Antioxidant Activity of Supramolecular Water-Soluble Fullerenes Evaluated by β-Carotene Bleaching Assay

Highly Water-Dispersed Natural Fullerenes Coated with Pluronic Polymers as Novel Nanoantioxidants for Enhanced Antioxidant Activity

Fullerene is a cosmic material with a buckyball-like structure comprising 60 carbon atoms. It has attracted significant interest because of its outstanding antioxidant, antiviral, and antibacterial properties. Natural fullerene (NC60) in shungite meets the demand of biomedical fields to scavenge reactive oxygen species in many diseases. However, its hydrophobicity and poor solubility in water hinder its use as an antioxidant. In this study, highly water-dispersed and stable Pluronic-coated natural fullerene nanoaggregates (NC60/Plu) were prepared from various Pluronic polymers. The water dispersity and stability of NC60 were compared and optimized based on the characteristics of Pluronic polymers including F68, F127, L35, P123, and L81. In particular, NC60 coated with Pluronic F127 at a weight ratio of 1 to 5 showed excellent antioxidant effects both in situ and in vitro. This suggests that the high solubilization of NC60 in Pluronic polymers increases its chance of interacting with reactive oxygen radicals and improves radical scavenging activity. Thus, the optimized NC60/PF127 may be a novel biocompatible antioxidant for treating various diseases associated with oxidative stress.

Preparation of a thermo-responsive drug carrier consisting of a biocompatible triblock copolymer and fullerene

A triblock copolymer (PEG-b-PUEM-b-PMPC; EUM) comprising poly(ethylene glycol) (PEG), thermo-responsive poly(2-ureidoethyl methacrylate) (PUEM), and poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) blocks was synthesized via controlled radical polymerization. PEG and PMPC blocks exhibit hydrophilicity and biocompatibility. The PUEM block exhibits an upper critical solution temperature (UCST). PMPC can dissolve hydrophobic fullerenes in water to form a complex by grinding PMPC and fullerene powders. Fullerene-C₇₀ (C₇₀) and EUM were ground in a mortar and phosphate-buffered saline (PBS) was added to synthesize a water-soluble complex (C₇₀/EUM). C₇₀/EUM has a core-shell-corona structure, whose core is a complex of C₇₀ and PMPC, the shell is PUEM, and corona is PEG. The maximum C₇₀ concentration dissolved in PBS was 0.313 g L^-1 at an EUM concentration of 2 g L^-1. The C₇₀/EUM hydrodynamic radius (R_h) was 34 nm in PBS at 10 °C, which increased due to the PUEM block's UCST phase transition with increasing temperature, and R_h attained a constant value of 38 nm above 36 °C. An anticancer drug, doxorubicin, was encapsulated in the PUEM shell by hydrophobic interactions in C₇₀/EUM at room temperature, which can be released by heating. The generation of singlet oxygen (¹O₂) from C₇₀/EUM upon visible-light irradiation was confirmed using the singlet oxygen sensor green indicator. Water-soluble C₇₀/EUM may be used as a carrier that releases encapsulated drugs when heated and as a photosensitizer for photodynamic therapy.

Topical Artocarpus communis Nanoparticles Improved the Water Solubility and Skin Permeation of Raw A. communis Extract, Improving Its Photoprotective Effect

Antioxidants from plant extracts are often used as additives in skincare products to prevent skin problems induced by environmental pollutants. Artocarpus communis methanol extract (ACM) has many biological effects, such as antioxidant, anti-inflammatory, wound healing, and photoprotective effects; however, the poor water solubility of raw ACM has limited its applications in medicine and cosmetics. Topical antioxidant nanoparticles are one of the drug-delivery systems for overcoming the poor water solubility of antioxidants for increasing their skin penetration. The present study demonstrated that ACM-loaded hydroxypropyl-β-cyclodextrin and polyvinylpyrrolidone K30 nanoparticles (AHP) were successfully prepared and could effectively increase the skin penetration of ACM through changing the physicochemical characteristics of raw ACM, including reducing the particle size, increasing the surface area, and inducing amorphous transformation. Our results also revealed that AHP had significantly better antioxidant activity than raw ACM for preventing photocytotoxicity because the AHP formulation increased the cellular uptake of the ACM in UVB-irradiated HaCaT keratinocytes. In conclusion, our results suggest that AHP may be used as a good topical antioxidant nanoparticle for delivering ACM into deep layers of the skin for preventing UVB-induced skin problems.

Water-soluble C60 fullerene ameliorates astroglial reactivity and TNFa production in retina of diabetic rats

The complications of both first and second types of diabetes mellitus patients are important cause of decline in quality of life and mortality worldwide. Diabetic retinopathy (DR) is a widespread complication that affects almost 60% of patients with prolonged (at least 10–15 years) diabetes. The critical role of glial cells has been shown in retinopathy initiation in the last decades. Furthermore, glial reactivity and inflammation could be key players in early pathogenesis of DR. Despite the large amount of research data, the approaches of effective DR therapy remain unclear. The progress of DR is accompanied by pro-inflammatory and pro-oxidative changes in retinal cells including astrocytes and Muller cells. Glial reactivity is a key pathogenetic factor of various disorders in neural tissue. Fullerene C60 nanoparticles were confirmed for both antioxidant and anti-inflammatory capability. In the presented study glioprotective efficacy of water-soluble hydrated fullerene C60 (C60HyFn) was tested in a STZ-diabetes model during 12 weeks. Exposure of the STZ-diabetic rat group to C60HyFn ameliorated the astrocyte reactivity which was determined via S100β and PARP1 overexpression. Moreover, C60HyFn induced the decrease of TNFα production in the retina of STZ-diabetic rats. By contrast, the treatment with C60HyFn of the normal control rat group didn’t change the content of all abovementioned markers of astrogliosis and inflammation. Thus, diabetes-induced abnormalities in the retina were suppressed via the anti-oxidant, anti-inflammatory and glioprotective effects of C60HyFn at low doses. The presented results demonstrate that C60HyFn can ensure viability of retinal cells viability through glioprotective effect and could be a new therapeutic nano-strategy of DR treatment.

Protective effects of polyvinylpyrrolidone-wrapped fullerene against intermittent ultraviolet-A irradiation-induced cell injury in HaCaT cells

To identify compounds that suppress UV irradiation-induced oxidative stress in the skin, various types of antioxidants have been studied. Polyvinylpyrrolidone-entrapped fullerene (C60/PVP) is known as a powerful antioxidant that exerts a cytoprotective effect against UV irradiation-induced cell injury in human skin cells and skin models. However, the effects of the alternate attractive C60/PVP feature, persistent antioxidant ability, on cytoprotection have rarely been ascertained. In this study we therefore investigated the efficacies of C60/PVP using an intermittently repeated UVA irradiation model wherein human keratinocytes were repeatedly exposed to UVA five times every 1h and compared the cytoprotective effects with those provided by ascorbic acid-2-O-phosphate-disodium salt (APS) and α-tocopherol (α-Toc). Our results demonstrated that C60/PVP yielded prominent cytoprotective effects against intermittently repeated UVA irradiation-induced injuries in a dose-dependent manner and suppressed intracellular superoxide anion radical (O2(-)) generation both during and after the repeated UVA irradiation. Additionally, C60/PVP also repressed the intermittent UVA irradiation-induced apoptosis via suppression of chromatin condensation and caspase-3/7 activation. Furthermore, the observed cytoprotective effects were superior to the effects of the typical antioxidants APS and α-Toc. These data suggest that C60/PVP might function as a potent cosmetic antioxidant against the effects of repeated and prolonged UVA irradiation through its persistent antioxidative property.

In vitro antioxidant assay of medium chain fatty acid rich rice bran oil in comparison to native rice bran oil

The study aimed to evaluate the in vitro antioxidant activity of medium chain fatty acid (MCFA) rich-rice bran oils in comparison with native rice bran oil. Different in vitro methods were used to evaluate the free radical scavenging activity, metal chelation activity, reducing acitivity, ABTS radical scavenging activity, thiobarbituric acid (TBA) value and so on at different concentrations of the oils such as 10-100 μg/mL. Inhibition of lipid peroxidation was evaluated measuring thiobarbituric acid responsive substance (TBARS) and conjugated diene formation. All the oils showed potent antioxidant activity at 100 μg/mL concentration. TBARS formation and conjugated diene formation was lower with MCFA rich oils i.e. the inhibition of lipid peroxidation was more in MCFA rich oils than original rice bran oil. Caprylic acid rich rice bran oil showed maximum antioxidant activity in comparison to capric- and lauric acid rich rice bran oils. Overall the MCFA rich rice bran oils showed to be more potent antioxidant than rice bran oil due to their lower unsaturated fatty acid content.

Pharmacological approaches to the treatment of oxidative stress-induced cardiovascular dysfunctions

Cardiovascular diseases are a growing major global health problem. Our understanding of the mechanisms of pathophysiology of cardiovascular diseases has been gaining significant advances and a wealth of knowledge implicates oxidative stress as a key causative agent. However, to date, most efforts to treat heart failure using conventional antioxidant therapies have been less than encouraging. With increasing incidences of cardiovascular disease in young as well as in aging populations, and the problem of long-term diminishing efficacy of conventional therapeutics, the need for new treatments has never been greater. In this review, [corrected] a variety of therapeutic targets and compounds applied to treat cardiovascular diseases via inhibition of oxidative stress are presented.

Modulation of adenosine receptors by [60]fullerene hydrosoluble derivative in SK-N-MC cells

The most known fullerenes are spherical carbon compounds composed of 60 carbon atoms. C(60) fullerenes have shown biochemical and biomedical properties in the last years such as as blockade of apoptosis and neuroprotection. The nucleoside adenosine has a neuroprotective role mainly due to inhibition of glutamate release, which is a neurotransmitter related to excitotoxicity and cell death. In the present work, we have determined the presence of adenosine receptors in SK-N-MC cells, a neuroepithelioma human cell line, and analyzed the effect of fullerenes in these receptors by using radioligand binding, immunoblotting, and quantitative real time PCR assays. Results demonstrated that SK-N-MC cells endogenously express adenosine receptors. Fullerene exposure of these cells did not affect cell viability measured by MTT reduction assay. However, adenosine A(1) and A(2A) receptors were both increased in SK-N-MC cells after treatment. These results suggest for the first time the modulation of adenosine receptors after C(60) fullerenes exposure.

Main approaches for delivering antioxidant vitamins through the skin to prevent skin ageing

INTRODUCTION

One of the major contributions to skin photoageing and diseases is oxidative stress, caused by UV radiation inducing reactive oxygen and nitrogen species. Successful prophylaxis and therapy would necessitate control of the oxidant/antioxidant balance at the affected site, which can be achieved through the external supply of endogenous antioxidants.

AREAS COVERED

This review discusses possible strategies for dermal delivery of the antioxidant vitamins E and C, as oral supplementation has proved insufficient. These antioxidants have low skin bioavailability, owing to their poor solubility, inefficient skin permeability, or instability during storage. These drawbacks can be overcome by various approaches, such as chemical modification of the vitamins and the use of new colloidal drug delivery systems. New knowledge is included about the importance of: enhancing the endogenous skin antioxidant defense through external supply; the balance between various skin antioxidants; factors that can improve the skin bioavailability of antioxidants; and new delivery systems, such as microemulsions, used to deliver vitamins C and E into the skin simultaneously.

EXPERT OPINION

A promising strategy for enhancing skin protection from oxidative stress is to support the endogenous antioxidant system, with antioxidants containing products that are normally present in the skin.

Super-highly hydroxylated fullerene derivative protects human keratinocytes from UV-induced cell injuries together with the decreases in intracellular ROS generation and DNA damages

Polyhydroxylated fullerenes (fullerenols: C(60)(OH)(n)) are known as the major water-soluble fullerene derivatives which possess particular significance as free radical scavengers or antioxidants in biological systems. Recently, the novel polyhydroxylated fullerene (C(60) (OH)(44)·8H(2)O: SHH-F) was successfully synthesized. In the present study, we investigated the radical-scavenging effects and cytoprotective effects of three types of fullerenols (C(60)(OH)(6-12): LH-F, C(60) (OH)(32-34)·7H(2)O: HH-F, and C(60) (OH)(44)·8H(2)O: SHH-F) on UV-irradiation-induced cell injuries. HH-F and SHH-F exerted hydroxyl-radical scavenging activities as shown by DMPO-spin trap/ESR method, more markedly than LH-F. UVA or UVB irradiation-induced injuries in human skin keratinocytes HaCaT were significantly suppressed by HH-F and SHH-F, but scarcely by LF-H. The cytoprotective effects of SHH-F had a tendency to be superior to that of HH-F. And the cytoprotective effects of SHH-F against UVB-induced injuries were more effective than those of UVA. Irradiation with UVB to HaCaT cells was shown to cause rapid increases in cell-injury-associated symptoms such as intracellular oxidative stress levels, the formation of cyclobutane pyrimidine dimers and chromatin condensation, all of which were repressed by SHH-F. Thus, UVB-induced diverse harmful effects could be prevented by SHH-F, which was suggested to exert the cytoprotective effects through intracellular reactive oxygen species-scavenging in the keratinocytes.

In vitro evaluation of cellular responses induced by stable fullerene C60 medium dispersion

Because of the expansion of the functionalities available for modification of fullerene C60 and its derivatives, their uses are increasing. However, the consequences of fullerene exposure to human health have not been fully studied. In vitro experiments are useful for risk assessment and for understanding potential applications. However, the insolubility of pristine C60 in water makes the in vitro evaluation of cellular responses difficult. To overcome this problem, we prepared a stable and uniform C60-medium dispersion for in vitro examinations. In addition, we examined the effect of the C60-medium dispersion on human keratinocyte HaCaT cells and human lung carcinoma A549 cells to understand the cellular responses induced by exposure to C60. Results indicated that exposure to C60 did not affect cell viability; neither apoptosis nor necrosis were induced, while cell proliferation was inhibited. Furthermore, intracellular oxidative stress was induced by C60 exposure in both HaCaT and A549 cells. Transmission electron microscopy indicated the cellular uptake of C60 aggregates. The results obtained from this study indicate that C60 has oxidative stress induction potential. Further examinations including in vivo studies are necessary for a more accurate evaluation of biological influences by C60.

Mechanisms of bacteriophage inactivation via singlet oxygen generation in UV illuminated fullerol suspensions

Nonenveloped viruses are shown to be inactivated by singlet oxygen ((1)O2) produced in UVA photosensitized aqueous suspensions of a polyhydroxylated fullerene (C60(OH)22-24; fullerol, 40 microM). Experiments were performed with MS2, a ssRNA bacteriophage, as well as two dsDNA phages: PRD1, which has an internal lipid membrane, and T7, which entirely lacks lipids. MS2 was highly susceptible to inactivation, having a rate constant of 0.034 min(-1) with UVA alone, which increased to 0.102 min(-1) with photoactivated fullerol. PRD1 and T7 were not susceptible to UVA alone but were photoinactivated by fullerol with rate constants of 0.026 and 0.035 min(-1), respectively. The role of 1(O)2 was demonstrated by three independent observations: (i) viruses that were insensitive to UVA alone were photoinactivated by rose bengal in the absence of fullerol, (ii) beta-carotene reduced (but did not eliminate) photoinactivation rates, and (iii) singlet oxygen sensor green fluorescence spectroscopy directly detected (1)O2 in UVA illuminated fullerol suspensions. Qualitative evidence is also presented that fullerol aggregates were closely associated with viruses allowing efficient transfer of 1(O)2 to their capsids. Fourier transform infrared spectroscopy revealed significant oxidative modifications to capsid proteins but comparatively minor changes to the DNA and (phospho)lipids. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) suggested (1)O2 induced crosslinking of proteins. Hence, phage inactivation by photoactivated fullerol nanoparticles appears to be caused by cross-linking of capsid protein secondary structures by exogenous (1)O2 and consequentimpairmentof their ability to bind to surface receptors of their bacterial hosts (loss of infectivity) rather than by direct reactions with fullerol.

Photoinduced DNA cleavage by alpha-, beta-, and gamma-cyclodextrin-bicapped C60 supramolecular complexes

Water-soluble supramolecular inclusion complexes of alpha-, beta-, and gamma-cyclodextrin-bicapped C60 (CD/C60) have been investigated for their photoinduced DNA cleavage activities, with the aim to assess the potential health risks of this class of compounds and to understand the effect of host cyclodextrins having different cavity dimensions. Factors such as incubation temperature, irradiation time, and concentration of NADH or CDs/ C60 supramolecular inclusion complexes have been examined. The results show that alpha-, beta-, and gamma-CDs/C60 are all able to cleave double-stranded DNA under visible light irradiation in the presence of NADH. However, a difference in the photoinduced DNA cleavage efficiency is observed, where the cleavage efficiency increases in the order of alpha-, beta-, and gamma-CD/C60. The difference is attributed to the different aggregation behavior of the inclusion complexes in aqueous solution, which is correlated to the cavity dimension of the host cyclodextrin molecules.

NanoGenotoxicology: the DNA damaging potential of engineered nanomaterials

With the rapid expansion in the nanotechnology industry, it is essential that the safety of engineered nanomaterials and the factors that influence their associated hazards are understood. A vital area governing regulatory health risk assessment is genotoxicology (the study of genetic aberrations following exposure to test agents), as DNA damage may initiate and promote carcinogenesis, or impact fertility. Of late, considerable attention has been given to the toxicity of engineered nanomaterials, but the importance of their genotoxic potential on human health has been largely overlooked. This comprehensive review focuses on the reported abilities of metal nanoparticles, metal-oxide nanoparticles, quantum dots, fullerenes, and fibrous nanomaterials, to damage or interact with DNA, and their ecogenotoxicity is also considered. Many of the engineered nanomaterials assessed were found to cause genotoxic responses, such as chromosomal fragmentation, DNA strand breakages, point mutations, oxidative DNA adducts and alterations in gene expression profiles. However, there are clear inconsistencies in the literature and it is difficult to draw conclusions on the physico-chemical features of nanomaterials that promote genotoxicity, largely due to study design. Hence, areas that require that further attention are highlighted and recommendations to improve our understanding of the genotoxic potential of engineered nanomaterials are addressed.

Effects of carboxylic acids on nC60 aggregate formation

The discovery that negatively charged aggregates of C(60) fullerene (nC(60)) are stable in water has raised concerns regarding the potential environmental and health effects of these aggregates. In this work, we show that nC(60) aggregates produced by extended mixing in the presence of environmentally relevant carboxylic acids (acetic acid, tartaric acid, citric acid) have surface charge and morphologic properties that differ from those produced by extended mixing in water alone. In general, aggregates formed in the presence of these acids have a more negative surface charge and are more homogeneous than those produced in water alone. Carboxylic acid identity, solution pH, and sodium ion concentration, which are all intricately coupled, play an important role in setting the measured surface charge. Comparisons between particle sizes determined by analysis of TEM images and those obtained by dynamic light scattering (DLS) indicate that DLS results require careful evaluation when used to describe nC(60) aggregates.

Antioxidant assays for plant and food components

Recently, research on natural antioxidants has become increasingly active in various fields. Accordingly, numerous articles on natural antioxidants, including polyphenols, flavonoids, vitamins, and volatile chemicals, have been published. Assays developed to evaluate the antioxidant activity of plants and food constituents vary. Therefore, to investigate the antioxidant activity of chemical(s), choosing an adequate assay based on the chemical(s) of interest is critical. There are two general types of assays widely used for different antioxidant studies. One is an assay associated with lipid peroxidations, including the thiobarbituric acid assay (TBA), malonaldehyde/high-performance liquid chromatography (MA/HPLC) assay, malonaldehyde/gas chromatography (MA/GC) assay, beta-carotene bleaching assay, and conjugated diene assay. Other assays are associated with electron or radical scavenging, including the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay, ferric reducing/antioxidant power (FRAP) assay, ferrous oxidation-xylenol orange (FOX) assay, ferric thiocyanate (FTC) assay, and aldehyde/carboxylic acid (ACA) assay. In this review, assays used recently were selected for extended discussion, including discussion of the mechanisms underlying each assay and its application to various plants and foods.