Iranian Journal of Pharmaceutical Sciences

Bioinert ceramics, like alumina and zirconia are used mainly for replacementsof bones, hip joints and for dental implants. Partially stabilized zirconia ceramics(PSZ or TZPwith 3 mol.% or 5 wt.% Y2O3), appear as perspective bioinert ceramicsbecause of their high strength and corrosion resistance. In order to fabricate complexshapes, it is essential to use a near net shape processing like gelcasting as anuncomplicated method which has appropriate potential of producing special shapeswith suitable green and sintered properties (like high mechanical properties and almostfull density and machinability of green bodies). Moreover, biocompatibility studieshave proved that this processing route is nontoxic. In this experiment, micro-structural observation performed to illustrate the effect of dispersant on homogeneityof gelcast 3Y-TZPbodies. It has been shown that it is possible to achieve uniformmicrostructure by means of appropriate amount of dispersant and ultrasonic wave.In addition, the machinability of these green bodies has been proven and somecomplex shaped bodies fabricated, in order to illustrate the capability of the process.

The overall goal of this study was to identify the appropriate biomaterials ableto facilitate the regeneration in rat's injured adult spinal cord. Acute damage to axonsis manifested as a breach in their membranes, ionexchange distortion across thecompromised region, local depolarization and even conduction block. It would beof particular importance to interrupt the progress of events happening after acuteinjury to the spinal cord. Repair strategies using transplants of cells have shown manyattractions in spinal cord repair studies. However, as the processes of purificationand growth require time, they cannot be fully implemented in acute injuries.Furthermore, application of cell grafts from other human or animal sources are likelyto provoke immune reactions in human patients. Immediate repairing or sealing theregions of compromised membrane with hydrophilic polymers or surfactants couldretard or reverse the permeabilization of nerve fiber membranes. Biodegradablepolymeric materials used for tissue engineering, made of either peptide or non-peptidecomponents, are considered as potential candidates. Application of the hydrophilicpolymer, polyethylene glycol (PEG), has showed to be effective in the repair of nervemembrane damage associated with severe spinal cord injury in adult rat. This classof large hydrophilic molecules can reverse the permeabilization of ruptured cellmembranes as well as anatomically reconnect their severed processes. Our preliminaryresults showed rather rapid partial restoration of the declined magnitude of compoundactions potentials (CAPs) in injured spinal cords, varying as a result of theintroduction of PEG's with different molecular weights.

The synthesis of titania via sol-gel method has been widely studied. In thepresent work, titania was deposited onto a titanium substrate via sol-gel method.Different processing parameters such as the repetition number of dipping/heattreatment process and dipping time have been studied to obtain the homogenous titaniacoating. Phase and microstructural evaluation of the powder and coating sampleswere performed, using X-ray diffraction and scanning electron microscopy. Theparticle size distribution of the powder was measured by zetasizer instrument.Based on the results obtained in this work, both rutile and anatase phases formedafter the heat treatment at 600 °C. In addition, the thickness and the morphologyof the coatings were found to be influenced by the repetition number of process.

Zein is one of the best biopolymer for edible film making and sugars are naturalplasticizers for biopolymers. In this research, sugars (fructose, galactose andglucose) at three levels (0.5, 0.7, 1 g/g of zein) were used as plasticizers for zeinprotein films and their water vapor permeability (WVP), oxygen permeability (OP)and atomic force microscopy (AFM) topography were studied. The pure zein filmshad the highest WVPand adding sugars to 0.7 g/g of zein decreased WVPof thefilms. In comparison among different zein films, those plasticized by galactose andfructose had the highest and lowest barrier properties, respectively. The zein filmswithout plasticizer had low OPand increasing plasticizers to 0.5 g/g of zeindecreased OPvalues in all samples. The films containing galactose and fructose hadthe lowest and highest OP, respectively. AFM images were used to evaluate surfacetopography (a qualitative parameter) and roughness (a quantitative parameter) ofthe zein films. The films plasticized by fructose had smoother surface and lowerroughness than the other films. Interrelation between WVP, OPand the roughnessof zein films were not observed.

The fabrication of complex-shaped parts out of (wt %) Co-28Cr-6Mo alloy bythree-dimensional printing (3DP) was studied using two grades of the alloy withaverage particle sizes of 20 and 75 μm. To produce sound specimens, 3DPprocessingparameters were tuned. The sintering behavior of the powders was characterized bythe dilatometric analysis. Batch sintering in argon atmosphere at 1280 °C for 2h wasalso performed. It was shown that complex-shaped biomedical parts with totalporosity of 12-25% and homogenous pore structure can be fabricated by the 3DPprocess.

Determination of blood compatibility is an important problem in blood contactingdevices. In this study, two classes of materials including polyurethane (based onpolyethylene glycol and poly tetrametylene oxide) and polyvinyl alcohol samples,with different hydrophilicity properties were synthesized and their physico-chemicalproperties were compared. Water uptake ratio, FTIR spectroscopy, and contactangle measurement were conducted. In vitrobiocompatibility experiments wereundertaken using L-929 fibroblast cell lines which demonstrated desired cellviability for all samples after 7 days. The adhesion of platelets from human plasmawas studied by optical microscopy. Blood coagulation time were also determinedwhich revealed polyurethane based poly tetramethylene oxide has better interactionby blood elements among all samples.

Wetability of biocompatible polymers can be improved by plasma surfacemodification. The purpose of this study was to surface modify an experimental poly(dimethylsiloxane) rubber (PDMS) material in order to improve its wetability andbiocompatibility. Surface properties of the PDMS were characterized using contactangles measurement for wetability analysis. Samples of experimental siliconerubber were surface modified by first argon, hydrogen, oxygen plasma treatment.In all cases, contact angles were measured. We have observed that oxygen, argon,and hydrogen glow discharges are quite effective in reducing the water contact angleof PDMS. However, indifferently to the efficiency of the treatment, practically allof the modified surfaces recovered great part of their original hydrophobicity.Surface modified materials had comparable contact angles to surfactant modifiedsilicone rubber, all being significantly lower than the unmodified material. Oxygenmicrowave discharge treatment proved an effective way of improving the wetabilityand biocompatibility of an experimental silicone rubber without altering bulkproperties.

Nowadays, hydrogels are widely used as wound dressings in biomedicalapplications. Similar to other types of the moist (wet) wound dressings, it isnecessary to have sufficient information about their dehydration kinetics during thepre-usage period (e.g. storage duration) and also the wound healing process. In thiswork, hydrogel wound dressings based on polyvinyl alcohol were prepared bycyclic freezing-thawing method and their dehydration process investigated byexperimental and mathematical methods. The dehydration tests were performed atatmospheric pressure at 37 °C, using hydrogels containing initial water content of70, 80 and 90 wt% and thickness of 1, 3 and 4 mm. The dehydration kinetics of eachhydrogel was determined by plotting the relative water loss (ratio of water loss toinitial water content) versus time. The obtained results showed that the dehydrationrate has inverse dependency to the thickness of wound dressing. On the other hand,the initial water content of the wound dressing has not significant effect on itsdehydration rate. To compare the obtained results with theoretical data, themathematical modeling on the basis of diffusion mechanism was developed topredict the dehydration process of the wound dressings. The results obtained fromthe mathematical modeling were in agreement with the experimental results showingthat the main phenomenon governing the dehydration of the wound dressings is thediffusion.

In this study, hydroxyapatite was coated on titanium substrates by plasma spraying process. A well-known porous and lamellar microstructure was found in the lateral and outer surface of coating. The phase composition was studied by XRD and the morphological and the microstructural aspects were investigated by scanning electron and optical microscopy. The hardness of coatings and substrates was measured by Vickers indentation method. For in vivo study, rabbit condyles were exposed to two groups of coated and uncoated samples. Radiographyically, different parameters such as bone lysis, sclerosis, displacement of samples and bone resorption were taken into consideration and no statistically differences between the two groups, with no sign of infection on the edges of each hole were found. Histopathological interpretation of all coated samples indicated that the extent of callus and thickness of speculae were quite distinct from that of uncoated group. In this group, the space between implant and canal was filled up with matured connective tissues and plenty of bone speculae of woven bone in nature. However, these speculaes were thinner and immature as compared to coated samples.

The purpose of this study was to investigate the deposition of the hydroxyapatite(HA) coating via the electrophoresis procedure. The HAdeposition was performedin an ethanol, methanol, acetone and isopropanol suspension. Methanol was foundto be the best deposition media. Among the different environmental conditions,including the encapsulation of the samples under two vacuum types of pressure(10-5-10-4and 2×10-2Torr) and also thepurge of the argon gas in the tube-likefurnace, the optimum environment was the one demonstrating the encapsulation underthe vacuum pressure of 2×10-2Torr (washing with argon gas of 99.9% purity). Afterthe examination of 3 sintering temperatures (1020, 1050 and 1100 ºC), the sinteringtemperature at 1050 ºC illustrated the most desired results. The samples sintered underthese conditions were apparently intact, most of the interfacial part of the coatingwas found to be attached to the substrate surface irregularities and no single crackswere observed.

To evaluate the ultimate compressive strength of five composite resins after 1 hour,24 hours, 7 days and 1 month. Twenty four cylindrical 4 mm×8mm specimens ofeach commonly used composite resins in posterior region (Nulite-F , Z250 , P60,Biscore, Tetric ceram HB) were prepared. Each group of composite resins weredivided into four time groups of 1 h, 24 h, 7 days and 1 month. All of specimensstored in an incubator with 37 °C. After each period of time all of the specimenswere tested by Zwick/Roell Z020 (Germany) for ultimate compressive strength atcross head speed of 0.5 cm/min. Results were analyzed by ANOVAand Scheffe test.P60 and Z250 had the highest and Nulite-F and Tetric ceram HB had the lowestcompressive strength at all the times. The difference between these two groups wasstatistically significant (p<0.05). The results of the Biscore was steady among theother groups. It is suggested to use Z250 or P60 in posterior restorations instead ofthe other composite resins tested.