title: Superparamagnetic magnetite nanocrystal clusters: a sensitive tool for MR cellular imaging.
abstract: Silica coated, PEI and citric acid hybrid superparamagnetic magnetite nanocrystal clusters (SMNC) were synthesized using either a mini-emulsion/sol-gel method or a polyol technique. After careful characterization of the size, structure, composition, and magnetic properties, the as-synthesized SMNC were used for cell labeling while the MR detection sensitivity of cells labeled with silica SMNC was performed with a 3 T whole body MR scanner. TEM investigations revealed that the sizes of the SMNC were about 200 nm and the SMNC mainly consisted of magnetite nanoparticles imbedded in a PEI, citric acid or polystyrene scaffold. Silica and citric acid SMNC were highly negatively charged and PEI SMNC were positively charged. Relaxometry measurements revealed that these SMNC possessed a very high MR sensitivity (silica SMNC: r(2) = 299 s(-1) mM(-1), PEI SMNC: r(2) = 124 s(-1) mM(-1)), especially for the citric acid SMNC (r(2) = 360 s(-1) mM(-1)). Furthermore, when used for cell (RAW264.7 cells) labeling, the SMNC had no adverse effect on cell viability, and the cell uptake of the SMNC show a dose- and time-dependent feature. MR imaging of cells labeled with silica SMNC indicated that cells with a concentration as low as 10 x 10(3) cells ml(-1) could be detected with a 3 T MRI scanner. Our study demonstrated that superparamagnetic magnetite nanocrystal clusters are a sensitive tool for cell imaging.
authors.affiliation: Med-X Research Institute, Shanghai Jiao Tong University, Shanghai 200030, People's Republic of China.
authors.forename: Fenghua
authors.initials: F
authors.lastname: Xu
authors.forename: Changming
authors.initials: C
authors.lastname: Cheng
authors.forename: Fangjie
authors.initials: F
authors.lastname: Xu
authors.forename: Chunfu
authors.initials: C
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Xu
authors.forename: Xuan
authors.initials: X
authors.lastname: Xie
authors.forename: Duanzhi
authors.initials: D
authors.lastname: Yin
authors.forename: Hongchen
authors.initials: H
authors.lastname: Gu
mesh_terms: D000818:Animals; D002460:Cell Line; D019343:Citric Acid / Q000737:chemistry; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D008280:Magnetics; D051379:Mice; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D011094:Polyethyleneimine / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D019343:Citric Acid; D012822:Silicon Dioxide; D011094:Polyethyleneimine