DEVELOPMENT AND INVESTIGATION OF FLUORESCENCE IMAGING PROBES

Abstract

Fluorescence imaging has attracted much attention due to high sensitivity, spatial and temporal resolution, and fast acquisition time, for imaging biomolecular processes and for diagnosis of diseases such as cancer in early stages. Fluorescence imaging in centimeter-deep tissue suffers from low spatial resolution because of the strong scattering of light. On the other hand ultrasound imaging benefits from 1000 times less scattering in the tissue and deep penetration. Ultrasound switchable fluorescence imaging is a relatively new imaging modality that combines the sensitivity of optical imaging with the depth of penetration of ultrasound imaging while preserving the resolution by only eliciting the fluorescence signal from the small focal volume of the high intensity focused ultrasound (HIFU). As such unprecedented depths can be penetrated while resolution and sensitivity of fluorescence imaging are relatively conserved. USF imaging contrast agents directly or indirectly respond to the elevated temperatures caused by HIFU. As such thermo-sensitive USF imaging probes switch “ON” over a narrow range of elevated temperatures instantly. In this work, several different strategies for developing thermo-sensitive probes for potential use in USF imaging are studied a pH-sensitive USF contrast agent developed.