Porphyrin-magnetite nanoconjugates for biological imaging.

BACKGROUND: The use of silica coated magnetic nanoparticles as contrast agents has resulted in the production of highly stable, non-toxic 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 "two-in-one" magnetic fluorescent nanocomposites composed of silica-coated magnetite nanoparticles covalently linked to a porphyrin moiety. METHOD: The experiments were performed by administering porphyrin functionalised silica-coated magnetite nanoparticles to THP-1 cells, a human acute monocytic leukaemia cell line. Cells were cultured in RPMI 1640 medium with 25 mM HEPES supplemented with heat-inactivated foetal bovine serum (FBS). RESULTS: We have synthesised, characterised and analysed in vitro, a new multimodal (magnetic and fluorescent) porphyrin magnetic nanoparticle composite (PMNC). Initial co-incubation experiments performed with THP-1 macrophage cells were promising; however the PMNC photobleached under confocal microscopy study. ß-mercaptoethanol (ß-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 environment. CONCLUSION: Our experiments have demonstrated that ß-ME visibly enhances the emission intensity. No deleterious effects to the cells were witnessed upon co-incubation with ß-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.

Linear assemblies of magnetic nanoparticles as MRI contrast agents.

Using a one-step procedure we have prepared magnetic fluids comprising of polyelectrolyte stabilized magnetite nanoparticles. These nanocomposites are comprised of linear, chain-like assemblies of magnetic nanoparticles, which can be aligned in parallel arrays by an external magnetic field. We have shown the potential use of these materials as contrast agents by measuring their MR response in live rats. The new magnetic fluids have demonstrated good biocompatibility and potential for in vivo MRI diagnostics.

High-content screening as a universal tool for fingerprinting of cytotoxicity of nanoparticles.

Recent advances and progress in nanobiotechnology have demonstrated many nanoparticles (NPs) as potential and novel drug delivery vehicles, therapeutic agents, and contrast agents and luminescent biological labels for bioimaging. The emergence of new biomedical applications based on NPs signifies the need to understand, compare, and manage their cytotoxicity. In this study, we demonstrated the use of high-content screening assay (HCA) as a universal tool to probe the cytotoxicity of NPs and specifically cadmium telluride quantum dots (CdTe QDs) and gold NPs (Au NPs) in NG108-15 murine neuroblastoma cells and HepG2 human hepatocellular carcinoma cells. Neural cells represent special interest for NP-induced cytotoxicity because the optical and electrical functionalities of materials necessary for neural imaging and interfacing are matched well with the properties of many NPs. In addition, the cellular morphology of neurons is particularly suitable for automated high content screening. HepG2 cells represent a good model for high content screening studies since they are commonly used as a surrogate for human hepatocytes in pharmaceutical studies. We found the CdTe QDs to induce primarily apoptotic response in a time- and dosage-dependent manner and produce different toxicological profiles and responses in undifferentiated and differentiated neural cells. Au NPs were found to inhibit the proliferation and intracellular calcium release of HepG2 cells.