Browsing by Author "Pool, Edmund J."
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Item Assessment of raw and treated sewage using in vitro assays(University of the Western Cape, 2014) Booysen, Robin Alvin; Pool, Edmund J.Water scarcity is becoming an increasingly relevant problem for urban centres, especially in Southern Africa. However, water availability is not the only concern for consumers, because water quality is just as relevant. Many studies have revealed adverse health effects in organisms exposed to polluted waters, and the main source of that water pollution was traced back to sewage treatment works (STWs). Physiological systems that are affected include the endocrine system (as well as the reproductive system) and the immune system. Recently, the Stellenbosch STW started upgrading its facility, but this procedure would also affect the STW‘s operations. Stellenbosch STW uses an activated sludge treatment, but also employs trickling filters (biofilters). After screening and grit removal, wastewater enters trickling filters, and then undergoes activated sludge treatment (aerobic basin). After activated sludge treatment (and settling) some water is chlorinated before entering a maturation pond. The other water goes directly to a larger maturation pond (for a longer period), instead. The final effluent then gets discharged into the Veldwagters River. Since STW operations is an important factor in STW effluent quality, this study aimed to investigate the water quality (at Stellenbosch STW) during the upgrade. Specifically, the bacterial quality, the steroidal quality (testosterone, progesterone, estrone: E1, 17 β- estradiol: E2 and 17 α-ethinyl estradiol: EE2) and the potential immunotoxic quality of waters were assessed. Water samples were collected after the grit removal (influent), after the trickling filters (biofilter effluent), while it was leaving the aerobic basin activated sludge effluent) and as it was leaving the maturation ponds (final effluent). To determine bacterial quality a semi-quantitative ReadyCult® assay was performed on raw water samples (detects total coliforms and Escherichia coli). Bacterial levels were high for all influent samples, water from the biofilter, water from the aerobic digester (activated sludge) and the final effluent (most days). The first collection date, however, showed less than 1cfu/mL of both E. coli and total coliforms for the final effluent. Raw water also underwent solid phase extraction, before the steroid concentrations were determined by enzyme-linked immunosorbent assays (ELISAs). Steroid levels were very high in the influent. Each treatment progressively reduced the steroid concentration. However, progesterone concentration increased during the biofilter treatment. The increase in progesterone was probably due to bacterial de-conjugation of hydrophilic-progesterone-conjugates. Nonetheless effluent steroid levels were significantly lower than the influent. Steroid reduction through the Stellenbosch STW was 96%, 95%, 55%, 78% and 87% for testosterone, progesterone, estrone, estradiol and ethinyl estradiol respectively. Much variability in steroid concentrations was noted between sampling dates. The activated sludge treatment was the best at reducing steroid concentration. Nonetheless, the STW still discharged steroids into the environment. Finally, the humoral immune effects of Stellenbosch STW influent and effluent was determined by using hybridoma cells and assessing affects on antibody production. Antibody levels were then detected by ELISA. No adverse effects to antibody synthesis/secretion were noted as a result of exposure to either influent or effluent.Item Comparison between chemical and tissue culture methods to monitor environmental estrogens(University of the Western Cape, 2012) Baguma, Richard; Pool, Edmund J.Endocrine disrupting compounds (EDCs) are exogenous compounds/chemicals in the environment that interfere with the synthesis, secretion, distribution and function or elimination of natural hormones in the body. Environmental estrogens are a subclass of EDCs that may mimic or inhibit the effect of endogenous estrogen and can therefore influence developmental and reproductive health in humans and animals. EDCs have been reported to adversely affect the reproductive, immune, endocrine and nervous systems of wildlife and humans. The effects of EDCs include gonadal abnormalities, altered male/female sex ratios, reduced fertility and cancers of the male and female reproductive tract to mention a few. These effects are difficult to detect. Although it is essential to screen for EDCs in aqueous environmental samples, most countries have failed to implement this as part of their routine water quality monitoring programs due to various constraints such as the high cost of assays and the lack of infrastructure and skills required to do the assays. Therefore, there is a clear need for more user-friendly, more economically viable and time saving assays that can be used for routine monitoring of environmental EDCs. The aim of this study was to investigate the comparison between chemical and tissue culture methods to monitor environmental estrogens. 28 environmental water samples were collected from various sites around South Africa and analyzed for EDCs using a battery of rapid in vitro tests. Samples collected for the current study were selected based on various human impacts and also to give approximately 50% high and 50% low estrogen values. The 28 environmental water samples were separated into two groups based on the estradiol ELISA. The estradiol ELISA was chosen because estradiol is the principal estrogen found in all mammalian species during their reproductive years. For this separation, an estradiol level of 5 pg/ml was used as cut-off. Of the 28 samples investigated, 15 had estradiol levels higher than 5 pg/ml and were designated as high estradiol. The remaining 13 samples contained estradiol at 5 pg/ml or less and they were designated as low estradiol. The first objective of this study was to compare different rapid ELISAs for EDC monitoring to determine if the data obtained with these assays are similar/identical. The data obtained from the estrogenic ELISAs was related/similar and showed good correlation with each other. This is because the different estrogens are very similar and also due to the fact that the same sub-group in the population (the reproductively active females) is secreting these hormones. Therefore, an estradiol rapid assay was proposed as a first screening system for estrogens in samples. Even though there was a positive correlation between the estradiol rapid assay and testosterone rapid assay, separation of samples based on estradiol levels wasn’t a good predictor of testosterone levels in the samples. A testosterone rapid assay was therefore recommended as necessary to screen for androgens in samples. The positive correlation between the estradiol rapid assay and progesterone rapid assay was expected because both estradiol and progesterone are secreted and excreted by the same population sub-group (reproductively active females). This study also demonstrated a good predictability of separating samples containing progesterone using the estradiol ELISA. Progesterone is secreted by pregnant women, a sub-group of the reproductively active females. It is advised that a progesterone rapid assay be included to screen samples for progestogens. The second objective of this study was to compare estradiol rapid ELISAs with a bioassay for anti-androgenicity using mouse testicular cell cultures. The mouse testicular cell testosterone synthesis bioassay to monitor anti-androgenicity of the samples showed no correlation between the ELISA data for estrogens. This study shows that anti-androgenic effects need to be monitored independently because the data for estrogenic compounds cannot be used as a predictor for anti-androgenic effects. This demonstrated the need for the inclusion of a mouse testicular cell testosterone synthesis bioassay to screen for androgenicity and anti-androgenicity of water samples. In summary, due to the different mechanisms of action of EDCs, this study recommended a battery of assays to monitor for EDCs. The battery of assays suggested is: ●Estradiol ELISA as a rapid assay to screen for estrogens. ●Testosterone ELISA as a rapid assay to screen for androgens. ●Progesterone ELISA as a rapid assay to screen for progestogens. ●Mouse testicular cell testosterone synthesis bioassay to screen for androgenicity and anti-androgenicity.Item The effects of endocrine disrupting chemicals on biomarkers of inflammation produced by lipopolysaccharide stimulated raw264.7 macrophages(MDPI, 2019) Makene, Vedastus W.; Pool, Edmund J.Endocrine disrupting chemicals (EDCs) are common pollutants in the environment and can induce disruption of the endocrine and immune systems. The present study evaluated the effects of selected common environmental EDCs on secretion of inflammatory biomarkers by RAW264.7 cells. The EDCs investigated were Estradiol (E2), 5α-dihydrotestosterone (DHT), and Bisphenol A (BPA). To evaluate if the effects caused by EDCs were modulated by steroid hormone receptors, antagonists of estrogen and androgen receptors were used. The steroid receptor antagonists used were Tamoxifen, an estrogen receptor antagonist, and Flutamide, an androgen receptor antagonist. Secretion of biomarkers of inflammation, namely nitric oxide (NO) and interleukin 6 (IL-6), were monitored. The NO was determined using Griess reaction and IL-6 was measured by enzyme linked immunosorbent assay (ELISA). Although 5 µg/mL E2, DHT, and BPA were not toxic to RAW264.7 cell cultures, the same treatments significantly (p < 0.001) reduced both NO and IL-6 secretion by lipopolysaccharide (LPS)-stimulated RAW264.7 cell cultures.Item Effects of green, black and rooibos tea, coffee and buchu on testosterone production by mouse testicular cultures(University of the Western Cape, 2013) Abuaniza, Zaroug A.M.; Pool, Edmund J.Modulation of the male reproductive system occurs as a result of exposure to endocrine disrupting compounds (EDCs) in different life stages. The effects of EDCs on the male reproductive system include infertility, decreased sperm count, function and morphology, abnormal development of secondary sex characteristics, reproductive function and sexual behavior, as well as decreased libido. Phytochemicals are naturally occurring, biologically active chemical compounds in plants. They are divided into different groups. Isoflavonoids and lignans, are the two major groups of phytoestrogens. Phytoestrogens of teas, coffee and buchu have many beneficial effects on body systems such as antimutagenic, antidiabetic, anti-inflammatory, antibacterial and antiviral properties. They also elicit many adverse events, for example, heavy consumption of green and black tea may cause liver damage and added unwanted effects when combined with other herbal beverages. Chronic heavy consumption of coffee is positively correlated to acute myocardial infarction and can elevate serum cholesterol levels. Rooibos tea decreases steroidogenesis by steroid secreting cell lines.This study investigated the effects of these beverages on the male reproductive system, using a minced testes method for determination of cell viability and hormone (testosterone) production. The first objective of this study was to optimize protein supplement for in vitro testosterone production using human serum albumin (HSA) and foetal bovine serum (FBS). Testicular cultures were prepared and exposed overnight to different concentrations of both sera and then incubated for 4 hours with or without luteinizing hormone (LH). The results showed that addition of protein supplements (HSA or FBS) did not have a significant effect on testosterone production. The second objective of this study was to investigate the effects of green tea, black tea, rooibos tea, coffee and buchu on cell viability of testicular cultures. Cells were treated overnight with varying concentrations of the plant extracts followed by incubation with/without LH for 4 hours. The effects of the plant beverages on cellular protein production were determined by the Bradford assay. The results showed that treatment of cells with varying concentrations of the plant extracts (with/without LH-treatment) had no significant effect on total cellular protein. The third objective of this study was to investigate the effects of black, green and rooibos teas, coffee and buchu on testosterone production by testicular cultures. The results obtained from these experiments showed that rooibos tea and buchu did not affect testosterone production in the presence or absence of LH. The results also indicated that green tea, black tea and coffee inhibited testosterone production by mouse testis cultures in the presence of LH, but not in the absence of LH. Black tea was the most potent inhibitor of testosterone synthesis by mouse testis cultures (IC50= 48 μg/ml), followed by coffee (IC50= 64 μg/ml) and green tea (IC50= 173 μg/ml). Green tea, black tea and coffee inhibited LH-stimulated testosterone synthesis, suggesting that these beverages may impair testicular steroidogenesis in mice. Thus, in spite of their acclaimed beneficial effects, consumption of these beverages in high doses raises concerns for their inhibitory effects on male reproductive function. Further in vitro and in vivo studies are warranted to determine their exact mechanisms of action on the male reproductive system in general and testicular function in particular.Item The effects of nanomaterials, in the presence and absence of serum proteins, on testicular cell metabolic processes and steroidogenesis(University of the Western Cape, 2014) Muller, Ashley George; Pool, Edmund J.The aim of this study is to be the first to ascertain the effects of silver nanoparticles on testosterone production. The Ag NPs used for this study have the following characteristics; purity ≥ 99.5%; 66.7 % of particles have a diameter between 20-40 nm in aqueous solution. Three month old male Balb/C mice were sacrificed and testicular cell cultures were prepared. The cells were subsequently treated with various concentrations of Ag NPs (with or without luteinizing hormone (LH)-treatment) and incubated for 4 hours. Testosterone secretion in the culture supernantant was then determined using a testosterone ELISA kit. Ag NPs (at 20 μg/ml) significantly (p < 0.001) decreased LH-stimulated testosterone production as compared to the control. This study showed that Ag NPs adversely affect testosterone synthesis in vitro and can therefore pose a risk for male reproduction.Item The effects of silver nanoparticles on RAW 264.7. Macrophages and human whole blood cell cultures(University of the Western Cape, 2019) Lategan, Kim L.; Walters, Chavon R.; Pool, Edmund J.Silver nanoparticles (AgNPs) are commonly found in consumer products due to their antimicrobial properties. This study evaluated the effects of AgNPs on the murine macrophage cell line RAW 264.7 and human whole blood cell cultures (WBCs). Effects of AgNPs on RAW cells were assessed in the presence or absence of lipopolysaccharide (LPS). Effects of AgNPs on WBCs were monitored under basal conditions and in the presence of either LPS or phytohaemmagglutinin (PHA). AgNPs were cytotoxic to WBCs at 250 μg/ml. Under basal conditions, RAW cells = 62.5. μg/ml and WBCs > 25 μg/ml AgNPs induced biomarkers associated with inflammation. Under LPS stimulated conditions, 250 μg/ml AgNP inhibited biomarkers associated with inflammation for both cultures. Under basal conditions, and in the presence of 250 μg/ml AgNP, WBCs produced acquired immune system cytokines IL-10 and IFNγ. IL-10 synthesis by WBCs was partially inhibited by 250 μg/ml AgNP in the presence of PHA. Proteome profiles of RAW cell supernatants show that AgNPs modulate biomarkers associated with inflammation. WBCs proteome analysis shows modulation of biomarkers associated with anti-inflammatory effects.Item The effects of silver nanoparticles on the expression of protein biomarkers of cell stress, apoptosis and inflammation by the human liver cancer cell line, HepG2(University of Western Cape, 2021) Volkmann, Tina; Pool, Edmund J.Nanoscience is the study of phenomena and objects at the nanoscale (around 1-100 nm), socalled nanomaterials. These nanomaterials exhibit novel properties that are often very different to those of the bulk materials used for their synthesis. Hence, nanoparticles are widely commercialised, especially silver nanoparticles (AgNPs) due to their antimicrobial properties and some other useful phenomena. This commercialisation leads to inevitable exposure to the environment and humans, which leads to inhalation, ingestion or dermal uptake of AgNPs by the human body culminating in distribution to several major organs, including the liver. Both chronic and acute exposure to AgNPs have been linked to detrimental effects in both in vitro and in vivo studies. These include oxidative stress, induction of inflammation, DNA damage, cell death and many others.Item The efficiency of drinking water treatment plants in removing immunotoxins(University of the Western Cape, 2010) Malan, Cheryl; Pool, Edmund J.; DuPreez, H.; Dept. of Medical BioSciences; Faculty of ScienceThe aim of this study was to evaluate the effectiveness of water treatment processes of two drinking water plants to remove immunotoxins and steroid hormones. Raw and treated drinking water was screened for effects on inflammatory activity using the biomarker IL-6, humoral immunity using the biomarker IL-10 and cell mediated immunity using the biomarker FN-γ. In vitro human whole blood culture assays were used in order to elucidate potential immunotoxicity.Item The immune-modulating activity of Artemisia afra(University of the Western Cape, 2010) Kriel, Yusra; Pool, Edmund J.; Faculty of ScienceThis study shows that herbs can be effectively screened for potiential bio-activity using in vitro methods. Further studies will be needed to better explore Artemisia afra’s effect on immunoregulation, particularly long term effects of the herb on the immune system and its effect on other disease states.Item The immune-modulating activity of Artemisia afra(University of the Western Cape, 2010) Kriel, Yusra; Pool, Edmund J.; Faculty of ScienceThis study shows that herbs can be effectively screened for potiential bio-activity using in vitro methods. Further studies will be needed to better explore Artemisia afra’s effect on immunoregulation, particularly long term effects of the herb on the immune system and its effect on other disease states.Item The immune-modulating activity of Sutherlandia frutescens(University of the Western Cape, 2010) Kisten, Najwa; Pool, Edmund J.; NULL; Faculty of ScienceThe aim of this study was to investigate the effects of Sutherlandia frutescens on the inflammatory response and T cell differentiation in vitro using cytokines as biomarkers. Whole blood cells containing various concentrations of Sutherlandia frutescens were stimulated in vitro with either Lipopolysaccharide (LPS) or Phytohaemagglutinin (PHA). Results show that Sutherlandia frutescens is not toxic at any of the concentrations tested. The addition of Sutherlandia frutescens at high concentrations to the stimulated whole blood cell cultures reflects a significant down regulation of Interleukin(IL) 6 and IL-10 compared to the control (P<0.05) hence suppressed the inflammatory and humoral immune response. Results obtained for Inteferon-gamma (IFN ) shows that Sutherlandia frutescens is donor specific as it reflects both up and down regulation in the release of IFN at the concentrations tested. The in vitro data generated by this study supports the use of Sutherlandia frutescens in the management of inflammatory conditions and allergies such as asthma. However the effects of Sutherlandia frutescens on cell mediated immunity was found to be donor specific. Further investigation of Sutherlandia frutescens on cellular immunity is advised.Item The immune-modulating activity of Sutherlandia frutescens(University of the Western Cape, 2010) Kisten, Najwa; Pool, Edmund J.; NULL; Faculty of ScienceThe aim of this study was to investigate the effects of Sutherlandia frutescens on the inflammatory response and T cell differentiation in vitro using cytokines as biomarkers. Whole blood cells containing various concentrations of Sutherlandia frutescens were stimulated in vitro with either Lipopolysaccharide (LPS) or Phytohaemagglutinin (PHA). Results show that Sutherlandia frutescens is not toxic at any of the concentrations tested. The addition of Sutherlandia frutescens at high concentrations to the stimulated whole blood cell cultures reflects a significant down regulation of Interleukin(IL) 6 and IL-10 compared to the control (P<0.05) hence suppressed the inflammatory and humoral immune response. Results obtained for Inteferon-gamma (IFN ) shows that Sutherlandia frutescens is donor specific as it reflects both up and down regulation in the release of IFN at the concentrations tested. The in vitro data generated by this study supports the use of Sutherlandia frutescens in the management of inflammatory conditions and allergies such as asthma. However the effects of Sutherlandia frutescens on cell mediated immunity was found to be donor specific. Further investigation of Sutherlandia frutescens on cellular immunity is advised.Item An in vitro study on the immunotoxicity of sewage effluents discharged into the Eerste River-Kuils river water catchment system(2008) Magcwebeba, Tandeka; Pool, Edmund J."The aim of the study was to use in vitro human whole blood cultures to screen the water samples collected from the Eerste/Plankenbrug river system for cytotoxicity and inflammatory activity and for the first time investigate the impact on the cell- mediated and humoral immune pathways. Water samples were collected fronm the sites during the dry summer season and rainy winter season. Blood was collected from the healthy male volunteers and diluted with RPMI 1640. For cytotoxicity and inflammatory activity 2.5ul of blood for 18-20 hrs at 37 C... This study shows that waster from the Plankenbrug River is heavily polluted by contaminants from both the agricultural area and informal settlement of Kayamandi. These contaminants can be potentially immunotoxic during the summer season and they can result in inflammatory diarrheal disease and immunosuppression in exposed individuals..."Item An in vitro study on the immunotoxicity of South African beer(University of the Western Cape, 2008) Neethling, Michelle; Pool, Edmund J.; Faculty of ScienceTraditionally brewed beers are of cultural and economic importance to many African nations. The presence of mycotoxins in African beer is a topic that needs to be addressed, since most African countries have a climate of high humidity and temperature that favours the growth of moulds. Mycotoxins challenge not only the health of animals and humans, but also the economy, especially in underdeveloped countries where contamination is most likely. Literature proves that mycotoxins depict various effects on the immune system including immunotoxicity. Beer analysis is therefore of utmost importance in order to evaluate organoleptic characteristics, quality, nutritional value as well as safety. The aims of this study involve the analysis and comparison of traditional and commercial beer in terms of physical characteristics, mycotoxin concentrations as well as effects on specific immune pathway biomarkers in order to elucidate possible immunotoxicity.Item Potamonautes spp. As a bioindicator for oestrogenic endocrine disrupting chemicals(University of the Western Cape, 2017) Schoeman, Dewald; Pool, Edmund J.Environmental pollutants, such as endocrine disrupting chemicals (EDCs), are a health concern as they can adversely affect animal health by interfering with the normal function of hormones. Oestrogenic EDCs can cause adverse developmental and reproductive effects by mimicking or inhibiting endogenous oestrogens. However, these effects are difficult to detect as they often only manifest long after the initial exposure. Vitellogenin (VTG) is the precursor to the major yolk protein vitellin (Vn) and is produced by egg laying females in response to oestrogens. The VTG gene is also present in males, but silent. Thus, the presence of VTG and Vn in animals, as well as the synthesis thereof in response to oestrogens, can serve a dual purpose in biomonitoring experiments. These proteins can be monitored over a period of time to establish the reproductive cycle of an organism and can also serve as a biomarker for oestrogenic pollutants.Item The use of in vitro assays to screen for endocrine modulation(University of the Western Cape, 2008) Hendricks, Rahzia; Pool, Edmund J.; Faculty of ScienceAspalathus linearis (A. linearis), commonly known as Rooibos tea or Red bush tea and Camellia sinensis (C. sinensis) or Black tea are beverages that are consumed throughout the world. These teas possess antioxidant, immunomodulating and anti-cancer actions. The aim of this study was to use in vitro assays to screen Rooibos and Black tea for endocrine modulation. The immune modulating effects of Rooibos and Black tea were investigated using an in vitro whole blood culture (WBC) assay. Unstimulated WBCs treated with Rooibos tea secreted higher levels of IL-6, IL-10 and IFNγ than cultures treated with DMSO control. Rooibos treatment of stimulated WBCs resulted in higher IL-6, lower IL-10 and no effect on IFNγ secretion compared to DMSO treated stimulated WBC. Black tea treatment of stimulated WBC resulted in decreased IL-6, IL-10 and IFNγ secretion compared to the DMSO treated stimulated WBC. Extracts of Rooibos and Black tea were assessed for phytoestrogens using quantitative estrogen ELISAs. Both teas contain phytoestrogens. The quantitative ELISAs showed that Rooibos tea contained significantly lower estrone (E1), estradiol (E2) and estriol (E3) levels than Black tea. The effects of Rooibos and Black tea on proliferation of the estrogen dependant MCF-7 cell line was determined to further characterise the phytoestrogenic properties of the teas. Both Rooibos and Black tea extracts caused a significant inhibition of MCF-7 proliferation. This study shows that Rooibos tea and Black tea are beverages that can either stimulate or suppress the immune system. Also, both teas contain significant levels of phytoestrogens as determined by quantitative ELISAs. The current study confirms previous reports showing inhibition of growth in breast cancer cell lines by phytoestrogens. The findings extend related observations on the anti-carcinogenic potential of the two teas.Item The use of whole blood cell cultures as a model for assessing the effects of Septilin on the immune system(University of the Western Cape, 2017) Hoosen, Mujeeb; Pool, Edmund J.In the past three decades there has been a huge increase in the use of herbal medicine globally. The active principles of these herbal medicines are mostly unknown with supportive evidence for safety and efficacy very rare. Septilin is a phytopharmaceutical formulation which is recommended for the treatment and management of various infections. It has been claimed to have immunomodulatory actions that potentiates the body's immune response. The immunomodulatory activity of Septilin has not been well investigated via appropriate in vitro models. Therefore this study was undertaken to investigate the in vitro effects of Septilin on biomarkers of specific immune pathways by using WBC. Stimulated and unstimulated WBC were incubated with the product. Enzyme linked immunosorbent assays were used to screen for IL-6, IL-10, and IFN? as biomarkers for inflammation, humoral immunity, and cell mediated immunity, respectively. Results show that the presence of Septilin in LPS stimulated WBC has no effect on the release of IL-6 and IFN? production but stimulated IL-10 production. Septilin in unstimulated WBC has no effect on the release of IL-10 and IFN? production but stimulatory effects on IL-6 production. This study also assessed the effects of Artemisia afra, Aspalathus linearis (rooibos), and Septilin on inflammatory biomarkers namely, IL-6 and nitric oxide (NO) using RAW 264.7 cells, a murine macrophage cell line. The results of this study indicate that Artemisia afra has anti-inflammatory effects while Aspalathus linearis (rooibos) up regulated the immune system. The study also shows that Septilin has no immunomodulatory effects on RAW 264.7 cells.Item The toxicity of silver nanoparticles(University of the Western Cape, 2012) Motsoeneng, Khothatso Patricia; Pool, Edmund J.; Petrik, LeslieUnavailability and contamination of available water resources are major factors contributing to adverse health conditions worldwide. AgNPs present a potential strategy for water purification; however, their ability to accumulate in organs such as the kidneys, lungs and spleen is a possible source of toxicity. This study investigates the toxicity of AgNPs to Saccharomyces cerevisiae (S. cerevisiae). S. cerevisiae is an excellent model organism for assessing toxic compounds that affect eukaryotic organisms due to their ease of cultivation. AgNPs were prepared by photo-reduction of silver nitrate with OSRAM Vitalux lamp (300 W and 230 V) in the presence of stabilizing agents such as polyvinylpyrrolidone and citric acid, yielding AgNPs. The effects of varying the concentration of the stabilizing agent, time of exposure to the light source, and pH were investigated. The formation of AgNPs was analysed by ultra-violet spectroscopy (UV-Vis) and transmission electron microscope techniques. The results showed that the AgNPs absorbed ultra-violet radiation between 400 and 500 nm and TEM images showed the particles to be both spherical and needle-like in shape. The shapes of the AgNPs were largely dependent on the synthesis method applied. The toxicity of AgNPs was assessed using metabolic activity of yeast cells as biomarker andmonitored with of the chromogenic assay, XTT. S. cerevisiae was introduced into different concentrations of AgNPs and incubated at 37oC for 72 h. After the incubation, XTT assay was performed to assess the cell viability. The XTT results showed that high concentration of AgNPs (100 µg/mL) inhibited the growth of S. cerevisiae. The synthesis of AgNPs and theassessment of their toxicity on S. cerevisiae was thus undertaken and established in this work.