Titanium(IV) oxo-complexes with α-hydroxy acid ligands: their structure, antimicrobial and cytotoxic properties


Titanium(IV) oxo complexes (TOCs) are known for structural diversity and photocatalytic activity. It is possi-ble to obtain TOCs with cores containing from 2 to 44 titanium atoms. Usually TiaOb cores are stabilized by alkoxide groups as well as carboxylate, phosphonate, β-diketonate, β-ketoester, and sulfonate ligands. The use of α-hydroxy acids (α-HA) as stabilizing factor seems to be interesting because of increased coordina-tion possibilities with Ti(IV) and from biological point of view due to their anti-inflammatory and antimicrobial properties. The aim of research was the synthesis of TOCs with a core stabilized with α-hydroxy acids, spectroscopic characterization of the obtained compounds, preparation of composite materials by dispersing TOCs in poly(methyl methacrylate) (PMMA) and testing their antibacterial properties and cytotoxicity. Titanium(IV) oxo-complexes were obtained under an inert atmosphere, by mixing titanium(IV) isopropoxide with mandelic, 9-hydroxy-9-fluorenecarboxylic or propionic acid. Composite materials were obtained by introducing 2%, 5%, 10%, 20% TOCs into a PMMA matrix. The obtained composites were examined by Ra-man and IR spectroscopy. Microbiological tests were carried out for the following bacteria: Escherichia coli, Staphylococcus aureus and Candida albicans yeasts. MTT tests conducted on the L929 murine fibroblast cell line were carried out to estimate cytotoxicity. Our results confirmed that the reaction of titanium alkoxides with α-hydroxy acids allows obtaining TOCs whose core is stabilized by both the interactions of the carboxylate group and the hydroxyl group. Two mech-anisms of the microbiological action of TOCs are postulated: (i) related to the photocatalytic activity of the oxo complex and (ii) caused by structural factors, especially the formation of chelate rings. The obtained materials do not exhibit cytotoxicity. These compounds and their composites can be utilized as an antibacterial coating in public facilities or hospi-tals to mitigate the risk of bacterial infections.

2nd International Conference on Advanced Materials for Bio-Related Applications