Biodegradable hydrogels based on novel photopolymerizable guar gum–methacrylate macromonomers for in situ fabrication of tissue engineering scaffolds Ashutosh Tiwari a , Jamison J. Grailer b , Srikanth Pilla a , Douglas A. Steeber b , Shaoqin Gong a,c, * a Department of Mechanical Engineering, University of Wisconsin-Milwaukee, 3200 North Cramer Street, Milwaukee, WI 53211, USA b Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA c Department of Materials, University of Wisconsin-Milwaukee, 3200 North Cramer Street, Milwaukee, WI 53211, USA Received 25 February 2009; received in revised form 8 May 2009; accepted 1 June 2009 Available online 6 June 2009 Abstract Guar gum (GG) is a non-ionic polysaccharide that is found abundantly in nature and has many properties desirable for biomedical applications. In the present work GG with molecular weights ranging from 74 to 210 kDa was modified with glycidyl methacrylate (GMA) to produce a series of water-soluble photopolymerizable guar gum–methacrylate (GG–MA) macromonomers of different molec- ular weights. We investigated the effects of molecular weight of GG–MA macromonomers from 102 to 216 kDa and with percent degree of methacrylation (%DM) ranging from 14% to 56% on the properties of GG–MA hydrogels. GG–MA hydrogels exhibited a three- dimensional open cell microstructure with an average pore size ranging from 10 to 55 lm and an average pore density of from 2.4  10 6 to 8.6  10 7 pores cm 3 . The hydrogels exhibited equilibrium swelling ratios ranging from 22% to 63%. The degree of in vitro enzymatic biodegradation of the hydrogels decreased linearly with increasing gel content and the degree of methacrylation of the respective macromonomers. The human endothelial cell line EA.hy926 was photo-encapsulated in the GG–MA hydrogels. Cells remained viable at low macromonomer concentrations, but cell viability decreased sequentially as the macromonomer concentration increased. GG–MA hydrogels with a 0.05 wt.% GG–MA macromonomer concentration revealed excellent endothelial cell proliferation, similar to that of the Matrigel TM control. Ó 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Guar gum–methacrylate; Photopolymerizable macromonomer; Biodegradable hydrogels; Cytocompatibility; Tissue engineering scaffold 1. Introduction Hydrogels derived from biomacromolecules such as polysaccharides have emerged as promising scaffolding materials for tissue engineering applications owing to their three-dimensional porous structure, biodegradability and biocompatibility, ability to imbibe a large amount of water, as well as biological fluids, and good mechanical integrity [1–7]. Such hydrogels can typically offer positive interac- tions with cells. Although a number of hydrogels have been explored as scaffolding materials for cartilage, corneal and heart valve tissue engineering applications using a range of ionic poly- saccharides, such as chitosan, alginate, hyaluronic acid and other glycosaminoglycans [8–11], certain limitations exist with ionic hydrogels due to the nature of the ionizable groups [12]. The dynamic swelling equilibrium of ionic hydrogels is closely related to pH, ionic strength, tempera- ture and composition of the external solutions. Since ionic hydrogels are pH responsive, they may form biologically stable ionic networks due to the strong ionic interaction. 1742-7061/$ - see front matter Ó 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actbio.2009.06.001 * Corresponding author. Address: Department of Mechanical Engineer- ing, University of Wisconsin-Milwaukee, 3200 North Cramer Street, Milwaukee, WI 53211, USA. Tel.: +1 414 229 5946; fax: +1 414 229 6958. E-mail address: sgong@uwm.edu (S. Gong). Available online at www.sciencedirect.com Acta Biomaterialia 5 (2009) 3441–3452 www.elsevier.com/locate/actabiomat