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Journal of Biomedical Optics

In vitro testing of a protease-sensitive contrast agent for optoacoustic imaging
Author(s): Anthony Green; James R. Norris; Jing Wang; Zhixing Xie; Hao F. Zhang; Patrick J. La Rivière
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Paper Abstract

We have designed a protease-sensitive imaging probe for optoacoustic imaging whose absorption spectrum changes upon cleavage by a protease of interest. The probe comprises an active site, a derivative of chlorophyll or natural photosynthetic bacteriochlorophyll that absorbs in the near infrared, conjugated to a peptide backbone specific to the protease being imaged. The uncleaved molecules tend to aggregate in dimers and trimers, causing a change in the absorption spectrum relative to that of the monomer. Upon cleavage, the probe molecules deaggregate, giving rise to a spectrum characteristic of monomers. We show using photospectrometry that the two forms of the probe have markedly different absorption spectra, which could allow for in vivo optoacoustic identification using a multiwavelength imaging strategy. Optoacoustic measurements using a narrow-band dye laser find spectral peaks in the two forms of the probe at the expected location. The optoacoustic signal from the uncleaved probe is found to be considerably weaker than that of the cleaved probe, perhaps due to poor optical-acoustic coupling in the aggregated molecules. However, ultimately, it is detection of the cleaved probe that is of the greatest import, since it reports on the protease activity of interest.

Paper Details

Date Published: 1 March 2010
PDF: 8 pages
J. Biomed. Opt. 15(2) 021315 doi: 10.1117/1.3365935
Published in: Journal of Biomedical Optics Volume 15, Issue 2
Show Author Affiliations
Anthony Green, The Univ. of Chicago (United States)
James R. Norris, The Univ. of Chicago (United States)
Jing Wang, Univ. of Wisconsin-Milwaukee (United States)
Zhixing Xie, Univ. of Wisconsin-Milwaukee (United States)
Hao F. Zhang, Univ. of Wisconsin-Milwaukee (United States)
Patrick J. La Rivière, The Univ. of Chicago Medical Ctr. (United States)

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