Peptides on surfaces have many applications in biosensing and biomaterials, both in influencing the affinity for biomolecule and cells for a surface and in providing that surface with the ability to determine the activity of protease enzymes in a biological medium. In this presentation we will discuss some of our work on using peptides on surfaces for biosensing and cell biology applications. We will initially start with an electrochemical biosensors for glycosylated haemoglobin, referred to as HbA1c and an important biomarker of the glucose levels in the blood over the preceding 3 months. This biosensor employs a surface-bound glycosylated pentapeptide to ensure specific binding of anti-HbA1c antibodies to the surface. The presentation will next cover using peptide modified photonic crystals as a means to monitor the release of matrix metalloprotease enzymes, MMP2 and MMP9, from live macrophage cells. In this work surface chemical techniques to allow different peptides to be immobilised on the exterior and interior walls of mesoporous silicon photonic crystals is outlined. In later work we demonstrate the ability to give these photonic crystals specificity for a given protease enzyme using a custom synthesized polymer cross-linked with appropriate peptide sequences. Finally the talk will cover work on modifying flat surfaces with different densities of RGD peptides on a surface and showing how the surface density of peptides influences cell phenotype and behaviour. The influence of the peptide density on cell behaviour is ascertained using electrochemical impedance, cell migration studies and western blots for monitoring signalling proteins.