Research Papers - School of Natural Sciences
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Publication Open Access The photocatalytic and antibacterial activity of graphene oxide coupled CoOx /MnOx nanocomposites(Elsevier B.V., 2025-02) Liyanaarachchi, H; Thambiliyagodage, C; Jayanetti, M; Ekanayake, G; Wijayawardana, S; Samarakoon, UCoOx and MnOx metal oxide composites were fabricated via co-precipitation varying the Co:Mn (CM) weight ratio as 4:1, 2:1, 1:1, 1:2 and 1:4, and they hydrothermally coupled with 30 wt% of graphene oxide (GO). XRD analysis revealed the presence of Co3O4 and CoO, and Mn2O3 and Mn3O4 phases in pure CoOx and MnOx metal oxides, respectively. The irregularly shaped metal oxide nanocomposites comprised Co3O4, Mn2O3 and Mn3O4 phases and were immobilized on GO. The band gap values of the composites varied in the range of 1.86 – 2.22 eV. The highest photocatalytic activity with a rate constant of 3.5 × 10−3 min−1 was obtained with CMG (1:4). The total removal of MB increased by 55.8 % when CM (1:4) were coupled with GO. The rate of photocatalysis was dramatically increased in the presence of S2O82- and was decreased in the presence of EDTA and isopropyl alcohol. The effect of catalyst dosage was determined by varying the weight to 25, 50, 75, and 100 mg, and the dye concentration was varied in the range of 25, 50, 75 and 100 mg/L. The presence of Pb2+ and Rhodamine B decreased the photocatalytic activity, while it remained the same in the presence of Cl- and PO43- as co-pollutants. The photocatalytic activity of CMG (1:4) was reduced to 72 % upon using the catalyst for five cycles. All the synthesized nanocomposites exhibited greater sensitivity to the Gram-positive strain than the Gram-negative strains.Publication Embargo A Comprehensive Investigation of Microplastic Contamination and Polymer Toxicity in Farmed Shrimps; L. vannamei and P. monodon(Springer Nature, 2025-02-20) Jayaweera, Y. U; Hennayaka, H. M.A.I; Herath, H.M.L.P.B; Kumara, G. M.P; Mahagamage, M.G.Y.L; Rodrigo, U.D; Manatunga, D. CMicroplastic (MP) pollution poses a significant threat to marine ecosystems, seafood safety, and human health. This study investigates the accumulation of microplastics in two commercially important shrimp species, Litopenaeus vannamei (L. vannamei) and Penaeus monodon (P. monodon), sourced from cluster farming sites in Puttalam, Sri Lanka. Shrimp exoskeletons and edible soft tissues underwent rigorous microplastic analysis, including density separation, alkali digestion, stereo microscopy, and Raman spectroscopy. The results revealed high microplastic contamination, with L. vannamei containing an average of 4.99 ± 1.81 MP particles/g and P. monodon containing 1.87 ± 0.55 MP particles/g. Microplastic sizes varied, with L. vannamei predominantly contaminated with 100–250 µm particles and P. monodon with 500 µm—1000 µm particles. Fiber morphotypes were prevalent in L. vannamei, while blue-colored microplastics were dominant in P. monodon. These comprised polystyrene (PS), nylon 6,6, and polyethylene (PE) which were identified by Raman spectroscopy. Additionally, the study investigated the acute toxicity effects of microplastic polymer combinations using a zebrafish embryo model (FET236 assay). Zebrafish embryos exposed to polyethylene-nylon 6,6 combinations exhibited significant adverse effects on hatching, survival, and heart function at lower concentrations, while polyethylene terephthalate-polystyrene combinations showed no considerable effects. These findings underscore the urgent need for monitoring and managing microplastic contamination in shrimp farming areas. Future research should focus on elucidating the ecological impacts and human health risks associated with microplastic exposure.Publication Embargo Facile synthesis of silver/iron-TiO2 nanoparticles for sterilization of Nodal explants of Dracaena sanderiana Sander ex Mast. cvs ‘Gold’ and ‘Victory’ and growth regulator effects on in vitro growth(OICC Press, 2025-02-08) Seneviratne, K.L; Peiris, S. E.; Peiris, C. N; Shashikala, R. P. A; Jayasinghe, S; Kottegoda, NThis study investigates the application of silver/iron-titanate (Ag/Fe-TiO2) nanoparticles (NPs) as a sterilizing agent for in vitro cultures of Dracaena sanderiana cultivars ‘Gold’ and ‘Victory’. The motivation behind this research is to find an effective sterilization method that does not harm plant growth. The Ag/Fe-TiO2 NPs, activated by visible light, exhibit catalytic properties that eliminate harmful microbes such as Escherichia coli, Staphylococcus aureus, and Fusarium spp. The main findings indicate that the combination of Benzyl Amino Purine (BAP) at 1.5 mg/L and Indole Acetic Acid (IAA) at 0.01 mg/L significantly enhances shoot number and length in both cultivars. The use of 200 mg/L Ag/Fe-TiO2 NPs achieved 90% contamination-free cultures in the first cycle, with a slight decrease to 80% in the second cycle and 70% in the third cycle. Importantly, the treatment not only sterilizes but also promotes plant growth, suggesting that Ag/Fe-TiO2 NPs could be a sustainable solution for in vitro plant mass production. © 2025 The Author(s)Publication Open Access Kinetic Study of In Vitro Release of Neem from Chitosan Biopolymer and Assessment of Its Biological Effectiveness(Multidisciplinary Digital Publishing Institute (MDPI), 2025-03-06) Nishshanka, Y; Thambiliyagodage, C; Jayanetti, MThe study examined the sustained release of neem from the polymeric carrier system chitosan by varying the drug content, ionic strength of the release medium, and pH. Six different kinetic models, i.e., Korsmeyer–Peppas (KP), Peppas–Sahlin (PS), Higuchi, Hixson–Crowell, Zero order, and First order were used to investigate the drug release kinetics. Based on the R2 values, the KP and PS models were chosen from the examined models to study the drug release mechanism from the chitosan biopolymer. The values found for model parameters n and m in the KP and PS models differ noticeably, suggesting that Fickian diffusion and Case II relaxation are important components of the neem release mechanism from chitosan. At lower ionic strengths and lower pH values, neem is released from the composite mostly by Fickian diffusion. The diphenyl-2-picrylhydrazyl assay served to assess the composite’s antioxidant properties. The composite’s antioxidant properties ranged from 3.56 ± 1.89% at 10 μg/mL to 51.28 ± 1.14% at 70 μg/mL. The ability of the composite to inhibit the denaturation of egg albumin was also tested and it ranged from 59.68 ± 0.93% at 25 μg/mL to 187.63 ± 3.53% at 1600 μg/mL. The drug composite has exhibited antibacterial activity against Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, and proved to be highly effective against P. aeruginosa at lower concentrations and against S. aureus at higher concentrations. The resulting inhibition zones for P. aeruginosa at 5 and 10 mg/mL concentrations were 16.5 ± 2.25 mm, and 14.83 ± 0.6 mm, respectively, whereas for S. aureus, it was 16.67 ± 0.33 mm at 20 mg/mL. The neem–chitosan composite’s minimum inhibitory concentration/minimum bactericidal concentration ratio for K. pneumoniae, P. aeruginosa, and S. aureus was greater than 4, suggesting that they trigger bacteriostatic outcomes, whereas for E. coli, it was 4, which means that bactericidal effects were evident.Publication Embargo Phylogenetic reassessment and epitypification of Exobasidium vexans causing blister blight of tea(Springer Nature, 2025-05-02) Sinniah, G.D; Kulatunga, D. C.M; Pandey, A. K; Sharma, H. K; Colombage, N. P; Udayanga, DExobasidium vexans is an important tropical phytopathogenic fungus that causes blister blight in tea. Despite its devastating impact on tea cultivation, this pathogen remains poorly studied. In this study, fresh symptomatic leaf samples of blister blight were collected from the main tea-growing regions of Sri Lanka and from Northeast and Eastern India, where the disease was originally reported. Fresh collections obtained from each locality were characterized based on micromorphological characters and molecular data and an epitype was designated. A molecular phylogeny based on the ITS (ribosomal nuclear internal transcribed spacer 1, 5.8S, internal transcribed spacer 2), 28S rDNA (largest subunit of ribosomal gene partial sequence), and TEF-1α (translation elongation factor-1 alpha) revealed that E. vexans collections represent a monophyletic clade closely related to E. reticulatum. This study provides crucial insights into the phylogenetic position and genetic diversity of E. vexans, offering a foundation for future studies on its biology, epidemiology, and management to mitigate impact on global tea production.Publication Open Access Utilization of E-Health Technology in Optimizing Health Services to Increase Patient Satisfaction(Cahaya Ilmu Cendekia, 2025-06-13) Kelegama, T; Ona, R.E; Abdullahi, M. Rurpose of the study: This study aims to explore the utilization of e-health technology in health service delivery and its impact on patient satisfaction through a comprehensive and contextual qualitative approach. Methodology: The approach used in this study is a qualitative approach with the aim of providing a comprehensive and in-depth picture of e-Health-based Health Service Innovation in Increasing Public Satisfaction at Community Health Centers. Main Findings: This study shows that e-health utilization is influenced by the type of service, age, and digital literacy. Online registration is the most preferred, while other features are less understood. Patient experiences include efficiency, digital literacy barriers, technical constraints, and satisfaction that vary. The main influencing factors are age, access to technology, health worker attitudes, and application design. Health workers play a key role in facilitating the digital transition, with patients expecting a simpler, more inclusive, and trained system. Novelty/Originality of this study: This study offers new insights into how digital literacy, patient context, and health worker support affect the acceptance and effectiveness of e-health services. It contributes to knowledge by highlighting the importance of user-centered implementation and the role of health professionals in facilitating digital transitions in healthcare.Publication Embargo Heterojunction and homojunction engineering on multi-shelled confinement structure for CO2 photoreduction to CH4(Elsevier B.V., 2025-10-15) Yang, X; Yang, R; Lu, X; Cao, Y; Ye, P; Zhang, L; Li, K; Li, Z; Jiang, Y; Liu, J; Zhou, Y; Eroglu, Z; Thambiliyagodage, C; Wu, B; Metin, Ö; Zhou, Y; Zhu, WThe underdeveloped CO2 photo-reduction solid-gas mode still relies on precious metals to produce CH4. Fine-tuned ingenious structure and morphology with nonprecious metal can enable better performance with lower cost. We have synthesized and modified a TiO2 with a three-stage cavity and a three-shelled layer, loaded with In2S3 flakes only on the outermost layer. The porous hollow multi-shelled structure can give a sequence of gas diffusion from inside to outside or vice versa. Due to the confinement effect, products generated by the core can only be transferred from the inside to the outside in a unidirectional manner. The In2S3/TiO2 catalysts exhibited high performance comparable to that of conventional noble metal catalysts (e.g., Au-Ag-Pt), with a selectivity of up to 98.28 % for CH4 and a rate of 296.87 μmol·g−1·h−1 without using any co-catalyst or sacrificial agent. Systematic fundamental characterization, as well as in situ characterization and DFT calculations show that homo-junctions consisting of two crystalline phases of TiO2 contribute to the production of more *Hads and *CO. Desorbed CO can be captured and catalyzed by the outer shell In2S3/TiO2 S-scheme heterojunction during diffusion for methanation via formaldehyde intermediate. A series of photoelectrochemical characterizations also confirms that the In2S3/TiO2 hetero-junction improves light absorption and charge separation efficiency. This work provides insight into the future rational design of hollow semiconductors for artificial photosynthesis systems and selective solar fuel production.Publication Open Access Fe3O4 Chitosan Nanocomposite as a pH-Responsive Delivery System for Enhanced Delivery of Punica Granatum L. Polyphenols(American Chemical Society, 2025-10-17) Rukshan, R; Rajapaksha, N; Wijayawardana, S; Thambiliyagodage, C; Senevirathne, U; Jayanetti, M; Samarakoon, UPunica granatum extract (PG), consisting of punicalagin, ellagic acid, and gallic acid, was loaded onto an Fe3O4/Chitosan (Fe3O4@Chi) nanocomposite (Fe3O4@Chi-PG) to enhance pharmacokinetic properties. Fe3O4was synthesized via the coprecipitation method and coupled with chitosan in 2% acetic acid solution via glutaraldehyde cross-linking. The presence of interested polyphenols in the pomegranate extract was confirmed by HPLC analysis, and the extract was post-loaded to the nanocarrier. XRD confirmed the crystallographic orientation of the nanocarrier, and SEM analysis confirmed the successful coupling of Fe3O4onto the chitosan surface during the fabrication of Fe3O4@Chi. BET surface area analysis revealed the presence of micro- and mesopores in the synthesized materials. Significant reduction of the BET surface area and the pore volume of Fe3O4@Chi-PG compared to Fe3O4@Chi suggested the loading of the porous network and surface by PG. The presence of vibrational bands corresponding to the functional groups of the relevant bioactive compounds was confirmed via FT-IR analysis. The IC50values of the nanocomposite for DPPH and egg albumin denaturation assays were 18.69 and 257.69 μg/mL, respectively. The PG encapsulation efficiency of Fe3O4@Chi-PG was reported to be 86.44%. The pH-responsive release of the polyphenols was studied by fitting the release data into five kinetic models, including Korsemeyer–Peppas (KP) and Peppas–Sahlin (PS). The KP and PS models were selected to interpret the release mechanism based on the R2≥ 0.95 value. A combination of Fickian diffusion, relaxation, and swelling dominates the polyphenol release. Quasi-Fickian diffusion is responsible for the release in media with pH 1–6.7, whereas anomalous transport occurs at pH 7.4 (n = 0.46) according to the KP model. Polymer relaxation is the dominant mechanism for the release of bioactive compounds at pH 7.4, as exhibited by R/F > 1. However, the contribution of relaxation to the release of polyphenols at pH 2.5, 4, and 5.5 was negligible according to the parameters (kR= 0). Characteristics of chitosan, including protonation and deprotonation of NH2groups, surface charge of Fe3O4, ionization of COOH and OH groups of the polyphenols, and molecular weight of the active compounds, contributed to the differences in the release behavior.Publication Open Access Correlation between molecular diversity and biochemical traits of edible aerial parts of Basella alba L. from different geographical locations of Sri Lanka(BioMed Central Ltd, 2025-12-29) Dahanayaka, L. W.; Mapa, M. M. S. T; Kadigamuwa, C.C; Udayanga, DBackground: Basella alba L. a widely consumed green leafy vegetable, exhibits considerable nutritional and therapeutic potential attributed to its bioactive constituents. Prior investigations revealed significant variation in phytochemical and antioxidant activity across agro-climatic zones in Sri Lanka, suggesting potential genetic influence. This study is designed to explore underlying genetic variation using RAPD markers to investigate the correlations and contributions of genotype on previously reported bioactivity variation. Results: From a screening of 15 RAPD primers, four primers (OPA 9, OPA 10, OPA 16, and OPB 10) produced, polymorphic, consistent and clearly scorable banding profiles (under optimized PCR conditions) in B. alba L. collected from 15 Sri Lankan locations. These primers collectively yielded 36 bands, 35 of which were polymorphic, resulting in a high polymorphism rate of 97.2%, confirming the informativeness of the selected primers for genetic diversity analysis. Genetic similarity was assessed using Jaccard’s coefficient in NTSYSpc.v2·10e, revealing values ranging from 0.44 to 0.97, with the highest similarity from the samples from Ratnapura and Kandy and the lowest similarity in Ratnapura and Kalutara. A dendrogram constructed via UPGMA grouped the samples into two major clusters and five sub-clusters, demonstrating substantial genetic differentiation influenced by geographic origin. Cluster I included Ratnapura and Kandy, while the remaining samples formed Cluster II and its subgroups, each representing different ecological zones. When compared to the phytochemical and antioxidant clustering data of the previous study, partial correspondence was observed. A Mantel test comparing genetic diversity and biochemical/antioxidant potential revealed a weak negative correlation which was not significantly different. Some of the locations within similar genetic cluster shared similar biochemical traits, while others diverged significantly, indicating that environmental conditions also influence bioactive compound synthesis. Notably, Cluster I (Ratnapura and Kandy) showed both genetic similarity and lower antioxidant traits. Samples from Ella and Polonnaruwa showed similar bioactive traits even though they were grouped into different genetic clusters. Conclusion: These findings suggest that both genetic makeup and environmental adaptation contribute to observed biochemical diversity in B. alba L. with a clear geographical correlation. This study highlights the value of integrating molecular and biochemical analyses to develop regionally adapted B. alba L. cultivars with enhanced nutritional traits, supporting sustainable agriculture in Sri Lanka and beyond.Publication Open Access Impact of geographical variation on nutritional and antioxidant properties of Basella alba L. from Sri Lanka(BioMed Central Ltd, 2025-01-27) Dahanayaka, L. W.; Mapa, M. M. S.T; Kadigamuwa, C.C; Udayanga, DBackground: Basella alba L. (Malabar spinach) is a widely consumed leafy vegetable, well known for its nutritional and therapeutic properties. These properties arise from the availability of essential nutrients, phytochemicals, and antioxidant potential, which may vary depending on environmental factors induced by the geographical location. In this study our aim is to investigate the correlation between the geographical location and proximate composition, phytochemical content, and antioxidant activity of B. alba harvested from fifteen locations in Sri Lanka. Results: According to the statistical analysis by ANOVA and Tukey test, the results of proximate analysis confirmed that samples from different locations showed statistically significant variance in nutritional content. Furthermore, phytochemical content and antioxidant potential varied showing a significant difference between locations in total chlorophyll (27.53 to 6.69 µg/g dry weight), carotene (4.54 to 1.15 µg/g dry weight), total flavonoid content (10.54 to 3.94 mg/g dry weight in Quercetin equivalents), total phenolic content (8.33 to 0.46 mg/g dry weight in gallic acid equivalents), 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity (38.03–11.4% inhibition), and ferric ion-reducing antioxidant power (1.23 to 3.76 mg/g dry weight in ascorbic acid equivalents) (p < 0.05). The Pearson correlation showed a strong positive correlation between total phenolic content and antioxidant activity. Principal component analysis indicates the role of antioxidant activity and chlorophyll content in location differentiation, forming distinct clusters. Cluster analysis categorized samples into four groups, linking biochemical traits to agro-climatic zones. The principal component analysis and cluster analysis showed a close relationship between some locations due to their high antioxidant and phytochemical accumulation. Conclusion: This study exhibits the importance of geographical location on the phytochemical profile and antioxidant properties of B. alba. These findings can be used to refine optimal cultivation sites for B. alba to enhance the efficacy of its nutraceutical and pharmaceutical potential.