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Near-infrared fluorescence imaging has emerged as a noninvasive, inexpensive, and ionizing-radiation-free monitoring tool for assessing tumor growth and treatment efficacy. In particular, ultrasound switchable fluorescence (USF) imaging has been explored with improved imaging sensitivity and spatial resolution in centimeter-deep tissues. This study achieved the size control of polymer-based and indocyanine green (ICG) encapsulated USF contrast agents, capable of accumulating in the tumor after intravenous injections. These nanoprobes varied in size from 58 to 321 nm. The bioimaging profiles demonstrated that the proposed nanoparticles can efficiently eliminate the background light from normal tissue and show a tumor-specific fluorescence enhancement in the BxPC-3 tumor-bearing mice models possibly via the enhanced permeability and retention effect. In vivo tumor USF imaging further demonstrated that these nanoprobes can effectively be switched “ON” with enhanced fluorescence in response to a focused ultrasound stimulation in the tumor microenvironment, contributing to the high-resolution USF images. Therefore, our findings suggest that ICG-encapsulated nanoparticles are good candidates for USF imaging of tumors in live animals, indicating their great potential in optical tumor imaging in deep tissue.

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Publication history

Received: 13 May 2022
Revised: 13 May 2022
Accepted: 01 August 2022
Published: 21 September 2022

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© Tsinghua University Press 2022

Acknowledgements

Acknowledgements

This work was supported in part by funding from the National Institute of Biomedical Imaging and Bioengineering (No. 1R15EB030809-01), the Research Enhancement Program (No. 270089), and the Cancer Prevention & Research Institute of Texas (Nos. RP170564 and RP210206).

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Email: nanores@tup.tsinghua.edu.cn

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