Abstract: The surface of nanoparticles is of fundamental importance as it interacts with biointerface and decide the fate of nanoparticles inside cell. Surface modification includes ligand exchange, ligand modification and surface capping. The choice of modification approach is, therefore, imperative for the future of nanotechnological platforms. Such platforms not only provide vital biocompatibility but also provide active sites for further functionalization with target molecules, for example in case of surface capping. Furthermore, active sites on modified surface provide further opportunity to link reporter or target molecules to the  surface. Here we give two examples of such systems, as analyte/environment sensors and drug delivery systems.