Graphene Oxide-Fe(?) Complex Coated Molecularly Imprinted Polymer:Articial Cytochrome C Mimics For Bioremediation

The water pollution is a serious problem nowadays.The pollution of environmental water is mainly from industrial,agricultural and domestic pollutants.The pollution of environmental water results in serious damage to human beings.Therefore,development of new methods for removal of pollutants in environmental water is urgent needed.Cytochrome c?Cyt c?is an electron transport protein containing a porphyrin group and is very important in physiological functions in respiration.Because of the transmition of electrons through iron in the porphyrin group and specific recognition for target pollutant,Cyt c and bacteria containing Cyt c show great potential for the bioremediation of environmental water.Because of the susceptible and unstable of biological treatment methods,an artificial Cyt c mimic material is necessary to be prepared.Molecularly imprinted polymer?MIP?is a material known as"artificial antibody",which possesses specific recognition and binding property just like antigen-antibody binding.Because of its easy synthesis,high selectivity and good stability,MIP is widely used to prepare the artificial enzyme materials with catalytic properties like natural enzymes.Therefore,the artificial enzyme materials have been widely used to remove contaminants in environmental water.In this study,a Cyt c mimic material was obtained by molecular imprinting technology.This material showed good properties of stability,specific recognition and electron transport.The Cyt c mimic material was applied to remove the contaminants in environmental water,and the efficiency and mechanism were also studied.Objective:The Cyt c mimic material was prepared by molecular imprinting technique,and the obtained material had the specific recognition and electron transport properties of Cyt c,and the stability of MIP.The Cyt c mimic material could be used to remove the contaminants from environmental water effectively.Methods:First,the graphene oxide?GO?coated Cr?VI?ion imprinted polymer?IIP?was obtained by Pickering emulsion system stabilized with GO as stabilizers.The morphology and adsorption properties of IIP were evaluated.The IIP provided the specific recognition sites for the Cyt c mimic material.After that,the Cyt c mimic material was prepared by constructing GO-Fe?III?complex on the surface of IIP.The GO-Fe?III?complex was formed on the surface of IIP by mixing the Fe?III?with IIP.The Cyt c mimic material could provide electrons to the Fe?III?under illumination,then the Fe?III?was reduced to Fe?II?and Fe?II?could reduce the adsorbed Cr?VI?to Cr?III?.The photocatalytic reduction property of Cyt c mimic material was evaluated and the detoxification performance of the Cyt c mimic material was evaluated by cytotoxicity experiment.At last,the Cyt c mimic material was used to selective photocatalytic reduce pentavalent vanadium?V?V??and nitrobenzene?NB?.Result:?1?The Cr?VI?,2-VP,TRIM and EGDMA,toluene were used as the template,momoner,crosslinker and porogen,respectively.The oil phase was composed with monomer,crosslinker and porogen.The water phase was composed with GO solution.The IIP was successfully prepared by Pickering emulsion stabilized with GO as stabilizers.According to optical microscopy,the IIP was a regular sphere with a diameter of 76.5±8.4?m.Scanning electron microscopy?SEM?showed that GO was coated on the IIP surface.Thermodynamic adsorption results showed that the maximum adsorption capacity q_max(0.68 mg g^-1)of IIP was significantly higher than q_maxof non-imprinted polymer?NIP?(0.43 mg g^-1).Kinetic adsorption studies showed that the adsorption equilibrium time of Cyt c mimic material was only 30minutes.These all indicated that the IIP could recognize and bind Cr?VI?selectively and effectively.Interference experiments showed that Cr?III?,Fe?III?,Fe?II?and Cu?II?had no obvious inhibitory effect.The IIP still had good selective adsorption property after 5 cycles and this indicated that IIP has good stability.?2?The Cyt c mimic material was prepared with constructing GO-Fe?III?complex on the surface of IIP by mixing the Fe?III?with IIP.The material could reduce Cr?VI?under illumination in pH4 solution.The reference experiments showed that illumination,imprinted cavities,GO,and Fe?III?played important roles in the photocatalytic reduction process.The study of Michaelis-Menten model showed that the material could be used as an artificial enzyme for catalyze Cr?VI?,the Michaelis-Menten constant K_m of IIP was 46%for that of NIP?The smaller of K_m,the better of the enzyme catalytic ablity?.Interference experiments showed that H₂PO₄^-has an obvious inhibitory effect on the catalysis of IIP,which was due to the structural analog to Cr?VI?.The CH₃COO^-was not similar to Cr?VI?,so it has no effect on the catalysis of IIP.This indicated that the IIP has good selective bind property for target substance.Mechanism studies showed that GO was oxidized,providing electrons to Fe?III?under illumination,then the Fe?III?was reduced to Fe?II?and Fe?II?could reduce the adsorbed Cr?VI?to Cr?III?.After reducing,the Fe and Cr were adsorbed on the surface of IIP formed as a hydrate.Therefore,the Cyt c mimic material was successfully prepared and the material could photocatalytic reduce Cr?VI?effectively,and the reduction product Cr?III?was adsorbed on the surface of the material.?3?The IIP and Cyt c mimic material were used to treat Cr?VI?solution respectively and the cytotoxicity experiment was used to evaluate the toxicity of the Cr?VI?solution after treatment.It could adsorb Cr?VI?effectively through many times of adsorption,to make the treated solution was almost non-cytotoxic.The L02 cells were cultured with Cr?VI?solution treated by IIP for 10 times?10 mg polymers per time?,and about 93%of the cells still had viability.The adsorption of Cr?VI?was weak treated with different weights of IIP,and this method could not neutralize the toxicity of Cr?VI?effectively.The other adsorption method was not effective to neutralize the toxicity of Cr?VI?.The adsorption method is very cumbro to remove Cr?VI?,therefore it is necessary to develop an adsorption-degradation catalyst for Cr?VI?.The study showed that Cyt c mimic material could neutralize the Cr?VI?toxicity effectively.With the increase of illumination time,the concentration of Cr?VI?was decreased gradually,and the HepG2 cells cultured with the Cr?VI?solution treated by IIP?for 420 min illumination?were about 85%still alive.The double staining results of Hoechst 33342 and PI also showed that the HepG2 cells cultured with treated Cr?VI?still had a good alive state,and the Cyt c mimic material could neutralize the toxicity of Cr?VI?effectively.?4?The pentavalent vanadium?V?V??and nitrobenzene?NB?were selected to photocatalytic reduce by the Cyt c mimic material.The structural analog molecularly imprinted polymer?SA-MIP?of V?V?showed high affinity to V?V?.Thermodynamic adsorption results showed that the maximum adsorption capacity q_maxof SA-MIP was 5.44 mg g^-1,which was 1.3 times to the structural analog non-imprinted polymer?SA-NIP?.Kinetic adsorption studies showed that the equilibrium adsorption time of SA-MIP was only 30 minutes.Photocatalytic data showed that the V?V?was significantly reduced within 30 minutes,but the concentration of V?V?in solution was not significantly changed with the increase of illumination.This may be due to the reduction was occurred on the V?V?which was absorbed by SA-MIP.The transition state analogue molecularly imprinted polymer?TSA-MIP?of NB showed a good adsorption to NB.The photocatalytic data showed that the TSA-MIP could effectively reduce NB,and the apparent rate constant(4.2×10^-3 min^-1)was 1.2 times to the value(3.5×10^-3 min^-1)of the transition state analogue non-imprinted polymer?TSA-NIP?.The fluorescein isothiocyanate?FITC?was used to label the TSA-MIP and TSA-NIP,the results showed that NB was reduced to aniline during the catalytic process,and the aniline was also adsorbed on the surface of MIP.These results showed that the Cyt c mimic material was not only useful to selective reduce Cr?VI?,but also suitable for the reduction of V?V?and NB.This also indicated that the Cyt c mimic material could be used to remove pollutants in the environment water effectively.Conclusion:The IIP with good stability,strong adsorption capacity and strong anti-interference ability was easy synthesized by Pickering emulsion stabilized with GO.The Cyt c mimic material was easy prepared with constructing GO-Fe?III?complex on the surface of IIP by mixing the Fe?III?with IIP.The material could catalytic reduce the Cr?VI?effectively and the Cr?VI?solution after treatment had no toxicity to cells.The material showed good selectivity and catalytic reduction property towards the V?V?and NB.These demonstrated that the Cyt c mimic material was useful to selectively remove pollutants in the environment effectively.This Cyt c mimic material could provide a new method and idea for the selective photocatalytic reducation of pollutants.