Aggregation and dispersion characteristics of calcium oxalate monohydrate: Effect of urinary species

Kimberly G. Christmas, Laurie B. Gower, Saeed R. Khan, Hassan El-Shall

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


In this research, screening and central composite experimental designs are used to determine the effect of various factors on the aggregation and dispersion characteristics of previously grown calcium oxalate monohydrate (COM) crystals in artificial urinary environments of controlled variables. The variables examined are pH and calcium, oxalate, pyrophosphate, citrate, and protein concentrations in ultrapure water and artificial urine. Optical density measurements, particle size analysis, optical microscopy, AFM force measurements, and protein adsorption have been used to assess the state of aggregation and dispersion of the COM crystals and to elucidate the mechanisms involved in such a complex system. The data indicate that our model protein, mucin, acts as a dispersant. This is attributed to steric hindrance resulting from the adsorbed mucoprotein. Oxalate, however, promotes aggregation. Interesting interactions between protein and oxalate along with protein and citrate are observed. Such interactions (synergistic or antagonistic) are found to depend on the concentrations of these species. Surface responses for these interactions are presented and discussed in this paper. In summary, solution, surface, and interface chemistries interact in a complex manner in the physiological environment to either inhibit or promote aggregation, and an understanding of such interactions may help determine and control the factors affecting kidney stone formation.

Original languageEnglish (US)
Pages (from-to)168-174
Number of pages7
JournalJournal of Colloid and Interface Science
Issue number1
StatePublished - 2002
Externally publishedYes


  • AFM force measurements
  • Artificial urine
  • Calcium oxalate
  • Citrate
  • Crystal aggregation and dispersion
  • Experimental design
  • Kidney stones
  • Oxalate
  • Protein adsorption

ASJC Scopus subject areas

  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry
  • Surfaces and Interfaces


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