www.elsevier.com/locate/jmbbm Available online at www.sciencedirect.com Research Paper Effects of alginate hydrogel cross-linking density on mechanical and biological behaviors for tissue engineering Jinah Jang a , Young-Joon Seol 1,b , Hyeon Ji Kim b , Joydip Kundu b,2 , Sung Won Kim c,d , Dong-Woo Cho b,n a Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Nam-gu, Pohang, Kyungbuk, 790-784, South Korea b Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Nam-gu, Pohang, Kyungbuk, 790-784, South Korea c Department of Otolaryngology-Head and Neck Surgery, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701, South Korea d Department of Biomedical Science, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701, South Korea article info Article history: Received 7 February 2014 Received in revised form 1 May 2014 Accepted 4 May 2014 Available online 14 May 2014 Keywords: Alginate Tissue engineering Hydrogel Structure-properties relations Cross-linking abstract An effective cross-linking of alginate gel was made through reaction with calcium carbonate (CaCO 3 ). We used human chondrocytes as a model cell to study the effects of cross-linking density. Three different pore size ranges of cross-linked alginate hydrogels were fabricated. The morphological, mechanical, and rheological properties of various alginate hydrogels were characterized and responses of biosynthesis of cells encapsulated in each gel to the variation in cross-linking density were investigated. Desired outer shape of structure was maintained when the alginate solution was cross-linked with the applied method. The properties of alginate hydrogel could be tailored through applying various concentrations of CaCO 3 . The rate of synthesized GAGs and collagens was significantly higher in human chondrocytes encapsulated in the smaller pore structure than that in the larger pore structure. The expression of chondrogenic markers, including collagen type II and aggrecan, was enhanced in the smaller pore structure. It was found that proper structural morphology is a critical factor to enhance the performance and tissue regeneration. & 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jmbbm.2014.05.004 1751-6161/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ82 54 279 5889. E-mail addresses: jinahjang@postech.ac.kr (J. Jang), yseol@wakehealth.edu (Y.-J. Seol), ghj901017@postech.ac.kr (H.J. Kim), joydip15@gmail.com (J. Kundu), kswent@catholic.ac.kr (S.W. Kim), dwcho@postech.ac.kr (D.-W. Cho). 1 Present address: Wake Forest Institute for Regenerative Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA. 2 Present address: Department of Chemical Engineering, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA. journal of the mechanical behavior of biomedical materials 37 (2014) 69–77