Regulation of Potassium Aminocarboxylates on Calcium Oxalate Crystal Growth and Its Relationship with Molecular Structure

The effect of potassium aminocarboxylates on crystallization of calcium oxalate (CaOxa) was investigated in silica gel system by means of scanning electron microscopy and X-ray diffraction. These aminocarboxylates included potassium aminoacetate (KGLY), dipotassium glycoletherdiaminotetraacetate (K2EGTA), dipotassium aminotriacetate (K2NTA), dipotassium diethylenetriaminepenteacetate (K2DTPA), dipotassium ethylene diamine tetraacetate (K2EDTA) and dipotassium cyclohexanediamine tetraacetate (K2CDTA). All these aminocarboxylates could induce the formation of calcium oxalate dihydrate (COD), inhibit the aggregation of calcium oxalate monohydrate (COM) and decrease the specific surface area of COM aggregates. The ability to induce COD formation follows the order: K2DTPA (55wt%) > K2EDTA ≈K2CDTA (50wt%) > K2NTA (43wt%) >> K2EGTA (4wt%) > KGLY (2wt%), and the ability to inhibit COM aggregation follows the sequence: K2DTPA>K2NTA > K2CDTA≈ K2EDTA > K2EGTA > KGLY. These results are discussed in terms of their molecular structure, relative content of carboxylic groups, spatial location of carboxyl groups in aminocarboxylates, and their coordination capacity and modes with Ca ions. It is proved that K2NTA and K2DTPA can be the potential drugs for preventing the formation of CaOxa stones.