Taofeek A. Yekeen

Biogenic synthesis of silver nanoparticles using a pod extract of Cola nitida: Antibacterial and antioxidant activities and application as a paint additive

Abstract This work reports the biogenic synthesis of silver nanoparticles (AgNPs) using the pod extract of Cola nitida, the evaluation of their antibacterial and antioxidant activities, and their application as an antimicrobial additive in paint. The AgNPs were characterized with UV–Vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The AgNP solution was dark brown with a maximum absorbance occurring at 431.5 nm. The FTIR spectrum showed strong peaks at 3336.85, 2073.48, and 1639.49 cm−1, indicating that proteins acted as the capping and stabilization agents in the synthesis of the AgNPs. The AgNPs were spherical, with sizes ranging from 12 to 80 nm. Energy dispersive X-ray (EDX) analysis showed that silver was the prominent metal present, while the selected area electron diffraction pattern conformed to the face-centred cubic phase and crystalline nature of AgNPs. At various concentrations between 50 and 150 μg/ml, the AgNPs showed strong inhibition of the growth of multidrug resistant strains of Klebsiella granulomatis, Pseudomonas aeruginosa, and Escherichia coli. In addition, at 5 μg/ml, the AgNPs completely inhibited the growth of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, A. flavus and A. fumigatus in a paint-AgNP admixture. The AgNPs exhibited a potent antioxidant activity with an IC50 of 43.98 μg/ml against 2,2-diphenyl-1-picrylhydrazyl and a ferric ion reduction of 13.62–49.96% at concentrations of 20–100 μg/ml. This study has demonstrated the biogenic synthesis of AgNPs that have potent antimicrobial and antioxidant activities and potential biomedical and industrial applications. To the best of our knowledge, this work is the first to use the pod extract of C. nitida for the green synthesis of nanoparticles.

Biomedical and Catalytic Applications of Gold and Silver-Gold Alloy Nanoparticles Biosynthesized Using Cell-Free Extract of Bacillus Safensis LAU 13: Antifungal, Dye Degradation, Anti-Coagulant and Thrombolytic Activities

This study investigated the green biosynthesis of gold (Au) and silver-gold alloy (Ag-Au) nanoparticles using cell-free extract of Bacillus safensis LAU 13 strain (GenBank accession No: KJ461434). The biosynthesized AuNPs and Ag-AuNPs were characterized using UV-Vis spectroscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy. Evaluation of the antifungal activities, degradation of malachite green, anti-coagulation of blood, and thrombolysis of human blood clot by the biosynthesized nanoparticles were investigated. The AuNPs and Ag-AuNPs had maximum absorbance at 561 and 545 nm, respectively. The FTIR peaks at 3318, 2378, 2114, 1998, 1636, 1287, 446, 421 cm-1 for AuNPs; and 3310, 2345, 2203, 2033, 1636, 1273, 502, 453, 424 cm-1 for Ag-AuNPs indicated that proteins were the capping and stabilization molecules in the biosynthesized nanoparticles. The particles were fairly spherical in shape with size of 10-45 nm for AuNPs and 13-80 nm for Ag-AuNPs. Moreover, energy dispersive X-ray analysis of AuNPs revealed gold as the most prominent metal in the AuNPs solution, while silver and gold were the most prominent in the case of Ag-AuNPs. Selected area electron diffraction showed the biosynthesized nanoparticles as crystal structures with ring shape pattern. AuNPs and Ag-AuNPs displayed growth inhibitions of 66.67-90.78% against strains of Aspergillus fumigatus and A. niger at concentration of 200 μg/ml, and remarkable degradation (> 90%) of malachite green after 48 h. Furthermore, the nanoparticles prevented coagulation of blood, and also completely dissolved blood clots, indicating the biomedical potential of AuNPs and Ag-AuNPs in the management of blood coagulation disorders. This is the first report of the synthesis of AuNPs and Ag-AuNPs using a strain of B. safensis for biomedical and catalytic applications.

Bacteriology and genotoxicity of some pharmaceutical wastewaters in Nigeria

Wastewaters from two pharmaceutical production processes, cotrimoxazole B wastewater (BWW) and Piriton wastewater (PWW), were examined microbiologically and for physico-chemical parameters. Furthermore, the wastewaters were also screened for genotoxicity using Allium cepa assay to assess the risk associated with the discharge of untreated pharmaceutical wastewaters into the environment. The effluents induced various types of chromosomal aberrations, namely, disturbed spindle, vagrant and chromosome bridge, and also showed a dose-dependent reduction in the number of dividing cells. The mitotic inhibition ranged from 38.6 to 67.2%. The mean root length at 20% of BWW and all concentrations except 1% of PWW were significantly different from the control values (p < 0.05). The EC50 of the root growth inhibition was 4.17 and 12.45% for PWW and BWW, respectively. The wastewater physico-chemical analysis revealed that most parameters were within the allowable limits. The wastewaters had similar microbial load index of 107 cfu ml−1, indicating dense populations of bacteria, which may be due to the richness of the wastewaters in nutrients particularly sulphate, nitrate and phosphate. Coliform bacteria concentrations in the PWW and BWW wastewaters were 50MPN/100 ml and 550MPN/100 ml, respectively. The identified bacterial isolates included Staphylococcus aureus, Escherichia coli, Serratia marcescens, Klebsiella sp, Streptococcus pyogenes, Bacillus licheniformis, Yersinia sp, Proteus vulgaris and Bacillus subtilis. The resistance of the bacterial isolates ranged from 10% for gentamicin to 100% for augmentin, amoxycillin, cloxacillin and nalidixic acid. PWW isolates were more resistant. Seven patterns of multiple drug resistance ranging from 5 to 11 antibiotics were obtained amongst the isolates.

Evaluation of toxic effects of lambdacyhalothrin on the haematology and selected biochemical parameters of African catfish Clarias gariepinus

The potential acute and chronic toxic effects of lambdacyhalothrin (LCT) on African catfish Clarias gariepinus were evaluated. Lethal concentrations (LC) were determined using 0.2, 0.3, 0.4, 0.5 and 0.6 ppm of LCT. Haematological and biochemical parameters were evaluated on fish treated with 0.001, 0.005, 0.010 and 0.025 ppm of LCT. Blood samples were collected on the 15th, 30th, 45th and 60th day of exposure and 60th day of recovery. Fish treated with LCT showed behavioural abnormalities compared to the control, which included reduced swimming activity, loss of equilibrium, vertical hanging and air gulping. The LC50 values of LCT were 0.571, 0.380, 0.337 and 0.325 ppm at the exposure time of 24, 48, 72 and 96 h, respectively. Significant reductions (p ⩽ 0.05) were observed in the packed cell volume, red blood cell count and haemoglobin concentration values in exposed fish. Initial increase in the value of the white blood cell count was observed, which later declined. Serum glucose increased significantly...

Enterococcus species for the one-pot biofabrication of gold nanoparticles: Characterization and nanobiotechnological applications

In the current work, cell-free extracts of four strains of non-pathogenic Enterococcus species of food origin, were studied for the green synthesis of gold nanoparticles (AuNPs), and characterized by UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The AuNPs were evaluated for their Anopheles gambiae larvicidal, dye degradation, antioxidant and thrombolytic activities. The blue-black colloidal AuNPs which absorbed maximally at 549-552nm were nearly spherical in shape, and crystalline in nature with size of 8-50nm. The EDX spectra showed formation of AuNPs to the tune of 89-94%. The prominent FTIR peaks obtained at 3251-3410, 2088 and 1641-1643cm-1 alluded to the fact that proteins were involved in the biofabrication and capping of AuNPs. AuNPs degraded methylene blue and malachite green by 24.3-57.6%, and 88.85-97.36% respectively in 24h, whereas at 12h, larvicidal activities with LC50 of 21.28-42.33μg/ml were obtained. DPPH scavenging activities of 33.24-51.47% were obtained for the biosynthesized AuNPs. The AuNPs prevented coagulation of blood and also achieved 9.4-94.6% lysis of blood clot showing potential nanomedical applications. This study has presented an eco-friendly and economical synthesis of AuNPs by non-pathogenic strains of Enterococcus species for various nanobiotechnological applications.

Cytogenotoxicity potentials of cocoa pod and bean-mediated green synthesized silver nanoparticles on Allium cepa cells

Abstract Nanotechnology is a ground-breaking scientific innovation, but there are possible hazards to environment and human health. Therefore, there is a need to understand the toxic potential of nanoparticles. Cytotoxic and genotoxic effects of biogenic cocoa pod husk and cocoa bean silver nanoparticles (CPHE-AgNPs and CBE-AgNPs, respectively), and silver nitrate salts (Ags) were evaluated using the A. cepa root assay. Twenty onion bulbs were exposed to various concentrations (0.01, 0.10, 1.0, 10.0, and 100.0 μg ml–1) of AgNP and Ags solutions. Effects on cell division and chromosomes were observed at 24, 48 and 72 h, while root number and growth inhibition were evaluated at 72 h. Both biogenic AgNPs have potential to be cytotoxic with disturbances to mitotic phases. Mitotic index was less than one half the values of control for almost all concentrations throughout exposure periods. The highest concentration of both AgNPs induced complete cell arrest at both 48 and 72 h, except for Ags. Induction of chromosomal aberrations (chromosomal bridge, c-mitosis, vagrant chromosome, sticky chromosome) pointed to potential for genotoxicity. AgNPs demonstrated a clear mito-depressive effect culminating in growth inhibition of the A. cepa roots, except for 0.01 μg ml–1 of CPHE-AgNPs (p < 0.05). EC50 values showed that growth inhibition was in the order of CPHE-AgNPs>Ags>CBE-AgNPs. While indiscriminate usage of AgNPs might have an impact on the health status of exposed organisms, raising concerns, the cell arresting potential of both AgNPs can be explored in the control of growth of cancerous cells.

Fungal xylanases-mediated synthesis of silver nanoparticles for catalytic and biomedical applications

Green synthesis of nanoparticles has fuelled the use of biomaterials to synthesise a variety of metallic nanoparticles. The current study investigates the use of xylanases of Aspergillus niger L3 (NEA) and Trichoderma longibrachiatum L2 (TEA) to synthesise silver nanoparticles (AgNPs). Characterisation of AgNPs was carried out using UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy, while their effectiveness as antimicrobial, antioxidant, catalytic, anticoagulant, and thrombolytic agents were determined. The colloidal AgNPs was brownish with surface plasmon resonance at 402.5 and 410 nm for NEA-AgNPs and TEA-AgNPs, respectively; while FTIR indicated that protein molecules were responsible for the capping and stabilisation of the nanoparticles. The spherical nanoparticles had size of 15.21-77.49 nm. The nanoparticles significantly inhibited the growth of tested bacteria (63.20-88.10%) and fungi (82.20-86.10%), and also scavenged DPPH (37.48-79.42%) and hydrogen peroxide (20.50-96.50%). In addition, the AgNPs degraded malachite green (78.97%) and methylene blue (25.30%). Furthermore, the AgNPs displayed excellent anticoagulant and thrombolytic activities using human blood. This study has demonstrated the potential of xylanases to synthesise AgNPs which is to the best of our knowledge the first record of such. The present study underscores the relevance of xylanases in nanobiotechnology.

Safety evaluation of green synthesized Cola nitida pod, seed and seed shell extract-mediated silver nanoparticles (AgNPs) using an Allium cepa assay

Abstract The increase in the use of nanoparticles in various fields of human endeavours calls for the need to understand the toxic potential of green synthesized nanoparticles. Cytogenotoxic potentials of green synthesized Cola pod (Cp-AgNPs), seed (Cs-AgNPs) and seed shell (Css-AgNPs) silver nanoparticles and silver nitrate salts (Ags) were evaluated using an A. cepa assay. Twenty onion bulbs were exposed to 0.01, 0.10, 1.0, 10.0, and 100.0 μg/ml AgNPs and Ags solutions. Microscopic evaluation was performed at 24, 48 and 72 h with 5000 cells per concentration scored for chromosomal aberrations, while the effects on the root growth were evaluated at 72 h. The observed dividing cells and mitotic inhibition were dose-dependent for the three AgNPs and Ags at 24, 48 and 72 h. Mitotic index obtained for 1.0, 10 and 100 μg/mL at all times of evaluation were less than half the value of the negative control, while cell arrest was only observed at 72 h at a concentration of 100 μg/mL for the three AgNPs. The chromosomal aberrations observed were c-mitosis, a chromosome bridge, a vagrant chromosome, and a sticky chromosome, which indicate the potential of AgNPs for genotoxicity. The mean root length of A. cepa treated with AgNPs showed a dose-dependent significant decrease compared to the control, indicating their inhibitory potential, but the mean root lengths were found to be lower at all concentrations compared to those treated with Ags, thus showing the attenuation of growth inhibition. The EC50 values revealed the order of growth inhibition as Ags>Cp-AgNPs>Css-AgNPs>Cs-AgNPs. The cytogenotoxic potential of the AgNPs suggests that caution should be exercised in their usage to prevent environmental pollution.