Abstract
Water-soluble and cytocompatible polymers were investigated to enhance a transporting efficiency of biomolecules into cells in vitro. The polymers composed of a 2-methacryloyloxyethyl phosphorylcholine (MPC) unit, a hydrophobic monomer unit, and a cationic monomer unit bearing an amino group were synthesized for complexation with model biomolecules, siRNA. The cationic MPC polymer was shown to interact with both siRNA and the cell membrane and was successively transported siRNA into cells. When introducing 20–50 mol% hydrophobic units into the cationic MPC polymer, transport of siRNA into cells. The MPC units (10–20 mol%) in the cationic MPC polymer were able to impart cytocompatibility, while maintaining interaction with siRNA and the cell membrane. The level of gene suppression of the siRNA/MPC polymer complex was evaluated in vitro and it was as the same level as that of a conventional siRNA transfection reagent, whereas its cytotoxicity was significantly lower. We concluded that these cytocompatible MPC polymers may be promising complexation reagent for introducing biomolecules into cells, with the potential to contribute to future fields of biotechnology, such as in vitro evaluation of gene functionality, and the production of engineered cells with biological functions.
Highlights
In the molecular design of a safe and effective water-soluble polymers for promoting the introduction of a biomolecule into cells, the interactions between the polymer and the biomolecule and that between the polymer and the cell membrane are key factors [1,2,3,4]
In the case of amphiphilic block-type copolymers, they form micelle-like structures in an aqueous medium, through interaction between hydrophobic units [35,36,37]
In the case of amphiphilic random copolymers, polymer aggregates can be formed in aqueous media, their structure is unstable and is dependent on the concentration of polymer [32]
Summary
In the molecular design of a safe and effective water-soluble polymers for promoting the introduction of a biomolecule into cells, the interactions between the polymer and the biomolecule and that between the polymer and the cell membrane are key factors [1,2,3,4]. Many cationic both lipids and polymers have been examined as transporter molecules for specific biomolecules into cells in vitro [3,8,9,10]. When focusing on the interaction between cells and polymers, it is necessary to consider the characteristics of the cell membrane, which is the first barrier. The siRNA solution was diluted with a serum-reduced medium Opti-MEM (Invitrogen) to the desired concentration, before use. Polymer solutions were prepared by dissolving the polymer in Opti-MEM. In the case of PMBA154M, which would not completely dissolve in Opti-MEM, it was dissolved in ultrapure water. The concentration of polymer was determined according to the charge ratio with the siRNA. The charge ratio was fixed at 5/1, and concentration of the polymer was
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