Properties of Biomimetic Artificial Spider Silk Fibers Tuned by PostSpin Bath Incubation.

Gabriele Greco,Nicola M Pugno,Tina Arndt,Andreas Barth,Anna Rising,Jan Johansson,Fredrik G Bäcklund,Benjamin Schmuck,Juanita Francis

doi:10.3390/molecules25143248

Abstract

Efficient production of artificial spider silk fibers with properties that match its natural counterpart has still not been achieved. Recently, a biomimetic process for spinning recombinant spider silk proteins (spidroins) was presented, in which important molecular mechanisms involved in native spider silk spinning were recapitulated. However, drawbacks of these fibers included inferior mechanical properties and problems with low resistance to aqueous environments. In this work, we show that ≥5 h incubation of the fibers, in a collection bath of 500 mM NaAc and 200 mM NaCl, at pH 5 results in fibers that do not dissolve in water or phosphate buffered saline, which implies that the fibers can be used for applications that involve wet/humid conditions. Furthermore, incubation in the collection bath improved the strain at break and was associated with increased β-sheet content, but did not affect the fiber morphology. In summary, we present a simple way to improve artificial spider silk fiber strain at break and resistance to aqueous solvents.

Highlights

In recent decades, spider silks and their extraordinary mechanical and biological properties have gained interest from the scientific community as well as from the industry [1,2,3,4]
We show that the strain at break of biomimetic artificial spider silk fibers can be improved by means of increased incubation time in the collection bath
The immersed roller was left in the bath for fixed periods of time ranging between 1 and 48 h, where after it was removed from the bath, the fibers were collected from the roller, dried in air, and tested for water solubility, as well as characterized by tensile testing using Fourier transform infrared (FTIR) spectroscopy, light microscopy, and scanning electron microscopy (SEM)

Summary

Introduction

Spider silks and their extraordinary mechanical and biological properties have gained interest from the scientific community as well as from the industry [1,2,3,4]. Spiders produce small amounts of silk and they are difficult to farm due to their cannibalistic, predatory, and solitary nature [15] To overcome this problem, production of recombinant silk proteins (spidroins) in heterologous hosts has been seen as a plausible solution that would be beneficial from an environmental point of view [16,17]. Common problems encountered when producing spidroins in these hosts have been low protein yields and premature aggregation during expression, which resulted in aggregated target proteins that required solubilization in harsh solvents such as hexafluoroisopropanol (HFIP) [23,28] Such conditions denatured the proteins and were incompatible with a biomimetic spinning procedure [16]

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Discussion

Conclusion