Increased oxidative stress with elevated serum thioredoxin level in patients with coronary spastic angina

BACKGROUND

Increased oxidative stress has been implicated in the pathogenesis of coronary vasospasm. Thioredoxin (TRX) is a redox-active protein that is known to be induced by oxidative stress.

HYPOTHESIS

The serum TRX level may be high in patients with coronary vasospasm.

METHODS

The serum TRX level was determined using an enzyme-linked immunosorbent assay in 21 patients with the active stage of coronary spastic angina (CSA), in 18 patients with the inactive stage of CSA (iCSA), in 24 control subjects without coronary artery disease (Control), and in 20 patients with stable effort angina (SEA).

RESULTS

Serum TRX levels (mean +/- standard deviation ng/ml) were significantly higher in CSA (64 +/- 44) than in iCSA (28 +/- 26), in Control (34 +/- 15), and in SEA (36 +/- 16). In contrast, serum alpha-tocopherol levels (mg/g lipids) were significantly lower in CSA (2.8 +/- 0.7) than in Control (4.0 +/- 1.2) and in SEA (3.2 +/- 0.4). Current smoking was significantly more prevalent in CSA (76%) than in any of the other groups. No significant correlation was found between the serum level of TRX and alpha-tocopherol in the study subjects. In nine patients with CSA, the serum TRX level decreased (93 +/- 41 --> 41 +/- 35 ng/ml) and the alpha-tocopherol level increased (2.7 +/- 0.6 --> 3.2 +/- 0.7 mg/g lipids) significantly under medication with calcium entry blockers after an at least 3-month angina-free period.

CONCLUSIONS

Patients with coronary spastic angina had a higher serum TRX level associated with a lower serum level of antioxidant vitamin E, with redox equilibrium appearing to be related to the disease activity of coronary vasospasm in these patients. Oxidative stress may be related to the genesis of coronary vasospasm.

Serum antioxidant and cholesterol levels in patients with different types of cancer

Serum antioxidant (urate, alpha-tocopherol) activity and cholesterol concentration in 142 patients of Indian and Arab (Kuwaitis and other Arabs) origin with different types of cancer (breast, colon, stomach, thyroid, oral, rectal, pancreatic, and renal) were compared to 100 age- and sex-matched control subjects. Values were expressed as medians (interquartile range). Urate concentration was significantly decreased in male patients compared to male controls (P < 0.0001) and in female patients and female breast cancer cases compared to female controls; P < 0.0001 and P = 0.001, respectively. Alpha-tocopherol concentration decreased significantly in total cancer, stomach, colon, rectal, and breast cancer cases than the controls; P < 0.0001, P < 0.0001, P < 0.0001, P = 0.012, and P = 0.022, respectively. Cholesterol concentration decreased significantly in stomach, oral, colon, and total cancer cases compared to the controls; P < 0.0001, P < 0.0001, P = 0.002, and P = 0.012, respectively. Among controls, females had significantly (P < 0.0001) lower concentrations of alpha-tocopherol than males. Among patients, cholesterol, urate, and alpha-tocopherol concentrations decreased significantly in smokers than in nonsmokers; P < 0.0001, P = 0.004, and P = 0.047, respectively. Generally, changes in alpha-tocopherol/cholesterol ratios mimicked changes in alpha-tocopherol concentration. Concentrations of all parameters decreased significantly in male patients compared to male controls. Age was positively associated with all three analytes with respect to the controls. Alpha-tocopherol correlated with cholesterol in cancer patients (r = 0.367; P < 0.0001) and with urate in the controls (r = 0.342; P < 0.0001). The data suggest cancer-related diminished synthesis of cholesterol and, generally, a greater antioxidant burden for alpha-tocopherol than urate in cancer-generated oxidative stress. The increased incidence of pancreatic cancer in Kuwaitis warrants further study.

Green synthesis of Ce2O3 NPs and determination of its antioxidant activity

In this study, the authors presented synthesis of ceria nanoparticles (NPs) by the bio-reduction method and their antioxidative activity. Aqueous extract of Euphorbia (Euphorbia amygdaloides) was used as reducing and stabilising agents. They used aqueous extract of Euphorbia (E. amygdaloides) as reducing and stabilising agent. Ultraviolet-visible (UV-vis) absorption spectroscopy was used to monitor the quantitative formation of ceria NPs. They also addressed the characteristics of the obtained ceria NPs using scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmitting electron microscope (TEM). The synthesised cerium (III) oxide (Ce2O3) NPs were initially noted through visual colour change from colourless pale yellow cerium (III) to light yellow cerium (IV) and further confirmed the band at 345 nm employing UV-vis spectroscopy. The average diameter of the prepared NPs was about 8.6-10.5 nm. In addition, the synthesised Ce2O3 NPs were tested for antioxidant and anti-bacterial activities using ferric reducing antioxidant power, cupric reducing antioxidant capacity, ferrous ions chelating activity, superoxide the anion radical scavenging and 2, 2'-azinobis 3-ethylbenzothiazol to-6-sulphonic acid scavenging activity. It could be concluded that Euphorbia (E. amygdaloides) extract can be used efficiently in the production of potential antioxidant and anti-bacterial Ce2O3 NPs for commercial applications.

α-Tocopherol suppresses hepatic steatosis by increasing CPT-1 expression in a mouse model of diet-induced nonalcoholic fatty liver disease

Aim

Antioxidant therapy for with vitamin E appears to be effective for the treatment of nonalcoholic fatty liver disease　(NAFLD). However, the mechanism of action and optimal therapeutic dosage is unclear. The present study was undertaken to examine whether the effects of α‐tocopherol (α‐Toc) on NAFLD are dose‐dependent in a diet‐induced obese model.

Methods

Male mice were fed standard chow, high‐fat (HF) diet, HF diet with low‐dose, or with high dose of α‐Toc supplementation. Histological findings, triglyceride content, and the levels of protein expression related to fatty acid synthesis/oxidation such as carnitine palmitoyltransferase I (CPT‐1) of liver were evaluated. In addition, 2‐tetradecylglycidic acid (TDGA), a CPT‐1 inhibitor, was administered to mice fed HF diet with low‐dose of α‐Toc. Finally, HepG2 cells in fat‐loaded environment were treated with 0–50 μM α‐Toc.

Results

Treatment of low‐dose of α‐Toc decreased HF‐induced hepatic fat accumulation, but this finding was not observed in treatment of high dose of α‐Toc. HF‐induced reduction of CPT‐1 was attenuated with low‐dose of α‐Toc but not with high dose of α‐Toc. TDGA suppressed the improvement of histological findings in liver induced by low‐dose of α‐Toc treatment. CPT‐1 expression in HepG2 cells increased in response to low‐dose of α‐Toc, but not in high dose.

Conclusions

Dual action of α‐Toc on CPT‐1 protein levels was observed. The effect of vitamin E on NAFLD may be not be dose‐dependent.

Age-dependent increase in α-tocopherol and phytosterols in maize leaves exposed to elevated ozone pollution

Tropospheric ozone is a major air pollutant that significantly damages crop production. Crop metabolic responses to rising chronic ozone stress have not been well studied in the field, especially in C4 crops. In this study, we investigated the metabolomic profile of leaves from two diverse maize (Zea mays) inbred lines and the hybrid cross during exposure to season-long elevated ozone (~100 nl L-1) in the field using free air concentration enrichment (FACE) to identify key biochemical responses of maize to elevated ozone. Senescence, measured by loss of chlorophyll content, was accelerated in the hybrid line, B73 × Mo17, but not in either inbred line (B73 or Mo17). Untargeted metabolomic profiling further revealed that inbred and hybrid lines of maize differed in metabolic responses to ozone. A significant difference in the metabolite profile of hybrid leaves exposed to elevated ozone occurred as leaves aged, but no age-dependent difference in leaf metabolite profiles between ozone conditions was measured in the inbred lines. Phytosterols and α-tocopherol levels increased in B73 × Mo17 leaves as they aged, and to a significantly greater degree in elevated ozone stress. These metabolites are involved in membrane stabilization and chloroplast reactive oxygen species (ROS) quenching. The hybrid line also showed significant yield loss at elevated ozone, which the inbred lines did not. This suggests that the hybrid maize line was more sensitive to ozone exposure than the inbred lines, and up-regulated metabolic pathways to stabilize membranes and quench ROS in response to chronic ozone stress.

Plasma monomeric ApoA1 and high-density lipoprotein bound ApoA1 are markedly decreased and associated with low levels of lipophilic antioxidants in sickle cell disease: A potential new pathway for therapy

Patients with sickle cell disease (SCD) exhibit high levels of reactive oxygen species and low plasma levels of lipophilic antioxidants, which may contribute to end-organ damage and disease sequelae. Apolipoprotein A1, the major apolipoprotein of high-density lipoprotein (HDL), is mainly secreted by the intestine and liver in the form of monomeric ApoA1 (mApoA1) present in plasma. Cholesterol and α-tocopherol are delivered to ApoA1 via the ATP-binding cassette transporter, subfamily A, member 1 (ABCA1). We measured cholesterol, mApoA1, ApoA1, and lipophilic antioxidants in the plasma of 17 patients with SCD and 40 healthy volunteers. Mean HDL cholesterol (-C) levels in SCD patients and healthy subjects were 59.3 and 48.1 mg/dL, respectively, and plasma lutein, zeaxanthin, and α-tocopherol were 64.0%, 68.7%, and 9.1% lower, respectively. To compare SCD to healthy subjects with similar HDL-C, we also performed subgroup analyses of healthy subjects with HDL-C above or below the mean. In SCD, the mApoA1 level was 30.4 μg/mL; 80% lower than 141 μg/mL measured in healthy volunteers with similar HDL-C (56.7 mg/dL). The mApoA1 level was also 38.4% greater in the higher versus lower HDL-C subgroups (p = .002). In the higher HDL-C subgroup, lutein and zeaxanthin transported by HDL were 48.9% (p = .01) and 41.9% (p = .02) higher, respectively, whereas α-tocopherol was 31.7% higher (p = .003), compared to the lower HDL-C subgroup. Plasma mApoA1 may be a marker of the capacity of HDL to capture and deliver liposoluble antioxidants, and treatments which raise HDL may benefit patients with high oxidative stress as exemplified by SCD.

Scientific opinion on the tolerable upper intake level for vitamin E

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the revision of the tolerable upper intake level (UL) for vitamin E. As α-tocopherol is recognised as the only essential form of vitamin E, the Panel restricted its evaluation to α-tocopherol. Systematic reviews of the literature were conducted to assess evidence on priority adverse health effects of excess intake of vitamin E, namely risk of impaired coagulation and bleeding, cardiovascular disease and prostate cancer. The effect on blood clotting and associated increased risk of bleeding is considered as the critical effect to establish an UL for vitamin E. No new evidence has been published that could improve the characterisation of a dose-response. The ULs for vitamin E from all dietary sources, which were previously established by the Scientific Committee on Food, are retained for all population groups, i.e. 300 mg/day for adults, including pregnant and lactating women, 100 mg/day for children aged 1-3 years, 120 mg/day for 4-6 years, 160 mg/day for 7-10 years, 220 mg/day for 11-14 years and 260 mg/day for 15-17 years. A UL of 50 mg/day is established for infants aged 4-6 months and a UL of 60 mg/day for infants aged 7-11 months. ULs apply to all stereoisomeric forms of α-tocopherol. ULs do not apply to individuals receiving anticoagulant or antiplatelet medications (e.g. aspirin), to patients on secondary prevention for CVD or to patients with vitamin K malabsorption syndromes. It is unlikely that the ULs for vitamin E are exceeded in European populations, except for regular users of food supplements containing high doses of vitamin E.

An insight into vitamin E and lipid nutrition of the plains-wanderer Pedionomus torquatus

Vitamin E, as α-tocopherol, is an essential antioxidant protecting the body from free radicals. The vitamin E requirement of managed wildlife species is known to be greater than their wild counterparts, predominantly due to higher dietary lipid content and potentially stressful environments. The plains-wanderer (Pedionomus torquatus, Family Pedionomidae [monotypical]) is a critically endangered, superficially quail-like bird that is the focus of an ongoing captive breeding programme in Australia. It is estimated that plains-wanderers have a high vitamin E requirement (compared with domestic poultry species) to offset a high lipid diet and their naturally flighty temperament. This study therefore aims to gain a greater understanding of the nutritional status and vitamin E requirements of plains-wanderers in managed environments. Total lipid and α-tocopherol intake were quantified for 26 zoo-managed plains-wanderers over a series of diet intake trials in addition to measurement of plasma α-tocopherol and cholesterol concentrations. Plains-wanderers that consumed higher portions of dietary fat had significantly lower circulating α-tocopherol concentrations than birds that consumed lower total dietary fat (p < .001). Additionally, plasma cholesterol concentrations of managed plains-wanderers were found to be significantly greater than all other bird species reviewed, irrespective of Family or feeding type. We also present the first published data quantifying the nutritional makeup of stomach contents of a wild plains-wanderer for use as a potential guide for diet formulation. This study forms a vital foundational insight into the nutritional management of plains-wanderers, but further research is required to understand their dietary habits and cholesterol metabolism.

The effect of the fat to starch ratio in young horses' diet on plasma metabolites, muscle endurance and fear responses

High-starch diets may affect equine hindgut microbiota and increase blood glucose levels, which may cause unwanted physiological changes, but may also elicit behavioural changes such as increased fear reactions. The purpose of the current study was to feed a high starch (300) and low fat (43; HS_LF) or a low starch (60) and high fat (85; LS_HF, g/kg of DM) concentrate within the available commercial range and investigate how muscle endurance and fear reactions of horses respond to different diets. Twenty Danish Warmblood stallions (4 years) were randomly allocated to two treatments: LS_HF (n = 10) and HS_LF (n = 10) for 9 weeks. During the two last weeks, a single step exercise test was performed, and plasma metabolites and blood gases were measured before and after exercise in a 2 × 2 factorial design. The effect of two diets on fearfulness was tested by exposing the horses to novel objects test (T1 and T2). Plasma metabolites was not affected by diets. However, plasma level of glucose post-exercise (4.9) was lower than pre-exercise (5.6 mmol/L; p < 0.001). Similarly, plasma level of insulin post-exercise (4.2) was lower than pre-exercise (13.1 pmol/L; p < 0.001). Plasma level of lactate dehydrogenase (p < 0.001), non-esterified fatty acids (p = 0.002), β-hydroxybutyrate (p = 0.001), and fructosamine (p = 0.01) post-exercise was higher than pre-exercise. Regardless of type of diets, RRR-α-tocopherol was the dominance α-tocopherol stereoisomers in plasma. In conclusion, during aerobic exercise, fat to starch ratio in horse diets within the normal range had no significant effect on plasma metabolites. However, horses fed LS_HF tended to show more investigative behaviour than horses fed HS_LF.

Cosmetic emulsions containing innovative complex coacervates: A cross-sectional study

OBJECTIVE

Vitamin E, in the form of α-tocopherol (TOCO), is an essential lipophilic antioxidant widely used in topical formulations. However, incorporating pure TOCO into skincare products poses significant challenges due to its limited solubility and high sensitivity to heat, light and oxidation. The present cross-sectional study aimed to innovate by encapsulating TOCO using non-animal sustainable biopolymers through complex coacervation and to investigate the interaction of these coacervates with cosmetic emulsions, focusing on their impact on the emulsions' physicochemical properties and stability.

METHODS

TOCO was encapsulated using the complex coacervation technique by combining two biopolymers: fungal chitosan and gum Arabic. The designed microcapsules were incorporated into oil-in-water emulsions containing natural ingredients, and the physicochemical properties as well as the stability of the formulations were evaluated and compared to those of non-encapsulated TOCO emulsions.

RESULTS

Innovative coacervates of the non-animal TOCO complex of 86.8 ± 3.5 μm were developed, achieving a high encapsulation efficiency and loading of 87.0% and 27.2%, respectively. The microcapsules exhibited thermal stability up to a temperature of 220°C and showed improved storage stability of the active ingredient when encapsulated. In particular, 63% of TOCO was retained over 2 months at a temperature of 40°C. Emulsions containing microcapsules showed increased particle size distribution, higher viscosity, and enhanced viscoelastic properties, in accordance with their textural properties. Both emulsions remained stable for a 1-month storage period at a temperature of 40°C, and no noticeable effect of coacervates on the stability of TOCO in the emulsions was observed.

CONCLUSION

This study emphasises the potential of fungal chitosan-gum Arabic coacervates as a sustainable substitute for animal-derived coacervates, demonstrating promising outcomes for the encapsulation of lipophilic actives. When incorporated into cosmetic emulsions, these coacervates enhanced the textural and rheological properties while preserving the TOCO stability over time. These findings suggest that the developed microcapsules offer considerable potential for the development of future skin-care products with enhanced functional properties.

Metabolism of 11'-α- and 11'-γ-Tocomonoenols in HepG2 Cells Favors the γ-Congener and Results Predominantly in Carboxymethylbutyl-Hydroxychromans

SCOPE

Tocomonoenols (T1) are little-known vitamin E derivatives naturally occurring in foods. Limited knowledge exists regarding the cellular uptake and metabolism of α-tocomonoenol (αT1) and none about that of γ-tocomonoenol (γT1).

METHODS AND RESULTS

The study investigates the cytotoxicity, uptake, and metabolism of αT1 and γT1 in HepG2 cells compared to the α- and γ-tocopherols (T) and -tocotrienols (T3). None of the studied tocochromanols are cytotoxic up to 100 µmol L-1. The uptake of the γ-congeners is significantly higher than that of the corresponding α-forms, whereas no significant differences are observed based on the degree of saturation of the sidechain. Carboxymethylbutyl-hydroxychromans (CMBHC) are the predominant short-chain metabolites of all tocochromanols and conversion is higher for γT1 than αT1 as well as for the γ-congeners of T and T3. The rate of metabolism increases with the number of double bonds in the sidechain. The rate of metabolic conversion of the T1 is more similar to tocopherols than to that of the tocotrienols.

CONCLUSION

This is the first evidence that both αT1 and γT1 follow the same sidechain degradation pathway and exert similar rates of metabolism than tocopherols. Therefore, investigation into the biological activities of tocomonoenols is warranted.

Development of α-Tocopherol Loaded PLGA Nanoparticles and Its Evaluation as a Novel Immune Adjuvant

With the continuous development of preventive and therapeutic vaccines, traditional adjuvants cannot provide sufficient immune efficacy and it is of high necessity to develop safe and effective novel nanoparticle-based vaccine adjuvants. α-Tocopherol (TOC) is commonly used in oil-emulsion adjuvant systems as an immune enhancer, yet its bioavailability is limited by poor water solubility. This study aims to develop TOC-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (TOC-PLGA NPs) to explore the potential of TOC-PLGA NPs as a novel nanoparticle-immune adjuvant. TOC-PLGA NPs are prepared by a nanoprecipitation method and their physicochemical properties are characterized. It is shown that TOC-PLGA NPs are 110.8 nm, polydispersity index value of 0.042, and Zeta potential of -13.26 mV. The encapsulation efficiency and drug loading of NPs are 82.57% and 11.80%, respectively, and the cumulative release after 35 days of in vitro testing reaches 47%. Furthermore, TOC-PLGA NPs demonstrate a superior promotion effect on RAW 264.7 cell proliferation compared to PLGA NPs, being well phagocytosed and also promoting antigen uptake by macrophages. TOC-PLGA NPs can strongly upregulate the expression of co-stimulatory surface molecules and the secretion of cytokines. In conclusion, TOC-PLGA NPs can be a novel vaccine adjuvant with excellent biocompatibility and significant immune-enhancing activity.

Dysregulated serum concentrations of fat-soluble vitamins in dogs with chronic enteropathy

BACKGROUND

In inflammatory bowel disease (IBD) of humans, nutrient malabsorption can result in fat-soluble vitamin deficiency, especially of vitamin D. In veterinary species, decreased concentrations of vitamin D are relatively common in dogs with chronic enteropathy (CE), but data on the status of other fat-soluble vitamins (FSVs) is lacking.

OBJECTIVES

Determine the serum concentrations of retinol, vitamin D, and α-tocopherol in dogs with CE compared with healthy dogs and compare clinical, clinicopathologic variables between CE and healthy dogs to detect associations with decreased FSVs concentrations.

ANIMALS

Eighteen client-owned dogs with CE and 33 healthy dogs.

METHODS

Serum 25-hydroxyvitamin D (25[OH]D), serum retinol and α-tocopherol concentrations were compared between groups. Correlations and multiple regression modeling were used to examine the relationship between serum 25(OH)D, retinol, and α-tocopherol concentrations and clinical and clinicopathological variables.

RESULTS

Dogs with low serum albumin concentrations were more likely to have lower 25(OH)D concentrations than dogs with normal serum albumin concentration. Dogs with CE had higher serum concentrations of retinol, and variable α-tocopherol concentrations. The cause of these dysregulated vitamin concentrations is unclear and requires further study.

CONCLUSION AND CLINICAL IMPORTANCE

Dogs with severe forms of CE should be monitored for decreased concentrations of 25(OH)D. Additional studies are needed to evaluate the clinical relevance and the possible benefit of vitamin D supplementation in these patients.

The synergistic effect of α-tocopherol and phloretin-loaded nanoemulsions on improvement of the stability, antioxidant, and tyrosinase inhibitory potentiality

The purpose of this study was to prepare and evaluate the formulation of nanoemulsions (NEs) to encapsulate phloretin (PT) to improve its stability, antioxidant, and tyrosinase inhibitory competence. The aim of this study was to improve the stability, antioxidant, and tyrosinase inhibitory effects of PT via NEs. The formulations were prepared using low energy emulsification method for PT-VE-NEs, α-tocopherol (Vitamin E) and medium chain triglycerides (MCT) were used as the oil phase, and Tween 60 was used as the emulsifier and PEG-400 as the co-emulsifier. The droplet size and zeta potential of oil-in-water NEs were evaluated using dynamic light scattering. The PT-VE-NEs were also characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The mean droplet diameter was 14.85 ± 0.14 nm, with a zeta potential of -2.47 ± 0.51 mV. Fourier transform infrared spectroscopy revealed the formation of molecular interactions in the NEs formulations. PT-VE-NEs size was maintained the same during the in vitro digestion study. The particle size of PT-VE-NE remained stable during in vitro digestion. The addition of VE significantly improved the antioxidant, tyrosinase inhibitory effects, as well as thelion and physical stability of PT-VE-NE. The results revealed that NEs is a promising strategy to improve the functionality and stability of PT and VE. PT-VE-NEs will be applied for the preservation of fruits.

A high fat to vitamin E ratio in the feed protects and improves uptake of the natural form of vitamin E in postweaning calves

In postweaning calves, it is a challenge to maintain the plasma vitamin E level at or above the recommended level (3 µg/mL), which is linked to a good immune response. It has been unclear until now why the provision of solid feed with concentrations below 200 mg/kg feed of vitamin E is ineffective in maintaining the plasma vitamin E level of calves above the recommended plasma level postweaning. The present study was conducted to investigate if a high fat to vitamin E ratio in the concentrate could protect and improve the delivery of the natural form of vitamin E (RRR-α-tocopherol) to calves postweaning. Thirty calves were included in the experiment from 2 weeks preweaning until 2 weeks postweaning (Weeks -2, -1, 0 [weaning], 1, and 2 relative to weaning) and fed one of three concentrates in which lecithin mixture provided the fat supplement: control (77 mg/kg of vitamin E and 4.9% DM of crude fat; CONT), medium level of vitamin E supplemented (147 mg/kg of vitamin E and 7.7% DM of crude fat; MedVE) or high level of vitamin E supplemented (238 mg/kg of vitamin E and 12.4% DM of fat; HiVE). Thus, there was a comparable ratio of fat to vitamin E (520-630) in the three concentrates. During the 2 weeks postweaning, final body weight (92 ± 2 kg), average daily gain (917 ± 51 g/day) and concentrate intake (2.2 ± 0.09 kg/day; mean of treatment ± standard error) were unaffected by treatment and the interaction between treatment and week. There was an interaction between treatment and week for vitamin E intake pre- (p < 0.001) and postweaning (p < 0.001). There was an interaction between treatment and week (p < 0.001) for plasma vitamin E level postweaning, and it was 2.5, 3.1, and 3.8 µg/mL in CONT, MedVE, and HiVE, respectively, at Week 1 postweaning. In addition, plasma vitamin E levels at Week 2 postweaning were 2.6, 3.6 and 4.8 µg/mL in CONT, MidVE and HiVE respectively. The results show that 147 mg/kg of lecithin-protected vitamin E in the concentrate is needed to secure a plasma vitamin E level well above the recommended level. In addition, lecithin-protected vitamin E elevated the plasma level of triglycerides and nonesterified fatty acids.

Processing and interpretation of core-electron XPS spectra of complex plasma-treated polyethylene-based surfaces using a theoretical peak model

Interpretation of X-ray photoelectron spectroscopy (XPS) spectra of complex material surfaces, such as those obtained after surface plasma treatment of polymers, is confined by the available references. The limited understanding of the chemical surface composition may impact the ability to determine suitable coupling chemistries used for surface decoration or assess surface-related properties like biocompatibility. In this work, XPS is used to investigate the chemical composition of various ultra-high-molecular-weight polyethylene (UHMWPE) surfaces. UHMWPE doped with α-tocopherol or functionalised by active screen plasma nitriding (ASPN) was investigated as a model system. Subsequently, a more complex combined system obtained by ASPN treatment of α-tocopherol doped UHMWPE was investigated. Through ab initio orbital calculations and by employing Koopmans' theorem, the core-electron binding energies (CEBEs) were evaluated for a substantial number of possible chemical functionalities positioned on PE-based model structures. The calculated ΔCEBEs showed to be in reasonable agreement with experimental reference data. The calculated ΔCEBEs were used to develop a material-specific peak model suitable for the interpretation of merged high-resolution C 1 s, N 1 s and O 1 s XPS spectra of PE-based materials. In contrast to conventional peak fitting, the presented approach allowed the distinction of functionality positioning (i.e. centred or end-chain) and evaluation of the long-range effects of the chemical functionalities on the PE carbon backbone. Altogether, a more detailed interpretation of the modified UHMWPE surfaces was achieved whilst reducing the need for manual input and personal bias introduced by the spectral analyst.