Glycolipid based cubic nanoparticles: preparation and structural aspects.

Abstract

Kinetically stable cubic colloidal particle dispersion was produced from a glycolipid using a novel preparation strategy based on the dialysis principle. The use of synchrotron small-angle X-ray diffraction (SSAXD) permitted the identification of exact structure of these dispersed particles in the colloidal state. Dynamic light scattering methods were used to obtain size and size distributions. A glycoside, 1-O-phytanyl-beta-D-xyloside (beta-XP), that exhibits Pn3m cubic phase in an excess aqueous medium, was used as the lipid material. The dialysis technique includes controlled stirring action both inside and outside of the dialysis membrane tube. Initially, a mixed micellar system composed of beta-XP, n-octyl-beta-D-glucopyranoside (beta-OG) and a triblock copolymer, Pluronic F127 (PL) was prepared in the aqueous medium. About 10 wt.% of PL to lipid weight was found to be sufficient to produce stable colloidal dispersions. The mean volume diameter of these colloidal particles was found to be in the range of 0.85 +/-0.05 microm. The cubic phase structure of these colloidal particles is greatly depended on the final beta-OG concentration level in the system. Coexistence of Im3m and Pn3m cubic structures has been identified in these colloidal particles. This coexistence has the characteristics of Bonnet relation, which forms a compelling case for the infinite periodic minimal surface (IPMS) descriptions. These colloidal particles could restore pure Pn3m phase structure, but a longer dialysis time was needed. This work, in general, will open up new possibilities for membrane protein reconstitution and other relevant biological applications using colloidal cubic lipid particles.