STV-Based Extraction Devices
One innovation we will pursue is the addition of a processing step to purify and concentrate the biomarkers in samples. By removing interferents and concentrating the target, we predict an increased performance of the existing WHO-qualified RDTs. Multidisciplinary cohorts will develop a cassette device that separates the malaria biomarker protein HRP-II from interferents contained in patient samples (blood or saliva) for use in downstream commercial malaria RDTs. In this device, a biological sample is introduced into the first chamber and mixed with appropriate target magnetic beads (e.g. silica-coated) in a binding buffer (Figure 1). Magnetic beads are entrained by an external magnet and transported through each of the processing solutions. The pre-loaded processing solutions are held in place in the cassette by the surface tension forces of the liquid valves (surface tension valves). Surprisingly, when the beads reach the liquid-air interface of the surface tension valves between the immobilized fluids, they pass through without entraining solution. Entry into the next solution proceeds similarly until the cloud of beads passes through all the processing steps (Figure 2). Processing removes sample interferents, and the target is concentrated in 50μL of water in the final chamber The fundamental benefit is that the cassette system is adaptable to both target and matrix. Relative to other approaches, we anticipate the extraction cassettes will allow efficient target isolation regardless of the skill/experience of the end user, reduce costs, not require laboratory equipment, and demonstrate utility in a variety of field conditions. A cassette device that separates biomarkers (DNA, RNA, protein) interferents contained in patient samples (blood or saliva) could be used in downstream commercial detection (e.g. improving existing RDTs and making nucleotide extraction possible for more robust PCR).