PLGA‐based in situ‐forming system: degradation behavior in the presence of hydroxyapatite nanoparticles

The degradation behavior of poly(lactic‐co‐glycolic acid) (PLGA) is important for its application as a biomaterial. In this work, the influence of nano‐hydroxyapatite (nano‐HA) on the degradation behavior of PLGA matrix was studied. PLGA‐based in situ forming system containing nano‐HA was prepared using the immersion precipitation method and the polymer hydrolysis was investigated in a phosphate buffer (pH 7.4) at 37°C. The pH values in the testing medium were evaluated to quantify the degradation process. Gel permeation chromatography and scanning electron microscopy techniques were employed to monitor changing of the weight‐average molecular weight (M_W) and the body structures of PLGA matrices, respectively. To model the M_W changes, a first‐order degradation model was employed. The formed PLGA matrices had different porosities that effected water penetration into the matrices following the hydrolysis process. The obtained degradation rate constant using a mathematical model for PLGA matrices with different nano‐HA content was about from 2.5 to 4.5 times lower than neat PLGA matrix. POLYM. ENG. SCI., 59:1028–1035, 2019. © 2019 Society of Plastics Engineers     

Sunlight photodecolorization of a mixture of Methyl Orange and Bromocresol Green by CuS incorporated in a clinoptilolite zeolite as a heterogeneous catalyst

Photocatalytic activity of CuS incorporated into an Iranian clinoptilolite (CuS-Cp) was studied for decolorization of a mixture of Methyl Orange and Bromocresol Green under sunlight irradiation. All samples were characterized by XRD, FTIR, DRS and TG/DTG techniques. The effect of some key experimental parameters such as: amount of the catalyst (0.05–5 g L^?1), initial concentration of dyes (5–30 mg L^?1), solution pH (1–11) and also dosage of H₂O₂ and KBrO₃ was studied on the decolorization extent. The extent of decolorization was estimated from the residual concentration by spectrophotometrically and it was confirmed by the reduction of chemical oxygen demand (COD).     

Effects of Ramadan fasting on cardiovascular risk factors: a prospective observational study

ABSTRACT: BACKGROUND: Previous research has shown that Ramadan fasting has beneficial effects on cardiovascular risk factors, however there are controversies. In the present study, the effect of Ramadan fasting on cardiovascular risk factors has been investigated. METHOD: This is a prospective observational study that was carried out in a group of patients with at least one cardiovascular risk factor (including history of documented previous history of either coronary artery disease (CAD), metabolic syndrome or cerebro-vascular disease in past 10 y). Eighty two volunteers including 38 male and 44 female, aged 29--70 y, mean 54.0 [PLUS-MINUS SIGN] 10 y, with a previous history of either coronary artery disease, metabolic syndrome or cerebro-vascular disease were recruited. Subjects attended the metabolic unit after at least 10 h fasting, before and after Ramadan who were been fasting for at least 10 days. A fasting blood sample was obtained, blood pressure was measured and body mass index (BMI) was calculated. Lipids profile, fasting blood sugar (FBS) and insulin, homocysteine (hcy), high-sensitivity C-reactive protein (hs-CRP) and complete blood count (CBC) were analyzed on all blood samples. RESULTS: A significant improvement in 10 years coronary heart disease risk (based on Framingham risk score) was found (13.0 [PLUS-MINUS SIGN] 8 before Ramadan and 10.8 [PLUS-MINUS SIGN]7 after Ramadan, P <0.001, t test).There was a significant higher HDL-c, WBC, RBC and platelet count (PLT), and lower plasma cholesterol, triglycerides, LDL-c, VLDL-c, systolic blood pressure, body mass index and waist circumference after Ramadan (P <0.05, t test). The changes in FBS, insulin,Homeostasis Model Assessment Insulin Resistance (HOMA-IR), hcy, hs-CRP and diastolic blood pressure before and after Ramadan were not significant (P >0.05, t test). CONCLUSIONS: This study shows a significant improvement in 10 years coronary heart disease risk score and other cardiovascular risk factors such as lipids profile, systolic blood pressure, weight, BMI and waist circumference in subjects with a previous history of cardiovascular disease.     

Photothermal inactivation of methicillin‐resistant Staphylococcus aureus : anti‐biofilm mediated by a polypyrrole–carbon nanocomposite

Widespread resistance to antibiotics amongst pathogens has become a tremendous challenge of high morbidity and mortality rates which increases the needs to exploring novel methods of treatment. An efficient antimicrobial procedure to root out pathogenic bacteria is photothermal therapy. In this study, antimicrobial effects of a polypyrrole–carbon nanocomposite (PPy‐C) upon laser irradiation in order to destroy the pathogenic gram‐positive bacterium, methicillin‐resistant Staphylococcus aureus (MRSA) were assessed. The bacterial cells were incubated with 500, 750 and 1000 μg ml⁻¹ concentrations of PPy‐C and irradiated with an 808‐nm laser at a power density of 1.0 W cm⁻². To indicate the biocompatibility and toxic effect of the nanocomposite without and with laser irradiation, the authors counted the number of CFUs and compared it to an untreated sample. Antibacterial mechanisms of PPy‐C were assessed through temperature increment, reactive oxygen species production, and protein and DNA leakages. Photothermal heating assay showed that 26°C temperature increases in the presence of 1000 µg ml⁻¹ PPy‐C led to >98% killing of MRSA. Furthermore, 20 min radiation of near‐infrared light to PPy‐C in different concentrations indicated destruction and reduction in the MRSA biofilm formation. Therefore, PPy‐C was introduced as a photothermal absorber with a bactericidal effect in MRSA.Inspec keywords: laser applications in medicine, biomedical materials, DNA, nanofabrication, biochemistry, nanocomposites, microorganisms, nanomedicine, cellular biophysics, antibacterial activity, molecular biophysics, proteinsOther keywords: photothermal inactivation, staphylococcus aureus, anti‐biofilm, polypyrrole–carbon nanocomposite, widespread resistance, bacterial pathogens, high morbidity, mortality rates, efficient antimicrobial procedure, pathogenic bacteria, photothermal therapy, antimicrobial effects, PPy‐C, laser irradiation, pathogenic gram‐positive bacterium, bacterial cells, biocompatibility, toxic effect, reactive oxygen species production, photothermal heating assay, MRSA biofilm formation, photothermal absorber, bactericidal effect, methicillin‐resistance, temperature 26.0 degC, time 20.0 min     

A New Chemical Probe for Phosphatidylinositol Kinase Activity

Phosphatidylinositol kinases (PIKs) are key enzymatic regulators of membrane phospholipids and membrane environments that control many aspects of cellular function, from signal transduction to secretion, through the Golgi apparatus. Here, we have developed a photoreactive “clickable” probe, PIK‐BPyne, to report the activity of PIKs. We investigated the selectivity and efficiency of the probe to both inhibit and label PIKs, and we compared PIK‐BPyne to a wortmannin activity‐based probe also known to target PIKs. We found that PIK‐BPyne can act as an effective in situ activity‐based probe, and for the first time, report changes in PI4K‐IIIβ activity induced by the hepatitis C virus. These results establish the utility of PIK‐BPyne for activity‐based protein profiling studies of PIK function in native biological systems.     

Conductive heating and microwave hydrolysis under identical heating profiles for advanced anaerobic digestion of municipal sludge

Microwave (2.45 GHz, 1200 W) and conventional heating (custom pressure vessel) pretreatments were applied to dewatered municipal waste sludge (18% total solids) using identical heating profiles that span a wide range of temperatures (80–160 °C). Fourteen lab-scale semi-continuous digesters were set up to optimize the energy (methane) output and sludge retention time (SRT) requirements of untreated (control) and thermally pretreated anaerobic digesters operated under mesophilic and thermophilic temperatures. Both pretreatment methods indicated that in the pretreatment range of 80–160 °C, temperature was a statistically significant factor (p-value < 0.05) for increasing solubilization of chemical oxygen demand and biopolymers (proteins, sugars, humic acids) of the waste sludge. However, the type of pretreatment method, i.e. microwave versus conventional heating, had no statistically significant effect (p-value >0.05) on sludge solubilization. With the exception of the control digesters at a 5-d SRT, all control and pretreated digesters achieved steady state at all three SRTs, corresponding to volumetric organic loading rates of 1.74–6.96 g chemical oxygen demand/L/d. At an SRT of 5 d, both mesophilic and thermophilic controls stopped producing biogas after 20 d of operation with total volatile fatty acids concentrations exceeding 1818 mg/L at pH <5.64 for mesophilic and 2853 mg/L at pH <7.02 for thermophilic controls, while the pretreated digesters continued producing biogas. Furthermore, relative (to control) organic removal efficiencies dramatically increased as SRT was shortened from 20 to 10 and then 5 d, indicating that the control digesters were challenged as the organic loading rate was increased. Energy analysis showed that, at an elevated temperature of 160 °C, the amount of methane recovered was not enough to compensate for the energy input. Among the digesters with positive net energy productions, control and pretreated digesters at 80 °C were more favorable at an SRT of 10 d.     

New achievements in visco-elastoplastic constitutive model and temperature sensitivity of glasphalt

This paper focuses on the experimental investigation on temperature sensitivity and visco-elastoplastic behaviour of glasphalt. Classic Burgers creep model could only describe the viscoelastic behaviour of materials before the third creep-phase, so a viscoplastic string is added in series with classic Burgers model in order to predict the visco-elastoplastic behaviour of glasphalt. In this research, the effects of loading stress and temperature on creep behaviour of glasphalt under dynamic loading are investigated. In addition, some methods were used to solve model parameters and then predictions from proposed model were compared with experimental results. It was shown that creep testing curves coincided well with theoretic curves, validating that modified Burgers model can completely characterise creep behaviour of glasphalt. Besides, temperature sensitivity of glasphalt was evaluated by using indirect tensile stiffness modulus test, and stiffness modulus behaviour model of glasphalt was presented based on the experimental results and numerical analysis.     

Mn‐doped ZnS quantum dots‐chlorin e6 shows potential as a treatment for chondrosarcoma: an in vitro study

Chondrosarcoma is the second‐most malignant cancer of the bone and routine treatments such as chemotherapy and radiotherapy have not responded to the treatment of this cancer. Due to the resistance of chondrosarcoma to radiotherapy, the combination of therapeutic methods has been considered in recent years. In this study, a novel combination approach is used that allows photodynamic therapy to be activated by X‐rays. The synthesis of Mn‐doped zinc sulphide (ZnS) quantum dots was carried out and chlorin e6 photosensitiser attached by covalent and non‐covalent methods and their application as an intracellular light source for photodynamic activation was investigated. The toxicity of each nanoparticles was evaluated on chondrosarcoma cancer cells (SW1353) before and after radiation. Also, the effect nanoparticle‐photosensitiser conjugated type was investigated in the therapeutic efficacy. The characterisation test (SEM, TEM, EDS, TGA, XRD and ICP analyses) was shown successful synthesis of Mn‐doped ZnS quantum dots. Chondrosarcoma cancer cell viability was significantly reduced when cells were treated with MPA‐capped Mn‐doped ZnS quantum dots‐chlorin e6 with spermine linker and with covalent attachment (P  ≤ 0.001). These results indicate that X‐ray can activate the quantum dot complexes for cancer treatment, which can be a novel method for treatment of chondrosarcoma.Inspec keywords: semiconductor quantum dots, X‐ray diffraction, transmission electron microscopy, cadmium compounds, cellular biophysics, drugs, manganese, biomedical materials, cancer, quantum dots, nanofabrication, ultraviolet spectra, zinc compounds, fluorescence, scanning electron microscopy, nanoparticles, nanomedicine, bone, photochemistry, photodynamic therapy, tumours, II‐VI semiconductors, laser applications in medicineOther keywords: noncovalent methods, photodynamic activation, chondrosarcoma cancer cells, chondrosarcoma cancer cell viability, quantum dot complexes, cancer treatment, malignant cancer, routine treatments, radiotherapy, therapeutic methods, Mn‐doped zinc sulphide quantum dots, in vitro study, MPA‐capped Mn‐doped ZnS quantum dots‐chlorin e6, nanoparticle‐photosensitiser conjugated type, ZnS, Mn, ZnS:Mn     

High‐responsivity AlGaN–GaN multi‐quantum well UV photodetector

In this paper, we propose a set of AlGaN–GaN multi‐quantum well (MQW) photodetectors based on p‐i‐n heterostructures with 14 AlGaN–GaN MQW structures in i‐region, where GaN quantum well has 6 nm thickness and Al_xGa_1−xN barrier thickness is 3 nm. In this structure, the peak responsivity of 0.19 A/W at 246 nm is reported. In addition, we investigate effects of various parameters on responsivity, and we show that responsivity of MQW‐based photodetectors strongly depends on proper device design, that is, number of quantum wells, well thickness, barrier thickness, and mole fraction. We also show that increasing number of quantum wells, thickness of wells, and mole fraction as well as decreasing thickness of barriers, increase the responsivity. Using obtained results, we proposed optimal structure. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of various post materials and resin luting cements on microleakage in endodontically treated root canals

The effect of various post materials luted with different resin luting cements on microleakage in root canals was studied in the present study. Sixty carious and crack-free premolars were prepared using a step-back technique and obturated with gutta-percha. The roots were randomly divided into six groups (n = 10). Two different post types, glass fiber reinforced posts and zirconium posts (ZP), were cemented three different resin adhesive cements (Panavia F 2.0, Smartcem 2, and Variolink II) in the root canals. All specimens were thermal cycled and stored in the methylene blue solution for one week. The roots were sectioned horizontally into three sections: apical, middle, and coronal. The occlusal direction of each section was digitally photographed under a stereomicroscope. Dye penetration area was calculated as the methylene blue-infiltrated surface divided by total dentin area. After the two-way Anova test results, Tukey HSD and Bonferroni tests were used for multiple comparisons. According to the test results, ZP luted with Panavia F showed the best microleakage results and glass fiber posts luted with smartcem 2 showed the most unsuccessful microleakage results (p = 0.146).