Mammary epithelial cell adhesion, viability, and infiltration on blended or coated silk fibroin–collagen type I electrospun scaffolds Yas Maghdouri-White a,b , Gary L. Bowlin c , Christopher A. Lemmon b , Didier Dréau a a Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223 USA b Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284 USA c Department of Biomedical Engineering, University of Memphis, Memphis, TN 38152 USA abstract article info Article history: Received 20 January 2014 Received in revised form 2 June 2014 Accepted 30 June 2014 Available online 8 July 2014 Keywords: Silk fibroin Type I collagen Cell adhesion Cell viability Mechanical properties Electrospun scaffolds Interactions between cells and the extracellular matrix (ECM) play a crucial role in regulating biological tissue function. Silk biomaterials from Bombyx mori (B. mori) silkworm silk are widely used in tissue engineering. As this silk fibroin (SF) contains no strong adhesion sites, we assessed whether the blending or coating of SF with collagen would further improve SF biocompatibility, in part through the addition of the specific integrin recogni- tion sequences. In the present study, electrospun scaffolds were developed by blending 7% SF and 7% type I col- lagen solutions at ratios of 100:0 (pure SF), 95:5, 90:10, and 85:15 (SF:collagen, v/v) prior to electrospinning. Pure SF scaffolds were further coated with collagen type I. The physical and mechanical properties of these scaf- folds and MCF10A mammary epithelial cell adhesion, viability, and infiltration into these blended or coated SF– collagen (SF–C) scaffolds were determined. The blending of SF with collagen decreased average pore sizes and fiber diameters of the electrospun scaffolds regardless of the ratio (p b 0.01). The mechanical strength of these scaffolds did not change in their hydrated state (ns), but was decreased for 85:15 SF–C blended scaffolds in the dry state (p b 0.05). The adhesion of MCF10A cells was significantly increased in SF–C blended or coated scaffolds compared to pure SF scaffolds (p b 0.01). MCF10A cell viability and infiltration on SF–C coated scaffolds were sig- nificantly higher compared to all other conditions tested (p b 0.01). © 2014 Elsevier B.V. All rights reserved. 1. Introduction Interactions between cells and the ECM critically define the biologi- cal microenvironment, and thus play a crucial role in regulating homeo- stasis and tissue specificity [1]. Fundamental cellular events, including proliferation, migration and apoptosis, are regulated by the cellular con- text [2]. In vitro three-dimensional (3D) cell cultures mimicking these physiological cell–ECM interactions provide a microenvironment closer to biological tissue than conventional two-dimensional (2D) cell cul- tures [1,3]. As scaffolds for tissue engineering, natural or synthetic poly- mers, electrospun into non-woven fibers led to the generation of tissue- like structures that closely resemble collagen fibers in the ECM [4]. Among the natural biodegradable polymers available, such as collagen, gelatin, chitosan and silk fibroin (SF), silk-based biomaterials offer sig- nificant advantages for tissue engineering applications [5,6]. Indeed, silk-based biomaterials have excellent mechanical properties, controlla- ble biodegradability, hemostatic properties, low antigenicity, non- inflammatory characteristics [5], high permeability to oxygen and drugs, and resistance to enzymatic cleavage [7]. Silk consists of two types of proteins: SF, which is a filament core protein, and sericins, the members of a glue-like coating family of hy- drophilic proteins that hold two fibroin fibers together [5,8]. Sericins have been shown to decrease biocompatibility and increase hypersensitivity to silk; however when removed, biocompatibility of SF was comparable to other biomaterials [9]. SF has been used as a bio- material in various forms such as films [5,8], membranes [5,8], gels [5], sponges [5,8], powders, scaffolds [5], fibers, nets, meshes, and yarn [8]. The native Bombyx mori SF protein contains no RGD sequence, a recog- nized binding site for integrin-mediated cell adhesion [10–13]. Cell ad- hesion to this biomaterial has been attributed to alternative low-affinity cell binding domains [13] such as arginine residues that are present in the non-repetitive region near the carboxy-terminus [7], or electrostatic interactions between cells and silk [13]. The cell attachment and early stages of cell–matrix interactions to B. mori SF can be enhanced by mod- ifying the SF biomaterial surface through coating or chemical coupling with the RGD peptide sequence or specific growth factors [8,13–16]. In- troducing the fibronectin cell-adhesive sequence, RGD, onto the SF bio- material enhanced cell attachment to this material [16,17]. Increased attachment and growth of endothelial cells were obtained when SF nets were coated with gelatin, fibronectin, or collagen type I [16]. Human bone marrow stromal cells (BMSCs) and human ACL fibroblasts showed higher cell attachment, spreading, and proliferation on RGD- modified SF matrices and silk films [13]. Although SF products (microfibers, nano-fibers, and films) coated with laminin increased human keratinocyte spreading, keratinocyte attachment was not al- tered [18]. Altman et al. also demonstrated that SF films coated with Materials Science and Engineering C 43 (2014) 37–44 http://dx.doi.org/10.1016/j.msec.2014.06.037 0928-4931/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec