Integration of hydrogels into microfluidic devices with porous membranes as scaffolds enables their drying and reconstitution

A Fully Integrated Microfluidic Device with Immobilized Dyes for Simultaneous Detection of Cell-Free DNA and Histones from Plasma Using Dehydrated Agarose Gates

Sepsis, a life-threatening condition resulting from a failing host response to infection, causes millions of deaths annually, necessitating rapid and simple prognostic assessments. A variety of genomic and proteomic biomarkers have been developed for sepsis. For example, it has been shown that the level of plasma cell-free DNA (cfDNA) and circulating histones increases considerably during sepsis, and they are linked with sepsis severity and mortality. Developing a diagnostic tool that is capable of assessing such diverse biomarkers is challenging as the detection methodology is quite different for each. Here, a fully integrated microfluidic device capable of detecting a genomic biomarker (cfDNA) and a proteomic biomarker (total circulating histones) using a common detection platform has been demonstrated. The microfluidic device utilizes dehydrated agarose gates loaded with pH-specific agarose to electrophoretically trap cfDNA and histones at their respective isoelectric points. It also incorporates fluorescent dyes within the device, eliminating the need for off-chip sample preparation and allowing the direct testing of plasma samples without the need for labeling DNA and histones with fluorescent dyes beforehand. Xurography, which is a low-cost and rapid method for fabrication of microfluidics, is used in all the fabrication steps. Experimental results demonstrate the effective accumulation and separation of cfDNA and histones in the agarose gates in a total processing time of 20 min, employing 10 and 30 Volts for cfDNA and histone accumulation and detection, respectively. The device can potentially be used to distinguish between the survivors and non-survivors of sepsis. The integration of the detection of both biomarkers into a single device and dye immobilization enhances its clinical utility for rapid point-of-care assessment of sepsis prognosis.

Isoelectric trapping and discrimination of histones from plasma in a microfluidic device using dehydrated isoelectric gate

Histones are basic proteins with an isoelectric point around 11. It has been shown that the level of plasma circulating histones increases significantly during sepsis, and circulating free histones are associated with sepsis severity and mortality. It was found that the median plasma total free histone concentration of sepsis ICU non-survivors is higher compared to survivors. Therefore, histone concentration can serve as a prognostic indicator and there is a need for a simple, low-cost, and rapid method for measuring histone levels. In this work, we have developed a microfluidic device containing an isoelectric membrane made of dehydrated agarose gel of a specific pH embedded in a porous membrane for isoelectric trapping of histones rapidly. Although isoelectric gates have been used for trapping proteins before, they have to be introduced at the time of the experiment. Here, we show that isoelectric gates formed by gels loaded in a scaffold can be integrated directly into the fabrication process flow, dehydrated for storage, and rehydrated during the experiment and still function effectively to achieve isoelectric trapping. A low-cost and rapid microfabrication technique, xurography, was used for agarose integration and device fabrication. The integrated device was tested with samples containing buffered histone, histone in the presence of high-concentration bovine serum albumin (BSA), and histone spiked in blood plasma. The results show that the device can be used to distinguish between survivors and non-survivors of sepsis in less than 10 min, making it suitable as a point-of-care device for sepsis prognosis.