title: Surface characterization of aspirin crystal planes by dynamic chemical force microscopy.
abstract: Tapping mode (TM) atomic force microscopy (AFM) has been applied in a novel fashion to characterize and distinguish the (001) and (100) surfaces of individual aspirin crystals. The surface characterization was achieved by amplitude-phase, distance (a-p,d) measurements employing gold-coated AFM probes functionalized with self-assembled monolayers (SAM). Experiments using model probes coated with -CH3 and -COOH terminated SAMs have been performed on the two aspirin crystal planes (001) and (100). Results indicate that the hydrophobic -CH3 terminated AFM probes had a greater degree of interaction with the crystal plane (001), whereas the -COOH terminated AFM probes had a larger interaction with the crystal plane (100). Interpretation of these data, based upon the chemistries of the probes, correlates with current understanding of the crystal surface chemistry derived from X-ray diffraction data and dissolution rate studies.
authors.affiliation: Laboratory of Biophysics and Surface Analysis, School of Pharmaceutical Sciences, University of Nottingham, UK.
authors.forename: A
authors.initials: A
authors.lastname: Danesh
authors.forename: M C
authors.initials: MC
authors.lastname: Davies
authors.forename: S J
authors.initials: SJ
authors.lastname: Hinder
authors.forename: C J
authors.initials: CJ
authors.lastname: Roberts
authors.forename: S J
authors.initials: SJ
authors.lastname: Tendler
authors.forename: P M
authors.initials: PM
authors.lastname: Williams
authors.forename: M J
authors.initials: MJ
authors.lastname: Wilkins
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D001241:Aspirin / Q000737:chemistry*; D003460:Crystallization; D018625:Microscopy, Atomic Force / Q000379:methods; D015394:Molecular Structure
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D001241:Aspirin