New Method for Obtaining Antimicrobial, Bismuth-Containing Apatite

A research team from the Department of Solid State Chemistry of the Lobachevsky University worked under Dr. Evgeny Bulanov to devise an innovative technique for obtaining bismuth-containing apatite.

With the aim of modeling the functioning of this material under operating conditions, the team has also analyzed its crystal structure as well as its thermodynamic characteristics.

Materials formed using compounds that have a crystalline structure of apatite have a broad array of applications - from fertilizers to ionic conductors. This is because nearly any element from the periodic table can be combined into the structure of these substances, which leads to variations in the performance of the material.

Hydroxyapatite, which has the formula Ca5(PO4)3OH, is largely used in the field of medicine as the source for materials applied to revive bone tissue. It is similar to the inorganic component found in bone, both structurally and chemically.

For nearly a decade, this compound and its analogs have been studied at the UNN Department of Solid State Chemistry. One of the most recent accomplishments is the incorporation of bismuth atoms into the crystal structure of the compound. Bismuth and its compounds demonstrate antimicrobial activity; hence, bismuth-containing apatite can be used to synthesize a material with biocompatibility as well as antimicrobial characteristics.

The team put forward a solid-phase synthesis process to produce the substance, allowing the process temperature to be considerably decreased when compared with the literature data. The Rietveld method was used for refining the crystalline structure of the compound, which enabled the determination of the distribution of atoms along crystallographic positions. This distribution must be known for subsequently elaborating on the properties of the substance.

Evgeny Bulanov, a senior researcher at the UNN Department of Solid State Chemistry, reiterated that for biomaterials, although finding ways for producing a substance is important, gaining insights into the behavior of the material under service conditions is equally important.

Thermodynamic modeling can give the answer to this question. The experimentally determined standard thermodynamic functions of bismuth-containing apatite will be used to analyze possible transformations of the substance already implanted into the human body. It is necessary for predicting possible negative consequences (destruction of the material caused by a change in its phase composition).

Evgeny Bulanov, Senior Researcher

The researchers from Lobachevsky University have found out several anomalous variations in the characteristics of the materials in the low-temperature region—such as an increase in the heat capacity at temperatures below 8 K, and the formation of a superstructure in the region of 173 K—which need further investigation.

The UNN Department of Solid State Chemistry performed this research in collaboration with colleagues from the Nanyang Technological University, Singapore. The results have been reported in an article titled “Bi-apatite: synthesis, crystal structure and low-temperature heat capacity,” published in the Journal of Chemical Thermodynamics.

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