Linezolid and fentanyl: An underrecognized drug-to-drug interaction.

WHAT IS KNOWN AND OBJECTIVE: Despite its frequent use in clinical practice, fentanyl's pro-serotonergic effects are underrecognized, especially in combination with linezolid. Life-threatening reactions can occur. CASE SUMMARY: We report a case of serotonin syndrome developed shortly after the initiation of linezolid in a 63-year-old patient in whom selective serotonin reuptake inhibitor therapy was discontinued for the duration of antibiotic therapy. However, fentanyl transdermal patch treatment was inadvertently continued. Noteworthy, 24 hours following discontinuation of linezolid, the patient experienced complete resolution of symptoms. WHAT IS NEW AND CONCLUSION: Fentanyl can increase the intrasynaptic release of serotonin through their effects on y-amino butyric acid and its phenylpiperidine chemical structure. We illustrate the importance of thorough medication reconciliation and review of all potential drug-to-drug interactions when indicating linezolid therapy to ensure patient safety. We believe that our case provides novel observations and insight that could help recognize similar cases in clinical practice.

High Oxidation Stability of Tea Polyphenol-stabilized Highly Crosslinked UHMWPE Under an in Vitro Aggressive Oxidative Condition.

BACKGROUND: Synovial fluid components, especially lipids, can trigger oxidation of ultrahigh-molecular-weight polyethylene (UHMWPE) artificial joint components in vivo. The use of antioxidants such as vitamin E effectively diminishes the oxidative cascade by capturing free radicals and reducing the oxidation potential of UHMWPE implants. Using a thermo-oxidative aging method, we recently found that tea polyphenols can enhance the oxidation resistance of irradiated UHMWPE in comparison with commercial vitamin E. However, it is yet unknown whether tea polyphenols can reduce lipid-induced oxidation. QUESTIONS/PURPOSES: We explored whether tea polyphenol-stabilized UHMWPE would exhibit (1) lower squalene absorption; (2) stronger oxidation resistance; and (3) lower content of free radicals than vitamin E-stabilized UHMWPE under a physiologically-motivated in vitro accelerated-aging model. METHODS: Tea polyphenol (lipid-soluble epigallocatechin gallate [lsEGCG]) and vitamin E were blended with UHMWPE powders followed by compression molding and electron beam irradiation at 100 and 150 kGy. Small cubes (n = 3, 60 mg, 4 × 4 × 4 mm) cut from the blocks were doped in squalene at 60°, 80°, 100°, and 120° C for 2 hours. Gravimetric change of the cubes after squalene immersion was measured to assess absorption. Thin films (n = 3, ∼60 µm) were also microtomed from the blocks and were doped at 120° C for 24 hours. Oxidation induction time (n = 3, 5 mg of material from the cubes) and incipient oxidation temperature (n = 3, thin films) were obtained to determine the oxidation stability. Signal intensity of the free radicals, obtained by electron spin resonance spectroscopy, was used to qualitatively rank the antioxidant ability of vitamin E and lsEGCG. RESULTS: Squalene absorption was comparable between lsEGCG/UHMWPE and vitamin E/UHMWPE at a given temperature and radiation dose. The oxidation induction time of 100 kGy-irradiated UHMWPE was increased with lsEGCG compared with vitamin E except at 120° C. For example, the oxidation induction time value of 100 kGy-irradiated lsEGCG/UHMWPE immersed at 60 C was 25.3 minutes (24.2-27.8 minutes), which was 8.3 minutes longer than that of 100 kGy-irradiated vitamin E/UHMWPE which was 17.0 minutes (15.0-17.1 minutes) (p = 0.040). After squalene immersion at 120° C, the incipient oxidation temperature of 100 and 150 kGy irradiated lsEGCG/UHMWPE was 234° C (227-240° C) and 227° C (225-229° C), which was higher than vitamin E-stabilized counterparts with value of 217° C (214-229° C; p = 0.095) and 216° C (207-218° C; p = 0.040), respectively. The electron spin resonance signal of 150 kGy irradiated lsEGCG/UHMWPE was qualitatively weaker than that of 150 kGy irradiated vitamin E/UHMWPE. CONCLUSIONS: lsEGCG-stabilized UHMWPE demonstrated higher oxidation resistance than vitamin E-stabilized UHMWPE after squalene immersion, likely because lsEGCG donates more protons to eliminate macroradicals than vitamin E. CLINICAL RELEVANCE: Our in vitro findings provide support that lsEGCG may be effective in protecting against oxidation that may be associated with synovial fluid-associated oxidation of highly crosslinked UHMWPE joint replacement components.

Relapse of porphyria cutanea tarda after treatment with phlebotomy or 4-aminoquinoline antimalarials: a meta-analysis.

BACKGROUND: Porphyria cutanea tarda (PCT) is the most common human porphyria. It is caused by hepatic deficiency of uroporphyrinogen decarboxylase activity, which is acquired in the presence of multiple susceptibility factors. PCT presents clinically with cutaneous blistering photosensitivity and is readily treatable with either repeated phlebotomy or 4-aminoquinoline antimalarials. OBJECTIVES: To perform a systematic review and meta-analysis to compare the effectiveness of these quite different treatment approaches, especially on relapse rates (RRs) after achieving remission. METHODS: Published studies that included follow-up for at least 1 year after treatment of PCT were included. The primary study outcome was PCT relapse. Pooled data are reported as the RRs per person-year of follow-up with 95% confidence intervals (CIs). RESULTS: Of 375 articles identified as pertaining to PCT treatment, 12 were eligible for analysis. Of these, five used high-dose 4-aminoquinoline regimens (two combined with phlebotomy and three without phlebotomy), five used low-dose 4-aminoquinoline regimens and three used phlebotomy. RRs during the year after treatment were similar for the high- and low-dose 4-aminoquinoline groups (35-36%) and lower in the phlebotomy group (20%). The pooled RRs with their 95% CIs were 8·6 (3·9-13·3) per 100 person-years in the high-dose 4-aminoquinoline group, 17·1 (8·9-25·3) per 100 person-years in the low-dose 4-aminoquinoline group and 5·1 (0·5-10·6) per 100 person-years in the phlebotomy group. Subgroup and sensitivity analyses showed similar results. CONCLUSIONS: Clinical or biochemical RRs ranged from 5 to 17 per 100 person-years after remission of PCT. Relapses were somewhat more frequent after remission with 4-aminoquinoline regimens than after remission following phlebotomy. Prospective studies are needed to define better how often relapses occur with these treatments after documenting both clinical and biochemical remission of PCT.

Idiopathic Atypical Haemolytic Uraemic Syndrome presenting with acute dystonia.

Hemolytic Uremic Syndrome (HUS), a triad of microangiopathic hemolytic anemia, thrombocytopenia and acute kidney injury. The atypical HUS (aHUS) results from over activation of complement system with formation of micro thrombi and damage to endothelial cells resulting in renal impairment in 50 % and death in 25 %, commonly in untreated patients. We report an intriguing case of aHUS presenting with acute onset of movement disorder and fluctuating delirium.

Effect of silicon on wheat seedlings (Triticum turgidum L.) grown in hydroponics and exposed to 0 to 30 µM Cu.

MAIN CONCLUSION: Aqueous Si limits Cu uptake by a Si-accumulating plant via physicochemical mechanisms occurring at the root level. Sufficient Si supply may alleviate Cu toxicity in Cu-contaminated soils. Little information is available on the role of silicon (Si) in copper (Cu) tolerance while Cu toxicity is widespread in crops grown on Cu-contaminated soils. A hydroponic study was set up to investigate the influence of Si on Cu tolerance in durum wheat (Triticum turgidum L.) grown in 0, 0.7, 7.0 and 30 µM Cu without and with 1.0 mM Si, and to identify the mechanisms involved in mitigation of Cu toxicity. Si supply alleviated Cu toxicity in durum wheat at 30 µM Cu, while Cu significantly increased Si concentration in roots. Root length, photosynthetic pigments concentrations, macroelements, and organic anions (malate, acetate and aconitate) in roots, were also increased. Desorption experiments, XPS analysis of the outer thin root surface (≤100 Å) and µXRF analyses showed that Si increased adsorption of Cu at the root surface as well as Cu accumulation in the epidermis while Cu was localised in the central cylinder when Si was not applied. Copper was not detected in phytoliths. This study provides evidences for Si-mediated alleviation of Cu toxicity in durum wheat. It also shows that Si supplementation to plants exposed to increasing levels of Cu in solution induces non-simultaneous changes in physiological parameters. We propose a three-step mechanism occurring mainly at the root level and limiting Cu uptake and translocation to shoots: (i) increased Cu adsorption onto the outer thin layer root surface and immobilisation in the vicinity of root epidermis, (ii) increased Cu complexation by both inorganic and organic anions such as aconitate and, (iii) limitation of translocation through an enhanced thickening of a Si-loaded endodermis.

Outcomes and Complications of Lead Removal: Can We Establish a Risk Stratification Schema for a Collaborative and Effective Approach?

BACKGROUND: Removal of an entire cardiovascular implantable electronic device is associated with morbidity and mortality. We sought to establish a risk classification scheme according to the outcomes of transvenous lead removal in a single center, with the goal of using that scheme to guide electrophysiology lab versus operating room extraction. METHODS: Consecutive patients undergoing transvenous lead removal from January 2001 to October 2012 at Mayo Clinic were retrospectively reviewed. RESULTS: A total of 1,378 leads were removed from 652 (age 64 ± 17 years, M 68%) patients undergoing 702 procedures. Mean (standard deviation) lead age was 57.6 (58.8) months. Forty-four percent of leads required laser-assisted extraction. Lead duration (P < 0.001) and an implantable cardioverter defibrillator (ICD) lead (P < 0.001) were associated with the need for laser extraction and procedure failure (P < 0.0001 and P = 0.02). The major complication rate was 1.9% and was significantly associated with longer lead duration (odds ratio: 1.2, 95% confidence interval: 1.1-1.3; P < 0.001). High-risk patients (with a >10-year-old pacing or a >5-year-old ICD lead) had significantly higher major events than moderate-risk (with pacing lead 1-10 years old or ICD lead 1-5 years old) and low-risk (any lead ≤1-year-old) patients (5.3%, 1.2%, and 0%, respectively; P < 0.001). CONCLUSIONS: Transvenous lead removal is highly successful, with few serious procedural complications. We propose a risk stratification scheme that may categorize patients as low, moderate, and high risk for lead extraction. Such a strategy may guide which extractions are best performed in the operating room.

Comparative Efficacy of High-Dose Dexamethasone Versus Methylprednisolone in Coronavirus Disease 2019 (COVID-19)-Associated Acute Respiratory Distress Syndrome.

OBJECTIVE: This retrospective (matched paired) clinical trial aimed to compare the efficacy of dexamethasone vs. methylprednisolone at equipotent (high) doses in patients with coronavirus disease 2019 (COVID-19)-associated acute respiratory distress syndrome (ARDS). METHODS: A total of 347 patients with moderate and severe COVID-19-associated ARDS were administered either a high (equipotent) dose of dexamethasone (32 mg) or methylprednisolone (180 mg) for a duration of up to 10 days. All participants received the standard of care for critically ill COVID-19 patients. RESULTS: The primary outcomes included length of stay in the ICU, ICU mortality, and discharge from the hospital. Based on the obtained results, a tendency towards more favorable clinical outcomes concerning the length of stay in the ICU (in the group of patients treated with non-invasive mechanical ventilation (NIV), p<0.05), ICU mortality, and discharge from the hospital (in the group of patients who were intubated, p<0.05) in patients receiving the high dose of dexamethasone compared to those receiving methylprednisolone was observed. CONCLUSION: It appears that severe cases of COVID-19, especially intubated ones, treated with high doses of dexamethasone have a more favorable clinical outcome than the use of equipotent doses of methylprednisolone. However, larger multicenter studies are needed to validate our observations.

Lack of functionally active sweet taste receptors in the jejunum in vivo in the rat.

BACKGROUND: When studied in enterocyte-like cell lines (Caco-2 and RIE cells), agonists and antagonists of the sweet taste receptor (STR) augment and decrease glucose uptake, respectively. We hypothesize that exposure to STR agonists and antagonists in vivo will augment glucose absorption in the rat. MATERIALS AND METHODS: About 30-cm segments of jejunum in anesthetized rats were perfused with iso-osmolar solutions containing 10, 35, and 100 mM glucose solutions (n = 6 rats, each group) with and without the STR agonist 2 mM acesulfame potassium and the STR inhibitor 10 µM U-73122 (inhibitor of the phospholipase C pathway). Carrier-mediated absorption of glucose was calculated by using stereospecific and nonstereospecific (14)C-d-glucose and (3)H-l-glucose, respectively. RESULTS: Addition of the STR agonist acesulfame potassium to the 10, 35, and 100 mM glucose solutions had no substantive effects on glucose absorption from 2.1 ± 0.2 to 2.0 ± 0.3, 5.8 ± 0.2 to 4.8 ± 0.2, and 15.5 ± 2.3 to 15.7 ± 2.7 µmoL/min/30-cm intestinal segment (P > 0.05), respectively. Addition of the STR inhibitor (U-73122) also had no effect on absorption in the 10, 35, and 100 mM solutions from 2.3 ± 0.1 to 2.1 ± 0.2, 7.7 ± 0.5 to 7.2 ± 0.5, and 15.7 ± 0.9 to 15.2 ± 1.1 µmoL/min/30-cm intestinal segment, respectively. CONCLUSIONS: Provision of glucose directly into rat jejunum does not augment glucose absorption via STR-mediated mechanisms within the jejunum in the rat. Our experiments show either no major role of STRs in mediating postprandial augmentation of glucose absorption or that proximal gastrointestinal tract stimulation of STR or other luminal factors may be required for absorption of glucose to be augmented by STR.

Evaluating the Safety and Efficacy of Naloxegol in Critically Ill Opioid-Induced Constipation Patients.

Background Opioid-induced constipation (OIC) has become more common in the intensive care unit (ICU) due to increased opioid utilization. Traditional laxatives often prove ineffective against OIC, leading to the increased utilization of naloxegol. However, further research is needed to confirm naloxegol's effectiveness and safety in critical care. This study aimed to explore the safety and efficacy of this intervention in critically ill OIC patients. Methods A single-center retrospective study was conducted on 353 patients who received one or more doses of naloxegol from January 1, 2019, to June 30, 2020, for OIC at a tertiary care center. The primary endpoint of this study was to evaluate serious adverse events such as reduced analgesic effect, gastrointestinal perforation, seizure, acute myocardial infarction (AMI), or ventricular arrhythmias using Naranjo Scale in critically ill patients. The secondary goal was to assess the efficacy of naloxegol, measured by the time of the first bowel movement. Results The average duration of naloxegol use was three days, with the first bowel movement occurring at an average of 11.3 hours. Furthermore, 59.8% of individuals had their first bowel movement within 20 hours of receiving naloxegol. There was a low level of causality between naloxegol use and adverse events such as gastrointestinal perforation, seizures, AMI, cardiovascular mortality, stroke, and ventricular arrhythmia. Additionally, reduction in analgesia showed no strong relationship with naloxegol use indicated by the Naranjo Scale assessment. Conclusion Naloxegol showed promising safety and efficacy profiles in treating OIC amongst critically ill patients, though our findings require further validation through prospective studies. This research paves the way for further investigation into naloxegol's role in OIC management, emphasizing the necessity of personalized treatment strategies in critical care settings.

Association of periodontal disease with oral lichen planus: A systematic review and meta analysis.

Background: Gingival lesions in oral lichen planus can indirectly increase the risk of plaque-induced periodontal disease when symptoms associated with such lesions hamper the proper oral hygiene maintenance by the patients and can increase the risk of periodontal tissue destruction. This systematic review analyses the existing evidence on the association between oral lichen planus and periodontal disease. Aim: This systematic review of case-control studies aimed to analyse the association between periodontal disease and oral lichen planus. Material and Methods: An electronic database search for randomised controlled trials, experimental studies, case-control studies, and cohort studies published in peer-reviewed Journals in the English language was conducted from the following databases: PubMed, EBSCOHost, Science Open, EMBASE, and Google Scholar. Results: A total of 12,507 were identified on an electronic database search. Only eight studies fulfilled the eligibility criteria and were included for quantitative analysis. A data extraction sheet was prepared, and studies were analysed. Conclusion: Bleeding on Probing and Probing depth were seen to be significantly associated with Oral Lichen Planus. The symptoms in Oral Lichen Planus impede efficient oral hygiene maintenance by a patient and predispose them to the occurrence of long-term Periodontal Disease.

Expression of tyrosinase gene in gingiva: A pilot study.

Background: Melanin is the predominant pigment responsible for the color of skin, hair, iris of eyes, and oral mucosa. Tyrosinase (TYR) is the key enzyme involved in melanin synthesis. Studies in dermatology have shown a positive correlation between TYR enzyme levels and melanin pigmentation of the skin. However, no study has been conducted to assess TYR levels in the gingiva. Hence the present study was conducted to assess TYR levels in gingival melanin hyperpigmentation. Aim: To assess the TYR gene expression in gingiva in individuals with moderate to severe gingival melanin hyperpigmentation. Methodology: Subjects with a chief complaint of blackish appearance of gums with an unesthetic smile were included in the study. Informed consent was obtained. Scaling and root planning were done and subjects were recalled after 2 weeks. The gingival depigmentation procedure was performed using the conventional scalpel technique under adequate local anesthesia. The selected sites underwent conventional gingival depigmentation technique using Bard-Parker handle no: 3 and blade no: 11. The excised layer of epithelium along with a thin layer of underlying connective was sent to the laboratory to assess the TYR gene expression by real-time polymerase chain reaction technique. Results: The levels of the TYR enzyme activity in the gingival tissues from the selected sites were assessed. Table 1 and Graph 1 show the levels of TYR enzyme gene expression in the gingival tissue. Conclusion: TYR gene expression and the degree of gingival melanin hyperpigmentation are positively correlated. Hence the assessment of TYR enzyme activity in gingiva could be of great value in today's cosmetologically conscious individuals.

Tomato paste rich in lycopene protects against cutaneous photodamage in humans in vivo: a randomized controlled trial.

BACKGROUND: Previous epidemiological, animal and human data report that lycopene has a protective effect against ultraviolet radiation (UVR)-induced erythema. OBJECTIVES: We examined whether tomato paste--rich in lycopene, a powerful antioxidant--can protect human skin against UVR-induced effects partially mediated by oxidative stress, i.e. erythema, matrix changes and mitochondrial DNA (mtDNA) damage. METHODS: In a randomized controlled study, 20 healthy women (median age 33 years, range 21-47; phototype I/II) ingested 55 g tomato paste (16 mg lycopene) in olive oil, or olive oil alone, daily for 12 weeks. Pre- and postsupplementation, UVR erythemal sensitivity was assessed visually as the minimal erythema dose (MED) and quantified with a reflectance instrument. Biopsies were taken from unexposed and UVR-exposed (3 × MED 24 h earlier) buttock skin pre- and postsupplementation, and analysed immunohistochemically for procollagen (pC) I, fibrillin-1 and matrix metalloproteinase (MMP)-1, and by quantitative polymerase chain reaction for mtDNA 3895-bp deletion. RESULTS: Mean ± SD erythemal D(30) was significantly higher following tomato paste vs. control (baseline, 26·5 ± 7·5 mJ cm(-2); control, 23 ± 6·6 mJ cm(-2); tomato paste, 36·6 ± 14·7 mJ cm(-2); P = 0·03), while the MED was not significantly different between groups (baseline, 35·1 ± 9·9 mJ cm(-2); control, 32·6 ± 9·6 mJ cm(-2); tomato paste, 42·2 ± 11·3 mJ cm(-2)). Presupplementation, UVR induced an increase in MMP-1 (P = 0·01) and a reduction in fibrillin-1 (P = 0·03). Postsupplementation, UVR-induced MMP-1 was reduced in the tomato paste vs. control group (P = 0·04), while the UVR-induced reduction in fibrillin-1 was similarly abrogated in both groups, and an increase in pCI deposition was seen following tomato paste (P = 0·05). mtDNA 3895-bp deletion following 3 × MED UVR was significantly reduced postsupplementation with tomato paste (P = 0·01). CONCLUSIONS: Tomato paste containing lycopene provides protection against acute and potentially longer-term aspects of photodamage.

Differentiating passive from transporter-mediated uptake by PepT1: a comparison and evaluation of four methods.

BACKGROUND: To quantify transmembrane transport of dipeptides by PepT1, passive uptake (non-PepT1 mediated) must be subtracted from total (measured) uptake. Three methods have been described to estimate passive uptake: perform experiments at cold temperatures, inhibit target dipeptide uptake with a greater concentration of a second dipeptide, or use modified Michaelis-Menten kinetics. We hypothesized that performing uptake experiments at pH 8.0 would estimate passive uptake accurately, because PepT1 requires a proton gradient. Our aim was to determine the most accurate method to estimate passive uptake. METHODS: Caco-2 cells were incubated with various concentrations of glycyl-sarcosine (gly-sar) at pH 6.0 and at 37°C to measure total uptake. Passive uptake was estimated: (1) by incubating Caco-2 cells with varying concentrations of gly-sar at 4°C, (2) in the presence of 50 mM glycyl-leucine, (3) in solution at pH 8.0, or (4) using modified Michaelis-Menten kinetics. PepT1-mediated uptake was calculated by subtracting passive uptake from total uptake. K(m), V(max), and % gly-sar transported by PepT1 were calculated and compared. RESULTS: K(m), V(max), and % gly-sar transported by PepT1 varied from 0.7 to 2.4 mM, 8.4 to 21.0 nmol/mg protein/10 min, and 69% to 87%, respectively. Uptakes calculated with cold, 50 mM gly-leu and using modified Michaelis-Menten kinetics were similar but differed significantly from uptake at pH 8.0 (P < 0.001). CONCLUSIONS: Estimating passive uptake at pH 8.0 does not appear to be accurate. Measuring uptake at cold temperatures or in the presence of a greater concentration of a second dipeptide, and confirming results with modified Michaelis-Menten kinetics is recommended.

Plant-Mediated Green Synthesis of Zinc Oxide Nanoparticles Using Peel Extract of Citrus reticulate for Boosting Seed Germination of Brassica nigra Seeds.

High demand of food for rapidly increasing population requires novel but ecofriendly fertilizers. Green reducing and capping agents are being explored to minimize production cost and toxicity of chemicals in synthesis of nanoparticles (NPs) which could be used to increase the production of crops and plants. In present research, Zinc Oxide Nanoparticles (ZnO NPs) are produced by employing an eco-friendly, simple and efficient green route using peel extract of Citrus reticulate. The optical properties of green synthesized ZnO NPs are explored by UV-Visible and Photoluminance spectroscopies where NPs presented 3.21 to 3.13 eV band gap. The morphology and purity of the ZnO NPs are analyzed by scanning electron microscopy (SEM), X-ray diffraction technique (XRD) and energy dispersive X-ray spectroscopy (EDX), respectively. The spherical like ZnO NPs having 23-90 nm size exhibited hexagonal structure with 8.89 to 8.62 nm crystallite size. Fourier transform infrared spectroscopy (FTIR) explores the existence of specific functional groups which are responsible for stabilization, capping and reduction during synthesis of nanoparticles. The green synthesized ZnO NPs are tested for seed germination of Brassica nigra (black mustard) seeds at standard temperature and pressure. The activity shows that germination percentage of the Brassica nigra seeds is enhanced 100% and seedling vigor index 16.45 after treatment with ZnO NPs and can be controlled by the concentration of NPs. Therefore, it can be expected that ZnO NPs can serve as the cost effective and ecofriendly nano-fertilizers in agriculture.

Prediction of soil seed bank of piedmont and alluvial environments of Dera Ghazi Khan, Punjab, Pakistan.

The current focus is on the overall pattern of seed storage present in the fragments of the soil of piedmont and alluvial landscapes of the environment. The present study predicted the seed banks of both soils of alluvial and piedmont zones in different ecological conditions and evaluate the potential of seeds in the restoration of both environments. The composition of the seed bank of soil is mainly affected by the alluvial environment and the structure of cleared area shows that more species of germinating annual grasses and growable seeds with the higher total number. Extant vegetation structures have an important role in the diversity of soil seed reservoirs, whose composition corresponded with the openness of the site. When in situ soil seed bank is recruited, it helps to restore only some components of the plant community in an alluvial environment. In our current research, it was confirmed that seed richness was higher in number at lower elevation (alluvial) than that at high elevation (piedmont). Seed richness showed a significant negative correlation with anions, cations, while significantly positive with altitude that suggests the richness pattern of the overall seed bank of the area is influenced by various environmental factors.

Polyphenol-Assisted Chemical Crosslinking: A New Strategy to Achieve Highly Crosslinked, Antioxidative, and Antibacterial Ultrahigh-Molecular-Weight Polyethylene for Total Joint Replacement.

Highly crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE) bearings are wear-resistant to reduce aseptic loosening but are susceptible to oxidize in vivo/in vitro, as reported in clinical studies. Despite widespread acceptance of antioxidants in preventing oxidation, the crosslinking efficiency of UHMWPE is severely impacted by antioxidants, the use of which was trapped in a trace amount. Herein, we proposed a new strategy of polyphenol-assisted chemical crosslinking to facilitate the formation of a crosslinking network in high-loaded tea polyphenol/UHMWPE blends. Epigallocatechin gallate (EGCG), a representative of tea polyphenol, was mixed with UHMWPE and peroxide. Multiple reactive phenolic hydroxyl groups of tea polyphenol coupled with the nearby free radicals to form extra crosslinking sites. The crosslinking efficiency was remarkably enhanced with increasing tea polyphenol content, even at a concentration of 8 wt %. Given by the hydrogen donation principle, the high-loaded tea polyphenol also enhanced the oxidation stability of the crosslinked UHMWPE. The antioxidative performance was preserved even after tea polyphenol elution. Moreover, superior antibacterial performance was achieved by the in situ tea polyphenol release from the interconnected pathways in the present design. The strategy of polyphenol-assisted chemical crosslinking is applicable for producing highly crosslinked, antioxidative, and antibacterial UHMWPE, which has promising prospects in clinical applications.

Synergy between vitamin E and D-sorbitol in enhancing oxidation stability of highly crosslinked ultrahigh molecular weight polyethylene.

Oxidative stability of radiation crosslinked ultrahigh molecular weight polyethylene (UHMWPE) artificial joints is significantly improved by vitamin E (VE), but there is a dilemma that VE hinders crosslinking and thus jeopardizes the wear of UHMWPE. In this effort, we proposed an efficient strategy to stabilize UHMWPE under limited antioxidant contents, where VE and D-sorbitol (DS) were used as the primary antioxidant and the secondary antioxidant respectively. For non-irradiated blends with fixed antioxidant contents, oxidative stability accessed by oxidation induction time (OIT) of VE/DS/UHMWPE blends was superior to that of VE/UHMWPE blends, while DS/UHMWPE blends showed no increase in OIT. The cooperation between DS and VE exhibited a synergistic effect on enhancing the oxidative stability of UHMWPE. Interestingly, the irradiated VE/DS/UHMWPE blends showed comparable OIT but a significantly higher crosslink density than the irradiated VE/UHMWPE blends. The crystallinity, melting point, and in vitro biocompatibility of the blends were not affected by VE and DS. The quantitative relationships of mechanical properties, oxidation stability, crystallinity and crosslink density were established to unveil the correlation of these key factors. The overall properties of VE/UHMWPE and VE/DS/UHMWPE blends were compared to elucidate the superiority of the antioxidant compounding strategy. These findings provide a paradigm to break the trade-off between oxidative stability, crosslink density and mechanical properties, which is constructive to develop UHMWPE bearings with upgraded performance for total joint replacements. STATEMENT OF SIGNIFICANCE: VE-stabilized UHMWPE is the most commonly used material in total joint replacements at present. However, oxidation and wear resistance of VE/UHMWPE implants cannot be unified since VE reduces the efficiency of radiation crosslinking. It limits the use of VE. Herein, we proposed a compounding stabilization by the synergy between VE and DS. The antioxidation capability of VE was revived by DS, thus enhancing the oxidation stability of unirradiated UHMWPE. The irradiated VE/DS/UHMWPE exhibited similar oxidation stability but higher crosslink density than irradiated VE/UHMWPE, which is beneficial to combat wear of UHMWPE and to inhibit the occurrence of osteolysis. This synergistic antioxidation strategy endows the UHMWPE joint material with good overall performance, which is of clinical significance.

Controlled bacteriostasis of tea polyphenol loaded ultrahigh molecular weight polyethylene with high crosslink density and oxidation resistance for total joint replacement.

To avoid catastrophic bacterial infection in prosthesis failure, ultrahigh molecular weight polyethylene (UHMWPE), a common bearing material of artificial joints, has been formulated with antibiotics to eliminate bacteria locally at the implant site. However, the pressing issues regarding cytotoxic effects and evolution of drug resistant bacteria necessitates the development of bio-friendly bacteriostat with long bacteriostatic efficacy. Herein, tea polyphenol extracted from nature source was introduced in UHMWPE as a biogenic antimicrobial. Controlled antimicrobial activity was achieved by chemical crosslinking to regulate the release of the tea polyphenol. In addition, the crosslinking efficiency of UHMWPE blends with high loaded tea polyphenol was significantly improved in comparison to radiation crosslinking. The immobilized tea polyphenols also enhanced the oxidation stability of the UHMWPE, which is essential to prolong the service life in vivo and the storage time in vitro. The blends presented good biocompatibility, despite cell repellent on the highly crosslinked surface. Chemically crosslinked tea polyphenol/UHMWPE exhibited feasible properties for total joint implants, which is promising for clinical application.

Gamma-ray shielding characteristics of flexible silicone tungsten composites.

Silicone being a hybrid elastomer is well known for its excellent thermal and mechanical properties, chemical resistance, compatibility with organic and inorganic fillers, nontoxicity, and flexibility. As the reported literature on silicone tungsten composite is rare, thus, a complete possible spectrum of silicone tungsten composites series with tungsten loading of 0-88.1 %wt has been fabricated by RTV method and studied as a flexible gamma shielding material. Flexible silicone/tungsten composite formulations containing different weight percentages of tungsten powder (0, 30.1, 47.8, 59.8, 68.1, and 88.1 wt %) were developed by the room-temperature vulcanization route. Two lead collimators with diameters of 0.6 cm were used to make a narrow beam geometry for gamma rays emitted from a137Cs (gamma-ray energy of 662 keV) point source. Uncollided flux was measured with a NaI(Tl) scintillation detector enclosed in lead shielding to reduce the background radiation level. The measured mass attenuation coefficient for our composites with 88.1 wt % tungsten was 0.1035 cm2/g, which is nearly 3.5% higher than that of commercially available silicone/tungsten composites named T-Flex (nearly 0.095 cm2/g) containing the same tungsten loading. Similarly, superior half value layers (HVL) of our composites with 88.1 % wt loading of tungsten i.e 1.01 cm versus 1.27 cm for the reported T-Flex counterpart with additional advantage of insitu fabrication on complex geometries. It was also found that the effectiveness of gamma-ray shielding increases with increase in density of the composites, which is due to the increase in the weight percent of tungsten powder. Our material will have applications as shielding material for both mobile and stationary radiation sources and it can also be used as fabrication material for gloves, safety shoes, coats, etc. to protect workers in a radiation environment.

The effect of Vitamin C on melanin pigmentation - A systematic review.

Vitamin C, also known as ascorbic acid, is used as a treatment modality in depigmentation of hyperpigmented spots on the skin and gingiva. This systematic review discusses the studies conducted to assess the effect of Vitamin C on melanin pigmentation. The primary objective was to evaluate the effect of Vitamin C on melanin pigmentation. The secondary objective was to analyze the effect of Vitamin C administration on melanin pigmentation. An electronic database search was conducted from the following databases: PubMed, EBSCOhost, ScienceOpen, EMBASE and Google Scholar. Randomized controlled trials, experimental studies, case-control studies and cohort studies published in peer-reviewed journals in English language were included. Case reports, case series, animal model studies, in vitro studies, studies where Vitamin C was used along with other agents and unpublished research were excluded. Out of 22,580 studies, only 7 studies satisfied the selection criteria. Data extraction sheet was prepared, and the studies were analyzed. Out of the 7 studies analyzed, 1 was a randomized controlled trial and 6 were experimental studies. Vitamin C has been used widely as a depigmenting agent in dermatology. However, there are limited studies conducted on the use of Vitamin C for gingival depigmentation.