Topography-assisted electromagnetic platform for blood-to-PCR in a droplet

A Rapid and Automated Device for Purifying Nucleic Acids

We have developed a rapid, automated nucleic acid purification device in a single cartridge containing silica-coated magnetic beads. We succeeded in extracting the matrix protein gene of influenza A virus from pharyngeal swab samples within 3 min. The device will be widely applicable to detect a specific gene from the various samples for clinical diagnosis and genetic research.

A parallelized microfluidic DNA bisulfite conversion module for streamlined methylation analysis

Aberrant methylation of DNA has been identified as an epigenetic biomarker for numerous cancer types. The vast majority of techniques aimed at detecting methylation require bisulfite conversion of the DNA sample prior to analysis, which until now has been a benchtop process. Although microfluidics has potential benefits of simplified operation, sample and reagent economy, and scalability, bisulfite conversion has yet to be implemented in this format. Here, we present a novel droplet microfluidic design that facilitates rapid bisulfite conversion by reducing the necessary processing steps while retaining comparable performance to existing methods. This new format has a reduced overall processing time and is readily scalable for use in high throughput DNA methylation analysis.

Droplet-based magnetic bead immunoassay using microchannel-connected multiwell plates (μCHAMPs) for the detection of amyloid beta oligomers

Multiwell plates are regularly used in analytical research and clinical diagnosis but often require laborious washing steps and large sample or reagent volumes (typically, 100 μL per well). To overcome such drawbacks in the conventional multiwell plate, we present a novel microchannel-connected multiwell plate (μCHAMP) that can be used for automated disease biomarker detection in a small sample volume by performing droplet-based magnetic bead immunoassay inside the plate. In this μCHAMP-based immunoassay platform, small volumes (30-50 μL) of aqueous-phase working droplets are stably confined within each well by the simple microchannel structure (200-300 μm in height and 0.5-1 mm in width), and magnetic beads are exclusively transported into an adjacent droplet through the oil-filled microchannels assisted by a magnet array aligned beneath and controlled by a XY-motorized stage. Using this μCHAMP-based platform, we were able to perform parallel detection of synthetic amyloid beta (Aβ) oligomers as a model analyte for the early diagnosis of Alzheimer's disease (AD). This platform easily simplified the laborious and consumptive immunoassay procedure by achieving automated parallel immunoassay (32 assays per operation in 3-well connected 96-well plate) within 1 hour and at low sample consumption (less than 10 μL per assay) with no cumbersome manual washing step. Moreover, it could detect synthetic Aβ oligomers even below 10 pg mL(-1) concentration with a calculated detection limit of ∼3 pg mL(-1). Therefore, the μCHAMP and droplet-based magnetic bead immunoassay, with the combination of XY-motorized magnet array, would be a useful platform in the diagnosis of human disease, including AD, which requires low consumption of the patient's body fluid sample and automation of the entire immunoassay procedure for high processing capacity.

Sample introduction interface for on-chip nucleic acid-based analysis of Helicobacter pylori from stool samples

Despite recent advances in microfluidic-based integrated diagnostic systems, the sample introduction interface, especially with regards to large volume samples, has often been neglected. We present a sample introduction interface that allows direct on-chip processing of crude stool samples for the detection of Helicobacter pylori (H. pylori). The principle of IFAST (immiscible filtration assisted by surface tension) was adapted to include a large volume sample chamber with a septum-based interface for stool sample introduction. Solid chaotropic salt and dry superparamagnetic particles (PMPs) could be stored on-chip and reconstituted upon sample addition, simplifying the process of release of DNA from H. pylori cells and its binding to the PMPs. Finally, the PMPs were pulled via a magnet through a washing chamber containing an immiscible oil solution and into an elution chamber where the DNA was released into aqueous media for subsequent analysis. The entire process required only 7 min while enabling a 40-fold reduction in working volume from crude biological samples. The combination of a real-world interface and rapid DNA extraction offers the potential for the methodology to be used in point-of-care (POC) devices.

Droplet Manipulation Using Acoustic Streaming Induced by a Vibrating Membrane

We present a simple method for on-demand manipulation of aqueous droplets in oil. With numerical simulations and experiments, we show that a vibrating membrane can produce acoustic streaming. By making use of this vortical flow, we manage to repulse the droplets away from the membrane edges. Then, by simply aligning the membrane at 45° to the flow, the droplets can be forced to follow the membrane's boundaries, thus steering them across streamlines and even between different oil types. We also characterize the repulsion and steering effect with various excitation voltages at different water and oil flow rates. The maximum steering frequency we have achieved is 165 Hz. The system is extremely robust and reliable: the same membrane can be reused after many days and with different oils and/or surfactants at the same operating frequency.

Centrifugal LabTube platform for fully automated DNA purification and LAMP amplification based on an integrated, low-cost heating system

This paper introduces a disposable battery-driven heating system for loop-mediated isothermal DNA amplification (LAMP) inside a centrifugally-driven DNA purification platform (LabTube). We demonstrate LabTube-based fully automated DNA purification of as low as 100 cell-equivalents of verotoxin-producing Escherichia coli (VTEC) in water, milk and apple juice in a laboratory centrifuge, followed by integrated and automated LAMP amplification with a reduction of hands-on time from 45 to 1 min. The heating system consists of two parallel SMD thick film resistors and a NTC as heating and temperature sensing elements. They are driven by a 3 V battery and controlled by a microcontroller. The LAMP reagents are stored in the elution chamber and the amplification starts immediately after the eluate is purged into the chamber. The LabTube, including a microcontroller-based heating system, demonstrates contamination-free and automated sample-to-answer nucleic acid testing within a laboratory centrifuge. The heating system can be easily parallelized within one LabTube and it is deployable for a variety of heating and electrical applications.

Novel droplet platforms for the detection of disease biomarkers

Personalized medicine - healthcare based on individual genetic variation - has the potential to transform the way healthcare is delivered to patients. The promise of personalized medicine has been predicated on the predictive and diagnostic power of genomic and proteomic biomarkers. Biomarker screening may help improve health outcomes, for example, by identifying individuals' susceptibility to diseases and predicting how patients will respond to drugs. Microfluidic droplet technology offers an exciting opportunity to revolutionize the accessibility of personalized medicine. A framework for the role of droplet microfluidics in biomarker detection can be based on two main themes. Emulsion-based microdroplet platforms can provide new ways to measure and detect biomolecules. In addition, microdroplet platforms facilitate high-throughput screening of biomarkers. Meanwhile, surface-based droplet platforms provide an opportunity to develop miniaturized diagnostic systems. These platforms may function as portable benchtop environments that dramatically shorten the transition of a benchtop assay into a point-of-care format.

A droplet microfluidic approach to single-stream nucleic acid isolation and mutation detection

In this work, a droplet microfluidic platform for genetic mutation detection from crude biosample is described. Single-stream integration of nucleic acid isolation and amplification is realized on a simple fluidic cartridge. Subsequent DNA melting curve is employed with signal normalizing algorithm to differentiate heterozygous K-ras codon 12 c.25G>A mutant from the wildtype. This technique showcases an alternative to modular bench-top approaches for genetic mutation screening, which is of interest to decentralized diagnostic platforms.

Magnetic droplet manipulation platforms for nucleic acid detection at the point of care

This review summarizes recent developments in the use of magnetically actuated droplets in point-of-care molecular diagnostic platforms. We discuss the fundamentals of magnetic droplet manipulation and the various modes of actuation. The balance of forces acting on a droplet during transport and particle extraction, as well as the devices and instrumentation developed to perform these operations will be presented and discussed. Furthermore, we review some of the recent advances on the diagnostic applications of platforms utilizing magnetic manipulation for genetic assessment of biological samples.

Phaseguide assisted liquid lamination for magnetic particle-based assays

We have developed a magnetic particle-based assay platform in which functionalised magnetic particles are transferred sequentially through laminated volumes of reagents and washing buffers. Lamination of aqueous liquids is achieved via the use of phaseguide technology; microstructures that control the advancing air-liquid interface of solutions as they enter a microfluidic chamber. This allows manual filling of the device, eliminating the need for external pumping systems, and preparation of the system requires only a few minutes. Here, we apply the platform to two on-chip strategies: (i) a one-step streptavidin-biotin binding assay, and (ii) a two-step C-reactive protein immunoassay. With these, we demonstrate how condensing multiple reaction and washing processes into a single step significantly reduces procedural times, with both assay procedures requiring less than 8 seconds.

Integrated lab-on-chip biosensing systems based on magnetic particle actuation--a comprehensive review

The demand for easy to use and cost effective medical technologies inspires scientists to develop innovative lab-on-chip technologies for point-of-care in vitro diagnostic testing. To fulfill medical needs, the tests should be rapid, sensitive, quantitative, and miniaturizable, and need to integrate all steps from sample-in to result-out. Here, we review the use of magnetic particles actuated by magnetic fields to perform the different process steps that are required for integrated lab-on-chip diagnostic assays. We discuss the use of magnetic particles to mix fluids, to capture specific analytes, to concentrate analytes, to transfer analytes from one solution to another, to label analytes, to perform stringency and washing steps, and to probe biophysical properties of the analytes, distinguishing methodologies with fluid flow and without fluid flow (stationary microfluidics). Our review focuses on efforts to combine and integrate different magnetically actuated assay steps, with the vision that it will become possible in the future to realize integrated lab-on-chip biosensing assays in which all assay process steps are controlled and optimized by magnetic forces.

Droplet Array Platform for High-Resolution Melt Analysis of DNA Methylation Density

High-resolution melting (HRM) has garnered significant interest as an analytical technique for a number of applications, including DNA methylation detection, due to its inherent sensitivity and robustness. In this study, we describe a miniaturized assay platform for quantitative methylation density analysis using a microfluidic droplet array cartridge. We demonstrate that the DNA methylation level of the RASSF1A promoter can be directly analyzed using HRM. PCR products were generated by amplifying bisulfite-treated DNA with varying CpG densities using CpG island-flanking primer sets. Subsequent HRM analysis on the miniaturized droplet platform shows distinct melting curve profiles associated with methylation levels, which was verified using a conventional benchtop PCR-HRM system. The characteristic melting temperature (Tm) of the PCR products was used to directly quantify the respective levels of DNA methylation density. Our approach provides a key advantage over current gold standard methods such as methylation-specific PCR (MSP), which are incapable of providing specific information regarding the overall methylation density of the target genes. The miniaturized platform establishes a practical approach to methylation density profiling from multiple DNA samples with a potential application in point-of-care diagnostics.