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Updated: Jun 3, 2026

Preparation of Neutrally-charged, pH-responsive Polymeric Nanoparticles for Cytosolic siRNA Delivery
Published on: May 2, 2019
Enhanced stability and knockdown efficiency of poly(ethylene glycol)-b-polyphosphoramidate/siRNA micellar
Masataka Nakanishi1, Rajesh Patil1, Yong Ren1
1Department of Materials Science and Engineering Johns Hopkins University Baltimore, Maryland 21218, USA Translational Tissue Engineering Center, Johns Hopkins University Baltimore, Maryland 21218, USA Department of Biomedical Engineering, Johns Hopkins University Baltimore, Maryland 21218, USA Department of Neuroscience, Johns Hopkins University Baltimore, Maryland 21218, USA Whitaker Biomedical Engineering Institute, Johns Hopkins University Baltimore, Maryland 21218, USA 101E Maryland Hall, 3400 North Charles Street Baltimore, Maryland 21218, USA.
Purpose:
Polyelectrolyte complex nanoparticles are a promising vehicle for siRNA delivery but suffer from low stability under physiological conditions. An effective stabilization method is essential for the success of polycationic nanoparticle-mediated siRNA delivery. In this study, sodium triphosphate (TPP), an ionic crosslinking agent, is used to stabilize siRNA-containing nanoparticles by co-condensation.
Methods:
siRNA and TPP were co-encapsulated into a block copolymer, poly(ethylene glycol)-b-polyphosphoramidate (PEG-b-PPA), to form ternary nanoparticles. Physicochemical characterization was performed by dynamic light scattering and gel electrophoresis. Gene silencing efficiency in cell lines was assessed by dual luciferase assay system.
Results:
The PEG-b-PPA/siRNA/TPP ternary nanoparticles exhibited high uniformity with smaller size (80-100 nm) compared with PEG-b-PPA/siRNA nanoparticles and showed increased stability in physiological ionic strength and serum-containing medium, due to the stabilization effect from ionic crosslinks between negatively charged TPP and cationic PPA segment. Transfection and gene silencing efficiency of the TPP-crosslinked nanoparticles were markedly improved over PEG-b-PPA/siRNA complexes in serum-containing medium. No significant difference in cell viability was observed between nanoparticles prepared with and without TPP co-condensation.
Conclusions:
These results demonstrated the effectiveness of TPP co-condensation in compacting polycation/siRNA nanoparticles, improving nanoparticle stability and enhancing the transfection and knockdown efficiency in serum-containing medium.
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