, we explore recent advancements in developing point-of-need devices for foodborne pathogen screening. We discuss the detection of surface markers, nucleic acids, and metabolic products using both paper-based and microfluidic devices, focusing primarily on developments that have been made between 2015 and mid-2020.

Microfluidic-Based Approaches for Foodborne Pathogen Detection

Food safety is of obvious importance, but there are frequent problems caused by foodborne pathogens that threaten the safety and health of human beings worldwide. Although the most classic method for detecting bacteria is the plate counting method, it takes almost three to seven days to get the bacterial results for the detection. Additionally, there are many existing technologies for accurate determination of pathogens, such as polymerase chain reaction (PCR), enzyme linked immunosorbent assay (ELISA), or loop-mediated isothermal amplification (LAMP), but they are not suitable for timely and rapid on-site detection due to time-consuming pretreatment, complex operations and false positive results. Therefore, an urgent goal remains to determine how to quickly and effectively prevent and control the occurrence of foodborne diseases that are harmful to humans. As an alternative, microfluidic devices with miniaturization, portability and low cost have been introduced for pathogen detection. In particular, the use of microfluidic technologies is a promising direction of research for this purpose. Herein, this article systematically reviews the use of microfluidic technology for the rapid and sensitive detection of foodborne pathogens. First, microfluidic technology is introduced, including the basic concepts, background, and the pros and cons of different starting materials for specific applications. Next, the applications and problems of microfluidics for the detection of pathogens are discussed. The current status and different applications of microfluidic-based technologies to distinguish and identify foodborne pathogens are described in detail. Finally, future trends of microfluidics in food safety are discussed to provide the necessary foundation for future research efforts.

Carbon nanotubes in microfluidic lab-on-a-chip technology: current trends and future perspectives

Advanced nanomaterials such as carbon nano-tubes (CNTs) display unprecedented properties such as strength, electrical conductance, thermal stability, and intriguing optical properties. These properties of CNT allow construction of small microfluidic devices leading to miniaturization of analyses previously conducted on a laboratory bench. With dimensions of only millimeters to a few square centimeters, these devices are called lab-on-a-chip (LOC). A LOC device requires a multidisciplinary contribution from different fields and offers automation, portability, and high-throughput screening along with a significant reduction in reagent consumption. Today, CNT can play a vital role in many parts of a LOC such as membrane channels, sensors and channel walls. This review paper provides an overview of recent trends in the use of CNT in LOC devices and covers challenges and recent advances in the field. CNTs are also reviewed in terms of synthesis, integration techniques, functionalization and superhydrophobicity. In addition, the toxicity of these nanomaterials is reviewed as a major challenge and recent approaches addressing this issue are discussed.

Streak Imaging Flow Cytometer for Rare Cell Analysis

There is a need for simple and affordable techniques for cytology for clinical applications, especially for point-of-care (POC) medical diagnostics in resource-poor settings. However, this often requires adapting expensive and complex laboratory-based techniques that often require significant power and are too massive to transport easily. One such technique is flow cytometry, which has great potential for modification due to the simplicity of the principle of optical tracking of cells. However, it is limited in that regard due to the flow focusing technique used to isolate cells for optical detection. This technique inherently reduces the flow rate and is therefore unsuitable for rapid detection of rare cells which require large volume for analysis.To address these limitations, we developed a low-cost, mobile flow cytometer based on streak imaging. In our new configuration we utilize a simple webcam for optical detection over a large area associated with a wide-field flow cell. The new flow cell is capable of larger volume and higher throughput fluorescence detection of rare cells than the flow cells with hydrodynamic focusing used in conventional flow cytometry. The webcam is an inexpensive, commercially available system, and for fluorescence analysis we use a 1 W 450 nm blue laser to excite Syto-9 stained cells with emission at 535 nm. We were able to detect low concentrations of stained cells at high flow rates of 10 mL/min, which is suitable for rapidly analyzing larger specimen volumes to detect rare cells at appropriate concentration levels. The new rapid detection capabilities, combined with the simplicity and low cost of this device, suggest a potential for clinical POC flow cytometry in resource-poor settings associated with global health.

Improving the Sensitivity and Functionality of Mobile Webcam-Based Fluorescence Detectors for Point-of-Care Diagnostics in Global Health

Resource-poor countries and regions require effective, low-cost diagnostic devices for accurate identification and diagnosis of health conditions. Optical detection technologies used for many types of biological and clinical analysis can play a significant role in addressing this need, but must be sufficiently affordable and portable for use in global health settings. Most current clinical optical imaging technologies are accurate and sensitive, but also expensive and difficult to adapt for use in these settings. These challenges can be mitigated by taking advantage of affordable consumer electronics mobile devices such as webcams, mobile phones, charge-coupled device (CCD) cameras, lasers, and LEDs. Low-cost, portable multi-wavelength fluorescence plate readers have been developed for many applications including detection of microbial toxins such as C. Botulinum A neurotoxin, Shiga toxin, and S. aureus enterotoxin B (SEB), and flow cytometry has been used to detect very low cell concentrations. However, the relatively low sensitivities of these devices limit their clinical utility. We have developed several approaches to improve their sensitivity presented here for webcam based fluorescence detectors, including (1) image stacking to improve signal-to-noise ratios; (2) lasers to enable fluorescence excitation for flow cytometry; and (3) streak imaging to capture the trajectory of a single cell, enabling imaging sensors with high noise levels to detect rare cell events. These approaches can also help to overcome some of the limitations of other low-cost optical detection technologies such as CCD or phone-based detectors (like high noise levels or low sensitivities), and provide for their use in low-cost medical diagnostics in resource-poor settings.

Biomarker detection for disease diagnosis using cost-effective microfluidic platforms

Early and timely detection of disease biomarkers can prevent the spread of infectious diseases, and drastically decrease the death rate of people suffering from different diseases such as cancer and infectious diseases. Because conventional diagnostic methods have limited application in low-resource settings due to the use of bulky and expensive instrumentation, simple and low-cost point-of-care diagnostic devices for timely and early biomarker diagnosis is the need of the hour, especially in rural areas and developing nations. The microfluidics technology possesses remarkable features for simple, low-cost, and rapid disease diagnosis. There have been significant advances in the development of microfluidic platforms for biomarker detection of diseases. This article reviews recent advances in biomarker detection using cost-effective microfluidic devices for disease diagnosis, with the emphasis on infectious disease and cancer diagnosis in low-resource settings. This review first introduces different microfluidic platforms (e.g. polymer and paper-based microfluidics) used for disease diagnosis, with a brief description of their common fabrication techniques. Then, it highlights various detection strategies for disease biomarker detection using microfluidic platforms, including colorimetric, fluorescence, chemiluminescence, electrochemiluminescence (ECL), and electrochemical detection. Finally, it discusses the current limitations of microfluidic devices for disease biomarker detection and future prospects.

Webcam-based flow cytometer using wide-field imaging for low cell number detection at high throughput

Here we describe a novel low-cost flow cytometer based on a webcam capable of low cell number detection in a large volume which may overcome the limitations of current flow cytometry. Several key elements have been combined to yield both high throughput and high sensitivity. The first element is a commercially available webcam capable of 187 frames per second video capture at a resolution of 320 × 240 pixels. The second element in this design is a 1 W 450 nm laser module for area-excitation, which combined with the webcam allows for rapid interrogation of a flow field. The final element is a 2D flow-cell which overcomes the flow limitation of hydrodynamic focusing and allows for higher sample throughput in a wider flow field. This cell allows for the linear velocity of target cells to be lower than in a conventional "1D" hydrodynamic focusing flow-cells typically used in cytometry at similar volumetric flow rates. It also allows cells to be imaged at the full frame rate of the webcam. Using this webcam-based flow cytometer with wide-field imaging, it was confirmed that the detection of fluorescently tagged 5 μm polystyrene beads in "1D" hydrodynamic focusing flow-cells was not practical for low cell number detection due to streaking from the motion of the beads, which did not occur with the 2D flow-cell design. The sensitivity and throughput of this webcam-based flow cytometer was then investigated using THP-1 human monocytes stained with SYTO-9 florescent dye in the 2D flow-cell. The flow cytometer was found to be capable of detecting fluorescently tagged cells at concentrations as low as 1 cell per mL at flow rates of 500 μL min(-1) in buffer and in blood. The effectiveness of detection was concentration dependent: at 100 cells per mL 84% of the cells were detected compared to microscopy, 10 cells per mL 79% detected and 1 cell per mL 59% of the cells were detected. With the blood samples spiked to 100 cells per mL, the average concentration for all samples was 91.4 cells per mL, with a 95% confidence interval of 86-97 cells per mL. These low cell concentrations and the large volume capabilities of the system may overcome the limitations of current cytometry, and are applicable to rare cell (such as circulating tumor cell) detection The simplicity and low cost of this device suggests that it may have a potential use in developing point-of-care clinical flow cytometry for resource-poor settings associated with global health.

Integration of genetically modified virus-like-particles with an optical resonator for selective bio-detection

A novel virus-like particle (TMV-VLP) receptor layer has been integrated with an optical microdisk resonator transducer for biosensing applications. This bioreceptor layer is functionalized with selective peptides that encode unique recognition affinities. Integration of bioreceptors with sensor platforms is very challenging due their very different compatibility regimes. The TMV-VLP nanoreceptor exhibits integration robustness, including the ability for self-assembly along with traditional top-down microfabrication processes. An optical microdisk resonator has been functionalized for antibody binding with this receptor, demonstrating resonant wavelength shifts of (Δλo) of 0.79 nm and 5.95 nm after primary antibody binding and enzyme-linked immunosorbent assay (ELISA), respectively, illustrating label-free sensing of this bonding event. This demonstration of label-free sensing with genetically engineered TMV-VLP shows the flexibility and utility of this receptor coating when considering integration with other existing transducer platforms.

Mobile flow cytometer for mHealth

Flow cytometry is used for cell counting and analysis in numerous clinical and environmental applications. However flow cytometry is not used in mHealth mainly because current flow cytometers are large, expensive, power-intensive devices designed to operate in a laboratory. Their design results in a lack of portability and makes them unsuitable for mHealth applications. Another limitation of current technology is the low volumetric throughput rates that are not suitable for rapid detection of rare cells.To address these limitations, we describe here a novel, low-cost, mobile flow cytometer based on wide-field imaging with a webcam for large volume and high throughput fluorescence detection of rare cells as a simulation for circulating tumor cells (CTCs) detection. The mobile flow cytometer uses a commercially available webcam capable of 187 frames per second video capture at a resolution of 320 × 240 pixels. For fluorescence detection, a 1 W 450 nm blue laser is used for excitation of Syto-9 fluorescently stained cells detected at 535 nm. A wide-field flow cell was developed for large volume analysis that allows for the linear velocity of target cells to be lower than in conventional hydrodynamic focusing flow cells typically used in cytometry. The mobile flow cytometer was found to be capable of detecting low concentrations at flow rates of 500 μL/min, suitable for rare cell detection in large volumes. The simplicity and low cost of this device suggests that it may have a potential clinical use for mHealth flow cytometry for resource-poor settings associated with global health.

Mycobacterium tuberculosis PPE protein Rv0256c induces strong B cell response in tuberculosis patients

Tuberculosis (TB) is one of the most important diseases of humans and major public health problem worldwide. Early and accurate diagnosis of TB is necessary for the treatment, prevention, and control of TB. Therefore, it is important to identify suitable antigens that can differentiate active tuberculosis patients from BCG-vaccinated individuals. In the present study, we have used Rv0256c (PPE2) protein of Mycobacterium tuberculosis to screen the sera of infected patients belonging to different clinical TB presentations, and BCG-vaccinated clinically healthy individuals by enzyme immunoassay. Our results demonstrated that Rv0256c displayed stronger and specific immunoreactivity against the sera obtained from clinically active tuberculosis patients compared to PPD and ESAT-6 and could differentiate the TB-patients from the BCG-vaccinated controls. Importantly, Rv0256c was also found to detect even the extrapulmonary and smear-negative pulmonary cases which often are tedious and difficult to detect using conventional diagnostic methods. This study suggests that Rv0256c can be used as a potential marker for the serodiagnosis of tuberculosis patients.