Adsorption of calcium ions by graft copolymer of acrylic acid on biopolymer chitin

Selective sorption of Fe(II) ions over Cu(II) and Cr(VI) ions by cross-linked graft copolymers of chitosan with acrylic acid and binary vinyl monomer mixtures

Low-cost and environment-friendly polymeric adsorbents for sorption of heavy metal ions were synthesized by simultaneous graft copolymerization and cross-linking of acrylic acid alone and with comonomers glycidyl methacrylate, acrylamide and acrylonitrile onto chitosan using free radical initiator and cross-linker in aqueous medium. Structural aspects of cross-linked graft copolymers have been characterized by FTIR, SEM, TGA/DTA, XRD and swelling behavior at pH 2.2, 7.0 and 9.4. An attempt has been made to study sorption of Cr(VI), Cu(II) and Fe(II) ions on cross-linked graft copolymers by equilibration method and to establish a relationship between structural aspects of graft copolymers and metal ion uptake efficiency and selectivity. Solutions of individual ions were used for non-competitive sorption onto synthesized bio-adsorbents as a function of change in contact time, temperature, pH and metal ion concentration in feed. Competitive sorption investigation was performed from an aqueous solution of ternary metal ions by batch equilibration at 25°C and at 7.0pH. Cross-linked graft copolymers showed better results than unmodified chitosan and showed preferential sorption of Fe(II) ions than Cu(II) and Cr(VI) ions.

Sulfonated chitosan and dopamine based coatings for metallic implants in contact with blood

Thrombosis and calcification constitute the main clinical problems when blood-interacting devices are implanted in the body. Coatings with thin polymer layers represent an acknowledged strategy to modulate interactions between the material surface and the blood environment. To ensure the implant success, at short-term the coating should limit platelets adhesion and delay the clot formation, and at long-term it should delay the calcification process. Sulfonated chitosan, if compared to native chitosan, shows the unique ability to reduce proteins adsorption, decrease thrombogenic properties and limit calcification. In this work, stainless steel surfaces, commonly used for cardiovascular applications, were coated with sulfonated chitosan, by using dopamine and PEG as anchors, and the effect of these grafted surfaces on platelet adhesion, clot formation as well as on calcification were investigated. Surface characterization techniques evidenced that the coating formation was successful, and the sulfonated chitosan grafted sample exhibited a higher roughness and hydrophilicity, if compared to native chitosan one. Moreover, sulfonated surface limited platelet activation and the process of clot formation, thus confirming its high biological performances in blood. Calcium deposits were also lower on the sulfonated chitosan sample compared to the chitosan one, thus showing that calcification was minimal in presence of sulfonate groups. In conclusion, this sulfonated-modified surface has potential to be as blood-interacting material.

A glass polyalkenoate cement carrier for bone morphogenetic proteins

This work considers a glass polyalkenoate cement (GPC)-based carrier for the effective delivery of bone morphogenetic proteins (BMPs) at an implantation site. A 0.12 CaO-0.04 SrO-0.36 ZnO-0.48 SiO2 based glass and poly(acrylic acid) (PAA, Mw 213,000) were employed for the fabrication of the GPC. The media used for the water source in the GPC reaction was altered to produce a series of GPCs. The GPC liquid media was either 100 % distilled water with additions of albumin at 0, 2, 5 and 8 wt% of the glass content, 100 % formulation buffer (IFB), and 100 % BMP (150 µg rhBMP-2/ml IFB). Rheological properties, compressive strength, ion release profiles and BMP release were evaluated. Working times (Tw) of the formulated GPCs significantly increased with the addition of 2 % albumin and remained constant with further increases in albumin content or IFB solutions. Setting time (Ts) experienced an increase with 2 and 5 % albumin content, but a decrease with 8 % albumin. Changing the liquid source to IFB containing 5 % albumin had no significant effect on Ts compared to the 8 % albumin-containing BT101. Replacing the albumin with IFB/BMP-2 did not significantly affect Tw. However, Ts increased for the BT101_BMP-2 containing GPCs, compared to all other samples. The compressive strength evaluated 1 day post cement mixing was not affected significantly by the incorporation of BMPs, but the ion release did increase from the cements, particularly for Zn and Sr. The GPCs released BMP after the first day, which decreased in content during the following 6 days. This study has proven that BMPs can be immobilized into GPCs and may result in novel materials for clinical applications.

Preparation and scanning electronic microscopy study of chitosan/polyvinyl (alcohol)-encapsulated crude urease extract

Small capsules of a blended chitosan (QTS)-polyvinyl alcohol (PVA) mixture were prepared by the coacervation salting-out method using sodium sulphate (20%, w/v) as a coagulation solution followed by further treatment with a solution containing formic aldehyde (7%, w/v), sulphuric acid (20%, w/v) and sodium sulphate (25%, w/v). The morphology of the microcapsule wall was observed by scanning electron microscopy (SEM). The enzyme urease, as a crude extract, was encapsulated and the cross section of the loaded capsule was observed by SEM. The enzyme extract was fully immobilized and the enzymatic assay showed the presence of the enzyme in an active form with a shift in the pH maximum activity to a lower pH.