فهرست مطالب nader nezafati

The purpose of this study was to prepare and compare a hydroxyethyl cellulose/hyaluronic acid (HEC/HA)-based scaffold with and without gelatin for the treatment of second-degree partial-thickness burns. The scaffolds were prepared by freeze-drying method from the aqueous solutions of the mentioned polymers. Microstructural examination by scanning electron microscopy (SEM) indicated the average pore size of 120 and 98 µm for the gelatin-free and gelatin-containing scaffolds, respectively. According to the dynamic rheology measurements (DMA), all the solutions were flowable in which, the loss modulus was higher than the storage one. Moreover, the solutions revealed shear-thinning behaviour at low frequencies, which changed to shear thickening at frequencies higher than 100 s-1. Both loss and storage modulus increased by adding gelatin to the polymer solutions. The scaffolds water uptake was up to 3,000%. The addition of gelatin to the HA/HEC solution increased the polymer network collapse up to 2 hours and led to reducing the scaffolds degradation rate. Cytotoxicity assay in the presence of the scaffolds showed that more than 80 % of the fibroblast cells were viable (compared to the control group), meanwhile, the presence of  gelatin had a positive effect on the metabolic activity of the cells and increased the rate of cell proliferation.  Scratch test results showed the ability of scaffolds to increase the cell migration rate compared to the control sample. The hydroxyethyl cellulose/hyaluronic acid/gelatin scaffold due to the presence of gelatin and improved the cell migration, which indicating the rapid re-epithelialization, reduced wound contraction to   73 % within 24 hours.

The injectable composites were formulated from melt-derived 45S5 bioactive glass powder and gum tragacanth. The effect of tragacanth concentration (2 and 4 w/v%) and powder to liquid ratio (P/L= 1.5 to 2.5) on rheological properties, injectability, degradation, swelling, and bioactivity the composites was studied. With the increase of P/L ratio and tragacanth concentration, the force required for injection of the composites increased, however, the formulated composites showed maximum injection force of 15 N, which seems to be proper for surgical purposes. The formulated composites showed positive thixotropic behavior and the composites prepared with 2% tragacanth showed greater thixotropy than ones made of 4% tragacanth. The composites formulated by 2% tragacanth showed much more resistance against degradation and swelling. The bioactivity assay confirmed the formation of flake-like apatite nanostructures on the surface of nanocomposites on initial days of immersion in the SBF.

Three-dimensional structures such as nanofibrous scaffolds are being used in biomedical engineering as well as provide a site for cells to attach and proliferate leading to tissue formation. In the present study, poly(vinyl pyrrolidone) (PVP)/ poly(vinyl alcohol)(PVA) hybrid nanofibrous scaffold was synthesized by electrospinning.
The effect of adding nano hydroxyapatite (n-HA) and also Epoxypropoxy-propyl-trimethoxysilane (EPPTMS) as a crosslinking agent on morphology and cell behaviour of the nanofibers was investigated.
Scanning electron microscope (SEM) observations showed that all kinds of nanofibers represented uniform and well-ordered morphologies without formation of any beads by controlling the synthesis parameters. The average ûber diameter of PVP-PVA was 260 nm. n-HA was synthesized by wet chemical process. The synthesized n-HA was characterized by XRD for structural analysis. Transmission electron microscope (TEM) revealed that HA particles had nanosized dimensions (in the range of 40-100 nm). The presence of n-HA within electrospun PVP-PVA nanofibers was confirmed by XRD and Fourier transmission infrared spectroscopy (FTIR) analyses. The average ûber diameter was decreased to 136 nm when n-HA was added in the composition of PVP-PVA. FTIR analysis depicted that PVP-PVA nanofibers were linked to EPPTMS as a biocompatible material by the covalent bond. Although adding n-HA caused to decrease the diameter of PVP-PVA nanofibers, addition of EPPTMS within PVP/PVA/n-HA nanofibers induced increasing distribution of fiber diameter as it enhanced to 195nm. In addition, the proper proliferation of G292 osteoblastic cells without any cytotoxicity was observed for the nanofiber.
Since these materials have been known as biomaterials, PVP/PVA/n-HA-EPPTMS nanofibers can be propounded as a good candidate for bone tissue engineering application.

Calcium phosphate cements are among the formable calcium phosphate cements which are widely used for reconstruction of hard tissue injuries. Unfortunately, due to low mechanical strength, the application of such materials is only limited to non-load bearing like skull. We have investigated some mechanical and characteristics of a calcium phosphate cement which was reinforced with glass fiber. Compressed strength, setting time, phase composition and microstructure of the composite cement were among the cases which were investigated using appropriate techniques. The results indicated that adding only 15 weight percent of glass fiber (with about 100µm diameter) which was prepared using sol-gel method, does not show any meaningful change in the setting time of calcium phosphate cement This period of time was estimated about 20 minutes. Compressed strength of the cements without any fibers was 0.635MPa which was increased by adding fiber to 3.69MPa.The toughness of the cement was changed from 0.098KJ/m2 for cement without any fibers to 0.545KJ/m2 cement containing fibers. The XRD pattern of the composite samples which were maintained in the Ringer's solution showed that the reactant materials of the cement have almost thoroughly converted to hydroxyapatite which in this case does not show much difference with the non-fiber samples. As a whole, it seems that using glass fiber prepared by sol-gel method can considerably increase mechanical strength and toughness of calcium phosphate. This occurs without any effect on the quality of the cement.