Oxidative Skin Research Articles

HPLC-DAD phenolics screening and in vitro investigation of haemostatic, antidiabetic, antioxidant and photoprotective properties of Centaurea tougourensis Boiss. & Reut.

Summary Introduction Traditional medicine has an important place in human history and this since antiquity. Indeed, during Egyptian and Chinese civilization era, many detailed manuscripts, describing the therapeutic effect of plants, were found which suggest that folk medicine is the basis of the actual medicine. Objective To investigate the phytochemical and pharmacological properties of the n-butanol (n-BuOH) and ethyl acetate (EA) extracts of the aerial part of Centaurea tougourensis. Methods The phytochemical evaluation was done based on HPLC-DAD approach. The antioxidant activity was determined by DPPH and cupric ion reducing antioxidant capacity (CUPRAC), while the hemostatic effect was performed using plasma recalcification time (PRT) method. The antidiabetic capacity was investigated by alpha-amylase inhibition assay and the photoprotective test was evaluated by the measurement of sun protection factor (SPF). Results 13 phenolic compounds were identified in both extracts of C. tougourensis. These extracts showed antioxidant, haemostatic, antidiabetic and photoprotective properties with a dose-dependent manner. Amounts of n-BuOH activities were found higher, with a respective IC50 value of 0.72±0.07 μg/ml in DPPH assay, an A0.50 value lower than 3.125 μg/ml in CUPRAC assay besides a shortening rate percentage of coagulation (86.71%) in haemostatic assay, a moderate inhibition effect on alpha amylase activity with an IC50 value of (711.5±0.03 μg/ml) and a maximum sun protection factor of (56.035). These results were mostly found highly significant (p<0.001) when compared to respective standards. Conclusion This study demonstrated some pharmacological effects of C. tougourensis which suggests that our plant could be a good candidate to treat some illnesses related to oxidative stress, bleeding or skin cancer.

Liquid metal enabled continuous flow reactor: A proof-of-concept

Liquid metal enabled continuous flow reactor: A proof-of-concept

Simulation on Influence of Wall Thickness and Probe Channel Numbers on the Examination Rate of Oxides Blocking Ratio in non-Ferromagnetic Tubes

Oxides accumulated in the inner bend of austenite heating tubes of super critical units may cause overheat and bursting. Traditional methods could not examine oxides blocking ratio. A magnetic field simulation of the boiler tube’s oxide skin blockage model has been set up in this paper. The influence of different wall thickness and different accumulation of oxide on the distribution of magnetic field was analyzed. It was demonstrated that the blockage oxide scale could be quantitatively measured by the amplitude and distribution of magnetic field.

NMN recruits GSH to enhance GPX4-mediated ferroptosis defense in UV irradiation induced skin injury

Oxidative stress and lipid peroxidation are major causes of skin injury induced by ultraviolet (UV) irradiation. Ferroptosis is a form of regulated necrosis driven by iron-dependent peroxidation of phospholipids and contributes to kinds of tissue injuries. However, it remains unclear whether the accumulation of lipid peroxides in UV irradiation-induced skin injury could lead to ferroptosis. We generated UV irradiation-induced skin injury mice model to examine the accumulation of the lipid peroxides and iron. Lipid peroxides 4-HNE, the oxidative enzyme COX2, the oxidative DNA damage biomarker 8-OHdG, and the iron level were increased in UV irradiation-induced skin. The accumulation of iron and lipid peroxidation was also observed in UVB-irradiated epidermal keratinocytes without actual ongoing ferroptotic cell death. Ferroptosis was triggered in UV-irradiated keratinocytes stimulated with ferric ammonium citrate (FAC) to mimic the iron overload. Although GPX4 protected UVB-injured keratinocytes against ferroptotic cell death resulted from dysregulation of iron metabolism and the subsequent increase of lipid ROS, keratinocytes enduring constant UVB treatment were markedly sensitized to ferroptosis. Nicotinamide mononucleotide (NMN) which is a direct and potent NAD+ precursor supplement, rescued the imbalanced NAD+/NADH ratio, recruited the production of GSH and promoted resistance to lipid peroxidation in a GPX4-dependent manner. Taken together, our data suggest that NMN recruits GSH to enhance GPX4-mediated ferroptosis defense in UV irradiation-induced skin injury and inhibits oxidative skin damage. NMN or ferroptosis inhibitor might become promising therapeutic approaches for treating oxidative stress-induced skin diseases or disorders.

What Are Reactive Oxygen Species, Free Radicals, and Oxidative Stress in Skin Diseases?

Oxygen in the atmosphere is a crucial component for life-sustaining aerobic respiration in humans. Approximately 95% of oxygen is consumed as energy and ultimately becomes water; however, the remaining 5% produces metabolites called activated oxygen or reactive oxygen species (ROS), which are extremely reactive. Skin, the largest organ in the human body, is exposed to air pollutants, including diesel exhaust fumes, ultraviolet rays, food, xenobiotics, drugs, and cosmetics, which promote the production of ROS. ROS exacerbate skin aging and inflammation, but also function as regulators of homeostasis in the human body, including epidermal keratinocyte proliferation. Although ROS have been implicated in various skin diseases, the underlying mechanisms have not yet been elucidated. Current knowledge on ROS-related and oxidative stress-related skin diseases from basic research to clinical treatment strategies are discussed herein. This information may be applied to the future treatment of skin diseases through the individual targeting of the ROS generated in each case via their inhibition, capture, or regulation.

Protective Effects of Linearthin and Other Chalcone Derivatives from Aspalathus linearis (Rooibos) against UVB Induced Oxidative Stress and Toxicity in Human Skin Cells.

Skin cells suffer continuous damage from chronic exposure to ultraviolet light (UV) that may result in UV-induced oxidative stress and skin thinning. This has necessitated the formulation of cosmeceutical products rich in natural antioxidants and free radical scavengers. Aspalathus linearis (rooibos) is an endemic South African fynbos plant growing naturally in the Western Cape region. The plant is rich in phenolics and other bioactives with a wide spectrum of health benefits. The chemical study of an acetonic extract of green A. linearis afforded a novel compound named linearthin (1) and two known dihydrochalcones, aspalathin (2) and nothofagin (3). The chemical structure of the novel compound was elucidated based on spectroscopic data analysis. The bio-evaluation of the isolated chalcones in vitro for protection against UVB-induced oxidative stress were systematically assessed by examining cell viability, metabolic activity, apoptosis, and cytotoxicity using HaCaT and SK-MEL-1 skin cells models. It was observed that pre-treatment with tested samples for 4- and 24 h at low concentrations were sufficient to protect skin cells from UVB-induced damage in vitro as evidenced by higher cell viability and improved metabolic activity in both keratinocytes (HaCaT) and melanocytes (SK-MEL-1). The results further show that the pre-treatment regimen employed by this study involved some degree of cellular adaptation as evidenced by higher levels of reduced glutathione with a concomitant decrease in lipid peroxidation and lowered caspase 3 activity. Furthermore, compound 1 was most cytoprotective against UVB irradiation of HaCaT cell line (over 24 h) with an IC50 of 282 µg/mL and SK-MEL-1 cell line with IC50 values of 248.3 and 142.6 µg/mL over 4 and 24 h, respectively. On the other hand, HaCaT cells exposed to 2 over 4 h before UVB irradiation showed the highest degree of cytoprotection with an IC50 of 398.9 µg/mL among the four studied samples. These results show that linearthin (1) and the two glycoside dihydrochalcone of A. linearis have the potential to be further developed as antioxidant cosmeceutical ingredients that may protect skin against UVB-induced damage.

Revisiting the Chemical Stability of Germanium Selenide (GeSe) and the Origin of its Photocatalytic Efficiency

AbstractRecently, germanium selenide (GeSe) has emerged as a promising van der Waals semiconductor for photovoltaics, solar light harvesting, and water photoelectrolysis cells. Contrary to previous reports claiming perfect ambient stability based on experiments with techniques without surface sensitivity, here, by means of surface‐science investigations and density functional theory, it is demonstrated that actually both: i) the surface of bulk crystals; and ii) atomically thin flakes of GeSe are prone to oxidation, with the formation of self‐assembled germanium‐oxide skin with sub‐nanometric thickness. Surface oxidation leads to the decrease of the bandgap of stoichiometric GeSe and GeSe1−x, while bandgap energy increases upon surface oxidation of Ge1−xSe. Remarkably, the formation of a surface oxide skin on GeSe crystals plays a key role in the physicochemical mechanisms ruling photoelectrocatalysis: the underlying van der Waals semiconductor provides electron–hole pairs, while the germanium‐oxide skin formed upon oxidation affords the active sites for catalytic reactions. The self‐assembled germanium‐oxide/germanium‐selenide heterostructure with different bandgaps enables the activation of photocatalytic processes by absorption of light of different wavelengths, with inherently superior activity. Finally, it is discovered that, depending on the specific solvent‐GeSe interaction, the liquid phase exfoliation of bulk crystals can induce the formation of Se nanowires.

Oat (Avena sativa) Extract against Oxidative Stress-Induced Apoptosis in Human Keratinocytes.

Oat (Avena sativa) is well known for its various health benefits. The protective effect of oat extract against oxidative stress-induced apoptosis in human keratinocytes HaCaT was determined. First, extracts of two varieties of oat, Daeyang and Choyang, were analyzed for fat-soluble antioxidants such as α-tocotrienol, γ-oryzanols, lutein and zeaxanthin using an UPLC system and for antioxidant activity using a DPPH assay. Specifically, an 80% ethanol extract of Daeyang oat (Avena sativa cv. Daeyang), which had high amounts of antioxidants and potent radical scavenging activity, was further evaluated for protective effect against oxidative stress-induced cell death, intracellular reactive oxygen species levels, the phosphorylation of DNA damage mediating genes such as H2AX, checkpoint kinase 1 and 2, and p53 and the activation of apoptotic genes such as cleaved caspase-3 and 7 and poly (ADP-ribose) polymerase in HaCaT cells. The Daeyang and Choyang oat 80% ethanol extracts had 26.9 and 24.1 mg/100 g γ-oryzanols, 7.69 and 8.38 mg/100 g α-tocotrienol, 1.25 and 0.34 mg/100 g of lutein and 1.20 and 0.17 mg/100 g of zeaxanthin, respectively. The oat 80% ethanol extract treatment (Avena sativa cv. Daeyang) had a protective effect on oxidative stress-induced cell death in HaCaT cells. In addition, the oat 80% ethanol extracts led to a significant decrease in the intracellular ROS level at a concentration of 50–200 μg/mL, the attenuation of DNA damage mediating genes and the inhibition of apoptotic caspase activities in a dose dependent manner (50–200 μg/mL). Thus, the current study indicates that an oat (Avena sativa cv. Daeyang) extract rich in antioxidants, such as polyphenols, avenanthramides, γ-oryzanols, tocotrienols and carotenoids, has a protective role against oxidative stress-induced keratinocyte injuries and that oat may a useful source for oxidative stress-associated skin damage.

Crack on the Inner Rim Flange of an Aluminum Rim

Abstract The aluminum rim of a passenger car was claimed by the customer because a crack had appeared on the inner rim flange, which ran into the rim well. The cause of this damage was to be determined. Accumulations of oxide skins in areas close to the surface were proven to be the cause of failure by metallographic and scanning electron microscopic examinations. The cause of the damage was a manufacturing defect.

Thermodynamic analysis of graphene CVD grown on liquid metal: Growth on liquid metallic gallium or solid gallium oxide skin?

A number of recent publications have reported liquid gallium to have an extraordinary catalytic activity for chemical vapor deposition (CVD) of graphene, enabling the growth of high-quality graphene on its surface even below 600 K. Our presented thermodynamic analysis however, indicates that during several of these experiments, an atomically thin gallium oxide layer should have covered the liquid gallium. This means that graphene should have actually grown on the solid oxide skin rather than on the liquid metal. This suggests a more complex mechanism for graphene growth on liquid gallium than what is currently considered in the community.

Kaempferol Blocks the Skin Fibroblastic Interleukin 1β Expression and Cytotoxicity Induced by 12-O-tetradecanoylphorbol-13-acetate by Suppressing c-Jun N-terminal Kinase.

Kaempferol, a bioflavonoid present in fruits and vegetables, has a variety of antioxidant and anti-inflammatory capacities, but the functional role of kaempferol in oxidative skin dermal damage has yet to be well studied. In this study, we examine the role of kaempferol during the inflammation and cell death caused by 12-O-tetradecanoylphorbol-13-acetate (TPA) in normal human dermal fibroblasts (NHDF). TPA (5 μM) significantly induced cytotoxicity of NHDF, where a robust increase in the interleukin (IL)-1β mRNA among the various pro-inflammatory cytokines. The skin fibroblastic cytotoxicity and IL-1β expression induced by TPA were significantly ameliorated by a treatment with 100 nM of kaempferol. Kaempferol blocked the production of the intracellular reactive oxygen species (ROS) responsible for the phosphorylation of c-Jun N-terminal kinase (JNK) induced by TPA. Interestingly, we found that kaempferol inhibited the phosphorylation of nuclear factor-kappa B (NF-κB) and the inhibitor NF-κB (IκBα), which are necessary for the expression of cleaved caspase-3 and the IL-1β secretion in TPA-treated NHDF. These results suggest that kaempferol is a functional agent that blocks the signaling cascade of the skin fibroblastic inflammatory response and cytotoxicity triggered by TPA.

Nanotip Formation from Liquid Metals for Soft Electronic Junctions.

Liquid metals and alloys with high-aspect-ratio nanodimensional features are highly sought-after for emerging electronic applications. However, high surface tension, water-like fluidity, and the existence of self-limiting oxides confer specific peculiarities to their characteristics. Here, we introduce a high accuracy nanometric three-dimensional pulling and stretching method to fabricate liquid-metal-based nanotips from room- or near-room-temperature gallium-based alloys. The pulling rate and step size were controlled with a resolution of up to 10 nm and yielded different nanotip morphologies and lengths as a function of the base liquid metal alloy composition and the pulling parameters. The obtained nanotips presented high aspect ratios over lengths of a few microns and apexes between 10 and 100 nm. The liquid metal alloys were found confined within nanotips with about 10 nm apexes when vertically pulled at 100 nm/s. An amorphous gallium oxide skin was shown to cover the surface of the nanotips, while the liquid core was composed of the initial liquid metal alloys. The electrical contact established at the nanotips was characterized under dynamic conditions. The liquid metal nanotips showed an Ohmic resistance when a continuous liquid metal channel was formed, and a controllable semiconductor state corresponding to a heterojunction formed at the junction between the liquid metal phase and the gallium oxide semiconductor skin. The variable threshold voltages of the heterojunction were controlled via stretching of the nanotips with a 10 nm step resolution. The liquid metal nanotips were also used for establishing soft electronic junctions. This novel method of liquid metal nanotip fabrication with Ohmic and semiconducting behaviors will lead to exciting avenues for developing electronic and sensing devices.

Oxidative stress in the skin: Impact and related protection.

Skin, our first interface to the external environment, is subjected to oxidative stress caused by a variety of factors such as solar ultraviolet, infrared and visible light, environmental pollution, including ozone and particulate matters, and psychological stress. Excessive reactive species, including reactive oxygen species and reactive nitrogen species, exacerbate skin pigmentation and aging, which further lead to skin tone unevenness, pigmentary disorder, skin roughness and wrinkles. Besides these, skin microbiota are also a very important factor ensuring the proper functions of skin. While environmental factors such as UV and pollutants impact skin microbiota compositions, skin dysbiosis results in various skin conditions. In this review, we summarize the generation of oxidative stress from exogenous and endogenous sources. We further introduce current knowledge on the possible roles of oxidative stress in skin pigmentation and aging, specifically with emphasis on oxidative stress and skin pigmentation. Meanwhile, we summarize the science and rationale of using three well-known antioxidants, namely vitamin C, resveratrol and ferulic acid, in the treatment of hyperpigmentation. Finally, we discuss the strategy for preventing oxidative stress-induced skin pigmentation and aging.

Formulation and Evaluation of Mangosteen (Garcinia mangostana L.) Fruit Pericarp Extract Gel

The topical antioxidant product may be useful for the treatment of oxidative stress-related skin disorder. This research aimed to evaluate a topical gel formulation of Garcinia mangostana L. fruit pericarp (GMP) extract. GMP extract was formulated into a gel and characterized for its physical properties. The antioxidant activity was evaluated based on the radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity. The ability of gel formulation to release GMP extract and promote skin delivery was estimated based on DPPH scavenging method and also compared to that of suspension form. The results showed that the GMP extract gel showed characteristics for topical application. The radical DPPH scavenging activity was confirmed both in GMP extract and GMP extract gel. In vitro study release showed that the GMP extract was released from gel. Some degree of GMP extract was also delivered into the shed snakeskin in vitro. When compared with the suspension form, GMP extract gel provided a more profoundly lower release.

Syringaresinol derived from Panax ginseng berry attenuates oxidative stress-induced skin aging via autophagy

BackgroundIn aged skin, reactive oxygen species (ROS) induces degradation of the extracellular matrix (ECM), leading to visible aging signs. Collagens in the ECM are cleaved by matrix metalloproteinases (MMPs). Syringaresinol (SYR), isolated from Panax ginseng berry, has various physiological activities, including anti-inflammatory action. However, the anti-aging effects of SYR via antioxidant and autophagy regulation have not been elucidated. MethodsThe preventive effect of SYR on skin aging was investigated in human HaCaT keratinocytes in the presence of H2O2, and the keratinocyte cells were treated with SYR (0–200 μg/mL). mRNA and protein levels of MMP-2 and -9 were determined by real-time PCR and Western blotting, respectively. Radical scavenging activity was researched by 2,2 diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. LC3B level was assessed by Western blotting and confocal microscopy. ResultsSYR significantly reduced gene expression and protein levels of MMP-9 and -2 in both H2O2-treated and untreated HaCaT cells. SYR did not show cytotoxicity to HaCaT cells. SYR exhibited DPPH and ABTS radical scavenging activities with an EC50 value of 10.77 and 10.35 μg/mL, respectively. SYR elevated total levels of endogenous and exogenous LC3B in H2O2-stimulated HaCaT cells. 3-Methyladenine (3-MA), an autophagy inhibitor, counteracted the inhibitory effect of SYR on MMP-2 expression. ConclusionSYR showed antioxidant activity and up-regulated autophagy activity in H2O2-stimulated HaCaT cells, lowering the expression of MMP-2 and MMP-9 associated with skin aging. Our results suggest that SYR has potential value as a cosmetic additive for prevention of skin aging.

Chemotherapeutic and chemopreventive potentials of ρ-coumaric acid – Squid chitosan nanogel loaded with Syzygium aromaticum essential oil

One of the most important trends in chemotherapy is the development of green chemotropic drugs with maximal activity and minimal side effects. The nanoencapsulation of phytochemical oils with natural polymers has been documented as a promising approach to producing nanodrugs with sustainable bioactivity and prolonged stability. In this context, Syzygium aromaticum essential oil (SAEO) and ultrasound-assisted deacetylated chitosan (UCS3) were successfully extracted from clove buds and squid pens, respectively. Grafting of UCS3 by ρ-coumaric acid (ρCA) has been performed to fabricate the ρCACS nanogel which was used for nanoencapsulation of SAEO to yield SAEO-loaded nanogel (ρCACS@SAEO). The findings of spectral, thermal, and morphological analyses have confirmed the success of the formation of new materials and SAEO encapsulation, as well. Based on the findings of the in vitro antimicrobial, antioxidant, and anticancer studies, the nanoencapsulation of SAEO by ρCACS has significantly boosted its chemotherapeutic effects, compared to unencapsulated oil. Therefore, ρCACS@SAEO nanogel could be considered as a multifunctional chemotherapeutic/chemopreventive agent for prevention or therapy of pathologies induced by oxidative stress, microbial infection, and breast and skin cancer.

Antioxidant, anti-tyrosinase and anti-inflammatory activities of 3,5-dihydroxy-4′,7-dimethoxyflavone isolated from the leaves of Alpinia nigra

BackgroundOverexposure to sunlight and high UV radiation leads to uncontrolled melanin production in the skin, leading to hyperpigmentation and inflammatory diseases. Therefore, there is a need to discover safe and highly prospective drugs from natural sources. Previous studies have shown that leaves and rhizome extract of Alpinia nigra possesses antioxidant and anti-inflammatory activities. Among the components of the most bioactive methanol and ethyl acetate extract, flavones seem to be the most promising compound. AimTo evaluate the antioxidant, anti-tyrosinase and anti-inflammatory efficacy of 3,5-dihydroxy-4′,7-dimethoxyflavone (DHDM). MethodsThe flavone DHDM was isolated from A. nigra ethyl acetate leaf extract and characterized by multi spectroscopic techniques. The toxicity of DHDM was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The antioxidant and reactive oxygen species (ROS) inhibitory activity were determined by 2,2-Diphenyl-1-picrylhydrazy (DPPH) assay and by flow cytometry. Further, the anti-tyrosinase activity was evaluated by in silico (molecular docking), fluorescence, and enzyme kinetics studies. The anti-inflammatory activity was demonstrated by western blotting. ResultsThe cell viability assay with DHDM showed no inhibition at ≤200 µM concentration in THP-1 (human macrophage) and ≤80 µM in HaCaT (human keratinocyte) cell lines. Additionally, strong antioxidant properties and reduced ROS generation suggested prevention from oxidative damage and skin aging. Strong binding of DHDM to tyrosinase leading to the conformational change was revealed by fluorescence quenching studies and molecular docking. Further, the anti-tyrosinase activity of the isolated compound was observed at 42.5 µM (IC50). Moreover, DHDM inhibited the expression of anti-inflammatory proteins like TNF-α and NF-κB. ConclusionThe DHDM demonstrates the efficient antioxidant, anti-tyrosinase and anti-inflammatory potential, which could be developed for obtaining a new drug for the management of hyperpigmentation and inflammatory-related diseases.

Surface Tension of the Oxide Skin of Gallium-Based Liquid Metals.

Gallium-based alloys have garnered considerable attention in the scientific community, particularly as they are in an atypical liquid state at and near room temperature. Though physical parameters, such as thermal conductivity, electrical conductivity, viscosity, yield stress, and surface tension, of these alloys are broadly known, the surface tension (surface free energy) of the oxide skin remains intangible due to the high yield stress of the oxide skin. In this article, we propose to employ gradually attenuated vibrations to obtain equilibrium shapes, which are analyzed along the lines of the puddle height method. The surface tension of the oxide skin was determined on quartz glass and liquid metal-phobic diamond coating to be around 350-365 mN/m, thus independent of the substrate surface or employed liquid metal (i.e., eutectic Ga-In (EGaIn) and galinstan). The similarity of the surface tension for different alloys was ascribed to the composition of the oxide skin, which predominantly comprises gallium oxides due to thermodynamic constraints. We envision that this method can also be applied to other liquid metal alloys and liquid metal marble systems facilitating modeling, simulation, and optimization processes.

An Image Quality Evaluation Model for Optical Strip Signal-to-Noise Ratio in the Target Area of High Temperature Forgings

Under the time-varying temperature, the high-temperature radiation of forgings and the change of reflection characteristics of oxide skin on the surface of forgings lead to the difficulty of obtaining images to truly reflect the geometric characteristics of forgings. It is urgent to study the clear and reliable acquisition method of hot forging feature image under time-varying temperature to meet the requirements of visual measurement of hot geometric parameters of forgings. Based on this, this chapter first puts forward the quality evaluation method of forging feature image, which provides guarantee for the accurate evaluation of feature image quality. Furthermore, the factors that affect the image quality, such as the radiation characteristics of forgings and the photographic characteristics of cameras, are analyzed, and the imaging spectrum which can effectively suppress the radiation intensity of forgings is determined. Finally, aiming at the problem that the quality of image acquisition is difficult to guarantee due to the drastic change of radiation intensity of forgings under time-varying temperature, an image acquisition method based on minimum signal-to-noise ratio (SNR) based laser light intensity adaptation is proposed, which significantly improves the definition of feature light strips in forging images at high temperature, and finally realizes the clear acquisition of feature images of large-scale hot forging under time-varying temperature.

Dependence of the effective surface tension of liquid phase eutectic gallium indium on wrinkles of the surface oxide

We investigated the effective surface tension of liquid eutectic gallium indium (EGaIn) with oxide skin. Our visualization of the EGaIn interface during extension and compression indicated the compression causes the wrinkles on the oxide skin, which is then partially smoothed out by extension. We found that the creation of the interface was the combined result of tearing of the oxide skin and the unfolding of oxide wrinkles. Our experiments revealed that the effective surface tension depends on oxide wrinkle, and the value is 0.7 N/m in the absence of wrinkles, but can be as small as ∼0.5 N/m in the presence of surface wrinkles.