title: Surface study of collagen/poloxamine hydrogels by a 'deep freezing' ToF-SIMS approach.
abstract: In order to determine the presence of collagen molecules at the surface of a collagen-modified poloxamine hydrogel (a semi-interpenetrating network), the surface composition was studied using Time-of-Flight Secondary Ion Mass Spectra (ToF-SIMS). Collagen was added to the poloxamine hydrogel (poloxamine is a commercially available four-arm poly(ethylene oxide)/poly(propylene oxide) block copolymer, PEO/PPO) to promote the attachment of endothelial or liver cells. X-ray photoelectron spectroscopy (XPS) of dry samples showed a sharp increase in the N content from 0.6% in a pure poloxamine hydrogel to 8.8% in the collagen-containing material. Afterwards, the surface was studied by a 'deep freezing' ToF-SIMS approach under progressive heating from -120 to -60 degrees C. The positive spectrum of collagen/poloxamine at -65 degrees C displayed distinct signals corresponding to different amino acid fragments such as CH4N+ (30 m/z, Gly), C3HN2+ (43 m/z, Arg), C2H6N+ (44 m/z, Ala) and C4H5N2+(81m/z, His) and others corresponding to the PEO and PPO blocks of poloxamine. In addition, the negative spectrum showed peaks at 26 m/z (CN-), 32 m/z (S-) and 42 m/z (CNO-) characteristic of fragments of the collagen molecule. Imaging experiments indicated the homogeneous distribution of the collagen on the surface. These results supported the use of ToF-SIMS for the surface characterization of hydrated hydrogels and confirmed the collagen presence as the means whereby cells attach to the modified poloxamine matrix.
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College St, Toronto, ON, Canada. ale.sosnik@utoronto.ca
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sosnik
authors.forename: Rana N S
authors.initials: RN
authors.lastname: Sodhi
authors.forename: Peter M
authors.initials: PM
authors.lastname: Brodersen
authors.forename: Michael V
authors.initials: MV
authors.lastname: Sefton
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D002417:Cattle; D002448:Cell Adhesion; D002478:Cells, Cultured; D003094:Collagen / Q000737:chemistry*; D005029:Ethylenediamines / Q000737:chemistry*; D005615:Freezing; D020100:Hydrogels / Q000737:chemistry; D066298:In Vitro Techniques; D008422:Materials Testing; D008856:Microscopy, Fluorescence; D015394:Molecular Structure; D018629:Spectrometry, Mass, Secondary Ion / Q000295:instrumentation; D013057:Spectrum Analysis; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry; D014965:X-Rays
chemical_list: D001672:Biocompatible Materials; D005029:Ethylenediamines; D020100:Hydrogels; D013501:Surface-Active Agents; C112299:Tetronic 1107; D003094:Collagen