Search

The creep and recovery and the stress relaxation behaviors of poly(butylene adipate-co-terephthalate) (PBAT) and polyhydroxyalkanoates (PHA) binary blends incorporating 30 wt % of a mixture of trisilanolisobutyl polyhedral oligomeric silsesquioxanes (POSS) and calcium phosphate glass (CaP-g) were investigated under simulated physiological and human body temperature conditions. The synergistic effect of PHA and CaP-g/POSS filler remarkably improved the creep behavior of the PBAT matrix and decreased its residual strain, consequently enhancing its elastic recovery. A considerable increase of the relaxation modulus of the hybrid materials was also observed upon incorporation of PHA and CaP-g/POSS. The relaxation modulus of the neat PBAT sample increased from ~60 MPa to ~1600 MPa after addition of 30 wt % CaP-g/POSS and 70 wt % PHA. However, after exposure of the composites to the simulated human body conditions for 14 days, a drop of dynamic mechanical properties of the studied material systems was observed along with formation of a desirable calcium phosphate phase on the material surface. The long-term (i.e., up to 7 × 10 5  s) viscoelastic behavior of the studied materials was successfully predicted using the time-temperature superposition principle and the obtained creep strain and the relaxation modulus master curves were satisfactorily fitted to the Findley power law equation and the generalized Maxwell model, respectively. This study demonstrates a facile method for tailoring CaP-g/POSS bioactive glasses composition for bone-like apatite formation on biopolymer surfaces. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2419-2432, 2019., (© 2019 Wiley Periodicals, Inc.)

Phosphate-based glasses (PBGs) are ideal materials for regenerative medicine strategies because their composition, degradation rates, and ion release profiles can easily be controlled. Strontium has previously been found to simultaneously affect bone resorption and deposition. Therefore, by combining the inherent properties of resorbable PBG and therapeutic activity of strontium, these glasses could be used as a delivery device of therapeutic factors for the treatment of orthopaedic diseases such as osteoporosis. This study shows the cytocompatibility and osteogenic potential of PBGs where CaO is gradually replaced by SrO in the near invert glass system 40P 2 O 5 ·(16-x)CaO·20Na 2 O·24MgO·xSrO (x = 0, 4, 8, 12, and 16 mol%). Direct seeding of MG63 cells onto glass discs showed no significant difference in cell metabolic activity and DNA amount measurement across the different formulations studied. Cell attachment and spreading was confirmed via scanning electron microscopy (SEM) imaging at Days 3 and 14. Alkaline phosphatase (ALP) activity was similarly maintained across the glass compositions. Follow-on studies explored the effect of each glass composition in microsphere conformation (size: 63-125 μm) on human mesenchymal stem cells (hMSCs) in 3D cultures, and analysis of cell metabolic activity and ALP activity showed no significant differences at Day 14 over the compositional range investigated, in line with the observations from MG63 cell culture studies. Environmental SEM and live cell imaging at Day 14 of hMSCs seeded on the microspheres showed cell attachment and colonisation of the microsphere surfaces, confirming these formulations as promising candidates for regenerative medicine strategies addressing compromised musculoskeletal/orthopaedic diseases., (© 2019 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.)

Novel CaO-P 2 O 5 -Nb 2 O 5 -Ag 2 O invert glasses with substitution Ag 2 O for Nb 2 O 5 were successfully prepared using a melt-quenching method. Ag 2 O in the glasses act as a network modifier oxide, playing the same role as Na 2 O, which breaks the phosphate chains. Analysis of the ultraviolet-visible absorption spectra of the glasses showed that the glass matrix contained ionic silver species and silver nanoparticles. Approximately 0.05 mM of Nb 5+ ions released from the glasses, which would be expected to stimulate osteoblast differentiation. A glass containing 1 mol % Ag 2 O showed a linear increase in the releasing amount of Ag + ions with increasing soaking time, whereas glasses containing 3-5 mol % Ag 2 O showed Ag + ion concentrations of around 13 μM at day 3, and then maintained similar values until day 7. When the solution was replaced with fresh solution every 2 days, the Ag + ion dissolution amounts indicated almost constantly 13 μM due to AgCl formation. There were no differences in the numbers of primary osteoblast cells on silver-free and silver-containing glasses after cultivation for 1-7 days. The silver-containing calcium phosphate invert glasses showed cytocompatibility with simultaneous antibacterial activity to Escherichia coli and Staphylococcus aureus. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3127-3135, 2017., (© 2017 Wiley Periodicals, Inc.)

We have developed a calcium phosphate glass (CPG) doped with Zn(2+) or F(-) or combined Zn(2+) and F(-) ions, which are naturally found in the human body and play a dual role in bone formation and antibacterial activity. Previously, we have demonstrated that this family of CPGs has superior osteoconductive and resorbable properties in vivo. This study aimed to investigate the antibacterial property of CPGs incorporating Zn(2+) and/or F(-) . We used Streptococcus mutans as a model organism because it is one of the major human oral pathogens and an early colonizer, and it has been associated with several oral infections, such as dental caries, periodontitis, and peri-implantitis. CPGs of 0.01 and 0.05 g were incubated with S. mutans for 0, 2, 4, and 6 h. Serial dilutions were plated in triplicate and colony forming units were determined. The antimicrobial effect of CPG incorporating Zn(2+) or F(-) was greater than CPG incorporating both these ions. CPG without doping produced a moderate antimicrobial effect. This family of CPGs, previously shown to promote new bone formation in vivo, is demonstrated to have superior bactericidal properties., (Copyright © 2013 Wiley Periodicals, Inc.)