title: Label-free imaging of gelatin-containing hydrogel scaffolds.
abstract: Composite hyaluronic acid (HA) hydrogels containing gelatin are used in regenerative medicine as tissue-mimicking scaffolds for improving stem cell survival. Once implanted, it is assumed that these biomaterials disintegrate over time, but at present there is no non-invasive imaging technique available with which such degradation can be directly monitored in vivo. We show here the potential of chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) as a label-free non-invasive imaging technique to monitor dynamic changes in scaffold composition in vivo. The CEST properties of the three individual hydrogel components (HA, GelinS, and polyethylene glycol diacrylate) were first measured in vitro. The complete hydrogel was then injected into the brain of immunodeficient rag2(-/-) mice and CEST MR images were obtained at day 1 and 7 post-transplantation. In vitro, GelinS gave the strongest CEST signal at 3.6 ppm offset from the water peak, originating from the amide protons present in gelatin. In vivo, a significant decrease in CEST signal was observed at 1 week post-implantation. These results were consistent with the biodegradation of the GelinS component, as validated by fluorescent microscopy of implanted hydrogels containing Alexa Fluor 488-labeled GelinS. Our label-free imaging approach should be useful for further development of hydrogel formulations with improved composition and stability.
authors.affiliation: Russell H. Morgan Dept. of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Yajie
authors.initials: Y
authors.lastname: Liang
authors.affiliation: Russell H. Morgan Dept. of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Amnon
authors.initials: A
authors.lastname: Bar-Shir
authors.affiliation: Russell H. Morgan Dept. of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Song
authors.affiliation: Russell H. Morgan Dept. of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Assaf A
authors.initials: AA
authors.lastname: Gilad
authors.affiliation: Russell H. Morgan Dept. of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Piotr
authors.initials: P
authors.lastname: Walczak
authors.affiliation: Russell H. Morgan Dept. of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Dept. of Chemical & Biomolecular Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Dept. of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Dept. of Oncology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Electronic address: jwmbulte@mri.jhu.edu.
authors.forename: Jeff W M
authors.initials: JW
authors.lastname: Bulte
mesh_terms: D000818:Animals; D005780:Gelatin / Q000494:pharmacology*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry / Q000494:pharmacology*; D021621:Imaging, Three-Dimensional; D020007:Implants, Experimental; D008279:Magnetic Resonance Imaging; D008297:Male; D051379:Mice; D013194:Staining and Labeling; D054457:Tissue Scaffolds / Q000737:chemistry*
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D005780:Gelatin
keywords: CEST MRI; Gelatin; Hyaluronic acid; Hydrogel; Scaffold; Transplantation