Yunfei Niu

In vitro degradability, bioactivity and cell responses to mesoporous magnesium silicate for the induction of bone regeneration

Mesoporous magnesium silicate (m-MS) was synthesized, and the in vitro degradability, bioactivity and primary cell responses to m-MS were investigated. The results suggested that the m-MS with mesoporous channels of approximately 5nm possessed the high specific surface area of 451.0m(2)/g and a large specific pore volume of 0.41cm(3)/g compared with magnesium silicate (MS) without mesopores of 75m(2)/g and 0.21cm(3)/g, respectively. The m-MS was able to absorb a large number of water, with water absorption of 74% compared with 26% for MS. The m-MS was also degradable in a Tris-HCl solution, with a weight loss ratio of 40wt% after a 70-day immersion period. The m-MS exhibited good in vitro bioactivity, inducing apatite formation on its surfaces after soaking in simulated body fluid (SBF) at a faster rate than observed for MS. The m-MS surface clearly promoted the proliferation and differentiation of MC3T3-E1 cells, and their normal cell morphology indicated excellent cytocompatibility. This study suggested that mesoporous magnesium silicate with a high specific surface area and pore volume had suitable degradability and good bioactivity and biocompatibility, making it an excellent candidate biomaterial for the induction of bone regeneration.

Bioactive and degradable scaffolds of the mesoporous bioglass and poly(L-lactide) composite for bone tissue regeneration

Bioactive scaffolds of the mesoporous bioglass (m-BG) and poly(l-lactide) (PLLA) composite were fabricated using a solvent casting-particulate leaching method. The results showed that incorporation of the m-BG into PLLA significantly improved the in vitro water absorption, degradability and apatite-formation ability of the m-BG-PLLA composite scaffolds, which were m-BG content dependent. Moreover, addition of the m-BG into PLLA could neutralize the acidic degradation products of PLLA and thus compensate for the decrease of the pH value. In cell culture experiments, the results revealed that the m-BG-PLLA composite scaffolds enhanced attachment, proliferation and alkaline phosphatase (ALP) activity of MC3T3-E1 cells, which were m-BG content dependent. In animal experiments, the SRmCT and histological elevation results showed that the composite scaffolds significantly improved osteogenesis in vivo. It can be suggested that incorporation of bioactive materials of m-BG into PLLA was a useful approach to obtain composite scaffolds with improved properties (such as water absorption, degradability, bioactivity and osteogenesis), and the composite scaffolds with excellent biocompatibility could be promising bioactive implants for bone regeneration.

Degradability, bioactivity, and osteogenesis of biocomposite scaffolds of lithium-containing mesoporous bioglass and mPEG-PLGA- b -PLL copolymer

Biocomposite scaffolds of lithium (Li)-containing mesoporous bioglass and monomethoxy poly(ethylene glycol)-poly(D,L-lactide-co-glycolide)-poly(L-lysine) (mPEG-PLGA-b-PLL) copolymer were fabricated in this study. The results showed that the water absorption and degradability of Li-containing mesoporous bioglass/mPEG-PLGA-b-PLL composite (l-MBPC) scaffolds were obviously higher than Li-containing bioglass/mPEG-PLGA-b-PLL composite (l-BPC) scaffolds. Moreover, the apatite-formation ability of l-MBPC scaffolds was markedly enhanced as compared with l-BPC scaffolds, indicating that l-MBPC scaffolds containing mesoporous bioglass exhibited good bioactivity. The cell experimental results showed that cell attachment, proliferation, and alkaline phosphatase activity of MC3T3-E1 cells on l-MBPC scaffolds were remarkably improved as compared to l-BPC scaffolds. In animal experiments, the histological elevation results revealed that l-MBPC scaffolds significantly promoted new bone formation, indicating good osteogenesis. l-MBPC scaffolds with improved properties would be an excellent candidate for bone tissue repair.

Mesoporous magnesium silicate-incorporated poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) bioactive composite beneficial to osteoblast behaviors

Mesoporous magnesium silicate (m-MS) and poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL) composite (m-MPC) was synthesized by solvent casting method. The results suggest that the mechanical properties of compressive strength and elastic modulus, as well as hydrophilicity, of the m-MPC increased with increase of m-MS content in the composites. In addition, the weight loss of the m-MPC improved significantly with the increase of m-MS content during composite soaking in phosphate-buffered saline for 10 weeks, indicating that incorporation of m-MS into PCL-PEG-PCL could enhance the degradability of the m-MPC. Moreover, the m-MPC with 40 w% m-MS could induce a dense and continuous apatite layer on its surface after soaking in simulated body fluid for 5 days, which was better than m-MPC 20 w% m-MS, exhibiting excellent in vitro bioactivity. In cell cultural experiments, the results showed that the attachment and viability ratio of MG63 cells on m-MPC increased significantly with the increase of m-MS content, showing that the addition of m-MS into PCL-PEG-PCL could promote cell attachment and proliferation. The results suggest that the incorporation of m-MS into PCL-PEG-PCL could produce bioactive composites with improved hydrophilicity, degradability, bioactivity, and cytocompatibility.

Effects of hydrothermal treatment on the properties of nanoapatite crystals

We report the synthesis of nanoapatite crystals via a hydrothermal reaction of hydroxyapatite precipitates. The impact of the reaction conditions on the properties of the crystals obtained were evaluated. The hydrothermal reaction that takes place markedly affected the crystallinity, morphology, and size of the nanoapatite crystals formed. High crystallinity and large crystal size were obtained at higher hydrothermal temperatures and longer hydrothermal reaction times. The nanoapatite crystals were needle-like when prepared under ambient pressure conditions and rod-like when prepared under increased pressure. The crystals prepared at ambient pressure had a larger aspect ratio compared with those prepared under increased pressure. The aging time of the initial hydroxyapatite precipitate significantly affected growth of the nanoapatite crystals. With other hydrothermal reaction conditions being equal, the fresh hydroxyapatite precipitate produced notably larger crystals than the aged hydroxyapatite precipitate. The influence of apatite morphology on osteoblast viability was studied by MTT assay. The results indicate that the rod-like apatite showed a better biological response than needle-like apatite in promoting cell growth. Transmission electron microscopy showed that large quantities of needle apatite entered into cells and damaged their morphology.

Preparation and osteogenic properties of magnesium calcium phosphate biocement scaffolds for bone regeneration

The regenerative treatment of large osseous defects remains a formidable challenge in today. In the present study, we have synthesized biodegradable magnesium calcium phosphate biocement (MCPB) scaffolds with interconnected macroporous structure (100-600 mu m), as well as good bioactivity, biocompatibility and proper degradatibility. The results revealed that the porosity increased from 52% to 80% of MCPB scaffolds while the compressive strength decreased from 6.1MPa to 1.2MPa. We further assessed the effects of scaffolds on the rabbit femur cavity defect model in vivo by using synchrotron radiation X-ray microCT and microCT imaging, indicating that the MCPB scaffolds underwent gradually degradation and promoted the extensive neo-bone formation.

Zein regulating apatite mineralization, degradability, in vitro cells responses and in vivo osteogenesis of 3D-printed scaffold of n-MS/ZN/PCL ternary composite

Bioactive and degradable scaffolds of nano magnesium silicate (n-MS)/zein (ZN)/poly(caprolactone) (PCL) ternary composites were prepared by 3D-printing method. The results showed that the 3D-printed scaffolds possessed controllable pore structure, and pore morphology, pore size, porosity and pore interconnectivity of the scaffolds can be efficiently adjusted. In addition, the apatite-mineralization ability of the scaffolds in simulated body fluids was obviously improved with the increase of ZN content, in which the scaffold with 20 w% ZN (C20) possessed excellent apatite-mineralization ability. Moreover, the degradability of the scaffolds was significantly enhanced with the increase of ZN content in the scaffolds. The degradation of ZN produced acidic products that could neutralize the alkaline products from the degradation of n-MS, which avoid the increase of pH value in degradable solution. Furthermore, the MC3T3-E1 cells responses (e.g. proliferation and differentiation, etc.) to the scaffolds were significantly promoted with the increase of ZN content. The in vivo osteogenesis of the scaffolds implanted the femur defects of rabbits was investigated by micro-CT and histological analysis. The results demonstrated that the new bone formation was significantly enhanced with the increase of ZN content, in which the C20 scaffold induced the highest new bone tissues, indicating excellent osteogenesis. The results suggested that the ZN in the ternary composite scaffolds played key roles in assisting bone regeneration in vivo.

Retracted Article: Cell orientation, proliferation, and differentiation on poly(L-lactide) spherulites

The ringless spherulites of poly(L-lactide) (PLLA), fabricated via isothermal crystallization at temperatures of 100 °C and 140 °C (PLLA100 and PLLA140, respectively), were used to evaluate the effect of spherulites on MC3T3-E1 cell functions, including adhesion, proliferation, and differentiation. The atomic force microscopy (AFM) images indicated that PLLA100 presented a ridge width of 50–100 μm and a ride depth of 50–100 nm, whereas the values of PLLA140 were 25–50 μm and 100–350 nm, respectively. The cytoskeleton and nuclear alignment were observed on PLLA140, while no alignment was found on PLLA100. More interestingly, MC3T3-E1 cell proliferation and differentiation were also promoted significantly on PLLA140 compared with PLLA100. Our results, undoubtedly, provide a fundamental understanding regarding the effects of polymer spherulites on cell functions.