Silk fibroin–polyurethane blends: Physical properties and effect of silk fibroin content on viscoelasticity, biocompatibility and myoblast differentiation Hyung-seok Park a,b , Myoung-Seon Gong a , Jeong-Hui Park a , Sung-il Moon b , Ivan B. Wall a,d , Hae-Won Kim a,e , Jae Ho Lee a,⇑ , Jonathan C. Knowles a,c,⇑ a Department of Nanobiomedical Science & WCU Research Center, Dankook University Graduate School, Cheonan 330-714, South Korea b Development Group 2, Uiwang R&D Center, Samsung Cheil Industries Inc., Gyeonggi-do 437-801, South Korea c Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, 256 Gray’s Inn Road, London WC1X 8LD, UK d Department of Biochemical Engineering, University College London, Torrington Place, London WC1E 7JE, UK e Institute of Tissue Regeneration Engineering (ITREN), Dankook University Graduate School, Cheonan 330-714, South Korea article info Article history: Received 7 March 2013 Received in revised form 4 July 2013 Accepted 11 July 2013 Available online 24 July 2013 Keywords: Silk Polyurethane Viscoelasticity Myogenesis Biocompatibility abstract As a way to modify both the physical and biological properties of a highly elastic and degradable poly- urethane (PU), silk fibroin (SF) was blended with the PU at differing ratios. With increasing SF content, the tensile strength decreased as did the strain at break; the stiffness increased to around 35 MPa for the highest silk content. C2C12 (a mouse myoblast cell line) cells were used for in vitro experiments and showed significantly improved cell responses with increasing SF content. With increasing SF content the number of non-adherent cells was reduced at both 4 and 8 h compared to the sample with the lowest SF content. In addition, muscle marker genes were upregulated compared to the sample containing no SF, and in particular sarcomeric actin and a-actin. Crown Copyright Ó 2013 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved. 1. Introduction Tissue engineering methods are being developed as a means to replace damaged or diseased organs. This approach uses tissue- specific cells, which are grown on a scaffold material with the pur- pose of creating a functional tissue or organ. Many different com- pounds are being studied for use as scaffolds in tissue engineering. These include both synthetic and natural materials [1]. Recently natural polymers have been studied as resources due to their unique properties including non-toxicity, biodegradability and biocompatibility. However, natural homopolymers by them- selves are inadequate to meet the diversity of demands for bioma- terials and do not offer the opportunity for property-tuning via modulation of the chemistry. In order to improve the performance of individual natural polymers, many blends have been developed, such as silk fibroin (SF) with calcium phosphate cements [2] and blends of two or more degradable polymers [3]; chitosan [4], hya- luranon [5] and poly(vinyl alcohol) [6] blends, amongst others, have been prepared using solution blending methods. Synthetic biocompatible/biodegradable polymers have good potential for clinical use as control over their degradation rate and mechanical properties may be accomplished for a particular application [7]. These polymers are especially useful in biomedical approaches due to their potential ability to enable migration, cell adhesion, differentiation and proliferation [8,9], as well as their temporary nature. These polymers could also be implanted in the human body by injection, having potential applications in the areas of gene delivery, sustained drug delivery and tissue engineering [10]. Polyurethanes (PUs) can be fabricated via reaction between dialcohols and diisocyanates forming urethane linkages [11]. There are many methods for manufacturing PUs, either with or without the use of organic solvents. The most widely used approach the one-shot process, where direct mixing of monomers and catalysts and other additives is carried out [12]. Recently, many papers on biodegradable PUs have appeared [13]; PUs are a class of biode- gradable polymers that have been applied as tissue-engineering scaffolds as they show low cytotoxicity in vitro and in vivo [14– 18]. 1742-7061/$ - see front matter Crown Copyright Ó 2013 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved. http://dx.doi.org/10.1016/j.actbio.2013.07.013 ⇑ Corresponding authors at: Department of Nanobiomedical Science & WCU Research Center, Dankook University Graduate School, Cheonan 330-714, South Korea and Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, 256 Gray’s Inn Road, London WC1X 8LD, UK. Tel.: +44 0203456 1189. E-mail address: j.knowles@ucl.ac.uk (J.C. Knowles). Acta Biomaterialia 9 (2013) 8962–8971 Contents lists available at ScienceDirect Acta Biomaterialia journal homepage: www.elsevier.com/locate/actabiomat