Native-like Flow Properties of an Artificial Spider Silk Dope.

Tina Arndt,Chris Holland,Anna Rising,Jan Johansson,Peter R Laity

doi:10.1021/acsbiomaterials.0c01308

Abstract

Recombinant spider silk has emerged as a biomaterial that can circumvent problems associated with synthetic and naturally derived polymers, while still fulfilling the potential of the native material. The artificial spider silk protein NT2RepCT can be produced and spun into fibers without the use of harsh chemicals and here we evaluate key properties of NT2RepCT dope at native-like concentrations. We show that NT2RepCT recapitulates not only the overall secondary structure content of a native silk dope but also emulates its viscoelastic rheological properties. We propose that these properties are key to biomimetic spinning and that optimization of rheological properties could facilitate successful spinning of artificial dopes into fibers.

Highlights

The extreme toughness of spider silk, combined with properties like biological degradability and biocompatibility, make it a highly attractive material for a wide variety of technical and medical applications.[1,2] In order to make this material reproducible, available, and economical, industrialscale production of spider-silk mimics are best produced recombinantly, where silk proteins are expressed in heterologous hosts, purified, and subsequently spun into fibers.we are faced with a challenge; the vast majority of available protocols for spidroin production include the use of denaturing agents during purification and/or coagulation baths during spinning.[3]
Having already demonstrated that it may be spun under conditions similar to those of natural silk fibers, we explore the properties of NT2RepCT spinning dope using rheology, circular dichroism (CD) spectroscopy and Fourier transform infrared (FTIR) spectroscopy
While considerable sample-to-sample variation was evident, the NT2RepCT specimens showed a weak correlation between concentration and increased viscosity, which became more pronounced above 300 mg mL−1 (Figure 1A)

Summary

Introduction

We are faced with a challenge; the vast majority of available protocols for spidroin production include the use of denaturing agents during purification and/or coagulation baths during spinning.[3] These conditions may be incompatible with the native protein conformation and will likely result in fibers with a molecular structure that differs from that of the native fiber.[4]. There are seven types of glands, of which the major ampullate gland and the fiber it produces, the dragline silk, are most extensively studied.[4−7] Prior to spinning the spidroins contained within major ampullate glands are stored at very high concentrations and near neutral pH (30−50% w/v, > 6.3 pH) as a soluble, transparent and viscous substance (dope).[6,8] As the dope passes through the gland into the spinning duct the microenvironment is significantly altered, i.e., the pH decreases to at least 5.7, the salt concentration changes and shear stress and pulling forces act on the proteins.[8−12] Together, these factors induce fiber formation where the proteins’ secondary structures transition from being predominantly α-helices and random coils to the ordered β-sheet-rich structures observed in the fiber.[12−18]

Results

Discussion

Conclusion