Both biogenic and chemically synthesized metal sulfide nanoparticles induce oxidative stress and enhance lipid accumulation in Rhodococcus opacus

Metallic nanoparticles (NPs) find applications in many different industrial sectors. However, the fate of these NPs in the environment and their potential impact on organisms living in different ecosystems are not fully known. In this work, the individual effect of biogenic and chemically synthesized lead sulfide nanoparticles (PbSNPs) and cadmium sulfide nanoparticles (CdSNPs) on the activity of the oleaginous bacterium Rhodococcus opacus PD630 which belongs to an ecologically important genus Rhodococcus was investigated. A dose-dependent increase in PbSNPs and CdSNPs uptake by the bacterium was observed upto a maximum of 16.4 and 15.6 mg/g cell, corresponding to 98% and 95% uptake. In the case of chemically synthesized NPs, the specific PbSNPs and CdSNPs uptake were slightly less [15.5 and 14.8 mg/g cell], corresponding to 93.2% and 88.4% uptake. Both biogenic and chemically synthesized PbSNPs and CdSNPs did not affect the bacterial growth. On the other hand, the triacylglycerol (biodiesel) content in the bacterium increased from 30% to a maximum of 75% and 73% CDW due to oxidative stress induced by biogenic PbSNPs and CdSNPs. The results of induced oxidative stress by biogenic metal nanoparticle were similar to that induced by the chemically synthesized NPs.

Effects of cadmium sulfide nanoparticles on sulfate bioreduction and oxidative stress in Desulfovibrio desulfuricans

Sulfate-containing wastewater has a serious threat to the environment and human health. Microbial technology has great potential for the treatment of sulfate-containing wastewater. It was found that nano-photocatalysts could be used as extracellular electron donors to promote the growth and metabolic activity of non-photosynthetic microorganisms. However, nano-photocatalysts could also induce oxidative stress and damage cells. Therefore, the interaction mechanism between photosynthetic nanocatalysts and non-photosynthetic microorganisms is crucial to determine the regulatory strategies for microbial wastewater treatment technologies. In this paper, the mechanism and regulation strategy of cadmium sulfide nanoparticles (CdS NPs) on the growth of sulfate-reducing bacteria and the sulfate reduction process were investigated. The results showed that the sulfate reduction efficiency could be increased by 6.4% through CdS NPs under light conditions. However, the growth of Desulfovibrio desulfuricans C09 was seriously inhibited by 55% due to the oxidative stress induced by CdS NPs on cells. The biomass and sulfate reduction efficiency could be enhanced by 6.8% and 5.9%, respectively, through external addition of humic acid (HA). At the same time, the mechanism of the CdS NPs strengthening the sulfate reduction process by sulfate bacteria was also studied which can provide important theoretical guidance and technical support for the development of microbial technology combined with extracellular electron transfer (EET) for the treatment of sulfate-containing wastewater.

Production of cadmium sulfide quantum dots by the lithobiontic Antarctic strain Pedobacter sp. UYP1 and their application as photosensitizer in solar cells

Background

Microbes are present in almost every environment on Earth, even in those with extreme environmental conditions such as Antarctica, where rocks may represent the main refuge for life. Lithobiontic communities are composed of microorganisms capable of colonizing rocks and, as it is a not so well studied bacterial community, they may represent a very interesting source of diversity and functional traits with potential for biotechnological applications. In this work we analyzed the ability of Antarctic lithobiontic bacterium to synthesize cadmium sulfide quantum dots (CdS QDs) and their potential application in solar cells.

Results

A basaltic andesite rock sample was collected from Fildes Peninsula, King George Island, Antarctica, and processed in order to isolate lithobiontic bacterial strains. Out of the 11 selected isolates, strain UYP1, identified as Pedobacter, was chosen for further characterization and analysis due to its high cadmium tolerance. A protocol for the biosynthesis of CdS QDs was developed and optimized for this strain. After 20 and 80 min of synthesis, yellow-green and orange-red fluorescent emissions were observed under UV light, respectively. QDs were characterized through spectroscopic techniques, dynamic light scattering analysis, high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy. Nanostructures of 3.07 nm, composed of 51.1% cadmium and 48.9% sulfide were obtained and further used as photosensitizer material in solar cells. These solar cells were able to conduct electrons and displayed an open circuit voltage of 162 mV, a short circuit current density of 0.0110 mA cm⁻², and had an efficiency of conversion up to 0.0016%, which is comparable with data previously reported for solar cells sensitized with biologically produced quantum dots.

Conclusions

We report a cheap, rapid and eco-friendly protocol for the production of CdS QDs by an Antarctic lithobiontic bacterium, Pedobacter, a genus that was not previously reported as a quantum dot producer. The application of the biosynthesized QDs as sensitizer material in solar cells was validated.

Possible Mechanisms of Liver Injury Induced by Cadmium Sulfide Nanoparticles in Rat

Cadmium is primarily utilized in the construction of particles known as quantum dots. Hepatotoxicity caused by microparticles of cadmium is very well known; however, toxicity of nanoparticles of cadmium is not well understood. The present study describes the toxicity of cadmium sulfide nanoparticles (CdSNPs) in the liver of rat. Adult Wistar rats were administered CdSNPs (10 mg/kg) on alternate days for 45 days. Serum enzymes (ALT, AST, ALP), biomarkers of lipid peroxidation (MDA, H₂O₂, and NO), and metallothionein concentration were determined. Histopathological and TEM observations were also made to record morphological changes. CdSNPs (10 mg/kg) induced significant changes in the structure and function of liver. Values of serum enzymes and reactive species increased significantly in rats treated with CdSNPs in comparison to CdS-treated rats. Histopathological observations showed extensive parenchymal degeneration. Ultrastructural studies exhibited proliferation of endoplasmic reticulum, microsomes, and lysosomes. It is concluded that NP-membrane interaction leads to the generation of reactive species that alter membrane integrity and induce oxidative stress. These events may activate cell death pathways in hepatocytes.

Cadmium sulfide nanoparticles-assisted intimate coupling of microbial and photoelectrochemical processes: Mechanisms and environmental applications

Intimate coupling of microbial extracellular electron transfer (EET) and photoelectrochemical processes is an emerging research area with great potential to circumvent many disadvantages associated with traditional techniques that depend on independent microbial or photocatalysis treatment. Microbial EET processes involve microorganism oxidation of extracellular electron donors for respiration and synchronous reduction of extracellular electron acceptors to form an integrated respiratory chain. Coupled microbial EET-photoelectrochemical technologies greatly improve energy conversion efficiency providing both economic and environmental benefits. Among substitutes for semiconductor photocatalysts, cadmium sulfide nanoparticles (CdS NPs) possess several attractive properties. Specifically, CdS NPs have suitable electrical conductivity, large specific surface area, visible light-driven photocatalysis capability and robust biocompatibility, enabling them to promote hybrid microbial-photoelectrochemical processes. This review highlights recent advances in intimately coupled CdS NPs-microbial extracellular electron transfer systems and examines the mechanistic pathways involved in photoelectrochemical transformations. Finally, the prospects for emerging applications utilizing hybrid CdS NPs-based microbial-photoelectrochemical technologies are assessed. As such, this review provides a rigorous fundamental analysis of electron transport dynamics for hybrid CdS NPs-microbial photoelectrochemical processes and explores the applicability of engineered CdS NPs-biohybrids for future applications, such as in environmental remediation and clean-energy production.

Evaluation of bioactivities of zinc oxide, cadmium sulfide and cadmium sulfide loaded zinc oxide nanostructured materials prepared by nanosecond pulsed laser

The present study reports the preparation of cadmium sulfide (CdS) loaded zinc oxide (ZnO) nanostructured semiconductor material and its anti-bioactivity studies against cancerous and fungus cells. For composite preparation, two different mass ratios of CdS (10 and 20%) were loaded on ZnO (10%CdS/ZnO, 20%CdS/ZnO) using a 532 nm pulsed laser ablation in water media. The structural and morphological analyses confirmed the successful loading of nanoscaled CdS on the surface of ZnO particles, ZnO particles were largely spherical with average size ~50 nm, while CdS about 12 nm in size. The elemental and electron diffraction analyses reveal that the prepared composite, CdS/ZnO contained both CdS and ZnO, thus reaffirming the production of CdS loaded ZnO. The microscopic examination and MTT assay showed the significant impact of ZnO, CdS, and CdS loaded ZnO on human colorectal carcinoma cells (HCT-116 cells). Our results show that the prepared ZnO had better anticancer activities than individual CdS, and CdS loaded ZnO against cancerous cells. For antifungal efficacy, as-prepared nanomaterials were investigated against Candida albicans by examining minimum inhibitory/fungicidal concentration (MIC/MFC) and morphogenesis. The lowest MIC (0.5 mg/mL), and MFC values (1 mg/mL) were found for 10 and 20%CdS/ZnO. Furthermore, the morphological analyses reveal the severe damage of the cell membrane upon exposure of Candida strains to nanomaterials. The present study suggests that ZnO, CdS, and CdS loaded ZnO nanostructured materials possess potential anti-cancer and anti-fungal activities.

Escherichia coli-based synthesis of cadmium sulfide nanoparticles, characterization, antimicrobial and cytotoxicity studies

The present research describes the synthesis of cadmium sulfide (CdS) nanoparticles from Escherichia coli under the influence of bacterial enzyme sulphate reductase and study on their cytotoxicity for applications in cancer therapy. Escherichia coli cells were used to synthesize CdS nanoparticles under different concentrations of cadmium chloride and sodium sulfide. The morphology of the nanoparticles was analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) was used for elemental analysis of nanoparticles. Fourier-transform infrared spectroscopy analysis (FTIR) was performed to assess the functional groups of the nanoparticles. Crystalline nature of nanoparticles was assessed using powder X-ray diffraction (XRD). Antibacterial studies of CdS nanoparticles were carried out on foodborne pathogens and cytotoxicity studies were carried out on Mus musculus skin melanoma (B16F10) and human epidermoid carcinoma (A431) cell lines. CdS nanoparticle showed more cytotoxic effect on cancer cells compared with standard 5-aminolevulinic acid (5-ALA). The Escherichia coli-synthesized CdS nanoparticles showed highest zone of inhibition in the ratio 4:1 of cadmium chloride and sodium sulfide on all tested bacterial strains. The nanoparticles were also tested for haemolytic activity on RBC cells, which exhibited lower cytotoxicity than sodium dodecyl sulphate which was used as positive control. The cytotoxicity of CdS nanoparticles assessed on A431 cells showed an inhibition of 81.53% at 100 μM concentration while the cytotoxicity assessed on B16F10 cells showed an inhibition of 75.71% at 200 μM concentration which was much efficient than 5-ALA which showed an inhibition of 31.95% at a concentration against B16F10 cells and 33.45% against A431 cells at a concentration of 1 mM. Cadmium sulfide nanoparticles were thus found to be highly toxic on cancer cells compare with standard anticancerous drug 5-ALA.

Different behavior of Staphylococcus epidermidis in intracellular biosynthesis of silver and cadmium sulfide nanoparticles: more stability and lower toxicity of extracted nanoparticles

Chemical reagents that are used for synthesis of nanoparticles are often toxic, while biological reagents are safer and cost-effective. Here, the behavior of Staphylococcus epidermidis (ATCC 12228) was evaluated for biosynthesis of silver nanoparticles (Ag-NPs) and cadmium sulfide nanoparticles (CdS-NPs) using TEM images intra- and extracellularly. The bacteria only biosynthesized the nanoparticles intracellularly and distributed Ag-NPs throughout the cytoplasm and on outside surface of cell walls, while CdS-NPs only formed in cytoplasm near the cell wall. A new method for purification of the nanoparticles was used. TEM images of pure CdS-NPs confirmed biosynthesis of agglomerated nanoparticles. Biosynthetic Ag-NPs were more stable against bright light and aggregation reaction than synthetic Ag-NPs (prepared chemically) also biosynthetic Ag-NPs displayed lower toxicity in in vitro assays. CdS-NPs indicated no toxicity in in vitro assays. Biosynthetic nanoparticles as product of the detoxification pathway may be safer and more stable for biosensors.

Biochemical and behavioural responses of the marine polychaete Hediste diversicolor to cadmium sulfide quantum dots (CdS QDs): waterborne and dietary exposure

Cadmium sulfide (CdS) quantum dots are widely used in medical imaging. The aim of this study was to examine toxicity effects of CdS engineered nanoparticles (CdS NPs) compared to soluble Cd, on marine ragworms (Hediste diversicolor) exposed for 14 d to these contaminants (10 μg Cd L(-1)) in seawater or via their food (contaminated worm tissue). In our experimental media, Dynamic Light Scattering studies showed that the majority of CdS remained in the nanoscale (1-10 nm) with the exception of few aggregates (100-300 nm). Labile Cd fractions released from CdS NPs were estimated by diffusive gradient in thin films, showing that about 50% of CdS NPs remained in nanoparticulate form. Ragworms accumulated Cd in both soluble Cd and CdS NPs in waterborne exposures only. Greater significant changes of biochemical responses were observed in worms exposed to CdS NPs in seawater compared to contaminated food. Catalase and glutathione-S-transferase activities were the most sensitive biochemical biomarkers responding to both Cd treatments for waterborne exposure. Inductions of CAT were higher in diet-exposed worms to Cd as NPs vs soluble form suggesting a specific "nano" effect. Caspase activities increased in worms exposed to soluble Cd and Cd NPs for the two routes of exposure compared to controls. Defences, may be insufficient to prevent reactive oxygen species generation and the associated apoptosis. Behaviour of invertebrates inside sediment showed impairments of body movements in worms exposed to CdS NPs. This study points out oxidative processes as the main consequences of exposure to Cd based NPs in worms.