Micromorphology Memory in Amphiphilic Polypeptides

Abstract

ABSTRACT:Micromorphology memory was observed using thin films of PEGylated polypeptides, poly{(-benzyl-L-aspartate) (BLA)-block-ethylene glycol (EG)-block-BLA}. The slow vaporization of polymer dichloromethane solutions led to the formation of multi-spherulite films, which disappeared upon heating above the PEG melting temperature, 57 C, but reappeared by successive cooling, down to 30 C, thereby changing the spherulite interface morphology. The water-immersion of recrystallized films caused the self-assembly of peptide chains to form water-swollen networks with spherulites, but surprisingly, spherulite interface morphologies remained completely the same as oncedisappeared morphologies in the original dry films. A similar memory behavior was also observed in the pattern inside a milliscaled spherulite which entirely occupied the network. Spectroscopic and microscopic studies suggest that appropriate peptide conformations are very important for memorized micromorphology.[doi:10.1295/polymj.PJ2006109] KEY WORDS Triblock Copolymers / Spherulites / Shape-memory / Self-assembly / Polypeptides / Micromorphology / The memory of the organic system has attracted researcher's attention in terms of life sciences such as immunology and brain science, and material fields such as molecular machines and electronic devices. Macromolecular helical forms were memorized regardless of chirality 1 and hydrogel macroscopic forms were memorized by supporting changeable cross-linking junctions.2 However a key factor in the life action and the material development is rather in molecular aggregates, as cells move based on changes in protein-assembly forms of myosine bundles with actin. 3Micromorphology memory, regarding macromolecular chain self-assembly has never been observed as far as we know, although the memory based on the multistable state in the crystalline or liquid crystalline state has been seen on the nanoscale level. 4 In previous papers, we synthesized an ABA-type triblock copolymer comprised of poly(-benzyl-Laspartate) (PBLA) as a hydrophobic (A) segment and poly(ethylene glycol) (PEG, number-average molecular weight, M n ¼ 20;300, a polymerization degree Dp ¼ 460) as a hydrophilic (B) segment.5-7 The copolymers had monodispersed chain lengths and excellent cell compatibility.7 Although ABA-type triblock copolymers containing PEG as a B block were widely studied and the importance of interblock interactions on the mutual crystallization behavior following thermal treatment has been reported, 8 there are no reports on block copolymers containing long PEG blocks with Dp of more than 200, except for ours. In the course of studies on in situ hydrogelation of triblock PBLA-PEO-PBLA copolymers with long PEO blocks, we found a micromorphology memory of the copolymer spherulites by water-immersion. Herein we report such a unique behavior and the relationship between the micromorphology memory and peptide structures. The appropriate peptide conformation was indispensable for memory induction.

Secondary-Structure-Mediated Hierarchy and Mechanics in Polyurea–Peptide Hybrids

“…For instance, Z5–10 still exhibits faint spherulites; however, Z5–20 only displays birefringence. This result suggests that the thermal history strongly influences the morphology of solid-state network PU films. ,− Future work on the kinetics of spherulite formation will aid in the understanding of PZLY’s role in crystal growth; however, this is not within the scope of the current project . It is noted that the kinetics of spherulite growth are influenced by molecular mobility, suggesting that a permanent network may slow down the kinetics of spherulite growth …”

“…However, the Z20–20 spherulite diameter is notably higher than the control films, suggesting that competitive interactions of α-helices promote increased intermolecular associations between PEG and PZLY. This higher spherulite size for the Z20 series may be the result of an increase in α-helical content that aids in crystal formation due to the similarity in crystal sizes of the PEG 7 2 helix and an α-helix, which will be explored further via wide-angle X-ray scattering studies. ,,, Thus, the incorporation of peptides into network PEG–PU films was harnessed to control PEG crystal growth and hierarchy based on secondary structure and peptide content.…”

Self-assembled Monolayers and Nanocomposite Hydrogels of Functional Nanomaterials for Tissue Engineering Applications

“…[134][135][136][137][138][139] A wide range of NMs and polymers have been used for the generation of NC hydrogels with superior properties and tailored functionalities. In particular, silica based NMs such as clays (e.g., hectorite, montmorillonite), silica NPs, other minerals such as polyhedral oligomeric silsesquioxane, [140,141] polysiloxane, [142,143] fibrillar attapulgite, [144] and hydrotalcite [145] combined with polymers [146,147] such as poly(N-isopropylacryamide) or poly(N,N-dimethylacrylamide), poyl(acryl amide), poly(vinyl alcohol), poyl-(ethylene oxide) (PEO), etc. have been widely used for mechanically strong and cell-compatible NC hydrogels preparation.…”

Uniaxial Swelling in LC Hydrogels Formed by Two-Step Cross-Linking

“…The anisotropic structures of these biological tissues enable the elaborate functions of living organisms . For example, actin and myosin show a liquid crystalline-like anisotropic structure in a muscle sarcomere, which contributes to the smooth motion of muscle contraction in one direction while limiting motion in the other direction. , In order to impart anisotropic properties to synthetic hydrogels, some techniques have been reported such as directional freezing, self-assembly, − and mechanical reorientation . Although one of the most attractive targets for anisotropic hydrogels is one-directional swelling, like a coiled spring, there have been no reports of this behavior as the water molecules move freely, rendering the network amorphous.…”