Faculty of Applied Sciences
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Item Biogenic synthesis of zinc oxide nanoparticles mediated by the extract of Terminalia catappa fruit pericarp and its multifaceted applications(American Chemical Society (ACS), 2023-10-09) Fernandes, Cannon Antony; Jesudoss M, Nameeta; Nizam, Aatika; Krishna, Suresh Babu Naidu; Lakshmaiah, Vasantha VeerappaZinc oxide nanoparticles (ZnO-NPs) were bio synthesized by using the pericarp aqueous extract from Terminalia catappa Linn. These NPs were characterized using various analytical techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, ultraviolet (UV) spec troscopy, dynamic light scattering (DLS), and scanning electron microscopy (SEM), and XRD studies of the nanoparticles reported mean size as 12.58 nm nanocrystals with highest purity. Further SEM analysis emphasized the nanoparticles to be spherical in shape. The functional groups responsible for capping and stabilizing the NPs were identified with FTIR studies. DLS studies of the synthesized NPs reported ζ potential as −10.1 mV and exhibited stable colloidal solution. These characterized ZnO-NPs were evaluated for various biological applications such as antibacterial, antifungal, antioxidant, genotoxic, biocompatibility, and larvicidal studies. To explore its multidimensional application in the field of medicine. NPs reported a potential antimicrobial activity at a concentration of 200 μg/mL against bacterial strains in the decreasing order of Streptococcus pyogenes > Streptococcus aureus > Streptococcus typhi > Streptococcus aeruginosa and against the fungi Candida albicans. In vitro studies of RBC hemolysis with varying concentrations of NPs confirm their biocompatibility with IC50 value of 211.4 μg/mL. The synthesized NPs’ DPPH free radical scavenging activity was examined to extend their antioxidant applications. The antiproliferation and genetic toxicity were studied with meristematic cells of Allium cepa reported with mitotic index (MI index) of 1.2% at the concentration of 1000 μg/mL. NPs exhibited excellent Larvicidal activity against Culex quinquefasciatus larvae with the highest mortality rate as 98% at 4 mg/L. Our findings elicit the therapeutic potentials of the synthesized zinc oxide NPsItem Green synthesis, characterization, biological and electrochemical studies of indole pyrazole capped nanomaterials(2021) Majola, Senzekile; Sabela, Myalowenkosi Innocent; Gengan, Robert Moonsamy; Makhanya, Talent RaymondGreen nanomaterial synthesis has become more popular and, with the need for greener approaches to counter higher costs and higher energy usage for chemical and physical processes, scientists are searching for cheaper methods of synthesis. The use of plant extracts has been one of the popular methods because they are known to reduce metal ions from their surface. Green synthesized nanomaterials are relatively unstable compared to chemical and physical methods hence new stabilizing agents (indole pyrazole ligands) have been introduced in this study. The nanomaterials are being applied in electrochemical and biological systems, their behavior may not be as efficient as the new capped nanomaterials. Hence, a comparison of capped and uncapped nanomaterials was studied. Indole pyrazole capped selenium nanoparticles (TRPIDC-CH3 SeNPs), Indole pyrazole capped silver nanoparticles (TRPIDC-CH3 AgNPs), and Indole pyrazole capped cadmium sulphide quantum dots (TRPIDC-CH3 CdSQDs) were successfully synthesized using plant extracts of allium sativum cloves, pelargonium, and moringa leaves, respectively. Green synthesized TRPIDC-CH3 capped nanomaterials were characterized by UV-vis spectrophotometry, HR-TEM, and FTIR analysis. The results revealed no differences in shape, color, functional groups involved, or wavelength, but an increase in average diameter as compared to uncapped nanomaterials. Furthermore, green-fabricated synthesized nanomaterials were tested to evaluate their cytotoxicity against MCF-7, A549, and HEK293 cells. The overall cytotoxicity was low: a dose-dependent increase in cytotoxic activity was observed for each of the nanomaterials, as the concentration increased from 50 μg/ml to 100 μg/ml. Interaction of TRPIDC-CH3 capped and uncapped nanomaterials with human serum albumin (HSA) was investigated under physiological conditions (PBS, pH 7.3) by UV–Vis, and fluorescence. Fluorescence analysis at different temperatures revealed the quenching of HSA. The results showed a single class of binding site and a static ( uncapped) and dynamic (TRPIDC-CH3 capped) quenching mechanism between nanomaterials and HSA. The thermodynamic results indicated van der Waals forces and hydrogen bonds (uncapped) and hydrophobic interactions (TRPIDC-CH3 capped) were dominant. Dual enzyme electrode for the indirect detection of adenosine triphosphate (ATP),using a redox probe as a reference peak, was developed by co-immobilization of the enzymes glucose oxidase (GO) and hexokinase (Hex) and nanomaterials. The implementation of a simple electrochemical technique to co-immobilize enzymes on electrode surfaces demonstrates a significant improvement in the sensitivity, reproducibility and ease of fabrication of ATP biosensors. However, the addition of the TRPIDC-CH3 ligand to QDs affected the surface area and conductive activity of the sensor leading to a decrease in sensitivity and weakening the electrochemical stability of the QDs. The concept proposed provides the technological basis for a new generation of fast, responsive and robust biosensors for the detection of ATP through indirect detection. Keywords: Adenosine triphosphate (ATP); Indole pyrazole ligand (TRPIDC-CH3); Selenium Nanoparticles (SeNPs); Cyclic voltammetry (CV); Square wave voltammetry (SWV); Hexokinase (Hex); Glucose oxidase (GO); Human serum albumin (HSA); MTT assay; MCF-7, A549, and HEK293 cells.Item The efficiency of phytoremediation using Panicum maximum and TiO2 nanoparticles(2021) Cibane, Nozipho Sinenhlanhla; Mdluli, Phumlani Selby; Moodley, K.G.; Arthur, G.D.This study focused on the application of Panicum maximum (guinea grass) for evaluating the phytoremediation of titanium dioxide nanoparticles (nTiO2). This study was done to explore the ability of Panicum maximum Jacq as a hyperaccumulator for phytoremediation of nTiO2. Titanium dioxide has steadily become more abundant in our environment over the years due to human activities, and this could potentially harm the environment. Panicum maximum (guinea grass) is a non-vascular plant with a short life cycle. It is well adapted to a wide variety of conditions. It originated from Africa but is presently found and cultivated in almost all parts of the world with tropical climates. It is loosely to densely tufted, with short rhizomous rooting at the lower nodes. Leaf blades are linear to narrowly lanceolate. Plant to metal oxide nanoparticle interaction was investigated by germination of seeds in the presence of titanium dioxide nanoparticles (nTiO2). The uptake of nTiO2 by Panicum maximum Jacq was evaluated after treatment of the seedlings with nTiO2. The synthesized nTiO2 was characterized, using Transmission Electron Microscope, Scanning Electron Microscope. Energy Dispersive Spectroscopy (EDX), and X-ray Diffraction (XRD). The average mean particle distribution was analyzed using Image J. The Image J analysis showed that the average particle distribution of nTiO2 was 9 nm. The TEM and SEM results revealed that the particles in the nTiO2 were spherical in shape. The XRD analysis revealed that the nTiO2 was predominantly 67.1% and 32.9% of anatase and rutile forms, respectively. Metal uptake was analyzed using the Inductively Coupled Plasma – Optical Emission Spectrometer method (ICP-OES) after the plants were digested using the wet digestion and microwave digestion methods. The ability of the plants to translocate the metals to the aerial parts of the plants (Translocation Factor - TF) was evaluated for the metal using concentration ranging from 5 ppm to 50 ppm. It was observed that the root had the highest concentration of nTiO2 while the lowest uptake was found in the leaf. The TF was highest for the 5 ppm sample. The roots with the shortest length, which indicated stress/toxicity were that of the plants which were treated with 50 ppm of nTiO2. These also had the highest accumulated nanoparticles which suggested that these plants were negatively impacted by a higher concentration of nTiO2. The standard with 5 ppm treatment showed the highest value of the translocation factor which suggested that at this concentration the nanomaterial aided and catalyzed the movement of nanoparticles to the aerial parts of the plant. The results suggested that seed treated with nanoparticles before planting for phytoremediation purposes could increase the metal uptake selectivity.Item Development of a gold nanoparticle based colorimetric sensor kit for the analysis of sodium chloride levels in seawater(2019) Mbambo, Andile Truelove; Madikizela, Lawrence Mzukisi; Mdluli, Phumlani SelbyIn this study, colorimetric assay was used to develop a gold nanoparticle enabled optical sensor for the analysis of sodium chloride in seawater. Sodium chloride has a major effect in the seawater’s salinity level, thus, this has led to the design of a colorimetric device that is selective to sodium chloride, which can be used for both seawater and the nearby estuarine water. Flocculation assay based on gold nanoparticles was used to optimise the colorimetric response of the selected sodium chloride concentration range (5-40 ppT) for the developed kit. Polydispersed and stable gold nanoparticles were synthesized via the Turkevich method using tri-sodium citrate as a reducing and capping agent. The optical properties of the as-synthesized gold nanoparticles were characterized by Ultra-Violet- Visible spectroscopy where the existence of the Surface Plasmon Resonance (SPR) absorption peak was observed at 525 nm. Transmission Electron Microscopy (TEM) image revealed the morphology of the gold nanoparticles to be isotropic/ spherical with a calculated average size of gold nanoparticles which was found to be 7 nm. The introduction of sodium chloride to gold nanoparticles solution resulted in aggregation which was indicated by the change of colour from red to blue. Scanning Electron Microscopy (SEM) images confirmed the spherical morphology of the gold nanoparticles. The gold nanoparticles with sodium chloride image showed crystals of the salt covering the aggregated gold nanoparticles inferring that the tri- sodium citrate barrier on the surface of the nanoparticles had been broken. In the Fourier-transform Infrared Spectroscopy spectrum (FTIR), the existence of hydroxyl was observed in the gold nanoparticles solution at 3540 cm-1 due to the deionised water used in preparation of all solutions. The carbonyl groups observed at 1782 cm−1, 1520 cm-1 and 1290 cm-1 in the gold nanoparticles spectrum were due to the citrate capping the nanoparticles. Ultraviolet-Visible Spectroscopy (UV-Vis) spectroscopy was also used to validate the colorimetric method as the application of gold nanoparticles is based on solution colour convergence from wine red to blue upon analyte introduction. The colorimetric assay of the sodium chloride concentration range gave distinguishable colour shades which were visually observed. The intensity of the colour in standard solutions increased as the concentration of NaCl was increased. A red shift was observed in the UV-Vis spectrum due to the increase in sodium chloride concentration. A decrease in the 525 nm SPR peak was observed with an increase of another SPR peak at longer wavelengths around 660 nm. Images of the colorimetric assay were analysed using the Colorgrab application. Results of this analysis showed that the colour intensities in the Greyscale percentages were decreasing with increasing sodium chloride concentration and were in the range of 42.33-57.66%. The red green blue (RGB) colour model analysed by ImageJ software revealed that the red colour of the gold nanoparticles gradually disappeared with the development of the blue colour as the concentration of sodium chloride was increased in solution. Commission Internationale d’Eclairage (CIE) Lab colour management method validated the colour similarities and differences of the sodium chloride colorimetric assay. The sodium chloride quantification colour wheel/disk was then fabricated using the RBG colour model values. The developed colorimetric device was applied to screen the level of salinity along the coastal seawater and estuaries of Durban in KwaZulu-Natal. Results of this colorimetric method had a linearity value of 0.9980, a detection and quantification limits of 1.18 ppT and 3.57 ppT, respectively. The concentrations of NaCl in the tested seawater and estuary samples were in the ranges of 30-35 ppT and 5-30 ppT, respectively. The measured concentrations of sodium chloride in water samples using the proposed colorimetric method were in agreement with those observed when using the traditional methods such as ion chromatography and titration. Overall, gold nanoparticles based colorimetric sensor used for the analysis of sodium chloride in seawater and estuarine water was rapid, cost effective, accurate, precise, sensitive, and selective.Item Gold nanoparticle-based lateral flow kit for in vitro detection of malaria antibodies(2018) Mthembu, Christian Lungani; Mdluli, Phumlani Selby; Mlambo, Mbuso; Gumede, HalalisaniThis study involves the development of three-dimensional dual lateral flow diagnostic assays. These assays were fabricated with quick response (QR) barcodes to ease the accessibility and transfer test data. The assays were designed to also improve the collection and transfer of survey from point-of-care facilities to centralized laboratories, thus, these would help to speed-up response to disease out-break. The study introduces the fabrication of two barcode based malaria diagnostic in the field of diagnostics. Two lateral flow kits were modified with two QR barcodes and three QR barcodes encoded with Google analytics codes for the detection and real-time tracking of malaria lateral flow which was designed to detect Plasmodium lactate dehydrogenase (pLDH). The fabrication of test kit was achieved by attaching two and three QR barcodes into two different test kits which were encoded with websites that were linked to Google analytics website as a tracking and performance monitor. Gold nanoparticles (AuNPs) were used as a substrate, where optical and structural properties were studied using UV/Visible spectroscopy, fluorescence spectroscopy, and transmission electron microscopy (TEM). The anti-mouse IgG antibody was used as a secondary antibody to act as control and the anti-(pLDH) was stripped on the test line. Phosphate buffer was used as a mobile phase solution. The antibody binding with pLDH antigen showed red test line indicating a positive test. Two diagnostic kits for rapid detection of pLDH were developed and validated for the detection of malaria antigen with lowest detectable recombinant concentration of 10 ng.mL-1. The diagnostic kits were incorporated with two and three optimally angled QR barcodes for identifying positive and negative. The second three QR barcode embedded test kit identified positive, negative and invalid using tracked website. These QR barcodes enabled massive results and tracking with precise location of the test through Google Analytics.Item Active targeting of cancer cells using gemcitabine conjugated platinum nanoparticles(2017) Odayar, Kriya; Odhav, Bharti; Mohanlall, VireshNanotechnology is explained as the science of engineered materials and systems on a molecular scale. This innovation is currently used in a wide variety of applications which include using these nanoparticles as drug delivery vehicles. Such nanocarriers are relatively smaller than 100 nm in size with the ability to convey therapeutic drugs to a number of disease sites. Platinum-based nanoparticles have been extensively used in a number of applications namely catalysts, gas sensors, glucose sensors and cancer therapy. The properties of platinum nanoparticles (PtNP’s) typically depend on characteristics such as shape, particle size, elemental composition and structure, all of which can be manipulated and controlled in the fabrication process. Their unique size in the nanometer scale makes platinum nanoparticles an ideal candidate as targeted drug delivery vehicles. To target an anticancer drug to a diseased site is a distinctive feature of most studies, which aim to transfer an adequate dosage of the drug to cancer cells. Transport systems used as carriers of anticancer drugs offer numerous advantages, which include improved efficacy and a decrease in toxicity towards healthy cells when compared to standard drugs. The aim of this study was to determine the effect of platinum nanoparticles, gemcitabine and gemcitabine conjugated platinum nanoparticles (Hybrids) against cancer cells and healthy cells and to determine the mode of cell death and cell death pathways using flow cytometry. Platinum nanoparticles were synthesized via the reduction of hexachloroplatinic acid using sodium borohydride in the presence of capping agents. Synthesized platinum nanoparticles and the hybrids were characterized by observing peaks at 301 nm and 379 nm respectively using UV-visible spectroscopy. TEM images revealed that the PtNP’s and the conjugate compounds were spherical in shape with core sizes of 1.14 nm - 1.65 nm and 1.53 - 2.66 nm respectively. The bioactivity platinum nanoparticles, gemcitabine and the hybrids were investigated using MCF7 and Melanoma cancer cells at different concentrations from 0.10 to 100 µg/ml. Results indicated that conjugated nanoparticles induced the highest cell inhibition against both cell lines compared to gemcitabine and platinum nanoparticles. Bioactivity against PBMC (peripheral blood mononuclear) cells indicated that all three compounds show little or no effect towards the healthy cell line compared to the control. Melanoma cell line was used to determine the mode of cell death. Apoptosis was detected using Annexin V-FITC to detect membrane changes, JC-1 to detect a loss in mitochondrial membrane potential and caspase-3 assay kits. Results indicated that a significant amount of cell death was caused by cleavage of caspase-3. Nanoparticle drug delivery is an area that has shown significant promise in cancer treatment. Interaction of nanoparticles with human cells is an interesting topic for understanding toxicity and developing potential drug candidates. Imagine, something that is atleast or more than 80,000 times smaller than the edge of the ridge on a fingertip and unlocks a new wilderness into cancer research. Nanotechnology, known as the science of minute, is changing the approach to cancer and especially future diagnosis and treatment. Nanotechnology permits scientists to fabricate new apparatuses that are definitely smaller than cells, giving them the chance to attack tumor diseased cells. This innovation not just empowers practitioners to recognize malignancies prior but additionally holds the guarantee of halting cancer growth before it further develops. This progressive approach is so exact, specialists will in future be able to outline a unique treatment for an individual’s own restorative and hereditary profile. Researchers are designing nanoparticles that detect and destroy diseased cells and this optimistic innovation could be personalized for targeted drug delivery, enhanced imaging and ongoing affirmation of cancer cell death. The National Cancer Institute remains hopeful that facilitated development, nanotechnology will drastically change cancer treatment.Item Antimicrobial activity of ciprofloxacin-coated gold nanoparticles on selected pathogens(2014-08-08) Moodley, Nivrithi; Odhav, BhartiAntibiotic resistance amongst bacterial pathogens is a crisis that has been worsening over recent decades, resulting in serious and often fatal infections that cannot be treated by conventional means. Diseases caused by these drug resistant agents result in protracted illnesses, greater mortality rates and increases in treatment costs. Improvements to existing therapies and the development of novel treatments are urgently required to deal with this escalating threat to human health. One of the more promising strategies to combat antibiotic resistance is the use of metallic nanoparticles. Research into this area has shown that the binding of antibiotics to nanoparticles enhances their antimicrobial effects, reduces side-effects due to requirement of lower dosages of the drug, concentrates the drug at the interaction site with bacterial cells and in certain cases, has re-introduced susceptibility into bacterial strains that have developed drug resistance. Furthermore, these nanoparticles can be used in cancer treatment in similar drug delivery roles. Based on the promising data that demonstrated the synergistic effects of antimicrobial agents with nanoparticles, the aim of our research is to determine the effect of ciprofloxacin-conjugated gold nanoparticles as antimicrobial agents. To achieve this aim our objectives were: (i) to synthesize citrate-capped and ciprofloxacin-conjugated gold nanoparticles; (ii) to determine the physical and chemical characteristics of the ciprofloxacin-nanoparticle hybrid molecule; (iii) to investigate the antimicrobial activity of the conjugated nanoparticles against various species of common pathogens and (iv) to investigate the anti-cancer potential of the citrate-capped nanoparticles against a Caco-2 cell line. In this study, citrate-capped gold nanoparticles were conjugated to the antibiotic, ciprofloxacin, and their antibacterial and anti-cancer activity was evaluated. Initial experiments involved the synthesis and characterization of gold nanoparticles and ciprofloxacin conjugated nanoparticles. The gold nanoparticles were synthesized using the Turkevich citrate reduction technique which has been extensively used in studies thus far. The synthesized nanoparticles were characterized for specific absorbance using a UV-Spectrophotometer. The bond between the nanoparticles and ciprofloxacin was characterized by FTIR. Ultra structural details of the gold nanoparticles were established by TEM. The colloidal stability of the nanoparticles was determined by spectroscopic analysis. The antibacterial activity of the ciprofloxacin-conjugated gold nanoparticles was studied by exposure to pathogenic bacteria (Staphyloccocus aureus, E. coli, Klebsiella pneumoniae, Enterocococcus spp., Enterobacter spp., and Psuedomonas spp.). MIC values were measured to give indication of antimicrobial effect. These bactericidal properties of the conjugate nanoparticles were further investigated by electron microscopy. To evaluate the action of the citrate capped gold nanoparticles on cancer cells, we exposed Caco-2 cells to various concentrations of the nanoparticles and its effect was evaluated by measuring the viability of the cells. The results showed that 0.5 mM trisodium citrate reduced gold chloride to yield gold nanoparticles, which were spherical and 15 to 30 nm (by TEM characterization) and had an absorption maxima of 530 nm. The ciprofloxacin conjugated nanoparticles had an absorption maxima of 667nm. The colloidal stability, which is used to assess whether the synthesized particles will retain their integrity in solution showed that citrate-capped GNPs were most stable at 37°C over a 14 day storage period while ciprofloxacin-conjugated GNPs were found to be most stable at 4°C over a 14 day period. The FTIR results showed that chemical bonding in the conjugated nanoparticles occurs between the pyridone moiety of ciprofloxacin and the nanoparticle surface. The antimicrobial results of ciprofloxacin-conjugated GNPs had a significantly improved killing response compared to ciprofloxacin on both Gram positive and Gram negative bacteria. The citrate-capped GNPs are shown to exert a similar cytotoxic effect to gemcitabine on the Caco-2 cell line at a concentration of 0.5 mM. These results indicate that combining gold nanoparticles and ciprofloxacin enhances the antimicrobial effect of the antibiotic. The conjugate nanoparticles increase the concentration of antibiotics at the site of bacterium-antibiotic interaction, and thus enhance the binding and entry of antibiotics into bacteria. This has great implications for treatment of infection, as these antibiotic-conjugated nanoparticles can be incorporated into wound dressings, be administered intravenously as drug delivery agents, be engineered to possess multiple functionalities in addition to antibacterial activity and act as dual infection tracking and antimicrobial agents. Likewise, in this study, gemcitabine, an anticancer drug and gold nanoparticles were shown to kill cancer cells. In addition to their use in photothermal therapy and as drug delivery agents, the nanoparticles themselves possess anti-cancer activity against the Caco-2 cells. Thus, they have potential to act alone as a form of cancer treatment if functionalized with certain targeting agents that are specific to cancer cells, reducing the side-effects that come with regular chemotherapeutic drugs. It can be concluded that ciprofloxacin-conjugated gold nanoparticles enhance antibacterial effects of the antibiotic ciprofloxacin against bacterial cells and citrate-capped gold nanoparticles have anti-cancer activity against the Caco-2 cell line.Item Biosynthesis and antibacterial activity of silver and gold nanoparticles from the leaf and callus extracts of Amaranthus dubius, Gunnera perpensa, Ceratotheca triloba and Catharanthus roseus(2013-09-17) Patel, Naazlene; Odhav, BhartiThe biosynthesis of NPs has many advantages over the tedious, expensive and toxic physical and chemical methods of synthesis. Plants are stocked with valuable metabolites that are capable of reducing metal salts to form NPs. In this study, aqueous leaf extracts of A. dubius, G. perpensa, C. roseus and C. triloba were reacted with AgNO3 and HAuCl4 to determine the plants reducing abilities and hence synthesis of Ag and Au NPs capabilities. The synthesis reactions were carried out at different temperatures and extract concentrations for optimization. The goal was to form NPs within the specific wavelength range. Polar solvents: methanol and ethyl acetate extractions were carried out at the optimized conditions to evaluate the best solvent for the extraction of phytochemicals from the plants. The plant leaf extracts that were successful (A. dubius, G. perpensa and C. triloba) in synthesizing NPs were then micropropagated to form callus cultures. The reducing abilities of these callus cultures extracts were determined by varying temperature and concentration parameters. Characterization of the NPs formed by the different extracts was performed using UV-vis, TEM and FTIR. UV-vis spectrophotometry was used as a confirmatory as well as characterizing tool. TEM analysis was able to provide a description on the size and shape of the NPs whereas FTIR provided information on the biomolecules responsible for synthesis and capping of NPs. The stability of the NPs was determined by UV-vis scans over a period of 30 days which allowed observation of the alteration in peak shape and absorbance and hence condition of particles. Phytochemical tests were performed on the leaf extracts of the four plants to elucidate possible phytochemicals responsible for the reduction of metal salts. Antibacterial activity of the NPs was evaluated by using the disk diffusion assay and MICs were determined by the broth dilution method against pathogenic bacteria. A. dubius, G. perpensa and C. triloba were capable of synthesizing Ag NPs and Au NPs which were indicated by yellowish orange and reddish purple colour changes respectively. G. perpensa was able to spontaneously form Ag and Au NPs without any addition of heat whereas A. dubius and C. triloba required heat to form Au NPs. As the temperature of the reactions increased, the absorbance and possibly the number of NPs produced, increased. When the concentration of the extract was doubled, the absorbance was seen to decrease. C. roseus did not produce any Ag or Au NPs with any of the leaf extracts. Only A. dubius and C. triloba callus extracts were investigated for NP synthesis and it was found that A. dubius callus extracts were unsuccessful in synthesizing NPs and C. triloba callus extracts were able to form unstable Ag and Au NPs. The spherical Ag NPs that were formed from aqueous extracts of A. dubius were slightly larger than the methanolic Ag NPs. The Ag NPs produced by G. perpensa were in the same size range for aqueous and methanolic extracts. C. triloba Ag NPs formed from the methanolic extract were closer in size to A. dubius aqueous Ag NPs but the C. triloba aqueous extract produced much larger Ag NPs than the other extracts. The Ag NPs produced from A. dubius aqueous and methanolic extracts as well as C. triloba methanolic extracts exhibited the longest stability of 30 days. Ag NPs from G. perpensa aqueous extracts had the least stability. G. perpensa did not form any hexagonal Au NPs and the spherical and triangular Au NPs were smaller unlike in A. dubius and C. triloba Au NPs. The Au NPs formed by the aqueous extracts of A. dubius and C. triloba were larger in comparison to their methanolic counterparts. The Au NPs produced from G. perpensa aqueous and methanolic extracts as well as A. dubius and C. triloba methanolic extracts exhibited the longest stability of 30 days. Au NPs were stable for longer in comparison to Ag NPs. FTIR provided evidence that Ag and Au NPs have a chemical bond with the amide group in amino acids. However the intensities of biomolecules for Au NPs are more pronounced compared to the Ag NPs. It was also found that the Ag NPs synthesized by methanolic leaf extracts have slightly higher intensities than Ag NPs synthesized from aqueous leaf extracts. Phytochemical screening showed the absence of tannins in the C. roseus leaf, A. dubius and C. triloba callus extracts and presence in the other three plants. C. triloba methanolic extract Ag NPs showed the highest activity against Gram-positive S. aureus. Aqueous and methanolic Ag NPs from G. perpensa and C. triloba as well as A. dubius methanolic Ag NPs had activity against all fourteen bacteria. A. dubius aqueous Ag NPs had no activity against Enterobacter spp. and a strain of Klebsiella pneumoniae. G. perpensa Ag NPs had better antibacterial activity and lower MICs against Gram-positive and Gram-negative pathogenic bacteria compared to A. dubius and C. triloba. There was no antibacterial activity seen with Au NPs. The size and shape of NPs are the keys to their biomedical properties. Green synthesis of NPs is a feasible way for the future. This study showed that NPs can be synthesized very easily and economically. A key finding of this study is that different plants produce varying sizes and aggregation of NPs.Item Safety of nanofood : a review(Academic Journals, 2012-10-30) Ijabadeniyi, Oluwatosin AdemolaIntroduction of genetically modified (GM) foods generated a lot of controversy few years back, now it is the turn of nanofoods. There has been debate on the safety of foods that have been produced directly or indirectly with nanomaterials. Nanoparticles or nanotechnology procedures may be used to make food products, food additives, seeds and food packaging materials to give rise to a new and novel nanofood. While a lot have been written about the benefits of nanotechnology and nanomaterials in the food system, there is little research into the toxicological and possible hazard of nanofood. In this paper, the concept of nanotechnology, its diverse applications in the food industry and recent safety issues are considered. The paper concluded that it is necessary to do a thorough risk assessment of nanofoods before they are released to the market.