Silk‐inspired polyurethane containing GlyAlaGlyAla tetrapeptide. I. Synthesis and primary structure

Abstract

Biomedical polyurethane (PU) and silk fibroin have similar molecular architecture in their primary and aggregate structure, both of which have imido bonds and microphase separation, and they have been employed as scaffold materials for biomedical applications. As the featured peptide sequence of silkworm silk protein, GlyAlaGlyAla (GAGA) tetrapeptide was synthesized by using traditional liquid-phase peptide synthesis method with Boc-protected alanine and glycine as starting materials, and was transformed to its derivative with two end-amido groups. The derivative was incorporated into the backbone of the classical synthetic copolyurethane as a chain extender to form a silk-inspired polyurethane. Elemental analysis showed the nitrogen content in the silk-inspired PU was higher than that in the butanediol-extended PU but lower than the theoretical value, indicating the chain extender containing GAGA was partially incorporated into the PU chain. The results from 1 H-nuclear magnetic resonance, Fourier transform infrared spectra, Raman scattering spectra and pyrolysis-gas chromatography/mass spectrometry qualitatively identified the primary structure of the silk-inspired polyurethane. This concept and strategy may allow the fabrication of a new class of thermoplastic polyurethane elastomer to mimic the structure and properties of silk fibers if in fiber form, which combines traditional synthetic polymer chains with peptide sequences.

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

“…Table II summarizes the main FTIR bands in typical PU, while Table III shows the FTIR values of amides obtained for BDO-extended PU, silkinspired PU and controls. In our previous report, 32 relative comparisons of FTIR and Raman spectra indicating the primary structure changes have been discussed. Currently, we describe herein relative comparisons of Amide I, II, and III in BDOextended PU, silk-inspired PU and silk.…”

“…The absorption peak of BDO-extended PU (265 nm) exhibited a slight red shift in wavelength compared with that of Dow BPU (263 nm), while the absorption peak of silk-inspired PU (266 nm) exhibited a farther slight red shift in wavelength compared with that of BDO-extended PU (265 nm). The detailed chemical structures of the tested PU samples have been depicted in the previous report, 32 in which there is no conjugated system other than benzenoid ring. Therefore, UV-Vis absorption peaks of the three PUs are very contiguous.…”

“…The detailed synthesis procedures and the chemical composition of the final PU were illustrated in a previous article. 32 Briefly, the specific chain extender, H-GlyAlaGlyAla-NH(CH 2 ) 6 NH-AlaGlyAlaGly-H, was prepared and purified as described in the earlier literature, 25 using traditional liquid-phase peptide synthesis method. Subsequently, the classical two-step polymerization method 33 was employed to synthesize the silk-inspired PU, using the specific chain extender mentioned above.…”

“…31 Then the silkinspired PU containing GlyAlaGlyAla tetrapeptide was synthesized and its primary structure was qualitatively identified by means of elemental analysis (EA), 1 H nuclear magnetic resonance ( 1 H-NMR) spectroscopy and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). 32 Currently, we describe herein our efforts in investigating its physical properties and hierarchy structure of more importance. Molecular weights were determined by intrinsic viscosity ([g]) method and gel permeation chromatography (GPC), and microstructural analysis was characterized by Fourier transform infrared (FTIR) spectroscopy and ultraviolet-visible (UV-Vis) spectroscopy.…”

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

“…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 .…”