Calcium pyrophosphate is of great importance not only for industrially but also for clinical studies by reason of its formation in the human body. There are many clinical studies on determining calcium pyrophosphate forms, especially because of causing pseudogout disease, which is one of the most common types of arthritis, also known as calcium pyrophosphate crystal accumulation. In the literature, it has been suggested that calcium pyrophosphate crystallized in the form of calcium pyrophosphate dihydrate (CPPD) in the joint tissues of arthritis patients. Although there are many studies in the literature on the synthesis and characterization of CPPD, there are limited studies on the growth and dissolution of calcium pyrophosphate crystals. It is a known fact that the physical properties of the crystal product in a crystallization process depend on the operating conditions as well as on the additives. In this study, the effect of citric acid, which is one of the carboxylic acids, was investigated on CPPD crystallization. Citric acid is taken from fruits naturally in our daily diet, and therefore it is known that usage of it as an additive does not constitute an impediment in terms of human health. Firstly, the influence of the residence time (τ) was examined, and the results showed that the dependency of the average particle size on the τ value disappeared after a certain value. The growth kinetic of CPPD crystals was analyzed in accordance with size-independent and size-dependent growth models. It was suggested that the growth rates of CPPD crystals depend on the particle size, and it was found that the M-4 model is the best model to characterize the experimental data statistically. The morphology of crystals was examined under the light microscope, and plate-like structures and rod-shaped crystals were obtained and that they could be characterized by agglomerated structures. Almost all crystals transformed into spherical agglomerated structures in the presence of citric acid and the average particle size increased based on these structures. Kinetic evaluations also supported transformation into agglomerated structures totally. In sum, it may be concluded that the patients with pseudogout should take into account the citric acid consumption in their daily diet based on this in vitro study.
Anahtar Kelimeler: Calcium pyrophosphate dihydrate, Crystallization kinetics, Morphology, Citric acid