Sr incorporation in Ca-Phosphate glasses

• Grant number: 17/22188-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2018
• End date: March 31, 2019
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: José Fabián Schneider
• Grantee: Lucas Bins Ely Tsunaki
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass, AP.CEPID

Abstract

There are many therapeutic properties associated with the controlled release of Sr in the body. The introduction of Sr in bioglasses, partially replacing Ca, opened the possibility of developing materials with greater efficiency in bone regeneration, combining the bactericidal properties and the greater X-ray opacity of Sr. The feasibility of these applications is based on the similarity of structural chemistry between Ca2+ and Sr2+ cation, which allows the substitution of Ca in bioglass and hydroxyapatite. Frequently, it is considered that the substitution of Ca2+ by Sr2+ does not significantly alter the structure of the glass. However, recent results produced in our laboratory showed structural differences between the properties of Na-Sr and Na-Ca polyphosphate vitreous systems, both in the short-range scale (bonding of the alkaline earth with the network formers) and in the macroscopic scale (evolution of molar volume with composition). Another aspect of interest detected in the Na-Sr polyphosphates is the preferential bonding of Sr with the oxygen of the Q1-phosphate groups, chain terminators, up to a certain critical concentration of SrO. This property results in the non-random mixing of Na+ and Sr2+ cations in the glass network. In this project, it will be analyzed the structural properties of phosphate glass with Sr and Ca mixture, in order to test in which conditions and to what degree both ions can be considered homologous. Sodium poly- and meta-phosphates glasses will be considered, due to the previous knowledge of its structure and their relative simplicity compared to bioglasses, where besides phosphorous there is a second forming species, silicon. The structure at atomic scale will be analyzed with techniques of 31P and 23Na nuclear magnetic resonance, in parallel with the determination of macroscopic properties dependent on cation-O bonds (molar volume and glass transition temperature). The conclusions of this study are potentially relevant to develop strategies for the formulation of bioactive glasses with application as osteoimplants and as Sr-delivery agents for therapeutic purposes. (AU)