title: An in situ atomic force microscopy study of uric acid crystal growth.
abstract: Kidney stones are heterogeneous polycrystalline aggregates that can consist of several different building blocks. A significant number of human stones contain uric acid crystals as a crystalline component, though the molecular-level growth of this important biomaterial has not been previously well-characterized. In the present study, in situ atomic force microscopy (AFM) is used to investigate the real-time growth on the (100) surface of uric acid (UA) single crystals as a function of fundamental solution parameters. Layer-by-layer growth on UA (100) was found to be initiated at screw dislocation sites and to proceed via highly anisotropic rates which depend on the crystallographic direction. The smallest b-steps exhibited minimum heights corresponding to two molecular layers, while fast-moving c-steps more commonly showed monolayer heights. Growth kinetics measured under a range of flow rates, supersaturation levels, and pH values reveal linear trends in the growth kinetics, with faster growth attained in solutions with higher supersaturation and/or pH. The calculated kinetic parameters for UA growth derived from these experiments are in good agreement with the values reported for other crystal systems.
authors.affiliation: Department of Chemistry, Georgetown University, 37th and "O" Streets NW, Washington, D.C. 20057-1227, USA.
authors.forename: Ryan E
authors.initials: RE
authors.lastname: Sours
authors.forename: Amanuel Z
authors.initials: AZ
authors.lastname: Zellelow
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Swift
mesh_terms: D003460:Crystallization; D007700:Kinetics; D018625:Microscopy, Atomic Force / Q000379:methods*; D014527:Uric Acid / Q000737:chemistry*
chemical_list: D014527:Uric Acid