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. 2021 Oct 1;6(40):26566-26574.
doi: 10.1021/acsomega.1c03938. eCollection 2021 Oct 12.

Calcium Oxalate Crystallization: Influence of pH, Energy Input, and Supersaturation Ratio on the Synthesis of Artificial Kidney Stones

Helen Werner  1 , Shalmali Bapat  2 , Michael Schobesberger  1 , Doris Segets  2   3 , Sebastian P Schwaminger  1   4
Affiliations

Calcium Oxalate Crystallization: Influence of pH, Energy Input, and Supersaturation Ratio on the Synthesis of Artificial Kidney Stones

Helen Werner et al. ACS Omega. .

Abstract

The removal of kidney stones can lead to small residual fragments remaining in the human body. Residual stone fragments can act as seeds for kidney stone crystallization and may necessitate another intervention. Therefore, it is important to create a consistent model with a particle size comparable to the range of kidney stone fragments. Thus, the size-determining parameters such as supersaturation ratio, energy input, and pH value are examined. The batch crystallizations were performed with supersaturation ratios between 5.07 and 6.12. The compositions of the dried samples were analyzed with Raman spectroscopy, infrared spectroscopy, and X-ray diffraction (XRD). The samples were identified as calcium oxalate monohydrate with spectroscopic analysis, while calcium oxalate dihydrate being the most prominent crystalline species at all supersaturation ratios for the investigated conditions. The aggregate size, obtained with analytical centrifugation, varied between 2.9 and 4.3 μm, while the crystallite domain size, obtained from XRD, varied from 40 to 61 nm. Our results indicate that particle sizes increase with increasing supersaturation, energy input, and pH. All syntheses yield a high particle heterogeneity and represent an ideal basis for reference materials of small kidney stone fragments. These results will help better understand and control the crystallization of calcium oxalate and the aggregation of such pseudopolymorphs.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(a) Raman spectrum of the powder form of the sample crystallized at a supersaturation ratio of 5.72, measured with a 488 nm laser and a power of 4 mW. (b) FT-IR spectrum of the powder form of the sample crystallized at a supersaturation ratio of 5.72, measured in a range between 400 and 4000 cm–1. The ATR–IR spectra of COD and COM from the RUFF database have been used as a reference.
Figure 2
Figure 2
Diffractogram and Rietveld refinement of the diffractogram of the powder sample crystallized at a supersaturation ratio of 5.72 irradiated with Cu Kα1. Data points correspond to a refinement of COD, and the difference corresponds to COM. The references of COM (whewellite), COD (weddellite), and COT (caoxite) from the RUFF database are shown.
Figure 3
Figure 3
Hydrodynamic diameter measured by AC as a function of the supersaturation ratio.
Figure 4
Figure 4
Exemplary transmittogram of the sample crystallized at a supersaturation ratio of 5.96. A sucrose concentration of 25% was used as the continuous phase for the experiment to slow down sedimentation. The meniscus and sedimentation fronts are marked by black arrows. I and II indicate sedimentation fronts of larger and smaller aggregates, respectively.
Figure 5
Figure 5
Hydrodynamic diameter as a function of the Reynolds number in a range between Re = 732.4 and Re = 1614.
Figure 6
Figure 6
Intensity-weighted cumulative size distribution Q(x) with varying energy input and pH. Numbers 1–6 correspond to the sample code used in Table 3.
See this image and copyright information in PMC

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