The combined use of nanoparticles and mesenchymal stem cells (MSC) in regenerative medicine requires the incorporation of the particles and, at the same time, undisturbed cell viability and maintenance of the multi-lineage potential of MSC. The aim of this study was to investigate the uptake of novel phosphonate-functionalised polystyrene nanoparticles prepared by miniemulsion polymerisation. After exposition of human MSC to the particles, their uptake and localisation were analysed by flow cytometry, confocal laser scanning microscopy (CLSM), and transmission electron microscopy (TEM). The osteogenic, adipogenic and chondrogenic differentiation potential was examined by analysing representative marker genes by RT-PCR. Flow cytometry revealed that after 5 and 16 days more than 98% of the MSC and of the cells, which underwent osteogenic and adipogenic differentiation were positive for particle association. CLSM and TEM demonstrated the successful intracellular incorporation of the particles without using any transfection agents and their presence over the cultivation period. The cell viability was found to be unaffected. Particle treated MSC maintained their potential for osteogenic, adipogenic and chondrogenic differentiation. It was concluded that the surface functionalisation with phosphonate groups provides a promising basis for the development of nanoparticles with high intracellular uptake rates for drug delivery or cell labelling.
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