Reversible Electrochemical Modulation of a Catalytic Nanosystem

Abstract

A catalytic system based on monolayer-functionalized gold nanoparticles (Au NPs) that can be electrochemically modulated and reversibly activated is reported. The catalytic activity relies on the presence of metal ions (Cd 2+ and Cu 2+ ), which can be complexed by the nanoparticle-bound monolayer. This activates the system towards the catalytic cleavage of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNPP), which can be monitored by UV/Vis spectroscopy. It is shown that Cu 2+ metal ions can be delivered to the system by applying an oxidative potential to an electrode on which Cu 0 was deposited. By exploiting the different affinity of Cd 2+ and Cu 2+ ions for the monolayer, it was also possible to upregulate the catalytic activity after releasing Cu 2+ from an electrode into a solution containing Cd 2+ . Finally, it is shown that the activity of this supramolecular nanosystem can be reversibly switched on or off by oxidizing/reducing Cu/Cu 2+ ions under controlled conditions. Complexityisemergingasamajorthemeinchemistry. [1] Notonly does it mark a shift from the study of relatively simple molecules to complex molecular structures similar to those found in nature, but it also marks a shift from the study of single molecules to networks of molecules. [2][3][4] Within the subfield of catalysis, [5] the emergence of nanozymes, defined as nanomaterials with enzyme-like activity, nicely illustrates this development. [6] Nanozymes are prepared following a bottom-up strategy relying on the use of simple synthetic components for the formation of structures with a size and structural complexity similar to that of enzymes. [7,8] Their high stability, uniformity, and ease of modification is favoring applications in the fields of sensing, [9] materials science, [10] and systems chemistry. [11] The observation that nanozymes can exhibit an emerging property such as cooperativity is indeed a sign that significant progress has been made in the design of functional complex systems. [12] However, whereas nature has gained exquisite control over the complex biological machinery by using specific triggers to up-and down-regulate catalytic processes, similar regulatory pathways are still largely inexistent for nanozymes. Herein, we present a simple setup for the reversible activation and modulation of nanozymes using an electronic input. The electrochemical activation is highly attractive because of its ease of implementation, cleanliness, precision, and rapid response. [13][14][15][16] The availability of this kind of regulatory mechanism will strongly determine the success of chemists in constructing synthetic networks for studying complexity on the systems level.The main component of our system is Au NP 1, which are gold nanoparticles (d = 1.5 AE 0.3 nm) covered with C9-thiols terminating with a 1,4,7-triazacyclononane (TACN) head group (Figure 1 a). [11] Such nanoparticle-bound TACN moieties are able to coordinate Zn 2+ -metal ions forming a supra-

Gold Nanozymes: From Concept to Biomedical Applications

“…Lastly, gold nanozymes have proved useful beyond diagnosis and treatment possibilities. Many studies have already shown some potential bioapplications in diverse fields worth mentioning, either for building artificial biochemical models [ 213 , 214 ] or for implementing chemical catalysis [ 215 , 216 ]. Regarding biochemical models, two of them have been developed using gold nanozymes with different applicabilities.…”

“…However, many of these examples use AuNPs as scaffolds in which the catalysts are immobilized. Metallic ions are commonly used for this purpose, such as Cd 2+ and Cu 2+ [ 216 ] or Ru [ 215 ]. These models follow the traditional nanozyme definition, coined by Scrimin’s group [ 76 ], and referring to the combination of nanomaterials and catalysts, with no evaluation of the functionality of the nanomaterial itself as catalyst.…”

“…These models follow the traditional nanozyme definition, coined by Scrimin’s group [ 76 ], and referring to the combination of nanomaterials and catalysts, with no evaluation of the functionality of the nanomaterial itself as catalyst. The first nanosystem catalyses the cleavage of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNPP) [ 216 ] and demonstrates that the activity of this supramolecular catalyst can be electrochemically regulated by releasing metallic cations from an electrode or by re-depositing these ions on the electrode (Fig. 14 a).…”

Reversible Deactivation Radical Polymerization: State-of-the-Art in 2017

“…An important progress in RDRP has been achieved in polymer synthesis mediated by external stimuli including applied current (41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55). Light (56)(57)(58), mechanical force (59)(60)(61)(62), and chemical redox triggers (63)(64)(65)(66) to enable spatial, temporal, and sequence control.…”

Toward supramolecular nanozymes for the photocatalytic activation of Pt(iv) anticancer prodrugs

“…While these key aspects are worth exploring in the future, the results described here highlight that TACN AuNPs are suitable components to develop supramolecular nanomaterials capable to carry out unconventional flavinmediated catalytic reactions using Pt(IV) prodrugs as substrates. Besides extending the repertoire of reactions catalyzed by TACN-based nanoparticles, [31][32][33] this work holds promise as strategy to control spatio-temporally the effects of Pt anticancer drugs via light activation and catalytic amplification.…”