Cationic star polymers: preparation and applications

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Water-soluble cationic polymers have been extensively used as flocculants in papermaking and these polymers are now being considered as vehicles for DNA delivery. Gene therapy or DNA-based drugs (involving the introduction of synthetic DNA molecules to a cell to replace defective genes) are extremely promising for dealing with various diseases such as cancer, AIDS and neurological disorders due to their selective recognition of targets and pathways. A significant challenge in exploiting DNA-based drugs is the lack of a safe and efficient delivery system for nucleic acids. The proposed research will address this challenge by developing a range of cationic star polymers with desirable structures as non-viral vectors for DNA delivery. The syntheses will be based on our previous success in preparing a cyclodextrin-based initiator for living free-radical polymerization that permits the preparation of 21-arm star polymers with controllable arm structure, charge types and charge distribution. The preparation of cationic polymer will also be extended to linear and biopolymer types. The variety of tailor-modified polymers will enable us to identify the optimal structures for maximizing the DNA delivery efficiency. Further extending the arm chain lengths in polymeri- zation generates novel star polymers that can be used as flocculants (or retention aids) for papermaking - another important application of cationic star polymers. With much lower solution viscosity at the molecular weights similar to linear ones, cationic star polymers will facilitate the making-down process and improve retention performance in papermaking. The star polymers with controllable spherical sizes enable us to reveal the retention mechanism from a colloid scientific point of view. Several state-of-art techniques, a Pico-force atomic force microscope (AFM) in particular, will be utilized to visualize the polymer/DNA complex and to quantify the driving (or bonding) forces for both DNA complex formation and filler floc formation, providing information unachievable previously. The findings obtained from the proposed research will significantly benefit Canadian pharmaceutical, papermaking, and aquaculture industries and Canadian public health.