Rapid Cell Magnetisation Using Cationised Magnetoferritin Introduction Materials and Methods Characterising Magnetoferritin and Cationised Magnetoferritin Stem Cell Labelling with Cationised Magnetoferritin Toxicological Profiling of Cationised Magnetoferritin Escherichia coli labelling with Cationised Magnetoferritin Overall Conclusions and Future Opportunities. Bringing together nanoscience with stem cell and bacterial cell biology this thesis is truly interdisciplinary in scope. It shows that the creation of superparamagnetic nanoparticles inside a protein coat followed by chemical functionalisation of the protein surface provides a novel methodology for cell magnetisation using incubation times as short as one minute. Crucially stem cell proliferation and multi lineage differentiation capacity is not impaired after labelling. Due to the unspecific labelling mechanism this thesis also shows that the same magnetic protein nanoparticles can be used for rapid bacterial magnetisation. Thus it is possible to magnetically capture and concentrate pathogens from clinical samples quickly and highly efficiently.