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Updated: Jul 4, 2026
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Microwave-assisted Functionalization of Poly(ethylene glycol) and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation
Published on: October 29, 2013
Amine-reactive pyridylhydrazone-based PEG reagents for pH-reversible PEI polyplex shielding.
Carolin Fella1, Greg F Walker, Manfred Ogris
1Pharmaceutical Biology-Biotechnology, Center for Drug Research, and Center for Nanoscience, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, D-81377 Munich, Germany.
Summary
Reversible PEGylation shields DNA polyplexes, enhancing gene delivery. This pH-cleavable shielding improves cellular uptake and in vivo tumor gene expression, offering a promising tool for nucleic acid delivery.
Area of Science:
- Biomaterials Science
- Nanotechnology
- Gene Therapy
Background:
- Polyethylene glycol (PEG)ylation is crucial for drug and nucleic acid delivery systems.
- Bioreversible PEGylation offers advantages for targeted delivery by releasing the therapeutic agent at the target site.
- Developing pH-sensitive PEGylation reagents is key for endosomal release and enhanced cellular uptake.
Purpose of the Study:
- To synthesize and evaluate novel pH-cleavable PEG-hydrazone-NHS (PEG-HZN-NHS) reagents for bioreversible surface shielding of DNA polyplexes.
- To compare the performance of reversibly shielded polyplexes with stably shielded polyplexes in vitro and in vivo gene delivery.
- To investigate the potential of PEG-HZN-NHS for enhancing tumor-specific gene expression.
Main Methods:
- Synthesis of monofunctional and bifunctional PEG-HZN-NHS reagents.
- Preparation and characterization of polyethylenimine (PEI) polyplexes shielded with PEG-HZN-NHS or stable PEG-NHS.
- Assessment of polyplex stability at physiological (pH 7.4) and endosomal (pH 5) pH using particle size and zeta potential measurements.
- Confirmation of pH-dependent deshielding using fluorescence correlation spectroscopy (FCS).
- In vitro luciferase gene transfection assays in hepatoma cells overexpressing EGF receptors.
- In vivo studies of tumor-specific transgene expression in a mouse xenograft model.
Main Results:
- Successfully synthesized pH-sensitive PEG-HZN-NHS and stable PEG-NHS reagents.
- PEG-HZN-NHS shielded polyplexes demonstrated stability at pH 7.4 but underwent deshielding at endosomal pH 5.
- Reversibly shielded polyplexes showed up to a 16-fold enhancement in gene expression in vitro compared to stably shielded polyplexes.
- In vivo studies confirmed enhanced tumor-specific transgene expression with reversibly shielded polyplexes after intravenous administration.
Conclusions:
- PEG-HZN-NHS enables bioreversible shielding of DNA polyplexes, facilitating endosomal release.
- Reversible PEGylation significantly enhances gene delivery efficiency both in vitro and in vivo.
- This approach holds great promise for improving the efficacy of nucleic acid-based therapeutics and gene therapy applications.
