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Interactions of tripeptide derivatives of salicylic acid with calcite surfaces

One of the focuses in the field of materials chemistry is to design the systems that could be used for the controlled introduction and release of active pharmaceutical compounds in the living organisms and tissues. At that, a promising systems for controlled drug delivery is calcite, most stable polymorph of calcium carbonate, functionalized by small, biologically active molecules, like derivatives of salicylic acid (Sal). During biomineralization, CaCO3 precipitates as main inorganic component of invertebrate’s hard tissues. Such calcitic skeletal elements regularly contain small amounts of macromolecules. It has been shown previously that the isolated fragments of proteins extracted from mineralized tissue, which exert a significant influence on the morphology and crystal structure of CaCO3, contain high acidic regions, comprising mostly aspartic acid. In this respect, we decided to investigate the interactions of calcite functionalized with highly active biomolecules, in order to uncover the roles of their flexibility and chirality in potential composites suitable for drug delivery. Hence, we prepared salicylic acid- derived aspartic acid (Asp) tripeptides. In order to investigate influence of chirality on extent of organic/inorganic interaction different enantiomers of aspartic acid, N-Sal- linker-L-Asp-D-Asp-L-Asp (Sal-LDL) and N-Sal- linker-L-Asp-L-Asp-L-Asp (Sal-LLL), were employed in tripeptides. Salicylic acid was attached to tripeptides using linkers of various length. The interactions between synthesized molecules and the calcite surface was investigated using advanced simulation techniques and by crystal growth kinetic analyses. The Langmuir adsorption constants are calculated from kinetic data and used as an indication of extent of organic/inorganic interaction. Our results indicate that Sal-LDL adsorb better than Sal-LLL on calcite surface. The highest adsorption constant was found with the longest linker of CH2 group.

biomineralization ; calcite ; drug delivery ; salicilyc acid ; aspartic acid

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