Delayed nucleation in lipid particles

Abstract

Metastable states in first-order phase-transitions have been traditionally described by classical nucleation theory (CNT). However, recently an increasing number of systems displaying such a transition have not been successfully modelled by CNT. The delayed crystallization of phospholipids upon super-cooling is an interesting case, since the extended timescales allow access into the dynamics. Herein, we demonstrate the controllable behavior of the long-lived metastable liquid-crystalline phase of dilauroyl-phosphatidylethanolamine (DLPE), arranged in multi-lamellar vesicles, and the ensuing cooperative transition to the crystalline state. Experimentally, we find that the delay in crystallization is a bulk phenomenon, which is tunable and can be manipulated to span two orders of magnitude in time by changing the quenching temperature, solution salinity, or adding a secondary phospholipid. Our results reveal the robust persistence of the metastability, and showcase the apparent deviation from CNT. This distinctive suppression of the transition may be explained by the resistance of the multi-lamellar vesicle to deformations caused by nucleated crystalline domains. Since phospholipids are used as a platform for drug-delivery, a programmable design of cargo hold and release can be of great benefit.

Heating-Induced Switching to Hierarchical Liquid Crystallinity Combining Colloidal and Molecular Order in Zwitterionic Molecules

“…The observed coexistent lamellar phases Sm1, Sm2, and Sm3 all show different but equidistant reflections in the SAXS graphs (Supporting Information Section S4). Polymorphism has been observed in thermotropic LCs, wherein different types of packings are observed depending on the cooling rate and the thermal history. ,− A detailed study of the coexisting/metastable phases was outside the scope of the current focus, but they could arise from kinetically trapped states that are unable to relax below the clearing point. These lamellar phases have different rigidities corresponding to the state of the alkyl tails, as seen by the temperature-dependent FTIR measurements (Figure a).…”

Angular super-resolution retrieval in small-angle X-ray scattering

“…However, recent advances in small scale laboratory-based X-ray sources and, in particular, in high-efficiency solid-state 2D X-ray detectors, enable conducting many of the experiments using laboratory-based SAXS systems. For example, laboratory-based systems are best suitable for the study of hours-long dynamics for a nanoscopic structural organization 3 , 9 , 10 or when SAXS is used to optimize sample preparation. Currently, there are a handful of well-established SAXS suppliers that provide systems that can measure structural information in a variety of disciplines.…”