Siloxane-containing Vaterite Research Articles

Protein adsorption behaviors on siloxane-containing vaterite particles

The adsorption properties of two types of proteins, i.e., acidic bovine serum albumin (BSA) and basic lysozyme (LSZ), on siloxane-containing vaterite particles (SiV) were examined. SiV particles showing a positive zeta potential of 44 mV electrostatically adsorbed ~ 40 mg/g of negatively charged BSA in Tris buffer solution after soaking for 2 weeks. LSZ adsorption on SiV particles was 14 mg/g in 2 weeks, despite it being a positively charged protein. The adsorption of LSZ can be explained via the rapid dissolution of amorphous calcium carbonate phase and reprecipitation of positively charged calcite phase. SiV might be effective for designing biomaterials owing to high adsorption affinity for both, acidic as well as basic proteins.

Oriented siloxane-containing vaterite/poly(lactic acid) composite scaffolds for controlling osteoblast alignment and proliferation

ABSTRACTBone tissue has an anisotropic structure, which is strongly associated with the collagen fibril orientation and the direction of the c-axis of the bone apatite crystal. The bone regeneration process contains two main phases: bone mineral density (BMD; bone quantity) restoration and reconstruction of the bone apatite c-axis orientation (bone quality), which is the dominant factor for the mechanical properties of bone. Hence, restoration of the bone quality and quantity is required for bone tissue regeneration. In this work, novel, oriented siloxane-containing vaterite/poly(lactic acid) composite scaffolds were developed by controlling the cell alignment and proliferation, which play an important role in regenerating the bone quality and quantity, respectively. Our strategy controlled the cell alignment and proliferation using a morphological design of the scaffolds and the ions released from the siloxane-containing vaterite. The scaffolds were designed to control of the cell alignment, which successfully induced cell orientation along the fibermats. In addition, the released ions from the siloxane-containing vaterite improved osteoblast proliferation, indicating that the released Mg2+ and silicate ions stimulated cell adhesion and proliferation. These results indicated that the fibermats developed in this work could be used for bone tissue regeneration scaffolds that enable the recovery of bone quality and quantity.

Cotton-Wool-Like Resorbable Bone Void Fillers Containing β-TCP and Calcium Carbonate Particles

Cotton-wool-like bioresorbable bone void fillers consisting of β-tricalcium phosphate (β-TCP), siloxane-containing vaterite (SiV) and poly (L-lactic acid) (PLLA) was prepared by an electrospinning method. The fibers, which were 50 ~ 150 μm-width with 10 ~ 30 μm-thickness, were entwined. The resulting cotton-wool-like material showed mechanical flexibility and excellent shapability; it showed easy, excellent mechanical-fixation in defects. The in vivo performance of this material was examined in the distal femur in New Zealand white rabbits. It was evaluated using micro CT and histologic analyses at time points of 6 and 12 weeks. These analyses of the defect sites verified normal healing response and new bone formation. The in vivo testing with rabbits showed good biocompatibility and excellent osteogenic ability.

Interphase coordination design in carbamate-siloxane/vaterite composite microparticles towards tuning ion-releasing properties

Siloxane-containing vaterite (SiV) microparticles were prepared with controlling the degree of aminopropyl-functionalization in the siloxane; they are aiming for applications as bone regenerative devices. The aim of this work was to evaluate the structure at siloxane/vaterite interphase and to control the solubility of particles by the structural tuning of siloxane. The particles were spherical with average diameters of 1.1–1.4μm. Differential infrared spectrometry revealed the transformation of aminopropyl terminals in the siloxane into carbamate (NH-COO−) groups. Moreover, the vaterite crystallites in the particles were slightly oriented towards the (001) plane. These results describe the interphase structure, with the carbamate groups coordinating on the Ca2+ ion face in the (001) plane of neighbouring vaterite. Upon soaking in buffer solution, the particles exhibited a rapid initial release of Ca2+ ions within 30min and of soluble silica within 2h. The vaterite in this particle survived for more than 6h. The chemical stability of the siloxane was enhanced by incorporating tetraethoxysilane-derived siloxane with fractions of 24mol% or 50mol%. This enhancement controlled the initial release of not only soluble silica but also Ca2+ ions.

Development of Magnesium and Siloxane-Containing Vaterite and Its Composite Materials for Bone Regeneration.

Development of novel biomaterials with Mg2+, Ca2+, and silicate ions releasability for bone regeneration is now in progress. Several inorganic ions have been reported to stimulate bone-forming cells. We featured Ca2+, silicate, and especially, Mg2+ ions as growth factors for osteoblasts. Various biomaterials, such as ceramic powders and organic–inorganic composites, that release the ions, have been developed and investigated for their cytocompatibilities in our previous work. Through the investigation, providing the three ions was found to be effective to activate osteogenic cells. Magnesium and siloxane-­containing vaterite was prepared by a carbonation process as an inorganic particle that can has the ability to simultaneously release Ca2+, silicate, and Mg2+ ions to biodegradable polymers. Poly (l-lactic acid) (PLLA)- and bioactive PLLA-based composites containing vaterite coatings were discussed regarding their degradability and cytocompatibility using a metallic Mg substrate as Mg2+ ion source. PLLA/SiV composite film, which has a releasability of silicate ions besides Ca2+ ion, was coated on a pure Mg substrate to be compared with the PLLA/V coating. The degradability and releasability of inorganic ions were morphologically and quantitatively monitored in a cell culture medium. The bonding strength between the coatings and Mg substrates was one of the key factors to control Mg2+ ion release from the substrates. The cell culture tests were conducted using mouse osteoblast-like cells (MC3T3-E1 cells); cellular morphology, proliferation, and differentiation on the materials were evaluated. The PLLA/V and PLLA/SiV coatings on Mg substrates were found to enhance the proliferation, especially the PLLA/SiV coating possessed a higher ability to induce the osteogenic differentiation of the cells.

Preparation of siloxane-containing vaterite doped with magnesium

Preparation of siloxane-containing vaterite doped with magnesium

Enhancement of crystalline plane orientation in silsesquioxane-containing vaterite particles towards tuning of calcium ion release.

Siloxane-containing vaterite (SiV) particles with spherical- to discoidal-morphologies were selectively prepared by a CO2 gas carbonation process in a methanol-acetone mixed solvent; they are intended for application as osteogenic devices in bone tissue engineering. Moreover, the c/ab-face ratio of vaterite was successfully tuned through the selection of methanol-acetone volume fractions. The solvent increased the supersaturation of CO3 2- ions and accelerated the crystal growth along the ab-axis in the presence of silsesquioxane. The particles released soluble silica species and calcium ions upon soaking in physiological pH buffer solution, which are expected to genetically stimulate osteoblasts to enhance bone reconstruction. An initial calcium ion release from the particles significantly decreased from 3.1 to 1.6 mmol L-1 as the c/ab-face ratio increased, while the composition of the particle and release profiles of soluble silica remained consistent. This demonstrated the possibility of tuning the calcium ion release from SiV particles by controlling the degree of crystalline plane orientation.

Cytocompatibility of Siloxane-Containing Vaterite/Poly(l-lactic acid) Composite Coatings on Metallic Magnesium.

Poly(l-lactic acid)-based films which include 60 wt % of vaterite (V) or siloxane-containing vaterite (SiV) were coated on a pure magnesium substrate, denoted by PLLA/V or PLLA/SiV, respectively, to suppress early corrosion and improve its cytocompatibility. Both coating films adhered to the Mg substrate with 2.3–2.8 MPa of tensile bonding strength. Soaking test for 7 days in α-modified minimum essential medium revealed that the morphological instability of the PLLA/V film caused a higher amount of Mg2+ ion to be released from the coating sample. On the other hand, in the case of the coating with the PLLA/SiV film, no morphological change even after the soaking test was observed, owing to the suppression of the degradation rate. In cell culture tests, the proliferation of mouse osteoblast-like cell (MC3T3-E1) was significantly enhanced by both coatings, in comparison with the uncoated magnesium substrate. The cell morphology revealed that a few less-spread cells were observed on the PLLA/V film, while more elongated cells were done on the PLLA/SiV film. The cells on the PLLA/SiV film exhibited an extremely higher alkaline phosphatase activity after 21 days of incubation than that on the PLLA/V one. The PLLA/SiV film suppressed the early corrosion and enhanced cytocompatibility on metallic magnesium.

Preparation of electrospun fiber mats using siloxane‐containing vaterite and biodegradable polymer hybrids for bone regeneration

An electrospun fiber mat using a new composite consisting of siloxane-containing vaterite (SiV) and poly(lactic-co-glycolic acid) (PLGA) (denoted by SiPLGVH) was prepared with the aim of applying it as a membrane for use in a guided bone regeneration (GBR) system. Another electrospun fiber mat using a previously described composite consisting of SiV and poly(L-lactic acid) (denoted by SiPVH) was also prepared as a comparative sample. SiPLG VH fiber mats showed superior results in terms of mechanical tensile properties and cellular behavior. Their elongation before failure was about eight times higher than that of SiPVH. The numbers of osteoblast-like cells that proliferated on the SiPLGVH fiber mats, regardless of the hydroxyapatite coating, were comparable to that of SiPVH. The cells spread more, two dimensionally, on the SiPLGVH fiber mats, since the pores between fibers were narrowed down because of swelling of the PLGA matrix during cell culture. This two-dimensional cellular proliferation quality on the SiPLGVH fiber mats is expected to be suitable for materials used in GBR, leading to control of infiltration of the soft tissue and great tissue integration with the surrounding tissue.

Aluminum Silicate Nanotube Modification of Cotton-Like Siloxane-poly(L-lactic acid)-vaterite Composites

In our earlier work, a cotton-like biodegradable composite, consisting of poly(L-lactic acid) with siloxane-containing vaterite, has been prepared by electrospinning. In the present work, the fibers skeleton of the cotton-like composites was modified successfully with imogolite, which is hydrophilic and biocompatible, via a dip process using ethanol diluted solution to improve the cellular initial attachment. Almost no change in the fiber morphology after the surface modification was observed. The surface-modified composite showed the similar calcium and silicate ions releasabilities, for activating the osteoblasts, as an unmodified one. Cell culture tests showed that the initial adhesion of murine osteoblast-like cells on the surface of the fibers was enhanced by surface modification.

Preparation of siloxane-containing vaterite particles with red-blood-cell-like morphologies and incorporation of calcium-salt polylactide for bone regenerative medicine

Preparation of siloxane-containing vaterite particles with red-blood-cell-like morphologies and incorporation of calcium-salt polylactide for bone regenerative medicine

Preparation of Fibrous Scaffolds Containing Calcium and Silicon Species

Materials for bone defect filling should have 3D macroporous structure and be flexible to be packed into complex defects with limited entrance space. Tissue engineering scaffolds should also mimic the structure and morphology of the host tissue. Electrospinning is a versatile technique to produce materials with micro/nanofibrous structure, large surface area and high porosity. Electrospun materials are very promising for tissue engineering due to the possibility of mimicking the fibrous structure of natural extra cellular matrix (ECM). Siloxane-containing vaterite (SiV)/poly (L-lactic acid) (PLLA) hybrids (SiPVH) with controlled silicate and calcium ions releasing ability has been produced in our group. They have also demonstrated good cell infiltration into the electrospun hybrid materials that had fiber diameters greater than 10 μm. However, these electrospun hybrid materials were planar (2D) and are not suitable for large defect regeneration. In this work, the development of a fabrication technique for the production of 3D cotton wool-like structures with fiber diameter in the range of 10 μm was performed. SiPVH cotton wool-like structure containing 0, 30 and 60 wt % SiV were prepared by blowing air in the direction perpendicular to fiber spinning. Si-vaterite particles and small pores were found on the surface of the fibers. The fiber diameter of the samples were found to be in the range of 10 ~ 20 μm. Stretch tests showed more than 50 % extension for the SiPVH cotton wool-like material containing 30 wt % SiV (SiPVH30). This extension was similar to that observed for the PLLA cotton wool-like material. The results suggest that the SiPVH30 cotton wool-like material are good candidates for bone tissue engineering scaffolds.

Silicate and Calcium Ions Releasing Biomaterials for Bone Reconstruction

Siloxane-containing vaterite (SiV) / poly (lactic acid) hybrid (SiPVH) beads with the releasability of silicate and calcium ions were prepared with an electrospraying method. According to the increase in the silicon content of the SiV, the amount of silicate ion released from the resulting beads also increased. When the beads were soaked in a cell culture medium, proteins derived from fetal bovine serum were adsorbed on their surfaces. Cell adhesion tests were also performed on the beads with using mouse osteoblast-like cell line (MC3T3-E1) in vitro. After 5 days of culturing, the cells adhered and spread well to cover the surface of the beads. In the localized area, agglomerated cells were observed to combine with cauliflower-shaped calcium phosphate deposits.

Modification and mechanical properties of electrospun blended fibermat of PLGA and siloxane-containing vaterite/PLLA hybrids for bone repair

Multi-syringe electrospinning has been successfully employed to produce a blended fibermat composed of poly(lactic-glycolic acid) (PLGA) fibers and a composite fiber for bone repair. The composite fiber, siloxane-containing vaterite (SiV)/poly(L-lactic acid) (PLLA), donated as SiPVH has the ability to release soluble silica species and calcium ions at a controlled rate. The SiPVH fibermats have demonstrated excellent bone regeneration ability in vivo at the front midline of the calvaria of rabbits. However, they are brittle and have low tensile strength resulting from the large particulate SiV (60 wt%) content. In this study, co-electrospinning of PLGA with SiPVH was performed in the hope of achieving a blended fibermat with improved mechanical properties. The co-electrospun fibermats showed good homogeneous blending of the PLGA and SiPVH composite fibers that had excellent flexibility. The blended PLGA-SiPVH fibermats had signifi- cantly improved mechanical properties compared to the SiPVH fibermats, where more than 20 times higher elongation to failure was achieved on comparison to the SiPVH fibermat. As well as strength, high porosity and large pore size are vital for the migration of cells into the centre of the graft. This was accomplished by heating the PLGA-SiPVH fibermats at 110°C for a fixed time, which induced the softening and flow of PLGA towards the more stable SiPVH fibers. Heating had successfully produced PLGA-SIPVH fibermats with large open pores and inter-fused SiPVH fibers, which also had better tensile mechanical properties than the SiPVH fibermat.

Preparation of siloxane-containing vaterite/poly (L-lactic acid) hybrid microbeads with silicate and calcium ions-releasing ability

Siloxane-containing vaterite (SiV)/poly (L-lactic acid) (PLLA) hybrids have the releasing-ability of silicate and calcium ions for gene-activation. In the present paper a new types of beads were prepared using the hybrids via an electrospraying method. The diameters of the beads were controlled in the range of ∼65 to ∼180 µm by increasing the feeding rate from 0.1 to 0.9 ml/min. Depressed areas could be observed on the surface of the beads. The SiV particles with concentration of 10 and 20 wt % in the beads were completely enclosed by the PLLA matrix. These beads showed the controlled release of silicate and calcium ions in Tris buffer solution.

Preparation of siloxane-containing vaterite/poly (lactic acid) hybrid fibermats with improved ductility for bone regeneration

Siloxane-containing vaterite (SiV)/poly (L-lactic acid) (PLLA) hybrid (SiPVH) fibermats have superior potential for bone regeneration applications. Present work aims to optimise its performance as bone filler materials by improving its mechanical properties and maintaining its bioactivity. The SiPVH fibermats were prepared with melt-blending and electrospinning protocols and modified by increasing PLLA content from 40 to 70 wt %. The tensile strength of the modified fibermat was 10 times higher than that of the original one. The elongation before failure of the modified fibermat was twice as large as that of the original one. The mechanism of their enhancement was investigated by observing failure points in the fibermats after the tensile tests: necking of fibers, which occurred in the modified fibermats, was believed to contribute to the enhanced mechanical properties. The modified fibermat showed the relatively constant release of ionic silicon-species in Tris-buffer solution and could be coated with hydroxyapatite by soaking in simulated body fluid.