Interaction of salicylic acid and its derivates with calcite crystals of different morphologies

Ukrainczyk, Marko (2012) Interaction of salicylic acid and its derivates with calcite crystals of different morphologies. Doctoral thesis, Sveučilište u Zagrebu, Prirodoslovo-matematički fakultet.

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Abstract

Investigation of basic interactions between calcium carbonates and active pharmaceutical compounds is of great importance because of the possibility to use the carbonates as a mineral carrier in drug delivery systems. In this study the mode and extent of interactions of small organic molecules, chosen as pharmaceutically relevent model compounds, with calcite crystals of different morphologies are described. A method for the preparation of pure, monodispersed and well-defined calcite crystals in the Ca(OH)2(s)-H2O(l)-CO2(g) precipitation system was developed. Stearic acid, salicylic acid and its functional derivatives were used as model active pharmaceutical substances. Adsorption of stearate was studied by FT-IR spectroscopy, thermogravimetric analysis and hydrophobicity measurements. Minimal amount of stearate necessary to build up the monolayer and coresponding cross sectional area of one stearate molecule were estimated for different calcite morphologies. The crystal growth kinetics of well defined rhombohedral and scalenohedral calcite seed crystals in the systems containing salicylic acid, 5-aminosalicylic acid, N-salicyloil-L-aspartic acid or N-salicyloil-L-glutamic acid, were investigated. The analysis of the crystal growth kinetic parameters indicated that the crystal growth of calcite is controlled by integration of growth units into the spiral step. Growth rate of scalenohedral calcite is found to be lower than for rhombohedral calcite. The addition of functional salicylate derivates into the precipitation systems caused the inhibition of their growth as well as change of growth mechanism. Based on the kinetic parameters, conclusions on the mechanisms of interactions were gained. The results indicated that salicylate molecules preferentially adsorb along the steps on the growing calcite surfaces. The results of crystal growth kinetic experiments were additionally supported with the results of the appropriate adsorption, spectroscopic and acustophoretic measurements. The extent of adsorption of salicylates was determined. Chemical and conformational properties of used functional derivatives were correlated with different surface structures of calcite crystals.

Item Type:	Thesis (Doctoral thesis)
Uncontrolled Keywords:	adsorption; calcite; calcium carbonate; crystal growth kinetics; crystal surface structure; mineralk carrier of pharmaceutical substances; salicylic acid derivates; stearic acid
Subjects:	NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Chemistry > Physical Chemistry
Divisions:	Division of Materials Chemistry
Projects:	Project title Project leader Project code Project type Precipitation mechanisms of inorganic biocompatible and related materials (Mehanizmi taloženja anorganskih biokompatibilnih i srodnih materijala)- Damir Kralj 098-0982904-2951 MZOS
Depositing User:	Marko Ukrainczyk
Date Deposited:	12 Oct 2015 15:36
URI:	http://fulir.irb.hr/id/eprint/270

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