A Facile Approach For Fabrication Of Core-shell Magnetic Molecularly Imprinted Nanospheres Towards Hypericin

As the main biocomponent of hypericum perforatum,hypericin has attracted increasing attention due to its pharmacological activities such as anti-bacterial anti-inflammatory,antidepressant,anti-virus,anti-cancer,etc..However,the content of hypericin in hypericum perforatum is very low,resulting in difficulty in extracting from plants and low extraction efficiency.Molecularly imprinted polymer technology is one of the effective ways to solve the problem of hypericin extraction because of its ability to give material specific identification and adsorption ability to specific molecules.Based on this,we adopted Fe3O4 as matrix,dopamine as functional monomer and crosslinker,to form a core-shell structure of the surface molecular imprinted polymer nanospheres in the presence of hypericin(Fe3O4@PDA/Hyp),via the oxidation self-polymerization of dopamine.In this paper,the fabricated core-shell magnetic nanospheres(including magnetic nanospheres,hypericin imprinted and non-imprinted magnetic nanospheres)were frist characterized by FTIR,TEM,DLS,Zeta potential and BET.The results showed that dopamine formed polydopamine(PDA)film with a thickness between 23 and 29 nm on the surface of magnetic sphere.The synthesis conditions of the hypericin magnetic nanoparticles(Fe3O4@PDA/Hyp)on the imprinting effect were studied.The conditions included the concentration of dopamine,the amount of acetone,the ratio of the template molecule to the functional monomer,the reaction temperature,the pH of the reaction medium,the adding orders of the reactants and the post-treatment with ethanolamine.By comparing adsorption capacity of hypericin of Fe3O4@PDA/Hyp nanospheres prepared in different conditions,the optimal conditions were obtained: at room temperature,hypericin is first added to a suspension of the matrix beads,followed by addition of dopamine with a concentration of dopamine at 2 mg/mL,the volume ratio of acetone to Tris-HCl is 1:6,the molar ratio of hypericin to dopamine was 1:122 and the pH of the solution is 8.0.Finally,the prepared nanospheres were treated with ethanolamine to obtain the final Fe3O4@PDA/Hyp with an adsorption capacity of 18.28 mg/g for hypericin.The specific recognition of Fe3O4@PDA/Hyp was studied by using protohypericin and emodin as the structural analogues of hypericin.It was found that the selection factor SF of protohypericin and emodin was 1.92 and 3.55,respectively;the imprinting factor IF of hypericin,protohypericin and emodin was 8.01,3.07 and 1.36,respectively.The adsorption kinetics of the nanospheres showed that the adsorption of hypericin was in accordance with the Langmuir adsorption model.The preliminary pratical study showed that Fe3O4@PDA/Hyp magnetic nanospheres prepared by this work have good selectivity and adsorption ability for hypericin in the extract of hypericum perforatum.The method developed in the thesis for fabrication of Fe3O4@PDA/Hyp magnetic nanospheres has a good selectivity for adsorption of hypericin,and is expected to be used as an adsorption material for hypericin enrichment and separation.