The development of multifunctional, biocompatible nanoparticles is essential for delivering drugs and biomolecules into the cell. Here, we have functionalised TiO2 nanoparticles with tris-(nitrilo trisacetic acid) (Tris-NTA) and biotin, by covalent surface functionalisation. This biocompatible nanoparticle is non-cytotoxic and can deliver both oligo-histidine and avidin conjugated biomolecules simultaneously into the cell. © 2013 The Royal Society of Chemistry.