Integrated electrokinetically driven microfluidic devices with pH-mediated solid-phase extraction coupled to microchip electrophoresis for preterm birth biomarkers

3D printed microfluidic devices for integrated solid-phase extraction and microchip electrophoresis of preterm birth biomarkers

BACKGROUND

Preterm birth (PTB) is a leading cause of neonatal mortality, such that the need for a rapid and accurate assessment for PTB risk is critical. Here, we developed a 3D printed microfluidic system that integrated solid-phase extraction (SPE) and microchip electrophoresis (μCE) of PTB biomarkers, enabling the combination of biomarker enrichment and labeling with μCE separation and fluorescence detection.

RESULTS

Reversed-phase SPE monoliths were photopolymerized in 3D printed devices. Microvalves in the device directed sample between the SPE monolith and the injection cross-channel in the serpentine μCE channel. Successful on-chip preconcentration, labeling and μCE separation of four PTB-related polypeptides were demonstrated in these integrated microfluidic devices. We further show the ability of these devices to handle complex sample matrices through the successful analysis of labeled PTB biomarkers spiked into maternal blood serum. The detection limit was 7 nM for the PTB biomarker, corticotropin releasing factor, in 3D printed SPE-μCE integrated devices.

SIGNIFICANCE

This work represents the first successful demonstration of integration of SPE and μCE separation of disease-linked biomarkers in 3D printed microfluidic devices. These studies open up promising possibilities for rapid bioanalysis of medically relevant analytes.

Analysis of thrombin-antithrombin complex formation using microchip electrophoresis and mass spectrometry

Preterm birth (PTB) related health problems take over one million lives each year, and currently, no clinical analysis is available to determine if a fetus is at risk for PTB. Here, we describe the preparation of a key PTB risk biomarker, thrombin-antithrombin (TAT), and characterize it using dot blots, MS, and microchip electrophoresis (µCE). The pH for fluorescently labeling TAT was also optimized using spectrofluorometry and spectrophotometry. The LOD of TAT was measured in µCE. Lastly, TAT was combined with six other PTB risk biomarkers and separated in µCE. The ability to make and characterize TAT is an important step toward the development of an integrated microfluidic diagnostic for PTB risk.

Device Fabrication and Fluorescent Labeling of Preterm Birth Biomarkers for Microchip Electrophoresis

An unmet need exists for a clinical diagnostic to determine preterm birth (PTB) risk. Such an assessment is possible with high sensitivity and specificity using a panel of nine biomarkers. An integrated microfluidic analysis system for these biomarkers is being developed which includes microchip electrophoresis (μCE) separation. A t-shaped microchip device can be used to test the μCE portion of this integrated system to find appropriate separation conditions. These t-shaped microchips can be fabricated using photolithographically patterned Si templates and hot embossing. PTB biomarkers can be fluorescently labeled using an amine-reactive dye prior to μCE. The μCE conditions established using this t-shaped device should be useful in developing a complete integrated microfluidic system for PTB risk assessment.

Rapid quantification of aloin A and B in aloe plants and aloe-containing beverages, and pharmaceutical preparations by microchip capillary electrophoresis with laser induced fluorescence detection

A microchip capillary electrophoresis coupled with laser induced fluorescence detection method for the fast determination of aloin was developed and comprehensively applied for the quantification of aloin A and B present in seven aloe plant species, 42 aloin-containing crude drugs, ten aloe pharmaceutical preparations, and four aloe gel-containing functional foods. The excitation and emission wavelengths for detection of both aloins were set at 473 and 520 nm, respectively. Sample analysis on a 35 mm length of glass microchip channel was completed within 40 s. An interference study indicated that the other main anthraquinones present in the samples did not interrupt with the target aloins detection, demonstrating the good selectivity of this method. It is demonstrated that this method is fast, facile, and specific for determination of aloin A and B from matrix samples which can be applied to the quality control of a wide varieties of aloe species and aloe-derived products.

A decade of microchip electrophoresis for clinical diagnostics - A review of 2008-2017

A core element in clinical diagnostics is the data interpretation obtained through the analysis of patient samples. To obtain relevant and reliable information, a methodological approach of sample preparation, separation, and detection is required. Traditionally, these steps are performed independently and stepwise. Microchip capillary electrophoresis (MCE) can provide rapid and high-resolution separation with the capability to integrate a streamlined and complete diagnostic workflow suitable for the point-of-care setting. Whilst standard clinical diagnostics methods normally require hours to days to retrieve specific patient data, MCE can reduce the time to minutes, hastening the delivery of treatment options for the patients. This review covers the advances in MCE for disease detection from 2008 to 2017. Miniaturised diagnostic approaches that required an electrophoretic separation step prior to the detection of the biological samples are reviewed. In the two main sections, the discussion is focused on the technical set-up used to suit MCE for disease detection and on the strategies that have been applied to study various diseases. Throughout these discussions MCE is compared to other techniques to create context of the potential and challenges of MCE. A comprehensive table categorised based on the studied disease using MCE is provided. We also comment on future challenges that remain to be addressed.

Advancement of analytical modes in a multichannel, microfluidic droplet-based sample chopper employing phase-locked detection

In this work, we expand upon our recently developed droplet-based sample chopping concepts by introducing a multiplexed fluidic micro-chopper device (μChopper). Six aqueous input channels were integrated with a single oil input, and each of these seven channels was controlled by a pneumatic valve for automated sampling through software control. This improved design, while maintaining high precision in valve-based droplet generation at bandwidths of 0.03 to 0.05 Hz, enabled a variety of analytical modes to be employed on-chip compared to previous devices limited to sample/reference alternations. The device was analytically validated for real-time, continuous calibration with a single sample and five standards; multiplexed analysis during calibration using a mixed mode; and standard addition through spiking of six sample droplets with varying amounts of standard. Finally, the standard addition mode was applied to protein quantification in human serum samples using on-chip, homogeneous fluorescence immunoassays. Ultimately, with only ~1.2 μL of total analyzed solution volume- representing 100-fold and 75-fold reductions in reagent and serum volumes, respectively-we were able to generate full, six-point standard addition curves in only 1.5 min, and results correlated well with those from standard plate-reader equipment. This work thus exploited microfluidic valves for both their automation and droplet phase-locking capabilities, resulting in a micro-analytical tool capable of complex analytical interrogation modes on sub-microliter sample volumes while also leveraging drastic noise rejection via lock-in detection. The multichannel μChopper device should prove particularly useful in analyzing precious biological samples or for dynamic analyses at small volume scales.

Microchip electrophoresis separation of a panel of preterm birth biomarkers

Preterm birth (PTB) is responsible for over one million infant deaths annually worldwide. Often, the first and only indication of PTB risk is the onset of early labor. Thus, there is an urgent need for an early PTB risk diagnostic that is inexpensive, reliable, and robust. Here, we describe the development of a microchip electrophoresis (μCE) method for separating a mixture of six PTB protein and peptide biomarkers present in maternal blood serum. μCE devices were photografted with a poly(ethylene glycol) diacrylate surface coating to regulate EOF and reduce nonspecific analyte adsorption. Separation conditions including buffer pH, buffer concentration, and applied electric field were varied to improve biomarker peak resolution while minimizing deleterious effects like Joule heating. In this way, it was possible to separate six PTB biomarkers, the first μCE separation of this biomarker panel. LODs were also measured for each of the six PTB biomarkers. In the future, this μCE separation can be integrated with upstream maternal blood serum sample preparation steps to yield a complete PTB risk diagnosis microdevice.

Automated microfluidic devices integrating solid-phase extraction, fluorescent labeling, and microchip electrophoresis for preterm birth biomarker analysis

We have developed multichannel integrated microfluidic devices for automated preconcentration, labeling, purification, and separation of preterm birth (PTB) biomarkers. We fabricated multilayer poly(dimethylsiloxane)-cyclic olefin copolymer (PDMS-COC) devices that perform solid-phase extraction (SPE) and microchip electrophoresis (μCE) for automated PTB biomarker analysis. The PDMS control layer had a peristaltic pump and pneumatic valves for flow control, while the PDMS fluidic layer had five input reservoirs connected to microchannels and a μCE system. The COC layers had a reversed-phase octyl methacrylate porous polymer monolith for SPE and fluorescent labeling of PTB biomarkers. We determined μCE conditions for two PTB biomarkers, ferritin (Fer) and corticotropin-releasing factor (CRF). We used these integrated microfluidic devices to preconcentrate and purify off-chip-labeled Fer and CRF in an automated fashion. Finally, we performed a fully automated on-chip analysis of unlabeled PTB biomarkers, involving SPE, labeling, and μCE separation with 1 h total analysis time. These integrated systems have strong potential to be combined with upstream immunoaffinity extraction, offering a compact sample-to-answer biomarker analysis platform. Graphical abstract Pressure-actuated integrated microfluidic devices have been developed for automated solid-phase extraction, fluorescent labeling, and microchip electrophoresis of preterm birth biomarkers.

Electrokinetically operated microfluidic devices for integrated immunoaffinity monolith extraction and electrophoretic separation of preterm birth biomarkers

Biomarkers are often present in complex biological fluids like blood, requiring multiple, slow sample preparation steps that pose limitations in simplifying analysis. Here we report integrated immunoaffinity extraction and separation devices for analysis of preterm birth biomarkers in a human blood serum matrix. A reactive polymer monolith was used for immobilization of antibodies for selective extraction of target preterm birth biomarkers. Microfluidic immunoaffinity extraction protocols were optimized and then integrated with microchip electrophoresis for separation. Using these integrated devices, a ∼30 min analysis was carried out on low nanomolar concentrations of two preterm birth biomarkers spiked in a human serum matrix. This work is a promising step towards the development of an automated, integrated platform for determination of preterm birth risk.

Protein separation under a microfluidic regime

Lab-on-a-Chip (LoC), or micro-Total Analysis Systems (μTAS), is recognized as a powerful analytical technology with high capabilities, though end-user products for protein purification are still far from being available on the market. Remarkable progress has been achieved in the separation of nucleic acids and proteins using electrophoretic microfluidic devices, while pintsize devices have been developed for protein isolation according to miniaturized chromatography principles (size, charge, affinity, etc.). In this work, we review the latest advances in the fabrication of components, detection methods and commercial implementation for the separation of biological macromolecules based on microfluidic systems, with some critical remarks on the perspectives of their future development towards standardized microfluidic systems and protocols. An outlook on the current needs and future applications is also presented.

Recent advances in microfluidic sample preparation and separation techniques for molecular biomarker analysis: A critical review

Microfluidics is a vibrant and expanding field that has the potential for solving many analytical challenges. Microfluidics show promise to provide rapid, inexpensive, efficient, and portable diagnostic solutions that can be used in resource-limited settings. Researchers have recently reported various microfluidic platforms for biomarker analysis applications. Sample preparation processes like purification, preconcentration and labeling have been characterized on-chip. Additionally, improvements in microfluidic separation techniques have been reported for molecular biomarkers. This review critically evaluates microfluidic sample preparation platforms and separation methods for biomarker analysis reported in the last two years. Key advances in device operation and ability to process different sample matrices in a variety of device materials are highlighted. Finally, current needs and potential future directions for microfluidic device development to realize its full diagnostic potential are discussed.