Optimization of Ca2+ content in alginate hydrogel injected in myocardium.

The spontaneous uptake of Ca2+ -ions is a unique property of alginate hydrogels, which, along with their high biocompatibility, disintegration (approximately within 2 weeks), and morphological similarity to heart tissue, makes them attractive as scaffolding materials in therapies in infarct myocardium. To shed light on the aforementioned ability, thorough theoretical calculations were carried out with the density functional theory (DFT) method. The influence of Ca-content οn the molecular structure and the thermodynamic stability of the alginate hydrogel was determined; what is more, these results effectively interpreted the experimental findings, as well. This analysis suggests that in Ca-free or Ca-deficient alginates spontaneous Ca2+ cations uptake can occur from the biological environment and develop, via chelation reaction, a well-formed and thermodynamically stable hydrogel in situ inside the tissue. The highest degree of cross linking results in viscosity peak. Nevertheless, further increase of Ca-content in alginate structure beyond this peak results in products with poorer thermodynamic stability. Structural optimization DFT calculations revealed that the destabilization of the Ca-rich alginate hydrogels is attributed to changes of the alginate chain molecule, which are relaxation, weakening, and eventually total collapse of the bond between the units of the alginate chain. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 223-231, 2019.

Structural and Theoretical Study of Strontium Borophosphate Glasses Using Raman Spectroscopy and ab Initio Molecular Orbital Method.

Strontium borophosphate glasses of composition xSrO·(1 - x)·[0.68B2O3·0.32P2O5], 0.40 ≤ x ≤ 0.68, have been prepared by fast quenching of high-temperature melts and studied using Raman spectroscopy. In order to comprehend and confirm the obtained spectroscopic Raman data, crystalline compounds and glass-ceramics of analogous compositions were also prepared and studied. Also, ab initio molecular electronic structure theory was used to predict and confirm the experimental vibrational spectra The comparison between theoretical and experimental results showed a good overall agreement. The analysis has focused on a new detailed interpretation of the P-O-B Raman bands. Also, the analysis has revealed a divergent modification of the reported glasses near the meta-stoichiometry where the dominant species in the glass network were found to be borophosphate chains [BP2O9]5-, pyrophosphate P2O74-, and orthophosphate PO43- units.