Highly Hydrophobic Films of Engineered Silk Proteins by a Simple Deposition Method

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Langmuir, Volume 39, issue 12
Molecular engineering of protein structures offers a uniquely versatile route for novel functionalities in materials. Here, we describe a method to form highly hydrophobic thin films using genetically engineered spider silk proteins. We used structurally engineered protein variants containing ADF3 and AQ12 spider silk sequences. Wetting properties were studied using static and dynamic contact angle measurements. Solution conditions and the surrounding humidity during film preparation were key parameters to obtain high hydrophobicity, as shown by contact angles in excess of 120°. Although the surface layer was highly hydrophobic, its structure was disrupted by the added water droplets. Crystal-like structures were found at the spots where water droplets had been placed. To understand the mechanism of film formation, different variants of the proteins, the topography of the films, and secondary structures of the protein components were studied. The high contact angle in the films demonstrates that the conformations that silk proteins take in the protein layer very efficiently expose their hydrophobic segments. This work reveals a highly amphiphilic nature of silk proteins and contributes to an understanding of their assembly mechanisms. It will also help in designing diverse technical uses for recombinant silk.
Funding Information: This work was funded by the Academy of Finland through Projects 317019 and 348628, the Center of Excellence Program (2022–2029) in Life-Inspired Hybrid Materials (LIBER) through Project 346105, and the Novo Nordisk Foundation (0061306). The authors thank Dr. Kai Liu for advice in performing dynamic contact angle measurements and Dr. Sesilja Aranko and Yin Yin for cloning the silk constructs. The authors also thank Dr. Julie-Anne Gandier for help with editing the manuscript, Senni Lehtonen for assistance in silk protein expression, and Dmitrii Fedorov for expressing the crystallin protein. The authors acknowledge the provision of facilities and technical support by OtaNano Nanomicroscopy Center (Aalto-NMC) and the Bioeconomy Infrastructure at Aalto University. Publisher Copyright: © 2023 The Authors. Published by American Chemical Society.
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Välisalmi , T , Roas-Escalona , N , Meinander , K , Mohammadi , P & Linder , M B 2023 , ' Highly Hydrophobic Films of Engineered Silk Proteins by a Simple Deposition Method ' , Langmuir , vol. 39 , no. 12 , pp. 4370–4381 . https://doi.org/10.1021/acs.langmuir.2c03442