中文摘要：

目的：研究表面修饰对氧化铁纳米粒子类酶活性的影响。方法：用共沉淀法制备γ-Fe2O3纳米粒子,并用透射电子显微镜（TEM）表征。将γ-Fe2O3纳米粒子分别表面修饰二巯基丁二酸（DMSA）、柠檬酸、酒石酸和3-氨丙基三乙氧基硅烷（APTS）,并用Zeta电位仪表征。由于γ-Fe2O3纳米粒子可以催化双氧水氧化底物3,3′,5,5′-四甲基联苯胺（TMB）,从而发生显色反应,这一特性与辣根过氧化物酶（HRP）相似,通过岛津UV-3600紫外-可见分光光度计和酶标仪检测该显色反应,评估氧化铁纳米粒子的催化性能及表面修饰的影响。结果：（1）TEM和Zeta电位测量表明,γ-Fe2O3纳米粒子直径约为13 nm,表面修饰能够有效调控其表面电荷;（2）氧化铁纳米粒子类过氧化物酶催化活性与纳米粒子的表面电荷相关,表面负电荷有利于增加对带正电荷底物TMB的亲和力,从而增加类酶活性;（3）γ-Fe2O3/DMSA具有最高的表面负电荷,米氏常数测量表明Km（TMB）为0.3 mmol·L^-1,表现出与天然HRP对底物TMB类似的亲和力。结论：通过表面修饰可以调控氧化铁纳米粒子的类酶活性,其作为HRP模拟酶具有潜在的应用价值。

英文摘要：

Objective：To investigate the effect of surface modifications on the peroxidase-like activity of iron oxide nanoparticles.Methods：Magnetic iron oxide nanoparticles were prepared by co-precipitation method.The morphology of particles was observed by using TEM.The obtained γ-Fe2O3 nanoparticles were modified with meso-2,3-Dimercaptosuccinic acid（DMSA）,citric acid,tartaric acid and 3-aminopropyltriethoxysilanes（APTS）,respectively,and the resultant products were characterized by zeta potential measurements.Like horseradish peroxidase（HRP）,γ-Fe2O3 nanoparticles were found to be able to catalyze a colour reaction of the substrate 3,3′,5,5′-tetramethylbenzidine（TMB） in the presence of H2O2.The catalysis was evaluated by detecting the colour reaction using UV-visible spectrophotometer and microplat reader.Results：（1） TEM measurements showed that the mean diameter of γ-Fe2O3 nanoparticles was 13 nm.（2） The peroxidase-like activity of γ-Fe2O3 nanoparticles was found to be related to their surface charge.TMB carries two amine groups,likely yielding stronger affinity toward a negatively charged nanoparticle surfaces.（3）γ-Fe2O3/DMSA nanoparticles with the strongest negative surface charge exhibited the highest peroxidase-like activity than others when TMB acts as a substrate.The kinetic parameter of γ-Fe2O3/DMSA nanoparticles were determined to be Km（TMB）=0.3 mmol·L^-1,exhibiting a similar enzyme activity to the natural HRP.Conclusions：The peroxidase-like activity of γ-Fe2O3 nanoparticles can be readily regulated by surface modifications,thus providing a potential advantage for application as a HRP mimic enzyme.