Influence of the Insoluble and Soluble Matrix of Abalone Nacre on the Growth of Calcium Carbonate Crystals

Abstract

During the growth process of the nacre layer in abalone shells, aragonite platelets are built into a preformed organic matrix. This matrix consists of chitin and different proteins that may affect the morphology and the crystal structure of the developed platelets. The organic matrix can be divided into two fractions: the soluble and the insoluble matrix. The soluble matrix has influence on the precipitation rates of calcium carbonate crystals and also the insoluble matrix affects crystal growth. In this work we investigated the collective influence of soluble and insoluble matrix in a crystallization device which contained the insoluble matrix and was flowed through by CaCl2 and NaHCO3 solutions. The presence of 0.02 μg/mL soluble matrix promoted the growth of flat CaCO3 crystals on the surface layers of the insoluble matrix of Haliotis laevigata. The crystals could be identified as aragonite using electron diffraction in the transmission electron microscope (TEM). Furthermore the addition of 1 μg/mL soluble matrix inhibited largely crystal growth on the surface of the insoluble matrix. Our findings indicate that components of the soluble matrix are required for a controlled nucleation and growth of flat aragonite crystals on the insoluble matrix.

In vitro growth of flat aragonite crystals between the layers of the insoluble organic matrix of the abalone Haliotis laevigata

“…The influence of this addition on the probability of crystal growth was presented in a previous paper [8]. A direct influence on the results presented in the present paper was not observed.…”

“…1 shows a sketch of the cross section of the crystallization device. A photograph and a plane view sketch of the crystallization device were already presented in previous publications [8,11]. By placing a punched out piece of the insoluble organic matrix with a diameter of 14 mm and a neoprene ring (inner and outer diameter: 12 mm and 14 mm, height: 0.48 mm) as a spacer in the middle of the crystallization device, it was divided into two compartments.…”

“…A more detailed description and images of this procedure are provided in a previous publication [8].…”

“…In abalone nacre the mineral and the organic phase do not grow in an alternating manner but the aragonite platelets grow in the preformed layers of the interlamellar organic matrix [4][5][6][7][8]. These preformed organic matrix layers are soaked by the extrapallial fluid containing ions as well as proteins that are incorporated into the shell during the growth process.…”

“…In a previously published paper we already documented the in vitro growth of flat aragonite crystals on the insoluble organic matrix of abalone Haliotis laevigata [8] using a crystallization device. This growth process took place in the presence of different concentrations of the soluble organic matrix.…”