Scanning electron microscopic (SEM) images of as-formed films containing (a) graphene, (b) graphene–haemin, (c) graphene–GOx and (d) graphene–haemin–GOx; and the respective films after immersing into platelet-rich rabbit blood plasma for 3 days: (e) graphene, (f) graphene–haemin, (g) graphene–GOx and (h) graphene–haemin–GOx. Only films containing graphene–haemin–GOx exhibit a minimum morphology change by SEM after immersion into blood plasma compared to control films of graphene, graphene–haemin or graphene–GOx. Scale bars, 10 μm.