Core-shell Au@Co-Fe hybrid nanoparticles as peroxidase mimetic nanozyme for antibacterial application

Nanozymes have been developed as alternative for enzymes to overcome practical limitations of enzymes in industry and medicine. Infectious diseases are becoming severe threat to public health. Hence, peroxidase nanozyme for combating bacteria have been designed. Core-Shell Au@Co-Fe hybrid nanoparticles (Au@Co-Fe NPs) were synthesized. The structure of Au@Co-Fe NPs was characterized by UV–vis and FT-IR spectroscopic methods. The size, zeta potential and spherical morphology of Au@Co-Fe NPs were determined by DLS, TEM and AFM techniques. Au@Co-Fe NPs has been evaluated as peroxidase mimic nanozyme. The peroxidase mimetic activity of gold nanoparticles, Co (II) and Fe (III) were measured and compared with that obtained for native HRP. The enzymatic measured activity was 50% of native horse radish peroxidase. Additionally, Au@Co-Fe NPs was evaluated as antibacterial agent against four selected standard pathogenic bacteria as Escherichia coli, Pseudomonas aeruginosa (as gram negative) and Staphylococcus aureus, and Bacillus cereus (as gram positive).     

Albumin coated copper-cysteine nanozyme for reducing oxidative stress induced during sperm cryopreservation

In the present work, SOD mimetic nanozyme (NACu-Cys) consisting of Cu-Cys complex and nano-albumin (NA) were synthesized. After characterizing the nanozyme, its superoxide dismutase (SOD) behavior was evaluated by inhibition of the pyrogallol autoxidation method. The results revealed that NACu-Cys exhibited SOD mimetic activity with a half inhibition concentration (IC₅₀) value of 7.0 × 10⁻³ µM and a turnover number (k_cat) of 5.4 × 10⁷ s⁻¹. In the next step, this nanozyme was applied as a protective agent against oxidative stress induced by sperm cryopreservation. Increasing the motility, raising the viability and reducing the apoptosis occurred as a result of NACu-Cys additions to human sperm freezing medium. Comparison between the natural SOD and SOD mimic behavior of NACu-Cys revealed that this nanoparticle has the ability to be used as oxidative stress decrescent during cryopreservation process.     

Self-assembled gold nanocrystal micelles act as an excellent artificial nanozyme with ribonuclease activity

Abstract  Water-soluble Au nanocrystal (NC) micelles with an inserted catalytic Cu(II) center that act as excellent nanoenzyme models for imitating ribonuclease were constructed by supramolecular self-assembly. The dodecane-1-thiol-based Au NC was constructed first, and subsequently the cationic surfactant hexadecyltrimethylammonium bromide and the catalytic ligand (N ¹,N ¹-bis(2-aminoethyl)-N ²-dodecylethane-1,2-diamine) copper(II) were installed on the surface of the Au NC via hydrophobic interaction. The catalytic capability of the Au NC micelles designed was estimated by the cleavage of a typical RNA analogue, 2-hydroxypropyl p-nitrophenyl phosphate (HPNP). The study of the catalytic behavior of Au NC micelle catalysis showed that the Au NC micelles exhibited dramatic ribonuclease-like activity: a high rate acceleration of k _cat/k _uncat = 1.10 × 10⁵ for the cleavage of HPNP in comparison with the spontaneous cleavage of HPNP (k _uncat) was observed. The catalytic capability for HPNP cleavage by these functionalized Au NC micelles can be compared with that of covalent Au nanoparticles reported previously as nanozymes under comparable conditions. A detailed investigation of enzymatic kinetics was carried out and a possible mechanism was suggested. Graphical abstract        

A natural nanozyme in life is found: the iron core within ferritin shows superoxide dismutase catalytic activity

Science China Life Sciences -     

A colorimetric detection of dopamine in urine and serum based on the CeO2@ZIF-8/Cu-CDs laccase-like nanozyme activity

This study reports a sensitive and selective colorimetric approach for the analysis of dopamine (DA) based on CeO₂@ZIF-8/Cu-CDs laccase-like nanozymes activity. The CeO₂@ZIF-8/Cu-CDs was synthesized using cerium oxide (CeO₂) and copper-doped carbon dots (Cu-CDs) with 2-methylimidazole by a facilely hydrothermal approach. The CeO₂@ZIF-8/Cu-CDs exhibited excellent laccase-like nanozymes activity and can oxidize the colorless substrate (DA) to red product with 4-aminoantipyrine as the chromogenic agent. The Michaelis–Menten constant (K_m) and the maximal velocity (V_max) of CeO₂@ZIF-8/Cu-CDs are 0.20 mM and 1.48 μM/min, respectively. The detection method has a linear range of 0.05–7.5 μg/mL and a detection limit as low as 8.5 ng/mL with good reproducibility. The developed colorimetric sensor was applied to rapid and precise quantitative evaluation of DA levels in serum and urine samples. This study presents a new approach for detecting biological molecules by utilizing the controlled regulation of nanozymes' laccase-like activity.