Development of microLIPS (Luciferase Immunoprecipitation Systems): a novel microfluidic assay for rapid serum antibody detection

There is considerable interest in the development of rapid, point-of-care antibody detection for the diagnosis of infectious and auto-immune diseases. In this paper, we present work on the development of a self-contained microfluidic format for the Luciferase Immunoprecipitation Systems (LIPS) assay. Whereas the majority of immunoassays for antigen-specific antibodies employ either bacteria- or yeast-expressed proteins and require the use of secondary antibodies, the LIPS technique uses a fusion protein comprised of a Renilla luciferase reporter and the antigen of interest produced via mammalian cell culture, ensuring the addition of mammalian post-translational modifications. Patient serum is mixed with the fusion protein and passed over immobilized Protein A/G; after washing, the only remaining luciferase-tagged antigens are those retained by specific antibodies. These can be quantitatively measured using chemiluminescence upon the introduction of coelenterazine. The assay has been successfully employed for a wide variety of diseases in a microwell format. We report on a recent demonstration of rapid HSV-2 diagnosis with the LIPS assay in a microfluidic format, using one microliter of serum and obtaining results in under ten minutes. We will also discuss recent progress on two fronts, both aimed at the deployment of this technology in the field: first, simplifying assay operation through the automation of flow control using power-free means; and second, efforts to increase signal levels, primarily through strategies to increase antibody binding capacity, in order to move towards portable battery powered electronics.