Abstract
The structural evolution of a diamond-type bicontinuous lipid cubic phase upon application of
thermal and chemical (hydration agent) stimuli is investigated by means of small-angle neutron (SANS)
and X-ray scattering (SAXS). The soft-matter cubic architecture responds by dramatic swelling (DLarge cubic structure) upon incorporation of a hydration-enhancing guest component (octyl glucoside) at low and ambient
temperatures, the aqueous channel diameter increasing twice to 7 nm. DLarge appears to be built up from
an assembly of cubosomic domains, which may coexist with an amphiphilic lamellae domain at low
temperatures. The chemical stimulus concentration can be selected as to tune the hydration of the
nanochannels in the DLarge phase and its transformation into a DNormal phase at temperatures above the body temperature. Two-dimensional SANS images recorded upon heating scan reveal growth of
spontaneously oriented domains of single-crystal cubic nature. Phase separation and squeezing out the
guest-hydrating agent from the higher-curvature regions of the amphiphilic bilayer suggest a possible
mechanism for the established transformations. The order-order structural transition, cubic DLarge - cubic DNormal, is found to be reversible upon cooling. The obtained results put forward a structure-based concept
for release of encapsulated guest molecules from stimuli-responsive and self-regulated cubosomic
nanocarriers.
DOI Link to Publication