Phase transition and gelation in cellulose nanocrystal-based aqueous suspensions studied by SANS.

HYPOTHESIS: Aqueous suspensions of cellulose nanocrystals (CNC) form a re-entrant liquid crystal (LC) phase with increasing salinity. Phase separation occurs in this LC state leading to a biphasic gel with a flow programmable structure that can be used to form anisotropic soft materials. We term this state a Liquid Crystal Hydroglass (LCH). Defining the mechanisms by which the LCH forms requires detailed structural analysis at the mesoscopic length scale. EXPERIMENTS: By utilising Small Angle Neutron Scattering (SANS), we investigated the microstructure transitions in CNC suspensions, with a particular focus on the unique LC re-entrancy and gelation into the biphasic LCH. FINDINGS: Scattering from LCH gels comprises contributions from a dispersed liquid state and static heterogeneity, characterised using a Lorentzian-Gaussian model of inhomogeneity. This conceptually supports a gelation mechanism (spinodal decomposition) in CNC suspensions towards a biphasic structure of the LCH. It also demonstrates that, with increasing salinity, the non-monotonic variation in effective volume fraction of CNC rods fundamentally causes the LC re-entrancy. This work provides the first experimental characterisation of the LC-re-entrancy and formation of an anisotropic LCH gel. The proposed mechanism can be extended to understanding the general behaviour of anisotropic colloids.

Phase Difference of Traditional Chinese Medicine Compound Decoction： A Review / 中国实验方剂学杂志

Decoction is a traditional clinical way of traditional Chinese medicine （TCM） compound. A series of complex physical and chemical changes are often involved in the process of decoction， which presents a mixed-phase system. In most studies on the TCM compound decoction， it has always focused on the amounts of chemical substances in decoction， while the phase properties and existence forms of these components are neglected. Most of the chemical components exist in the mixed-phase system as molecules， ions or other particles. According to the particle size of the contained particles， the differences among the phases， including true solution phase， colloidal phase， suspended phase and precipitated phase， lead to their differences in pharmaceutical and biological effects. Based on the above research background， this paper takes the phase state differences of decoction as the breakthrough point， and systematically reviews the physicochemical properties， the physical structures of the active components and the biological effects of the decoction caused by the phase state differences. The phase state differences of TCM compound decoction have been found to be closely related to their efficacy， which might be a good perspective to investigate the possible mechanism. It might provide a beneficial reference for the exploration of related basic research on TCM compounds.

Polymer-mediated drug supersaturation - A spotlight on the interplay between phase-separated amorphous drug colloids and dissolved molecules.

HYPOTHESIS: Colloidal aggregation phenomena have been found responsible for the supersaturation of poorly water-soluble drugs, potentially leading to bioavailability enhancements. Unlike coarse precipitates, phase separation in the form of colloids, is expected to enhance drug supersaturation performance. Therefore, a high proportion of these colloids should correlate with the extent and the kinetics of supersaturation. The prime objective of the current study is to provide a mechanistic understanding on supersaturation for the model drug albendazole (ALB) in combination with twelve polymers. EXPERIMENTS: Species separated after a pH-shift were characterized by dynamic light scattering (DLS), freeze-fracture electron microscopy (FF-EM) and transmission X-ray diffraction (XRD). Laser diffraction (LD) in a liquid cell was introduced for a relative quantification of the colloidally separated species, described as colloid fraction. The pH-dependent supersaturation was assessed online using a miniaturized dissolution assay. FINDINGS: Here, a measure of the extent of amorphous colloidal phase separation was established, and its impact on supersaturation was evaluated. As a result, a correlation was found between the extent of supersaturation and the colloid fraction. This confirmed the dependence of polymer-mediated enabling and preservation of supersaturation on the ability of polymers to stabilize colloid fractions. Furthermore, a fixed ratio was suggested between the dissolved drug and colloidally separated drug as the kinetic profiles of both species showed similar trajectories. In conclusion, colloid fractions were identified to be responsible for dissolved and potentially bioavailable drug molecules.

Investigating the role of colloids on the distribution of bisphenol analogues in surface water from an ecological demonstration area, China.

Owing to the widespread use of bisphenol analogues (BPs) as substitutes for bisphenol A (BPA), the presence of BPs in multiple environments is of increasing concern. However, there is a limited understanding of the effects of colloids on the distribution and risk assessment of BPs traditionally dissolved in surface water. In this study, seven BPs were investigated in both the truly dissolved (<5 kDa) and colloidal (5 kDa to 1 µm) phases with water, with mean concentrations in the range of 71.6-671 ng/L and 5.84-76.6 ng/L, respectively. BPA and bisphenol S (BPS) were the dominant BPs in both phases, but a clear positive correlation was found between the adsorption contribution proportions of colloids to BPs and their hydrophobicity (octanol-water partition coefficient). The colloids contributed 50.4% of bisphenol AF, 33.4% of tetrabromobisphenol A, 25.2% of bisphenol F, 10.9% of BPA and 9.50% of BPS in the traditionally dissolved phase (<1 µm), which suggests that colloids play an important role in regulating the transformation and transportation of BPs in aquatic environments. Based on BP concentrations in the truly dissolved phase, only moderate risk levels for BPs towards algae, daphnia and fish were posed, and no oestrogenic risk existed in the study area.

Emergence of Life on Earth: A Physicochemical Jigsaw Puzzle.

We review physicochemical factors and processes that describe how cellular life can emerge from prebiotic chemical matter; they are: (1) prebiotic Earth is a multicomponent and multiphase reservoir of chemical compounds, to which (2) Earth-Moon rotations deliver two kinds of regular cycling energies: diurnal electromagnetic radiation and seawater tides. (3) Emerging colloidal phases cyclically nucleate and agglomerate in seawater and consolidate as geochemical sediments in tidal zones, creating a matrix of microspaces. (4) Some microspaces persist and retain memory from past cycles, and others re-dissolve and re-disperse back into the Earth's chemical reservoir. (5) Proto-metabolites and proto-biopolymers coevolve with and within persisting microspaces, where (6) Macromolecular crowding and other non-covalent molecular forces govern the evolution of hydrophilic, hydrophobic, and charged molecular surfaces. (7) The matrices of microspaces evolve into proto-biofilms of progenotes with rudimentary but evolving replication, transcription, and translation, enclosed in unstable cell envelopes. (8) Stabilization of cell envelopes 'crystallizes' bacteria-like genetics and metabolism with low horizontal gene transfer-life 'as we know it.' These factors and processes constitute the 'working pieces' of the jigsaw puzzle of life's emergence. They extend the concept of progenotes as the first proto-cellular life, connected backward in time to the cycling chemistries of the Earth-Moon planetary system, and forward to the ancient cell cycle of first bacteria-like organisms. Supra-macromolecular models of 'compartments first' are preferred: they facilitate macromolecular crowding-a key abiotic/biotic transition toward living states. Evolutionary models of metabolism or genetics 'first' could not have evolved in unconfined and uncrowded environments because of the diffusional drift to disorder mandated by the second law of thermodynamics.