Inhibitory Effect Of Silver Nanoparticles Research Articles

Study of the inhibitory effect of Silver Nanoparticles on Extensively Drug-resistant Mycobacterium Tuberculosis (TB) strains

Study of the inhibitory effect of Silver Nanoparticles on Extensively Drug-resistant Mycobacterium Tuberculosis (TB) strains

Grewia tenax-Mediated Silver Nanoparticles as Efficient Antibacterial and Antifungal Agents

Nanoparticles have gained immense interest as probable drug molecules against microbial infections. Metal nanoparticles synthesized via exploring the reduction potential and capping activity of plants were found to have remarkable antimicrobial activity. The synthesis was conducted without hazardous chemicals and generation of toxic waste products. The focus of the study was, therefore, to investigate the efficacy of silver nanoparticles biosynthesized using Grewia tenax leaf extract as an antibacterial, antibiofilm, and antifungal therapeutic agent. The silver nanoparticles (GTAgNPs) were synthesized using optimized conditions of 2.5 mM AgNO3 and 1 : 10 ratio of 10% extract at 37°C on continuous stirring. The characterization was done by UV-visible spectroscopy, DLS, SEM, zeta potential, and FTIR. The antibacterial activity of GTAgNPs against both Gram (+) Bacillus cereus and Staphylococcus aureus and Gram (−) Escherichia coli and Pseudomonas aeruginosa bacteria via zone of inhibition, MIC, and MBC was analysed. The inhibitory effect of silver nanoparticles on biofilm formation was also observed against these bacteria. These nanoparticles were then evaluated for their potential antifungal activity against Candida albicans and Aspergillus niger by observing fungal growth inhibition. The probable mechanism of antimicrobial activity by GTAgNPs was studied by scanning electron microscopy which showed the significant formation of pores on the cell surface in GTAgNPs-treated microbial cells, leading to the death of the microbial cell. All these studies concluded that GTAgNPs possess the potent antimicrobial potential and can be employed as antimicrobial therapeutic agents.

Inhibitory effect of silver nanoparticles synthesized using the chamomile extract against Streptococcus mutans cariogenic pathogen.

With the recent use and development of nanomaterials, silver nanoparticles (AgNPs) are gaining much attention as a promising antibacterial agent for use in caries prevention. This study aimed to biosynthesize AgNPs using chamomile extract as a reducing agent and to investigate its inhibitory effect against Streptococcus mutans (S. mutans) dental bacteria. Chamomile extract was prepared by sonication and added dropwise to silver nitrate (1mM) solution to synthesize AgNPs. Its formation was confirmed spectrophotometrically, and its size was determined. The disc diffusion method was used to test the antibacterial activity of the biosynthesized AgNPs against S. mutans. Also, its minimum inhibitory concentration (MIC) was assessed. The spectrum of biosynthesized AgNPs showed a maximum peak at 454 nm, and the peak area increased with increasing time. The mean AgNP size was 41 nm. The inhibition zone diameter recorded for AgNPs against S. mutans was 10 mm, while the MIC was 280 μg/ml. AgNPs biosynthesized using chamomile extract were proven to exert good antibacterial activity against cariogenic S. mutans. Using chamomile extract as a reducing agent can provide a rapid, affordable, and eco-friendly approach for AgNP production, which could be incorporated into various dental vehicles for dental caries prevention.

Determination of the inhibitory activity of silver nanoparticles against some pathogenic multi-antibiotic resistant bacterial species

The study was done to determine the inhibitory effect of silver nanoparticles synthesed by the filamentous fungus Fusarium mangiferae against some multidrugs resistant pathogenic bacteria which were taken from the Central Laboratory of Sulaymaniyah Teaching Hospital.Silver nanoparticles showed their inhibitory effect on the various bacterial species in this study by two methods Wich are the well diffusion method and inhibition growth. Nanoparticles of silver showed inhibitory areas by Well diffusion method against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Proteus mirabilis.
 The Diameter of inhibition zones of the above mentioned bacteria were (15.25, 20.5, 17.75.16) mm while The method of inhibition of growth had shown that nanoparticles effective against the above bacterial species at concentrations (50, 50, 50, 100)% respectively through the lack of growth of the colonies on the surface of the nutrient agar. Therefore, the use of nanoparticles from some metals is the best solution for the treatment of infectious diseases due to the effective inhibiting properties of these nanoparticles against bacteria without negative side effects.

Green Synthesis of Silver Nanoparticles with Extract of Indian Ginseng and In Vitro Inhibitory Activity against Infectious Bursal Disease Virus

Infectious bursal disease virus (IBDV) is a serious poultry pathogen responsible for causing major economic losses to the poultry industry globally. The virus is closely related to several other important viral pathogens of fishes, crabs, and mollusks and evolutionarily related to important viral pathogens of humans. Previously, we demonstrated the inhibition of this virus by the extracts of roots of Withania somnifera Dunal, commonly known as Indian ginseng, both in vitro and in vivo. Furthermore, many studies reported the inhibition of diverse types of viruses by nanoparticles of silver. In the present study, we investigated the inhibitory effect of silver nanoparticles obtained by green synthesized with Indian ginseng extract against IBDV. Conditions for the synthesis of silver nanoparticles were optimized, and the nanoparticles thus obtained (WS AgNPs) were characterized physically. Thereafter, the maximum non-cytotoxic dose of these nanoparticles for treating chicken embryo fibroblasts (CEF) was determined. Treatment of IBDV-infected CEF with the WS AgNPs decreased the infective virus titer by >93%, intracellular viral load by >71%, and virus-induced cytopathy by >51%, demonstrating the strong inhibitory effect of the WS AgNPs against IBDV, and encouraging similar applications against related veterinary and human viruses.

Biomimetic Synthesis of Silver Nanoparticles Using New Aquatic Species of Bacillus, Alcaligenes, and Paenibacillus and their Potential Antibiofilm Activity against Biofilm-Forming Escherichia coli

The current study aimed to assess the beneficial inhibitory effect of silver nanoparticles on biofilm formation by E. coli ATCC11922; eighteen Egyptian bacterial isolates obtained from Al-Bahr El-Pherony, Menoufyia Governorate were screened for silver nanoparticles biosynthesis (AgNPs). Three of the best extracellular AgNPs producing isolates have been identified using biochemical and molecular techniques. Characterization of AgNPs was performed by UV-visible spectroscopy, Fourier transforms infrared (FTIR), and Transmission Electron Microscopy (TEM). Next, the antibiofilm restriction of AgNPs was evaluated using the micro broth dilution method. A total of eleven bacterial isolates were positive for the AgNPs biosynthesis. Amongst, three AgNPs with tribute effects have the greatest anti-biofilm activity and have been identified as new species belonging to the genera Bacillus, Alcaligenes, and Paenibacillus. Plasmon surface resonance of the formed AgNPs had feature peaks at ~420 nm. FTIR confirmed the character of the capping/reducing agents of Ag+. X-ray diffraction and TEM investigation confirmed the purity, spherical shape, and size of 3.01-16.47 nm. Besides, biosynthetic AgNPs reduced biofilm growth, biomass, and density by 80-90% on a dose basis. Therefore, biosynthetic AgNPs are green antibiofilm against pathogenic microbes. This fact promotes its use as a convincing disinfectant for soiling water and depleting pollution.

Investigation the effects of silver nanoparticles and gold nanoparticles on expression of bap and csu genes in biofilm formation of Acinetobacter baumannii.

Acinetobacter baumannii is one of the main pathogens of the hospital and causes various infections. csu A/BABCDE involved in the initial surface attachment during biofilm formation and bap gene produces specific proteins at the cell surface that play a direct role in formation of biofilm and the infectivity of this bacterium. The aim of this study was to investigate the effect of silver nanoparticles and gold nanoparticles on the expression of bap and csu genes in the Acinetobacter baumannii biofilm formation. The susceptibility test was performed to determine the MIC of silver nanoparticles, gold nanoparticles and gold-vancomycin nanoparticles performed by broth dilution method on A. baumannii strains. The ability of biofilms formation in strains treated by MIC of silver nanoparticles and gold-vancomycin nanoparticles were evaluated by microtiter plate method and A. baumannii ATCC19606 used as control. Expression of the csu and bap genes were determinded by measuring the cognate mRNA level by real-time PCR. In present study, gold nanoparticles could not prevent the growth and biofilm formation of A. baumannii strains. The MIC concentration of silver nanoparticles and vancomycin- gold nanoparticles were 6.25 μg/ml and 0.625 μg/ml respectively and MBC concenteration of nanoparticles for 70% of strain was 12.5 μg/ml and 1.25 μg/ml respectively. Real-time PCR and data analysis, determined that the expression of bap, csuC and csuE genes in A. baumannii strains treated with MIC concentration (6.25 μg/ml) of silver nanoparticles decreased compared to control groups. Also, the expression of csuC and csuE genes in strains treated with MIC concentration (0.625 μg/ml) of vancomycin -gold nanoparticles increased, however the expression of bap was decreased compared to the control groups. Due to the inhibitory effect of silver nanoparticles and gold-vancomycin nanoparticles against A. baumannii biofilm formation and genes expression, they can probably be used for prevent of biofilm formation in medical instrument or can be use for treatment of infections with or without antibiotic.

Benefits of Usage of Immobilized Silver Nanoparticles as Pseudomonas aeruginosa Antibiofilm Factors.

The aim of this study was to assess the beneficial inhibitory effect of silver nanoparticles immobilized on SiO2 or TiO2 on biofilm formation by Pseudomonas aeruginosa—one of the most dangerous pathogens isolated from urine and bronchoalveolar lavage fluid of patients hospitalized in intensive care units. Pure and silver doped nanoparticles of SiO2 and TiO2 were prepared using a novel modified sol-gel method. Ten clinical strains of P. aeruginosa and the reference PAO1 strain were used. The minimal inhibitory concentration (MIC) was determined by the broth microdilution method. The minimal biofilm inhibitory concentration (MBIC) and biofilm formation were assessed by colorimetric assay. Bacterial enumeration was used to assess the viability of bacteria in the biofilm. Silver nanoparticles immobilized on the SiO2 and TiO2 indicated high antibacterial efficacy against P. aeruginosa planktonic and biofilm cultures. TiO2/Ag0 showed a better bactericidal effect than SiO2/Ag0. Our results indicate that the inorganic compounds (SiO2, TiO2) after nanotechnological modification may be successfully used as antibacterial agents against multidrug-resistant P. aeruginosa strains.

Ecofriendly Synthesis of Silver Nanoparticles Using Ananas comosus Fruit Peels: Anticancer and Antimicrobial Activities.

Metallic nanoparticles are valuable materials and have a range of uses. Nanoparticles synthesized from plant wastes by environment-friendly methods have attracted the attention of researchers in recent years. Also, the advantages of biological resources and synthesis methods are attracting attention. In this study, silver nanoparticles were synthesized from Ananas comosus fruit peels using ecofriendly method steps. The characterization of the particles obtained was determined by using a UV-visible spectrophotometer (UV-Vis.), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction diffractometer (XRD), Fourier scanning electron microscope (FESEM), and transmission electron microscopy (TEM). The nanoparticles showed maximum absorbance at 463 nm, measuring 11.61 in crystal nanosize, and presented spherical in appearance. An antimicrobial activity test was determined with the minimum inhibition concentration (MIC) method. The nanoparticles showed promising inhibitory activity on the Gram-positive and Gram-negative pathogen microorganisms (Escherichia coli ATCC25922, Staphylococcus aureus ATCC29213, Bacillus subtilis ATCC11774, Pseudomonas aeruginosa ATCC27833 bacteria, and Candida albicans yeast) at low concentrations. The cytotoxic and growth inhibitory effects of silver nanoparticles on different cancer cell lines were examined via the MTT assay.

The impact of copper oxide and silver nanoparticles on woody plants obtained by in vitro method

The article substantiates the necessity of studying behaviour of copper oxide and silver nanoparticles on forest cultures (downy birch 29-58 (Betula pubescens Ehrh.) and poplar ‘Pyramidal-osokoreviy Kamyshinsky’ (Poplus pyramidalis Roz. x Poplus nigra L.) in in vitro as well as in ‘soil-plant-microbiota’ to ensure stability of forest cultures in forest regeneration. The impact of nanoparticles on shoot regeneration and propagation processes was evaluated by introducing nanoparticles into Woody Plant medium. Differences in the influence of nanoparticles on the life processes of plants depending on their concentration and the stage of clonal micropropagation have been established. The results are demonstrated by a 15-25% reduction in the frequency of infection of poplar and birch explants as well as by an increase in their regenerating potential at the stage of introduction in tissue culture. When the nanoparticle solution is used in the soil substrate, a decrease in the number of diseased plants and an increase in their survival rate of 30% can be observed. The inhibitory effect of silver nanoparticles on some ecological and trophic groups of microorganisms has been established. These results can be used in the application of CuO and Ag nanoparticles in the biotechnology of clonal micropropagation of forest crops.

Inhibitory Effects of Gold and Silver Nanoparticles on the Differentiation into Osteoclasts In Vitro.

Gold nanoparticles (GNPs) have been widely studied to inhibit differentiation into osteoclasts. However, reports of the inhibitory effects of silver nanoparticles (SNPs) during the process of differentiation into osteoclasts are rare. We compared the inhibitory effect of GNPs and SNPs during the process of differentiation into osteoclasts. Bone marrow-derived cells were differentiated into osteoclasts by the receptor activator of the nuclear factor-kappa-Β ligand (RANKL). The inhibitory effect of GNPs or SNPs during the process of differentiation into osteoclasts was investigated using tartrate-resistant acid phosphatase (TRAP) and actin ring staining. The formation of TRAP positive (+) multinuclear cells (MNCs) with the actin ring structure was most inhibited in the SNP group. In addition, the expression of specific genes related to the differentiation into osteoclasts, such as c-Fos, the nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), TRAP, and Cathepsin K (CTSK) were also inhibited in the SNP groups. As a result, the levels related to differentiation into osteoclasts were consistently lower in the SNP groups than in the GNP groups. Our study suggests that SNPs can be a useful material for inhibiting differentiation into osteoclasts and they can be applied to treatments for osteoporosis patients.

In Vitro Investigation of the Antibacterial Effect of Silver Nanoparticles on ESBL-producing E. coli and Klebsiella spp. Isolated from Pet Animals

Despite the presence of modern antibacterial drugs, bacterial infections are still a major threatening problem due to the enormous increase in multi-drug-resistant bacteria. Nanoparticles have been extensively used as an applicable and safe alternative to antibiotics. The present study aimed to explore the inhibitory effect of silver nanoparticles on Extended Spectrum Beta lactamase (ESBL) producing E. coli and Klebsiella spp. in vitro as well as their effect on the expression of antibiotic resistance genes. Different samples (i.e., wound swabs, Fecal swabs, and urine samples) were collected from dogs and cats. Phenotypic and molecular identification, antibiotic susceptibility testing, and double-disk synergy test were carried out for the identification of ESBL producing E. coli and Klebsiella spp. Silver nanoparticles were tested for their in vitro antibacterial potential and there were reports of their minimum inhibitory concentration and minimum bactericidal concentration. Moreover, the effect of silver nanoparticles on the expression of antibiotic resistance genes (i.e., blaTEM, blaSHV, and blaCTX) was assessed as well as their effect on the structural integrity of the bacterial cells using Scanning Electron Microscope (SEM). Results revealed that 23 isolates (19.16%) (E. coli=17, Klebsiella spp.=6) were confirmed as ESBL producing. Silver nanoparticles indicated a promising antibacterial effect where the minimum inhibitory concentration of AgNPs for ESBL producing E. coli was measured as 0.31 mg/ml, and 0.62 mg/ml for ESBL-producing Klebsiella spp., while the minimum bactericidal concentration of ESBL-producing E. coli and Klebsiella spp. was reported as 0.15 mg/ml and 0.3 mg/ml, respectively. Consequently, the expression of antibiotic resistance genes was downregulated in both bacteria species and there was a noticeable toxic effect of AgNPs on E. coli and Klebsiella spp. cells which was investigated using SEM. It can be concluded that silver nanoparticles have a promising antibacterial activity and could be considered an applicable alternative for the control of ESBL producing bacteria.

Novel Biogenic Silver Nanoparticle-Induced Reactive Oxygen Species Inhibit the Biofilm Formation and Virulence Activities of Methicillin-Resistant Staphylococcus aureus (MRSA) Strain.

Emerging antibiotic-resistant bacteria result in increased mortality and have negative economic impacts. It is necessary to discover new strategies to create alternative antibacterial agents that suppress the bacterial resistance mechanism and limit the spread of serious infectious bacterial diseases. Silver nanoparticles may represent a new medicinal agents as alternative antibiotics affect different bacterial mechanisms such as virulence and resistance. In addition to that of silver nitrate (AgNO3) and ampicillin, for the first time, the inhibitory effect of silver nanoparticles synthesized using Desertifilum sp. (D-SNPs) was evaluated against five pathogenic bacteria using the agar well diffusion method. Also, the influence of D-SNPs and AgNO3 on bacterial antioxidant and metabolic activities was studied. The antibacterial activity of D-SNPs and AgNO3 against methicillin-resistant Staphylococcus aureus (MRSA) strains was studied at the morphological and molecular level. D-SNPs and AgNO3 have the ability to inhibit the growth of the five bacterial strains and resulted in an imbalance in the CAT, GSH, GPx and ATPase levels. MRSA treated with D-SNPs and AgNO3 showed different morphological changes such as apoptotic bodies formation and cell wall damage. Moreover, both caused genotoxicity and denaturation of MRSA cellular proteins. Additionally, TEM micrographs showed the distribution of SNPs synthesized by MRSA. This result shows the ability of MRSA to reduce silver nitrate into silver nanoparticles. These data indicate that D-SNPs may be a significant alternative antibacterial agent against different bacteria, especially MDR bacteria, by targeting the virulence mechanism and biofilm formation, leading to bacterial death.

Investigating the Inhibitory Effect of Silver Nanoparticles against Some Species of Candida and Pathogenic Bacteria

Silver nanoparticles synthesized from aqueous extract of mushroom Pleurotus ostreatus exhibited inhibitory effect at the concentration of 12.5, 25, 50, and 100 mg/ml against some pathogenic bacteria and fungi such as Candida albicans, Candida guilliermondii, Candida krusei, Candida zeylanoides, Geotrichum klebahnii, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The maximum inhibition zone was observed against C. zeylanoides at the concentration of 100 mg/ml was 24.5 mm, while the minimum inhibition zone was observed against Geotrichum at the concentration of 25 mg/ml was 8 mm and the concentration of 12.5 mg/ml was not effective against some species.

Получение стабилизированных наночастиц серебра и изучение их антимикробной и цитотоксической активности в отношении клеток гепатомы человека линии HepG2

Синтезированы наночастицы серебра с использованием для их восстановления и стабилизации арабиногалактана и диоктилсульфосукцината натрия. Средний гидродинамический размер наночастиц, определенный по данным фотонной корреляционной спектроскопии, составлял 30 нм, дзета-потенциал –34.04 ± 1.54 мВ. По данным метода электронной дифракции серебро в образце золя находится в металлической форме. Препарат наночастиц серебра проявлял антибактериальную активность в отношении условно-патогенных грамотрицательных (Escherichia coli) и грамположительных (Bacillus subtilis и B. coagulans) бактерий. Наночастицы серебра также обладали антифунгальной активностью в отношении штаммов фитопатогенных грибов рода Fusarium sporotrichioides и F. solani. Проведено исследование цитотоксической активности наночастиц серебра в отношении клеток гепатомы печени человека линии HepG2. Продемонстрировано ингибирующее действие наночастиц серебра в отношении метаболической активности и жизнеспособности опухолевых клеток. Средние относительные значения EC50 для наночастиц серебра составляли 1.5 ± 0.4 и 41.2 ± 3.9 мкг/мл. Препарат стабилизированных наночастиц серебра может найти применение в медицине в качестве потенциального антимикробного и противоопухолевого средства, а также в сельском хозяйстве в качестве средства подавления роста фитопатогенных грибов.

Comparative study of antibacterial inhibitory effect of silver nanoparticles and garlic oil nanoemulsion with their combination

Silver can inhibit bacterial activity. Previous studies showed that high concentration of silver nanoparticles (AgNPs) in compared to its lower concentrations is toxic for human health. However, by decreasing concentration of AgNPs, antibacterial activity also decreases. In this study, we investigated synergistic inhibitory activity of the combination of AgNPs and garlic oil nanoemulsion (GONE) for increase antibacterial activity of AgNPs at lower concentrations. AgNPs and GONE with sizes of 30.7 and 19.3 nm were synthesized and prepared by chemical reduction and low energy method, respectively. Physicochemical properties of AgNPs and GONE were investigated. The minimum inhibitory concentration (MIC) of samples was assessed using the standard microdilution method against pseudomonas aeruginosa and staphylococcus aureus. P. aeruginosa was suspected to AgNPs and GONE at all concentration, but in the case of S. aureus, antibacterial activity was revealed at ≥29.1% (v/v) and ≥ 36.4 ppb concentration of GONE and AgNPs, respectively. In addition, at low concentration, S. aureus was unsuspected to AgNPs and GONE. Combination of AgNPs and GONE (CAG) demonstrated synergistic inhibitory effects at low concentration (≥29.1% (v/v) and ≥ 36.4 ppb concentration). Also, CAG revealed antibacterial activity against S. aureus at low concentration. These results indicate that combination of GONE and AgNPs has potential as a green antiseptic agent.

Impacts of Continuous Inflow of Low Concentrations of Silver Nanoparticles on Biological Performance and Microbial Communities of Aerobic Heterotrophic Wastewater Biofilm.

Attached-growth wastewater processes are currently used in water resource recovery facilities (WRRFs) for required upgrades due to an increase in influent loading or to reach more stringent discharge criteria. Yet, the distribution and long-term inhibitory effects of silver nanoparticles (AgNPs) in attached-growth biological wastewater processes and their impact on involved microbial communities are poorly understood at relevant, low concentrations. Retention, distribution, and long-term inhibitory effect of polyvinylpyrrolidone (PVP)-coated AgNPs were evaluated in bench-scale moving bed biofilm reactors (MBBRs), achieving soluble organic matter removal, over a 64 day exposure to nominal concentrations of 10 and 100 μg/L. Distributions of continuously added AgNPs were characterized in the influent, bioreactor, and effluent of MBBRs using single particle inductively coupled plasma mass spectroscopy (spICP-MS). Aerobic heterotrophic biofilms in MBBRs demonstrated limited retention capacity for AgNPs over long-term exposure, with release of AgNPs, and Ag-rich biofilm sloughed from the carriers. Continuous exposure to both influent AgNP concentrations significantly decreased soluble chemical oxygen demand (SCOD) removal efficiency (11% to 31%) and reduced biofilm viability (8% to 30%). Specific activities of both intracellular dehydrogenase (DHA) and extracellular α-glucosidase (α-Glu) and protease (PRO) enzymes were significantly inhibited (8% to 39%) with an observed NP dose-dependent intracellular reactive oxygen species (ROS) production and shift in biofilm microbial community composition by day 64. Our results indicated that long-term exposure to AgNPs in biofilm processes at environmentally relevant concentrations can impact the treatment process stability and the quality of the discharged effluent.

Preparation of stabilized silver nanoparticles and study of their antimicrobial and cytotoxic activity on the human hepatoma HepG2 cell line

Silver nanoparticles were synthesized using arabinogalactan and sodium dioctyl sulfosuccinate to reduce and stabilize them. The average hydrodynamic size of the nanoparticles, determined by photon correlation spectroscopy, was 30 nm, and the zeta potential was –34.04 ± 1.54 mV. According to the electron diffraction method, silver in the sol sample is in metallic form. The preparation of silver nanoparticles showed antibacterial activity against opportunistic Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis and B. coagulans) bacteria. Silver nanoparticles also had antifungal activity against strains of phytopathogenic fungi of the genus Fusarium sporotrichioides and F. solani. A study of the cytotoxic activity of silver nanoparticles was made on human hepatoma cells of the HepG2 line. The inhibitory effect of silver nanoparticles on the metabolic activity and viability of tumor cells has been demonstrated. The average relative EC50 values for silver nanoparticles were 1.5 ± 0.4 μg/ml and 41.2 ± 3.9 μg/mL. The preparation of stabilized silver nanoparticles can find application in medicine, as a potential antimicrobial and antitumor agent, as well as in agriculture as a means of suppressing growth of phytopathogenic fungi.

Inhibitory effects of silver nanoparticles on photosystem II performance in Lemna gibba probed by chlorophyll fluorescence

Toxic effects of silver nanoparticles (AgNPs) on photosynthetic processes and biomass were investigated in aquatic plant Lemna gibba, and the plants were exposed to different concentrations of AgNPs for 7 days. At 7 day of exposure, a direct negative impact on the physiological state of plant was indicated by the decrease of chlorophyll (Chl) synthesis, the deterioration of photosynthetic activity and the change in biomass. When L. gibba was treated to 1 mg L−1 of AgNPs, total Chl content and the biomass decreased respectively by 66 and 51% compared to the control (P < 0.05). Under this condition, the alteration of photosystem II (PSII) photochemical reactions was indicated by a significant change compared to control of different studied fluorescence parameters value: FV/FM (35%), ET/RC (63%), VJ (61%), qP (57%) and NPQ (102%). Therefore, Chl a fluorescence measurements showed strong evidence of inhibitory effects on energy transfer from light harvesting complexes to reaction centers, the deterioration of the PSII water splitting system and the inactivation of PSII reaction centers at 1 mg L−1. In conclusion, our results demonstrated that AgNPs induced an inhibitory mechanism on photosynthetic processes and biomass of L. gibba plant.

Fate and inhibitory effect of silver nanoparticles in high rate moving bed biofilm reactors

Municipal water resource recovery facilities are the primary recipients of a significant fraction of discharged silver nanoparticle (AgNP)-containing wastes, yet the fate and potential risks of AgNPs in attached-growth biological wastewater treatment processes are poorly understood. The fate and inhibitory effects of polyvinylpyrrolidone (PVP)-coated AgNPs at environmentally-relevant nominal concentrations (10, 100, 600 μg/L) were investigated, for the first time, in high rate moving bed biofilm reactors (MBBRs) for soluble organic matter removal. The behavior and removal of continuously added AgNPs were characterized using single-particle inductively coupled plasma mass spectrometry (spICP-MS). While no inhibitory effect at average influent concentration of 10.8 μg/L Ag was observed, soluble COD removal efficiency was significantly decreased at 131 μg/L Ag in 18 days and 631 μg/L Ag in 5 days with suppressed biofilm viability. The inhibitory effect of AgNPs on treatment efficiency was highly correlated to the retained mass of total Ag in attached biofilm on the carriers. Biofilm demonstrated limited retention capacity for AgNPs over 18 days. Considerable mass of Ag (38% to 75%) was released via effluent, predominantly as NPs. We detected some chemically transformed and potentially less toxic forms of silver nanoparticles (Ag2S, AgCl), over the exposure period. This study demonstrated the distinct interaction dynamics, bioavailability and inhibitory effects of AgNPs in a biofilm system. Release of bioavailable AgNPs via effluent and AgNP-rich biofilm, sloughing off the carriers, can affect the treatment chain efficiency of downstream processes. Thus, the inhibitory effects of AgNPs can be a concern even at concentrations as low as 100 to 600 μg/L Ag in biological attached growth wastewater treatments.