title: Formulation of novel lipid-coated magnetic nanoparticles as the probe for in vivo imaging.
abstract: BACKGROUND
  Application of superparamagnetic iron oxide nanoparticles (SPIOs) as the contrast agent has improved the quality of magnetic resonance (MR) imaging. Low efficiency of loading the commercially available iron oxide nanoparticles into cells and the cytotoxicity of previously formulated complexes limit their usage as the image probe. Here, we formulated new cationic lipid nanoparticles containing SPIOs feasible for in vivo imaging.
  
  
  METHODS
  Hydrophobic SPIOs were incorporated into cationic lipid 1,2-dioleoyl-3-(trimethylammonium) propane (DOTAP) and polyethylene-glycol-2000-1,2-distearyl-3-sn-phosphatidylethanolamine (PEG-DSPE) based micelles by self-assembly procedure to form lipid-coated SPIOs (L-SPIOs). Trace amount of Rhodamine-dioleoyl-phosphatidylethanolamine (Rhodamine-DOPE) was added as a fluorescent indicator. Particle size and zeta potential of L-SPIOs were determined by Dynamic Light Scattering (DLS) and Laser Doppler Velocimetry (LDV), respectively. HeLa, PC-3 and Neuro-2a cells were tested for loading efficiency and cytotoxicity of L-SPIOs using fluorescent microscopy, Prussian blue staining and flow cytometry. L-SPIO-loaded CT-26 cells were tested for in vivo MR imaging.
  
  
  RESULTS
  The novel formulation generates L-SPIOs particle with the average size of 46 nm. We showed efficient cellular uptake of these L-SPIOs with cationic surface charge into HeLa, PC-3 and Neuro-2a cells. The L-SPIO-loaded cells exhibited similar growth potential as compared to unloaded cells, and could be sorted by a magnet stand over ten-day duration. Furthermore, when SPIO-loaded CT-26 tumor cells were injected into Balb/c mice, the growth status of these tumor cells could be monitored using optical and MR images.
  
  
  CONCLUSIONS
  We have developed a novel cationic lipid-based nanoparticle of SPIOs with high loading efficiency, low cytotoxicity and long-term imaging signals. The results suggested these newly formulated non-toxic lipid-coated magnetic nanoparticles as a versatile image probe for cell tracking.
authors.affiliation: Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan. hchuang@ntu.edu.tw
authors.forename: Huey-Chung
authors.initials: HC
authors.lastname: Huang
authors.forename: Po-Yuan
authors.initials: PY
authors.lastname: Chang
authors.forename: Karen
authors.initials: K
authors.lastname: Chang
authors.forename: Chao-Yu
authors.initials: CY
authors.lastname: Chen
authors.forename: Chung-Wu
authors.initials: CW
authors.lastname: Lin
authors.forename: Jyh-Horng
authors.initials: JH
authors.lastname: Chen
authors.forename: Chung-Yuan
authors.initials: CY
authors.lastname: Mou
authors.forename: Zee-Fen
authors.initials: ZF
authors.lastname: Chang
authors.forename: Fu-Hsiung
authors.initials: FH
authors.lastname: Chang
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology; D000818:Animals; D002412:Cations; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects / Q000637:transplantation; D015179:Colorectal Neoplasms / Q000473:pathology; D003287:Contrast Media / Q000138:chemical synthesis; D005229:Fatty Acids, Monounsaturated; D005240:Feasibility Studies; D005290:Ferric Compounds / Q000633:toxicity; D006367:HeLa Cells / Q000187:drug effects; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008279:Magnetic Resonance Imaging; D008297:Male; D053768:Metal Nanoparticles / Q000633:toxicity; D051379:Mice; D008807:Mice, Inbred BALB C; D008823:Micelles; D009447:Neuroblastoma / Q000473:pathology; D010316:Particle Size; D010714:Phosphatidylethanolamines; D011092:Polyethylene Glycols; D011471:Prostatic Neoplasms / Q000473:pathology; D000644:Quaternary Ammonium Compounds; D012235:Rhodamines
chemical_list: D002412:Cations; D003287:Contrast Media; D005229:Fatty Acids, Monounsaturated; D005290:Ferric Compounds; D008823:Micelles; D010714:Phosphatidylethanolamines; D000644:Quaternary Ammonium Compounds; D012235:Rhodamines; C107570:polyethylene glycol-distearoylphosphatidylethanolamine; C000499:ferric oxide; C094877:dioleoyl phosphatidylethanolamine; D011092:Polyethylene Glycols; C070046:1,2-dioleoyloxy-3-(trimethylammonium)propane