Mimicking the Extracellular Matrix: Tuning the Mechanical Properties of Chondroitin Sulfate Hydrogels by Copolymerizatio
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Mimicking the Extracellular Matrix: Tuning the Mechanical Properties of Chondroitin Sulfate Hydrogels by Copolymerization with Oligo(ethylene glycol) Diacrylates Anahita Khanlari1 ([email protected]) Tiffany C. Suekama1 ([email protected]) Michael S. Detamore1 ([email protected]) Stevin H. Gehrke1 ([email protected]) 1 Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS 66045, United States ABSTRACT Chondroitin sulfate (CS) is one of the major glycosaminoglycans (GAGs) present in the connective tissue extracellular matrix (ECM) and is responsible for the regulation of cellular activities as well as providing mechanical support for the surrounding tissue. Due to presence of CS in the natural tissues including cartilage, hydrogels of CS and other GAGs have been widely used in cartilage regeneration. Due to their polyelectrolyte nature, GAG-based hydrogels are brittle and require modifications to overcome the weak mechanical properties. In this work, we showed copolymerization of methacrylated chondroitin sulfate with oligo(ethylene glycol)s improved the crosslink density of the gels from 2 to 20 times depending on the methacrylation degree of CS and length of the crosslinking monomer. Copolymerization of CS with oligo(ethylene glycol) acrylates is a method to design hydrogels with tunable swelling and mechanical properties. INTRODUCTION Hierarchically ordered biomimetic materials are used in tissue engineering to replace the natural extracellular matrix (ECM) in cartilage regeneration applications. Either naturally available or synthetic biocompatible components are used in these ECM mimetic materials. In the natural tissue glycosaminoglycans (GAGs) are parts of aggrecan which have been extensively studied to mimic the ECM. First, GAGs are actively involved in cell signaling [1]. They are bioresorbable and because of multiple hydroxyl and carboxyl groups in their structures, they have versatility in their crosslinking chemistry. Two major GAGs, hyaluronic acid (HA) and chondroitin sulfate (CS) (shown in Figure 1) are used, in particular, to replicate ECM [2-4]. Hydrogels are excellent candidates for an ECM-mimicking material because similar to the ECM, hydrogels can be porous materials with over 80% water in their structure [5,6]. Hydrogels can be designed to degrade by incorporation of degradable moieties [7]. Spatial control over the hydrogel matrix can be used to initially create mechanically robust scaffolds while temporal control of the gels through degradation can assist tissue formation in the place of degrading scaffold [8]. In our present work, mechanical properties of hydrogels synthesized from natural CS and synthetic oligo(ethylene glycol) acrylate are investigated. In hydrogel syntheses, photopolymerization is a commonly used technique to shape 3D matrices. To take advantage of photopolymerization with fast reaction kinetics and to produce
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hydrogels from polysaccharide biopolymers, functionalization of polysaccharides with reactive groups is common. In particular, function
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