Manganese ferrite graphene nanohybrid synthesis and the investigation of its antibacterial properties

摘要

Introduction: Graphene oxide (GO) is a monolayer of carbon atoms that form dense honeycomb structure with unique properties. Hence, GO and its composites have a wide range of potential applications on nanoelectronics, transparent conductors, polymer reinforcement, bioengineehng and biomaterials areas.Recent research demonstrated that GO is a relative biocompatible material, and has antibacterial ability with mild cytotoxicity.Furthermore, due to the existence of assorted oxygen containing groups on the GO surface, its properties can be adjusted for various biomedical applications. Several approaches for the modification of biomaterials have been developed to confer antibacterial properties, and they have great importance in the development of self-disinfecting surfaces13'. Thus in this work, it was developed a manganese ferrite graphene nanohybrid followed by its antibacterial properties investigation. Materials and Methods: GO was synthesized according to the modified Hummers method.The preparation of MnFe_2O_4-G was based on a facile one-pot solvothermal method. In short, ethylene glycol, GO, ferric chloride, manganese chloride was dispersed under ultrasonication. Later, sodium acetate was added and stirred for 30 min. The mixture was then autoclaved at 200°C for 10 h. The obtained mixture was then washed several times by deionized water and ethanol and dried in hot air oven at 60°C. Bare MnFe_2O_4 nanoparticles was prepared by a similar approach but in the absence of GO. The antibacterial properties of the nanohybrids were tested by an adapted technique proposed by Chella et al. (2015), 10 mg of nanohybrids were added to 100 ml of artificialy contamined water (Escherichia coli ATCC11229) with an approximate concentration of 1×10~5 CFU mL~(-1). After 8 h of contact time, the antibacterial effect was evaluated by the membrane filtration technique according to Standard Methods for the Examination for Water and Wastewater. Results and Discussion: The results for the evaluation of antibacterial properties of the graphene oxide, MnFe_2O_4 and MnFe_2O_4-G are presented in the figure below. Figure 1 - Cell viability measurement after incubation with GO, MnFe_2O_4 and MnFe_2O_4-G dispersions after 8h of contact time. The material composed of bare nanoparticles showed lower removal when compared with the nanohybrids, presenting 89.50% of bacterial viability loss. Graphene oxide exhibited 62.63% of cell inactivation and showed moderate cytotoxicity, while the nanohybrids presented 91.91 % of cell inactivaction. This result suggests that graphene oxide also induced £ coli death. Chella et al. (2015) found a similar behavior. They found that both, the oxidation stress and the contact with the membrane, contributed to the antibacterial activity of graphene materials.The antibacterial activity mechanism was accomplished by binding the hybrid composite with the Exoli cell wall. The complete cell wall break occurred by direct contact through the graphene nanosheets, which induced stress to the membrane and disturbed the cell structure, leading the bacterial cells to death. Materials based on graphene, which contain a great number of functional groups, are likely to interact with bacterial cell structures, resulting in damage and their death. Conclusion: The manganese ferrite graphene nanohybrid synthesized in this research presented higher antibacterial activity when compared to graphene oxide and bare MnFe_2O_4 nanoparticles. Therefore, the nanohybrid has an important potential for antibacterial purposes.