Development and Characterization of a Generic Microfluidic Subsystem toward Portable Biochemical Detection

This paper presents the development and characterization of a generic microfluidic system for magnetic bead-based biochemical detection. Microfluidic and electrochemical detection devices such as microvalves, flow sensors, biofilters, and immunosensors have been successfully developed and individually characterized in this work. Magnetically driven microvalves, pulsed-mode microflow sensors, magnetic particle separators as biofilters, and electrochemical immunosensors have been sep-arately fabricated and tested. The fabricated microfluidic components have been surface-mounted on the microfluidic motherboard for fully integrated microfluidic biochemical detection system. A magnetic bio-bead approach has been adopted for both sampling and manipulating target biological molecules. Magnetic beads were used as both substrate of antibodies and carriers of target antigens for magnetic bead-based immunoassay, which was chosen as a proof-of-concept for the generic microfluidic bio-chemical detection system. The microfluidic and electrochemical immunosensing experiment results obtained from this work have shown that the biochemical sensing capability of the complete microfluidic subsystem is suitable for portable biochemical detection of bio-molecules. The methodology and system, which has been developed in this work, can be extended to generic bio-molecule detection and analysis systems by replacing antibody/antigen with appropriate bio receptors/reagents such as DNA fragments or oligonucleotides for application towards DNA analysis and/or high throughput protein analysis.

In this paper, recent research activities at the Microsystems and BioMEMS Laboratory at the University of Cincinnati (UC) will be presented, which includes handheld biochemical detection systems with sampling and analysis capabilities and plastic based disposable biochips for clinical diagnostics. In the past few years, numerous microfluidic prototype devices and systems have been developed, specifically for biochemical warfare detection systems and portable diagnostic applications. BioMEMS-research team at the University of Cincinnati has been working on the development of a remotely accessible generic microfluidic system for biochemical detection and biomedical analysis, based on the concepts of both surface-mountable microfluidic motherboards and electrochemical detection techniques. The goal of this work is to develop a generic MEMS-based microfluidic system and to apply the fluidic system to detect bio-molecules such as specific proteins and/or antigens in liquid samples.

Here, an enzyme-free lateral flow aptasensor was designed by target-induced strand-displacement effect and followed by the activation of multi-component nucleic acid enzyme (MNAzyme)-mediated cleavage to enable rapid and portable ochratoxin A (OTA) detection. The substrate was prepared as an oligonucleotide strand modified with magnetic beads (MB) and human chorionic gonadotropin (hCG). The interaction of OTA with the aptamer induces the release of blocking DNA, which hybridized with three separated subunits of DNA, forming a sequence-specific MNAzyme catalytic core. This core subsequently initiated an enzyme-free MNAzyme cleavage reaction in the presence of the Mg2+ cofactor, cleaving a special substrate and releasing both the incomplete MNAzyme catalytic core and hCG-DNA probe. The incomplete MNAzyme catalytic core was then recognized by substrates once again, triggering a cascade recycling cleavage and resulting in the generation of a larger number of hCG-DNA probes. After magnetic enrichment, the free hCG-DNA probes flow through the pregnancy test strip (PTS) to the T line, generating a colorimetric readout that unequivocally confirms the presence of the target OTA. This work leverages the efficient enzyme-free cleavage amplification of MNAzyme and the PTS-based portable detection device, presenting a biosensing strategy with significant potential for sensitive and portable OTA detection. This method exhibited remarkable sensitivity and selectivity for OTA detection, boasting a detection limit of 5nM. The present study successfully demonstrated the practical application of this method on real samples, offering a viable alternative for rapid and portable detection of mycotoxins.

MicroRNAs (miRNAs) diagnostics can be useful for diagnosing or confirming miRNA abundance and are used in screening tests and to assess changes in miRNAs in vivo. At present, the use of traditional nucleic acid amplification assays to detect miRNAs has been limited in laboratory environment because of the time, equipment, and technical expertise required to perform these assays. A specialized, rapid affordable miRNA detection system is necessary when there are limited resources or point-of-care testing needs. We designed a portable and affordable fluorescence-based miRNA detection system based on isothermal signal amplification technology, using SYBR Green II as a fluorescent dye. To reduce costs, we chose LED as a light source and designed the corresponding optical path for LED. The portable detection system shows results consistent with those by real-time PCR, and can be used to detect miR-183 with a limit of detection of approximately 2fmol. We used the system to detect miR-183 in tissues and blood from patients with hepatocellular carcinoma (HCC). The results from the portable detection device were compared with those from clinical trials and indicated that the miR-183 fluorescence signal could successfully identify HCC and provide information related to cancer progression.

The paper describes the configuration effects of the auxiliary parts on the flow behavior around the microfluidic device. Recent development of the devices in MEMS is noticeable. The devices are manufactured in more complicated configuration and arrangement with the auxiliary part for the requirement of higher performance. An evaluation of the flow field around the microfluidic device is strongly required in MEMS design. The aim of the paper is to clarify the effect of the auxiliary part arrangement on the flow field around the micro flow sensor which has both the sensing element and the auxiliary parts such as the pins, pillars and electric bonding wires. The flow around the sensor is measured by using the Micro Particle Image Velocimetry (PIV) system. We investigate four types of the micro flow sensor with different configuration and arrangement of the pin, the bonding wires and the pillars. The result shows that the effect of the supporting pillars is negligible.

Microelectromechanical systems (MEMS) technology has matured to the point where practical biological and chemical applications are possible. One particularly active research area is in the development of lab-on-a-chip type systems. In order to create successful lab-on-a-chip and other microfluidic systems, it is necessary to have the capability of controlling and directing fluid flow. Such functionality can be found on the front end of a microfluidic system and is known as a fluid delivery or dosing subsystem. For a MEMS micro fluid dosing system to be realized, several components are necessary. The essential components include a fluid actuator, a fluidic control device, and micro plumbing. A prototype fluid delivery system is demonstrated here using a micropump as the fluid actuator, a thermal flow sensor as the fluidic control device, and micromachined couplers as plumbing. The technology to build these components has been developed and each of these components have been fabricated and tested. A prototype constructed of discrete components has also been demonstrated. A truly integrated, channel-based fluid dosing system can be achieved through device scaling.

This paper presents a portable phosphate detection system based on electrochemical reaction mechanism using cobalt modified microelectrodes. The microelectrodes were fabricated by MEMS (Micro-electromechanical Systems) technology and modified by electrodeposition of cobalt. The performances of the microsensors were characterized by testing a series of standard phosphate solution. MSP430F4793 microcontroller was applied to control the detection process at low power consumption. Comparing with the test results achieved by using traditional electrochemical workstation method, this portable detection system has similar characteristics with the concentration range from 10-6 to 10-4 mol/L.

Wearable microfluidic detection devices for noninvasive sweat analysis are highly desirable for human health monitoring. Herein, we present a bioenzyme-free microfluidic colorimetric detection device for simultaneous detection of creatinine (Cre), urea, and Mg2+ in sweat, enabling comprehensive kidney function and mental stress assessment. The device leverages a ternary catalytic system composed of H2MoO5 nanomaterial, Cu2+, and Cre, which exhibits significantly enhanced oxidase-like activity. This system directly catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to generate a blue product (ox-TMB), providing a robust platform for Cre detection without the need for bioenzymes. For urea and Mg2+ detection, 4-dimethylaminobenzaldehyde and chromium black T were employed as effective chromogenic reagents, respectively. A flexible multichannel microfluidic chip was fabricated, incorporating specific colorimetric reagent-modified paper chips into the corresponding reaction reservoirs. This design allows for the simultaneous detection of Cre, urea, and Mg2+ in sweat with linear ranges of 10-100 μM, 10-70 mM, and 0.5-8 mM, respectively. The device's performance was validated using actual sweat samples, with detection results analyzed via a smartphone application, demonstrating high accuracy and reliability. This work introduces a simple, low-cost, and stable bioenzyme-free microfluidic colorimetric detection device, offering significant potential for in situ and intelligent sweat analysis. The integration of smartphone technology further enhances its practicality, making it a promising tool for real-time health monitoring and point-of-care testing.

The past few decades has witnessed an intensive drive in the development of microfluidic technologies and devices that have tremendous applications in diverse sectors from defence to healthcare. Entire analytical protocols, including sample pretreatment, sample/reagent manipulation, separation, reaction, and detection can be performed significantly quicker on these miniaturised and compact devices. A broad range of existing and new materials from silicon, glass, polymers, and paper have been demonstrated as viable compatible materials for creating advanced and low-cost microfluidic devices, with embedded micrometre-sized elements, to provide unique and often combined functionalities for microfluidic processing. Based on the category of materials, fabrication techniques and examples of applications will be discussed in this chapter. Factors influencing the choice of material, cost of processing, and suitability of specific applications are included. The integration of microfluidic devices and detection technologies suggests a solid understanding of fabrication procedures and their limitations is essential to the development of commercial microfluidic devices.

Development and application of a low-cost and portable multi-channel spectral detection system for mutton adulteration

This account examines developments in "digital" biology and chemistry within the context of microfluidics, from a personal perspective. Using microfluidics as a frame of reference, we identify two areas of research within digital biology and chemistry that are of special interest: (i) the study of systems that switch between discrete states in response to changes in chemical concentration of signals, and (ii) the study of single biological entities such as molecules or cells. In particular, microfluidics accelerates analysis of switching systems (i.e., those that exhibit a sharp change in output over a narrow range of input) by enabling monitoring of multiple reactions in parallel over a range of concentrations of signals. Conversely, such switching systems can be used to create new kinds of microfluidic detection systems that provide "analog-to-digital" signal conversion and logic. Microfluidic compartmentalization technologies for studying and isolating single entities can be used to reconstruct and understand cellular processes, study interactions between single biological entities, and examine the intrinsic heterogeneity of populations of molecules, cells, or organisms. Furthermore, compartmentalization of single cells or molecules in "digital" microfluidic experiments can induce switching in a range of reaction systems to enable sensitive detection of cells or biomolecules, such as with digital ELISA or digital PCR. This "digitizing" offers advantages in terms of robustness, assay design, and simplicity because quantitative information can be obtained with qualitative measurements. While digital formats have been shown to improve the robustness of existing chemistries, we anticipate that in the future they will enable new chemistries to be used for quantitative measurements, and that digital biology and chemistry will continue to provide further opportunities for measuring biomolecules, understanding natural systems more deeply, and advancing molecular and cellular analysis. Microfluidics will impact digital biology and chemistry and will also benefit from them if it becomes massively distributed.

This paper presents the development and characterization of an integrated microfluidic biochemical detection system for fast and low-volume immunoassays using magnetic beads, which are used as both immobilization surfaces and bio-molecule carriers. Microfluidic components have been developed and integrated to construct a microfluidic biochemical detection system. Magnetic bead-based immunoassay, as a typical example of biochemical detection and analysis, has been successfully performed on the integrated microfluidic biochemical analysis system that includes a surface-mounted biofilter and electrochemical sensor on a glass microfluidic motherboard. Total time required for an immunoassay was less than 20 min including sample incubation time, and sample volume wasted was less than 50 microl during five repeated assays. Fast and low-volume biochemical analysis has been successfully achieved with the developed biofilter and immunosensor, which is integrated to the microfluidic system. Such a magnetic bead-based biochemical detection system, described in this paper, can be applied to protein analysis systems.

In this work, a low-field microfluidic nuclear magnetic resonance (NMR) detection device was developed by fabricating a multi-layer microfluidic NMR probe. In combination with biological sensor technology based on immunomagnetic nanoparticles (IMNPs), the microfluidic NMR detection device was used to rapidly distinguish the concentration of target tumor markers. The experimental results show that the concentration of the target tumor markers can be differentiated with high sensitivity and specificity by the rate of the transverse relaxation time change ΔT2 even with interference from other biomarkers. A good linear relationship between ΔT2 and the concentration of the target tumor markers was also found, indicating that the microfluidic NMR device could be used for quantitative detection of tumor markers. Finally, the validity of the microfluidic NMR device for detecting target tumor markers was proved by comparison with a commercial cell counter, and the results detected by the two devices have a good consistency with a correlation coefficient of 0.996. In conclusion, the presented low-field microfluidic NMR device is a potential tool for the rapid and accurate quantitative detection of tumor markers.

Structural health monitoring of structures in general usually require an expert to permanently attach a sensor onto a specific area. This would be important for mechanical structures with bolted joints, such as in aircrafts or even machines as human lives depend on its structural integrity. However, for large civil infrastructures with bolted joints, such as in cable stayed bridges, installing a monitoring system with a large number of sensors would be unrealistic as the cost of the system would be significantly high. In addition, the time frame for certain bolts to loosen for civil structures can be quite long and one could say that a real time monitoring system is unnecessary as a routine maintenance is conducted for civil structures. An effective way of identifying bolt loosening would be vital for safety inspectors to inspect the target structure with minimized time. Thus, in this study, a piezoelectric transducer based non-destructive testing method is introduced to identify bolt loosening. The concept of real time online monitoring could be replaced with the portable damage detection concept shown in this study as the proposed idea could minimize the overall cost of the maintenance process.

Single-cell biophysical properties play a crucial role in regulating cellular physiological states and functions, demonstrating significant potential in the fields of life sciences and clinical diagnostics. Therefore, over the last few decades, researchers have developed various detection tools to explore the relationship between the biophysical changes of biological cells and human diseases. With the rapid advancement of modern microfabrication technology, microfluidic devices have quickly emerged as a promising platform for single-cell analysis offering advantages including high-throughput, exceptional precision, and ease of manipulation. Consequently, this paper provides an overview of the recent advances in microfluidic analysis and detection systems for single-cell biophysical properties and their applications in the field of cancer. The working principles and latest research progress of single-cell biophysical property detection are first analyzed, highlighting the significance of electrical and mechanical properties. The development of data acquisition and processing methods for real-time, high-throughput, and practical applications are then discussed. Furthermore, the differences in biophysical properties between tumor and normal cells are outlined, illustrating the potential for utilizing single-cell biophysical properties for tumor cell identification, classification, and drug response assessment. Lastly, we summarize the limitations of existing microfluidic analysis and detection systems in single-cell biophysical properties, while also pointing out the prospects and future directions of their applications in cancer diagnosis and treatment.