Effect of the Molecular Weight of Polyelectrolyte and Surfactant Chain Length on the Solid-Phase Molecular Self-Assembly.

Solid-phase molecular self-assembly (SPMSA) is emerging as an efficient approach, leading to scale-span self-assembled supramolecular films. With SPMSA, freestanding macroscopic supramolecular films can be formed upon mechanically pressing the precipitates formed with polyelectrolytes and oppositely charged surfactants. Herein, we report that the film formation ability and the mechanical strength of the resultant film depend highly on the surfactant chain lengths and the molecular weight of polyelectrolytes. A coarse-grained molecular dynamics study revealed that the longer surfactant chains are beneficial for the ordered assembly of surfactant bilayers in the film, whereas the larger molecular weight of PE favors the enhanced mechanical strength of the film by promoting the long-range order of the surfactant bilayers. The current results disclosed the physical insight of the surfactant chain length and the molecular weight of polyelectrolytes into the film structure and mechanical strength, which is of practical importance in guiding the creation of SPMSA materials.

Impacts of trehalose and l-proline on the thermodynamic nonequilibrium phase change and thermal properties of normal saline.

Understanding the phase change behavior and thermal properties of cryoprotective agents (CPAs) in biological solutions is essential for enhancing the success of cryopreservation and biobanking. In this study, the phase change behavior and thermal properties of normal saline added with trehalose or l-proline were investigated using differential scanning calorimeter (DSC) and cryomicroscope during freezing and warming. The addition of trehalose or l-proline can eliminate the eutectic formation in normal saline. Trehalose had significantly lower latent heat release than l-proline does at a high concentration of 1 M (P < 0.05), while unfrozen water content of trehalose is significantly lower than that of l-proline at all the concentrations (P < 0.05). It was also found that addition of 0.2 M, 0.3 M and 1 M trehalose can achieve partial vitrification in normal saline and that the glass transition temperature rises along with the increase in concentrations of trehalose. However, no vitrification was observed in normal saline with l-proline at any concentrations. Besides, rates of ice crystal growth in normal saline added with trehalose are slower than those in normal saline with l-proline at the same concentrations. These results suggest that both trehalose and l-proline can act as CPAs by avoiding eutectic formation and inhibiting ice formation in normal saline for cell cryopreservation. It could be useful for CPA selection and designing in the future.

Preparation of chitosan microcarriers by high voltage electrostatic field and freeze drying.

In this paper, a biocompatible, non-toxic porous chitosan microcarrier was prepared by high voltage electrostatic field and freeze drying technology. The chitosan solution was pushed from the syringe drop into the sodium polyphosphate solution using a booster pump. The droplet diameter of the chitosan solution was adjusted by the voltage of the electrostatic field formed between the syringe and the sodium polyphosphate solution. The droplets were dropped into a sodium polyphosphate solution to form microspheres. The microspheres were subsequently immersed in 25% (v/v) glutaraldehyde for crosslinking to enhance the mechanical strength of the microspheres. These microspheres were then frozen and lyophilized to form a microcarrier. By performance characterization, these microcarriers had a particle size of 400-500 µm, a pore size of 15-20 µm, and a porosity of 90%. Under simulated human environmental conditions, the 21-day degradation rate was about 30%, indicating that the microcarriers have potential clinical value.