Self-Assembled Biodegradable Block Copolymers and DNA Lipoplexes as Potential Nanomedicines
Featuring Lei Zhu, Ph.D.
Associate Professor, Polymer Program
Location: McDonald Douglas Auditorium (MDEA)
Polymeric nanoparticle formation via self-assembly is an attractive approach for delivery systems. In this presentation, we focus on two self-assembled polymer and biopolymer systems, namely, biodegradable block copolymers and DNA lipoplexes. In the first system, incompatible blends of poly(ethylene oxide)-/b/-poly(L-lactide) (PEO-PLLA) and poly(ethylene-/co/-butene)-/b/-poly(D-lactide) (PEB-PDLA) were studied. Stereocomplexation between biodegradable PLLA and PDLA induced intriguing phase morphologies. When the molecular weight of PEB (4.2k) was higher than that of PEO (2k), inverted honeycomb cylindrical morphology was observed in the melt, whereas biomimetic onion-like crystals were obtained in the solid-state. We believe that noncentrosymmetric lamellar morphology was responsible for the onion crystal formation, which was induced by unbalanced surface stresses at basal planes of the stereocomplex lamellar crystals. In the second system, synthetic cationic lipids having various molecular shapes were used to complex with double-stranded DNA. When the shape of the lipid tails changed from rod-like (cyanobiphenyl), to discotic (triphenylene), and finally to cubic [polyhedral oligomeric silsesquioxane (POSS)], the liquid crystalline structures of the DNA lipoplexes transformed from lamellar to inverted hexagonal. We attributed this change to the negative curvature of the POSS imidazolium lipid. Potential applications for biomimetic onion crystals and organic/inorganic DNA nanocomposites may be controlled drug and gene delivery.
About the Speaker:
Lei Zhu received his B.S. degree in materials chemistry in 1993 and his M.S. degree in polymer chemistry and physics in 1996 from