Iranian polymer journal
Volume:19 Issue: 6, 2010

Synthetic polymeric systems are considered vitally important in tissue regeneration.The reasons lay behind their specific characteristics such as porosity,hydrophilicity, degradation time, and mechanical properties which are variable toa large extent. The segmented polyurethanes have been used as biomaterials inmedical field because they possess unique properties. In this study, the perforatedpolyurethane (PPU) scaffold as cartilage substitution was prepared and evaluatedthrough biological assays. During the in vitro stage, the behaviour of both primarychondrocyte cells and L929 cell line in presence of PPU were examined. To evaluatein vivo performance of the scaffolds, PPUs were implanted in the scapula cartilage oftwelve mixed-bred female sheep and comparisons were made with the implantedautologous cartilages as control. The results of in vitro studies showed some round andaggregated chondrocyte cells grown after 2 weeks of cell culture along with aconsiderable growth and attachment of L929 cells. In vivo studies showed that there isno significant difference between the restored PPUs and the autologous cartilagecontrol. Our studies support the potential use of PPU as a proper substitute or ratheras an assistant in cartilage repair. Obviously, further studies are needed to qualify theconstituted cartilages regarding proteoglycan and collagen productions.

Some specific structure-properties relationship of a polyampholyte carboxymethylchitosan-g-poly(acrylic acid-co-trimethylallyl ammonium chloride) (CMCTS-g-(PAA-co-PTMAAC)) hydrogel and the properties of water in the hydrogel wereinvestigated by DSC measurement. The freezing water and non-freezing watercontents of the hydrogel were determined quantitatively by examining their relationshipwith the structure and constitutive parameters of the polyampholyte hydrogel. Theexperimental results showed that higher swelling ratio of the hydrogel could decreasethe content of the non-freezing water. It was found that the shape of the exothermic orendothermic curves and the peak temperature were strongly influenced by theheating/cooling rate or heating/cooling cycling. A hysteresis loop was evident during theprocess of heating/cooling cycling and the temperature interval between Tmax+ andTmax- was increased by higher heating/cooling rate. The cross-linking degree of thehydrogel, molar ratio of two monomers and the neutralization degree of the anionicacrylic acid also have a great influence on the water content at various states. Theresults showed that the amount of non-freezing water in the hydrogel increasedgradually as the cross-linking degree increased, but it was reduced while the molarratio of TMAAC increased. By increasing the neutralization degree of acrylic acid, theamount of the non-freezing water was also increased

Biodegradable polymers have been extensively investigated as nano-carrierdelivery systems in anti-cancer therapy. The anti-cancer drugs generally sufferfrom low aqueous solubility, short in vivo half-life and haphazard side effects. Inthis work, biodegradable poly(d,l-lactide-co-glycolide) nanoparticles (PLGA) containingtamoxifen citrate as a model anti-cancer drug were prepared using an o/w emulsification-solvent evaporation method. Dynamic light scattering (DLS), scanning electronmicroscopy (SEM) and analytical HPLC procedures were used to characterize thenanoparticles in terms of particle size, morphology and drug content. The characteristicsof the nanoparticles including size, drug loading, and the efficiency ofencapsulation were optimized by means of a full factorial experimental design over theinfluence of four different independent variables. Analyses of variance (ANOVA) wereused to evaluate the optimized conditions for the preparation of nanoparticles. Basedon the results, the most significant variables were homogenization speed andconcentration of PLGA in organic phase with known total volume. Also, the interactionsbetween the percentage of PVA and the amount of PLGA and organic phase volumewere the most important cross-factor parameters. The optimum formulation conditionwith 192 nm mean size and 33 w/w% loading capacity was established by using3 mg.mL-1 PLGA/dichloromethane in 7 w/v% PVA solution and 40% oil/water solventratio for emulsification at 24000 rpm homogenization rate. The results of this workfacilitate the development of nano-carriers for tamoxifen delivery through optimizationstudies to control nanoparticles with specific properties and establish correlationsbetween optimum production conditions and the required nano-carrier desiredcharacteristics

Tissue engineering scaffolds produced by electrospinning feature a structuralsimilarity with the natural extracellular matrices. In this study, for the first time,poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) and chitosan/poly(vinyl alcohol)(PVA) were simultaneously electrospun from two different syringes and mixed on arotating drum to prepare homogeneous nanofibrous composite scaffold. Theconcentration of the spinning solutions and the ratios of PCL/HA-chitosan/PVA werevaried and adjusted to acquire nanofibres with narrow diameter distribution. It wasfound that the PCL/HA spun fibres became thick and non-uniform in diameter bydecreasing the solution concentration and voltage, and yet the effect of flow rate wasnegligible. Meanwhile, the diameters of chitosan/PVA fibres decreased and becamemore uniform by decreasing the solution concentration and tip-to-target distance.Furthermore, HA nanocrystals reinforce the scaffold and increase its mechanicalstrength, though by changing its mechanical behaviour make it more brittle. SEMmorphology of the PCL/HA electrospun nanocomposite revealed that HA nanocrystalswere kept suspended in solution during the electrospinning process, and laid inside thePCL nanofibres. This feature may provide a mechanism for controlled release of HAnanoparticles in cell culture studies. It was assumed that the nanofibrous compositescaffold of electrospun PCL/HA-chitosan/PVA can potentially be used for theosteogenic differentiation of stem cells.

In recent years, the application of high-density multi-layer circuit boards in electronicproducts has put forward more set of requirements, especially on the thermalstability of the insulation ink, as the key material in the manufacturing of printedcircuit board (PCB). Both o-cresol formaldehyde epoxy (OCFEP) and cyanate ester(CE) resins show outstanding thermal stability for application in PCB. In this work,cyanate prepolymer (PCE) and a PCE/OCFEP composite system were prepared. Thecuring behaviour of cyanate prepolymer/o-cresol formaldehyde epoxy resin systemwas studied with non-isothermal differential scanning calorimetry (DSC). Combinedwith the application requirement, the curing process of the system was determined as:130°C/1h+140°C/1h+180°C/1h. The DSC results also revealed that the apparentactivation energy of curing reaction was 83.22, 66.32 and 78.48 kJ/mol when PCEcontent was 80, 60 and 40 wt%, respectively. This indicates that there was an optimalproportion of PCE and OCFEP in the system. The curing kinetics followed the first orderreaction. Theoretical analysis on the curing proccess of the system with 60 wt%PCE showed that the thermal stability increased with increased post-processingtemperature. This study could provide some guides and basic data for the developmentof insulation ink for high-density multi-layer printed circuit boards.