a biocompatible biological component is provided comprising a membrane - mimetic surface film covering a substrate . suitable substrates include hydrated substrates , e . g . hydrogels which may contain drugs for delivery to a patient through the membrane - mimetic film , or may be made up of cells , such as islet cells , for transplantation . the surface may present exposed bioactive molecules or moieties for binding to target molecules in vivo , for modulating host response when implanted into a patient and the surface may have pores of selected sizes to facilitate transport of substances therethrough . an optional hydrophilic cushion or spacer between the substrate and the membrane - mimetic surface allows transmembrane proteins to extend from the surface through the hydrophilic cushion , mimicking the structure of naturally - occurring cells . an alkylated layer directly beneath the membrane - mimetic surface facilates bonding of the surface to the remainder of the biological component . alkyl chains may extend entirely through the hydrophilic cushion when present . to facilitate binding , the substrate may optionally be treated with a polyelectrolyte or alternating layers of oppositely - charged polyelectrolytes to facilitate charged binding of the membrane - mimetic film or alkylated layer beneath the membrane - mimetic film to the substrate . the membrane - mimetic film is preferably made by in situ polymerization of phospholipid vesicles .