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Author: search.filters.author.Mendis, A

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    PublicationOpen Access
    In vitro release kinetics of bioactive compounds (gallic acid, ellagic acid, and eugenol) from chitosan polymer and the bioactivity of herb-loaded chitosan–CuO nanocomposites
    (Nature Research, 2025-10-13) Ekanayake, G; Wijayawardana, S; Jayanetti, M; Thambiliyagodage, C; Liyanaarachchi, H; Mendis, A
    The biological efficacy of nanocomposites comprised of chitosan, CuO nanoparticles, and extracts of Phyllanthus emblica, and Syzygium aromaticum was studied. The study assessed the pH– and ionic strength-responsive controlled release of the bioactive compounds, gallic acid, ellagic acid and eugenol, from the chitosan biopolymer. Release data were fitted into zero-order, first-order, Korsmeyer–Peppas (KP), Peppas–Sahlin (PS), Higuchi, and Hixson–Crowell kinetic models to evaluate the release mechanism. According to KP and PS models (R2 ≥ 0.96), release was governed by quasi-Fickian diffusion (n < 0.43), where the diffusion occurs along with the polymer relaxation and swelling. P.emblica-coated chitosan (PeC) composite exhibited a burst release at acidic media conditions, and a quasi-Fickian diffusion at pH 5.5–7.4. Higher ionic strength caused salting-in effects for PeC in 0.4 M media, resulting in a transiently increased release. In acidic conditions, diffusion-controlled release was observed for S.aromaticum-coated chitosan (SaC) composite, with the optimal release at pH 4 media. Release was facilitated by hydrophobic nanochannels at elevated pH (8.5–10) and ionic strength of 0.5 M NaCl. The PS model’s relaxation contributions were significant at 0.4 M NaCl and 5 mg drug loading. Both composites demonstrated enhanced release at physiological conditions (0.1–0.2 M NaCl, pH 7.4). Sustained release of SaC was achieved in near-neutral/moderate ionic strength media, whereas PeC exhibited sustained release in acid/low ionic strength media. The PeC and SaC composites showed IC50 values of 10.78 µg/mL and 19.27 µg/mL for the DPPH radical scavenging ability, respectively. Recorded IC50 values for the egg albumin denaturation assay were 467 µg/mL and 390.44 µg/mL, respectively. The antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus showed maximum inhibition zones of 11.83 ± 0.06 mm (Chitosan: CuO 1:2), 12.67 ± 0.20 mm (1:4), 16.50 ± 0.09 mm (1:4), and 11.83 ± 0.08 mm (4:1), respectively. Among the herbal-coated samples, SaC exhibited the highest activity of 23.67 ± 2.84 mm against E. coli
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    PublicationOpen Access
    Fabrication of Naturally Derived Chitosan and Ilmenite Sand-Based TiO2/Fe2O3/Fe-N-Doped Graphitic Carbon Composite for Photocatalytic Degradation of Methylene Blue under Sunlight
    (MDPI, 2023-04-01) Mendis, A; Thambiliyagodage, C; Ekanayake, G; Liyanaarachchi, H; Jayanetti, M; Vigneswaran, S
    first_pagesettingsOrder Article Reprints Open AccessArticle Fabrication of Naturally Derived Chitosan and Ilmenite Sand-Based TiO2/Fe2O3/Fe-N-Doped Graphitic Carbon Composite for Photocatalytic Degradation of Methylene Blue under Sunlight by Amavin Mendis 1,Charitha Thambiliyagodage 1,*ORCID,Geethma Ekanayake 1,Heshan Liyanaarachchi 1ORCID,Madara Jayanetti 1 andSaravanamuthu Vigneswaran 2,3,* 1 Faculty of Humanities and Sciences, Sri Lanka Institute of Information Technology, Malabe 10115, Sri Lanka 2 Faculty of Engineering and Information Technology, University of Technology Sydney, P.O. Box 123, Sydney, NSW 2007, Australia 3 Faculty of Sciences & Technology (RealTek), Norwegian University of Life Sciences, P.O. Box N-1432 Ås, Norway * Authors to whom correspondence should be addressed. Molecules 2023, 28(7), 3154; https://doi.org/10.3390/molecules28073154 Received: 15 March 2023 / Revised: 29 March 2023 / Accepted: 30 March 2023 / Published: 1 April 2023 (This article belongs to the Section Materials Chemistry) Download Browse Figures Versions Notes Abstract Fabrication of chitosan and ilmenite sand-based novel photocatalysts through the catalytic graphitization of chitosan is reported. Nanocomposites consisted of TiO2, Fe2O3 and Fe nanoparticles dispersed on a nitrogen-doped graphitic carbon framework. The surface area, pore volume and macropore structure of the carbon matrix is disturbed by the heterogeneously distributed nanoparticles. The extent of graphitization expanded with increasing metal loading as indicated by variation in the ID/IG ratio. The nanomaterial’s surface consists of Fe3+ and Ti4+, and graphitic, pyridinic and pyrrolic nitrogen were found in the carbon matrix. The band gap values of the composites varied in the 2.06–2.26 eV range. The photocatalytic activity of the synthesized nanomaterials was determined, and the highest rate constant for the photodegradation of methylene blue under sunlight was 4.4 × 10−3 min−1, which resulted with 10 mg/L MB and 25 mg of the best-performing catalyst. The rate constant rose with increasing concentrations of persulfate added to the medium. The rate constant greatly diminished with the addition of isopropyl alcohol as it scavenged hydroxyl radicals. The presence of co-pollutants including Pb2+, rhodamine B, PO43− and Cl− curtailed the rate of reaction. The activity reduced with an increasing number of uses of the catalyst.