Breaking through the pH Limitation of Fe1-xS Nanozymes Using Component-Modulated Coupled Nanoclay.

Overcoming the intrinsic low activity of most peroxidase mimics under neutral pH is crucial but still extremely challenging for the detection of disease markers in biological samples. Here, we chose nanoclay (i.e., montmorillonite K10, MK10) as a carrier to modulate the structure of Fe1-xS nanozyme components through an interfacial modulation strategy, aiming at breaking the neutral pH limitation of Fe1-xS. MK10 with abundant hydroxyl groups on its surface acts as a carrier to increase the ratio of Fe(II) and S(II-) content in surface Fe1-xS. We verify that Fe(II)-promoted surface hydroxyl radical generation and S(II-)-promoted regeneration of Fe(II) play key roles in endowing peroxidase-like activity to Fe1-xS at neutral pH. As expected, Fe1-xS/MK10 exhibited 11-fold higher Vmax and 52-fold higher catalytic efficiency than bare Fe1-xS. As a proof of concept, the sensor constructed based on Fe1-xS/MK10 achieved colorimetric detection of xanthine under neutral conditions with a linear range of 5-300 µM and a limit of detection of 2.49 µM. Finally, we achieved highly sensitive detection of xanthine in serum using the constructed biosensor. Our contribution is the novel use of a nanoclay-mediated interfacial modulation strategy for boosting the peroxidase-mimicking activity and breaking the pH limitation, which contributes to the in situ detection of disease markers by nanozymes under physiological conditions.

Mineral Phase Reconfiguration Enables the High Enzyme-like Activity of Vermiculite for Antibacterial Application.

Phyllosilicates-based nanomaterials, particularly iron-rich vermiculite (VMT), have wide applications in biomedicine. However, the lack of effective methods to activate the functional layer covered by the external inert layer limits their future applications. Herein, we report a mineral phase reconfiguration strategy to prepare novel nanozymes by a molten salt method. The peroxidase-like activity of the VMT reconfiguration nanozyme is 10 times that of VMT, due to the electronic structure change of iron in VMT. Density-functional theory calculations confirmed that the upward shifted d-band center of the VMT reconfiguration nanozyme promoted the adsorption of H2O2 on the active iron sites and significantly elongated the O-O bond lengths. The reconfiguration nanozyme exhibited nearly 100% antibacterial activity toward Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), much higher than that of VMT (E. coli 10%, S. aureus 21%). This work provides new insights for the rational design of efficient bioactive phyllosilicates-based nanozyme.

Mineral-Enhanced Manganese Ferrite with Multiple Enzyme-Mimicking Activities for Visual Detection of Disease Markers.

Local geometric configurations of metal cations in inorganic enzyme mimics determine their catalytic behaviors, while their optimization remains challenging. Herein, kaolinite, a naturally layered clay mineral, achieves the optimization of cationic geometric configuration in manganese ferrite. We demonstrate that the exfoliated kaolinite induces the formation of defective manganese ferrite and makes more iron cations fill into the octahedral sites, significantly enhancing the multiple enzyme-mimicking activities. The steady-state kinetic assay results show that the catalytic constant of composites toward 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 are more than 7.4- and 5.7-fold higher than manganese ferrite, respectively. Furthermore, density functional theory (DFT) calculations reveal that the outstanding enzyme-mimicking activity of composites is attributed to the optimized iron cation geometry configuration, which has a higher affinity and activation ability toward H2O2 and lowers the energy barrier of key intermediate formation. As a proof of concept, the novel structure with multiple enzyme-mimicking activities amplifies the colorimetric signal, realizing the ultrasensitive visual detection of disease marker acid phosphatase (ACP), with a detection limit of 0.25 mU/mL. Our findings provide a novel strategy for the rational design of enzyme mimics and an in-depth investigation of their enzyme-mimicking properties.

Nanoclay Modulates Cation Occupancy in Manganese Ferrite for Catalytic Antibacterial Treatment.

Controllable preparation is the current frontier in the field of inorganic nanomaterial-based artificial enzymes (nanozymes). For ferrites, the factors affecting cation occupancy are very complex, making the modulation of cation occupancy extremely challenging. Herein, we report a new strategy to modulate the cation occupancy of manganese ferrite (MFO) based on the structural properties of nanoclay (i.e., montmorillonite K10). It demonstrates that montmorillonite K10 mainly changes the valence state and occupancy of manganese ions in manganese ferrite and not iron ions. K10 increases the proportion of Mn (II) in manganese ferrite and causes more manganese ions to migrate to the tetrahedral sites. As expected, the prepared new inorganic compound possesses excellent enzyme-like catalytic activities and antibacterial functional properties, which are attributed to Mn (II) accelerating Fe (III) reduction and hydroxyl radical formation. Furthermore, steady-state kinetic assays are used to study the reaction mechanism in detail. In vitro and in vivo antibacterial experiments show that the synthesized inorganic compounds exhibit satisfactory disinfection and wound skin recovery efficiencies. This work emphasizes the controllable preparation of new inorganic compounds with biomimetic activity and provides novel insight into the biological effects of inorganic nanomaterials.

Surface acidity modulates the peroxidase-like activity of nanoclay.

A novel surface acidity modulation strategy allows us to obtain modified nanoclay with specific peroxidase (POD)-like catalytic activity. Fe3+ exchange could increase the surface acidity of modified montmorillonite (MMT), resulting in a significant enhancement of its POD-like activity. We proposed that the POD-like catalytic reaction followed the electron transfer pathway and ping-pong mechanism. Correspondingly the constructed colorimetric sensor for H2O2 exhibited high sensitivity and specificity.

[SNP in differentially methylated region upstream of H19 gene in Chinese Korean nationality].

OBJECTIVE: To investigate SNP and distribution of haplotypes in differentially methylated region (DMR) upstream of H19 gene in Chinese Korean nationality in order to provide basic data for forensic application and population genetics research. METHODS: One hundred and one blood samples from unrelated Chinese Korean individuals and 14 blood samples from 5 Chinese Korean intergenerational families which known genetic relationship were collected. The SNP in DMR upstream of H19 gene were investigated by PCR-cycle sequencing and McrBC digestion followed by PCR. The haplotypes detected by parentally imprinted allele (PIA) method and relevant genetic parameters were calculated. RESULTS: Thirteen SNPs (rs10840167, rs2525883, rs12417375, rs4930101, rs2525882, rs2735970, rs2735971, rs11042170, rs2735972, rs10732516, rs2071094, rs2107425, and rs4930098) and five haplotypes were detected in 1 174 bp target product in DMR upstream of H19 gene, with 9 SNPs having high discrimination power as good genetic markers. The average gene diversity (GD) of haplotypes was 0.714. The maternal haplotype was confirmed correctly by PIA method from McrBC-digested products of genomic DNA. CONCLUSION: High polymorphisms exist in DMR upstream of H19 gene in Chinese Korean nationality. And determination of the maternal haplotype could furthermore enhance the forensic identification efficiency of imprinted gene.