Synthesis of Various Water-Soluble G60Derivatives and Their Superoxide-Quenching Activity

Oxidative stress modulating nanomaterials and their biochemical roles in nanomedicine

Many pathological conditions are predominantly associated with oxidative stress, arising from reactive oxygen species (ROS); therefore, the modulation of redox activities has been a key strategy to restore normal tissue functions. Current approaches involve establishing a favorable cellular redox environment through the administration of therapeutic drugs and redox-active nanomaterials (RANs). In particular, RANs not only provide a stable and reliable means of therapeutic delivery but also possess the capacity to finely tune various interconnected components, including radicals, enzymes, proteins, transcription factors, and metabolites. Here, we discuss the roles that engineered RANs play in a spectrum of pathological conditions, such as cancer, neurodegenerative diseases, infections, and inflammation. We visualize the dual functions of RANs as both generator and scavenger of ROS, emphasizing their profound impact on diverse cellular functions. The focus of this review is solely on inorganic redox-active nanomaterials (inorganic RANs). Additionally, we deliberate on the challenges associated with current RANs-based approaches and propose potential research directions for their future clinical translation.

Fullerene derivatives as inhibitors of the SARS-CoV-2 main protease

COVID-19 is an ongoing worldwide pandemic. Even today, there is a need for the development of effective therapeutic agents. SARS-CoV-2 is known as the causative virus of COVID-19, and its main protease is one of the enzymes essential for its growth and is considered a drug discovery target. In this study, we evaluated the inhibitory activities of a variety of fullerene derivatives, including newly synthesized derivatives, against the main protease of SARS-CoV-2. As a result, the malonic acid-type fullerene derivatives showed the strongest inhibitory activity.

Immobilization of Heteroatom-Doped Carbon Dots onto Nonpolar Plastics for Antifogging, Antioxidant, and Food Monitoring Applications

This work presents the facile synthesis of heteroatom-doped fluorescent carbon quantum dots (C-dots), which could serve as an antioxidant. Herein, nitrogen, phosphorous, and sulfur codoped carbon dots (NPSC-dots) have been synthesized by a single-step hydrothermal strategy. Owing to the radical scavenging activity of the NPSC-dots, they were tested against several methods as well as in practical applications. The antioxidant ability of the NPSC-dots was efficiently utilized on plastic films by coating with these NPSC-dots. For the very first time, NPSC-dots were immobilized onto nonpolar plastic films (polypropylene) via photochemical covalent grafting to extend the shelf life of food items or storage without affecting the quality of plastic films. The NPSC-dot-coated PP film with negligible deterioration of transparency was extensively studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) analysis, X-ray photoelectron spectroscopy (XPS), contact angle measurement, and thermogravimetric analysis (TGA). The fluorescent character, antioxidant ability, and durability under different solvent systems of the coated film were examined. Also, the coated films were extensively and rigorously evaluated against simulated drastic environmental conditions to ensure the durability and antifogging application.

Recent advances in ultrathin two-dimensional materials and biomedical applications for reactive oxygen species generation and scavenging

Graphene and graphene-like two-dimensional (2D) nanomaterials, such as black phosphorus (BP), transition metal carbides/carbonitrides (MXene) and transition metal dichalcogenides (TMD), have been extensively studied in recent years due to their unique physical and chemical properties. With atomic-scale thickness, these 2D materials and their derivatives can react with ROS and even scavenge ROS in the dark. With excellent biocompatibility and biosafety, they show great application potential in the antioxidant field and ROS detection for diagnosis. They can also generate ROS under light and be applied in antibacterial, photodynamic therapy (PDT), and other biomedical fields. Understanding the degradation mechanism of 2D nanomaterials by ROS generated under ambient conditions is crucial to developing air stable devices and expanding their application ranges. In this review, we summarize recent advances in 2D materials with a focus on the relationship between their intrinsic structure and the ROS scavenging or generating ability. We have also highlighted important guidelines for the design and synthesis of highly efficient ROS scavenging or generating 2D materials along with their biomedical applications.

Green synthesis of multipurpose carbon quantum dots from red cabbage and estimation of their antioxidant potential and bio-labeling activity

We present a green synthesis of fluorescent carbon quantum dots (CQDs) by using red cabbage (rc) and a one-step hydrothermal approach. The rcCQDs were characterized by various techniques such as UV-visible spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, Fourier-transform infrared spectroscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy. The synthesized rcCQDs exhibited an average size of 3 nm, measured by TEM, blue fluorescence, and a quantum yield of 8.3%. The highest emission band was observed at approximately 402 nm when excited at 330 nm. The rcCQDs exhibited strong antioxidant activities by scavenging 61, 56, and 91% against 2, 2-diphenyl-1-picrylhydrazyl, hydroxyl, and potassium permanganate radicals, respectively. The scavenging activity of rcCQDs was comparable with that of standard antioxidant L-ascorbic acid. Cell Counting Kit (CCK)-8 assay depicted superior bio-compatibility and negligible cytotoxicity of rcCQDs on SH-SY5Y neuroblastoma cells. They were used as a fluorescent probe for bio-labeling of Escherichia coli and Staphylococcus aureus. The viabilities of the labeled bacterial cells were analyzed by AFM and UV-visible spectroscopy. Furthermore, the rcCQDs were utilized as a fluorescent ink, an alternative to pens, and maybe suitable for paints and varnish agents. This study provides detailed mechanistic insights into the antioxidant activity of as-synthesized rcCQDs, which suggest the practical applicability of CQDs for bio-medical applications. Key points • Carbon quantum dots were prepared from red cabbage using the hydrothermal method. • The scavenging activity of rcCQDs was evaluated for DPPH, OH, and KMnO₄radicals. • The rcCQDs were used for the labeling of foodborne bacteria. • The rcCQDs could be utilized as fluorescent ink. Graphical abstract Schematic representation of CQDs prepared from red cabbage (rc) with multifunctional applications.

Sozarukova M, V. Proskurnina E, E. Kareev I, A. Proskurnin M. Non-Functionalized Fullerenes and Endofullerenes in Aqueous Dispersions as Superoxide Scavengers

Endohedral metal fullerene are potential nanopharmaceuticals for MRI; thus, it is important to study their effect on reactive oxygen species (ROS) homeostasis. Superoxide anion radical is one of the key ROS. The reactivity of aqueous dispersions of pristine (non-functionalized) fullerenes and Gd@C₈₂ endofullerene have been studied with respect to superoxide in the xanthine/xanthine oxidase chemiluminescence system. It was found that C₆₀ and C₇₀ in aqueous dispersions react with superoxide as scavengers by a similar mechanism; differences in activity are determined by cluster parameters, primarily the concentration of available, acting molecules at the surface. Gd endofullerene is characterized by a significantly (one-and-a-half to two orders of magnitude) higher reactivity with respect to C₆₀ and C₇₀ and is likely to exhibit nanozyme (SOD-mimic) properties, which can be accounted for by the nonuniform distribution of electron density of the fullerene cage due to the presence of the endohedral atom; however, in the cell model, Gd@C₈₂ showed the lowest activity compared to C₆₀ and C₇₀, which can be accounted for by its higher affinity for the lipid phase.

Antioxidant Graphene Oxide Nanoribbon as a Novel Whitening Agent Inhibits Microphthalmia-Associated Transcription Factor-Related Melanogenesis Mechanism

In the melanin synthesis process, oxidative reactions play an essential role, and it is a good strategy to inhibit melanin production by reducing oxidative stress. Fullerene and its derivatives, or the complexes, were considered as strong free-radical scavengers, and we further applied multilayered sp² nanocarbons to discover melanin synthesis inhibitory mechanisms. In the present study, we used novel nanomaterials, such as multiwalled carbon nanotubes (MWCNTs), short-type MWCNTs, graphene oxide nanoribbons (GONRs), and short-type GONRs, as anti-oxidative agents to regulate melanin production. The results showed that GONRs had better anti-oxidative capabilities in intracellular and extracellular oxidative stress analysis platforms than others. We proposed that GONRs have oxygen-containing functional groups. In the 2',7'-dichlorodihydrofluorescein diacetate assay, we found out GONR could chelate metal ions to scavenge reactive oxygen species. In the molecular insight view, we observed that these nanomaterials downregulated the melanin synthesis by decreasing microphthalmia-associated transcription factor-related gene expressions, and there were similar consequences in protein expressions. To sum up, GONRs is a potential agent as a novel antioxidant and skin-whitening cosmetology material.

Ultrahigh-yield synthesis of N-doped carbon nanodots that down-regulate ROS in zebrafish

Oxidative damage induced by accumulation of excessive reactive oxygen species (ROS) could result in increased chronic inflammation and thus ageing and age-related diseases. Carbonaceous nanodrugs hold great promise for ameliorating age-related diseases, and it is necessary to develop ultrahigh-yield synthesis of such nanodrugs. To improve the synthetic yield (less than 50%) of carbon nanodots (CNDs), the general choice is to screen precursors. However, no reliable concept for improving the yield has been explored over the past few decades. We are the first to propose the concept of using carbon-carbon double bonds to boost the synthetic yield and demonstrate record breaking ultrahigh-yield (85.9%) synthesis of N-doped CNDs. When the C[double bond, length as m-dash]C content increased from 14 to 56 mmol, the synthetic yield exhibited a 3.3-fold increase. Nitrogen elements are doped as pyridinic-like N and NH₂, where conjugated π-systems as electron donors and pyridinic-like structures would benefit the potential down-regulated effect for ROS. N-doped CNDs exhibit an outstanding protective effect against oxidative stress via inhibiting exogenous and endogenous ROS generation, where the ROS in zebrafish are significantly reduced by 68%. Hence the concept of carbon-carbon double bond-boosted ultrahigh-yield synthesis of N-doped CNDs provides a promising strategy to be employed for carbonaceous nanodrugs aiming at preventing and curing ageing and age-related diseases.

Characterization of New Cationic N,N-Dimethyl[70]fulleropyrrolidinium Iodide Derivatives as Potent HIV-1 Maturation Inhibitors

HIV-1 maturation can be impaired by altering protease (PR) activity, the structure of the Gag-Pol substrate, or the molecular interactions of viral structural proteins. Here we report the synthesis and characterization of new cationic N,N-dimethyl[70]fulleropyrrolidinium iodide derivatives that inhibit more than 99% of HIV-1 infectivity at low micromolar concentrations. Analysis of the HIV-1 life cycle indicated that these compounds inhibit viral maturation by impairing Gag and Gag-Pol processing. Importantly, fullerene derivatives 2a-c did not inhibit in vitro PR activity and strongly interacted with HIV immature capsid protein in pull-down experiments. Furthermore, these compounds potently blocked infectivity of viruses harboring mutant PR that are resistant to multiple PR inhibitors or mutant Gag proteins that confer resistance to the maturation inhibitor Bevirimat. Collectively, our studies indicate fullerene derivatives 2a-c as potent and novel HIV-1 maturation inhibitors.

Fullerene Derivatives Strongly Inhibit HIV-1 Replication by Affecting Virus Maturation without Impairing Protease Activity

Three compounds (1, 2, and 3) previously reported to inhibit HIV-1 replication and/or in vitro activity of reverse transcriptase were studied, but only fullerene derivatives 1 and 2 showed strong antiviral activity on the replication of HIV-1 in human CD4(+) T cells. However, these compounds did not inhibit infection by single-round infection vesicular stomatitis virus glycoprotein G (VSV-G)-pseudotyped viruses, indicating no effect on the early steps of the viral life cycle. In contrast, analysis of single-round infection VSV-G-pseudotyped HIV-1 produced in the presence of compound 1 or 2 showed a complete lack of infectivity in human CD4(+) T cells, suggesting that the late stages of the HIV-1 life cycle were affected. Quantification of virion-associated viral RNA and p24 indicates that RNA packaging and viral production were unremarkable in these viruses. However, Gag and Gag-Pol processing was affected, as evidenced by immunoblot analysis with an anti-p24 antibody and the measurement of virion-associated reverse transcriptase activity, ratifying the effect of the fullerene derivatives on virion maturation of the HIV-1 life cycle. Surprisingly, fullerenes 1 and 2 did not inhibit HIV-1 protease in an in vitro assay at the doses that potently blocked viral infectivity, suggesting a protease-independent mechanism of action. Highlighting the potential therapeutic relevance of fullerene derivatives, these compounds block infection by HIV-1 resistant to protease and maturation inhibitors.

A proline-type fullerene derivative inhibits adipogenesis by preventing PPARγ activation

Obesity and its associated metabolic diseases represent some of the most rapidly expanding health issues worldwide, and, thus, the development of a novel chemical compound to suppress adipogenesis is strongly expected. We herein investigated the effects of water-soluble fullerene derivatives: a bis-malonic acid derivative and three types of proline-type fullerene derivatives, on adipogenesis using NIH-3T3 cells overexpressing PPARγ. One of the proline-type fullerene derivatives (P3) harboring three carboxy groups significantly inhibited lipid accumulation and the expression of adipocyte-specific genes, such as aP2, induced by the PPARγ agonist rosiglitazone. On the other hand, the bis-malonic acid derivative (M) and the 2 other proline-type fullerene derivatives (P1, P2), which have two carboxy groups, had no effect on PPARγ-mediated lipid accumulation or the expression of aP2. P3 fullerene also inhibited lipid accumulation induced by the combined stimulation with 3-isobutyl-1-methylxanthine (IBMX), dexamethasone, and insulin in 3T3-L1 preadipocytes. During the differentiation of 3T3-L1 cells into adipocytes, P3 fullerene did not affect the expression of C/EBPδ, C/EBPβ, or PPARγ, but markedly inhibited that of aP2 mRNA. These results suggest that P3 fullerene exhibits anti-obesity activity by preventing the activation of PPARγ.

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Fullerene derivative inhibits the rosiglitazone-induced adipogenesis.

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Fullerene derivative inhibits the rosiglitazone-induced expression of aP2 mRNA.

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Fullerene derivative inhibits adipogenesis of 3T3-L1 preadipocyte.

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Fullerene derivative inhibits the activation of PPARγ in 3T3-L1 preadipocyte.

Antioxidant chemistry of graphene-based materials and its role in oxidation protection technology

Two-dimensional nanomaterials have potential as a new class of antioxidants that combine physical barrier function with ultrahigh surface area for free radical scavenging. This work presents the first measurements of the chemical reactivities of graphene-based materials toward a set of model free radicals and reactive oxygen species using electron paramagnetic resonance spectroscopy (EPR) and sacrificial dye protection assays. Graphene-based materials are shown to protect a variety of molecular targets from oxidation by these species, and to be highly effective as hydroxyl-radical scavengers. When the hydroxyl radical is produced photolytically, the overall antioxidant effect is a combination of preventative antioxidant activity (UV absorption) and ˙OH radical scavenging. Few-layer graphene is more active than monolayer graphene oxide, despite its lower surface area, which indicates that the primary scavenging sites are associated with the sp(2)-carbon network rather than oxygen-containing functional groups. To explain this trend, we propose that GO is a weak hydrogen donor, due to the non-phenolic nature of most OH groups on GO, which reside at basal sp(3)-carbon sites that do not allow for radical resonance stabilization following hydrogen donation. As an example application of graphene antioxidant behavior, we show that encapsulation of TiO2 nanoparticles in graphene nanosacks reduces undesired photo-oxidative damage to nearby organic target molecules, which suggests graphene encapsulation as a new approach to managing adverse environmental or health impacts of redox-active nanomaterials.

Molecular structure, electronic property and vibrational spectroscopy of C24-glycine and Gd@C24-glycine complexes

Structure, electronic property and vibrational spectroscopy of C(24)-glycine and Gd@C(24)-glycine were systematically explored using the hybrid DFT-B3LYP functional. The interaction between empty C(24) cage and the smallest amino acid (glycine) was also investigated. It was found that the glycine molecule is energetically favorable to interact with the Mid-site on the C(24) cage through the amino nitrogen active site, rather than Top-site. The endohedral Gd atom increases the volume of the cage by around 6.7-9.8%. Analysis of frontier molecular orbitals reveals that the Gd@C(24)-glycine has the low-kinetic stability, being consistent with its thermodynamic property reflected by dissociation energy. We also see that the VIE and VEA of empty C(24) cage are slightly affected by absorbed glycine and endohedral Gd atom. Additionally, the assignments of simulated IR spectra are explored. The work may provide a theoretical reference for further application related structurally to potential antitumour activity.

Human immunodeficiency virus-reverse transcriptase inhibition and hepatitis C virus RNA-dependent RNA polymerase inhibition activities of fullerene derivatives

We examined the human immunodeficiency virus-reverse transcriptase and hepatitis C virus RNA-dependent RNA polymerase inhibition activities of cationic, anionic, and amino acid-type fullerene derivatives. Among the fullerene derivatives, the amino acid-type fullerene derivative was the most efficient in human immunodeficiency virus-reverse transcriptase inhibition.

Modulating activity of fullerol C60(OH)22 on doxorubicin-induced cytotoxicity

Paper presents the effects of the newly synthesized fullerol C60(OH)22 on the growth of tumor cells in vitro and its modulating activity on doxorubicin (DOX)-induced cytotoxicity in human breast cancer cell lines. Cell growth inhibition was evaluated by tetrazolium colorimetric WST1 assay. Electron spin resonance (ESR) "trapping" method was used to investigate OH-radical scavenger activity of fullerol during Fenton's reaction. At a range of nanomolar concentrations fullerol induced cell growth inhibition, which was cell line, dose and time dependent. Fullerol also strongly suppressed DOX-induced cytotoxicity at all concentrations regardless the time of fullerol addition. Proanthocyanidins added as single agent to MCF-7 cell culture for 48 h induced low growth inhibition but in combination with DOX strongly decreased DOX cytotoxicity. Fullerol was found to be a potent hydroxyl radical scavenger: the relative intensity of ESR signals of DMPO-hydroxyl radical (DMPO-OH) spin adduct decreased by 88% in the presence of 0.5 microg/ml of fullerol. The obtained results suggest that antiproliferative effect of the fullerol and its protective effect on DOX-induced cytotoxicity might be mediated through hydroxyl-radical scavenger activity of C60(OH)22.

Antibacterial and antiproliferative activity of cationic fullerene derivatives

We examined the antibacterial and antiproliferative activities of alkylated C(60)-bis(N,N-dimethylpyrrolidinium iodide) derivatives. The fullerene derivatives inhibited bacteria and cancer cell growth effectively. However, the fullerene derivatives with a long alkyl chain did not show antibacterial activity.

Respiratory chain inhibition by fullerene derivatives: hydrogen peroxide production caused by fullerene derivatives and a respiratory chain system

Fullerene is a new type of carbon allotrope. We have shown that the fullerene derivative C(60)-bis(N,N-dimethylpyrrolidinium iodide), a regio isomer mixture, inhibited Escherichia coli growth and dioxygen uptake caused by E. coli and glucose. This result indicates that the mechanism of the bacteriostatic effect is the inhibition of energy metabolism. In this study, we isolated two regio isomers of C(60)-bis(N,N-dimethylpyrrolidinium iodide) and studied their effect on E. coli growth and on respiratory chain activity. In dioxygen uptake caused by the inner-membrane and NADH, the effect of fullerene derivatives was biphasic. At low concentrations of both fullerene derivatives, dioxygen uptake was inhibited, whereas at high concentrations, it was increased. At high concentrations, consumed dioxygen was converted to H(2)O(2). An electrochemical study revealed that reduced fullerene derivatives react with dioxygen. This activity was closely related to a redox property of the isomers.

Photo-induced cytotoxicity of malonic acid [C(60)]fullerene derivatives and its mechanism

The biological activities of fullerenes have attracted extensive attention in recent years. The aim of this paper is to study the relation of the photo-induced cytotoxicity of fullerene derivatives to their chemical structures as well as the possible cellular mechanism involved in the photocytotoxicity. Three C(60) derivatives with two to four malonic acid groups (DMA C(60), TMA C(60) and QMA C(60)) were prepared and the cytotoxicity of these compounds against HeLa cells was determined by MTT. Cell cycle was measured by flow cytometry. The results showed that the cytotoxicity of the malonic acid C(60) derivatives was irradiation- and dose-dependent. The sequence of their photo-induced growth inhibition was DMA C(60)>TMA C(60)>QMA C(60). Hydroxyl radical quencher mannitol (10mM) was not able to prevent cells from the damage induced by irradiated DMA C(60). DMA C(60), together with irradiation, was found to have an ability of inducing a decrease in the number of G(1) cells from 63 to 42% and a rise in that of G(2)+M cells from 6 to 26%. These data indicated that the number of malonic acid molecules added to C(60) played an important role in the phototoxicity, and the blockage of cell cycle might be a mechanism of this activity.