Before Ebola, there was malaria. In recent months, the deadly Ebola virus has ravished West Africa, claiming more than 8400 lives to date. The much more ubiquitous malaria parasite has claimed even more victims: In 2013, an estimated 584 000 people—many of them children in Africa under age 5—died from malaria-related symptoms.
One key to reducing these troubling numbers is early and accurate detection. Sophisticated bench-top diagnostic instruments can do the job. However, that approach requires expensive equipment (usually microscopes) and sufficient numbers of trained technicians.
One promising alternative is a new, user-friendly class of technologies known as rapid diagnostic test kits (RDTs). Basically, RDTs are portable devices that contain immobilized malaria antibodies—the proteins produced by the immune system that bind to and neutralize malaria (the antigen) in the bloodstream. Depending on the RDT detection technology, a change in “brightness” or electrical resistance will indicate the binding, and the presence, of the antigen.
But RDTs suffer their own drawbacks. Most systems now in the field are either relatively slow, insensitive to small amounts of the antigen, or return false readings. Now, in a paper published in Advances in Infectious Diseases, three scientists—one based in Ghana and the other two based in Louisiana—present results of an “ultra-low detection” RDT that they claim could theoretically eliminate false readings.
The paper’s lead author, Emmanuel Gikunoo, is a materials science researcher at Ghana’s Kwame Nkrumah University of Science and Technology. His collaborators are Adeyabeba Abera at the HBCU Southern University and A&M College and Eyassu Woldesenbet at Louisiana State University. Abera and Woldesenbet both belong to the National Science Foundation’s Center for Next Generation Composites CREST Center (NextGenC3). Established at Southern, the center has a broad mission to “increase the research and education activities at one of the largest HBCU[s] graduating minority students in the fields of STEM.” (Another HBCU, North Carolina A&T State University, also leads an NSF advanced-materials-research center.)
Underpinning the RDT technology developed by Gikunoo et al. is an emerging class of materials known as carbon nanofibers (see the HBSciU article discussing nano-structured materials). The researchers essentially immobilized millions of individual carbon nanofibers onto microscopic glass balloons (see the scanning electron microscope image below). Following that, they attached the desired antibody (in this study, “IgG”) to the nanofiber-microballoon complex. After attaching the desired antibody, they then coated the surface with a polymer that would block open sites that might bind unwanted antibodies and other proteins, a step intended to reduce false readings.
Thanks to the millions of available binding sites on the microballoon, even minute amounts of test antigen (in this case, “anti-IgG”) could be captured. Indeed, a change in electrical resistance was detected for a sample containing as little as 4 picograms of antigen per 1 milliliter of solution (a picogram is 10-12 grams; 1 milliliter is two-tenths of a teaspoon). Also, their RDT could detect antigen in 1 minute; by contrast, other RDTs reportedly require at least three minutes before a change can be detected.
Furthermore, the researchers experimentally deduced a quantitative relationship between antigen concentration and electrical resistivity; that means their RDT is not just qualitative, merely indicating the presence of antigen, but also quantitative, indicating how much. And that can tell health-care workers the stage that the infection has grown inside the body.
The researchers previously conducted a similar study using a malaria-specific antigen. The results were essentially the same.