Low-resource method for extracting the malarial biomarker histidine-rich protein II to enhance diagnostic test performance.

We have demonstrated the utility of a self-contained extraction device for the selective isolation, purification, and concentration of the malaria diagnostic protein biomarker Plasmodium falciparum histidine-rich protein II (pfHRPII) from human plasma and whole blood. The extraction cassette consists of a small-diameter tube containing a series of preloaded processing solutions separated by mineral oil valves. Nickel(II) nitrilotriacetic acid-functionalized magnetic particles are added to a parasite-spiked sample contained within the loading chamber of the device for capture of pfHRPII. The biomarker-bound magnetic particles are then entrained by an external magnetic field and transported through three wash solutions. Processing removes sample interfering agents, and the biomarker target is concentrated in the final chamber for subsequent analysis. At parasitemias of 200 parasites/μL, purification and concentration of pfHRPII with extraction efficiencies in excess of 70% total protein target are achieved. The concentration of nonspecific protein interfering agents was reduced by more than 2 orders of magnitude in the final extracted sample without the need for hours of processing time and specialized laboratory equipment. We have demonstrated an application of this low-resource technology by coupling extraction and concentration of pfHRPII within the cassette to a commonly employed rapid diagnostic test. Sample preprocessing improved the visual limit of detection of this test by over 8-fold, suggesting that the combination of both low-resource technologies could prove to be useful in malaria eradication efforts.