(81d) A POC Technology for Detecting HCV Directly from Untreated Plasma Using Rotational Brownian Motion of Immuno-Janus Particles

Hepatitis C Virus (HCV) infections and associated liver diseases result in nearly 300,000 deaths annually. Recognizing this threat, the World Health Organization has set ambitious 2030 targets to reduce new HCV infections by 90% and related deaths by 65%. Despite the effectiveness of a 12-week antiviral drug regimen in treating HCV, access to effective diagnostic tools remains a major hurdle, particularly in developing countries where a significant portion of the HCV-related deaths take place. In these regions, diagnosis is predicated on an initial point-of-care (POC) antibody test of the patient’s saliva or blood. A positive antibody result necessitates an analysis of viral load using reverse-transcription PCR. While PCR tests and mail-in services are common in developed nations, they are far less accessible in lower-income countries. Consequently, individuals are less likely to pursue follow-up testing, even if initial tests are positive for HCV antibodies. This limitation obstructs comprehensive diagnosis and subsequent treatment for many individuals.

Our laboratory addresses this challenge with the Immuno-Janus Particle (IJP) assay, designed for rapid depletion and quantification of viruses by immunocapture with antibodies on the IJP. The IJPs are micron-sized beads half-coated with a 30 nm layer of gold, undergo discernible Brownian motion with a “blinking” frequency inversely proportional to their diameter cubed. When viruses are captured by the bead, the effective diameter increases and reduces the rotation and blinking frequency. The platform is able to detect as few as 1000 viruses from a 10 μL of untreated plasma from a capillary after a skin prick, which approaches the sensitivity of PCR but without the necessary extraction protocol. The incubation time is less than 30 minutes because of the bulk binding. The IJP’s size-based detection of eliminates the need for isolation, as soluble proteins are too small to create a signal and do not interfere with detection capabilities. An embedded microporous membrane allows the removal of blood cells by passive wetting flow in a lateral-flow chip. Moreover, its compatibility with standard smartphones enhances accessibility, as imaging the blinking beads requires only an inexpensive clip-on lens attached to a phone camera. By integrating our user-friendly MATLAB-based single-particle tracking code into a smartphone app, individuals can obtain the test results directly and transmit them wirelessly for region-wide epidemic control. These features hence render the platform a one-test definitive diagnostic test in the field that can be used in low-resource settings.

We are advancing the technology to a multiplex platform for detecting multiple blood-borne viruses in low-income countries, such as HIV, HBV and syphilis, with quantum dot labeling of the captured viruses. With labeling, magnetic IJPs will be used to enable an additional wash step to remove unbound quantum dots. A passive lateral flow design with a second wash flow will be tested.