Optimizing functionally graded tibial components for total knee replacements: a finite element analysis and multi-objective optimization study.

The optimal design of complex engineering systems requires tracing precise mathematical modeling of the system's behavior as a function of a set of design variables to achieve the desired design. Despite the success of current tibial components of knee implants, the limited lifespan remains the main concern of these complex systems. The mismatch between the properties of engineered biomaterials and those of biological materials leads to inadequate bonding with bone and the stress-shielding effect. Exploiting a functionally graded material for the stem of the tibial component of knee implants is attractive because the properties can be designed to vary in a certain pattern, meeting the desired requirements at different regions of the knee joint system. Therefore, in this study, a Ti6Al4V/Hydroxyapatite functionally graded stem with a laminated structure underwent simulation-based multi-objective design optimization for a tibial component of the knee implant. Employing finite element analysis and response surface methodology, three material design variables (stem's central diameter, gradient factor, and number of layers) were optimized for seven objective functions related to stress-shielding and micro-motion (including Maximum stress on the cancellous bone, maximum and mean stresses on predefined paths, the standard deviation of mean stress on paths, maximum and mean micro-motions at the bone-implant interface and the standard deviation of mean micro-motion). Then, the optimized functionally graded stem with 6 layers, a central diameter of 5.59 mm, and a gradient factor of 1.31, was compared with a Ti6Al4V stem for various responses. In stress analysis, the optimal stem demonstrated a 1.92% improvement in cancellous bone stress while it had no considerable influence on the maximum, mean, and standard deviation of stresses on paths. In micro-motion analysis, the maximum, mean, and standard deviation of mean micro-motion at the interface were enhanced by 24.31%, 39.53%, and 19.77%, respectively.

Bioactive gliadin electrospinning loaded with Zataria multiflora Boiss essential oil: Improves antimicrobial activity and release modeling behavior.

This study aimed to produce electrospun gliadin nanofibers containing Zataria multiflora Boiss essential oil (ZMEO) (5, 10, and 15% w/w), thereby developing active, sustained-release antimicrobial mats. By increasing the level of the ZMEO, the zeta potential and electrical conductivity increased, but the viscosity and consistency index decreased. All feed solutions demonstrated shear-thinning behavior, and the power law model was the best model. Field emission scanning electron microscopy (FESEM) images proved that the gliadin nanofibers showed a uniform, beaded-free structure at different levels of ZMEO, with an average diameter of between 403.87 ± 15.29 and 522.19 ± 11.23 nm. Increments in the level of ZMEO decreased the mats' tensile strength and Young's modulus but increased their elongation at break. Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) analysis confirmed that the ZMEO was well loaded within these structures, augmenting its thermal stability. The studied Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were more resistant to the ZMEO than the Gram-positive bacteria (Bacillus cereus and Staphylococcus aureus). The Peleg model was the most suitable model for describing the ZMEO release behavior, the mechanism of which was primarily Fickian diffusion.

Synthesis of superhydrophobic coatings based on silica nanostructure modified with organosilane compounds by sol-gel method for glass surfaces.

In the present study, the superhydrophobic coating was synthesized by spherical silica nanostructures modified with organosilane compounds for glass surfaces. To optimize the conditions in terms of cost-effectiveness and create a super-hydrophobic coating with a high contact angle, the response surface method of the central composite design (CCD) model was performed for the StÖber method, and the contact angle was defined as the response surface for the model. Tetraethoxysilane (TEOS) was used as a precursor and poly(dimethylsiloxane) (PDMS) was used to modify the surface of a spherical silica nanostructure synthesized by a one-step sol-gel method using a base catalyst. The accuracy of the research was checked by the contact angle measurement test and an angle of 162° was obtained. XRD, FT-IR, EDS, SEM, DLS, and AFM analyzes were performed to investigate the synthesis of silica nanostructure. Chemical resistance was performed in acidic, neutral, and alkaline environments and the contact angles were 127°, 134°, and 90°, respectively, which indicates that the coating created on the surface glass has good chemical resistance in acidic and neutral environments.

Corrigendum to "Effect of Chronic Morphine Consumption on Synaptic Plasticity of Rat's Hippocampus: A Transmission Electron Microscopy Study".

[This corrects the article DOI: 10.1155/2013/290414.].

Preparation and In-vitro Evaluation of Rifampin-loaded Mesoporous Silica Nanoaggregates by an Experimental Design.

The goal of this research is preparation, optimization and in-vitro evaluation of rifampin-loaded silica nanoparticles in order to use in the pulmonary drug delivery. Nanoparticles are exhaled because of their small size. Preparation of nanoaggregates in a micron-size scale and re-dispersion of them after deposition in the lung is an approach to overcome this problem. We used this approach in our research. Rifampin was selected as a model lipophilic molecule since it was a well-documented and much used anti tuberculosis drug. A half factorial design was used to identify significant parameters of the spray drying process. The results showed that feed concentration, feed pH and the interaction between feed flow rate and gas atomizer flow rate had statistically significant effects on the particle size of nanoaggregates. The Box-Behnken design was employed to optimize the spray drying process. Finally, a quadratic equation which explains the relation between independent variables and aerodynamic diameter of nanoaggregates was obtained. Rifampin-loaded silica nanoaggregates underwent different in-vitro tests including: SEM, Aerosol performance and drug release. The in-vitro drug release was investigated with buffer phosphate (pH=7.4). Regarding the drug release study, a triphasic pattern of release was observed. The rifampin-loaded silica nanoaggregates were capable of releasing 90% drug content after 24 h in combination patterns of release. The prepared rifampin-loaded nanoaggregates seem to have a potential to be used in a pulmonary drug delivery.

Piperazine and its carboxylic acid derivatives-functionalized mesoporous silica as nanocarriers for gemcitabine: adsorption and release study.

Piperazine-functionalized SBA-15 nanorods were synthesized by post grafting method with methyldimethoxysilylpropylpiperazine (MDSP). The carboxylic acid derivatives of piperazine-functionalized SBA-15 nanorods were obtained using two different kinds of precursors (bromoacetic acid and succinic anhydride). The prepared materials were used as nanocarriers for the anticancer drug (gemcitabine). The obtained samples were characterized by SAXS, N2 adsorption-desorption, SEM, TEM, DLS, thermogravimetric analysis, FTIR, Raman and UV spectroscopies. The adsorption and release properties of all samples were investigated. In vitro study included cell toxicity. It was found that the surface functionalization increases the interaction between the carrier and gemcitabine and results in the loading enhancement of the drug. In addition, the adsorption of gemcitabine on the modified mesoporous matrix depends on the type of the introduced functional groups. The carboxylic acid-modified samples have higher loading content, due to the strong interaction with gemcitabine. The maximum content of deposited drug in the modified SBA-15 nanorods is close to 36wt.% that it is related to PC2-SBA-15 sample which obtained using succinic anhydride. The obtained results reveal that the surface functionalization leads toward a significant decrease of the drug release rate without any appreciable cytotoxicity. No significant differences are observed among the drug release rate from the modified samples.

Effect of Chronic Morphine Consumption on Synaptic Plasticity of Rat's Hippocampus: A Transmission Electron Microscopy Study.

It is well known that the synapses undergo some changes in the brain during the course of normal life and under certain pathological or experimental circumstances. One of the main goals of numerous researchers has been to find the reasons for these structural changes. In the present study, we investigated the effects of chronic morphine consumption on synaptic plasticity, postsynaptic density thickness, and synaptic curvatures of hippocampus CA1 area of rats. So for reaching these goals, 24 N-Mary male rats were randomly divided into three groups, morphine (n = 8), placebo (n = 8), and control (n = 8) groups. In the morphine group, complex of morphine (0.1, 0.2, 0.3, and 0.4) mg/mL and in the placebo (sucrose) group complex of sucrose (% 0.3) were used for 21 days. After the end of drug treatment the animals were scarified and perfused intracardinally and finally the CA1 hippocampal samples were taken for ultrastructural studies, and then the obtained data were analyzed by SPSS and one-way analysis of variance. Our data indicated that synaptic numbers per nm(3) change significantly in morphine group compared to the other two groups (placebo and control) (P < 0.001) and also statistical analysis revealed a significant difference between groups in terms of thickness of postsynaptic density (P < 0.001) and synaptic curvature (P < 0.007). It seems that morphine dependence in rats plays a main role in the ultrastructural changes of hippocampus.

Poly[piperazinediium [aqua-bis(µ-pyridine-2,5-dicarboxyl-ato)zincate] dihydrate].

The polymeric title compound, {(C(4)H(12)N(2))[Zn(C(7)H(3)NO(4))(2)(H(2)O)]·2H(2)O}(n), was obtained by the reaction of zinc(II) nitrate hexa-hydrate with the proton-transfer compound (pipzH(2))(py-2,5-dc) (where pipz is piperazine and py-2,5-dcH(2) is pyridine-2,5-dicarboxylic acid) in aqueous solution. Each Zn(II) atom is coordinated in a distorted octa-hedral geometry by four O atoms and two N atoms from one water mol-ecule and two (py-2,5-dc)(2-) ligands, which also act as bridging ligands between Zn(II) atoms. π-π Stacking inter-actions between two aromatic rings of (py-2,5-dc)(2-) fragments, with centroid-centroid distances of 3.4747 (7) and 3.7081 (7) Šare observed. The crystal structure is stabilized by O-H⋯O and N-H⋯O hydrogen bonds.