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Chemically bound Silver nanoparticles on cotton textiles exhibiting efficient inhibition of escherichia coli and staphylococcus aureus
(University of Peradeniya, 2011-11-24) Bandara, I .M. C. C. D.; Rajapakse, R. M. G.; Rajapakse, S.
This study describes a convenient method for production of highly durable antimicrobial textile against laundering. The method involves layer-by-Iayer electrostatic self-assembly process. Here, natural cellulose substrate was modified with chloroacetic acid in the presence of sodium hydroxide, followed by drying and curing. Then it was immersed in silver nitrate solution for reducing the electrostatically attached silver ions into nanosized silver coatings on textile using sodium citrate as the reducing agent. Average particle size obtained was approximately 16.54 nm. The modified textile was tested for Gram positive Staphylococcus aureus and Gram negative Escherichia coli and showed antimicrobial activity even after 30 washing cycles. Antimicrobial activities were tested for the silver nanoparticles chemically bound on textile subjected to 5, 10, 15, 20, 30 washing cycles and found that a constant inhibition zone of 2 mm was obtained in each case. Control experiments done with silver nanoparticles physically entrapped in cotton showed progressive decrease in the inhibition zone due to excessive washing cycles.
Comparative pharmacognostic studies on Cyperus rotundus Linn. and Kyllinga monocephaia Rottb. (Cyperaceae)
(University of Peradeniya, 2011-11-24) Sudusinghe, S. P.; Marasinghe, P.; Damunupola, J. W.
Cyperusrotundus Linn., a perennial grass like herb of Cyperaceae family which is widely used in Ayurvedic medicine, cosmetics and new drug formulations in allopathic medicine, is officially known as "Mustha" in the Ayurvedic Pharmacopeia. Locally, the plant is known as "Kalanduru". Kyllingamonocephala Rottb of the same family has similar characteristics to C. rotundus Linn. and the latter is adulterated by K. monocephala Rottb. In addition, K. monocephala appears under the official Ayurvedic name of C. rotundus: in' many documents and web sites which triggered the question of its usage as a substitute since it might be affecting the quality of the final product. Rhizomes of both plants are the parts used as medicine, and have similar appearances when presented as a crude drug and are hard to differentiate. This research was designed to compare the two plants using pharmacognostic methods employed to analyse plants or plant related substances. The methods comprised macroscopic, microscopic and chemical analyses. Fresh plants of C. rotundus and K. monocephala were collected from Seeduwa, Anuradhapura, Nawinna and market samples of crude drug were collected from Seeduwa, Peradeniya, Nawinna and Anuradhapura. Identification of the two plants was performed at the National Herbarium, Royal Botanical Gardens, Peradeniya. Comparative studies of the two plants were perfomed macroscopically and microscopically, by comparison of plant morphological structures such as rhizomes, stems, leaves and inflorescences. For microscopic analyses, slides were prepared from fresh rhizomes of both plants and also from the market samples of the crude drug. The thickness of the exodermis, endoderm is and parenchyma were measured using Image J 1.43U software. Iodine, Safranin and Sudan III tests were carried out to identify ergastic cell contents in rhizomes of both plants. Ten replicates (each containing three measurements) from each location were used for all the measurements mentioned above. Upon completion of the comparative study and statistical analyses it was evident that these two plants could be easily distinguished mainly from their inflorescences and from the width of the leaves which is larger in C. rotundus. However; most of the other morphological structures were similar. From microscopical studies, it was apparent that rhizomes of the two plants and their contents were very similar except the thickness of exodermis, parenchyma and endoderm is, which were greater in C. rotundus. In conclusion, more advanced procedures such as chemical assay tests, ash value tests, quantification analysis of ergastic cell contents should be employed to compare the crude drug as well as the fresh rhizome of these two plants to evaluate the substitution of K. monocephala over C.rotundus in Ayurvedic medicine, cosmetics and drug formulations.
Comparison of antioxidant potential of Sri Lankan and Indian pomegranate (Punica granatum L.) Cultivars
(University of Peradeniya, 2011-11-24) Bopitiya, D,; Jayasooriya , J. A. P.L. P.; Madhujith, T.
Antioxidants, especially polyphenols, help to protect the body against oxidative stress by neutralising free radicals, reactive oxygen species (ROS) and reactive nitrogen species (RNS). The present study was carried out to determine the total phenolic content and antioxidant potential of extracts obtained from. the aril of Sri Lankan pomegranate (Punica granatum L) varieties (Nayana, Daya, Nimali) and an Indian variety. Well-ripened pomegranate fruits were obtained in August 2010 from the Regional Research Station, Department of Agriculture, Mankandura. Pomegranate juice was extracted by pressing the arils manually and filtering through Whatman No. 1 filter papers to remove particulate matter. The clear liquid devoid of particulate matter was used for analysis. Total Phenolic Content (TPC) was determined using Folin Ciocalteu colorimetric method and expressed as milligram of Gallic acid equivalents (GAE) per gram extract. Antioxidant potential of the fruit extracts was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH). Total Antioxidant Capacity (TAC) was determined using 2,2'-azinobis 3-ethylbenzothiazoline-6 sulphonic acid (ABTS) radical. DPPH radical scavenging capacity was expressed as IC value while TAC was expressed as percentage inhibition after lapse of 1 min. of the reaction. TPC of pomegranate varieties tested ranged from 0.015 to 0.164 mg GAE/g of extract. Daya variety possessed the highest TPC followed by Nayana, Nimali, and the Indian variety. The IC value of pomegranate extracts tested ranged from 0.182 mg/ml to 0.446 mg/ml with Nayana variety showing the highest antioxidant activity followed by the Indian variety, Nimali and Daya. Total Antioxidant Capacity (TAC) of pomegranate varieties tested varied from 72.73 - 93.1 % with the highest being observed in Nayana variety. The TAC of varieties Nayana, Nimali, Indian, Daya were 93.1%, 91.2%, 89.7% and 72.73%, respectively, at the 0.1g/ml concentration. Despite the moderate TPC, Nayana variety showed the highest antioxidant activity as measured by DPPH' scavenging activity (IC value 0.182 mg/ml) and the highest TAC (93.1% inhibition). On the other hand, Daya variety showed a relatively less antioxidant activity though it contained high level of TPC. The TPC and antioxidant activity as measured by TAC and IC value were not well correlated (R2 = 0.545 and 0.465, respectively). The poor correlation may be attributable to differential behaviour of phenolic constituents. Fruits with IC value of less than 1 mg/ ml are categorised as extremely high antioxidant potential fruits. Based on TAC and DPPH radical scavenging activity, pomegranate varieties tested can be categorised as fruits with high antioxidant potential.
Clinical and laboratory features of spotted fever rickettsioses in patients presented to teaching hospital, Peradeniya
(University of Peradeniya, 2011-11-24) Weerakoon, K. G. A. D.; Rajapakse, R. P. V. J.; Adikari, S. B.; Medagedara, S. C.; Nanayakkara, D. M.; Ranasingha, S.; Kularatne, S. A. M.
Spotted fever group rickettsioses (SFG) are predominantly seen in the central hills of Sri Lanka. Unfortunately, routine laboratory diagnostic facilities are not available in the hospitals. Therefore, logical use of the clinical features may help to arrive at a clinical diagnosis and to institute treatment, or otherwise delay in treatment could be detrimental. The aim of this study was to describe clinical and laboratory features of SFG from a prospective case series. Those patients who were presented to Medical Unit, General Hospital, Peradeniya from 2008-2010 with an IgG titer> 1/256 were included in the study. The confirmation of the diagnosis was made with Immunofluorescence antibody assays (IFA) which detected specific rickettsial IgM and IgG antibodies for Rickettsia conorii antigen. Ethical clearance for the study was obtained from ethical review committee, Faculty of medicine, Peradeniya. A total of 247 patients were confirmed to have either primary (19%) or secondary SFG (81%). Of them, 130 (53%) were males and 117 (47%) were females and the mean age of the group was 43 years (12 to 87 years). Patients were presented to the hospital after an average of six days (SO = 4) of fever. A maculopapular skin rash was observed in 78% and a rash with skin necrosis was seen in 6% of patients. Fever (98%), headache (95%), skin rash, arthralgia (70%), myalgia (84%), nausea (51%), vomiting (47%), cough (28%) and conjunctival injections (66%) were the predominant clinical findings. Leucopaenia, thrombocytopaenia and anaemia were seen in 17%, 74% and 19% of patients respectively. Both transaminases, (AST and ALT) were elevated in 66% of cases and ESR was elevatefd in 25 of 37 patients. Rapid response was noted with prompt administration of anti-rickettsial therapy including doxycycline or chloramphenicol. A wider clinical spectrum was noted among SFG patients. Cardinal clinical features such as skin rash, arthritis and response to anti-rickettsial antibiotics would help to arrive at a diagnosis. However, PCR and sero-diagnositic facilities must be available in the hospitals for confirmation of diagnosis.
Chirality dependence of elastic properties of supercarbon nanotubes
(University of Peradeniya, 2011-11-24) Gunatilake, P. A. G.; Herath, S. R.
Carbon nanomaterials are studied extensively among many nanoscale materials investigated during the last decade. Carbon nanotubes (CNT's) are linear fullerenes which can have aspect ratios as large as 103 to 105 . After the discovery of Y branching of CNT's, attention now is on the hierarchical structures (Supercarbon structures) which can be made of Single Walled Carbon Nanotubes (SWCNT's). When SWCNT's are arranged to form a higher order structure, it is called a supercarbon nanostructure. The present study focuses on the versatile elastic properties of Supercarbon nanotubes (SCNT's) which can be mastered by changing various parameters such as geometry and chirality of constituent SWCNT's and the chiral index of the SCNT. A simple mechanics model is used to estimate the stiffness of these supercarbon nanotubes and the results agree well with previous studies on these structures using molecular dynamics modelling. It was found that in super carbon nanotubes with Y junctions, the length of the constituent SWCNT and its chirality, influence the elastic modulus, stiffness and its ultimate tensile strength. Further the study shows that the higher the length of SWCNT the lesser the elastic modulus. It was also seen that for a given length, Lo ,and diameter, d, of SWCNT, the elastic modulus of the super nanotube turns out to be the same for both armchair and zigzag SWCNTs. By manipulating atoms to form different structures, it is possible to obtain different geometries of nano-structured materials. These new materials can be mastered to have desired material properties in any range. Therefore, these can be used to make bullet-proof clothes and vehicles, high-strength composite materials, nano electromechanical devices (NEMS) etc. At the same time, these low density, flexible materials can be used in light weight composite structures.