Inhibition of Sodium Citrate on Aggregation and Sedimentation of Nanocalcium Oxalate Dihydrate Crystals

Abstract

Objectives: The effects of sodium citrate (Na3cit) on sedimentation and aggregation of calcium oxalate dihydrate (COD) nanocrystallites with a size of about 50 nm was studied in order to explore the mechanism of Na3cit to inhibit calcium oxalate stone formation. Methods: The influence of concentration of Na3cit (c(Na3cit)) on size, Zeta potential, aggregation, and sedimentation of COD nanoparticles in aqueous solution was studied using nanoparticle size Zeta potential analyzer and ultraviolet spectrophotometer. Results: In lowc(Na3cit) (< 0.8 mmol/L), the inhibition effect of Na3cit on aggregation and sedimentation of nanoCOD increased with the increase ofc(Na3cit); while in highc(Na3cit), COD was gradually dissolved by Na3cit. The former was due to the specific adsorption of citrate ions (cit3-) on COD surface, which made the absolute Zeta-potential increased, therefore inhibited the aggregation and sedimentation of nanocrystallites; the later was because the high concentration of cit3-made Ca2+ions dissociated from the crystal surface, leading to COD dissolution. Conclusions: Na3cit can inhibit the aggregation and sedimentation of nanoCOD in low concentration and dissolve COD in high concentration, indicating that Na3cit can inhibit the formation of calcium oxalate stones.