Bioinspired assembly of functional block-copolymer nanotemplates.

A new concept on bioinspired assembly of functional diblock copolymers, capable of forming different microstructures through nucleobase-induced supramolecular interactions, has been explored. In this paper, a new series of uracil-functionalized poly(ε-caprolactone)-b-(4-vinylbenzyl uracil)s (PCL-b-PVBU) have been prepared which exhibit a high self-complementary ability in solution and solid states owing to the formation of uracil­uracil pairs by induced hierarchical self-assembly. The ordered morphologies of PCL-b-PVBU diblock copolymers changed from a lamellar, hexagonally packed cylinder to a sphere with respect to the content of the hydrogen bond segment. Moreover, we further show that the PCL segment could be easily extracted by enzymatic degradation, leading to a cylinder porous structure of long-range order, which gives a facile method for the fabrication of uracil-functionalized nanotemplates. In addition, bio-complementary PCL-b-PVBU/9-hexadecyladenine (AC16) hierarchical supramolecular complexes formed through strong cooperative hydrogen bonding between the uracil group of PVBU and the adenine group of A-C16. When the mixing ratios of PCL-b-PVBU/AC16 differ from the stoichiometric ratio, these complexes self-assemble into well-ordered lamellar and hexagonal structures; the changing morphology at different AC16 loadings reveals that the molecular structures of the PCL-b-PVBU/AC16 complexes are readily tailored.

Nucleobase-Functionalized Supramolecular Micelles with Tunable Physical Properties for Efficient Controlled Drug Release.

Complementary nucleobase-functionalized polymeric micelles, a combination of adenine-thymine (A-U) base pairs and a blend of hydrophilic-hydrophobic polymer pairs, can be used to construct 3D supramolecular polymer networks; these micelles exhibit excellent self-assembly ability in aqueous solution, rapid pH-responsiveness, high drug loading capacity, and triggerable drug release. In this study, a multi-uracil functionalized poly(ε-caprolactone) (U-PCL) and adenine end-capped difunctional oligomeric poly(ethylene glycol) (BA-PEG) are successfully developed and show high affinity and specific recognition in solution owing to dynamically reversible A-U-induced formation of physical cross-links. The U-PCL/BA-PEG blend system produces supramolecular micelles that can be readily adjusted to provide the desired critical micellization concentration, particle size, and stability. Importantly, in vitro release studies show that doxorubicin (DOX)-loaded micelles exhibit excellent DOX-encapsulated stability under physiological conditions. When the pH value of the solution is reduced from 7.4 to 5.0, DOX-loaded micelles can be rapidly triggered to release encapsulated DOX, suggesting these polymeric micelles represent promising candidate pH-responsive nanocarriers for controlled-release drug delivery and pharmaceutical applications.