Morphology transition in DNA block copolymer based polyelectrolyte complex micelles

Abstract

Polyelectrolyte complex micelles (PCMs) are nanoparticles formed by the complexation between a charged-neutral hydrophilic block copolymer and an oppositely charged polyelectrolyte. Herein, the effect of N/P ratio and DNA hybridization on morphology of PCMs formed from DNA-poly(ethylene glycol) (DNA-PEG) block copolymer and poly(L-lysine) (PLys) are investigated. Single-stranded (ss-) and double-stranded (ds-) DNA-PEG diblock copolymers are synthesized by solution-phase coupling. PCMs are prepared using thermal- and salt-annealing protocol under different N/P ratio conditions. Direct TEM imaging is used to observe the morphology of the PCMs. The TEM images show that the micelles are spherical in the majority of cases. Rod-like micelles are observed for salt-annealed ssPCMs at N/P=2, and dsPCMs at N/P=2, and 3 are shown to have ellipsoidal shapes. The present study can provide a basis for design and optimization of DNA block copolymer-based PCM systems for further application such as drug encapsulation or gene delivery.