Fabrication of conductive electrospun silk fibroin scaffolds by coating with polypyrrole for biomedical applications Salvador Aznar-Cervantes a , Maria I. Roca b , Jose G. Martinez b , Luis Meseguer-Olmo c , Jose L. Cenis a , Jose M. Moraleda c , Toribio F. Otero b, ⁎ a Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (IMIDA), La Alberca (Murcia), E-30150, Spain b Group for Electrochemistry, Intelligent Materials and Devices (GEMDI), Universidad Politécnica de Cartagena, ETSII, Cartagena (Murcia), E-30203, Spain c Cell Therapy Unit & Orthopedic Surgery Service. University Hospital V. Arrixaca, El Palmar (Murcia), E-30150, Spain abstract article info Article history: Received 29 April 2011 Received in revised form 22 November 2011 Accepted 26 November 2011 Available online 8 December 2011 Keywords: Fibroin-polypyrrole meshes Electroactivity Anion storage Human fibroblast Adult human mesenchymal stem cells Scaffolds constituted by micro and nanofibers of silk fibroin were obtained by electrospinning. Fibers of fibroin meshes were coated with polypyrrole (pPy) by chemical polymerization; chemical linkages between polymers were observed by SEM and IR spectroscopy. Mechanical resistance of the meshes was improved by polypyrrole coating. Furthermore, coated meshes present a high electroactivity allowing anion storage and delivery during oxidation/reduction reactions in aqueous solutions. Uncoated and pPy coated materials support the adherence and proliferation of adult human mesenchymal stem cells (ahMSCs) or human fibroblasts (hFb). The bioactivity of fibroin mesh overcomes that of the polypyrrole coated meshes. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Scaffolds for cellular growth made of silk fibroin (SF) demonstrate diverse applications in the field of tissue engineering [1]. SF is highly biocompatible and able to support appropriate cellular activity without eliciting rejection, inflammation or immune activation in the host [2–5]. SF structure is porous allowing the growing of cells, the exchange of nutrients and growth factors and the production of extracellular matrix (ECM) to enable communication between the cells. SF has been studied for tissue engineering in blood vessels [3,6], skin [5,7], bone [8,9] and cartilage [10]. Fibroin is extremely versatile and can be processed in very different formats, adequate for different tissue engineering needs. Fibroin cellular scaffolds can be constructed predominantly as hydrogels, 3-D sponges and mats of nanofibers obtained by electrospinning [1,11]. Nanofiber- based scaffolds are created through electrospinning with wide applications in biomedicine. Typical electrospinning setup consists of three components: a high voltage supplier, a capillary needle, and a grounded collector. During electrospinning, an electric potential is applied to a jet of a polymer solution, usually delivered with a syringe pump [12]. Electrohydrodynamic forces produced by charges in the polymer jet as well as the attractive forces between the liquid and the collector work together to exert tensile forces on the solution. Resulting in a thinning of the polymer jet to transverse sizes in the nanometer and micrometer range, which is collected in a metallic plate as a random non woven mat. The physical configuration of this mat mimics the extracellular matrix of animal tissues; and this is the reason of the excellent performance of these structures as cellular scaffolds. Numerous composite nanofibers and functionalized electrospun silk matrices have been developed in the last years including: Park et al. successfully produced chitin/silk fibroin blend fibers [13], collagen/silk fibroin solutions in HFIP were electrospun by Yeo et al. [14], Wang et al. encapsulated a silk fibroin core fiber within a poly (ethylene oxide) shell fiber [15] and Li et al. [16] added bone morphogenetic protein-2 (BMP-2) into silk fibroin nanofibers mixing it into the spinning solution and Liu et al. [17] immobilized glucose oxidase in a composite membrane of regenerated silk fibroin and poly(vinyl alcohol) for sensing applications. Electrospun mats of silk fibroin as well as other polymeric biomate- rials are satisfactory for a high number of tissue engineering applications. The field of potential applications could be highly expanded by fabricating electrospun mats with conductive properties. Scaffolds consisting of conducting polymers have application in biosensing, controlled drug delivery and tissue engineering with improved cellular growth [18,19]. Conductive electrospun nanofiber mats are constructed by two approaches: the first would be direct electrospinning of the conducting polymer, as was made with polypyrrole by Chronakis et al. [20]; however, little information exists regarding the reabsorption of this material when fabricating implantable devices. Secondly, an electrospun mat of a well known biocompatible and reabsorbable biomaterial is made and then Bioelectrochemistry 85 (2012) 36–43 ⁎ Corresponding author. Tel.: + 34 968325519; fax: + 34 968325915. E-mail address: toribio.fotero@upct.es (T.F. Otero). 1567-5394/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.bioelechem.2011.11.008 Contents lists available at SciVerse ScienceDirect Bioelectrochemistry journal homepage: www.elsevier.com/locate/bioelechem