Browsing by Author "Masika, Eric"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Antibacterial activity of green synthesized silver nanoparticles using Citrullus lanatus fruit rind extract
    (Kenya Chemical Society, 2020) Ndikau, Michael; Naumih, Noah; Andala, Dickson; Masika, Eric
    The increased resistance of microbes to current antibiotics calls for development of new effective antimicrobial agents. Metal nanoparticles such as silver nanoparticles have continued to attract increased research interest in the recent past because of their wide range of applications such as in the areas of chemical sensing, nanomedicine and electronics. In this work, spherical AgNPs (17.96 ± 0.16 nm in diameter) synthesized via a green method using Citrullus lanatus (water melon) fruit rind extract were evaluated for antimicrobial activity against clinical isolates of Escherichia coli (E.coli) and Salmonella typhi (S.typhi) bacteria using the discdiffusion method. The Minimum Inhibition Concentration (MIC) value of the nanoparticles was found to be 45.00 ± 0.01 g/ml for S.typhi and 38.50 ± 0.00 g/ml for E.coli while the Minimum Bactericidal Concentration (MBC) value was found to be 60.00 ± 0.05 g/ml for S.typhi and 50.00 ± 0.00 g/ml for E.coli. This study demonstrated that these two bacterial strains were susceptible to the green synthesized AgNPs.
  • Thumbnail Image
    Item
    Controlling Rate of Release of Tsetse Fly Repellent Blend byEncapsulating in β-Cyclodextrin Nanoparticles
    (Journal of Nanotechnology, 2025-05) Ratemo, Bernadatte M.; Wachira, Benson M.; Masika, Eric; Ng’ang’a, Margaret M.; Hassanali, Ahmed; Mireji, Paul O.
    Tsetse flies are major vectors of African trypanosomiasis, with devastating medical and veterinary consequences in sub-Saharan region of Africa. Insect repellents are promising tool for control of tsetse flies in the region. A four-component tsetse-repellent blend (δ-nonalactone, heptanoic acid, 4-methylguaiacol, and geranyl acetone) previously formulated and optimized was encapsulated in β-cyclodextrin for a slow controlled release. Here, we explored various methods of microencapsulating (kneading, coprecipitation, heating, or freeze-drying) tsetse fly repellent blend in β-cyclodextrin nanoparticles. We assessed release kinetics of the blends and individual compounds using gas chromatography linked with flame ionization detector and evaluated laboratory and field responses (repellence) of the flies by the encapsulated blends. We compared individual performances of releases kinetics of the encapsulated blend relative to nonencapsulated composites. Overall, kneading, coprecipitation, heating, and freeze-drying microencapsulation techniques retained 72.0%, 61.0%, 59.5%, and 57.3% of the blend, respectively. Release rates of blends in 400- and 200-microns thick polythene sachets were 6.73 and 11.82 mg/h, respectively, significantly higher (p < 0.05) than that of the kneaded encapsulated blend (5.35 mg/h). Laboratory and field responses of tsetse flies to the unencapsulated native (sachet) and kneaded encapsulated odor blends confirmed our laboratory findings. Microencapsulation technology of repellent odors can be used for controlled release of active molecules in order to give an extended protection period, potentially reducing operational cost in programs for control of tsetse flies and related insect vectors.
  • Thumbnail Image
    Item
    Green Synthesis and Characterization of Silver Nanoparticles Using Citrullus lanatus Fruit Rind Extract
    (Hindawi Publishing Corporation, 2017) Ndikau, Michael; Noah, Naumih M.; Andala, Dickson M.; Masika, Eric
  • Thumbnail Image
    Item
    ZnO Nanoparticles (ZnO-NPs): Synthesis Using Tithonia diversifolia, Characterization and in-vitroAntimicrobial Bioassays
    (IOSR Journal of Applied Chemistry, 2020) Wafula, Bonface Juma; Masika, Eric; Onindo, Charles
    ZnO is among leading metal oxide nanoparticles (MO-NPs). The conventional physical and chemical synthesis protocols require use of sophisticated equipment and many chemicals which may be hazardous. In this research, ZnO-NPs were prepared via a straightforward environmentally benign technique; employing Tithonia diversifolia as a reductant. Zinc nitrate solution was mixed with TDLE in the ratio of 3:1 respectively and incubated in an ultra-sonication bath. The precipitates were centrifuged at 5000 rpm for 15 minutes followed by washing with distilled water. A peak at 374 nm, as measured by UV-Vis, confirmed formation of nanoZnO.Presence of ZnO was shown by a new peak at 668.35 cm -1 in the ZnO-TDLE FTIR spectrum. The crystalline size of the sample was estimated as 20.91 nm by Debye-Scherer formula. Identification and quantification of elements was performed by X-Ray Fluorescence (XRF) analysis, which showed 91.823% Zn in the sample. The synthesized nano-ZnO showed promising antibacterial activity. The bioactive nature of ZnONPs, as demonstrated in this research, puts the nano-ZnO at pole position for the formulation of novel antimicrobial agents