Cationic polymers for DNA origami coating - examining their binding efficiency and tuning the enzymatic reaction rates.

DNA origamis are fully tailored, programmable, biocompatible and readily functionalizable nanostructures that provide an excellent foundation for the development of sophisticated drug-delivery systems. However, the DNA origami objects suffer from certain drawbacks such as low cell-transfection rates and low stability. A great deal of studies on polymer-based transfection agents, mainly focusing on polyplex formation and toxicity, exists. In this study, the electrostatic binding between a brick-like DNA origami and cationic block-copolymers was explored. The effect of the polymer structure on the binding was investigated and the toxicity of the polymer-origami complexes evaluated. The study shows that all of the analyzed polymers had a suitable binding efficiency irrespective of the block structure. It was also observed that the toxicity of polymer-origami complexes was insignificant at the biologically relevant concentration levels. Besides brick-like DNA origamis, tubular origami carriers equipped with enzymes were also coated with the polymers. By adjusting the amount of cationic polymers that cover the DNA structures, we showed that it is possible to control the enzyme kinetics of the complexes. This work gives a starting point for further development of biocompatible and effective polycation-based block copolymers that can be used in coating different DNA origami nanostructures for various bioapplications.

Conjugation-induced fluorescent labeling of proteins and polymers using dithiomaleimides.

Dithiomaleimides (DTMs) with alkyl substituents are shown to be a novel class of highly emissive fluorophores. Variable solubility and further functionalization can easily be tailored through the choice of N and S substituents. Inclusion of a DTM unit into a ROP/RAFT initiator or insertion into the disulfide bond of salmon calcitonin (sCT) demonstrates the utility for fluorescent labeling of polymers and proteins. Simultaneous PEGylation and fluorescent labeling of sCT is also demonstrated, using the DTM unit as both a linker and a fluorophore. It is anticipated that DTMs will offer an attractive alternative to commonly used bulky, planar fluorophores.