The effects of gold nanoparticles size and concentration on viscosity, flow activation energy, dielectric and optical properties

This study was carried out to investigate viscosity in relation with the temperature, flow activation energy and dielectric properties for 10, 20 and 50 nm gold nanoparticles size (GNPs) in addition to absorption and fluorescence spectra at different concentrations (0.2 × 10-3 to 1 × 10-2%) in an attempt to cover and understand the toxicity and potential role of their therapeutic and diagnostic use in medical applications. 10, 20 and 50 nm GNPs dissolved in aqueous solution were purchased (Product MKN-Au, Canada) and used in this study. Mechanical parameters were measured using Brookfield LVDV-III Programmable rheometer with temperature bath controlled by a computer. 0.5 ml of each GNP size in aqueous solution was poured in the sample chamber of the rheometer. The spindle was immersed and rotated in these gold nanofluids in the speed range from 50 to 250 rpm in steps of 20 min. Viscosity of GNPs was measured at temperature of 37°C and at a gradually increase of temperature to 42ºC. UV–Visible characterization of GNPs at different concentrations from 0.2 × 10-3 to 1 × 10-2 % was performed using UV-1601 PC, UV-Visible spectrophotometer. The absorbance measurements were made over the wavelength range of 250 to 700 nm using 1 cm path length quartz cuvettes. Fluorescence characterization of GNPs was performed over the wavelength range of 250 to 700 nm using FluoroMax-2 JOBIAN YVON-SPEX. The measured viscosities for all GNP sizes decreased with increasing the temperatures from 37 to 42°C. The GNPs with larger size (50 nm) exhibited higher viscosity values compared with 10 and 20 nm GNPs. The flow activation energies (kJ/mol) for 10, 20 and 50 nm GNPs were 332.55, 415.4 and 182.2 kJ/mol, respectively. The optical properties such as absorption maxima and the absorption intensity are particle size-dependent. The fluorescence emission band for GNPs with an excitation wavelength of 308 nm and photoluminescence (PL) band centre appeared at 408 nm. With the increase of GNPs concentration at a fixed GNP size of 20 nm, the intensity of emission band positioned increased, and the trend was consistent with the changes of the corresponding surface plasmon resonance (SPR) of GNPs. The presented dielectric data indicates that GNPs have strong dielectric dispersion corresponding to the alpha relaxation region in the frequency range of 20 Hz to 100 kHz which was identified as anomalous frequency dispersion. At a constant GNP size, the absorbance was found to be proportional to the concentration of gold. This is due to the increase in the number of GNPs as well as the increase in the SPR of GNPs. An intense absorption peak was observed at wavelength of 517 nm which is generally attributed to the surface plasmon excitation of the small spherical GNPs. The incident light at 308 nm will lead to excitation of the surface plasmon coherent electronic motion as well as the d electrons. This study suggests that the relaxation of these electronic motions followed by the recombination of the sp electrons with holes in the d band leads to the fluorescence emission. These results indicate that the intensity of fluorescence emission band of GNPs was dependent on the concentration of GNPs. A rapid decrease in the dielectric constant may be attributed to the tendency of dipoles in GNPs to orient themselves in the direction of the applied field in the low-frequency range. However, in the high-frequency range, the dipoles will hardly be able to orient themselves in the direction of the applied field and hence the value of the dielectric constant is nearly constant.Key words: Gold nanoparticles, viscosity, size, temperature, dielectric, absorption, fluorescence

Veterinary students’ perceptions of their learning environment as measured by the Dundee Ready Education Environment Measure

BACKGROUND: The Dundee Ready Education Environment Measure (DREEM) has been widely used to evaluate the learning environment within health sciences education, however, this tool has not been applied in veterinary medical education. The aim of this study was to evaluate the reliability and validity of the DREEM tool in a veterinary medical program and to determine veterinary students’ perceptions of their learning environment. METHODS: The DREEM is a survey tool which quantitatively measures students’ perceptions of their learning environment. The survey consists of 50 items, each scored 0–4 on a Likert Scale. The 50 items are subsequently analysed within five subscales related to students’ perceptions of learning, faculty (teachers), academic atmosphere, and self-perceptions (academic and social). An overall score is obtained by summing the mean score for each subscale, with an overall possible score of 200. All students in the program were asked to complete the DREEM. Means and standard deviations were calculated for the 50 items, the five subscale scores and the overall score. Cronbach’s alpha was determined for the five subscales and overall score to evaluate reliability. Confirmatory factor analysis was used to evaluate construct validity. RESULTS: 224 responses (53%) were received. The Cronbach’s alpha for the overall score was 0.93 and for the five subscales were; perceptions of learning 0.85, perceptions of faculty 0.79, perceptions of atmosphere 0.81, academic self-perceptions 0.68, and social self-perceptions 0.72. Construct validity was determined to be acceptable (p < 0.001) and all items contributed to the overall validity of the DREEM. The overall DREEM score was 128.9/200, which is a positive result based on the developers’ descriptors and comparable to other health science education programs. Four individual items of concern were identified by students. CONCLUSIONS: In this setting the DREEM was a reliable and valid tool to measure veterinary students’ perceptions of their learning environment. The four items identified as concerning originated from four of the five subscales, but all related to workload. Negative perceptions regarding workload is a common concern of students in health education programs. If not addressed, this perception may have an unfavourable impact on veterinary students’ learning environment

Twelve-month observational study of children with cancer in 41 countries during the COVID-19 pandemic

Introduction Childhood cancer is a leading cause of death. It is unclear whether the COVID-19 pandemic has impacted childhood cancer mortality. In this study, we aimed to establish all-cause mortality rates for childhood cancers during the COVID-19 pandemic and determine the factors associated with mortality. Methods Prospective cohort study in 109 institutions in 41 countries. Inclusion criteria: children &lt;18 years who were newly diagnosed with or undergoing active treatment for acute lymphoblastic leukaemia, non-Hodgkin's lymphoma, Hodgkin lymphoma, retinoblastoma, Wilms tumour, glioma, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma, medulloblastoma and neuroblastoma. Of 2327 cases, 2118 patients were included in the study. The primary outcome measure was all-cause mortality at 30 days, 90 days and 12 months. Results All-cause mortality was 3.4% (n=71/2084) at 30-day follow-up, 5.7% (n=113/1969) at 90-day follow-up and 13.0% (n=206/1581) at 12-month follow-up. The median time from diagnosis to multidisciplinary team (MDT) plan was longest in low-income countries (7 days, IQR 3-11). Multivariable analysis revealed several factors associated with 12-month mortality, including low-income (OR 6.99 (95% CI 2.49 to 19.68); p&lt;0.001), lower middle income (OR 3.32 (95% CI 1.96 to 5.61); p&lt;0.001) and upper middle income (OR 3.49 (95% CI 2.02 to 6.03); p&lt;0.001) country status and chemotherapy (OR 0.55 (95% CI 0.36 to 0.86); p=0.008) and immunotherapy (OR 0.27 (95% CI 0.08 to 0.91); p=0.035) within 30 days from MDT plan. Multivariable analysis revealed laboratory-confirmed SARS-CoV-2 infection (OR 5.33 (95% CI 1.19 to 23.84); p=0.029) was associated with 30-day mortality. Conclusions Children with cancer are more likely to die within 30 days if infected with SARS-CoV-2. However, timely treatment reduced odds of death. This report provides crucial information to balance the benefits of providing anticancer therapy against the risks of SARS-CoV-2 infection in children with cancer

Hepatitis E virus infection in patients with acute non-A, non-B, non-C hepatitis in Central Brazil

Hepatitis E virus (HEV) infection has a worldwide distribution and represents an important cause of acute hepatitis. This study aims to investigate the occurrence of HEV infection and factors associated with this infection in patients with acute non-A, non-B, non-C hepatitis in Central Brazil. From April 2012 to October 2014, a cross-sectional study was conducted among 379 patients with acute non-A, non-B, non-C hepatitis in the City of Goiania, Central Brazil. Serum samples of all patients were tested for serological markers of HEV infection (anti-HEV IgM and IgG) by ELISA. Positive samples were confirmed using immunoblot test. Anti-HEV IgM and IgG positive samples were tested for HEV RNA. Of the 379 serum samples, one (0.3%) and 20 (5.3%) were positive for anti-HEV IgM and IgG, respectively. HEV RNA was not found in any sample positive for IgM and/or IgG anti-HEV. After multivariate analysis, low education level was independently associated with HEV seropositivity (p = 0.005), as well as living in rural area, with a borderline p-value (p = 0.056). In conclusion, HEV may be responsible for sporadic self-limited cases of acute hepatitis in Central Brazil

Effects of quercetin and arginine on the nephrotoxicity and lipid peroxidation induced by gold nanoparticles in vivo

Mohamed Anwar K Abdelhalim, Huda AY Qaid, Yanallah Al-Mohy, Mohammed Suliman Al-Ayed Department of Physics and Astronomy, College of Science, King&nbsp;Saud University, Riyadh, Saudi Arabia Introduction: This study aimed to evaluate the nephrotoxicity caused by gold nanoparticles (GNPs) and investigate the potential roles of quercetin (Qur) and arginine (Arg) in mitigating the inflammatory kidney damage and dysfunction and inhibiting the toxicity induced by GNPs in rats.Methods: Kidney function was assessed using various serum biomarkers, including blood urea nitrogen (BUN), uric acid (URIC), and creatinine (CR), while toxicity was evaluated by measuring the biomarkers glutathione (GSH) and malondialdehyde (MDA) in kidney tissues. Results: Administration of GNPs to the rats severely affected the serum kidney biomarkers, as confirmed by the notable increases in BUN, URIC, and CR. Substantial changes in the levels of the biomarkers MDA and GSH in the kidney tissues were also observed, with a reduced level of GSH and elevated MDA activity. The administration of Qur or Arg exerted a protective effect against GNP-induced inflammatory kidney damage and toxicity, but with different responses according to their evaluated normalized values.Conclusion: This study demonstrates the beneficial effects of supplementation with Qur or Arg during the treatment with GNPs, potentially providing a powerful tool for cancer therapy. Keywords: gold nanoparticles, nephrotoxicity, lipid peroxidation, inflammatory damage, natural antioxidant

Effect of melanin on gold nanoparticle-induced hepatotoxicity and lipid peroxidation in rats

Mohamed Anwar K Abdelhalim,1 Sherif A Abdelmottaleb Moussa,2,3 Huda AY Qaid,1 Mohammed Suliman Al-Ayed1 1Department of Physics and Astronomy, College of Science, King Saud University, Riyadh, Saudi Arabia; 2Committee of Radiation and Environmental Pollution Protection (CREPP), Department of Physics, College of Science, Al-Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh, Saudi Arabia; 3Biophysics Group, Biochemistry Department, Genetic Engineering and Biotechnology Division, National Research Center, Giza, Egypt Introduction: Melanin pigments are produced by melanocytes and are believed to act as antioxidants based on the belief that melanin can suppress electronically stirred states and scavenge the free radicals. Materials and methods: The study was aimed to verify and prove the toxicity induced by administration of gold nanoparticles (GNPs) and to characterize the role of melanin as an antioxidant against inflammatory liver damage, oxidative stress, and lipid peroxidation induced intraperitoneally by GNPs in vivo. Results: The findings from this study confirmed that administration of GNPs intraperitoneally caused liver damage in addition to producing oxidative stress and fatty acid peroxidation. The treatment of rats with melanin along with GNPs induced dramatic changes in all the measured biochemical parameters. Our data demonstrated that melanin completely inhibited inflammatory liver damage, oxidative stress, and lipid peroxidation, which was confirmed by the histological investigation of different liver sections stained by H&amp;E. Conclusion: These results suggest the beneficial use of melanin together with GNPs for alleviating its toxicity. Other studies should be implemented taking into consideration the role of melanin in comparison with other natural antioxidants. Keywords: liver, gold nanoparticles, hepatotoxicity, oxidative stress, lipid peroxidation, histological investigatio

Potential effects of different natural antioxidants on inflammatory damage and oxidative-mediated hepatotoxicity induced by gold nanoparticles

Mohamed Anwar K Abdelhalim,1 Sherif A Abdelmottaleb Moussa,2,3 Huda AY Qaid,1 Mohammed Suliman Al-Ayed1 1Department of Physics and Astronomy, College of Science, King Saud University, Riyadh, Saudi Arabia; 2Committee of Radiation and Environmental Pollution Protection, Department of Physics, College of Science, Al-Imam Mohammad Ibn Saud Islamic University, Riyadh, Saudi Arabia; 3Biophysics Group, Biochemistry Department, Genetic Engineering and Biotechnology Division, National Research Centre, Giza, Egypt Objective: The objective of this study was to verify and confirm the oxidative-mediated hepatotoxicity, inflammatory liver damage, and oxidative stress induced by intraperitoneal administration of gold nanoparticles (GNPs) in vivo; characterize the effect of different natural antioxidants on these hazardous changes; and finally choose the most powerful antioxidant among these different natural antioxidants.Methods: Ten-nanometer GNPs were dissolved in aqueous solution of 0.01% concentration. A dose of 50&nbsp;&micro;L of 10&nbsp;nm GNPs was administered intraperitoneally for 7&nbsp;days to the rats, whereas the antioxidants were orally administered for the same time period. The antioxidants used in the study were vitamin E (Vit E), &alpha;-lipoic acid (ALA), quercetin (Qur), arginine (Arg), and melanin. Forty Wistar-Kyoto male rats were used. Rats were arbitrarily divided into seven groups after acclimatization for 1&nbsp;week. For serum separation, blood samples were obtained from each animal. Serum liver function markers and tissue oxidative stress and lipid proxidation biomarkers were assessed.Results: The increase in the levels of gamma-glutamyl transferase, alkaline phosphatase, total protein, alanine aminotransferase, and total bilirubin in the serum of rats and the increase of malondialdehyde in the hepatic tissue and decrease in reduced glutathione when compared with the control in this study confirmed the ability of GNPs to cause hazardous effects.Conclusion: Treatment of rats with Vit E, ALA, Qur, Arg, and melanin along with GNPs significantly inhibited the inflammatory liver damage, lipid peroxidation, and the oxidative stress induced by GNPs in vivo, but with different responses due to their evaluated normalization values, and it has been confirmed that melanin is the most powerful antioxidant among these different natural antioxidants, ie, it has the most effective potential role against the hepatic inflammatory damage, oxidative stress, and lipid peroxidation. Keywords: antioxidants, oxidative stress, gold nanoparticles, hepatotoxicity, vitamin E, &alpha;-lipoic acid, quercetin, arginine, melanin, rat