Time-resolved fluorescence polarization dynamics and optical imaging of Cytate: a prostate cancer receptor-targeted contrast agent.

Cypate-octreote peptide analogue conjugate (Cytate) was investigated as a prostate cancer receptor-targeted contrast agent. The absorption and fluorescence spectra of Cytate were ranged in the near-infrared "tissue optical window." Time-resolved investigation of polarization-dependent fluorescence emitted from Cytate in solution as well as in cancerous and normal prostate tissues was conducted. Polarization preservation characteristics of Cytate in solution and tissues were studied. Fluorescence intensity emitted from the Cytate-stained cancerous prostate tissue was found to be much stronger than that from the Cytate-stained normal prostate tissue, indicating more Cytate uptake in the former tissue type. The polarization anisotropy of Cytate contained in cancerous prostate tissue was found to be larger than that in the normal prostate tissue, indicating a larger degree of polarization preservation in Cytate-stained cancerous tissue. The temporal profiles of fluorescence from Cytate solution and from Cytate-stained prostate tissue were fitted using a time-dependent fluorescence depolarization model. The photoluminescence imaging of Cytate-stained cancerous and normal prostate tissues was accomplished, showing the potential of Cytate as a fluorescence marker for prostate cancer detection.