Thermoresponsive nanostructures by self-assembly of a poly(N-isopropylacrylamide)-lipid conjugate.
The synthesis and purification of a poly(N-isopropylacrylamide)-lipid conjugate and its use in the preparation of a thermoresponsive lipid mesophase is described. Specifically, poly(N-isopropylacrylamide) with a single carboxyl group at one end was activated with dicyclohexylcarbodiimide/N-hydroxysuccinimide to form an active ester. This N-hydroxysuccinimide ester was then used to form a dimyristoyl-sn-glycero-3-phosphoethanolamine conjugate with poly(N-isopropylacrylamide) via an amide bond, rendering the conjugate amphiphilic. Quaternary phases comprising the conjugate, a phosopholipid, dimyristoylphosphatidylcholine, and a cosurfactant, N,N-dimethyldodecylamine-N-oxide, dispersed in water were found to self-assemble at room temperature to form liquid crystalline gels, adopting an expanded lamellar structure. A modest increase in temperature triggered the reversible conversion of the aggregate to a collapsed lamellar structure, while a modest reduction in temperature resulted in its conversion to a nonlamellar phase. The phases were characterized by polarized optical microscopy and small-angle X-ray scattering (SAXS).
Materials Science, Chemistry, Argonne National Laboratory, Argonne, Illinois 60439, USA.
Daniel N T
DN
Hay
Paul G
PG
Rickert
Sönke
S
Seifert
Millicent A
MA
Firestone
D000180:Acrylic Resins / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D036103:Nanotechnology / Q000379:methods*; D010714:Phosphatidylethanolamines / Q000138:chemical synthesis / Q000737:chemistry*; D012542:Scattering, Radiation; D013057:Spectrum Analysis; D013696:Temperature; D014961:X-Ray Diffraction; D014965:X-Rays
D000180:Acrylic Resins; D010714:Phosphatidylethanolamines; C052970:poly-N-isopropylacrylamide; C018525:1,2-dimyristoylphosphatidylethanolamine