In this work, a novel and facile method for covalent attachment of biomaterials to graphene oxide sheets (GUS) was developed. Four conjugates were obtained via the diimide-activated amidation reaction under ambient conditions. Final products were characterized by FT-IR spectroscopy, atomic force microscopy and transmission electron microscopy. Electrochemical characterization of the composite showed that the covalently bonded biomaterial retained its bioactivity. This method may provide a way for further preparation of graphene-based biodevices. (C) 2011 Elsevier Inc. All rights reserved.