title: In situ nanoplasmonic probing of enzymatic activity of monolayer-confined glucose oxidase on colloidal nanoparticles.
abstract: In situ probing protein-particle interactions and activities of proteins on colloidal nanoparticle (NP) surfaces is a long-standing key challenge in understanding the nanobio interfaces and virtually important for a variety of biological and biomedical applications. The interactions of NPs with proteins, for instance, are known to form NP bioconjugates or protein coronas; protein surface immobilization and molecular layer-by-layer deposition techniques are widely used, but a clear understanding of the confinement effect on protein activity by molecular coating, at the monolayer level, remains poorly understood. We explore here a novel approach, using colloidal plasmonic nanocomplexes coated with glucose oxidase (GOx) as self-sensing nanoprobes for in situ optical probing of surface-confined enzymatic activity, which is at least 1-2 orders of magnitude more sensitive than standard colorimetric assays for detecting GOx activity. We found that enzymatic activity of monolayer-confined GOx on colloidal NPs was significantly enhanced as compared with free GOx (also proved by conformational changes from circular dichroism studies), with a low apparent Michaelis-Menten constant Km of ~0.115 mM and high turnover kcat/Km of ~8394 M(-1)·s(-1); compared with the "anchored-type" suspending GOx, the outmost polyelectrolyte monolayer-protected "sandwiched-type" GOx exhibits significantly improved enzymatic activities toward higher temperatures and wider pH range. This finding is of fundamental important and instructive for safe use of such nanomaterials for bioapplications.
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin, P R China.
authors.forename: Haili
authors.initials: H
authors.lastname: He
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Xu
authors.forename: Haoxi
authors.initials: H
authors.lastname: Wu
authors.forename: Yujuan
authors.initials: Y
authors.lastname: Zhai
authors.forename: Yongdong
authors.initials: Y
authors.lastname: Jin
mesh_terms: D003102:Colloids / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation; D005949:Glucose Oxidase / Q000737:chemistry / Q000378:metabolism*; D006046:Gold / Q000737:chemistry* / Q000378:metabolism; D053768:Metal Nanoparticles / Q000737:chemistry*; D012834:Silver / Q000737:chemistry* / Q000378:metabolism; D013499:Surface Properties
chemical_list: D003102:Colloids; D012834:Silver; D006046:Gold; D005949:Glucose Oxidase