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Poly(amidoamine) salt form: effect on pH-dependent membrane activity and polymer conformation in solution
Ka-Wai Wan1, Beatrice Malgesini, Ilario Verpilio
1Centre for Polymer Therapeutics, Welsh School of Pharmacy, King Edward VII Avenue, Cardiff CF10 3XF, United Kingdom.
Biomacromolecules
|May 11, 2004
Summary
The counterion significantly impacts poly(amidoamine)s (PAAs) membrane activity and cytotoxicity. Optimizing the PAA counterion is crucial for developing effective endosomolytic polymers for gene and toxin delivery.
Area of Science:
- Polymer Chemistry
- Biomaterials Science
- Drug Delivery
Background:
- Linear poly(amidoamine)s (PAAs) show potential as endosomolytic polymers for intracellular delivery due to pH-dependent membrane perturbation.
- Previous research primarily utilized PAAs in their hydrochloride form, limiting a comprehensive understanding of their properties.
Purpose of the Study:
- To systematically investigate the influence of various PAA counterions on pH-dependent membrane activity and general cytotoxicity.
- To guide the optimization of PAA structure for the development of advanced PAA-protein conjugates for enhanced intracellular delivery.
Main Methods:
- Synthesis of PAAs with diverse counterions (acetate, citrate, hydrochloride, lactate, phosphate, sulfate).
- Assessment of pH-dependent membrane activity using a rat red blood cell hemolysis assay.
- Evaluation of general cytotoxicity on murine melanoma (B16F10) and human endothelial (ECV-304) cell lines.
- Analysis of PAA solution properties using small-angle neutron scattering.
Main Results:
- PAA salts were non-hemolytic at neutral and slightly acidic pH (7.4, 6.5), unlike poly(ethyleneimine).
- At acidic pH (5.5), PAA sulfate and hydrochloride salts induced significant hemolysis, as did ISA 22 and 23 phosphate salts.
- All PAAs exhibited relatively low general cytotoxicity compared to poly-l-lysine, with hydrochloride salts showing the highest toxicity.
- Small-angle neutron scattering indicated counterion-dependent changes in PAA coil conformation and hydrodynamic radius.
Conclusions:
- The counterion identity critically affects the pH-dependent membrane activity and cytotoxicity of PAAs.
- Specific counterions (sulfate, hydrochloride, phosphate) enhance PAA-mediated membrane permeabilization at acidic pH.
- Counterion selection is a key factor in optimizing PAAs for endosomolytic applications and intracellular delivery systems.