Enhancing Peroxidase Activity of Cytochrome c by Modulating Interfacial Interaction Forces with Graphene Oxide

Toxicological insights into graphene family materials: Cytochrome P450 modulation and cellular stress in liver cells

Graphene family materials (GFM), including pristine graphene (GN), graphene oxide (GO), and nano-sized graphene oxide (nGO), are increasingly utilized across industrial, environmental, and biomedical domains. Despite their potential benefits, the hazardous effects of GFM, particularly on liver xenobiotic-metabolizing enzymes and cellular functions, are not fully understood. Cytochrome P450 (CYP) are enzymes conserved across species, which play a crucial role in the metabolism of xenobiotics, drugs, environmental pollutants, and endogenous compounds, are key to understanding the biotransformation and detoxification processes impacted by GFM. This study investigates the effects of GFMs on CYP enzymes (CYP1A2, CYP2D6, CYP3A4) in a recombinant CYP system and HepG2 liver cells, alongside an assessment of cellular stress responses. In HepG2 cells, GFMs induced oxidative stress, mitochondrial depolarization, and cytotoxicity, with GN causing the most pronounced effects. GO exhibited the strongest inhibition of CYP enzymatic activity, particularly CYP1A2, in a dose-dependent manner in a recombinant CYP system. None of the tested nanomaterials significantly altered CYP expression, except for nGO, where a slight increase in CYP3A4 protein expression was observed. These findings highlight the significant influence of GFM physicochemical properties on their hazardous potential, especially their ability to disrupt metabolic processes and induce cellular stress. This study emphasizes the critical need for evaluating the safety of GFM in light of their widespread application and potential environmental and human health implications.

Insight into the efficient loading and enhanced activity of enzymes immobilized on functionalized UiO-66

Enzyme immobilization is an effective strategy for achieving efficient and sustainable enzyme catalysis. As a kind of promising enzyme-loading materials, the systematic research on zirconium based metal organic frameworks (Zr-MOFs) about immobilization performance at molecular level is still in its initial stage. In this work, UiO-66 was functionalized with various groups (-H, -NH2, -COOH, -OH, -2OH) for the immobilization of cytochrome c (Cyt c) and antioxidant enzyme catalase (CAT). Then the effects of surface-functionalized UiO-66 derivatives on the loading efficiency, enzyme stability and catalysis kinetics were systematically investigated. In addition, the affinity constants of Cyt c and CAT towards UiO-66-series MOFs carriers were also compared. The results have shown that hydroxyl group functionalized UiO-66 represents the highest enzyme loading capacity, enhanced activity and improved stability for Cyt c and CAT possibly due to high surface area and suitable microenvironments as well as enhanced affinity towards the enzymes provided by the introduction of a single hydroxyl group. Our research would foresee immense potential of MOFs in engineering biocatalysts.

Assessing the Redox Toxicity of 2D Nanosheets Based on Their Redox Effect on Cytochrome c in Microchannels

2D nanosheets (NSs) have been widely used in drug-related applications. However, a comprehensive investigation into the cytotoxicity mechanism linked to the redox activity is lacking. In this study, with cytochrome c (Cyt c) as the model biospecies, the cytotoxicity of 2D NSs was evaluated systematically based on their redox effect with microfluidic techniques. The interface interaction, dissolution, and redox effect of 2D NSs on Cyt c were monitored with pulsed streaming potential (SP) measurement and capillary electrophoresis (CE). The relationship between the redox activity of 2D NSs and the function of Cyt c was evaluated in vitro with Hela cells. The results indicated that the dissolution and redox activity of 2D NSs can be simultaneously monitored with CE under weak interface interactions and at low sample volumes. Both WS2 NSs and MoS2 NSs can reduce Cyt c without significant dissolution, with reduction rates measured at 6.24 × 10-5 M for WS2 NSs and 3.76 × 10-5 M for MoS2 NSs. Furthermore, exposure to 2D NSs exhibited heightened reducibility, which prompted more pronounced alterations associated with Cyt c dysfunction, encompassing ATP synthesis, modifications in mitochondrial membrane potential, and increased reactive oxygen species production. These observations suggest a positive correlation between the redox activity of 2D NSs and their redox toxicity in Hela cells. These findings provide valuable insight into the redox properties of 2D NSs regarding cytotoxicity and offer the possibility to modify the 2D NSs to reduce their redox toxicity for clinical applications.

A transient vesicular glue for amplification and temporal regulation of biocatalytic reaction networks

Regulation of enzyme activity and biocatalytic cascades on compartmentalized cellular components is key to the adaptation of cellular processes such as signal transduction and metabolism in response to varying external conditions. Synthetic molecular glues have enabled enzyme inhibition and regulation of protein-protein interactions. So far, all the molecular glue systems based on covalent interactions operated under steady-state conditions. To emulate dynamic biological processes under dissipative conditions, we introduce herein a transient supramolecular glue with a controllable lifetime. The transient system uses multivalent supramolecular interactions between guanidinium group-bearing surfactants and adenosine triphosphate (ATP), resulting in bilayer vesicle structures. Unlike the conventional chemical agents for dissipative assemblies, ATP here plays the dual role of providing a structural component for the assembly as well as presenting active functional groups to "glue" enzymes on the surface. While gluing of the enzymes on the vesicles achieves augmented catalysis, oscillation of ATP concentration allows temporal control of the catalytic activities similar to the dissipative cellular nanoreactors. We further demonstrate temporal upregulation and control of complex biocatalytic reaction networks on the vesicles. Altogether, the temporal activation of biocatalytic cascades on the dissipative vesicular glue presents an adaptable and dynamic system emulating heterogeneous cellular processes, opening up avenues for effective protocell construction and therapeutic interventions.

Intrinsic mechanisms for the inhibition effect of graphene oxide on the catalysis activity of alpha amylase

Comprehending the interactions between graphene oxide (GO) and enzymes is critical for understanding the toxicities of GO. In this study, the inherent interactions of GO with α-amylase as a typical enzyme, and the impacts of GO on the conformation and biological activities of α-amylase were systematically investigated. The results reveal that GO formed ground-state complex with α-amylase primarily via hydrogen bonding and van der Waals interactions, thus quenching the intrinsic fluorescence of the protein statically. Particularly, the strong interactions altered the microenvironment of tyrosine and tryptophan residues, caused rearrangement of polypeptide structure, and reduced the contents of α-helices and β-sheets, thus changing the conformational structure of α-amylase. According to molecular docking results, GO binds with the amino acid residues (i.e., His299, Asp300, and His305) of α-amylase mainly through hydrogen bonding, which is in accordance with in vitro incubation experiments. As a consequence, the ability of α-amylase to catalyze starch hydrolysis into glucose was depressed by GO, suggesting that GO might cause dysfunction of α-amylase. This study discloses the intrinsic binding mechanisms of GO with α-amylase and provides novel insights into the adverse effects of GO as it enters organisms.

Revealing the Nanoarchitectonics of Amyloid β-Aggregation on Two-Dimensional Biomimetic Membranes by Surface-Enhanced Infrared Absorption Spectroscopy

The in vivo folding of amyloid β (Aβ) is influenced by many factors among which biomembrane interfaces play an important role. Here, using surface-enhanced infrared absorption (SEIRA) spectroscopy and atomic force microscopy (AFM), the adsorption, structure, and morphology of Aβ42 aggregating on different two-dimensional interfaces were investigated. Results show that interfaces facilitate the aggregation of Aβ42 and are conducive to the formation of homogeneous aggregates, while the aggregates vary on different interfaces. On hydrophobic interfaces, strong hydrophobic interactions with the C-terminus of Aβ42 result in the formation of small oligomers with a small proportion of the β-sheet structure. On hydrophilic interfaces, hydrogen-bonding interactions and electrostatic interactions promote the formation of large aggregate particles with β-sheet structure. The hydration repulsion plays an important role in the interaction of Aβ42 with interfaces. These findings help to understand the nature of Aβ42 adsorption and aggregation on the biomembrane interface and the origin of heterogeneity and polymorphism of Aβ42 aggregates.

Nanoconfined Electrochemical Collision and Catalysis of Single Enzyme inside Carbon Nanopipettes

Revealing the electrocatalytic features of single redox enzyme is significant to both fundamental biological processes and practical catalysis and sensing applications. Herein, we directly reveal the electrocatalytic current from a single enzyme inside the carbon nanopipettes via electrochemical collision strategies, based on the increased activity at nanoscale confinement. Besides the staircase current steps from surface blockage, discrete H₂O₂ oxidation and reduction current transients catalyzed by a single enzyme are also displayed and analyzed. The carbon nanopipette would increase the catalytic activities of enzymes and lead to a detectable current response, thus opening a new way to investigate the fundamental enzymatic mechanisms at the single enzyme level.

Enhanced Catalytic Activity of a New Nanobiocatalytic System Formed by the Adsorption of Cytochrome c on Pluronic Triblock Copolymer Stabilized MoS2 Nanosheets

The formation of nanobiohybrids through the immobilization of enzymes on functional nanomaterials has opened up exciting research opportunities at the nanobiointerfaces. These systems hold great promise for a wide range of applications in biosensing, biocatalytic, and biomedical fields. Here, we report the formation of a hybrid nanobiocatalytic system through the adsorption of cytochrome c (Cyt c) on pluronic triblock copolymer, P123 (PEO-b-PPO-b-PEO), stabilized MoS2 nanosheets. The use of pluronic polymer has helped not only to greatly stabilize the exfoliated MoS2 nanosheets but also to allow easy adsorption of Cyt c on the nanosheets without major structural changes due to its excellent biocompatibility and soft protein-binding property. By comparing the catalytic activity of the Cyt c-MoS2 nanobiohybrid with that of the free Cyt c and as-prepared MoS2 nanosheets, we have demonstrated the active role of the nanobiointeractions in enhancing the catalytic activity of the hybrid. Slight structural perturbation at the active site of the Cyt c upon adsorption on MoS2 has primarily facilitated the peroxidase activity of the Cyt c. As the MoS2 nanosheets and the native Cyt c individually exhibit weaker intrinsic peroxidase activities, their mutual modulation at the nanobiointerface has made the Cyt c-MoS2 a novel nanobiocatalyst with superior activity.

Protein immobilization on graphene oxide or reduced graphene oxide surface and their applications: Influence over activity, structural and thermal stability of protein

Due to the essential role of biological macromolecules in our daily life; it is important to control the stability and activity of such macromolecules. Therefore, the most promising route for enhancement in stability and activity is immobilizing proteins on different support materials. Furthermore, large surface area and surface functional groups are the important features that are required for a better support system. These features of graphene oxide (GO) and reduced graphene oxide (RGO) makes them ideal support materials for protein immobilization. Studies show the successful formation of GO/RGO-protein complexes with enhancement in structural/thermal stability due to various interactions at the nano-bio interface and their utilization in various functional applications. The present review focuses on protein immobilization using GO/RGO as solid support materials. Moreover, we also emphasized on basic underlying mechanism and interactions (hydrophilic, hydrophobic, electrostatic, local protein-protein, hydrogen bonding and van der Walls) between protein and GO/RGO which influences structural stability and activity of enzymes/proteins. Furthermore, GO/RGO-protein complexes are utilized in various applications such as biosensors, bioimaging and theranostic agent, targeted drug delivery agents, and nanovectors for drug and protein delivery.