Faculty of Humanities and Sciences-Q1

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    PublicationOpen Access
    In vitro influence of PEG functionalized ZnO–CuO nanocomposites on bacterial growth
    (PubMed ID, 2024-01-14) Thambiliyagodage, C; Jayanetti, M; Liyanaarachchi, H; Ekanayake, G; Mendis, M; Usgodaarachchi, L
    Polyethyleneglycol-coated biocompatible CuO–ZnO nanocomposites were fabricated hydrothermally varying Zn:Cu ratios as 1:1, 2:1, and 1:2, and their antibacterial activity was determined through the well diffusion method against the Gram-negative Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and the Gram-positive Staphylococcus aureus. The minimum inhibitory concentration and the minimum bactericidal concentration values of the synthesized samples were determined. Subsequently, the time synergy kill assay was performed to elucidate the nature of the overall inhibitory effect against the aforementioned bacterial species. The mean zone of inhibition values for all four samples are presented. The inhibitory effect increased with increasing concentration of the nanocomposite (20, 40 and 60 mg/ml) on all the bacterial species except for S. aureus. According to the MBC/MIC ratio, ZnO was found to be bacteriostatic for E. coli and P. aeruginosa, and bactericidal for S. aureus and K. pneumoniae. Zn:Cu 2:1 was bactericidal on all bacterial species. A bacteriostatic effect was observed on E. coli and P. aeruginosa in the presence of Zn:Cu 1:1 whereas, it showed a bactericidal effect on S. aureus and K. pneumoniae. Zn:Cu 1:2 exhibited a bacteriostatic effect on E. coli while a bactericidal effect was observed for E. coli, P. aeruginosa, and K. pneumoniae. The metal oxide nanocomposites were found to be more sensitive towards the Gram-positive strain than the Gram-negative strains. Further, all the nanocomposites possess anti-oxidant activity as shown by the DPPH assay.
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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
    Persulfate assisted photocatalytic and antibacterial activity of TiO2–CuO coupled with graphene oxide and reduced graphene oxide
    (https://www.nature.com, 2024-05-31) Thambiliyagodage, C; Liyanaarachchi, H; Jayanetti, M; Ekanayake, G; Mendis, A; Samarakoon, U; Vigneswaran, S
    Photocatalysts of TiO2–CuO coupled with 30% graphene oxide (GO) were hydrothermally fabricated, which varied the TiO2 to CuO weight ratios to 1:4, 1:2, 1:1, 2:1 and 4:1 and reduced to form TiO2–CuO/reduced graphene oxide (rGO) photocatalysts. They were characterized using XRD, TEM, SEM, XPS, Raman, and DRS technologies. TiO2–CuO composites and TiO2–CuO/GO degrade methylene blue when persulfate ions are present. Persulfate concentration ranged from 1, 2, 4 to 8 mmol/dm−3 in which the highest activity of 4.4 × 10–2 and 7.35 × 10–2 min−1 was obtained with 4 mmol/dm−3 for TiO2–CuO (1:4) and TiO2–CuO/GO (1:1), respectively. The presence of EDTA and isopropyl alcohol reduced the photodegradation. TiO2–CuO coupled with rGO coagulates methylene blue in the presence of persulfate ions and such coagulation is independent of light. The catalyst dosage and the concentration of the dye were varied for the best-performing samples. The antibacterial activity of the synthesized samples was evaluated against the growth of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumonia. Ti:Cu (1:2)-GO and Ti:Cu (1:4)-GO had the highest antibacterial activity against K. pneumoniae (16.08 ± 0.14 mm), P. aeruginosa (22.33 ± 0.58 mm), E. coli (16.17 ± 0.29 mm) and S. aureus (16.08 ± 0.88).
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    PublicationOpen 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, U
    CoOx 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.