Many individuals living in remote and resource-limited regions around the world face a barrier to adequate medical care due to the unavailability of diagnostic instrumentation to perform standard measurements which diagnose disease and inform treatment. Factors which limit the availability of diagnostics include both the costs of instrumentation and per-test costs, inadequate portability, the requirement for a laboratory facility, the time required to perform the test, and a need for highly-trained personnel to operate the instrumentation. While a wide variety of approaches primarily based on innovations in micro- and nanotechnology have been reported toward the point-of-care sensing of biological entities, none has yet emerged as a comprehensive solution to the fundamental problems of diagnostic testing in resource-limited settings. In strides toward a platform for low-cost, rapid, easy-to-use point-of-care diagnostics, we present an ELISA-inspired lab-on-a-chip strategy for biological detection based on liposome tagging and ion-release impedance spectroscopy. Ion-encapsulating dipalmitoylphosphatidylcholine (DPPC) liposomes can be functionalized with antibodies and are stable in deionized water yet become permeable for ion release upon heating, making them ideal reporters for electrical biosensing of surface-immobilized antigens. We demonstrate the quantification of these liposomes by real-time impedance measurements and the detection of HIV, which we have selected as a problem to target in the development of this platform, which ultimately can be applied more broadly to other biomolecules and antigens. By showing the detection of viruses on this biosensor platform, we have demonstrate a proof-of-concept which will be further optimized and advanced toward quantitative determination of viral load from whole blood specimens.
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A liposome-based ion release impedance sensor for HIV detection at the point-of-care
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