Preparation And Properties Of Polyacrylic Acid / Functionalized Oxidized Graphene Composites

Many drugs can’t be used the traditional preparation and conventional route of administration because of its poor solubility, therefore a new type of biocompatible nano-agents may solve this problem.Graphene oxide (GeneO) is the unlimited extension of the two-dimensional space in the single-layer carbon atoms with the carbonyl, hydroxyl and carboxyl functional groups. Because of its large specific surface area, high drug loading, good hydrophilicity and mechanical properties, GeneO is obtained extensive attention by researchers. Recent years, with in-depth study of GeneO, functional modification and development of graphene oxide become a hot topic. Surface chemical composition of GeneO has a great impact on hydrophilic properties, mechanical properties, biological properties, as well as new preparation of nano-carrier. Different organic modifier linked on the GeneO surface can make GeneO having unique properties, and the content of the surface organic functional groups have significant impact on the subsequent reaction of GeneO.In recent years, polymer materials are increasingly widely used in drug release carrier. Polymer drug delivery system can make use of specific distribution of nanoparticles of different sizes in the human body, and is biocompatibility of the immune system to not be recognized. As a drug carrier, it can make real of targeting transportation, sustaining release administration, maximizing efficacy with minimal drug dose and minimizing side effects. Polyester compounds such as polyacrylate, polylactide, poly lactide, polycaprolactone and their copolymers have excellent biocompatibility and biodegradability, which have been widely used in controlled release and targeted drug formulations, and other biomedical field.This thesis is to improve the biocompatibility of GeneO through modifing the surface of GeneO, and then reactioned with acrylic acid to design a novel nano-drug delivery system with different morphology and particle size, pH stimulus-response propertise.To achieve these goals, I used different organic modifiers to modify GeneO, and three kinds of modified GeneO with different hydrophilic propertise were synthesized, and did structural characterization, biological properties (antibacterial characterization and blood compatibility characterization) and in vitro cytotoxicity testing of the materials.Firstly, I used chloroacetic acid to do carboxyl modification of GeneO examed by FTIR, XRD, TG, Raman and other tests, which showed that the carboxyl graphene oxide (GeneO-CH2-COOH) was obtained. The carboxyl content of the material and the static contact angle testing showed that different carboxyl content of GeneO could be changed with the weight ratio of GeneO with chloroacetic acid, and the carboxyl content was increasesd with the increasing chloroacetic acid content and hydrophilic propertise. The antibacterial performance, blood compatibility and in vitro cytotoxicity of GeneO-CH2-COOH were also studied. The results showed that GeneO-CH2-COOH had some antibacterial properties of E.coli and S.aureus, the hemolysis rate and the recalcification time tests indicated that the material had a good blood compatibility. Materials vitro cytotoxicity assays showed that the material cytotoxicity assay for0or1.Chloroacetic acid is a toxic reagent, subject to certain restrictions in the application. For the first time, a free radical initiator-azobisisobutyronitrile (AIBN) was used in my experiment to modify GeneO and the structure of GeneO-C(CH3)2-COOH was tested by FT-IR, XRD, TG and Raman. Carboxyl content can be controlled by the weight ratio of GeneO with AIBN, when the mass ratio of GeneO and AIBN was1:50, the carboxyl content can reach7.7mmol/g, and its carboxyl content was gradually increased with the AIBN increased. We studied the biological properties and in vitro cytotoxicity of GeneO-C(CH3)2-COOH. Compared with GeneO-CH2-COOH, the E.coli antimicrobial properties of GeneO-C(CH3)2-COOH was increased and the antibacterial performance against S.aureus was decreased. Hemolysis rate and the recalcification time tests indicated that the material had good blood compatibility; Vitro cytotoxicity assays showed that the material in short-term was non-cytotoxic (Grade0). The results showed that biocompatibility of GeneO-C(CH3)2-COOH was better than GeneO-CH2-COOH.To further enhance the hydrophilic/hydrophobic properties of GeneO, we grafted oleic acid molecules on the surface of GeneO, and then grafted poly glycol molecules through ring-opening reaction of peroxide the double bond in the oleic acid chain, and new amphiphilic structure of modified GeneO (GeneO-Oleic acid-PEG) was synthesised. The structure was characterized by FT-IR, XRD, TEM and Raman. When the mass ratio of GeneO with Oleic acid was1:50and PEG with GeneO-Oleic acid was15:2, a new particle was formed with modified GeneO nuclear and PEG shell. We studied its biological properties and in vitro cytotoxicity. Compared with GeneO-C(CH3)2-COOH, the E.coli antimicrobial properties of GeneO-Oleic acid-PEG was increased as well as antibacterial performance against S.aureus. Hemolysis rate and the recalcification time teats indicated that the material had good blood compatibility. Vitro cytotoxicity assays showed that the material in the short-term was non-cytotoxic. The results show that GeneO-Oleic acid-PEG had a better biocompatibility than GeneO-C(CH3)2-COOH.On the basis of the above study, three new types of polymer particles (PAA/GeneO-CH2-COOH, PAA/GeneO-C(CH3)2-COOH and PAA/GeneO-Oleic acid-PEG) were prepared by the biocompatible modified GeneO (GeneO-CH2-COOH, GeneO-C(CH3)2-COOH and GeneO-Oleic acid-PEG) and acrylic acid. We used particle size analysis, the Zeta potential testing and transmission electron microscopy to study self-assembly behavior under different pH conditions. The particle size and morphology of synthesized materials prepared by GeneO-CH2-COOH, GeneO-C(CH3)2-COOH, GeneO-Oleic acid-PEG and acrylic acid in the solution with different pH were different. The particle size of the materials prepared by GeneO-CH2-COOH, GeneO-C(CH3)2-COOH and acrylic acid at different pH were decreased with the increasing pH values (4110nm-75nm,7230nm-515nm, respectively), while the particle size of the materials prepared by GeneO-oleic acid-PEG and acrylic acid was increased with the increasing pH values (100nm～1110nm). Three synthetic material particle size changes were also consistent with the TEM results.In this thesis, studies had shown that the biocompatibility of three modified GeneO was GeneO-Oleic acid-PEG> GeneO-C(CH3)2-COOH> GeneO-CH2-COOH, and its hydrophilicity was proportional to its biocompatibility, the antimicrobial properties against E. coli was GeneO-Oleic acid-PEG> GeneO-C(CH3)2-COOH> GeneO-CH2-COOH, antibacterial performance against Staphylococcus aureus was GeneO-Oleic acid-PEG> GeneO-CH2-COOH> GeneO-C(CH3)2-COOH, modified GeneO can be able to enhance the adhesion and proliferation of HEK293cells, which indicated that they had potential applications in the field of biological applications. And synthesized PAA/modified GeneO nano complex had self-assembly behavior under different pH conditions and had different size and morphology in different pH solutions, which meaned that they had potential applications in drug carriers or pH stimulus and response.