Marc Porter – Director, Nano Institute of Utah
Detection of the Tuberculosis Antigenic Marker Lipoarabinomannan in Infected Patient Sera by Gold Nanoparticle Labeling and Surface-enhanced Raman Scattering
Alexis C. Crawford,1,3 Lars B. Laurentius,3 Timothy S. Mulvihill,1 Jennifer H. Granger,3 John S. Spencer,4 Delphi Chatterjee,4 Kimberly E. Hanson,5 and Marc D. Porter1,2,3*
1Departments of Chemistry, 2Chemical Enginering, 2Bioengineering and 2Pathology and the 3Nano Institute of Utah, University of Utah, Salt Lake City, UT 84112, USA. 4Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523, USA. 5Departments of Medicine and Pathology, University of Utah School of Medicine, Salt Lake City, UT, 84112, USA.
Diagnostic tests for tuberculosis (TB) are critical for patient care and global infection control. This presentation describes the development and preliminary validation through TB-patient serum testing of a heterogeneous immunoassay that is based on surface-enhanced Raman scattering (SERS) for the low-level detection of lipoarabinomannan (LAM), a lipoglycan unique to mycobacteria that is a major virulence factor in the infectious pathology of TB and has been found in the serum, sputum, and urine of infected patients. We detail herein that an assay platform based on gold nanoparticle labels, monoclonal antibodies, and SERS, when combined with a simple serum pretreatment procedure to disrupt immunocomplexes, enables the measurement of LAM in patient sera effectively. To this end, we have carried out a preliminary assessment of the accuracy of this approach using sera from 24 TB-positive patients (culture-confirmed) and 10 healthy controls. LAM was measurable in 21 of the 24 TB-positive specimens, but it was not detectable in any of the controls. These results not only provide much needed evidence of the clinical utility of LAM as a TB biomarker, but also demonstrate the potential strengths of this approach as a new diagnostic test for this disease. Prospects and challenges to the extension of this approach for use in clinics and other point-of-care settings, along with possible applications to other TB markers and other types of patient specimens, are briefly examined and discussed.