Silk‐inspired polyurethane containing GlyAlaGlyAla tetrapeptide. II. physical properties and structure

Abstract

Biomedical polyurethane (BPU) and silk fibroin have similarly molecular architecture in their primary and aggregate structure, both of which have amide bonds and microphase separation, and they have been employed as scaffold materials for biomedical applications. Based on this, as the featured peptide sequence of silkworm silk fibroin, GlycineAlanineGlycineAlanine (GlyAlaGlyAla) tetrapeptide was synthesized by using traditional liquid-phase peptide synthesis method with Boc-protected glycine and alanine as starting materials, and was transformed to its derivative with two amine-terminated functional groups. The derivative was introduced as a chain extender into the backbone to form the hard segment of a silk-inspired PU with urea-linkage. Related measurements show that molecular weight of the synthesized silk-inspired PU ranged from 13,000 to 15,000. Fourier transform infrared (FTIR) absorption bands of Amides I and II are at 1651 cm À1 and 1534 cm À1 , and Raman absorption band of Amide III is at 1302 cm À1 . UV-Vis absorption peak of the silk-inspired PU is at 266 nm. This new concept and strategy may allow the fabrication of a new class of thermoplastic polyurethane elastomers to mimic the structure and properties of silk fibroin of silkworms and spiders. Information provided by this study may be used to better understand the correlation between the natural and man-made materials.

Chemical Synthesis of Silk-Mimetic Polymers

“…The polymer product then was formed into granules by dropping the reaction solution into a 3:1 mixture of methanol and water, and further extracted in toluene [107]. Molecular weights of 13 kg/mol were achieved, which is slightly lower than the molecular weight of copolymers made in similar conditions with 1,4 butanediol instead of the GAGA-HDI-GAGA triblock [108]. Unlike silk fibroin and other silk-mimetic polymers previously described, these pTHF-containing silk-mimetic polymers demonstrated good solubility in a variety of organic solvents, which facilitated processing into fibers and films.…”

“…Like silk fibroin, conventional TPUs consist of rigid ("hard") and flexible ("soft") segments that form a microphase segregated structure which enhances mechanical properties [103][104][105][106]. As TPUs contain urethane linkages rather than amide bonds, the incorporation of silk-like motifs introduces an interesting strategy for tuning materials properties [107][108][109]. In this work, GAGA tetrapeptides were synthesized stepwise in solution using Boc-protected amino acids from both ends of HDI [107].…”

Silk‐inspired polyurethane containing glyalaglyala tetrapeptide. III. morphological, thermal, and mechanical features of electrosprayed and electrospun deposition

“…The silk‐inspired PU containing GlyAlaGlyAla tetrapeptide in this study was obtained by a two‐step polymerization method. The detailed synthesis procedures and the chemical composition (Figure ) of the final PU were illustrated in previous articles . The PU products were made into granules by being dripped into a mixture of methanol‐water (3/1, v/v) and then coagulated .…”

“…The detailed synthesis procedures and the chemical composition ( Figure 2) of the final PU were illustrated in previous articles. 20,21 The PU products were made into granules by being dripped into a mixture of methanol-water (3/1, v/v) and then coagulated. 23 The granules were further purified by extraction in toluene, dried, and stored in granular or flaky forms.…”

“…In our recent work, the silk‐inspired PU containing GlyAlaGlyAla tetrapeptide was synthesized and its physical properties and structure were quantitatively or qualitatively identified by means of elemental analysis (EA), 1 H nuclear magnetic resonance ( 1 H NMR) spectroscopy, pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), intrinsic viscosity ([η]), gel permeation chromatography, Fourier transform infrared, Raman spectroscopy, and ultraviolet‐visible (UV–vis) spectroscopy. We have found GlyAlaGlyAla tetrapeptide within the chain extender is partially incorporated into the PU chain, and the PU molecular weight ranged from 13,000 to 15,000, which is quite low and is hard to be improved as reported in literatures .…”