Synthetic Metals 159 (2009) 1313–1318 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Biocompatible composites of polyaniline nanoﬁbers and collagen Hooi-Sung Kim a,∗ , Hugh L. Hobbs b , Lian Wang a , Michael J. Rutten a , Carl C. Wamser c a Oregon Medical Laser Center, Portland, OR 97225, USA b Department of Chemical Engineering, Oregon State University, Corvallis, OR 97331, USA c Department of Chemistry, Portland State University, Portland, OR 97207, USA article info Article history: Received 15 November 2008 Received in revised form 21 February 2009 Accepted 23 February 2009 Available online 26 March 2009 Keywords: Polyaniline Nanoﬁbers Collagen Composite material Conductive polymer abstract A new hybrid composite material composed of polyaniline nanoﬁbers and collagen was fabricated with various ratios of polyaniline nanoﬁbers in a collagen matrix. The nanoﬁbers were well dispersed in the composite matrix, as conﬁrmed by scanning electron microscopy. The polyaniline nanoﬁber–collagen composite ﬁlm remained electronically conductive, although conductivity decreased signiﬁcantly with decreasing polyaniline in the composite. Conductivity could also be adjusted by dedoping in neutral water and redoping in acid, easily monitored with UV–vis spectroscopy. Flash welding, a technique to fuse polyaniline nanoﬁbers with a pulse of light, did not signiﬁcantly affect the composite, presumably due to the discontinuous nanoﬁber population in the composite matrix; only minor structural changes were observed. Contact angles are relatively high (around 80 ◦ ) and independent of the amount of polyaniline in the composite, suggesting that the dominant surface material in the composite is collagen. Porcine skeletal muscle cells cultured as well on the composite ﬁlms as they did on collagen reference samples, suggesting that the composite material is suitable for biomedical applications. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Polyaniline has attracted attention because of its potential for advanced applications such as sensors [1,2], solar cells [3,4], light- emitting diodes [5], and corrosion protection [6,7]. Polyaniline has also shown biocompatibility in several biological applications [8–10]. The most common form of polyaniline has been as a thin ﬁlm; however it has been a major goal to make polyaniline and other conductive polymers more readily processable. Recently, polyaniline nanoﬁbers have been studied; this produces a stabilized colloidal structure with improved processability. In addition, these nanoﬁbers can be fused together by “ﬂash welding” [11–14]. Appli- cations as sensors have also been tested with promising results [15,16]. Polyaniline nanoﬁbers introduce the opportunity to make different types of materials or products, such as blends with mate- rials having different mechanical properties to create, for example, tubing or ﬂexible ﬁlms. Collagen has been shown to be one of the best materials for biological implants due to its biocompatibility and tensile strength [17–19]. Piza et al. recently proposed a hybrid blended material from a substituted polyaniline and collagen; how- ever, the polymer created from o-ethoxyaniline was never very ∗ Corresponding author at: Oregon Medical Laser Center, Providence Health & Services, 9205 S.W. Barnes Road, Portland, OR 97225, USA. Tel.: +1 503 216 6828; fax: +1 503 216 5256. E-mail address: Hooi-Sung.Kim@providence.org (H.-S. Kim). conductive, whether in collagen or not (conductivities the order of 10 -4 S/cm were reported [20]). In this study, we introduce the preparation and characterization of a hybrid thin ﬁlm created from polyaniline nanoﬁbers dispersed in a collagen matrix, show they can have relatively high electronic conductivities, and show bio- compatibility of the composite material with cell culture. 2. Experimental 2.1. Materials Acid-soluble bovine Achilles tendon Type 1 collagen was obtained from Sigma–Aldrich. Aniline was vacuum distilled to obtain a colorless liquid. All other materials were analytical grade and used as received from Fisher. 2.2. Preparation of PANI–collagen composite Aniline (75.4 mg, 0.81 mmol) was dissolved in 1 M HCl solution (5 mL), and ammonium peroxydisulfate (45.6 mg, 0.20 mmol) was dissolved separately in 1 M HCl solution (5 mL). The two solutions were vigorously mixed together for 1min and placed in a water bath for 1 h at 60 ◦ C. The dark green suspension was sonicated for 5 min, placed in dialysis tubes, and dialyzed against 0.25 mM HCl solution (1 L) until the pH decreased to 2.5–2.6. The excess acid solution was removed to maintain the solution volume at 10mL. Collagen (75 mg) was dissolved in 0.5 M acetic acid (10 mL) by stir- 0379-6779/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2009.02.036