磷酸根、钙离子在钛金属表面仿生矿化影响研究

目的研究不同预处理时间下,钙离子(Ca^2+)、磷酸根离子(PO4^3-)对钛金属表面仿生矿化性能的影响,为钛金属改性做铺垫。方法采用浓度为0.5 mol/L Na2HPO4和饱和Ca(OH)2的澄清溶液进行预磷化和预钙化处理,以预磷化和预钙化时间为参数,采用正交实验方法,利用能谱仪(EDS)、X射线衍射(XRD)分析仪、扫描电子显微镜(SEM)和傅里叶变换红外光谱(FT-IR)分析仪等检测手段对样品进行表征。比较各种不同预处理时间下样品表面矿化形貌、成分及晶体取向的差别,并分析各离子对矿化影响的各自作用和协同增效作用。结果不同预磷化、预钙化时间,对钛金属表面矿化仿生影响明显。预磷化时间越长,钙磷元素比增加;同时随着预磷化的时间延长,在同等预钙化时间下,钛片样品的表面C-O数量减少。结论Ca^2+和PO4^3-具有协同增效的作用,预磷化的样品再经预钙化处理,既可以加速钙磷层的沉积速度,又可以有效地调控钙磷晶体的生长取向。     

Determination of rate constants of initiation and propagation in the cationic polymerization of α-methylstyrene with CF3SO3H and H2SO4

The polymerization of α-methylstyrene with CF₃SO₃H and H₂SO₄ as initiators was studied at 30°C in dichloroethane by the stopped-flow/rapid-scan spectroscopic technique. The propagating cation shows λ_max at 336–340 nm. The initiation process and the early stage of propagation were analyzed kinetically on the basis of the cation formation and monomer consumption by taking into account the equilibrium monomer concentration. The rate of initiation with CF₃SO₃H was found to be proportional to the concentrations of CF₃SO₃H and monomer, but the initiation with H₂SO₄ is not proportional to the H₂SO₄ concentration. The rate constant of initiation was estimated to be (2 ± 1)·10³ 1.mol^?1.s^?1 with CF₃SO₃H, and similar values were found with H₂SO₄. The rate constant of propagation is 3.10⁴ 1.mol^?1.s^?1 with CF₃SO₃H as initiator and 10⁶ ? 10⁷ 1.mol^?1.s^?1 with H₂SO₄ as initiator. These k_p values are close to that obtained previously in the radiation polymerization. Finally, λ_max values of the propagating cation, obtained by the stopped-flow technique, were collected.     

Precipitation of carbonated apatite in the cement system alpha-Ca(3)(PO(4))(2)-Ca(H(2)PO(4))(2)-CaCO(3).

Powder mixtures of alpha-Ca(3)(PO(4))(2), Ca(H(2)PO(4))(2), and CaCO(3) were investigated to assess their potential for the precipitation of a carbonated apatite suitable for cement applications from a supersaturated solution. Of particular interest was the requirement of carbon dioxide release during the setting reaction to obtain Ca(9-x)(HPO(4))(1-1.5x) (PO(4))(5-2.5x)(CO(3))(3.5x)(OH)(1 + 1.5x) with a fixed carbonate content. Results indicated that a compromise is necessary with respect to the maximum permissible level of CaCO(3) addition to the powder mixture as against appropriate setting and hardening properties. Cementlike materials with good setting and hardening properties were obtained when alpha-Ca(3)(PO(4))(2) was the main reactant using Ca(H(2)PO(4))(2) and CaCO(3) as additives in relative proportions of <10 wt % corresponding, approximately, to the stability field area (x,lambda) contained within the lines lambda = -1.5x, x = 0.3, and lambda = -1. Desirable workability and setting properties were lost as the parameters x and -lambda increased. Finally, it was also found to be virtually impossible to obtain a predetermined chemical composition for the setting apatite precipitate, since to increase the amount of carbon dioxide released from the initial powder mixture during setting, the solution pH would need to be decreased, and in doing so the nature of the precipitate could be altered to fulfil the thermodynamic conditions of the solubility diagrams of calcium phosphates.     

Ethylene/propene copolymerization in the presence of the homogeneous catalyst system Ti(Oi-C3H7)4/Al(C2H5)2F

The behaviour of the homogeneous catalyst system Ti(Oi-C₃H₇)₄/Al(C₂H₅)₂F in ethylene/propene copolymerization was studied. The copolymer structure is discussed in view of the stereoregulation mechanism previously proposed for vanadium-based homogeneous catalyst systems.     

Induction of suppression following autologous mixed lymphocyte reaction; role of a novel 2H4 antigen

In this study, we have investigated the cellular and molecular basis for immunoregulatory function of T4+ cells after autologous mixed lymphocyte reaction (AMLR) activation. We demonstrated that the T4+ 2H4+ subset but not the T4+2H4- subset can proliferate maximally in response to autologous non-T cells. T4+ cells activated by AMLR exerted suppressor activity on pokeweed mitogen-driven IgG synthesis of autologous peripheral blood lymphocytes. The suppressor activity by AMLR-activated T4+ cells required the presence of fresh T8+ cells in the secondary culture, indicating that AMLR-activated T4+ cells functioned as a suppressor inducer rather than as a suppressor effector population. Following activation of T4+ cells in AMLR, it is the T4+2H4+ subset which induces suppression through the T8 population. Moreover, the treatment of AMLR-activated T4+2H4+ cells with anti-2H4 antibody, but not other antibodies, resulted in the abolishment of suppressor inducer function of such cells, suggesting that the 2H4 molecule itself may be involved in the suppressor inducer function. The 2H4 antigen on such cells was shown to be comprised of 220-kDa and 200-kDa glycoproteins. These results support the notion that the AMLR may play an important role in generating suppressor inducer signals and in down-regulating the immune response following self major histocompatibility complex recognition. More importantly, the present studies indicate that the 2H4 antigen on T4 cells serves not only as a phenotypic marker of suppressor inducer cells, but may have a functionally important role itself inducing suppression.     

Preliminary results on ethylene/propene copolymerization in the presence of Cp2Ti(CH3)2/Al(CH3)3/H2O

Ethylene/propene copolymerizations were carried out in the presence of the catalyst system Cp₂Ti(CH₃)₂/Al(CH₃)₃/H₂O (Cp = cyclopentadienyl group), and the reactivity ratios r₁, r₂ were determined through the Fineman and Ross equation and via ¹³C NMR. A nearly alternating copolymer structure was pointed out. The yields as well as the molecular weights of the copolymers strongly decrease with increasing propene mole fraction in the copolymers.     

Syndiospecific polymerization of styrene with the catalytic system [Ti2(OC2H5)8Cl]2Mg2(μ-Cl)2/methylaluminoxane compared with MgCl2-supported and unsupported Ti(OC2H5)4

As a part of our interest in the performance of [Ti₂(OC₂H₅)₈Cl]₂Mg₂(μ-Cl)₂ as Ziegler-Natta catalyst, the polymerization of styrene with a toluene solution of this compound and methyl-aluminoxane as cocatalyst was performed. It was found that the present catalytic system promotes the syndiospecific polymerization of styrene with high stereoregularity and the results were compared with those obtained with MgCl₂-supported or unsupported Ti(OC₂H₅)₄ catalysts. Determination of the titanium oxidation states and electron spin resonance (ESR) measurements both in the absence and in the presence of styrene were carried out for all the catalytic systems aimed at shedding some light on the nature of the active species.     

Beta-CaSiO3/beta-Ca3(PO4)2 composite materials for hard tissue repair: in vitro studies

In this study, a series of beta-CaSiO(3) (CS)/beta-Ca(3)(PO(4))(2) (TCP) composites with different ratios were prepared to produce new bioactive and biodegradable biomaterials for potential bone repair. The mechanical properties of CS-TCP composites increased steadily with the increase of TCP amounts in composites. Formation of bone-like apatite on a range of CS-TCP composites with CS weight percentage ranging from 0 to 100 has been investigated in simulated body fluid (SBF). The presence of bone-like apatite layer on the composite surface after soaking in SBF was demonstrated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and fourier transform infrared reflection spectroscopy (FTIR). The results showed that the apatite formation ability of the CS-TCP composite was enhanced with increasing CS content in the composites. For composites with more than 50% CS contents, the samples were completely covered by a layer of dense bone-like apatite just after 3 days immersion. Dissolution tests in Tris-HCl buffer solution showed obvious differences with different CS contents in composites. The dissolution rate increased with the increase of CS content, which suggested that the solubility of biphasic composites could be tailored by adjusting the initial CS/TCP ratio. In vitro cell experiments showed that higher content of CS phase in composites promoted cell proliferation and differentiation. When the CS amount in the composite increased to 50%, the proliferation rate and ALP activities of osteoblast-like cells showed significant difference compared with pure TCP (p < 0.05). Results of the study suggested that the CS-TCP composites with more than 50% CS content might be promising bone repair materials.     

Propene polymerization with δ-TiCl3/AlCl(C2H5)2 and δ-TiCl3/Al(C2H5)3 catalyst systems, 1. Effect of external donors

The effect of ethyl benzoate (EB), diisobutyl phthalate (DIBP), dibutyl ether (DBE) and triethoxy(phenyl)silane (EPS) as third components on the propene polymerization with the catalyst systems δ-TiCl₃/AlCl(C₂H₅)₂ and δ-TiCl₃/Al(C₂H₅)₃ was investigated. The influence of external donors on the isotacticity, catalyst activity and average molecular weight (M _v) was tested. If external donors are employed, M _v decreases, the insoluble fraction in boiling isooctane increases and the catalyst activity is strongly influenced by the mole ratio external donor/TiCl₃. The results indicate that all external donors employed have the same qualitative effect on catalytic active centers.     

Bony integration of titanium implants with a novel bioactive calcium titanate (Ca(4) Ti(3) O(10) ) surface treatment in a rabbit model

Nowadays total joint replacement is an indispensable component of modern medicine. The surfaces characteristics of cementless prostheses may be altered to achieve an accelerated and enduring bony integration. Classic surface coatings bear the risk of loosening or flaking from the implant body. This risk is excluded by the chemical conversion of the naturally existing TiO(2) surface layer into calcium titanate. The aim of this experimental animal study was to investigate the bony integration of implants with a new calcium titanate surface (Ca(4) Ti(3) O(10) ) compared with a conventional standard Ti6Al4V surface. Cylindrical implants, made of titanium alloy (Ti6Al4V) were implanted in both lateral femoral condyles of New Zealand white rabbits. In each animal, an implant with and without surface treatment was inserted in a blinded manner. Animals were sacrificed after 4, 12, and 36 weeks, respectively. The axial pull-off forces were determined for 25 animals using a universal testing machine (Zwick Z010, Ulm, Germany). Furthermore, a histological analysis of the bony integration of the implants was performed in 12 specimens. In general, the pull-off forces for untreated and treated implants increased with longer survival times of the rabbits. No significant difference could be shown after 4 weeks between treated and untreated implants. After 12 weeks, the treated implants revealed a statistical significant higher pull-off force. After 36 weeks, the pull-off forces for treated and untreated implants aligned again. Titanium implants treated with calcium titanate, may offer an interesting and promising implant surface modification for endoprosthetic implants. They might lead to an accelerated osseointegration of total hip and knee replacements. ? 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A 100A:2710-2716, 2012.     

Comparative studies of in vitro transformation by ethylene oxide and gamma-radiation of C3H/10T1/2 cells

A dose-dependent transforming ability of the direct-acting alkylatingagent, ethylene oxide (EtO), was demonstrated in C3H/10T1/2mouse embryo fibroblasts. Morphologically transformed colonieswere observed 5–6 weeks after the treatment with EtO.The transforming effectiveness of EtO was compared with thatof gamma-radiation, and the rad-equivalence of EtO was calculatedto be 90 rad/mMh. This value is consistent with earlier estimatesbased on induced mutation in various biological systems andthus indicates the applicability of the C3H/10T1/2 cell systemin the risk estimation of human exposure to genotoxic compounds. ¹To whom correspondence should be addressed     

Bioactive titania-gel layers formed by chemical treatment of Ti substrate with a H2O2/HCl solution.

An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a H2O2/0.1 M HCl solution at 80 degrees C. The thickness of the gel layer increased almost linearly with the period of the treatment. A subsequent heat treatment above 300 degrees C transformed gradually the amorphous gel to the anatase crystal structure and the rutile started to appear after heat treatment at 600 degrees C. Meanwhile, the densification of the gel occurred significantly after heat treatment above 700 degrees C. Similar to the sol-gel derived titania gel coatings. titania gel layers obtained in the present study exhibited in vitro apatite deposition ability after the gel layers exceeded a minimum thickness (0.2 microm) and was subsequently heated in a proper temperature range (400-600 degrees C).     

Identification of novel H3 receptor (H3R) antagonists with cognition enhancing properties in rats

Inflammation Research -     

Polymerization of acetylene with Ti(OC4H9)4/butyllithium as catalyst system and silicone oil as reaction medium

A polymerization reaction catalyzed by Ti(OC₄H₉)₄/butyllithium in a reaction medium of silicone oil yields a homogeneous and highly conductive polyacetylene when doped with iron (III) chloride. The effect of the transition metal halide on polyacetylene was studied by solution doping with FeCl₃/nitromethane as a function of time.