Urea-Bond Scission Induced by Therapeutic Ultrasound for Biofunctional Molecule Release
Yunkang Tong, Mingle Li, Haiqiao Huang, Saran Long, Wen Sun, Jianjun Du, Jiangli Fan, Lei Wang, Bin Liu, Xiaojun Peng
Abstract
Ultrasound-triggered remote control of biomolecular functions in cells provides unique advantages for us to interrogate nature. However, strategies to design therapeutic ultrasound-responsive functional molecules remain elusive, and rare ultrasound-cleavable chemical bonds have been developed to date. Herein, therapeutic ultrasound (1 MHz)-induced scission of urea bonds for drug release is demonstrated for the first time. Such a transformation has been verified to be initiated by hydroxyl radicals generated in the interior of cavitation bubbles, occurring specifically at the cavitation bubble-liquid interface. A series of urea-bond-containing prodrugs based on methylene blue (MB), namely MBUs, are designed. Upon sonication with low-intensity therapeutic ultrasound, the urea bonds linked with primary amines can be selectively cleaved, and free MB is released in a physiologically relevant environment, accompanied by recovered absorbance, fluorescence, and photosensitivity. Moreover, an FDA-approved alkylating agent (i.e., melphalan) bearing urea bond is also developed (MBU-Mel), successfully achieving ultrasound-triggered drug release in deep-seated cancer cells (mimic with 1 cm pigskin), showing the scalability of our ultrasound-responsive molecule platform in bioactive molecules release. This may set the starting point for therapeutic ultrasound-induced drug release, making a forward step in "sonopharmacology".