A Dynamic Interface Based on Segregation of an Amphiphilic Hyperbranched Polymer Containing Fluoroalkyl and Oligo(ethylene oxide) Moieties

Role of Surface Dipole Alignment in Modulating Cellular Activities on Poly(vinylidene fluoride)

Understanding and controlling the surface properties of bioscaffolds are crucial for regulating cell adhesion and proliferation behaviors. We here focused on poly(vinylidene fluoride) (PVDF), in which polymer chains are oriented through poling treatment to form a polar β-form crystal. The surface aggregation states of uniaxially stretched PVDF films subjected to poling treatment were investigated based on water contact angle measurements and sum-frequency generation spectroscopy. During poling treatment under a sufficiently strong electric field, the dipole moments of β-form crystals, which are inherently aligned within each crystalline domain, become more uniformly oriented across the entire film. As a result, the surface resists structural reorganization even upon exposure to water. This stable surface, which maintains its aggregation states despite environmental changes, was found to promote cell adhesion and proliferation, as well as protein adsorption. Our findings contribute to a deeper understanding of the relationship between the aggregation states on polymer scaffold surfaces and protein interactions, ultimately advancing insights into cell behaviors.

Cancer cell adhesion property on all-chitin composite films with reduced crystallinity

We previously prepared self-reinforced chitin composite (SR-ChC) films, also called all-chitin composites, comprising two components, that is, scale-down chitin nanofibers (SD-ChNFs) with high crystallinity and scale-down low-crystalline chitin (SD-LC-Ch) matrixes. In this study, we precisely evaluated hydrophilicity under water enviromental conditions and its effect on cell adhesion using human-derived cancer cells on the SR-ChC film surfaces. The surface analysis of the SR-ChC films with reduced crystallinity revealed reorientation of the molecular chain assemblies with amino groups in the SD-LC-Ch components in water. Consequently, the amount of the SD-LC-Ch components gave rise to increasing the number of hydrophilic amino groups on the film surfaces, which resulted in efficiency of cell adhesion and elongation. This study concludes that the hydrophilic SD-LC-Ch components in the lower crystalline SR-ChC films strongly contribute to exhibiting new functions, related to interaction with biological substrates, such as cells. © 2017 ElsevierInc.Allrightsreserved.

Water-Induced Crystal Transition and Accelerated Relaxation Process of Polyamide 4 Chains in Microfibers

Microplastics have recently been identified as one of the major contributors to environmental pollution. To design and control the biodegradability of polymer materials, it is crucial to obtain a better understanding of the aggregation states and thermal molecular motion of polymer chains in aqueous environments. Here, we focus on melt-spun microfibers of a promising biodegradable plastic, polyamide 4 (PA4), with a relatively greater number density of hydrolyzable amide groups, which is regarded as an alternative to polyamide 6. Aggregation states and thermal molecular motion of PA4 microfibers without/with a post-heating drawing treatment under dry and wet conditions were examined by attenuated total reflectance-Fourier transform infrared spectroscopy and wide-angle X-ray diffraction analysis in conjunction with dynamic mechanical analysis. Sorbed water molecules in the microfibers induced the crystal transition from a meta-stable γ-form to a thermodynamically stable α-form via activation of the molecular motion of PA4 chains. Also, the post-drawing treatment caused a partial structural change of PA4 chains, from an amorphous phase to a crystalline phase. These findings should be useful for designing PA4-based structural materials applicable for use in marine environments.

Modification of a Polymer Surface by Partial Swelling Using Nonsolvents

Surface modification without changing the physical properties in the bulk is of pivotal importance for the development of polymers as devices. We recently proposed a simple surface functionalization method for polymer films by partial swelling using a nonsolvent and demonstrated the incorporation of poly(2-methoxyethyl acrylate) (PMEA), which has an excellent antibiofouling ability, only into the outermost region of a poly(methyl methacrylate) (PMMA) film. We here extend this technology to another versatile polymer, polystyrene (PS). In this case, PS and PMEA have different solubility parameters making it difficult to select a suitable solvent, which is a nonsolvent for PS and a good solvent for PMEA, unlike the combination of PMMA with PMEA. Thus, such a solvent was first sought by examining the swelling behavior of PS films in contact with various alcohols. Once a mixed solvent of methanol/1-butanol (50/50 (v/v)) was chosen, PMEA chains could be successfully incorporated at the outermost region of the PS film. Atomic force microscopy in conjunction with neutron reflectivity revealed that chains of PMEA incorporated in the PS surface region were well swollen in water. This leads to an excellent ability to suppress the adhesion of platelets on the PS film.

Design of a Bioinert Interface Using an Amphiphilic Block Copolymer Containing a Bottlebrush Unit of Oligo(oxazoline)

We designed an amphiphilic block copolymer, poly(methyl methacrylate)-block-poly[oligo(2-ethyl-2-oxazoline) methacrylate] (PMMA-b-P[O(Ox)MA]), suitable for bioinert coating. Angular-dependent X-ray photoelectron spectroscopy and neutron reflectivity measurements revealed that the outermost surface of a dried film of PMMA-b-P[O(Ox)MA] was covered with the PMMA block-rich layer. Once the film came into contact with water, the P[O(Ox)MA] bottlebrush block was segregated toward the water interface. This structural rearrangement in the outermost region of the film resulted in the formation of the swollen oligo(oxazoline) layer with excellent bioinertness in terms of the suppression of serum protein adsorption and NIH3T3 fibroblast adhesion.

Surface Segregation of a Star-Shaped Polyhedral Oligomeric Silsesquioxane in a Polymer Matrix

A simple way to control only the surface properties of polymer materials, without changing the bulk properties, has long been desired. The segregation behavior when a component with a tiny amount fed into the matrix is thermodynamically enriched at the surface is one of the candidate methods. This capability was examined herein by focusing on a star-shaped polyhedral oligomeric silsesquioxane (s-POSS), where the central POSS unit is tethered to eight isobutyl-substituted POSS cages as a surface modifier. X-ray photoelectron spectroscopy revealed that the surface of a film of poly(methyl methacrylate) (PMMA) was almost completely covered with POSS units by adding just 5 wt % s-POSS to it. The segregated POSS dramatically altered the physical properties such as molecular motion and the mechanical and dielectric responses at the surface of the PMMA film. These findings make it clear that s-POSS is an excellent surface modifier for glassy polymers.