Agglomeration of urinary nanocrystallites: Key factor to formation of urinary stones

With transmission electron microscopy (TEM) and nanoparticle size analyzer, comparative studies were conducted on the property variation of nanocrystallites in the urine of 5 lithogenic patients and 5 healthy subjects following the placement time (t1). These properties include average particle size (d̄), size distribution, intensity–autocorrelation function, Zeta potential (ζ) and aggregation state. With the prolongation of t1 from 0 h to 4 h, d̄ value of the nanocrystallites in urine of lithogenic patients increased from 742 nm to 1667 nm, the autocorrelation time increased from 7.68 ms to 1050 ms and ζ decreased from −1.52 mV to −4.44 mV, respectively; the autocorrelation curves were of fluctuating and unsmooth, and TEM showed that most of the patient's urinary nanocrystallites were in aggregation state and three types of agglomeration were observed. However, for nanocrystallites in urine of healthy subjects, there was little variation in the above properties within 4 h. The autocorrelation curves were of regular and smooth, and TEM showed that healthy urinary nanocrystallites were well-dispersed. The above results show that the nanocrystallites in urine of healthy subjects can keep stability, whereas those of lithogenic patients are easier to agglomerate gradually; and the agglomeration of urinary nanocrystallites is the key factor to stone formation.