Phase, Morphology, and Water Uptake Measurements of Mixed Salt Nano-Nuclei Found in Kidney Stones

DEWANSH RASTOGI, Kanishk Gohil, Kotiba A. Malek, Chao Peng, Mingjin Tang, Akua Asa-Awuku, University of Maryland College Park

     Abstract Number: 191
     Working Group: Aerosol Physical Chemistry and Microphysics

Abstract
Kidney stone formation is attributed to the deposition of various salts or minerals inside the renal gland. Current treatments rely on invasive techniques that involve chemo dissolution or surgery. The solute-solvent interaction plays a significant role in kidney stone formation. Hence, investigating this property on a nanoscale can help with prevention and improved treatment methods.

In this work, the water uptake of aerosolized uric acid, calcium oxalate, calcium phosphate, and ammonium magnesium phosphate, and a mixture of these salts is investigated under sub- and supersaturated conditions using H-TDMA and CCNC measurements. In addition, the water uptake was also investigated for bulk salts using a Thermogravimetric Analyzer (TGA). Our water uptake measurements show that uric acid particles have a very low hygroscopicity value (less than 0.01) than inorganic salts such as sodium chloride. Due to the low solubility of salts, an adsorption model was used to obtain an accurate water uptake profile for each of the salt and mixtures. The hygroscopicity values differed at subsaturated and supersaturated conditions for droplet dried particles. Bulk salt particles were found to have a lower affinity for water than submicron particles. This indicates the salt particles crystallize from surrounding media even at low concentrations in the solution phase. Once formed, these crystals tend to be difficult to dissolve.

Furthermore, the morphology of particles at submicron sizes is significantly different from super micron size crystalline particles. Visualization tools such as electron microscopy reveal that mixed salt nuclei can result in homogeneous and phase-separated particles. This suggests heterogeneous nucleation can occur at the initial stages of nucleation and eventually stone formation. The phase of mixed salt nanoparticles also affects the water uptake properties of particles.