title: Analysis of a nanocrystalline polymer dispersion of ebselen using solid-state NMR, Raman microscopy, and powder X-ray diffraction.
abstract: OBJECTIVE
  Nanocrystalline drug-polymer dispersions are of significant interest in pharmaceutical delivery. The purpose of this work is to demonstrate the applicability of methods based on two-dimensional (2D) and multinuclear solid-state NMR (SSNMR) to a novel nanocrystalline pharmaceutical dispersion of ebselen with polyvinylpyrrolidone-vinyl acetate (PVP-VA), after initial characterization with other techniques.
  
  
  METHODS
  A nanocrystalline dispersion of ebselen with PVP-VA was prepared and characterized by powder X-ray diffraction (PXRD), confocal Raman microscopy and mapping, and differential scanning calorimetry (DSC), and then subjected to detailed 1D and 2D SSNMR analysis involving ¹H, ¹³C, and ⁷⁷Se isotopes and ¹H spin diffusion.
  
  
  RESULTS
  PXRD was used to show that dispersion contains nanocrystalline ebselen in the 35-60 nm size range. Confocal Raman microscopy and spectral mapping were able to detect regions where short-range interactions may occur between ebselen and PVP-VA. Spin diffusion effects were analyzed using 2D SSNMR experiments and are able to directly detect interactions between ebselen and the surrounding PVP-VA.
  
  
  CONCLUSIONS
  The methods used here, particularly the 2D SSNMR methods based on spin diffusion, provided detailed structural information about a nanocrystalline polymer dispersion of ebselen, and should be useful in other studies of these types of materials.
authors.affiliation: Product Development, GlaxoSmithKline Plc., 709 Swedeland Road, King of Prussia, Pennsylvania 19406, USA. fred.g.vogt@gsk.com
authors.forename: Frederick G
authors.initials: FG
authors.lastname: Vogt
authors.forename: Glenn R
authors.initials: GR
authors.lastname: Williams
mesh_terms: D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D009682:Magnetic Resonance Spectroscopy; D018613:Microscopy, Confocal; D011759:Pyrrolidines / Q000737:chemistry*; D014753:Vinyl Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D011759:Pyrrolidines; D014753:Vinyl Compounds; C402301:poly(vinylpyrrolidone-co-vinyl-acetate)