Ionic Functionalization of Hydrophobic Colloidal Nanoparticles To Form Ionic Nanoparticles with Enzymelike Properties

Abstract

Inorganic colloidal nanoparticles (NPs) stabilized by a layer of hydrophobic surfactant on their surfaces have poor solubility in the aqueous phase, thus limiting their application as biosensors under physiological conditions. Here we report a simple model to ionize various types of hydrophobic colloidal NPs, including FePt, cubic Fe3O4, Pd, CdSe, and NaYF4 (Yb 30%, Er 2%, Nd 1%) NPs, to multicharged (positive and negative) NPs via ligand exchange. Surfaces of neutral hydrophobic NPs were converted to multicharged ions, thus making them soluble in water. Furthermore, peroxidase-like activity was observed for ionic FePt, Fe3O4, Pd, and CdSe NPs, of which FePt and CdSe catalyzed the oxidation of the colorless substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to the blue-colored product in the absence of H2O2, while Pd and Fe3O4 catalyzed the oxidization of TMB in the presence of H2O2. With the benefit of the ionic functionalization protocols described herein, colloidal NPs should gain wider use as biomarkers, nanozymes, and biosensors.

Growth of Au Nanoparticles on 2D Metalloporphyrinic Metal‐Organic Framework Nanosheets Used as Biomimetic Catalysts for Cascade Reactions

“…TEM images (Figure 2c,d and Figure S8, Supporting Information) reveal that Au NPs with size of 2.2 ± 0.6 nm are deposited on the surface of Cu-TCPP(Co) nanosheets. In a typical experiment, 3,3′,5,5′-tetramethylbenzidine (TMB), which was widely used to evaluate the catalytic performance of enzyme mimic, [32] was used as substrate to test the peroxidase-like catalytic activity of Au NPs/Cu-TCPP(M) hybrid nanosheets. In order to prove it, the peroxidase-like catalytic activity of Au NPs/Cu-TCPP(M) hybrid nanosheets was first studied.…”

Iron oxide nanozyme catalyzed synthesis of fluorescent polydopamine for light-up Zn2+detection

“…6 In general, dopamine has strong affinity to many surfaces, 2 and it can even stabilize iron oxide NPs. 33 To test whether a surface coating is formed in our system, we examined the recycling ability of Fe3O4 NPs in producing FPD. The fluorescence intensity of the oxidization products after ten reaction cycles still remained 90% of the value of the fresh Fe3O4 NPs ( Figure 3A).…”

Fluorescein as a Visible‐Light‐Induced Oxidase Mimic for Signal‐Amplified Colorimetric Assay of Carboxylesterase by an Enzymatic Cascade Reaction

“…horseradish peroxidase, HRP), such as high cost in large‐scale production, poor stability of catalytic activities against denaturation, digestion, or the variations of environmental conditions, researchers have, therefore, endeavoured to develop artificial enzymes, such as nanozymes, metal‐organic frameworks, and small‐molecule‐based mimic peroxidises, as viable alternatives. Although these artificial peroxidases exhibit some advantages over HRP, for example, low in cost, easy to prepare, high stability, and so on, most of them need destructive and unstable H 2 O 2 as an oxidant to obtain high catalytic activity, which may become an obstacle to further applications. More significantly, owing to a lack of simple, green, and cost‐effective means to modulate the catalytic activity of nanozymes, it is highly desirable to exploit a new class of enzyme mimics, the activities of which can be easily modulated without the aid of H 2 O 2 .…”