Role of E. coli-Secretion and Melamine in Selective Formation of CaC₂O₄·H₂O and CaC₂O₄·2H₂O Crystals

The influence of Escherichia coliform secretion (E. coli-secretion) and melamine on the crystallization of calcium oxalate has been investigated in order to determine its role in morphological control and the effects on the kinetics of the calcium oxalate crystals. The crystals obtained were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray powder diffraction, and thermal gravimetric analyzer. At the same time, conductivity meter and zeta potentiometer have been used to study the kinetic process of the crystal formation. The results show that, in the absence of E. coli-secretion, calcium oxalate monohydrate (COM) was obtained, which is the most stable crystal form of calcium oxalate and the major component of urinary stones, while in the presence of the secretion, the obtained crystals were calcium oxalate dehydrate (COD) instead of COM. Simulation experiments under artificial urine circumstance further demonstrated the drastic effect of E. coli-secretion on the calcium oxalate dihydrate crystal form. Furthermore, the acceleration effect of melamine on the formation of stones was also studied. Additionally, a slight influence of melamine on the crystallization of calcium oxalate has been found for the first time. Thus, a method to inhibit stone has been found and is expected to provide important data for the development of the calculi treatment.