Rheological Characterization of Alginate Based Hydrogels for Tissue Engineering
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Rheological Characterization of Alginate Based Hydrogels for Tissue Engineering Pengfei Duan*1,2, Nehir Kandemir*1, Jiajun Wang1, Jinju Chen1† 1 School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne, UK 2 School of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle upon Tyne, UK *These two authors contribute equally to this manuscript. †Corresponding author: E-mail: [email protected] ABSTRACT Hydrogels have been widely used in many applications from tissue engineering to drug delivery systems. For both tissue engineering and drug delivery, the mechanical properties are important because they would affect cell-materials interactions and injectability of drugs encapsulated in hydrogel carriers. Therefore, it is important to study the mechanical properties of these hydrogels, particularly at physiological temperature (37°C). This study adopted strain sweep and frequency sweep rotational rheological tests to investigate the rheological characteristics of various tissue engineering relevant hydrogels with different concentrations at 37°C. These hydrogels include alginate, RGD-alginate, and copolymerized collagen/alginate/fibrin. It has revealed that the addition of RGD has negligible effect on the elastic modulus and viscosity of alginate. Alginate gels have demonstrated shear thinning behavior which indicates that they are suitable candidates as carriers for cells or drug delivery. The addition of collagen and fibrin would reinforce the mechanical properties of alginate which makes it a strong scaffold material. INTRODUCTION Hydrogels are water-swollen, crosslinked polymeric structures with covalent bonds from the reaction of one or more co-monomers, physical crosslinks from chain entanglements, and hydrogen bonds and van der Waals interactions between chains or crystallites combining macromolecular chains [1]. Among various hydrogels, alginate and collagen have been widely used for tissue engineering [2, 3]. Obtained from brown algae, alginate is a well-known biomaterial widely used in drug delivery applications and in tissue engineering because of its biocompatibility, low toxicity, relative low cost and, simple gelation with divalent cations [4, 5, 6]. To improve the capability of tissue regeneration, alginate gel is often covalently modified with peptides containing the amino acid sequence of arginine-glycine-aspartic acid (Arg-GlyAsp, known as RGD) to promote cell adhesion [7]. These modified alginate gels have been demonstrated to sustain adhesion, proliferation, and expression of differentiated phenotype of skeletal muscle cells [2]. However, it remains elusive if RGD modification may affect the mechanical properties of alginate. Collagen is the most widely used tissue-derived polymer which constitutes a main component of extracellular matrices of mammalian tissues including tendons and ligaments, bones and cartilage, skin and arteries [8]. However, physically formed collagen gels are lack of mechanical strength. Therefore, it is proposed to chemicall
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