Preparation And Adsorption Properties Of Curcumin Molecularly Imprinted Polymers

Molecular imprinting technology(MIT)is a highly selective separation and molecular recognition technology developed rapidly recently.Because of its strong ability to resist bad environment,high selectivity,good stability,high mechanical strength,simple preparation process and other advantages,MIT is widely used for separation,purification and concentration of active ingredients in natural products.As the main active ingredient in turmeric,curcumin is a natural pigment of special structures with two ketones and polyphenols.Curcumin has good physiological functions which shows obvious effect on the treatment of cancer and tumors.Nowadays,there are certain disadvantages on domestic and international technology process in the extraction and purification of curcumin.As a result,how to separate,purify and concentrate curcumin efficiently from complex natural products has great research significance and social market value.In this paper,curcumin molecularly imprinted polymer(MIP)were prepared by molecular imprinting technique.The main research contents and conclusions are as follows:1.Reaction mechanism of a series of assembling system formed by curcumin as template molecule,methacrylic acid,methyl methacrylate,acrylamide and 4-vinyl pyridine as functional monomer,methanol,acetonitrile,ethyl acetate,acetone and tetrahydrofuran as solvent was studied by ultraviolet spectrometry and differential ultraviolet spectrometry.In terms of theory,the best functional monomer was determined to methacrylic acid and the best optimal reaction ratio of curcumin and methyl acrylic acid was 1:4.At the same time,methanol,acetone and acetonitrile were the right reaction solvents in theory.2.The curcumin molecularly imprinted polymer was prepared by bulk polymerization using curcumin as template molecule,ethylene glycol dimethacrylate as cross-linker and azobisisobutyronitrile as initiator under the optimized conditions.The results showed that MIP had the best stability and identification toward curcumin by choosing methacrylic acid as functional monomer and acetone as solvent with the optimized ratio be n(CUR):n(MAA):n(EDMA)=1:4:20.Its imprinting factor was 1.27.Infrared spectrum analysis indicated that the curcumin in the MIP was completely washed and there was hydrogen bonding between the template molecule and functional monomer;Scanning electron microscopy analysis indicated that MIP had hole structures;Thermogravimetric analysis indicated that the thermal stability of MIP was good which could be used in high temperature conditions.Adsorption kinetics and thermodynamic studies of the curcumin molecularly imprinted polymer showed that its adsorption accorded with process pseudo-second-order kinetic model y=3.6848x+8.9290(R2=0.9992);Scatchard equation indicated that MIP formed two different types of binding sites.Equilibrium dissociation constant were Kd=3.306mg/L and Kd=0.177mg/L,respectively and maximum apparent adsorption quantity were Qmax=3.617mg/g and Qmax=0.781mg/g,respectively;Selective adsorption study showed that adsorption quantity of MIP toward curcumin is muchhigher than ferulic acid and quercetin which showed the strong selective adsorption ability to template molecule.3.The curcumin molecularly imprinted polymer microspheres were prepared by precipitation polymerization.The effects of solvent dosage,mixed solvent ratio and template molecular weight on the apparent morphology of curcumin molecularly imprinted polymer microspheres were investigated.The optimal preparation conditions were as follows: 50 mL acetonitrile and 20 mL methanol as mixed solvent,1.0mmol curcumin as a template molecule,4.0mmol of methacrylic acid as a functional monomer.Infrared spectrum analysis indicated that there was hydrogen bonding when Curcumin was saturated with MIP;Thermogravimetric analysis indicated that the thermal stability of MIP was good which could be used in high temperature conditions.Adsorption kinetics and thermodynamic studies of the curcumin molecularly imprinted polymer microsphere showed that adsorption capacity of MIP toward curcumin was obviously higher than that of NIP.Its adsorption accorded with process pseudo-second-order kinetic model y=1.8800x+1.6721(R2=0.9999);Scatchard equation indicated that two different types of binding sites exist in the MIP.Equilibrium dissociation constant were Kd=4.065mg/L and Kd=0.144mg/L,respectively and maximum apparent adsorption quantity were Qmax=5.077mg/g and Qmax=0.913mg/g,respectively;Selective adsorption study showed that,compared with ferulic acid and quercetin which have similar structures,polymer microspheres toward curcumin had strong selective adsorption ability.