High resolution magic angle spinning (H-1 HR-MAS) NMR spectroscopy has been used to analyze the composition of a set of bioactive hydrogels. Therefore, a set of six hydrogels with different cross linker densities ranging from 1 to 12 mol% were prepared by free radical polymerization. The disulfide based cross linkers of the hydrogels were reduced with dithiothreitol (DTT) to generate free sulfhydryl groups giving access to soluble copolymers. Comparison of the H-1 NMR results of the soluble copolymers with those obtained from 1H HR-MAS experiments revealed that for lower cross linker densities of 1-2 mol%, HR-MAS spectroscopy of the hydrogels matches quantitatively the peptide content of the soluble copolymer. With increasing cross linker densities up to 12 mol% the signal intensity of the aromatic unit is linearly reduced to 62% compared to the results obtained by 1H NMR spectroscopy. (C) 2014 Elsevier Ltd. All rights reserved.