Squaric Ester-Based, pH-Degradable Nanogels: Modular Nanocarriers for Safe, Systemic Administration of Toll-like Receptor 7/8 Agonistic Immune Modulators

Anne Huppertsberg, Leonard Kaps, Zifu Zhong, Sascha Schmitt, Judith Stickdorn, Kim Deswarte, Francis Combes, Christian Czysch, Jana De Vrieze, Sabah Kasmi, Niklas Choteschovsky, Adrian Klefenz, Carolina Medina-Montano, Pia Winterwerber, Chaojian Chen, Matthias Bros, Stefan Lienenklaus, Niek N. Sanders, Kaloian Koynov, Detlef SchuppanBart N. Lambrecht, Sunil A. David, Bruno G. De Geest, Lutz Nuhn*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

38 Citations (Scopus)
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Abstract

Small-molecular Toll-like receptor 7/8 (TLR7/8) agonists hold promise as immune modulators for a variety of immune therapeutic purposes including cancer therapy or vaccination. However, due to their rapid systemic distribution causing difficult-to-control inflammatory off-target effects, their application is still problematic, in particular systemically. To address this problem, we designed and robustly fabricated pH-responsive nanogels serving as versatile immunodrug nanocarriers for safe delivery of TLR7/8-stimulating imidazoquinolines after intravenous administration. To this aim, a primary amine-reactive methacrylamide monomer bearing a pendant squaric ester amide is introduced, which is polymerized under controlled RAFT polymerization conditions. Corresponding PEG-derived squaric ester amide block copolymers self-assemble into precursor micelles in polar protic solvents. Their cores are amine-reactive and can sequentially be transformed by acid-sensitive cross-linkers, dyes, and imidazoquinolines. Remaining squaric ester amides are hydrophilized affording fully hydrophilic nanogels with profound stability in human plasma but stimuli-responsive degradation upon exposure to endolysosomal pH conditions. The immunomodulatory behavior of the imidazoquinolines alone or conjugated to the nanogels was demonstrated by macrophages in vitro. In vivo, however, we observed a remarkable impact of the nanogel: After intravenous injection, a spatially controlled immunostimulatory activity was evident in the spleen, whereas systemic off-target inflammatory responses triggered by the small-molecular imidazoquinoline analogue were absent. These findings underline the potential of squaric ester-based, pH-degradable nanogels as a promising platform to permit intravenous administration routes of small-molecular TLR7/8 agonists and, thus, the opportunity to explore their adjuvant potency for systemic vaccination or cancer immunotherapy purposes.

Original languageEnglish
Pages (from-to)9872-9883
Number of pages12
JournalJournal of the American Chemical Society
Volume143
Issue number26
DOIs
Publication statusPublished - 24 Jun 2021

Bibliographical note

Funding Information:
A.H. and L.N. acknowledge support by the Max Planck Graduate Center with the Johannes Gutenberg-Universität Mainz (MPGC). Moreover, L.N. kindly acknowledges financial support by the DFG through the Emmy Noether program as well as the SFB 1066 projects Q02, B03, and B04. Both A.H. and L.N. would also like to thank Tanja Weil for providing access to excellent laboratory facilities.

Publisher Copyright:
© 2021 The Authors. Published by American Chemical Society.

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