Biomedical materials最新文献

Here, we demonstrate the in vivo efficacy of glucose microparticles (GMPs) to serve as porogens within calcium phosphate cements (CPCs) to obtain a fast-degrading bone substitute material. Composites were fabricated incorporating 20 wt% GMPs at two different GMP size ranges (100-150 μm (GMP-S) and 150-300 μm (GMP-L)), while CPC containing 20 wt% poly(lactic-co-glycolic acid) microparticles (PLGA) and plain CPC served as controls. After 2 and 8 weeks implantation in a rat femoral condyle defect model, specimens were retrieved and analyzed for material degradation and bone formation. Histologically, no adverse tissue response to any of the CPC-formulations was observed. All CPC-porogen formulations showed faster degradation compared to plain CPC control, but only GMP-containing formulations showed higher amounts of new bone formation compared to plain CPC controls. After 8 weeks, only CPC-porogen formulations with GMP-S or PLGA porogens showed higher degradation compared to plain CPC controls. Overall, the inclusion of GMPs into CPCs resulted in a macroporous structure that initially accelerated the generation of new bone. These findings highlight the efficacy of a novel approach that leverages simple porogen properties to generate porous CPCs with distinct degradation and bone regeneration profiles.

This study addresses the fabrication of an extracellular matrix material of the acellular sheep periosteum and the systematic evaluation of its biocompatibility to explore its potential application in guided bone regeneration. Sheep periosteum was harvested and decellularized by a combined decellularization protocol. The effectiveness of cell removal was proved and residual α-Gal antigen was also quantitatively detected. Then, mouse MC3T3-E1 cells were seeded onto the acellular periosteum. A scanning electron microscope (SEM) was used to record the whole process of cell adhesion. The CCK-8 assay suggested that the acellular periosteum not only had zero toxic effect on pre-osteoblasts, but played a positive role in cell proliferation. We also tested whether the acellular periosteum possesses favorable osteogenesis induction activity using an alkaline phosphatase (ALP) assay and a quantitative real-time PCR (Col I, Runx2, OCN) assay. An in vivo study of a subcutaneous implantation test using Sprague Dawley (SD) rats was performed to detect the changes in IL-2, IFN-γ and IL-4 in serum and elucidate the host's local response to acellular periosteum through hematoxylin and eosin (HE) and immunohistochemical staining. The results show that acellular sheep periosteum did not elicit a severe immunogenic response via the Th1 pathway, unlike fresh sheep periosteum. In conclusion, acellular sheep periosteum possesses favorable biocompatibility to be employed for guided bone regeneration.

Severe spinal cord injury (SCI) results in permanent functional deficits, which despite pre-clinical advances, remain untreatable. Combinational approaches, including the implantation of bioengineered scaffolds are likely to promote significant tissue repair. However, this critically depends on the extent to which host tissue can integrate with the implant. In the present paper, blood vessel formation and maturation were studied within and around implanted micro-structured type-I collagen scaffolds at 10 weeks post implantation in adult rat mid-cervical spinal cord lateral funiculotomy injuries. Morphometric analysis revealed that blood vessel density within the scaffold was similar to that of the lateral white matter tracts that the implant replaced. However, immunohistochemistry for zonula occludens-1 (ZO-1) and endothelial barrier antigen revealed that scaffold microvessels remained largely immature, suggesting poor blood-spinal cord barrier (BSB) reformation. Furthermore, a band of intense ZO-1-immunoreactive fibroblast-like cells isolated the implant. Spinal cord vessels outside the ZO-1-band demonstrated BSB-formation, while vessels within the scaffold generally did not. The formation of a double-layered fibrotic and astroglial scar around the collagen scaffold might explain the relatively poor implant-host integration and suggests a mechanism for failed microvessel maturation. Targeted strategies that improve implant-host integration for such biomaterials will be vital for future tissue engineering and regenerative medicine approaches for traumatic SCI.

An electrospinning technique was used to produce three-dimensional (3D) bioactive glass fibrous scaffolds, in the SiO₂-CaO sol-gel system, for wound healing applications. Previously, it was thought that 3D cotton wool-like structures could only be produced from sol-gel when the sol contained calcium nitrate, implying that the Ca²⁺ and its electronic charge had a significant effect on the structure produced. Here, fibres with a 3D appearance were also electrospun from compositions containing only silica. A polymer binding agent was added to inorganic sol-gel solutions, enabling electrospinning prior to bioactive glass network formation and the polymer was removed by calcination. While the addition of Ca²⁺ contributes to the 3D morphology, here we show that other factors, such as relative humidity, play an important role in producing the 3D cotton-wool-like macrostructure of the fibres. A human dermal fibroblast cell line (CD-18CO) was exposed to dissolution products of the samples. Cell proliferation and metabolic activity tests were carried out and a VEGF ELISA showed a significant increase in VEGF production in cells exposed to the bioactive glass samples compared to control in DMEM. A novel SiO₂-CaO nanofibrous scaffold was created that showed tailorable physical and dissolution properties, the control and composition of these release products are important for directing desirable wound healing interactions.

Because the collagen membrane lacks osteoinductivity, it must be modified with bioactive components to trigger rapid bone regeneration. In this study, we aimed to evaluate the bone regeneration effects of a collagen membrane chemically conjugated with stromal cell-derived factor-1 alpha (SDF-1α) in rat models. To this end, different collagen membranes from four groups including a control group with a Bio-Oss bone substitute + collagen membrane; physical adsorption group with Bio-Oss + SDF-1α physically adsorbed on the collagen membrane; chemical cross-linking group with Bio-Oss + SDF-1α chemically cross-linked to the collagen membrane; and cell-seeding group with Bio-Oss + bone marrow mesenchymal stem cells (BMSCs) seeded onto the collagen membrane were placed in critical-sized defect models using a guided bone regeneration technique. At 4 and 8 weeks, the specimens were analyzed by scanning electron microscopy, energy-dispersive x-ray spectroscopy, micro-computed tomography, and histomorphology analyzes. Furthermore, ectopic osteogenesis was examined by histological analysis with Von Kossa staining, with the samples counterstained by hematoxylin and eosin and immunohistochemical staining. The results showed that in the chemical cross-linking group and cell-seeding group, the bone volume fraction, bone surface area fraction, and trabecular number were significantly increased and showed more new bone formation compared to the control and physical adsorption groups. Von Kossa-stained samples counterstained with hematoxylin and eosin and subjected to immunohistochemical staining of 4-week implanted membranes revealed that the chemical cross-linking group had the largest number of microvessels. The collagen membrane chemically conjugated with SDF-1α to significantly promote new bone and microvessel formation compared to SDF-1α physical adsorption and showed similar effects on new bone formation as a BMSC seeding method. This study provided a cell-free approach for shortening the bone healing time and improving the success rate of guided bone regeneration.

A tissue-engineered heart valve can be an alternative to current mechanical or bioprosthetic valves that face limitations, especially in pediatric patients. However, it remains challenging to produce a functional tissue-engineered heart valve with three leaflets mimicking the trilayered, oriented structure of a native valve leaflet. In our previous study, a flat, trilayered nanofibrous substrate mimicking the orientations of three layers in a native leaflet-circumferential, random and radial orientations in fibrosa, spongiosa and ventricularis layers, respectively, was developed through electrospinning. In this study, we sought to develop a trilayered tissue structure mimicking the orientations of a native valve leaflet through in vivo tissue engineering, a practical regenerative medicine technology that can be used to develop an autologous heart valve. Thus, the nanofibrous substrate was placed inside the closed trileaflet-shaped cavity of a mold and implanted subcutaneously in a rat model for in vivo tissue engineering. After two months, the explanted tissue construct had a trilayered structure mimicking the orientations of a native valve leaflet. The infiltrated cells and their deposited collagen fibrils were oriented along the nanofibers in each layer of the substrate. Besides collagen, presence of glycosaminoglycans and elastin in the construct was observed.

The interaction of proteins with implantable metallic surfaces has a great influence on the bioactivity and biodegradation of orthopaedic implants. Initial osseointegration is known to be critical for the long term success of orthopaedic implants. The surface properties of the implant and electrochemical milieu of the surrounding solution such as electrostatic, hydrophobic, and hydrogen bonding interactions significantly modulate protein adsorption by implants. Magnesium (Mg) is considered to improve the adhesion of osteoblasts via ligand binding of the integrin receptors. Mg-based composites, reinforced with hydroxyapatite (HA), are potential candidates for temporary orthopaedic implants. However, their clinical translation requires enhanced degradation resistance in physiological environment so that it is in sync with the healing rate of the bone. The present study deals with the protein adsorption characteristics and degradation behaviour of Mg-HA-based biodegradable implants. Quantitative analysis of apatite inducing ability of composites was evaluated in terms of mass gain in simulated body fluid (SBF) as well as in foetal bovine serum (FBS), by an in vitro immersion study. Incorporation of 5 and 15 wt% HA to Mg-3Zn improved apatite formation up to 35% and 66%, respectively, after 14 days of immersion in SBF. Compared to FBS, SBF is found to be significantly more effective in precipitating apatite on a Mg-HA surface. However, FBS offered more corrosion resistance to Mg-HA than SBF did, as evident from the significant differences in the protein adhesion capabilities of the composite surface when incubated separately in these two mediums. The addition of 15 wt% HA enhanced the protein adsorption capability by ∼35%. These studies highlight the possibility of modulating the degradation and bioactivity of Mg-based composite by tailoring the composition of HA. These findings, in turn, warrant the suitability of Mg-HA composite in orthopaedic application.

The goal of this research was to promote the bioactivity and osteogenic characteristics of polyvinylidene fluoride(PVDF) fibrous membrane, while preserving its piezoelectric property for bone regeneration. In this regard, core-shell fibrous membrane of PVDF-Ba_0.9Ca_0.1TiO₃/polyvinyl alcohol(PVA) was developed via emulsion electrospinning approach. While PVA was in the outer layer of fibers with thickness of 53 ± 18 nm, the Ba_0.9Ca_0.1TiO₃ nanoparticles was uniformly dispersed in the PVDF core. The formation of PVA shell resulted in significant improvement of its hydrophilicity (3 times) and degradation rate, while piezoelectricity did noticeably modulate. In addition, incorporation of Ba_0.9Ca_0.1TiO₃ nanopowder remarkably improved bioactivity, protein adsorption and mechanical properties of PVDF/PVA fibrous membranes. Finally, the osteogenic differentiation of mesenchymal stem cells on the nanocomposite fibrous membranes, in the absence of osteogenic supplements, was also observed. Overall, the results confirmed the promising potential of PVDF-Ba_0.9Ca_0.1TiO₃/PVA fibrous membrane containing 1-2 wt% nanopowder for bone regeneration.

Using three-dimensional (3D) bone engineering to fabricate bone segments is a better choice for repairing bone defects than using autologous bone. However, biomaterials for bone engineering are burdened with some clinical safety concerns. In this study, we layered commonly found clinical materials, hemostatic gelatin sponges, in a novel manner to create a 3D scaffold for bone engineering purposes. We further examined the comparable benefits of our design with both closed- and open-bottom holders. Cells in stacked layer disc systems were examined after a week of growth and differentiation. Osteoblasts in the outer layers of both closed- and open-bottom holder systems displayed gradually increased alkaline phosphatase (ALP) activity but decreased osteopontin (OPN) expression. Further, cell proliferation assays and LIVE/DEAD staining revealed decreased viable cell counts in the top layer with increased incubation time. However, while layered disc systems with closed-bottom holders underwent differentiation, they kept more differentiated cells alive within the gelatin sponge disc scaffold after 28 d of culturing. Whether cells were inoculated into the top, middle, or bottom portions of the layered disc stack, osteoblasts showed a preference for migrating to the top layer, in keeping with the oxygen and nutrients gradients. Regarding practical application, this study offers valuable information to promote the use of hemostatic gelatin sponges for bone engineering.