Rapid detection of Mycobacterium tuberculosis biomarkers in a sandwich immunoassay format using a waveguide-based optical biosensor
Authors
Harshini Mukundan ; Sandeep Kumar ; Dominique N. Price ; Sonja M. Ray ; Ye-Jin Lee ; Seonyeong Min ; Seokyong Eum ; Jessica Kubicek-Sutherland ; Jesse M. Resnick ; W. Kevin Grace ; Aaron S. Anderson ; Soo Hee Hwang ; Sang Nae Cho ; Laura E. Via ; Clifton Barry III ; Ramamurthy Sakamuri ; Basil I. Swanson
Early diagnosis of active tuberculosis (TB) remains an elusive challenge, especially in individuals with disseminated TB and HIV co-infection. Recent studies have shown a promise for the direct detection of pathogen-specific biomarkers such as lipoarabinomannan (LAM) for the diagnosis of TB in HIV-positive individuals. Currently, traditional immunoassay platforms that suffer from poor sensitivity and high non-specific interactions are used for the detection of such biomarkers. In this manuscript, we demonstrate the development of sandwich immunoassays for the direct detection of three TB-specific biomarkers, namely LAM, early secretory antigenic target 6 (ESAT6) and antigen 85 complex (Ag85), using a waveguide-based optical biosensor platform. Combining detection within the evanescent field of a planar optical waveguide with functional surfaces that reduce non-specific interactions allows for the ultra-sensitive and quantitative detection of biomarkers (an order of magnitude enhanced sensitivity, as compared to plate-based ELISA) in complex patient samples (urine, serum) within a short time. We also demonstrate the detection of LAM in urine from a small sample of subjects being treated for TB using this approach with excellent sensitivity and 100% corroboration with disease status. These results suggest that pathogen-specific biomarkers can be applied for the rapid and effective diagnosis of disease. It is likely that detection of a combination of biomarkers offers greater reliability of diagnosis, rather than detection of any single pathogen biomarker.