Biomaterials 24 (2003) 4621–4629 Reduced mouse ﬁbroblast cell growth by increased hydrophilicity of microbial polyhydroxyalkanoates via hyaluronan coating Ya-Wu Wang, Qiong Wu*, Guo-Qiang Chen Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China Received 5 January 2003; accepted 13 May 2003 Abstract The mouse ﬁbroblast cell line L929 was inoculated on 3D scaffolds of microbial polyesters, namely polyhydroxybutyrate (PHB) and poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) to evaluate their in vitro biocompatibility. It was found that both polyhydroxyalkanoates (PHA) subjected to lipase treatment and hyaluronan (HA) coating decreased the contact angle of water to the material surface approximately 30%, meaning an increased hydrophilicity on the PHA surface. At the same time, both the lipase treatment and the HA coating smoothened the PHA surface. After the lipase treatment or HA coating, the ratio of PHA hydrophilic groups including hydroxyl and carboxyl to carbonyl of PHA was approximately 1:1 or 2:1. Cells grown on scaffolds treated with lipase were approximately 4  10 5 /ml, twice in number of the control. However, PHA scaffolds coated with HA were observed with a 40% decrease in cell growth compared with that of the control. HA coating reduced the cell attachment and proliferation on PHA although the materials had increased hydrophilicity. In comparison, lipase treatment promoted the cell growth on PHA although the treatment did not lead to better hydrophilicity compared with HA coating. It appeared that an appropriate combination of hydrophilicity and hydrophobicity was important for the biocompatibility of PHBHHx, especially for the growth of L929 cells on the surface of this material. This may have instructive signiﬁcance for biomaterial selection and design. r 2003 Elsevier Ltd. All rights reserved. Keywords: Polyhydroxyalkanoates; L929; Hyaluronan; PHB; Surface coating 1. Introduction The material surface properties will inﬂuence the initial cellular events on the cell–material interface. It is clear from a number of studies that the surface properties will determine which biological molecules will adsorb [1]. There are some aspects that will inﬂuence the material biocompatibilities, including surface rough- ness, surface chemistry, and surface energy [2–9]. Polyhydroxyalkanoates (PHA) is a family of biopo- lyesters synthesized by many bacteria [10–12]. Studies were conducted using polyhydroxybutyrate (PHB) as biomaterial for in vitro and in vivo studies, results showed various degrees of biocompatibility and biode- gradability [13,14]. The application of PHA as bioma- terials will add values to this novel biopolymer [15]. Yang et al. compared the biocompatibility of PHB, PHBHHx,theirblendsandpolylacticacid(PLA)invitro prior to and after the surface treatment with lipases and NaOH, respectively. They found that the growth of the cells L929 was poorer on PHB and PLA ﬁlms compared with that of the more hydrophobic PHBHHx [16]. At the same time, the biocompatibility was improved in various degrees when these polymers were treated with lipases [16]. Other research also showed that the surface properties of a biomaterial, especially hydrophilicity, inﬂuenced cell adhesion and proliferation on the materials [17–20]. Hyaluronic acid (HA), a linear polysaccharide con- sisting of alternating 1,4-linked units of 1,3-linked glucuronic acid and N-acetylglucosamine, is one of several glycosaminoglycan components of the extracel- lular matrix (ECM), the synovial ﬂuid of joints, and the scaffolding comprising cartilage [21]. According to the structure of HA, it is obvious highly hydrophilic because of its abundance of hydroxyl and carboxyl groups. Our ARTICLE IN PRESS *Corresponding author. Tel: +86-10-62771664; fax: +86-10- 62788784. E-mail address: wuqiong@mail.tsinghua.edu.cn (Q. Wu). 0142-9612/03/$-see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0142-9612(03)00356-9