Agarose is often used as a support for the tri-dimensional culture of human and animal cells. Because agarose forms a non-cytotoxic hydrogels, it can be utilized to reproduce the natural environment of cells in the human body, the extracellular matrix. However, agarose forms a stiff inert hydrogel that does not carry any biological information, thus the human and animal cells can not adhere to the polysaccharide. Because of these specifics properties, agarose hydrogel mimics the natural environment of cartilage cells and have been shown to support the differentiation of chondrocytes into cartilage. In order to modify the mechanical properties of agarose to reproduce the natural environment of other human cells, agarose can be chemically modified through the precise oxidation of the primary alcohol of the D-galactose into carboxylic acid. This chemical modification provides a novel class of materials named carboxylated agarose. Through the control over the number of carboxylated D-galactose on the polysaccharide backbone, the mechanical properties of the resulting hydrogel can be precisely controlled. These carboxylated agarose hydrogels can be then covalently bond to peptides to form hydrogel on which cells can adhere. These carboxylated agarose hydrogels have been shown to direct the organization of human endothelial cells into polarized lumens.