Sekar Vijayakumar

Plectranthus amboinicus leaf extract mediated synthesis of zinc oxide nanoparticles and its control of methicillin resistant Staphylococcus aureus biofilm and blood sucking mosquito larvae.

In this study, zinc oxide nanoparticles were biologically synthesized using the leaf extract of Plectranthus amboinicus (Pam-ZnO NPs). The synthesized Pam-ZnO NPs were characterized by UV-Vis spectrophotometer, FTIR, TEM and XRD analysis. TEM analysis of Pam-ZnO NPs showed the average size of about 20-50 nm. Pam-ZnO NPs control the growth of methicillin-resistant Staphylococcus aureus biofilms (MRSA ATCC 33591) at the concentration of 8-10 μg/ml. Confocal laser scanning microscope (CLSM) images revealed that Pam-ZnO NPs strongly inhibited the biofilm forming ability of S. aureus. In addition, Pam-ZnO NPs showed 100% mortality of fourth instar mosquito larvae of Anopheles stephensi, Culex quinquefasciatus and Culex tritaeniorhynchus at the concentration of 8 and 10 μg/ml. The histopathological studies of Pam-ZnO NPs treated A. stephensi and C. quinquefasciatus larvae revealed the presence of damaged cells and tissues in the mid-gut. The damaged tissues suffered major changes including rupture and disintegration of epithelial layer and cellular vacuolization. The present study conclude that Pam-ZnO NPs showed effective control of S. aureus biofilms and mosquito larvae by damaging the mid gut cells.

Antibacterial, antibiofilm and cytotoxic effects of Nigella sativa essential oil coated gold nanoparticles

This study reports the biological synthesis of gold nanoparticles using essential oil of Nigella sativa (NsEO-AuNPs). The synthesized NsEO-AuNPs were characterized by UV-visible spectra, X-ray diffraction (XRD), FTIR and Transmission electron microscopy (TEM). UV-vis spectra of NsEO-AuNPs showed strong absorption peak at 540 nm. The X-ray diffraction analysis revealed crystalline nature of nanoparticle with distinctive facets (111, 200, 220 and 311 planes) of NsEO-AuNPs. The FTIR spectra recorded peaks at 3388, 2842, 1685, 1607, 1391 and 1018 cm(-1). TEM studies showed the spherical shape of nanoparticles and the particle size ranges between 15.6 and 28.4 nm. The antibacterial activity of NsEO-AuNPs was greater against Gram positive Staphylococcus aureus MTCC 9542 (16 mm) than Gram negative Vibrio harveyi MTCC 7771 (5 mm) at the concentration of 10 μg ml(-1). NsEO-AuNPs effectively inhibited the biofilm formation of S. aureus and V. harveyi by decreasing the hydrophobicity index (78% and 46% respectively). The in-vitro anti-lung cancer activity confirmed by MTT assay on the cell line of A549 carcinoma cells showed IC50 values of bulk Au at 87.2 μg ml(-1), N. sativa essential oil at 64.15 μg ml(-1) and NsEO-AuNPs at 28.37 μg ml(-1). The IC50 value showed that NsEO-AuNPs was highly effective in inhibiting the A549 lung cancer cells compared to bulk Au and N. sativa essential oil.

Biosynthesis of silver nanoparticles using a probiotic Bacillus licheniformis Dahb1 and their antibiofilm activity and toxicity effects in Ceriodaphnia cornuta.

In the present study, we synthesized and characterized a probiotic Bacillus licheniformis cell free extract (BLCFE) coated silver nanoparticles (BLCFE-AgNPs). These BLCFE-AgNPs were characterized by UV-visible spectrophotometer, XRD, EDX, FTIR, TEM and AFM. A strong surface plasmon resonance centered at 422 nm in UV-visible spectrum indicates the formation of AgNPs. The XRD spectrum of silver nanoparticles exhibited 2θ values corresponding to the silver nanocrystal. TEM and AFM showed the AgNPs were spherical in shape within the range of 18.69-63.42 nm and the presence of silver was confirmed by EDX analysis. Light and Confocal Laser Scanning Microscope (CLSM) images showed a weak adherence and disintegrated biofilm formation of Vibrio parahaemolyticus Dav1 treated with BLCFE-AgNPs compared to control. This result suggests that BLCFE-AgNps may be used for the control of biofilm forming bacterial populations in the biomedical field. In addition, acute toxicity results concluded that BLCFE-AgNPs were less toxic to the fresh water crustacean Ceriodaphnia cornuta (50 μg/ml) when compared to AgNO3 (22 μg/ml). This study also reports a short term analysis (24 h) of uptake and depuration of BLCFE-AgNPs in C. cornuta.

Laurus nobilis leaf extract mediated green synthesis of ZnO nanoparticles: Characterization and biomedical applications

The present study reports the green synthesis of zinc oxide nanoparticles using the aqueous leaf extract of Laurus nobilis (Ln-ZnO NPs) by co-precipitation method. The synthesized Ln-ZnO NPs were characterized by UV-Vis spectroscopy, FTIR, XRD, TEM, SEM and EDX. Ln-ZnO NPs were crystalline in nature, flower like and have hexagonal wurtzite structure with a mean particle size of 47.27nm. The antibacterial activity of Ln-ZnO NPs was greater against Gram positive (Staphylococcus aureus) bacteria than Gram negative (Pseudomonas aeruginosa) bacteria. The zone of inhibition against S. aureus was 11.4, 12.6 and 14.2mm at 25, 50 and 75μgmL-1. The zone of inhibition against P. aeruginosa was 9.8, 10.2 and 11.3mm at 25, 50 and 75μgmL-1. The light and confocal laser scanning microscopic images evidenced that Ln-ZnO NPs effectively inhibited the biofilm growth of S. aureus and P. aeruginosa at 75μgmL-1. The cytotoxicity studies revealed that Ln-ZnO NPs showed no effect on normal murine RAW264.7 macrophage cells. On the other hand, Ln-ZnO NPs were effective in inhibiting the viability of human A549 lung cancer cells at higher concentrations of 80μgmL-1. The morphological changes in the Ln-ZnO NPs treated A549 lung cancer cells were observed under phase contrast microscope.

Biopolymer zein-coated gold nanoparticles: Synthesis, antibacterial potential, toxicity and histopathological effects against the Zika virus vector Aedes aegypti

The control of multidrug-resistant bacteria as well as insect pests and vectors is timely and important now a days. The present study was designed to evaluate the in vitro antibacterial, antibiofilm and mosquito larvicidal effects of gold nanoparticles synthesized using the zein biopolymer (Ze-AuNPs) against Gram positive (Bacillus pumilus and Bacillus subtilis), Gram negative (Shigella sonnei and Pseudomonas aeruginosa) bacteria and third instar larvae of the dengue and Zika virus vector Aedes aegypti. The synthesized Ze-AuNPs were characterized by UV-vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The antibacterial assays testing Ze-AuNPs at 100μg/ml showed that the zones of inhibition against Gram positive species B. pumilus and B. subtilis were 13.9 and 14.2mm, respectively, while for Gram negative S. sonnei and P. aeruginosa they were 18.1 and 18.4mm, respectively. Light and confocal laser scanning microscopy (CLSM) confirmed the interruption and disintegration of bacterial biofilm post-treatment with Ze-AuNPs at 100μg/ml. In larvicidal assays on A. aegypti, HAuCl4 and Ze-AuNPs treated third instar larvae of A. aegypti showed LC50 of 26.6 and 6.81mg/L, respectively, and LC90 of 81.1 and 13.6mg/L respectively. The histopathological analysis of A. aegypti treated with Ze-AuNPs showed complete disintegration of abdominal region, particularly the midgut and caeca, with loss of lateral and caudal hairs. The stereomicroscopic visualization of A. aegypti treated with Ze-AuNPs showed the loss of upper head hair, lower head hair, antenna hair, lateral hair and caudal hair. Overall, the study concludes that Ze-AuNPs have excellent antibacterial, antibiofilm effects and has ability to control the larval populations of A. aegypti mosquitoes.

Biopolymer gelatin-coated zinc oxide nanoparticles showed high antibacterial, antibiofilm and anti-angiogenic activity

The use of natural polymers in drug design plays an important role in biomedical applications. Combinations of nanoparticles (NPs) and biopolymers have been shown to be useful for many purposes. This study focused on gelatin-coated zinc oxide NPs synthesized by co-precipitation. The particles were characterized by UV-Vis spectrum, showing a main peak at 375nm. The stability and crystalline nature of the particles was evaluated by Zeta potential and X-ray diffraction analysis. Fourier transform infrared spectroscopy (FTIR) revealed the possible functional groups of Ge-ZnO NPs, with strong bands at 3851, 3447, and 2923cm-1. Moreover, transmission electron microscopy (TEM) highlighted the presence of spherically shaped Ge-ZnO NPs that were 20nm in size. Energy dispersive analysis X-ray (EDX) analysis showed that the zinc elemental content of Ge-ZnO NPs was 59.10%. The results of antibacterial activity assays revealed higher inhibition of Ge-ZnO NPs against Gram-negative Pseudomonas aeruginosa at 100μg/ml over that against Gram-positive Enterococcus faecalis. Greater inhibition of biofilm formation was observed for Gram-negative bacteria compared to Gram-positive bacteria. In addition, Ge-ZnO NPs effectively inhibited the biofilm growth of the fungus Candida albicans at 50μg/ml. Ge-ZnO NPs reduced the viability of hepatocarcinoma cancer cell lines at 100μg/ml. Moreover, in chick embryos, notable anti-angiogenesis effects were observed for Ge-ZnO NPs and zinc acetate at 50μg/ml compared to that observed testing gelatin. Overall, based on the results, Ge-ZnO NPs may be used as a novel agent for the control of biofilm-forming microbial pathogens.

Dietary supplementation of probiotic Bacillus licheniformis Dahb1 improves growth performance, mucus and serum immune parameters, antioxidant enzyme activity as well as resistance against Aeromonas hydrophila in tilapia Oreochromis mossambicus

ABSTRACT The present study evaluated the dietary supplementation of probiotic Bacillus licheniformis Dahb1 on the growth performance, immune parameters and antioxidant enzymes activities in serum and mucus as well as resistance against Aeromonas hydrophila in Mozambique tilapia Oreochromis mossambicus. Fish (24±2.5g) were fed separately with three diets, 1) commercial diet (control), 2) diet containing probiotic at 105cfug−1 (D1) and 3) diet containing probiotic at 107cfug−1 (D2) for 4 weeks. Growth performance in term of final weight (FW) specific growth rate (SGR) and feed conversion ratio (FCR), immune parameters of total protein (TP), alkaline phosphatase (ALP), myeloperoxidase (MPO), lysozyme (LYZ), reactive oxygen species (ROS), reactive nitrogen species (RNS) and antioxidant parameters of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in serum and mucus were evaluated after 2nd and 4th weeks. The FW, SGR, and FCR of fish fed with D1 and D2 significantly improved (p<0.05). The activities of ALP, LYZ and MPO in the mucus were significantly higher (p<0.05) in fish that fed D1 and D2. The TP, ROS, RNS, SOD and GPx in the serum were significantly higher (p<0.05) in fish that fed D1 and D2. In addition, the challenge test showed that fish fed D1 and D2 enhanced significantly (p<0.05) the resistance against A. hydrophila (1×107cells ml−1). In conclusion, probiotic B. licheniformis Dahb1 can be applied in diet at 107cfug−1 to improve healthy status and resistance against A. hydrophila in tilapia farming. HIGHLIGHTSBacillus licheniformis Dahb1 could be used as feed additive to O. mossambicus.The growth performance of fish fed with the diet containing B. licheniformis Dahb1 significantly improved.Antioxidant and immune parameters in mucus and serum enhanced in B. licheniformis Dahb1 groups.Dietary supplementation of probiotic improved survival rate of O. mossambicus against A. hydrophila challenge.The optimal dose of dietary supplementation of B. licheniformis Dahb1 was 107cfug−1 diet.

Green Synthesized Silver Nanoparticles: Toxicity Against Poecilia reticulata Fishes and Ceriodaphnia cornuta Crustaceans

Recently, the green synthesis of silver nanoparticles gained increasing attention due to interesting properties for optical, antimicrobial and pest control applications. However, their toxicity against micro-crustaceans and fishes has been scarcely explored, while most of the research efforts focused on mosquito control with the green-synthesized nanocomposites. In this study, we investigated the toxic effects of AgNO3, Cissus quadrangularis (Cq)-synthesized AgNPs and Cq extract in two different study models, the larvae of Poecilia reticulata fishes and adults of the micro-crustacean Ceriodaphnia cornuta. In both species, AgNO3 and Cq-AgNPs showed high mortality rates even if tested at very low doses. Molecular analysis revealed high DNA damages induced by Cq-AgNPs on both aquatic organisms. Furthermore, light microscopy studies evidenced lesions in the gills and vacuolization in the gills and in the abdomen of P. reticulata larvae. Overall, our research pointed out that the exposure of aquatic organisms to AgNO3 or green-fabricated AgNPs can damage fishes and crustaceans, posing noteworthy risks to the aquatic ecosystems.

Bioaccumulation, cytotoxicity and oxidative stress of the acute exposure selenium in Oreochromis mossambicus

Selenium (Se) is an essential trace-element that becomes toxic when present at high concentrations for aquatic organisms. The knowledge about the mechanism of Se toxicity in freshwater ecosystem is still poorly studied. Thus the aim of the present study was to assess the impact of environmentally relevant concentrations of Se toxicity: 5, 10, 25, 50 and 100 µg/L or water only (control) for periods of 96 hour (h) to test for Se accumulation (gill, liver and brain), its effects on enzymatic and non-enzymatic antioxidant defenses (gill and liver), oxidative stress effects on lipid, protein (gill and liver), DNA (liver) and inhibition of AchE (brain) activity were measured in Mozambique tilapia, Oreochromis mossambicus. Our result showed that Se accumulation was observed in the gill, liver and brain tissues of fish exposed to different concentrations and accumulation varied upon different tissues. Enzymatic (SOD, CAT, GPx and GST) and non-enzymatic (GSH and MT) antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-s-transferase (GST) were significantly increased after 96 h exposure of higher concentrations Se in the gill and liver tissue with the exception of GST activity was significantly inhibited in liver after 96 h exposure of higher concentrations of Se. In contrast, catalase (CAT) activities were inhibited for both tissues of Se exposure at 96 h. Reduced glutathione (GSH) and Metallothionein (MT) levels were increased in the gill and liver tissues after exposure to Se for 96 h. We also observed that Se affected antioxidant defense, increasing oxidative stress indicator of lipid peroxidation (LPO) and protein carbonyl (PCO) in gill and liver tissues of fish exposed to Se for 96 h at the concentration dependent manner. Increased DNA damage scores observed in liver tissue of fish exposed to Se for concentrations dependent manner, indicating potential of Se on fish. We also observed inhibition of acetylcholine esterase (AchE) activity in brain tissue of fish exposed to Se for higher concentrations. The changes in these parameters can be used as suitable biomarkers for monitoring the toxicity of Se in the aquatic environment.

Bacillus thuringiensis coated zinc oxide nanoparticle and its biopesticidal effects on the pulse beetle, Callosobruchus maculatus

Insect pests belonging to the genus Callosobruchus are the major cause of damage to stored pulse crops. Recently, nanotechnology has emerged as a promising tool for pest control. In the present study, we report for the first time the synthesis and biological evaluation of Bacillus thuringiensis coated zinc oxide nanoparticles (Bt-ZnO NPs) on the pulse beetle, Callosobruchus maculatus. The biologically synthesized Bt-ZnO NPs were extensively characterized using UV-Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and Zeta potential. The bio-physical characterization revealed that the Bt-ZnO NPs has a hexagonal wurtzite structures with an average particle size of 20nm. In addition, zeta potential measurement demonstrated that the Bt-ZnO NPs are negatively charged (-12.7mV) and are moderately stable. The biopesticidal effect of Bt-ZnO NPs was tested against the pulse beetle, C. maculatus. Treatment with Bt-ZnO NPs reduced the fecundity (eggs laid) and hatchability of C. maculatus in a dose-dependent manner. A significant delay in the larval, pupal and total development period of C. maculatus was observed after treatment with Bt-ZnO NPs at 25μg/mL. Furthermore, Bt-ZnO NPs are highly effective in the control of C. maculatus and caused 100% mortality at 25μg/mL. The LC50 value was estimated to be 10.71μg/mL. In addition, treatment with Bt-ZnO NPs decreased the mid-gut α-amylase, cysteine protease, α-glucosidase and glutathione S-transferase (GST) activity in C. maculatus. Our results suggest that Bt-ZnO NPs are effective against C. maculatus and could be used as nanobiopesticides in the control of stored grain insect pests in the future.