Inside human tissues, cells interact within a complex 3D microenvironment, while spreading, migrating, proliferating, and differentiating in the extracellular matrix (ECM). The need to mimic complex cellular environment has led to the emergence of hydrogel matrices that mimic the ECM.
Gelatin, which is derived from the hydrolysis of collagen, is a popular hydrogel that has been extensively used to create such realistic 3D in vitro models. Moreover, gelatin contains promotors of cell remodeling such as target sequences of matrix metalloproteinase (MMP) and cell attachment enhancers such as arginine-glycine-aspartic acid (RGD) sequences. However, gelatin has several limiting factors such as its low mechanical modulus, its rapid degradation and its low gelling point, making it difficult to manipulate at physiological temperature.
Chemical modification of gelatin prior to crosslinking can overcome some of these limitations. One such example, is gelatin methacryloyl (GelMA) which requires the addition of methacrylate groups to the amine-containing side groups of gelatin. This methacrylation reaction allows, in the presence of a photoinitiator, the UV-light induced polymerization of GelMA to produce hydrogels that are stable at 37 °C and mechanically stronger than unmodified gelatin hydrogels.
Although GelMA has been widely used as a biomaterial, the influence of the methacrylation reaction parameters on the physical properties of GelMA has only been studied using one-factor-at-a-time experimentation, which does not take into consideration the interaction between set parameters. The aim of the present work was to fully understand the effect and interactions of the most common parameters used to control the methacrylation reaction of GelMA, and consequently control and study the physical properties of its resulting crosslinked hydrogels, using an experimental design approach. The experimental design led to a quadratic empirical model that was used to control the degree of substitution and physical properties of GelMA .