Mechanical and Swelling Characteristics of Kappa-carrageenin/Poly-N-isopropylacrylamide Blend Hydrogels

Two- or multi-component hydrogels consisting of the three-dimensional network of polymer chains play more and more significant role in the field of biomaterials such as contact lens, burn dressing drug delivery systems etc or in some technical fields such as gel actuators, sensors, absorbents etc. In the work, a novel blend hydrogel composed of kappa-carrageenin (KC) and polyisopropylacrylamide (PNIPAAm) was prepared via gamma-radiation technology at room temperature. The main component of the hydrogels is a typical temperature sensitive polymer PNIPAAm. As the second component, KC is a kind of natural macromolecules. The properties of the gels, such as gel strength, and swelling behavior were investigated. The incorporation of relatively small content (up to 5 wt.%) of KC could obviously improve the mechanical properties and swelling capacity. 3% KC content in the blend hydrogel is preferable for better strength and swelling properties. On the other hand, as a kind of polysaccharide, KC would be degraded by γ-rays; so<br />suitable dose must be controlled carefully. Here the total dose used was controlled below 3 kGy. KC is soluble in water. If the hydrogels synthesized in the work were as usually extracted in water or other polar solvent such as methanol, the KC in hydrogels would be also washed out completely together with unreacted monomer and linear polymer, and the action of KC in the blend hydrogels would be disappeared. Otherwise, the results published before showed that the unreacted monomer and linear polymer in the hydrogels were very small, no more than 3-5%, which would not affect the properties of the hydrogels.

Influences of NBR/Al2O3/YSZ as Fillers for PMMA Composite on the Thermal Properties

The aim of this study is to investigate the effect of nitrile butadiene rubber (NBR as impact modifier) together with Al2O3/YSZ (toughening) as different filler ratios in PMMA material on the DSC thermal properties. PMMA matrix without fillers was mixed between PMMA powder and 0.5 wt.% of BPO and fixed at 7.5 wt.% of NBR particles with different ratios of filler (1, 3, 5, 7 and 10 wt.%) of Al2O3/YSZ mixture filler by (1:1 ratio). The TGA data were shown that the PMMA composite have better thermal stability compared to unreinforced PMMA matrix. While, DSC curves shows slightly similar in Tg value. DSC results also indicated the presence of unreacted monomer content for both reinforced and unreinforced PMMA composites. As conclusion of this study, the reinforced PMMA composites are improved in thermal stability compared to unreinforced PMMA matrix.

Safety Assessment of Polyquaternium-22 and Polyquarternium-39 as Used in Cosmetics

Polyquaternium-22 and polyquaternium-39 are polymers that function as antistatic agents, film formers, and hair fixatives in cosmetic products. These ingredients are being used at concentrations up to 2% (polyquaternium-22, in a rinse-off product) and up to 3% (polyquaternium-39, in rinse-off and leave-on products). The unreacted monomer content of these ingredients was considered low and of no toxicological concern. Limited data showed no skin irritation/sensitization. Although these ingredients were nongenotoxic in bacterial assays, mammalian genotoxicity, carcinogenicity, and reproductive and developmental toxicity data were not available. These polymers, however, are large, highly polar molecules that would likely not be absorbed, and neither local effects in the respiratory tract nor systemic toxicity are expected following product application/exposure. The Expert Panel concluded that polyquaternium-22 and polyquaternium-39 are safe in the present practices of use and concentration in cosmetic formulations.

Testing endodontic sealers on human umbilical vein endothelial cells

The toxic potential of the endodontic sealers ingredients, especially the unreacted monomer, that can irritate the periapical tissue and interfere with the healing process, thus having a negative impact on the biocompatibility of the material. The aim of this study was to evaluate the influence of three experimental endodontic sealers on cells viability in vitro. Human umbilical vein endothelial cells (HUVEC) were used. The experiments were done with solid samples and extracts of sealers in artificial saliva and water. The experiments evaluated the cytotoxicity of the residual monomers that resulted from the tested composites. The decrease in cell viability was quantified by colorimetric measurement of formazan. The components of the sealers dissolved in artificial saliva and water were determined by high performance liquid chromatography (HPLC). The HUVEC are a novelty for testing the endodontic sealers biocompatibility, with certain advantages compared to other cell types used in the literature, e.g. HELA cells, fibroblasts. The data showed that cytotoxicity was directly linked with the unreacted monomer — 2-hydroxyethyl methacrylate (HEMA) present in these composites. Two of the three formulations had little or no cytotoxic effect, which makes them suitable for further testing in order to be used in endodontic treatment.