Modeling of immunoglobulin uptake by N,N,N',N'-ethylenediaminetetramethylenephosphonic acid-modified zirconia particles under static and dynamic conditions

A matrix developed from N,N,N',N'-ethylenediaminetetramethylenephosphonic acid-modified zirconia beads (further referred to as r_PEZ); 25-38 microm in diameter and with a pore size of 22+/-3 nm, was utilized for the separation of immunoglobulins (Igs). r_PEZ has been shown to bind to various Igs originating from a wide variety of species. To understand the mechanisms controlling the uptake of Igs by r_PEZ, static protein uptake experiments were carried out. The protein uptake profiles were further modeled with a kinetic rate constant model. Individual studies were undertaken for human immunoglobulin A, G and M (HIgA, HIgG and HIgM). The kinetic rate constant model indicated that HIgG binding to r_PEZ was more favorable than its disassociation. The equilibrium rate constants were found to decrease with increasing concentration. The effect of continuous loading in a packed bed system utilizing r_PEZ matrix was evaluated by carrying out frontal studies, using different feed concentrations and linear velocities. The breakthrough profiles obtained for the uptake of HIgG were modeled with the pore diffusion model. The model was found to best describe the breakthrough profiles obtained at a feed concentration of 2.0 mg of HIgG per milliliter. The NTU for the packed bed was found to be equal to 2.     

Fabrication of chitin-chitosan/nano ZrO(2) composite scaffolds for tissue engineering applications

The urge to repair and regenerate natural tissues can now be satisfactorily fulfilled by various tissue engineering approaches. Chitin and chitosan are the most widely accepted biodegradable and biocompatible materials subsequent to cellulose. The incorporation of nano ZrO₂ onto the chitin-chitosan scaffold is thought to enhance osteogenesis. Hence a nanocomposite scaffold was fabricated by lyophilization technique using chitin-chitosan with nano ZrO₂. The prepared nanocomposite scaffolds were characterized using SEM, FTIR, XRD and TGA. In addition, the swelling, degradation, biomineralization, cell viability and cell attachment of the composite scaffolds were also evaluated. The results demonstrated better swelling and controlled degradation in comparison to the control scaffold. Cell viability studies proved the non toxic nature of the nanocomposite scaffolds. Cells were found to be attached to the pore walls and spread uniformly throughout the scaffolds. All these results suggested that the developed nanocomposite scaffolds possess the prerequisites for tissue engineering scaffolds and could be used for various tissue engineering applications.     

氧化锆基台的制作及其与钛基台抗折强度的比较

目的：制作氧化锆基台并将其与钛基台的抗折强度相比较,从而探讨其临床应用的可行性。方法：选用纳米氧化锆粉,采用冷等静压成型和二次烧结工艺制作0sstem USⅡ系统氧化锆基台;选取氧化锆基台和成品钛基台（OSSTEM公司,韩国）各10枚,分别与0sstem USⅡ种植体装配,然后固定于不锈钢夹具中置于万能试验机,将万能试验机压头与种植体长轴成90°角施加压力,记录基台损坏时的加载力值,比较分析两组试件的强度差异。结果：氧化锆基台和钛基台的平均抗折强度分别为（540.5±84.6）N和（753.9±160.8）N,差别有统计学意义（P〈0.05）。氧化锆基台组10枚基台全部颈部折裂;钛基台组2枚种植体损坏,6枚中央固位螺钉损坏,2枚基台颈部折裂。结论：本研究制作的0sstem USⅡ系统的氧化锆基台的抗折强度虽然低于钛基台,但尚能满足临床应用要求。     

Atom–atom force field for simulation of zirconia bulk,nanosheets and nanotubes

The set of three pair atom–atom potentials for zirconia crystals and nano objects was developed. Besides Buckingham potential and Coulomb interaction, these force fields employ the additional functional forms: Fermi-Dirac, Inverse Gaussian or Morse potential. The developed force fields are capable to reproduce the structural, mechanical and thermodynamic properties of five zirconia phases: monoclinic, tetragonal, cubic, brookite and cotunnite with acceptable accuracy. The proposed force fields give monoclinic phase as a ground state structure and predict the correct energy ordering of the phases. The Raman and IR phonon frequencies, temperature dependencies of the thermodynamic properties of monoclinic and tetragonal zirconia are predicted in good and moderate agreement with the experimentally observed data and results of first-principles calculations. To test the transferability of proposed potentials, the zirconia-based nanosheets and nanotubes were simulated. Results of structure optimisation and calculation of the nanotubes’ strain energies are well compared with the corresponding data of the first-principles calculations.     

Titanium and zirconia particle-induced pro-inflammatory gene expression in cultured macrophages and osteolysis,inflammatory hyperalgesia and edema in vivo

Aims

The biological reaction to wear debris is critical to the osteolysis underlying aseptic loosening of joint prosthetic implants. In an attempt to reduce aseptic loosening, ceramics have been introduced. This study was designed to evaluate, compare and correlate the expression of Toll-like receptors (TLRs), their intracellular adaptors and proinflammatory cytokines in cultured macrophages challenged with titanium or zirconia particles, as well as particle-induced osteolysis in calvaria and hyperalgesia and edema in hind paw.

Main methods

TLRs and their adaptors were evaluated at the mRNA level by RT-PCR, and cytokine expression was evaluated at the mRNA and protein levels. Osteolysis and hyperalgesia and edema were evaluated in vivo, in calvaria and hind paw, respectively.

Key findings

Cultured macrophages challenged with zirconia or titanium particles expressed increased mRNA for TLRs 2, 3, 4 and 9, and their adaptors MyD88, TRIF and NF-κB and cytokines TNF-α, IL-1β and IL-6, which were also increased at protein level. Quantitative differences are evident and, in general, zirconia particle-induced pro-inflammatory gene expression was lower than that induced by titanium particles. In in vivo experiments, exposition to titanium or zirconia particles induced osteolysis in calvaria and hyperalgesia and edema in hind paw; however those induced by zirconia particles were significantly lower. There is a strong and positive correlation between the expressions of mRNA for TLR4, NF-κB, TNF-α, IL-1β and IL-6.

Significance

Collectively, our data suggest that zirconia ceramic particles are less bioactive than titanium particles.     

A density functional theory parameterised neural network model of zirconia

We have developed a Behler–Parrinello Neural Network (BPNN) that can be employed to calculate energies and forces of zirconia bulk structures with oxygen vacancies with similar accuracy as that of the density functional theory (DFT) calculations that were used to train the BPNN. In this work, we have trained the BPNN potential with a reference set of 2178 DFT calculations and validated it against a dataset of untrained data. We have shown that the bulk structural parameters, equation of states, oxygen vacancy formation energies and diffusion barriers predicted by the BPNN potential are in good agreement with the reference DFT data. The transferability of the BPNN potential has also been benchmarked with the prediction of structures that were not included in the reference set. The evaluation time of the BPNN is orders of magnitude less than corresponding DFT calculations, although the training process of the BPNN potential requires non-negligible amount of computational resources to prepare the dataset. The computational efficiency of the NN enabled it to be used in molecular dynamics simulations of the temperature-dependent diffusion of an oxygen vacancy and the corresponding diffusion activation energy.     

Effect of round curvature of anterior implant-supported zirconia frameworks: finite element analysis and in vitro study using digital image correlation

Two groups of 4-unit zirconia frameworks were produced by CAD/CAM to simulate the restoration of an anterior edentulous gap supported by 2 implant-abutment assemblies. Group 1 comprised straight configuration frameworks and group 2 consisted of arched frameworks. Specimens were made with the same connector cross-section area and were cemented and submitted to static loads. Displacements were captured with two high-speed photographic cameras and analysed with video correlation system. Frameworks and the implant-abutment assembly were scanned and converted to 3DCAD objects by reverse engineering process. A specimen of each group was veneered and the corresponding 3D geometry was similarly obtained after scanning. Numerical models were created from the CAD objects and the FE analysis was performed on the zirconia frameworks and on the FPDs bi-layered with porcelain (veneered frameworks). Displacements were higher for the curved frameworks group, under any load. The predicted displacements correlated well with the experimental values of the two framework groups, but on the straight framework the experimental vertical displacements were superior to those predicted by the FEA. The results showed that the round curvature of zirconia anterior implant-supported FPDs plays a significant role on the deformation/stress of FPDs that cannot be neglected neither in testing nor in simulation and should be considered in the clinical setting.