title: MRI-monitored intra-tumoral injection of iron-oxide labeled Clostridium novyi-NT anaerobes in pancreatic carcinoma mouse model.
abstract: OBJECTIVE
  To validate the feasibility of labeling Clostridium novyi-NT (C.novyi-NT) anaerobes with iron-oxide nanoparticles for magnetic resonance imaging (MRI) and demonstrate the potential to use MRI to visualize intra-tumoral delivery of these iron-oxide labeled C.novyi-NT during percutaneous injection procedures.
  
  
  METHODS
  All studies were approved by IACUC. C.novyi-NT were labeled with hybrid iron-oxide Texas red nanoparticles. Growth of labeled and control samples were evaluated with optical density. Labeling was confirmed with confocal fluorescence and transmission electron microscopy (TEM). MRI were performed using a 7 Tesla scanner with T2*-weighted (T2*W) sequence. Contrast-to-noise ratio (CNR) measurements were performed for phantoms and signal-to-noise ratio (SNR) measurements performed in C57BL/6 mice (n = 12) with Panc02 xenografts before and after percutaneous injection of iron-oxide labeled C.novyi-NT. MRI was repeated 3 and 7 days post-injection. Hematoxylin-eosin (HE), Prussian blue and Gram staining of tumor specimens were performed for confirmation of intra-tumoral delivery.
  
  
  RESULTS
  Iron-oxide labeling had no influence upon C.novyi-NT growth. The signal intensity (SI) within T2*W images was significantly decreased for iron-oxide labeled C.novyi-NT phantoms compared to unlabeled controls. Under confocal fluorescence microscopy, the iron-oxide labeled C.novyi-NT exhibited a uniform red fluorescence consistent with observed regions of DAPI staining and overall labeling efficiency was 100% (all DAPI stained C.novyi-NT exhibited red fluorescence). Within TEM images, a large number iron granules were observed within the iron-oxide labeled C.novyi-NT; these were not observed within unlabeled controls. Intra-procedural MRI measurements permitted in vivo visualization of the intra-tumoral distribution of iron-oxide labeled C.novyi-NT following percutaneous injection (depicted as punctate regions of SI reductions within T2*-weighted images); tumor SNR decreased significantly following intra-tumoral injection of C.novyi-NT (p<0.05); these SNR reductions were maintained at 3 and 7 day follow-up intervals. Prussian blue and Gram staining confirmed presence of the iron-oxide labeled anaerobes.
  
  
  CONCLUSIONS
  C.novyi-NT can be labeled with iron-oxide nanoparticles for MRI visualization of intra-tumoral deposition following percutaneous injection during bacteriolytic therapy.
authors.affiliation: Department of Radiology, First People's Hospital, Shanghai Jiaotong University, Shanghai, China; Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America.
authors.forename: Linfeng
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America; Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois, United States of America.
authors.forename: Zhuoli
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Immunology, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Khashayarsha
authors.initials: K
authors.lastname: Khazaie
authors.affiliation: BioMed Valley Discoveries, Kansas City, Missouri, United States of America.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Saha
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lewandowski
authors.affiliation: Department of Radiology, First People's Hospital, Shanghai Jiaotong University, Shanghai, China.
authors.forename: Guixiang
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America; Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois, United States of America.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Larson
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003013:Clostridium / Q000737:chemistry* / Q000254:growth & development; D005260:Female; D005290:Ferric Compounds / Q000737:chemistry*; D006801:Humans; D007279:Injections, Subcutaneous; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles / Q000008:administration & dosage* / Q000737:chemistry; D051379:Mice; D010190:Pancreatic Neoplasms / Q000628:therapy* / Q000648:ultrastructure*; D059629:Signal-To-Noise Ratio; D023041:Xenograft Model Antitumor Assays
chemical_list: D005290:Ferric Compounds; D058185:Magnetite Nanoparticles; C000499:ferric oxide