Fabrication of a Novel Beta Tricalcium Phosphate/Sodium Alginate/Poly(D,L-lactic acid) Composite Microsphere and Its Drug Releasing Property.

Bone repair microspheres have been widely studied due to their convenience during clinical operations. In this study, beta tricalcium phosphate/sodium alginate/poly(D,L-lactic acid) (ß-TCP/SA/PDLLA) composite microspheres were successfully prepared using the liquid droplet method. Then, ß-TCP/SA/PDLLA composite microspheres were soaked in simulated body fluids (SBF) for 7 days, and tested in an X-ray diffractometer (XRD). The results indicated that sodium alginate (SA) and poly(D,L-lactic acid) (PDLLA) are not limiting factors for the transformation of ß-TCP to HA. Since sodium ions and bicarbonate ions were abundant, the final products were not pure HA but (Na, CO3)-substituted HA. When soaked in SBF, the structure of ß-TCP/SA/PDLLA composite microspheres remained stable for at least 14 days suggesting that their anti-washout ability was suitable. Furthermore, the absence of calcination during the preparation of ß-TCP/SA/PDLLA composite microspheres enabled the easy incorporation of vancomycin into the microspheres in situ at a final embedding ratio of 26.18%. Furthermore, the ß-TCP/SA/PDLLA composite microspheres possessed excellent sustained drug release capability, and the release of vancomycin (92.8 wt.%) lasted for almost 168 h. Our results suggest that the ß-TCP/SA/PDLLA composite microspheres could be used as a promising graft material particularly for bone repair.

Bacteriophage-Resistant Mutant of Enterococcus faecalis Is Impaired in Biofilm Formation.

Enterococcus faecalis is a common gram-positive non-spore-forming bacterium in nature and is found in the upper respiratory tract, intestine, and mouth of healthy people. E. faecalis is also one of the common pathogens causing nosocomial infections and is resistant to several antibiotics commonly used in practice. Thus, treating drug-resistant E. faecalis with antibiotics is challenging, and new approaches are needed. In this study, we isolated a bacteriophage named EFap02 that targets E. faecalis strain EFa02 from sewage at Southwest Hospital. Phage EFap02 belongs to the Siphoviridae family with a long tail of approximately 210 nm, and EFap02 can tolerate a strong acid and alkali environment and high temperature. Its receptor was identified as the capsular polysaccharide. Phage-resistant mutants had loss-of-function mutations in glycosyltransferase (gtr2), which is responsible for capsular polysaccharide biosynthesis, and this caused the loss of capsular polysaccharide and interruption of phage adsorption. Although phage-resistant mutants against EFap02 can be selected, such mutants are impaired in biofilm formation due to the loss of capsular polysaccharide, which compromises its virulence. Therefore, this study provided a detailed description of the E. faecalis EFap02 phage with the potential for treating E. faecalis infection.

Enhanced osteogenesis and angiogenesis of calcium phosphate cement incorporated with zinc silicate by synergy effect of zinc and silicon ions.

Calcium phosphate cement (CPC) with good injectability and osteoconductivity plays important roles in bone grafting application. Much attention has been paid to achieve multifunctionality through incorporating trace elements into CPC. Silicon and zinc can be used as additives to endow CPC with biological functions of osteogenesis, angiogenesis and anti-osteoclastogenesis. In this study, zinc and silicate ions were co-incorporated into CPC through mixing with submicron zinc silicate (Zn2SiO4, ZS) to obtain zinc silicate-modified CPCs (ZS/CPCs) with different contents. The results revealed that the addition of ZS increased the compressive strength, prolonged the setting time, and densified the structure of CPC. Low addition content of ZS facilitated the formation of surface apatite layer in the early mineralization stage. Incorporating ZS significantly induced osteogenesis of mouse bone marrow stromal cells (mBMSCs) and angiogenesis of human umbilical vein endothelial cells (HUVECs), and moreover, restricted osteoclastogenesis of Raw 264.7 in vitro. Silicate and zinc ions could be steadily released from ZS/CPCs into the culture medium. With the synergistic effect of silicate and zinc ions, ZS/CPCs provided an appropriate microenvironment for the immune cells to facilitate the osteogenesis of mBMSCs and angiogenesis of HUVECs further. Taken together, it can be concluded that incorporating ZS is an effective way to endow CPC with multifunctionality and better bone regeneration for bone defect repair.

Zinc doping induced differences in the surface composition, surface morphology and osteogenesis performance of the calcium phosphate cement hydration products.

In order to investigate the influence of Zn on the hydration reaction of calcium phosphate cement (CPC), the incompletely hydrated CPC tablets were kept soaking in varying zinc-containing tris-(hydroxymethyl)-aminomethane/hydrochloric acid (Zn-Tris-HCl) buffers. It was found that Zn could retard the CPC hydration, the inhibitory effect was in direct proportional to the Zn content in the Zn-Tris-HCl buffer, and overhigh concentration of Zn (≧800 µM) caused the CPC hydration products having different phase composition and surface morphology. Cell culture experimental results revealed the CPC tablets which were soaked in the Zn-Tris-HCl buffer containing relative low Zn content (≦320 µM) favored the mouse bone mesenchymal stem cells (mBMSCs) spreading. When Zn-doped CPC tablets released 10.91 to 27.15 µM of zinc ions into the cell culture medium, it greatly contributed to the improvement of the proliferation ability and the alkaline phosphatase (ALP) activity of the mBMSCs. In the same case, the expression of osteogenesis related genes such as collagen I and runt-related transcription factor 2 was remarkably up-regulated as well. However, the release of high concentration of Zn (128.58 µM) would significantly reduce the ALP activity of the mBMSCs. Therefore, Zn not only facilitates osteogenesis but also affects the CPC hydration behavior, and the CPC with suitable Zn dosage concentration has great potentials to be used for clinical bone repairing.

Auto-degradable and biocompatible superparamagnetic iron oxide nanoparticles/polypeptides colloidal polyion complexes with high density of magnetic material.

HYPOTHESIS: Superparamagnetic iron oxide nanoparticles (SPIONs) are extensively used as building block of colloidal nanocomposites for biomedical applications. Strategies employed to embed them in a biodegradable and biocompatible polymer matrix often fail to achieve a high density of loading which would greatly benefit to applications such as imaging and hyperthermia. In this study, poly(acrylic acid) coated SPION (γ-Fe2O3-PAA) are self-assembled with hydrolysable poly(serine ester) by electrostatic complexation, leading to perfectly defined spherical particles with ultra-high density of magnetic material and an ability to auto-degrade into individual SPION and biocompatible byproducts. EXPERIMENTS: Self-assembly and auto-degradation of γ-Fe2O3-PAA/poly(serine ester) and γ-Fe2O3-PAA/poly(serine ester)-b-PEG colloidal particles are studied by light scattering and microscopy. Colloidal stability in bio-fluids, hyperthermia under alternating magnetic field, cellular uptake, cytotoxicity and degradation of γ-Fe2O3-PAA/poly(serine ester)-b-PEG in living cells are investigated. FINDINGS: A remarkably slow electrostatic complexation leads to dense superparamagnetic γ-Fe2O3-PAA/poly(serine ester)-b-PEG polyion complexes (PICs) with controlled sizes (150-500 nm) and times of degradation in aqueous solvents (700-5000 h). The material shows good sustainability during hyperthermia, is well taken up by MC3T3 cells and non-cytotoxic. TEM images reveal a mechanism of degradation by "peeling" and fragmentation. In cells, PICs are reduced into individual SPIONs within 72 h.

Enhanced biocompatibility and osseointegration of calcium titanate coating on titanium screws in rabbit femur.

This study aimed to examine the biocompatibility of calcium titanate (CaTiO3) coating prepared by a simplified technique in an attempt to assess the potential of CaTiO3 coating as an alternative to current implant coating materials. CaTiO3-coated titanium screws were implanted with hydroxyapatite (HA)-coated or uncoated titanium screws into medial and lateral femoral condyles of 48 New Zealand white rabbits. Imaging, histomorphometric and biomechanical analyses were employed to evaluate the osseointegration and biocompatibility 12 weeks after the implantation. Histology and scanning electron microscopy revealed that bone tissues surrounding the screws coated with CaTiO3 were fully regenerated and they were also well integrated with the screws. An interfacial fibrous membrane layer, which was found in the HA coating group, was not noticeable between the bone tissues and CaTiO3-coated screws. X-ray imaging analysis showed in the CaTiO3 coating group, there was a dense and tight binding between implants and the bone tissues; no radiation translucent zone was found surrounding the implants as well as no detachment of the coating and femoral condyle fracture. In contrast, uncoated screws exhibited a fibrous membrane layer, as evidenced by the detection of a radiation translucent zone between the implants and the bone tissues. Additionally, biomechanical testing revealed that the binding strength of CaTiO3 coating with bone tissues was significantly higher than that of uncoated titanium screws, and was comparable to that of HA coating. The study demonstrated that CaTiO3 coating in situ to titanium screws possesses great biocompatibility and osseointegration comparable to HA coating.