Superior Compatibility of C2 N with Human Red Blood Cell Membranes and the Underlying Mechanism

Screening 2D Materials for Their Nanotoxicity toward Nucleic Acids and Proteins: An In Silico Outlook

Since the discovery of graphene, two-dimensional (2D) materials have been anticipated to demonstrate enormous potential in bionanomedicine. Unfortunately, the majority of 2D materials induce nanotoxicity via disruption of the structure of biomolecules. Consequently, there has been an urge to synthesize and identify biocompatible 2D materials. Before the cytotoxicity of 2D nanomaterials is experimentally tested, computational studies can rapidly screen them. Additionally, computational analyses can provide invaluable insights into molecular-level interactions. Recently, various "in silico" techniques have identified these interactions and helped to develop a comprehensive understanding of nanotoxicity of 2D materials. In this article, we discuss the key recent advances in the application of computational methods for the screening of 2D materials for their nanotoxicity toward two important categories of abundant biomolecules, namely, nucleic acids and proteins. We believe the present article would help to develop newer computational protocols for the identification of novel biocompatible materials, thereby paving the way for next-generation biomedical and therapeutic applications based on 2D materials.

Computational Assessment of the Biocompatibility of Two-Dimensional g-C3N3 Toward Lipid Membranes

One of the most recent additions to the family of two-dimensional (2D) materials, graphitic C3N3 (g-C3N3), has been considered a viable contender for biomedical applications, although its potential toxicity remains elusive. We perform all-atom molecular dynamics simulations to decipher the interactions between model lipid membranes and g-C3N3 as a first step toward exploring the cytotoxicity induced at the nanoscale. We show that g-C3N3 can easily insert into the cellular membranes following a multistage mechanism consisting of simultaneous desolvation of the 2D material along with enrichment of nanomaterial-lipid interactions. Free energy calculations indicate that g-C3N3 is more stable in a membrane-bound state compared to an aqueous solution; however, the insertion of the material does not disturb the structural integrity of lipid membranes. After being inserted into a membrane, g-C3N3 is unlikely to be released into the cellular environment and is incapable of extracting lipid molecules from the membrane. The nature of interaction between the 2D material and membranes is found to be independent of the nanomaterial size. Also, the performance of g-C3N3 toward biomolecular delivery is shown to be significantly improved compared to the state-of-the-art 2D materials graphene and hexagonal boron nitride (h-BN). It is revealed that, the affinity of g-C3N3 toward lipid membranes is weaker compared to the nanotoxic graphene and h-BN, while being marginally higher than h2D-C2N, which in turn, increases the biocompatibility of the material, thereby brightening its future as a noncytotoxic material for forthcoming biomedical applications.

Better biocompatibility of nitrogen-doped graphene compared with graphene oxide by reducing cell autophagic flux blockage and cell apoptosis

Nitrogen-doped graphene (C2 N), a novel graphene-based materials, has been proposed as a potential alternative to graphene oxide (GO) in biomedical applications. However, due to the challenges in synthesizing C2 N, reports in the biomedical field are currently rare. Here, we have modified the reported procedure and successfully synthesized C2 N nanoparticles at 120°C, which we refer to as C2 N-120. The toxicity and biocompatibility of GO and C2 N-120 were evaluated using a mouse model injected with GO/C2 N-120 via the tail vein, as well as cell models treated with GO/C2 N-120. In vivo studies revealed that GO/C2 N-120 showed similar distribution patterns after tail vein injection. The liver, spleen, and lung are the major nanoparticle uptake organs of GO and C2 N-120. However, GO deposition in the major nanoparticle uptake organs was more significant than that of C2 N-120. In addition, GO deposition caused structural abnormalities, increased apoptotic cells, and enhanced macrophage infiltration whereas C2 N-120 exhibited fewer adverse effects. In vitro experiments were conducted using different cell lines treated with GO/C2 N-120. Unlike GO which induced mitochondrial damage, oxidative stress, inflammatory response, autophagic flux blockage and cell apoptosis, C2 N-120 showed lower cytotoxicity in cell models. Our data demonstrated that C2 N-120 exhibits higher biocompatibility than GO, both in vivo and in vitro, suggesting its potential for biomedical application in the future.

A simple and efficient process for the synthesis of 2D carbon nitrides and related materials

We describe here a new process for the synthesis of very high quality 2D Covalent Organic Frameworks (COFs), such a C2N and CN carbon nitrides. This process relies on the use of a metallic surface as both a reagent and a support for the coupling of small halogenated building blocks. The conditions of the assembly reaction are chosen so as to leave the inorganic salts by-products on the surface, to further confine the assembly reaction on the surface and increase the quality of the 2D layers. We found that under these conditions, the process directly returns few layers material. The structure/quality of these materials is demonstrated by extensive cross-characterizations at different scales, combining optical microscopy, Scanning Electron Microscopy (SEM)/Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS). The availability of such very large, high-quality layers of these materials opens interesting perspectives, for example in photochemistry and electronics (intrinsic transport properties, high gap substrate for graphene, etc...).

Moderate binding of villin headpiece protein to C3N3 nanosheet reveals the suitable biocompatibility of this nanomaterial

Since its recent successful synthesis and due to its promising physical and chemical properties, the carbon nitrite nanomaterial, C3N3, has attracted considerable attention in various scientific areas. However, thus far, little effort has been devoted to investigating the structural influence of the direct interaction of this 2D nanomaterial and biomolecules, including proteins and biomembranes so as to understand the physical origin of its bio-effect, particularly from the molecular landscape. Such information is fundamental to correlate to the potential nanotoxicology of the C3N3 nanomaterial. In this work, we explored the potential structural influence of a C3N3 nanosheet on the prototypical globular protein, villin headpiece (HP35) using all-atom molecular dynamics (MD) simulations. We found that HP35 could maintain its native conformations upon adsorption onto the C3N3 nanosheet regardless of the diversity in the binding sites, implying the potential advantage of C3N3 in protecting the biomolecular structure. The adsorption was mediated primarily by vdW interactions. Moreover, once adsorbed on the C3N3 surface, HP35 remains relatively fixed on the nanostructure without a distinct lateral translation, which may aid in keeping the structural integrity of the protein. In addition, the porous topological structure of C3N3 and the special water layer present on the C3N3 holes conjointly contributed to the restricted motion of HP35 via the formation of a high free energy barrier and a steric hindrance to prevent the surface displacement. This work revealed for the first time the potential influence of the 2D C3N3 nanomaterial in the protein structure and provided the corresponding in-depth molecular-level mechanism, which is valuable for future applications of C3N3 in bionanomedicine.

Robust Mechanical Destruction to the Cell Membrane of Carbon Nitride Polyaniline (C3N): A Molecular Dynamics Simulation Study

The drug-resistant bacteria, particularly multidrug-resistant bacteria, has emerged as a major global public health concern posing serious threats to human life and survival. Nanomaterials, including graphene, have shown promise as effective antibacterial agents owing to their unique antibacterial mechanism compared with traditional drugs. Despite the structural similarity to graphene, the potential antibacterial activity of carbon nitride polyaniline (C₃N) remains unexplored. In this study, we employed molecular dynamics simulations to investigate the effects of the interaction between the C₃N nanomaterial and the bacterial membrane to evaluate the potential antibacterial activity of C₃N. Our results suggest that C₃N is capable of inserting deep into the bacterial membrane interior, regardless of the presence or absence of positional restraints in the C₃N. The insertion process also resulted in local lipid extraction by the C₃N sheet. Additional structural analyses revealed that C₃N induced significant changes in membrane parameters, including mean square displacement, deuterium order parameters, membrane thickness, and area per lipid. Docking simulations, where all the C₃N are restraint to a specific positions, confirmed that C₃N can extract lipids from the membrane, indicating the strong interaction between the C₃N material and the membrane. Free-energy calculations further revealed that the insertion of the C₃N sheet is energetically favorable and that C₃N exhibits membrane insertion capacity comparable to that observed for graphene, suggesting their potential for similar antibacterial activity. This study provides the first evidence of the potential antibacterial properties of C₃N nanomaterials via bacterial membrane damage and underscores the potential for its use as antibacterial agents in the future applications.

The Interaction Mechanism of Intramuscular Gene Delivery Materials with Cell Membranes

It has been confirmed that skeletal muscle cells have the capability to receive foreign plasmid DNA (pDNA) and express functional proteins. This provides a promisingly applicable strategy for safe, convenient, and economical gene therapy. However, intramuscular pDNA delivery efficiency was not high enough for most therapeutic purposes. Some non-viral biomaterials, especially several amphiphilic triblock copolymers, have been shown to significantly improve intramuscular gene delivery efficiency, but the detailed process and mechanism are still not well understood. In this study, the molecular dynamics simulation method was applied to investigate the structure and energy changes of the material molecules, the cell membrane, and the DNA molecules at the atomic and molecular levels. From the results, the interaction process and mechanism of the material molecules with the cell membrane were revealed, and more importantly, the simulation results almost completely matched the previous experimental results. This study may help us design and optimize better intramuscular gene delivery materials for clinical applications.

Cytocompatibility of Ti3C2Tx MXene with Red Blood Cells and Human Umbilical Vein Endothelial Cells and the Underlying Mechanisms

Two-dimensional (2D) nanomaterials have been widely used in biomedical applications because of their biocompatibility. Considering the high risk of exposure of the circulatory system to Ti3C2Tx, we studied the cytocompatibility of Ti3C2Tx MXene with red blood cells (RBCs) and human umbilical vein endothelial cells (HUVECs) and showed that Ti3C2Tx had excellent compatibility with the two cell lines. Ti3C2Tx at a concentration as high as 200 μg/mL caused a negligible percent hemolysis of 0.8%. By contrast, at the same treatment concentration, graphene oxide (GO) caused a high percent hemolysis of 50.8%. Scanning electron microscopy revealed that RBC structures remained intact in the Ti3C2Tx treatment group, whereas those in the GO group completely deformed, sunk, and shrunk, which resulted in the release of cell contents. This difference can be largely ascribed to the distinct surficial properties of the two nanosheets. In specific, the fully covered surface-terminating -O and -OH groups leading to Ti3C2Tx had a very hydrophilic surface, thereby hindering its penetration into the highly hydrophobic interior of the cell membrane. However, the strong direct van der Waals attractions coordinated with hydrophobic interactions between the unoxidized regions of GO and the lipid hydrophobic tails can still damage the integrity of the cell membranes. In addition, the sharp and keen-edged corners of GO may also facilitate its relatively strong cell membrane damage effects than Ti3C2Tx. Thus, the excellent cell membrane compatibility of Ti3C2Tx nanosheets and their ultraweak capacity to provoke excessive ROS generation endowed them with much better compatibility with HUVECs than GO nanosheets. These results indicate that Ti3C2Tx has much better cytocompatibility than GO and provide a valuable reference for the future biomedical applications of Ti3C2Tx.

Effects of urban particulate matter on the quality of erythrocytes

With the acceleration of industrialisation and urbanisation, air pollution has become a serious global concern as a hazard to human health, with urban particulate matter (UPM) accounting for the largest share. UPM can rapidly pass into and persist within systemic circulation. However, few studies exist on whether UPM may have any impact on blood components. In this study, UPM standards (SRM1648a) were used to assess the influence of UPM on erythrocyte quality in terms of oxidative and metabolic damage as well as phagocytosis by macrophages in vitro and clearance in vivo. Our results showed that UPM had weak haemolytic properties. It can oxidise haemoglobin and influence the oxygen-carrying function, redox balance, and metabolism of erythrocytes. UPM increases the content of reactive oxygen species (ROS) and decreases antioxidant function according to the data of malonaldehyde (MDA), glutathione (GSH), and glucose 6 phosphate dehydrogenase (G6PDH). UPM can adhere to or be internalised by erythrocytes at higher concentrations, which can alter their morphology. Superoxide radicals produced in the co-incubation system further disrupted the structure of red blood cell membranes, thereby lowering the resistance to the hypotonic solution, as reflected by the osmotic fragility test. Moreover, UPM leads to an increase in phosphatidylserine exposure in erythrocytes and subsequent clearance by the mononuclear phagocytic system in vivo. Altogether, this study suggests that the primary function of erythrocytes may be affected by UPM, providing a warning for erythrocyte quality in severely polluted areas. For critically ill patients, transfusion of erythrocytes with lesions in morphology and function will have serious clinical consequences, suggesting that potential risks should be considered during blood donation screening. The current work expands the scope of blood safety studies.

Nonmonotonic Relationship between the Oxidation State of Graphene-Based Materials and Its Cell Membrane Damage Effects

With the rapid development of carbon-based two-dimensional nanomaterials in biomedical applications, growing concern has emerged regarding their biocompatibility and especially their interactions with cell membranes. Our experimental studies found that the oxidation state, as one of the most important chemical parameters of graphene derivatives, regulates the hemolysis effect on human red blood cells in a nonmonotonic manner. Scanning electron microscopy and optical microscopy observations suggested that graphene oxides with medium oxygen content have the most serious destructive effects on the cell membranes. Molecular dynamics simulations and potential of mean force calculations revealed that, on the one hand, with the decrease in the surface oxygenated groups, more sp² carbon area of graphene-based materials will be exposed, playing a facilitating role in the damage of cell membranes; on the other hand, fewer oxygenated groups also lead to the accumulation of graphene-based nanosheets in solutions. The formation of the multilayer structure of graphene-based nanosheets reduces the exposed sp² carbon area, prevents the collective extraction of lipid molecules, and eventually results in a weakened extraction effect on cell membranes. Together, these factors generate a nonmonotonic relationship between the oxidation state of graphene oxides and their destructive effects on cell membranes.

On the interface between biomaterials and two-dimensional materials for biomedical applications

Two-dimensional (2D) materials have garnered significant attention due to their ultrathin 2D structures with a high degree of anisotropy and functionality. Reliable manipulation of interfaces between 2D materials and biomaterials is a new frontier for biomedical nanoscience and combining biomaterials with 2D materials offers a promising way to fabricate innovative 2D biomaterials composites with distinct functionality for biomedical applications. Here, we focus exclusively on a summary of the current work in the interface investigation of 2D biomaterials. Specifically, we highlight extraordinary features that make 2D materials so desirable, as well as the molecular level interactions between 2D materials and biomaterials that have been studied thus far. Furthermore, the approaches for investigating the interface characteristics of 2D biomaterials are presented and described in depth. To capture the emerging trend in mass manufacturing of 2D materials, we review the research progress on biomaterial-assisted exfoliation. Finally, we present a critical assessment of newly developed 2D biomaterials in biomedical applications.

Modulation of the thermal conductivity, interlayer thermal resistance, and interfacial thermal conductance of C2N

C₂N, a novel 2D semiconductor with orderly distributed holes and nitrogen atoms, has attracted significant attention due to its possible practical applications. This paper investigates the in-plane thermal conductivity and interlayer thermal resistance of C₂N and the interfacial thermal conductance of in-plane heterostructures assembled by C₂N and carbonized C₂N(C-C₂N) using molecular dynamics simulations. The in-plane thermal conductivities of C₂N monolayers along zigzag and armchair directions are 73.2 and 77.3 W m^-1 K^-1, respectively, and can be effectively manipulated by point defects, chemical doping, and strain engineering. Remarkably, nitrogen vacancies have a more substantial impact on reducing the thermal conductivity than carbon vacancies because of the more pronounced suppression of the high-frequency peaks. The difference in doping sites leads to a change in phonon mode localization. When the C₂N size is small, as the tensile strain increases, k_i is affected by dimensional lengthening due to stretching in addition to tensile strain. The interlayer thermal resistance decreases with increasing layer number and interlayer coupling strength. The AA stacking gives rise to a lower thermal resistance than the AB stacking when the heat flow passes through the multilayer due to the weaker in-plane bonding strength. Moreover, various possible atomic structures of C₂N/C-C₂N in-plane heterojunctions and the effect of carbon and nitrogen vacancies on interfacial thermal conductance are explored. The results provide valuable insights into the thermal transport properties in the application of C₂N-based electronic devices.

Mild adsorption of carbon nitride (C3N3) nanosheet on a cellular membrane reveals its suitable biocompatibility

Recently, the novel hole-containing carbon nitride C₃N₃ nanomaterial was successfully synthesized, featuring outstanding and unique mechanical and electrical properties. However, to fully exploit this nanomaterial in biomedical applications, information regarding its biocompatibility is necessary. Herein, by using all-atom molecular dynamics simulations, we evaluate the interactions between a C₃N₃ nanosheet and a critical cellular component, that is, a lipid membrane bilayer. Our results indicate that the C₃N₃ nanosheet is able to interact with the lipid bilayer surface without affecting the membrane's structural integrity. Moreover, our results showed that the C₃N₃ nanosheet is adsorbed on the surface of the lipid bilayer without inflicting any structural damage to the membrane, regardless of the conditions of the system (that is, with and without restrains in the C₃N₃ nanosheet). Also, we found that both energy contributions, namely vdW and Coulomb energies, conjointly mediated the C₃N₃ adsorption process. In comparison and as expected, pristine graphene significantly disturbed the membrane structure. Perpendicularly-oriented-sheet simulations described the significance of the surface charges of the C₃N₃ nanosheet in prohibiting its insertion into the membrane. Detailed analysis indicated that the electrostatic attraction between the pores in the C₃N₃ structure and the lipid head amino groups stabilized the interaction restricting the insertion of the C₃N₃ structure deeper into the membrane. Our results suggested the importance of the negatively charged C₃N₃ pores when interacting with lipid membranes. Our findings shed light on the potential compatibility of C₃N₃ with biomembranes and its underlying molecular mechanism, which might provide a useful foundation for the future exploration of this 2D nanomaterial in biomedical applications.

Biotransformation of rare earth oxide nanoparticles eliciting microbiota imbalance

Background

Disruption of microbiota balance may result in severe diseases in animals and phytotoxicity in plants. While substantial concerns have been raised on engineered nanomaterial (ENM) induced hazard effects (e.g., lung inflammation), exploration of the impacts of ENMs on microbiota balance holds great implications.

Results

This study found that rare earth oxide nanoparticles (REOs) among 19 ENMs showed severe toxicity in Gram-negative (G⁻) bacteria, but negligible effects in Gram-positive (G⁺) bacteria. This distinct cytotoxicity was disclosed to associate with the different molecular initiating events of REOs in G⁻ and G⁺ strains. La₂O₃ as a representative REOs was demonstrated to transform into LaPO₄ on G⁻ cell membranes and induce 8.3% dephosphorylation of phospholipids. Molecular dynamics simulations revealed the dephosphorylation induced more than 2-fold increments of phospholipid diffusion constant and an unordered configuration in membranes, eliciting the increments of membrane fluidity and permeability. Notably, the ratios of G⁻/G⁺ reduced from 1.56 to 1.10 in bronchoalveolar lavage fluid from the mice with La₂O₃ exposure. Finally, we demonstrated that both IL-6 and neutrophil cells showed strong correlations with G⁻/G⁺ ratios, evidenced by their correlation coefficients with 0.83 and 0.92, respectively.

Conclusions

This study deciphered the distinct toxic mechanisms of La₂O₃ as a representative REO in G⁻ and G⁺ bacteria and disclosed that La₂O₃-induced membrane damages of G⁻ cells cumulated into pulmonary microbiota imbalance exhibiting synergistic pulmonary toxicity. Overall, these findings offered new insights to understand the hazard effects induced by REOs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00410-5.

Boron nitride nanosheets elicit significant hemolytic activity via destruction of red blood cell membranes

Boron nitride (BN) nanosheets have emerged as promising nanomaterials in a wide range of biomedical applications. Despite extensive studies on these bio-nano interfacial systems, the underlying molecular mechanisms remain elusive. In this study, we used hemolysis assays and morphology observations to demonstrate for the first time that BN nanosheets can cause damages to the red-blood-cell membranes, leading to significant hemolysis. Further molecular dynamics simulations revealed that BN nanosheets can penetrate into the cell membrane and also extract considerable amount of phospholipid molecules directly from the lipid bilayer. The potential of mean force calculations then showed that their penetration effect was thermodynamically favorable due to the strong attractive van der Waals interactions between BN nanosheets and phospholipids. Overall, these findings provided valuable insights into the interaction of BN nanosheets with cell membranes at the atomic level, which can help future de novo design of BN-based nanodevices with better biocompatibility.

Current advances in nanomaterials affecting morphology, structure, and function of erythrocytes

In recent decades, nanomaterials have been widely used in the field of biomedicine due to their unique physical and chemical properties, and have shown good prospects for in vitro diagnosis, drug delivery, and imaging. With regard to transporting nanoparticles (NPs) to target tissues or organs in the body intravenously or otherwise, blood is the first tissue that NPs come into contact with and is also considered an important gateway for targeted transport. Erythrocytes are the most numerous cells in the blood, but previous studies based on interactions between erythrocytes and NPs mostly focused on the use of erythrocytes as drug carriers for nanomedicine which were chemically bound or physically adsorbed by NPs, so little is known about the effects of nanoparticles on the morphology, structure, function, and circulation time of erythrocytes in the body. Herein, this review focuses on the mechanisms by which nanoparticles affect the structure and function of erythrocyte membranes, involving the hemocompatibility of NPs, the way that NPs interact with erythrocyte membranes, effects of NPs on erythrocyte surface membrane proteins and their structural morphology and the effect of NPs on erythrocyte lifespan and function. The detailed analysis in this review is expected to shed light on the more advanced biocompatibility of nanomaterials and pave the way for the development of new nanodrugs.

C2N: A Class of Covalent Frameworks with Unique Properties

C2N is a unique member of the CnNm family (carbon nitrides), i.e., having a covalent structure that is ideally composed of carbon and nitrogen with only 33 mol% of nitrogen. C2N, with a stable composition, can easily be prepared using a number of precursors. Moreover, it is currently gaining extensive interest owing to its high polarity and good thermal and chemical stability, complementing carbon as well as classical carbon nitride (C3N4) in various applications, such as catalysis, environmental science, energy storage, and biotechnology. In this review, a comprehensive overview on C2N is provided; starting with its preparation methods, followed by a fundamental understanding of structure-property relationships, and finally introducing its application in gas sorption and separation technologies, as supercapacitor and battery electrodes, and in catalytic and biological processes. The review with an outlook on current research questions and future possibilities and extensions based on these material concepts is ended.

Recent progress of graphene oxide as a potential vaccine carrier and adjuvant

Vaccine is one of the most effective strategies for preventing and controlling infectious diseases and some noninfectious diseases, especially cancers. Adjuvants and carriers have been appropriately added to the vaccine formulation to improve the immunogenicity of the antigen and induce long-lasting immunity. However, there is an urgent need to develop new all-purpose adjuvants because some adjuvants approved for human use have limited functionality. Graphene oxide (GO), widely employed for the delivery of biomolecules, excels in loading and delivering antigen and shows the potentiality of activating the immune system. However, GO aggregates in biological liquid and induces cell death, and it also exhibits poor biosolubility and biocompatibility. To address these limitations, various surface modification protocols have been employed to integrate aqueous compatible substances with GO to effectively improve its biocompatibility. More importantly, these modifications render functionalized-GO with superior properties as both carriers and adjuvants. Herein, the recent progress of physicochemical properties and surface modification strategies of GO for its application as both carriers and adjuvants is reviewed. STATEMENT OF SIGNIFICANCE: Due to its unique physicochemical properties, graphene oxide is widely employed in medicine for purposes of photothermal treatment of cancer, drug delivery, antibacterial therapy, and medical imaging. Our work describes the surface modification of graphene oxide and for the first time summarizes that functionalized graphene oxide serves as a vaccine carrier and shows significant adjuvant activity in activating cellular and humoral immunity. In the future, it is expected to be introduced into vaccine research to improve the efficacy of vaccines.

Directional extraction and penetration of phosphorene nanosheets to cell membranes

Recently, phosphorene, a novel two-dimensional nanomaterial with a puckered surface morphology, was shown to exhibit cytotoxicity, but its underlying molecular mechanisms remain unknown. Herein, using large scale molecular dynamics simulations, we show that phosphorene nanosheets can penetrate into and extract large amounts of phospholipids from the cell membranes due to the strong dispersion interaction between phosphorene and lipid molecules, which would reduce cell viability. The extracted phospholipid molecules are aligned along the wrinkle direction of the phosphorene nanosheet because of its unique puckered structure. Our results also reveal that small phosphorene nanosheets penetrate into the cell membrane in a specific direction which is determined by the size and surface topography of phosphorene and the thickness of the membrane. These findings might shed light on understanding phosphorene's cytotoxicity and would be helpful for the future potential biomedical applications of phosphorene, such as biosensors and antibacterial agents.

The role of electrostatic potential polarization in the translocation of graphene quantum dots across membranes

Graphene quantum dots (GQDs) have shown promising potential applications in the field of biomedicine. To date, understanding the GQD-cell membrane interactions remains a key issue in developing their biomedical applications, such as targeted drug delivery and bio-imaging. In this study, we mainly shed light on the mechanism of how to control the interactions between GQDs and membranes by tuning the electrostatic potential (EP) of GQDs. Charge distributions at the edge sites were adjusted to mimic the modified EP of GQDs, given that the physicochemical properties of GQDs are usually regulated and determined by the grafted groups and doped atoms at edges. We found that the dynamics of GQDs in the GQD-membrane system can be regulated effectively by modulating the EP of GQDs, which is not only determined by the direct GQD-cell interactions but also by the GQD-water interactions. GQDs with non- or less-polarized EP are hydrophobic, and they can easily translocate into the inner membrane from the bulk water because of the decreased GQD-POPC van der Waals interactions and the favorable dehydration process. In the case of a GQD with more polarized EP, the nanomaterial prefers to adsorb onto the membrane surface due to the strong electrostatic attraction between the GQD and lipid headgroups, and especially, the high dehydration free energy of GQDs can even lead to transient detachment from the surface. These findings would be helpful to understand the interactions between GQD-based nanomaterials and cell membranes, facilitating the rational design of GQD-related biomedicines.

Ultra-small and biocompatible platinum nanoclusters with peroxidase-like activity for facile glucose detection in real samples

The highly sensitive glucose detection based on the peroxidase-like properties of nanoclusters has been gained great interest. In this work, Pericarpium Citri Reticulatae polysaccharide (PCRP) stabilized platinum nanoclusters (Pt-PCRP NCs) were prepared by a green method in which potassium tetrachloroplatinate and PCRP were simply mixed without addition of other agents. Platinum nanoclusters (Pt NCs) had ultra-small size of 1.26 ± 0.34 nm. The hydrodynamic size of Pt-PCRP NCs was 29.7 nm, and zeta potential of which was -12.0 mV. Pt-PCRP NCs showed high biocompatibility toward HeLa cells and red blood cells. In addition, Pt-PCRP NCs catalyzed the decomposition of H₂O₂ to produce •OH, which further oxidized colorless 3,3'5,5'-tetramethylbenzidine (TMB) to blue oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB), exhibiting peroxidase-like property. The kinetics followed the Michaelis-Menten equation. More importantly, the colorimetric method for glucose detection using Pt-PCRP NCs had high selectivity and low detection limit for 0.38 μM. The established method based on Pt-PCRP NCs was used to precisely detect glucose detection in human serum, saliva, and sweat. Taken together, the prepared ultra-small and biocompatible Pt-PCRP NCs have good potential glucose applications in clinical diagnosis in the future.

Screening two dimensional materials for the transportation and delivery of diverse genetic materials

In spite of several reports of graphene and other 2D materials concerning their capacity for biomolecular adsorption and delivery, recent toxicity evaluations found them to be nanotoxic toward different biomolecules, especially nucleic acids. Therefore, there is urgent demand for the synthesis of 2D materials exhibiting biocompatible and non-nanotoxic features. In this article, employing classical molecular dynamics simulations, we provide a benchmarking of h2D-C2N, graphene and hexagonal boron nitride (h-BN) toward the adsorption, preservation, targeting and delivery of various classes of nucleic acids namely single stranded DNA, double stranded natural as well as unnatural base substituted DNA and two different types of human telomeric guanine quadruplexes, all comprising different secondary structures. Our simulations reveal that, while h2D-C2N preserves the structures of most of the nucleic acids, graphene and h-BN disrupt them through strong π-π stacking with aromatic nucleobases. Interestingly, for the first time we identified a 'quartet-by-quartet' disruption mechanism of guanine quadruplexes, but only on graphene and h-BN. The lateral diffusion of adsorbed nucleic acids over C2N is restricted unlike that over both graphene and h-BN, thereby increasing the targeting efficacy for C2N. Modeling of the delivery phenomena suggests orders of magnitude longer release times from graphene and h-BN compared to C2N, thereby demonstrating the preferential suitability of C2N for all the hierarchical steps of nucleic acid transportation.

Mild lipid extraction and anisotropic cell membrane penetration of α-phase phosphorene carbide nanoribbons by molecular dynamics simulation studies

α-PC penetrates the interior of membrane efficiently only along its zigzag direction rather than its armchair direction.

Cytotoxicity of C2N Originating from Oxidative Stress Instead of Membrane Stress

Two-dimensional (2D) nanomaterials have shown promising potential in a wide range of biomedical applications. Nevertheless, the rapid advances in this field recently have also evoked growing concerns about their toxic effects on humans and the environment. Herein, we systematically investigate the potential cytotoxicity of C₂N nanosheets, a newly emerging 2D nitrogenized graphene with uniform holes in the basal plane. Our in vitro experiments show that C₂N is toxic to human umbilical vein/vascular endothelium cells. The further combined experimental and theoretical studies unravel that the cytotoxicity of C₂N mainly originates from its oxidative capability toward the antioxidant molecules, leading to excessive accumulation of reactive oxygen species in cells. Compared with graphene oxide, C₂N exerts a relatively milder cytotoxicity, and importantly, this novel material shows negligible physical destruction effects on cell membranes, suggesting that C₂N might be a potential alternative to graphene and its derivatives in biomedical research. This work sheds light on the cytotoxicity of C₂N nanosheets and the underlying mechanism, which is crucial for the future utilization of this 2D nanomaterial in related biomedical fields.

Molecular dynamics simulations reveal the mechanism of graphene oxide nanosheet inhibition of Aβ1–42 peptide aggregation

Graphene oxide nanosheets inhibit Aβ1–42 aggregation by weakening inter-peptide interactions and reducing β-sheet contents mostly via salt bridge, hydrogen bonding and cation–π interactions with charged residues.