porphyrinmagnetite nanoconjugates for biological imaging background the use of silica coated magnetic nanoparticles as contrast agents has resulted in the production of highly stable nontoxic solutions that can be manipulated via an external magnetic field as a result the interaction of these nanocomposites with cells is of vital importance in understanding their behaviour and biocompatibility here we report the preparation characterisation and potential application of new twoinone magnetic fluorescent nanocomposites composed of silicacoated magnetite nanoparticles covalently linked to a porphyrin moietymethod the experiments were performed by administering porphyrin functionalised silicacoated magnetite nanoparticles to thp1 cells a human acute monocytic leukaemia cell line cells were cultured in rpmi 1640 medium with 25 mm hepes supplemented with heatinactivated foetal bovine serum fbsresults we have synthesised characterised and analysed in vitro a new multimodal magnetic and fluorescent porphyrin magnetic nanoparticle composite pmnc initial coincubation experiments performed with thp1 macrophage cells were promising however the pmnc photobleached under confocal microscopy study mercaptoethanol me was employed to counteract this problem and resulted not only in enhanced fluorescence emission but also allowed for elongated imaging and increased exposure times of the pmnc in a cellular environmentconclusion our experiments have demonstrated that me visibly enhances the emission intensity no deleterious effects to the cells were witnessed upon coincubation with me alone and no increases in background fluorescence were recorded these results should present an interest for further development of in vitro biological imaging techniques