PROCEEDINGS ARTICLE | February 25, 2009
Proc. SPIE. 7177, Photons Plus Ultrasound: Imaging and Sensing 2009
KEYWORDS: Target detection, Gold, Sensors, Transducers, Pathogens, Signal generators, Acoustics, Laser beam diagnostics, Signal detection, Nanorods
We demonstrated the ability to detect surface antigens, associated with pathogens, utilizing laser optoacoustic
spectroscopy with antibody-coupled gold nanorods (GNR) as a contrast agent specifically targeted to the antigen of
interest. The sensitivity of the technique has been assessed by determining the minimum detectable concentration of a
surface antigen from biological samples. We compared the sensitivity and applicability of two different methods for
detecting optoacoustic responses, using either optical or piezoelectric sensors. Biological samples were adsorbed to the
inside walls of detachable, flat-bottomed plastic micro-wells, and then probed with appropriate antibodies conjugated
with gold nanorods. If the target antigens were present, the antibody-nanoparticle conjugates were bound, while any
nonadsorbed nanoparticles were washed out of the wells. Optoacoustic signals were generated from the bound nanorods
using a pulsed pump laser at wavelengths corresponding to one of the peak absorptions of the nanorods. Optoacoustic
responses were obtained from the samples using both detection modalities. The sensitivity, suitability, ease of use of
each method were assessed and compared. Initial results indicate that optical detection gives comparable sensitivity as
the piezoelectric method, and further enhancement of the detection sensitivity is possible for both methods. An
advantage of the piezoelectric detection method is that it may be implemented in a more compact assembly, compared to
the optical method, however, the optical method may be less sensitive to external electromagnetic and acoustic noise.
Further evaluation will be required to refine these measurements. The results with both methods indicate that the use of
antibody-targeted nanorod contrast agents, with laser-optoacoustic detection, is a promising technology for the
development of rapid in vitro diagnostic tests.
