| Biomedical polymer requires good biocompatibility, mechanical compatibility and long term stability. To fulfill the above requirements, polymer usually needs to have special treatment, including surface treatment and functionization. Many cases showed that untreated polymetic materials come into contact with blood or body fluid, some adverse responses may occur, such as thrombus formation and unfavorable immunoreactions. With the continuous development of biological materials, anticoagulant/antibacterial polymer materials have become the forefront and the key issues of biomedical engineering.Polyvinyl alcohol(PVA) has been chosen as the subject of this study since it provides both the needed strength and flexibility suitable for molding. PVA has the best formation properties of film such as tensile strength, pliability, moisture absorption and water-solubility. Further it has extensive application as biomedical material and showed low-toxicity and no pungency by security experiments. However, it can not meet the high standards of clinical care.It is well known that, carbon material is one of the best biomaterials. To materialize many of the prospect applications, the key is to functionalize graphene oxide in a controlled way to achieve desired properties, such as enhanced solution processing capability, and at the same time maintain the intrinsic properties of graphene oxide. Recently, polymer/oxide graphite nanocomposites, which are polymer modified with a relatively low amount of the layered graphite oxide, have attracted a great deal of attention because of their superior mechanical properties, barrier properties and high heat distortion temperature. However, anticoagulant and antimicrobial application of Polyvinyl alcohol/graphite oxide nanocomposites has not been reported.In this work, graphite oxide (GO) was synthesized according to the improved Brodie method. Graphene oxide was modified with chloroacetic to get carboxyl functional group(GeneO-COOH). GeneO-COOH nanocomposite was characterized by FT-IR, TG, TEM, Raman, DCA, XRD, WCA, AFM, UV. Functionalized graphene oxide was then doped with La3+ ions and the structure and properties of GeneO-La composite was characterized by FT-IR, TG, TEM, Raman, FS, XRD. Results showed that La3+ ions have been coordinated on graphene oxide sheet layer through physical and chemical bonding. Based upon the result of analysis, the antibacterial property was characterized by the kinetics of bacterial growth and inhibition zone method. The result showed that GeneO-La composite has a good inhibitory effect on the E.coli. When the concentration of 0.5 mg/mL, inhibition effiency was 96.40%. GeneO-La composite also has a good inhibitory effect on the S.aureus. When the concentration of 0.25 mg/mL, inhibition effiency was 99.81%. The GeneO-La on Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923) has significant inhibitory effect, a clear inhibition zone, respectively, up to 2.0,1.5 mm. There are also inhibitory effects on the S.aureus and the P.Aeruginosa. Therefore, the GeneO-La composite is a new graphene oxide composite, which has a good inhibitory effect. GeneO-La nanocomposite conformed to the Hormesis of rare earth. The higher the concentration of GeneO-La, the more it inhibits bacterial growth. We believe that the better antibacterial effect of GeneO-La than GO-La came from that GeneO has higer specific surface area and thus absorbed more La3+ ions. The heamocompatibility of nanocomposite was evaluated by hemolysis test and recalcification time test. It was observed that the plasma recalcification time gradually decreased as increasing the concentration of composite. The hemolysis rate was less than 5% in lower concentrations, which confirmed the Hormesis effect of rare earth elements. As a result, the GeneO-La composite is a new carboxylated graphene oxide composite, which has anticoagulant effect when it has lower concentrations. Based on the above work, we proposed mechanism of reaction of GeneO-La nanocomposites.A functional graphene oxide was prepared with glutamic acid and carboxylated graphene oxide sheet. The structure and properties of GeneO-Glu composite was characterized by FT-IR, TG, XRD, SCA and Zeta potential. The structure and mechanism of GeneO-Glu affected by different pH were also studied. And the hemocompatibility of nanocomposite was evaluated by hemolysis test and recalcification time test. It was observed that the plasma recalcification time gradually decreased with the increase in the concentration of nanocomposite. The hemolysis rate was less than 5%, which match the requirements of biomedial materials. The recalcification time of GeneO-Glu of 100μg/mL at pH=2 was about 25 min, about 8 min more than that of Ca2+ with PPP. GeneO-Glu of 100μg/mL at pH=2 was about 28 min, about 11 min more than that of Ca2+ with PPP. GeneO-Glu of 100μg/mL at pH =10 was about 22 min, about 5 min more than that of Ca2+ with PPP. GeneO-Glu nanocomposites at different pH, Zeta potential and particle size were investigated. Stability test and formation mechanism of GeneO-Glu nanocomposite was also discussed.In order to make the nanocomposites have better antibacterial properties, a composite intercalation agent (GeneO-Glu-La) with anticoagulation and antibacterial function was synthesized. The antibacterial activity of GeneO-Glu-La to Escherichia coli (ATCC25922) and Staphylococcus aureus (ATCC25923) were evaluated by a series of bacterial test. The results indicated that GeneO-Glu-La nanocomposite has great blood compatibility and is antibacterial. Biocompatibility of biomedical material were evaluated by hemolysis test, recalcification time test and platelet adhesion test. It was observed that the plasma recalcification time gradually decreased with increase in the concentration of composite. The hemolysis rate was less than 5% in lower concentrations, indicating hormesis effect of rare earth elements. Therefore, the GeneO-Glu-La composite is a new carboxylated graphene oxide composite, which has anticoagulant effect when it has lower concentrations.Based on the above works, a series of novel polyvinyl alcohol (PVA)/functional grapheme oxide nanocomposites were prepared by solution blending technology. The mechanical property results indicated that PVA has poor mechanical strength. While PVA/GeneO, PVA/GeneO-COOH, PVA/GeneO-La, PVA/GeneO-Glu and PVA/GeneO-Glu-La demonsarted better mechanical strength. When the GeneO content was 0.01%, it showed improved mechanical properties. Toughening tensile strength and elongation at break, respectively, improved 112.9% and 43.3% compared to PVA. As GeneO-COOH content was increased to 0.02%, the tensile strength and elongation at break, respectively, improved 136.7% and 44.6%. GeneO-Glu content was 0.02%, the tensile strength and elongation at break, respectively, improved 130.0% and 40.9% than PVA; GeneO-La content was 0.01%, the tensile strength and elongation at break, respectively, improved 132.5% and 66.4% than PVA; GeneO-Glu-La showed better effect, when GeneO-Glu-La content was 0.01%, the tensile strength and elongation at break, respectively, improved 140.1% and 1113.6.% than PVA. At the same time XRD showed the exfoliated structure of the nanocomposites. Biocompatibility was evaluated by hemolysis test, recalcification time test, platelet adhesion test, the dynamic blood-clotting and protein adsorption test. The hemolysis rate all under the international standard, adhering little platelet, protein and on the surface. Protein adhered to PVA/GeneO-Glu-La reduced 27.94% compared to PVA. |
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