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Proceedings Paper

Optoacoustic sensing of ocular bacterial antigen using targeted gold nanorods
Author(s): Saher Maswadi; Leland Page; Lee Woodward; Randolph D. Glickman; Norman Barsalou
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Paper Abstract

Bacterial contamination can be detected using a minimally invasive optical method, based on laser-induced optoacoustic spectroscopy, to probe for specific antigens associated with a specific infectious agent. As a model system, we have used a surface antigen (Ag), isolated from Chlamydia trachomatis, and a complementary antibody (Ab). A preparation of 0.2 mg/ml of monoclonal Ab specific to the C. trachomatis surface Ag was conjugated to gold nanorods using standard commercial reagents, in order to produce a targeted contrast agent with a strong optoacoustic signal. The C. trachomatis Ag was absorbed in standard plastic microwells, and the binding of the complementary Ab-nanorod conjugate was tested in an immunoaffinity assay. Optoacoustic signals were elicited from the bound nanorods, using an optical parametric oscillator (OPO) laser system as the optical pump. The wavelength tuneability of the OPO optimized the spectroscopic measurement by exciting the nanorods at their optical absorption maxima. Optoacoustic responses were measured in the microwells using a probe beam deflection technique. Immunoaffinity assays were performed on several dilutions of purified C. trachomatis antigen ranging from 50 μg/ml to 1 pg/ml, in order to determine the detection limit for the optoacoustic-based assay. Only when the antigen was present, and the complementary Ab-NR reagent was introduced into the microwell, was an enhanced optoacoustic signal obtained, which indicated specific binding of the Ab-NR complex. The limit of detection with the current system design is between 1 and 5 pg/ml of bacterial Ag.

Paper Details

Date Published: 28 February 2008
PDF: 8 pages
Proc. SPIE 6856, Photons Plus Ultrasound: Imaging and Sensing 2008: The Ninth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics, 685615 (28 February 2008); doi: 10.1117/12.766512
Show Author Affiliations
Saher Maswadi, Univ. of Texas Health Science Ctr. (United States)
Leland Page, Univ. of Texas Health Science Ctr. (United States)
Lee Woodward, Univ. of Texas Health Science Ctr. (United States)
Randolph D. Glickman, Univ. of Texas Health Science Ctr. (United States)
Norman Barsalou, Naval Health Research Ctr. Detachment (United States)


Published in SPIE Proceedings Vol. 6856:
Photons Plus Ultrasound: Imaging and Sensing 2008: The Ninth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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