Changes in urinary nanocrystallites in calcium oxalate stone formers before and after potassium citrate intake

Chao-Yang Duan,¹ Zhi-Yue Xia,² Guang-Na Zhang,² Bao-Song Gui,¹ Jun-Fa Xue,² Jian-Ming Ouyang<sup>2

1</sup>Department of Nephrology, the Second Hospital of Xi'an Jiaotong University, Xi'an, People's Republic of China; ²Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou, People's Republic of China

Abstract: The property changes of urinary nanocrystallites in 13 patients with calcium oxalate (CaOx) stones were studied before and after ingestion of potassium citrate (K₃cit), a therapeutic drug for stones. The analytical techniques included nanoparticle size analysis, transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The studied properties included the components, morphologies, zeta potentials, particle size distributions, light intensity autocorrelation curves, and polydispersity indices (PDIs) of the nanocrystallites. The main components of the urinary nanocrystallites before K₃cit intake included uric acid, β-calcium phosphate, and calcium oxalate monohydrate. After K₃cit intake, the quantities, species, and percentages of aggregated crystals decreased, whereas the percentages of monosodium urate and calcium oxalate dehydrate increased, and some crystallites became blunt. Moreover, the urinary pH increased from 5.96 ± 0.43 to 6.46 ± 0.50, the crystallite size decreased from 524 ± 320 nm to 354 ± 173 nm, and the zeta potential decreased from −4.85 ± 2.87 mV to −8.77 ± 3.03 mV. The autocorrelation curves became smooth, the decay time decreased from 11.4 ± 3.2 ms to 4.3 ± 1.7 ms, and the PDI decreased from 0.67 ± 0.14 to 0.53 ± 0.19. These changes helped inhibit CaOx calculus formation.

Keywords: nanotechnology, zeta potential, aggregation