title: Porphyrin-magnetite nanoconjugates for biological imaging.
abstract: 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.
  
  
  METHODS
  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. β-mercaptoethanol (β-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.
  
  
  CONCLUSIONS
  Our experiments have demonstrated that β-ME visibly enhances the emission intensity. No deleterious effects to the cells were witnessed upon co-incubation with β-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.
authors.affiliation: School of Chemistry, Trinity College Dublin, College Green, Dublin 2, Ireland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Nowostawska
authors.forename: Serena A
authors.initials: SA
authors.lastname: Corr
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Byrne
authors.forename: Jennifer
authors.initials: J
authors.lastname: Conroy
authors.forename: Yuri
authors.initials: Y
authors.lastname: Volkov
authors.forename: Yurii K
authors.initials: YK
authors.lastname: Gun'ko
mesh_terms: D045744:Cell Line, Tumor; D003952:Diagnostic Imaging / Q000379:methods; D006531:HEPES / Q000008:administration & dosage; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D058185:Magnetite Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D008623:Mercaptoethanol / Q000008:administration & dosage; D018613:Microscopy, Confocal / Q000379:methods; D058726:Nanoconjugates / Q000737:chemistry* / Q000648:ultrastructure; D038761:Photobleaching; D011166:Porphyrins / Q000138:chemical synthesis* / Q000378:metabolism; D013194:Staining and Labeling / Q000379:methods
chemical_list: D058185:Magnetite Nanoparticles; D058726:Nanoconjugates; D011166:Porphyrins; D008623:Mercaptoethanol; D006531:HEPES