Predicting permeability of regular tissue engineering scaffolds: scaling analysis of pore architecture, scaffold length, and fluid flow rate effects.

The main aim of this research is to numerically obtain the permeability coefficient in the cylindrical scaffolds. For this purpose, a mathematical analysis was performed to derive an equation for desired porosity in terms of morphological parameters. Then, the considered cylindrical geometries were modeled and the permeability coefficient was calculated according to the velocity and pressure drop values based on the Darcy's law. In order to validate the accuracy of the present numerical solution, the obtained permeability coefficient was compared with the published experimental data. It was observed that this model can predict permeability with the utmost accuracy. Then, the effect of geometrical parameters including porosity, scaffold pore structure, unit cell size, and length of the scaffolds as well as entrance mass flow rate on the permeability of porous structures was studied. Furthermore, a parametric study with scaling laws analysis of sample length and mass flow rate effects on the permeability showed good fit to the obtained data. It can be concluded that the sensitivity of permeability is more noticeable at higher porosities. The present approach can be used to characterize and optimize the scaffold microstructure due to the necessity of cell growth and transferring considerations.

Some biomarkers in acute myocardial infarction.

BACKGROUND: Several changes in serum biochemical factors occur in acute myocardial infarction (AMI). Recently alterations in serum levels of homocysteine (Hcy), sialic acid (SA) and high sensitive C-reactive protein (HS-CRP) has been attended as risk factors and index for prediction. This study was aimed to show the alterations in these factors and their relationships in AMI. METHODS: Thirty four patients with AMI were enrolled in this case-control study. Also 51 apparently healthy individuals were selected as control group. Serum was prepared from all subjects in fasting state. Hcy and HS-CRP were measured using ELISA and SA was determined by Erlich method. RESULTS: Serum levels of Hcy, SA and HS-CRP in AMI patients were 14.35±2.55λmol/l, 73.54±2.82 mg/dl, and 17.32±3.45 mg/l, respectively and in the control group they were 8.31±2.66 λmol/l, 59.82±2.70 mg/dl and 2.77±1.98 mg/l, respectively. Statistical analysis of data showed that serum level of Hcy, SA, and HS-CRP in the patients with AMI was significantly higher than those of control (P < 0.001). Also significant correlation was observed between Hcy-HS-CRP (r= 0.63), SA- Hcy (r= 0.73), and SA - CRP (r= 0.75) (P < 0.05 for all items). CONCLUSION: Our findings showed increased level of HS-CRP, SA, and Hcy in AMI patients. Also obtained data indicated a direct and significant correlation between HS-CRP as an inflammation index and Hcy and SA. Hence these two factors can be used as biomarkers in this disease.