Chemical and topographical modification of PHBV surface to promote osteoblast alignment and confinement H. Kenar, 1 A. Kocabas, 2 A. Aydinli, 2 V. Hasirci 1 1 METU, BIOMAT, Department of Biological Sciences, Biotechnology Research Unit, Ankara, Turkey 2 Department of Physics, Bilkent University, Ankara 06800, Turkey Received 10 January 2007; revised 21 June 2007; accepted 4 July 2007 Published online 28 September 2007 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jbm.a.31638 Abstract: Proper cell attachment and distribution, and thus stronger association in vivo between a bone implant and native tissue will improve the success of the implant. In this study, the aim was to achieve promotion of attach- ment and uniform distribution of rat mesenchymal stem cell-derived osteoblasts by introducing chemical and topo- graphical cues on poly(3-hydroxybutyrate-co-3-hydroxyval- erate) (PHBV) film surfaces. As the chemical cues, either alkaline phosphatase was covalently immobilized on the film surface to induce deposition of calcium phosphate minerals or fibrinogen was adsorbed to improve cell adhe- sion. Microgrooves and micropits were introduced on the film surface by negative replication of micropatterned Si wafers. Both chemical cues improved cell attachment and even distribution on the PHBV films, but Fb was more effective especially when combined with the micropatterns. Cell alignment (<108 deviation angle) parallel to chemi- cally modified microgrooves (1, 3, or 8 lm groove width) and on 10 lm-thick Fb lines printed on the unpatterned films was achieved. The cells on unpatterned and 5 lm- deep micropitted films were distributed and oriented randomly. Results of this study proved that microtopogra- phies on PHBV can improve osseointegration when com- bined with chemical cues, and that microgrooves and cell adhesive protein lines on PHBV can guide selective osteo- blast adhesion and alignment. Ó 2007 Wiley Periodicals, Inc. J Biomed Mater Res 85A: 1001–1010, 2008 Key words: PHBV; photolithography; micropatterned films; osteoblasts; bone tissue engineering INTRODUCTION Bone tissue engineering is becoming more promis- ing for the replacement or repair of damaged bone because advanced techniques such as micro and nanotechnology are now being used more exten- sively to form tissues that closely mimic the micro- structure and function of the natural tissue. Biodegradable polymers are considered to be the most suitable materials for scaffold preparation because of their variety, versatility, and biodegrad- ability. When applied, these materials circumvent the need for device removal from the body. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is one of the naturally derived biodegradable poly- mers that has improved processing and mechanical properties with respect to PHB, 1,2 which is brittle and has a higher melting temperature. 3 Properties of PHBV such as glass transition temperature (T g ), sta- bility, degradability, and crystallinity can be mo- dified by changing its copolymer composition and molecular weight. 4–6 Therefore, the rate and extent of accumulation of degradation products, such as b- hydroxybutyric acid, which is a normal constituent of blood, 7–9 and hydroxyvaleric acid, at the site of implantation is not problematic for PHBV, unlike the faster degrading a-polyhydroxy acids of the poly- lactide family. PHBV can be processed to take on various shapes, forms, and porosities because its ther- moplastic properties are suitable. Studies on using PHBV for bone tissue implants involved attempts to match the mechanical strength and form to that of bone through incorporation of minerals. 10,11 It can therefore be assumed that PHBV has a significant potential for use as a support for long-term bone regeneration in vivo. More recently, in vitro growth of osteoblasts on macroporous, three-dimensional PHBV matrices has been reported. 12 Suitability of the matrices for bone tissue engineering was shown by an increase in osteocalcin expression and alkaline Correspondence to: V. Hasirci; e-mail: vhasirci@metu.edu.tr Contract grant sponsor: Scientific and Technical Research Council of Turkey (TUBITAK) TBAG; contract grant number: 2288 Contract grant sponsor: METU Graduate School of Natu- ral and Applied Sciences; contract grant number: BAP- 2004-07-02-00-15 Ó 2007 Wiley Periodicals, Inc.