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Fabrication of precipitated calcium carbonate (PCC) based superhydrophobic gloves from Sri Lankan dolomite
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Dilhani, K.G.S.S.; Karunaratne, D.G.G.P.; Manipura, A.
Manufacturing bioinspired superhydrophobic covering on natural rubber gloves surface from Sri Lankan dolomite as a value-added process to local dolomite. In this study, we introduce a simple and effective method to synthesize superhydrophobic coating on glove surfaces using superhydrophobic precipitated calcium carbonate nanoparticles (nPCC) using dolomite as the raw material. Sodium stearates were used as a binder, while fatty acid was used to improve the superhydrophobicity. nPCC suspension was made with ethyl acetate, and it was applied on the glove surfaces via spray coating and dip coating methods. The products were subjected to scanning electron microscopy (SEM) to identify the morphology of nPCC and coating. SEM images confirm the presence of nano coating on PCC (1-100 nm) and on the glove surface (200 nm). Fourier Transform Infrared Spectroscopy (FTIR) was used to identify functional groups on surface coating, which confirmed the presence of stearates, ethyl acetate and fatty acid on the glove surfaces, while water contact angles were measured using a drop shape analyzer. In spray coating methods, obtained contact angles on glove surfaces were 142° for stearic modified and 144.5 ° for stearic\fatty acid- modified coating. It was 154.7° for dip coating methods. According to the results, stearates and fatty acids improve superhydrophobicity, while ethyl acetate gives a uniform nanoparticle suspension. Among the coating methods compared, spray coating gave a uniform coating on the glove surface.
9.4% Efficiency of a quasi-solid-state dye-sensitized solar cell under low light irradiance
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Gunathilake, S.M.S.; Bandara, T.M.W.J.; Pemasiri, B.M.K.
To convert highly abundant solar energy to electricity, low-cost dye-sensitized solar cells (DSCs) have attracted researchers' attention. Solar cells do not receive constant irradiance throughout the day when used in real outdoor applications. The efficiency of Si solar cells decreases with decreasing irradiance. However, very few studies have focused on studying the performance of DSCs as a function of light intensity. The present research is focused on improving gel polymer electrolyte-based DSCs and studying their performances under variable irradiance. The cells were fabricated with photoelectrodes having six spin- coated TiO2 layers photo-sensitized by N719 dye. The counter electrode was a piece of Pt-coated glass, and the gel polymer electrolyte contained binary salts tetrahexylammonium iodide and lithium iodide. Performance enhancers, 4-tert-butyl pyridine and 1-methyl-3-propylimidazolium iodide, were added to maximize the efficiency of the cell. In addition, the cell's performance was enhanced by the infusion of graphene into the fourth layer. The fabricated DSC was irradiated using Peccell PEC-LO1 solar simulator, and the irradiation level varied from 1,000 W m⁻² to 67 W m⁻², changing the distance from the solar simulator to the cell. To the best of our knowledge, this is the first study of the light intensity dependence of efficiency in graphene-incorporated DSCs. The fabricated quasi-solid-state DSC performed at an overall maximum efficiency of 6.8%, an open-circuit voltage of 770 mA, a short circuit current density of 13.4 mA cm⁻² , and a 66.3% fill factor under 1,000 W m⁻² irradiation. The efficiency and fill factor of the DSC increased gradually with the decreasing solar irradiance. The DSC achieved maximum efficiency and fill factor of 9.4 and 83.3%, respectively, at 67 W m⁻² of input solar irradiance. The present study concludes that the efficiency and fill factor of graphene-added DSC increase with the decrease of solar irradiance. Lower efficiencies at higher irradiance relate to the transport limitation of the redox mediator in such cells.
NMDA and trpv1 receptors: potential therapeutic targets of paspanguwa herbal formula
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Gunaratne, J.C.; Uduwela, D.R.; Ranatunga, R.J.K.U.
Despite the broad use of cough (antitussive and expectorant) medicine, there is little evidence for its clinical use. Dextromethorphan is a widely used antitussive that is considered effective by the U.S. Food and Drug Administration. N-methyl D-aspartate (NMDA) receptors are the therapeutic target of dextromethorphan. The transient receptor potential vanilloid 1 (TRPV1) receptor stimulates the cough reflex and has recently been identified as a potential drug target for treating cough. We hypothesize that the mechanism of the anti- cough effects of paspanguwa, an ayurvedic herbal drink, is due to inhibiting NMDA and TRPV1 receptors.This study aimed to identify natural products in the formula that bind favourably to the active sites of the receptors. Twenty-three natural products from paspanguwa were examined. The cryo-EM structures of NMDA receptor (PDB 7eu7) and TRPV1 receptor (PDB 3J5P) were used as receptor coordinates. AutoDock Vina was used for molecular docking at four active sites: glycine-binding site, glutamate- binding site and the ion-channel of NMDA, and the active site of TRPV1 receptor. Diosgenin, solasodine and tomatidenol showed the highest binding affinity to both the glutamate-binding site and glycine-binding site; the affinity well above that of references indicates the possibility of these natural products acting as NMDA antagonists and non-competitive antagonists. Diosgenin, tomatidenol, and oleanolic acid showed the highest affinity to the NMDA channel; an affinity higher than that of references indicates the ability to act as better channel blockers. At the active site of TRPV1, solasodine, diosgenin, and tomatidenol showed binding affinity on par with the references, indicating that they might act as TRPV1 antagonists. Findings from the study show that natural products from paspanguwa bind to active sites of NMDA and TRPV1 receptors. The reported anti-cough properties of the formula may, at least in part, be due to inhibiting NMDA and TRPV1 receptors.
Commiphora wightii gum extract mediated synthesis of silver nanoparticles and their bactericidal efficacy
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Wickramarathne, C.; Rajapakse, S.; Seneviratne, V.N.
Nanobiotechnology is an important division in nanotechnology that involves various biological entities for nano-synthesis. Silver nanoparticles (AgNPs) received tremendous attention owing to their versatile and promising properties and their wide range of applications. Moreover, nano-synthesis using plants is a promising approach among other biological sources because of the presence of the high amount of phytochemicals and the feasible procedures required in nano-synthesis. However, AgNP synthesis by incorporating Commiphora wightii (guggul) plant gum is not attempted previously. C. wightii, belonging to the family Burseraceae, is used in ayurvedic medicine due to its anticancer, antimicrobial and anti- inflammatory properties. The objective of this study was to green synthesize AgNPs using the gummy extract of C. wightii in a feasible, cost-effective and environmentally-friendly manner and evaluate their bactericidal efficacy. AgNPs were fabricated by the addition of C. wightii extract to AgNO3 while stirring and heating. Bactericidal efficacy was determined against Escherichia coli and Staphylococcus aureus using the standard Kirby-Bauer Disk diffusion method. A rapid colour transformation was observed from light brown to deep brown indicating AgNP formation, and it was confirmed by a characteristic band at 427 nm. X-Ray Diffraction patterns revealed the crystalline nature and the Face Centred Cubic structure of AgNPs. Moreover, Transmission Electron Microscopic analysis highlighted well-dispersed spherical AgNPs around 5-20 nm. Fourier Transform Infra-Red spectra revealed the presence and involvement of functional groups of steroids, flavonoids, terpenoids, carbohydrates etc. C. wightii gummy extract alone and AgNPs synthesized using gummy extract showed antibacterial potential against both E. coli and S. aureus. The diameters of zones of inhibition were 12.56±0.35 nm and 10.27±0.25 nm for E. coli and S. aureus, respectively. Therefore, this method was an effective, single-step green synthetic approach for the synthesis of stabilized AgNPs and bactericidal efficacy for both bacterial gram classes proposes their applicability in biomedical utilities. Moreover, further modifications of this green procedure must be carried out before any industrial-scale production and applications.
Milk protein composition in different lactation stages of dairy cattle grazing on saltmarsh pastures in Mannar, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Kumari, G.M.M.; Navaratne, A.N.; Ranawana, K.B
Cow milk is a nutrient-rich dairy product which has high demand worldwide. Improving local dairy production is essential to overcome malnutrition in the Sri Lankan population hit by the current food crisis. Cow milk is a vital source of high-quality proteins consisting of all nine essential amino acids required for humans. Considering the solubility factor, milk proteins belong to two main fractions that are casein (approximately 80% of total protein content) and whey protein (about 20% of total protein content). The composition of raw cow milk depends upon the stage of lactation, the feeding source, the cow's health and genetic factors. The study aimed to investigate the differences in total milk protein composition of cow milk within the lactation curve of cattle grazing on two types of pastures in Sri Lanka. The samples were collected during early, mid and late lactation stages from two cattle groups grazing on saltmarsh pastures in Mannar and dry pastures in Medawachchiya. The milk samples were tested for total protein composition (%w/w) by the ultrasonic Lactoscan MCC milk analyzer. Considering the results, the total milk protein composition of saltmarsh pasture feeding cattle was significantly higher (p<0.05) during the mid (3.48%) and late (3.54%) lactation stages than the dry pasture-feeding cattle. During the early lactation stage, the mean total protein composition (n=30, 3.38 %) of saltmarsh pasture feeding cattle was high compared to the mean total protein composition (n=25, 3.28%) of dry pasture feeding cattle, though statistically not significant (p>0.05). Since the milk protein yield is relatively proportional to the energy content of the diet in dairy cattle, this indicates that the saltmarsh pasture-based diet gives high energy to cattle. This study concludes that the protein composition of raw cow milk depends on the feeding pasture and the stage of the lactation period of dairy cattle.