Abstract: With the outstanding biocompatibility of hydroxyapatite (HA) and biodegradation of
poly(D,L)lactide(PDLLA), and the expected good bio-mechanical compatibility, nano-HA / PDLLA (n-HA/PDLLA)composite has been paid great interests in hard tissue repair. One of the key factors affecting the potential of the composite is the degradation of the composite. That is what the mechanism of degradation in the composite is and if the degradation of the materials would induce the crack of the composite or a porous structure facile for tissue ingrowth would be formed. In this study, an n-HA/ PDLLA composite containing about 40% n-HA (wt%) was prepared and the degradation of the composite in bony tissue of rabbits and tissue response were studied by implanting composite rods and control HA rods into the femora of 16 New Zealand rabbits. After definite intervals, the histological analysis was completed by light microscopy and the degradation behavior was observed by scanning electron microscopy. The results suggested that a nano-HA/PDLLA composite was obtained and the materials showed good biocompatibility and
osteoconductivity. The substantial degradation of the composite occurred at 8 weeks in vivo. After a longer period of implantation, the further degradation of the composite led to the formation of interconnected microporous and macroporous structure in the materials that might facilitate the tissue ingrowth in the composite.
Abstract: The copolymer of poly (1, 4-phenylene sulfide-2, 4-phenylene sulfide acid)[p-PPS-m-PPSA] and its nano HA composite [NHA/ p-PPS-m-PPSA] were recently developed as a new kind of inorganic-organic system for biomaterials. This kind of copolymer and its nano-HA composites may have a potential use in loaded bone substitutes, fixation or tissue engineering. In the present research the in vitro behavior of this kind of composites has been investigated in the SBF, and the surface changes were measured by XRD, XPS. SEM and EDS. The results showed that the copolymer and the NHA/ p-PPS-m-PPSA composites were very stable in SBF. The Ca, P content increased to 1.64wt% and 0.77wt% on the surface of p-PPS-m-PPSA, and the Ca/P was 1.63, near to that of the stoichiometric HA, 1.67
meanwhile the Ca, P content increased on NHA/ p-PPS-m-PPSA surface increased to 8.50wt% and 3.42wt% and the Ca/P ratio of surface of the NHA/ p-PPS-m-PPSA composites decreased slowly from 2.01to 1.83 during the incubation in SBF. Analysis demonstrated that the precipitate on copolymer of p-PPS-m-PPSA was HA and the precipitate on the NHA/ p-PPS-m-PPSA surface was HA, TCP and
carbonated-apatite. All results showed that both the copolymer of p-PPS-m-PPSA and NHA/ p-PPS-m-PPSA composite were stable and bioactive, and might have a promising potential use in implantation and tissue engineering.
Abstract: In this study, alkali-heat treatment in NaOH solution and heat treatment, which could
form amorphous sodium titanate on nanophase titania ceramics surface by conditioning the process, was employed to modify the structure and bioactivity of biomedical titania ceramics. After the nanophase titania ceramics was subjected to alkali-heat treatment, thin film X-ray diffraction and scanning electron microscopy results showed the titania ceramics surfaces were covered by porous sodium titanate. In fast calacification solution (FCS), the alkali-heat treated titania ceramics could induce bonelike apatite formation on its surface. Our results showed that induction of apatite-forming ability on titania ceramics could be attained by alkali-heat treatment. So it was an effective way to prepare bioactive titania ceramics by combining sintering and alkali-heat treatment.
Abstract: The HAp coatings with various surface morphologies were electrochemically deposited on titanium to improve its bio-properties. We compared the bio-properties for the different surface morphology coatings on titanium through a detailed surface characterization and upon in vitro cellular response of osteoblast-like cells MG63. The results of in vitro cellular response indicated that the uniform porous morphology of HAp layers on titanium exhibited higher bioactivity than the needle-like ones.
Abstract: Glutaraldehyde was increasingly used to improve the stability of the collagen-based
biomaterials as cross-linking. To investigate in vitro cytotoxicity of Hydroxyapatite/Collagen (HA/COL) composite with glutaraldehyde (GA) as cross-link reagent, which was abbreviated as cHA/COL, the mouse fibroblasts L929 cell was selected. The method of MTT colorimetric assay was adopted to evaluate the availability of cells. After cultured for 24h、 48h, the attachment and morphology of L929 cell on the surface of this material were observed by scanning electron microscopy (SEM) and fluorescent microscopy. MTT analysis
indicated L929 cells cultured on cHA/COL had a perfect growth capacity. Cells proliferated well and cell colonization was observed on the materials by scanning electron microscopy and fluorescent microscopy. It demonstrated that cHA/COL composite exhibited good cytocompatibility and might be suitable as bone substitutes. The result provided the evidence for further animal experiment in vivo.
Abstract: Six silane-modified hydroxyapatite (HA) / poly(lactic acid) (PLA) composites at 20% volume HA are prepared through absorption in liquid phase, volatilization, milling, and hot-press molding. Bending testing results indicate that their bending strengths are higher than that of control HA composite (unmodified HA composite) and the maximum strength enhances 27.8%. Calcium precipitation and calcium release experiments are designed to examine the bioactivity of the
modified HA. The results show that the presence of the modification coating does not really impair the bioactivity and mineralization tendency of HA particles. Relationship of swelling property of the composites as function of time is investigated. Swelling equilibriums of silane-modified HA / PLA composites are reached after 48 h or 72 h, but the equilibrium of the unmodified HA / PLA composite is reached within 24 h. The swelling experiment also suggests that the desired swelling property of the composites could be achieved by changing modification molecules of HA according to necessity. Finally, SEM micrographs show that there is an improved interfacial binding between the modified HA and PLA matrix.
Abstract: Effects of bio-degradation on the mechanical properties of polylactic acid
(PLA)/hydroxyapatite (HA) were evaluated using a newly designed three-point bending fixture in SBF chamber. The composite was found to be ductile and insensitive to cracks, which is totally different from its brittle behavior observed in conventional tests, in which the degraded samples are tested in air at room temperature. Initial bending modulus and strength of PLA/HA composite were 1.2 GPa and 43 MPa, respectively, which were lower than those tested under room conditions. After two weeks of immersion in vitro, both bending modulus and strength decreased by 40% and 57%, respectively. Their degradation rates were both higher than those in reports of previous researches. This work indicates the importance of evaluating mechanical behavior in simulated body environment.
Abstract: b-glucan, an immunomodulator, can selectively enhance the immunobiological
activities of neutrophils and macrophages without stimulating proinflammatory cytokine production. Biologic response modifiers, like beta-glucan, will modulate immunity, modify neoplastic disease and increase resistance to microbial challenge. Therefore, beta-glucan polymers can be applied in bone induction and regeneration model and have a possibility of association with bone morphogenetic protein (BMP) because of tissue-regenerative and antimicrobial effects of those polymers. In this report, we studied an E. coli expression system for BMP-7 production and the biological activities of b-glucan associated with BMP-7. The proliferation of MC3T3-E1 osteoblastic cells was enhanced by treatment with Aureobasidium b-glucan, while neither mushroom b-glucan nor barley b-glucan increased the cell proliferation. Mushroom b-glucan alone or associated with BMP-7 increased alkaline phosphatase (ALP) activity of MC3T3-E1 cells, one of the osteoblast phenotype markers, but the other b-glucans did not affect ALP activity
of the cells. In mineralization assay, a highly significant increase in nodular staining was observed in cultures treated with both mushroom and Aureobasidium b-glucans in the presence of BMP-7 compared with nontreated controls, while barley b-glucan showed a significant decrease in nodule number compared with cultures treated only with BMP-7.