in the present specification and claims , three modified cell culture substrates are disclosed for protecting peptide mimetic surfaces used in cell culture technology . the methods are able to retain the functionality of the bioactive species conjugated to the surface . in particular , a vitronectin peptide fragment ac - lys - gly - gly - pro - gln - val - thr - arg - gly - asp - val - phe - thr - met - pro - nh2 was able to facilitate growth and proliferation of undifferentiated human embryonic stem cells after stabilization using 3 different modified cell culture substrates for of protection against gamma irradiation . the modified substrates disclosed in this invention are covalent attachment of the antioxidant molecules ; the use of coatings consisting of anti - oxidants and stabilizers comprising glycoprotiens , sugars , carbohydrates , poly , peptides and hydrophilic polymers ; and a third method wherein the same methionine contained in the bioactive sequence used to facilitate growth and proliferation of human embryonic stem cells was also used as a sacrificial coating to protect the same conjugated sequence against damage by gamma irradiation .