(183al) Real Time Evaluation of Struvite Formation: Insights from the Macroscopic to Molecular Scale

The formation of so-called infection stones arising from urinary tract infections is one of the most difficult and dangerous stone diseases due to its large size, rapid growth, and high recurrence. Infection by urease positive bacteria leads to a cascade of reactions that elevates the pH, as well as concentrations of NH₄⁺ and PO₄^3- ions, resulting in precipitation of struvite (MgNH₄PO₄Ë‘6H₂O). These crystals have clinical implications as approximately 50% of all long-term catheterized patients experience catheter blockage that leads to more serious complications due to reflux to kidneys by urine flowing back¹.

Research efforts have focused on understanding the effects of different parameters (e.g., supersaturation, pH, modifiers) on crystallization of struvite; however, conventional batch experiments are subject to limitations, which include their ability to simulate the flow conditions in urinary tract system, notably under conditions that permit the evaluation of crystal growth in real time. To this end, we have established a new platform to evaluate struvite growth at both macroscopic and microscopic length scales in the absence and presence of various modifiers.

Here, we will present the results of integrated microfluidics and in situ atomic force microscopy (AFM) measurements. Our findings demonstrate how these techniques serve as a useful platform to capture the time-resolved dynamics of crystal growth. A unique microfluidics platform creates an environment that mimics the flow conditions of a urinary tract system, while offering distinct advantages of bulk assays under quiescent conditions. Seeded growth decouples nucleation and growth, while the continuous supply of growth solution maintains constant composition without the depletion of solutes or the reduction in pH. We compare struvite growth under static and flowing conditions and evaluate growth kinetics and morphology transformation as a function of supersaturation. In parallel, we conduct in situ AFM measurements to elucidate the molecular mechanisms of struvite growth in the presence and absence of modifiers. As will be discussed, these integrated approaches have allowed us to identify modifiers that inhibit struvite formation and rationalize their molecular mechanisms.

1. Stickler, D. J. (2014). Clinical complications of urinary catheters caused by crystalline biofilms: something needs to be done. Journal of Internal Medicine, 276(2), 120-129.
2. Olszynski, M., Prywer, J., & Mielniczek-Brzóska, E. (2016). Inhibition of struvite crystallization by tetrasodium pyrophosphate in artificial urine: chemical and physical aspects of nucleation and growth. Crystal Growth & Design, 16(6), 3519-3529.