Bone tissue scaffolds made from either natural or synthetic polymers are employed to promote bone healing. However, lack of sufficient or poor mechanical properties such as low integrity and ...stability reduces their medical applications. Crosslinking, defined as induction of chemical or physical links among polymer chains, is a simple method generally used to modify mechanical, biological and degradation properties of hydrogels. Although crosslinking through chemical reactions improves the mechanical properties of bone substitutes, most of the reagents used for this aim demonstrate undesirable effects and may exert toxic reactions. Glutaraldehyde is a widely-used chemical crosslinker with unique ability to crosslink a wide variety of biomaterials; however, many contradictory views have been recently raised on its cytotoxic effects. By keeping this limit in mind, green chemicals or natural crosslinking agents have been shown to provide desired improvements in mechanical properties of bone scaffolds. Therefore, developing more efficient crosslinking materials and methods are desirable to obtain crosslinked scaffolds with perfect properties in bone tissue engineering from different biopolymers such as collagen, gelatin, cellulose, chitosan, alginate, etc. In this review, we focused on developed or developing modalities used to improve mechanical properties of various bone scaffolds and matrices based on common crosslinking reagents.
Objective: Reporter gene transfer to mammalian cells receives a great deal of attention due to its importance for molecular biology, embryology and developmental biology studies. Among DNA transfer ...technologies to eukaryotic cells, lipofection is known as the most widely used because of its easy handling procedure, low cell mortality and the natural pathway it undertakes.Materials and Methods: In this study we have examined the transfectability of two cell types: CHO and Vero cells via Lipofection in four different treatments, with combination of exposure duration, 3 and 6 hrs, and different plasmid DNA concentration, 0.5 and 1μgs. A fusion protein expression vector, pUcD2. PTS2-EGFP was used to direct the EGFP protein to peroxisomes after expression of related cDNA. An SPSS analysis was preformed after counting the positive cells.Results: optimum gene expression was found when using 1 μg DNA treated for three hrs for CHO cells, and 1 μg DNA treated for six hrs for Vero cells.Conclusion: The result suggests that CHO lipofection efficiency is significantly increased by both the DNA concentration and exposure time increment; however, an increase in exposure time has less significant effect on low DNA concentration conditions. The same results have been observed for Vero cells. Optimum expression was obtained with highest DNA concentration.
