Category: Basic Science: Stones

MP2-3 - Exploring Thermodynamics of Kidney Stone Compounds to Optimize Calcium Oxalate Kidney Stone Dissolution and Crystallization

Thu, Sep 20
4:00 PM - 6:00 PM

Introduction & Objective : Prevalence of kidney stones is increasing throughout the world. Laser lithotripsy via ureteroscopy is performed to break up the stones into 0.5 mm, which may remain behind. This “dust” may become a nidus for crystal deposition and lead to recurrence of kidney stones. Our aim is to explore thermodynamic theories to aid in determination of ideal conditions for crystallization and dissolution of calcium oxalate kidney stone fragments.  

Methods : Based on the study by Thongboonkerd et. l, dissolution agent and chelator will be the solution of interest. We use the Gibbs equation (ΔG = ΔH - TΔS) to calculate and predict ideal conditions for stone dissolution.  Calcium oxalate crystals were formed by combining salts containing both calcium and oxalate in accordance with the chemical equation: Ca2+ + C2O42- → CaC2O4.  Dissolution agent sodium citrate and EDTA chelator are optimal compounds for calcium oxalate dissolution. For creation of a stone crystal model, OPN at physiologic pH, protein matrix (lab made Human Placental Matrix-HPM), and calcium oxalate were combined in artificial urine.   

Results : The measured dissolution enthalpies of the various calcium oxalate hydrates were determined via calorimetric experiments observed.  In water, calcium oxalate monohydrate requires 21.1 kJ/mol for dissolution, and the formation of sodium oxalate produces approximately 16.6 kJ, both at 25 C.  Calcium-EDTA produces 50 kJ of energy in TRIS buffer at pH 7.5 which provides the required energy for breaking calcium oxalate and hydrogen bonds.  The isoelectric point of OPN is 4.7, thus at pH close to 6.5, free calcium ions will primarily bind OPN which will result in less COM crystallization observed under microscopy. Crystals were observed under fluorescent and light microscopy.  HPM grown crystals promoted crystal growth over its matrix.  With no OPN present, there is more crystal growth compared to the crystals grown in the presence of OPN which may indicate crystallization suppression activity by OPN.  

Conclusions : Theoretically, ideal dissolution agent was found to be sodium citrate with EDTA on TRIS at physiologic pH, due to its favorable thermodynamic interactions. Osteopontin, will either enhance or inhibit stone formation depending on the pH related to its isoelectric point. Crystallization occurred more readily at low pH for the agents used.

Noa Grooms

Biomedical Engineering Candidate 2018
University of Florida
Navarre, Florida

Nicole Bird

Biomedical Engineering Candidate 2018
U. of Florida
Gainesville, Florida

Steven Arce

Faculty, Biomedical Engineering
U. of Florida, College of Engineering
Gainesville, Florida

Victoria Bird

Assistant Professor of Urology, Affiliate Professor of Biomedical Engineering, Director
U. of Florida, College of Medicine and College of Engineering, National Medical Association and Research Group LLC
Gainesville, Florida

National Medical Association and Research Group, Director.

Latina Women's League, Director of Health Projects.

Nicole ANNE. Bohmann

University of Florida
Gainesville, Florida

Michele Dill

Biomedical Engineering candidate 2019
Biomedical Engineering, College of Engineering
Ocoee, Florida