Toxicity assessment of palladium oxide nanoparticles derived from metallosurfactants using multi assay techniques in Allium sativum.

In today's world, nanotechnology is reaching practically every ground and entering the human lifestyle by becoming a part of it. Thus, it is vital to check the cytotoxic and genotoxic effects of nanosubstances on plants, as they are the base constituent of ecosystem. The present work deals with the toxicity evaluation of metallosurfactant derived palladium oxide nanoparticles towards Allium sativum (Garlic cloves). The nanoparticles were prepared using microemulsion quenching method (a softer approach) using palladium metallosurfactants as precursors. The three ligands used were cetyltrimethylammonium chloride (CTAC), dodecylamine (DDA) and hexadecylamine (HEXA). Further, their characterization was done using TEM, Size Distribution curve, FESEM, EDS, XRD and Zeta potential. Garlic (Allium sativum) cloves were used to investigate the cytotoxicity and genotoxicity of fabricated PdO NPs. To check the cytotoxicity, optical microscopy was employed and for the genotoxic assessment, different parameters such as chromosomal aberrations in the mitosis, circular dichroism, and gel electrophoresis were utilized. From mitosis study, chromosomes aberrations were confirmed such as chromosomes stickiness, breakage, C-Mitosis, delay in anaphase, spindle fibre abnormality, laggard, vagrant and condensed chromosomes. Morphology of A. sativum clove, rooting and shooting pattern in the presence of PdO nanosuspension was observed. From all the experiments, it was concluded that all the three PdO nanosuspension are toxic in nature to both the cells and to genome, although, bishexadecyltrimethyl ammonium palladium tetrachloride (PdCTAC) Ns was found to be the most cytotoxic and genotoxic. Gel electrophoresis also confirmed the complete degradation of DNA in the presence of PdCTAC Ns.

Transcriptome analysis of silver, palladium, and selenium stresses in Pantoea sp. IMH.

Heavy metal contamination is a significant environmental issue. Using bacteria for removal and reduction of heavy metals is an attractive alternative owing to its low-cost and eco-friendly properties. However, the mechanisms of resistance to and reduction of Ag(I), Pd(II), and Se(IV), especially in the same strain, remain unclear. Here, Pantoea sp. IMH was examed for its reduction of Ag(I), Pd(II), and Se(IV) to nanoparticles (NPs), and the molecular mechanism was investigated by transcriptome analysis. The results revealed that genes encoding binding, transport, catalytic activity, and metabolism were differentially expressed in cells exposed to Ag(I), Pd(II), and Se(IV). The same resistance mechanisms for all metals included multiple stress resistance protein BhsA and glutathione detoxification metabolism. However, zinc transport protein and sulfate metabolism played an important role in the resistance to cationic metals (Ag+ and Pd2+), while the oxalate transporter and arsenic resistance mechanisms were specifically involved in the resistance to and reduction of anion (SeO32-). In addition, Ag(I) was speculated to be reduced to AgNPs by glucose and cytochrome CpxP was involved in Pd(II) reduction. Our results provided new clues on the mechanisms of resistance to and reduction of Ag(I), Pd(II), and Se(IV).

Toxicity studies of nanofabricated palladium against filariasis and malaria vectors.

The present study was carried out to establish the biofabrication of palladium nanoparticles (PdNPs) using the plant leaf extract of Tinospora cordifolia Miers and its toxicity studies on the larvae of filariasis vector, Culex quinquefasciatus Say and malaria vector, Anopheles subpictus Grassi. The biofabricated PdNPs were characterized by using UV-visible spectrum, FTIR, XRD, FESEM, EDX and HRTEM. HRTEM confirmed the PdNPs were slightly agglomerated and spherical in shape and the average size was 16 nm. Gas chromatography and mass spectrometry analysis result revealed that the major constituent present in the T. cordifolia leaf extract is 2,4-di-tert-butylphenol (31.79%) whereas the minor compounds are 1-hexadecanol (7.97%), 1-octadecanol (7.70%), 1-eicosanol (6.85%), behenic alcohol (5.36%), 1-tetradecene (6.22%), cyclotetradecane (6.23%), 1-hexadecene (7.97%), 1-octadecene (7.70%), 1-eicosene (6.85%), and 1-docosene (5.36%). T. cordifolia leaf extract exhibited the larvicidal activity against the fourth instar larvae of C. quinquefasciatus and A. subpictus with the values of LC50 = 59.857 and 54.536 mg/L; LC90 = 113.445 and 108.940 mg/L, respectively. The highest toxicity was observed in the biofabricated PdNPs against the fourth instar larvae of C. quinquefasciatus and A. subpictus with the values of LC50 = 6.090 and 6.454 mg/L; LC90 = 13.689 and 13.849 mg/L, respectively. Concerning non-target effects, Poecilia reticulata were exposed to PdNPs for 24 h and did not exhibit any noticeable toxicity. Overall, our findings strongly suggest that PdNPs is a perfect ecological and inexpensive approach for the control of filariasis and malaria vectors.

Optimization of Surface Coating on Small Pd Nanosheets for in Vivo near-Infrared Photothermal Therapy of Tumor.

Palladium nanosheets with strong near-infrared absorption have been recently demonstrated as promising photothermal agents for photothermal therapy (PTT) of cancers. However, systematic assessments of their potential risks and impacts to biological systems have not been fully explored yet. In this work, we carefully investigate how surface coatings affect the in vivo behaviors of small Pd nanosheets (Pd NSs). Several biocompatible molecules such as carboxymethyl chitosan (CMC), PEG-NH2, PEG-SH, and dihydrolipoic acid-zwitterion (DHLA-ZW) were used to coat Pd NSs. The blood circulation half-lives, biodistribution, potential toxicity, clearance, and photothermal effect of different surface-coated Pd NSs in mice after intravenous injection were compared. PEG-SH-coated Pd NSs (Pd-HS-PEG) were found to have ultralong blood circulation half-life and show high uptake in the tumor. We then carry out the in vivo photothermal therapeutic studies on the Pd-HS-PEG conjugate and revealed its outstanding efficacy in in vivo photothermal therapy of cancers. Our results highlight the importance of surface coatings to the in vivo behaviors of nanomaterials and can provide guidelines to the future design of Pd NSs bioconjugates for other in vivo applications.

Amyloid fibrils enhance transport of metal nanoparticles in living cells and induced cytotoxicity.

Amyloid protein fibrils occur in vivo as pathological agents, in the case of neurodegenerative diseases, or as functional amyloids, when playing biologically vital roles. Here we show how amyloid fibrils generated from a food protein, ß-lactoglobulin, can be used as nanoreactors for the synthesis of metal nanoparticles and demonstrate that the resulting hybrids can play a central role in the internalization of nanoparticles into living cells, with up to 3-fold-enhanced transport properties over pristine nanoparticles. We conjugate gold, silver, and palladium nanoparticles onto amyloid fibrils by chemical reduction, and we study their effect on dendritic and MCF7 breast cancer cells. Transmission electron microscopy indicates localization of nanoparticles inside vesicles of the cells. Flow cytometry reveals that silver nanoparticle-amyloid hybrids are cytotoxic, while gold and palladium nanoparticle-amyloid hybrids produce no notable effect on cell viability and activation status.

Evaluating the abnormal ossification in tibiotarsi of developing chick embryos exposed to 1.0ppm doses of platinum group metals by spectroscopic techniques.

Platinum group metals (PGMs), i.e., palladium (Pd), platinum (Pt) and rhodium (Rh), are found at pollutant levels in the environment and are known to accumulate in plant and animal tissues. However, little is known about PGM toxicity. Our previous studies showed that chick embryos exposed to PGM concentrations of 1mL of 5.0ppm (LD50) and higher exhibited severe skeletal deformities. This work hypothesized that 1.0ppm doses of PGMs will negatively impact the mineralization process in tibiotarsi. One milliliter of 1.0ppm of Pd(II), Pt(IV), Rh(III) aqueous salt solutions and a PGM-mixture were injected into the air sac on the 7th and 14th day of incubation. Control groups with no-injection and vehicle injections were included. On the 20th day, embryos were sacrificed to analyze the PGM effects on tibiotarsi using four spectroscopic techniques. 1) Micro-Raman imaging: Hyperspectral Raman data were collected on paraffin embedded cross-sections of tibiotarsi, and processed using in-house-written MATLAB codes. Micro-Raman univariate images that were created from the ν1(PO4(3-)) integrated areas revealed anomalous mineral inclusions within the bone marrow for the PGM-mixture treatment. The age of the mineral crystals (ν(CO3(2-))/ν1(PO4(3-))) was statistically lower for all treatments when compared to controls (p≤0.05). 2) FAAS: The percent calcium content of the chemically digested tibiotarsi in the Pd and Pt groups changed by ~45% with respect to the no-injection control (16.1±0.2%). 3) Micro-XRF imaging: Abnormal calcium and phosphorus inclusions were found within the inner longitudinal sections of tibiotarsi for the PGM-mixture treatment. A clear increase in the mineral content was observed for the outer sections of the Pd treatment. 4) ICP-OES: PGM concentrations in tibiotarsi were undetectable (<5ppb). The spectroscopic techniques gave corroborating results, confirmed the hypothesis, and explained the observed pathological (skeletal developmental abnormalities) and histological changes (tibiotarsus ischemia and nuclear fragmentation in chondrocytes).

Pd-nanoparticles cause increased toxicity to kiwifruit pollen compared to soluble Pd(II).

In the present study, endpoints including in vitro pollen performance (i.e., germination and tube growth) and lethality were used as assessments of nanotoxicity. Pollen was treated with 5-10 nm-sized Pd particles, similar to those released into the environment by catalytic car exhaust converters. Results showed Pd-nanoparticles altered kiwifruit pollen morphology and entered the grains more rapidly and to a greater extent than soluble Pd(II). At particulate Pd concentrations well below those of soluble Pd(II), pollen grains experienced rapid losses in endogenous calcium and pollen plasma membrane damage was induced. This resulted in severe inhibition and subsequent cessation of pollen tube emergence and elongation at particulate Pd concentrations as low as 0.4 mg L(-1). Particulate Pd emissions related to automobile traffic have been increasing and are accumulating in the environment. This could seriously jeopardize in vivo pollen function, with impacts at an ecosystem level.

Permanganate oxidation of sulfur compounds to prevent poisoning of Pd catalysts in water treatment processes.

The practical application of Pd-catalyzed water treatment processes is impeded by catalyst poisoning by reduced sulfur compounds (RSCs). In this study, the potential of permanganate as a selective oxidant for the removal of microbially generated RSCs in water and as a regeneration agent for S-poisoned catalysts was evaluated. Hydrodechlorination using Pd/Al2O3 was carried out as a probe reaction in permanganate-pretreated water. The activity of the Pd catalysts in the successfully pretreated reaction medium was similar to that in deionized water. The catalyst showed no deactivation behavior in the presence of permanganate at a concentration level < or = 0.07 mM. With a residual oxidant concentration of > or = 0.08 mM, a significant but temporary inhibition of the catalytic dechlorination was observed. Unprotected Pd/Al2O3, which had been completely poisoned by sulfide, was reactivated by a combined treatment with permanganate and hydrazine. However, the anthropogenic water pollutants thiophene and carbon disulfide were resistant against permanganate. Together with the preoxidation of catalyst poisons, hydrophobic protection of the catalysts was studied. Pd/zeolite and various hydrophobically coated catalysts showed a higher stability against ionic poisons and permanganate than the uncoated catalyst. By means of a combination of oxidative water pretreatment and hydrophobic catalyst protection, we provide a new tool to harness the potential of Pd-catalyzed hydrodehalogenation for the treatment of real waters.

Biological impact of contact with metals on cells.

In order to investigate the in vivo effect of metals used in dentistry, we investigated the effect of direct contact with metal plates (20 x 20 x 0.5 mm3) made of gold (Au), silver (Ag), copper (Cu) or palladium (Pd) on human promyelocytic leukemic HL-60 cells grown in RPMI1640 medium supplemented with 10% fetal bovine serum. When 0.5 mL of cell suspension was applied to the metal plates, cells were precipitated on the surface of the metal plate within 10 min. Contact with Cu induced a rapid decline of cell viability, the smear pattern of DNA fragmentation, and only minor activation of caspase-3. These effects were accompanied by a progressive decrease in the extracellular concentration of methionine, cysteine and histidine, with a corresponding increase in the concentration of methionine sulfoxide. Electron microscopy showed that contact with Cu induced vacuolization and cytoplasmic damage, prior to nuclear damage, without affecting the cell surface microvilli or mitochondrial integrity. Contact with the other metals did not induce such changes during the 3 h incubation, nor was any hormetic response (beneficial action at lower concentration) observed in the cells with any metals. Addition of N-acetyl-L-cysteine (4-5 mM) almost completely abrogated the Cu-induced cytotoxicity, whereas sodium ascorbate (0.1-0.5 mM) and catalase (6,000(1)-30,000 units/mL) were ineffective. Numerous serum proteins were adsorbed to the Ag plate, while bovine serum albumin was the major protein adsorbed to other metal plates. The present study suggests that direct contact with Cu induced non-apoptotic cell death by an oxidation-involved mechanism. The present model system may be applicable to the study of the interaction between cells and dental restorative materials.