Coatings are provided in which biopolymers may be covalently linked to a substrate. Such biopolymers include those that impart thromboresistance and/or biocompatibility to the substrate, which may be a medical device. Coatings disclosed herein include those that permit coating of a medical device in a single layer, including coatings that permit applying the single layer without a primer. Suitable biopolymers include heparin complexes, and linkage may be provided by a silane having isocyanate functionality.