L-Cysteine as an Irreversible Inhibitor of the Peroxidase-Mimic Catalytic Activity of 2-Dimensional Ni-Based Nanozymes

Abstract

The ability to modulate the catalytic activity of inorganic nanozymes is of high interest. In particular, understanding the interactions of inhibitor molecules with nanozymes can bring them one step closer to the natural enzymes and has thus started to attract intense interest. To date, a few reversible inhibitors of the nanozyme activity have been reported. However, there are no reports of irreversible inhibitor molecules that can permanently inhibit the activity of nanozymes. In the current work, we show the ability of L-cysteine to act as an irreversible inhibitor to permanently block the nanozyme activity of 2-dimensional (2D) NiO nanosheets. Determination of the steady state kinetic parameters allowed us to obtain mechanistic insights into the catalytic inhibition process. Further, based on the irreversible catalytic inhibition capability of L-cysteine, we demonstrate a highly specific sensor for the detection of this biologically important molecule.

π‐Conjugated Copper Phthalocyanine Nanoparticles as Highly Sensitive Sensor for Colorimetric Detection of Biomarkers

“…It has been reported that L‐cysteine can inhibit the enzyme‐like activity of nanomaterials through the interaction of −SH with metal active centers, thus resulting in changes of oxTMB absorbance [44] . Based on this unique mechanism, diverse metal‐based POD‐like nanomaterials have been designed to detect L‐cysteine [44,45] . Due to the excellent POD‐like activity of Cu‐PcCP NPs, the catalytic sensing of L‐cysteine is carefully investigated via TMB mediated POD‐like activity assay (Figure 7a).…”

“…[44] Based on this unique mechanism, diverse metal-based POD-like nanomaterials have been designed to detect L-cysteine. [44,45] Due to the excellent…”

Cobalt Sulfide Nanosheets as Peroxidase Mimics for Colorimetric Detection of l-Cysteine

“…Following the in-depth characterization of the Co 3 S 4 nanosheets, we first explored their ability to mimic the catalytic activity of the natural peroxidase enzyme. ,,,− For this, the ability of Co 3 S 4 nanosheets to convert the colorless diamine TMB to a blue colored charge transfer product (λ max at ca. 650 nm) was assessed following its incubation with peroxidase substrates TMB and H 2 O 2 . , As shown in Figure a, the Co 3 S 4 nanosheets could rapidly oxidize TMB in the presence of H 2 O 2 at initial time points with the activity saturating within 15 min of the reaction.…”

“…This reversible binding showed similarity to the enzymatic competitive inhibition process. Subsequently, our more recent work has shown that l -cysteine binds irreversibly to Ni-based NZs . This difference in the mechanism suggested that the composition of the NZ can have a major role in the ability of the NZ to interact with l -cysteine.…”

“…In the context of catalysis, enzyme-mimicking catalytic nanoparticles or nanozymes (NZs) have gained remarkable interest with wide-spread applicability across sensing, bioimaging, environmental clean-up, and pro-drug therapy. − Given that the composition of the nanoparticle can influence the catalytic efficiency, − a suite of nanoparticles including metals, metal oxides, metal sulfides, etc ., have been reported for wide-ranging enzyme-mimic activities. , Of these, metal sulfides have been suggested to be superior catalyst candidates as the M–S bonds are weaker than the M–O bonds in the corresponding metal oxides . Further, NZ-based sensors have gained attention in analytical science as they allow visual detection of the sensing event. , Such sensors have been used for the detection of several chemical and biological molecules including l -cysteine, a thiol containing semi-essential amino acid found in a number of proteins. , The detection of l -cysteine is important as its deficiency can cause anomalous cell growth, skin lesions, lethargy, hair depigmentation, liver damage, and malabsorption syndrome, while high levels of l -cysteine can be neurotoxic and cause cardiovascular diseases …”