Phosphorylation of alginate was achieved using a heterogeneous urea/phosphate reaction. The degree. and stereoselectivity of phosphorylation a. well as the effects on. the physical properties of the polysaccharide were investigated. by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies, inductively coupled plasma optical :emission spectroscopy (ICP-OES), and size exclusion (SEC). Multidimensional NMR. studies of the phosporylated alginate revealed that phosphorylation of the M residues occurred predominantly at the C3 (equatorial) carbon. of the polysaccharide ring. In addition, a More comprehensive assignment of the H-1 NMR spectrum of alginate, compared with those previously reported in the literature, is provided here. Hydrogel material's were formed from ionically cross-linked blend's of phosphorylated alginate and alginate. These blended hydrogels showed an enhanced resistance to degradation by chelating agents Compared with cross linked alginate hydrogels and a reduction in their mineralization potential.