Porous scaffold of gelatin–starch with nanohydroxyapatite composite processed via novel microwave vacuum drying Jaya Sundaram * , Timothy D. Durance, Rizhi Wang University of British Columbia, 2205 East Mall, Vancouver, BC, Canada V6T 1Z4 Received 2 August 2007; received in revised form 17 January 2008; accepted 25 January 2008 Available online 14 February 2008 Abstract Hydroxyapatite (HA) is a fundamental mineral-based biomaterial, used for preparing composites for bone repair and regeneration. Gelatin blended with starch results in scaffold composites with enhanced mechanical properties. A gelatin–starch blend reinforced with HA nanocrystals (nHA) gave biocompatible composites with enhanced mechanical properties. In this study, a porous scaffold of gelatin– starch–nHA composites was fabricated through microwave vacuum drying and crosslinking using trisodium citrate. Three different com- posite scaffolds were prepared at three different percentages of nHA: 20%, 30% and 40%. The microstructures and compositions of the composites were analyzed. Within the porous structure, the nHA crystals were observed to precipitate. The interaction between the gel- atin–starch network film and nHA crystalline material was studied using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction analysis (XRD). XRD reflections showed that there are two different minerals present in the scaffold composite. There were strong reflection peaks close to the 26° and 32° 2h angles of HA, and close to the 8° and 49° 2h angles for sodium citrate minerals. The FTIR result suggested that carboxyl groups, C@O and amino groups play crucial roles in HA formation on the surface of a gelatin network. Ó 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Nanohydroxyapatite; Gelatin; Starch; Microwave vacuum drying; Porous scaffold composite 1. Introduction Biomaterials for clinical orthopaedics need to be biode- gradable, and induce and promote new bone formation by osteogenic cells at a required site. They should be in the form of porous scaffolds, which provide space for hard tis- sue development and also provide temporary mechanical support. The extracellular matrices of hard tissue are com- posed of both organic and inorganic phases. The inorganic phase consists of hydroxyapatite (HA) crystals and the organic phase consists of type I collagen and small amounts of glycosaminoglycans, proteoglycans and glyco- proteins. Biomaterials used for scaffolds play an important role in tissue regeneration, acting as, for example, support cells and growth factor carriers, and controlling the release of growth factors [1,2]. Therefore, the biomaterials used for tissue engineering scaffolds should meet certain require- ments. They should have high porosity to provide sufficient space and surface for cell seeding and should not allow any of the seeded cells to diffuse into the surrounding tissue following implantation. Furthermore, the porous scaffold biomaterials should be completely degradable and elimin- atable from the body, as these artificial supports are only needed temporarily [3–5]. Gelatin is a denatured form of collagen and contains a number of biological functional groups such as amino acids, making it suitable for hard tis- sue applications. Gelatin is also clinically proven as a tem- porary defect filler and wound dressing because of its biodegradability and cytocompatibility [6–8]. The hydrogel and plasticity properties of gelatin help to carry and deliver drugs. However, the mechanical properties of gelatin are not satisfactory for hard tissue applications. 1742-7061/$ - see front matter Ó 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actbio.2008.01.019 * Corresponding author. Tel.: +1 604 788 1139; fax: +1 604 822 5143. E-mail address: jayas@interchange.ubc.ca (J. Sundaram). Available online at www.sciencedirect.com Acta Biomaterialia 4 (2008) 932–942 www.elsevier.com/locate/actabiomat