Networks of nanoscale fibrous coatings made from self-assembled peptides are promising candidates for biomaterials that can promote the growth of mammalian cells. One particularly attractive feature is the possibility of adding biofunctional sequences to peptides to promote cell attachment. We deconvolute the topographic and chemical effects of nanoscale fibrils on cells by depositing a plasma polymer film on TTR1-based fibrils decorated with a range of cell adhesive chemistries (RGD and cycloRGDfK), producing a surface that retains the nanoscale fibrous topography of surface-bound fibrils but lacks the fibril surface chemistry. The surface topography was found to influence cell toxicity and spreading, and the fibril surface chemistry influenced cell attachment and spreading. This study highlights the importance of considering both the chemical and physical features of novel biomaterials and illustrates the use of plasma polymer deposition as a tool for examining the relationship between amyloid fibril structure and function.