Poster Presentation 11th Annual Conference of the International Chemical Biology Society 2022

Design and Synthetic Investigations toward pH-Sensitive Dual-Release Molecular Frameworks (#178)

Dan Zhao 1 , Trang Pham 1 , Yayao Zhou 1 , Jonathan Baell 1
  1. monash, NORTH MELBOURNE, VIC, Australia

Stimuli-responsive drug delivery systems (DDSs) have been gaining increasing attention due to their specific responsive drug release properties. Among them, pH stimuli-responsive DDS, which takes advantage of the pH differences between healthy (pH 7.4) and cancer tissues (pH 6.5)1, plasma (pH 7.4) and lymph fluid (pH 6.2)2, as well as cytosol (pH 7.2)3 and endosomes (pH 4-5)4, has created a promising platform for the development of the controlled DDSs. This study aims to investigate linker chemistry and enable the incorporation of a multifunctional molecular apparatus that can be assembled within a DDS for selective release of two payloads in an acidic environment. Herein, an effective linker that contains an acyl hydrazone core, a fluorophore (FL), and an azide moiety was designed. The hydrolysis of acyl hydrazone bond was able to release one payload from the linker, then release the second payload via intramolecular cyclisation. Noticeably, two payloads were released at a specific molar ratio of 1:1. The tuneable pH stimuli-responsive properties will be determined by the structural stability of the linker,5 which was further investigated through the variation of different electron-withdrawing and electron-donating groups and additional π-systems on the nitrogen of the acyl hydrazone. Finally, six target linkers have been synthesized and their pH sensitivities were evaluated. Among the six linkers, the acetophenone acyl hydrazone and carbamoyl hydrazone possessed a relatively higher stability at pH 6.5 and a quick release profile at pH 4.5-5.5. In addition, a new phenyl acetone benzenesulfonyl hydrazone linker exhibited a higher tendency to hydrolyse at pH 4.5 than that at pH from 5.5 to 7.4. The acetophenone benzenesulfonyl hydrazone linker was unreactive under any biologically-relevant acidic pH range, but the novel chemistry developed en route is suggested to be modifiable to fine-tune pH sensitivity. In conclusion, a suite of novel, pH-sensitive multifunctionalised linkers that could test future spatial and temporal payload delivery hypotheses in a manner hitherto not possible has been successfully developed.

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