Study of inhibition mechanisms of glycosaminoglycans on calcium oxalate monohydrate crystals by atomic force microscopy

Atomic force microscopy (AFM) was applied to the (-101) faces of calcium ox alate monohydrate (COM) crystals grown from calcium oxalate (CaOx) solution s. Microstructures of many spiral hillocks with step height of 1 nm were ob served on the faces. Then using AFM in situ, we analysed the re-growth proc ess of the spiral steps on the face of COM seed-crystals in CaOx growth sol utions that contained growth inhibitors of glycosaminoglycans and studied t heir inhibition mechanisms on COM crystals. The total morphology of the fac es of COM seed crystals re-grown in the CaOx growth solutions was assessed by scanning electron microscopy (SEM). In the growth solution without glyco saminoglycans (control experiment) or with chondroitin sulphate (ChS), AFM images and SEM micrographs of the faces of the re-grown seed crystals showe d two-dimensional (2D) nucleation although 2D nucleation was delayed in the presence of ChS. However, the addition of dermatan sulphate (DS) to the gr owth solution resulted in isotropic growth by a step flow mode and spiral m echanism. With regard to the main inhibition mechanisms of two glycosaminog lycans (ChS and DS) on COM crystals, it can be concluded from these results that ChS delays 2D nucleation and DS inhibits 2D nucleation.