NiS Particles Research Articles

Heterogeneous photocatalytic degradation of furfural using NiS-clinoptilolite zeolite

NiS-clinoptilolite is prepared by ion exchange and precipitation procedures and is characterized by Fourier transformation infrared, X-ray diffraction, thermal analysis, SEM and BET methods. The prepared composite is used as a catalyst for photodegradation of furfural in aqueous solution under UV irradiation. The degradation process is monitored during the experimental runs by UV/Vis absorption, COD and TOC concentration determination and HPLC methods. The effect of key operating parameters such as catalyst dosage, initial concentration of furfural, initial pH of the solutions and effect of the presence of hydrogen peroxide and potassium bromate is studied on the degradation efficiency. The optimal operation parameters are found as follows: pH 5, 330 mg L − 1 of the catalyst loading and 6 mM of furfural concentration. It observed that the degradation rate increased with an increasing mass of hydrogen peroxide and potassium bromate. The NiS particles out of the zeolite framework did not show significant degradation efficiency.

Photodecolorization of Eriochrome Black T using NiS–P zeolite as a heterogeneous catalyst

NiS–P zeolite was prepared by ion exchange and precipitation procedures and it was characterized by FT-IR, SEM and thermal methods. The prepared composite was used as a catalyst in the photodecolorization process of Eriochrome Black T (E.B.T.) dye in aqueous solution under UV irradiation. The effect of key operating parameters such as catalyst dosage, temperature, initial concentration of the dye and initial pH of the solutions were studied on the decolorization process of dye. The primary objective was to determine the optimal conditions for each of the parameters. UV–vis spectrophotometric measurements were performed for the determination of decolorization and mineralization extents. The optimal operation parameters were found as follows: pH 9.1, 0.8 g L −1 of catalyst loading and 40 ppm of dye concentration. The NiS particles out of zeolite framework did not show significant decolorization efficiency. The decolorization process obeyed first-order kinetics.

硫化金属微粒子をマトリックスとする表面支援レーザー脱離イオン化法の研究

Metal sulfide compounds have unique properties and are widely used in various applications. In this study, we investigated the efficacy of metal sulfide particles as matrices for the ionization of synthetic polymers, by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). After the preparation of metal sulfide particles (NiS, CuS, and ZnS) using a shaker, the dispersed solutions of matrix and analytes were spotted on an LDI plate and measured using a 337 nm nitrogen laser. Among the particles studied, NiS particles were the most efficient matrix for SALDI-MS.

模擬めっき廃液中の銅，亜鉛，ニッケルイオンの硫化カルシウムによる選択硫化と生成金属硫化物スラリーのろ過特性

Sulfidatiosn treatment of a mixed metal solution containing Cu2+, Zn2+, and Ni2+ ions was conducted using CaS as the sulfidation agent. The selective recovery of these metal sulfides was studied. Furthermore, filtration characteristics of the NiS cake obtained with CaS, Na2S, and NaOH as precipitation agents were compared in terms of their average specific filtration resistance and compressibility coefficient. Results show that selective precipitation of metal sulfides was achieved by sulfidation treatment with CaS at pH of 1.8-2.0 for CuS precipitation and at pH of 5.5-6.0 for ZnS precipitation. Based on the high performance of filtration of the resultant nickel sulfides, it was concluded that solid CaS was more effective for filtration of NiS cake than Na2S or NaOH as a precipitation agent because NiSO4 was sulfidated with solid CaS, thereby forming larger NiS particles by agglomeration.

Electronic behaviours of calcined materials from a (S-nickel-S-phenylene-O)-strontium-(O-phenylene-S-selenium-S) hybrid copolymer

The calcination of a (S-nickel-S-phenylene-O)-strontium-(O-phenylene-S-selenium-S) hybrid copolymer under an argon atmosphere at 400–600 ∘C was performed. 600 ∘C-calcined material was found to be composed of nano-sized NiS, SrS and Se particles in the matrix of the carbon clusters. ESR spectral examinations of the calcined material suggest the possibility of an electron transport in the process of carbon clusters → NiS → SrS → Se with a photoresponsive oxidation–reduction function.

Insight into the formation of the active phases in supported NiW hydrotreating catalysts

Abstract The sulfidation mechanism of supported NiW hydrotreating catalysts is described in detail based on literature data and experiments for carbon- and alumina-supported NiW catalysts. It is more difficult to convert tungsten oxides to WS 2 than molybdenum oxides to MoS 2 and therefore typical sulfidation procedures tend to result in oxysulfidic tungsten phases (WO x S y ) next to the layered WS 2 phase. The former phase appears to stabilize rather dispersed Ni sulfide particles (NiS–WO x S y ) which is found to be a precursor to the ‘Ni–W–S’ phase: Mossbauer spectroscopy clearly shows that the NiS particles redisperse over the WS 2 edges when partly oxidic tungsten phases transform to WS 2 slabs. As a consequence of very slow W sulfidation, the Ni promoter ion can end up in two phases, i.e. ‘Ni–W–S’-type and in NiS–WO x S y phases, this in contrast to Co(Ni)Mo catalysts that mainly contain ‘Co(Ni)–Mo–S’ phases after typical sulfidation procedures. The NiS–WO x S y phase is known to perform well in liquid-phase hydrodesulfurization (HDS) reactions whereas the ‘Ni–W–S’ phase is most active for gas-phase HDS. The relative speciation of these two phases for alumina-supported NiW can be controlled by parameters as the calcination temperature and the sulfidation temperature and pressure. Notably, elevated sulfidation pressures are preferred over elevated sulfidation temperatures because in the latter case the WS 2 slabs tend to sinter and crystallize which negatively affects the performance. This work shows the existence of a strong support effect for carbon- and alumina-supported NiW. Similar trends were found for amorphous-silica–alumina-supported NiW which is consistent with the finding that the sulfidation mechanism is similar to that of NiW/Al 2 O 3 . Even when WS 2 sulfidation is completed, as for instance found for a carbon-supported NiW catalyst at 673 K, a significant fraction of Ni is not involved in the ‘Ni–W–S’ phase. Chelating agents improve the edge occupation in NiW catalysts significantly by retarding Ni sulfidation. The result is a more efficient formation of the ‘Ni–W–S’ phase and optimized catalysts have a significantly higher activity than conventional ones.

Nickel carcinogenesis: Epigenetics and hypoxia signaling

Both water soluble and insoluble nickel compounds have been implicated in the etiology of human lung and nasal cancers. Water insoluble nickel compounds have been shown to enter cells by phagocytosis and are contained in cytoplasmic vacuoles, which are acidified thus accelerating the dissolution of soluble nickel from the particles. Using Newport Green, a dye that fluoresces when ionic nickel is bound, we have shown that following exposure (48–72 h) of human lung (A549) cells to NiS particles, most of the nickel is contained in the nucleus, while cells exposed to soluble NiCl 2 exhibit most of the ions localized in the cytoplasm. This effect is consistent with previously published reports showing that short-term exposure of cells to crystalline nickel particles (1–3 days) is able to epigenetically silence target genes placed near heterochromatin, while similar short-term exposure to soluble nickel compounds are not able to induce silencing of genes placed near heterochromatin. However, a 3 week exposure of cells to soluble NiCl 2 is also able to induce gene silencing. A similar effect was found in yeast cells where nickel was able to silence the URA-3 gene placed near (1.3 kb) a telomere silencing element, but not when the gene was placed farther away from the silencing element (2.0 kb). In addition to epigenetic effects, nickel compounds activate hypoxia signaling pathways. The mechanism of this effect involves the ability of either soluble or insoluble nickel compounds to block iron uptake leading to cellular iron depletion, directly affect iron containing enzymes, or both. This results in the inhibition of a variety of iron-dependent enzymes, such as aconitase and the HIF proline hydroxylases (PHD1-3). The inhibition of the HIF proline hydroxylases stabilizes the HIF protein and activates hypoxic signaling. Additional studies have shown that nickel and hypoxia decrease histone acetylation and increase the methylation of H3 lysine 9. These events are involved in gene silencing and hypoxia can also cause these effects in human cells. It is hypothesised that the state of hypoxia either by low oxygen tension or as a result of agents that signal hypoxia under normal oxygen tension (iron chelation, nickel and cobalt) results in low levels of acetyl CoA, which is a substrate for histone and other protein acetylation. This effect may in part be responsible for the gene silencing following nickel exposure and during hypoxia.

The Effect of Support Interaction on the Sulfidability of Al2O3- and TiO2-Supported CoW and NiW Hydrodesulfurization Catalysts

The effect of the degree of W sulfidation on dispersion, morphology, thiophene hydrodesulfurization (HDS) activity, and promotional behavior for supported Ni(Co)W sulfide catalysts was studied by varying the calcination temperature, sulfidation temperature, sulfidation pressure, and support. The catalysts were characterized by thiophene HDS, X-ray photoelectron spectroscopy; transmission electron microscopy, extended X-ray absorption fine-structure, and Mössbauer emission measurements. Assuming that sulfidation to a WS2 phase proceeds via a WOxSy phase it can be concluded that the ratio between these two phases depends on the sulfidation conditions and W–support interaction. For the highest thiophene HDS activity, sulfidation conditions that result in nearly maximum sulfidation of the WOxSy phase are necessary. However, one should be aware that complete sulfidation results in the formation of WS2, which is more susceptible to sintering. For Al2O3-supported NiW catalysts preferable sulfidation conditions are a low temperature and a high H2S/H2 sulfidation pressure. In contrast, for TiO2-supported NiW the calcination and sulfidation temperatures have to be low and sulfidation at atmospheric H2S/H2 pressure is already sufficient, because W is more easily sulfided due to its weak interaction with TiO2. The degree of sulfidation also affects the promotional behavior. The optimal Ni/W ratio is higher than the optimal Ni/Mo ratio, while in contrast to CoMo catalysts, for CoW no optimal ratio could be found. In addition, the activity of CoW appeared about the same as the sum of the W and Co activities, regardless of the Co content. In the case of NiW and CoW, Ni and Co are sulfided first. As soon as WS2 appears, the NiS particles already formed partially redisperse to form NiWS, while the CoS particles tend to form a separate Co9S8 phase instead of CoWS.

Formation of nickelhydroxy sulfide precursor and nickel sulfide in Langmuir and Langmuir–Blodgett films of a nickel complex of octadecylsuccinic acid

The influence of parameters on size of NiS particles formed at ambient temperatures by reacting Na 2S with the nickel salt of octadecylsuccinic acid (ODSA) at the air/water interface and in Langmuir–Blodgett films was investigated by changes in surface pressure–molecular area (π– A) and surface potential–molecular area (Δ V– A) isotherms. The contraction in area of ODSA on Ni 2+ subphase is indicative of a strong interaction of the dibasic acid with Ni 2+ leading to a monodentate complex of Ni 2+ with ODSA. The Langmuir monolayers of the nickel complex of ODSA were analysed using Brewster angle microscopy (BAM). In the absence of nickel in the subphase, ODSA exhibited no domains in BAM. The sulfidation reaction on ODSA/Ni 2+ complex at the air/water interface shows two steps as seen in the surface potential vs. time plot corresponding to formation of Ni(OH)S initially which then changes to NiS. The domain size seen with NiS formation increased with time and surface pressure indicating the growth of a two-dimensional solid complex in the monolayer at the air/water interface. The Langmuir–Blodgett (LB) films of ODSA/Ni 2+ on sulfidation transferred onto solid substrates from the two steps in the reaction were characterized using diffuse reflectance UV-visible spectroscopy (DIR-UV-vis) and X-ray photoemission spectroscopy. These experiments confirmed the reduction process involved in the above reaction. Atomic force microscopy experiments on these LB films indicated that there is a variation in the structural organization in the monolayers and in the morphology of the LB film, depending on the initial Ni(OH)S formation which ultimately leads to NiS. The results show that the average particle size which varies between 2 and 3.5 nm depends on the nature of the nickel complexes formed at the air/water interface.

Evolution of crystalline phases in nickel–tungsten sulfide catalysts

Unsupported Ni–W sulfide catalysts were prepared employing ammonium thiotungstate complexes and nickel nitrate as metal-sulfide precursors. Structural characterization was carried out by XRD and HRTEM measurements. XRD patterns show crystallinity enhancement of WS 2 particles as the W content in the mixed catalysts was decreased. HRTEM demonstrates that WS 2 layers start to coat NiS particles when the amount of Ni was increased.

Differences in the effect of vitamin E on nickel sulfide or nickel chloride-induced chromosomal aberrations in mammalian cells

Vitamin E (α-tocopherol succinate) pretreatment significantly inhibited formation of some but not all of the chromosomal aberrations induced by crystalline NiS particles but it did not affect the chromosome damage induced by NiCl 2. Crystalline NiS particles are phagocytized by cells in contrast to water-soluble NiCl 2 which enters the cells by a different mechanism. These and other previous studies suggest that the phagocytosis of crystalline NiS particles produces genetic damage as a consequence of oxygen radicals resulting from the irritant particle effect and also from the high intracellular levels of nickel ions dissolving from the endocytized particles.

Cluster ion formation under laser bombardment. Studies of recombination using isotope labeling

The analysis of natural abundance NiS particles mounted on an isotopically enriched /sup 34/S film using a transmission geometry laser microprobe mass spectrometer provides a means for observing recombination reactions in the laser-induced plasma. Sulfur-34 from the isotopically enriched thin film is extensively combining in the plasma with nickel from the NiS particle. The data suggest that this recombination phenomenon occurs to a similar extent for the three cluster ions NiS/sup +/, NiS/sub 2//sup +/, and Ni/sub 2/S/sup +/. One exception for the NiS/sub 2//sup +/ case is the /sup 58/NiS/sup 34/S/sup +/ ion, which has a much larger contribution to recombination by the /sup 34/S film. This probably reflects Ni attachment to /sup 34/S/sup 34/S dimers which are formed almost exclusively by contributions from the /sup 34/S film.

Chromosomal alterations in cell lines derived from mouse rhabdomyosarcomas induced by crystalline nickel sulfide.

Prior studies have shown a preferential decondensation (or fragmentation) of the heterochromatic long arm of the X chromosome of Chinese hamster ovary cells when treated with carcinogenic crystalline NiS particles (crNiS). In this report, we show that the heterochromatic regions of mouse chromosomes are also more frequently involved in aberrations than euchromatic regions, although the heterochromatin in mouse cells is restricted to centromeric regions. We also present the karyotypic analyses of four cell lines derived from tumors induced by leg muscle injections of crystalline nickel sulfide which have been analyzed to determine whether heterochromatic chromosomal regions are preferentially altered in the transformed genotypes. Common to all cell lines was the presence of minichromosomes, which are acrocentric chromosomes smaller than chromosome 19, normally the smallest chromosome of the mouse karyotype. The minichromosomes were present in a majority of cells of each line although the morphology of this extra chromosome varied significantly among the cell lines. C-banding revealed the presence of centromeric DNA and thus these minichromosomes may be the result of chromosome breaks at or near the centromere. In three of the four lines a marker chromosome could be identified as a rearrangement between two chromosomes. In the fourth cell line a rearranged chromosome was present in only 15% of the cells and was not studied in detail. One of the three major marker chromosomes resulted from a centromeric fusion of chromosome 4 while another appeared to be an interchange involving the centromere of chromosome 2 and possibly the telomeric region of chromosome 17.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathway of nickel uptake influences its interaction with heterochromatic DNA

Exposure of intact Chinese hamster ovary cells to water-soluble NiCl 2 and to particulate crystalline NiS induced a concentration-dependent incidence of chromosomal aberrations which included gaps, breaks, and exhanges. Exposure of cells to crystalline NiS particles caused a high incidence of chromatid exchanges and dicentrics and produced what appears to be an effect on the condensation state of the heterochromatic long arm of the X chromosome. Treatment of cells with NiCl 2 did not cause any significant effect on the long arm of the X chromosome, and there was a much lower incidence of the dicentric type of chromosomal aberrations compared to NiS. To examine whether the fragmentation/decondensation of the long arm of the X chromosome produced by crystalline NiS particles was due to a phagoctyic pathyway of uptake of NiS particles, cells were treated with NiCl 2-albumin complexes that had been encapsulated in liposomes. Although treatment of cells with NiCl 2-albumin complexes yielded higher intracellular nickel levels than were obtained by treatment of cells with NiCl 2, at comparable intracellular levels fragmentation/decondensation of the heterochromatic long arm of the X chromosome was observed when nickel (II) was delivered by way of a liposome but not when cells were treated with unencapsulated NiCl 2. Ionic nickel alone irrespective of its delivery mechanism exhibited some preference for heterochromatin, since there was a higher incidence of aberrations observed in the heterochromatic centromeric region of chromosomes. These observations suggest that the pathway of delivery of Ni 2+ from NiS particles may be responsible for a preferential interaction of this metal with heterochromatin leading to an effect on the condensation state/fragmentation of the heterochromatic long arm of the X chromosome.

Sequential events in the induction of transformation in cell culture by specific nickel compounds

Crystalline metal sulfides (i.e., Ni3S2, NiS, CoS, CuS) are potent inducers of transformation in Syrian Hamster Embryo cells while the respective amorphous compounds exhibit low transforming activity. Both crystalline and amorphous compounds are relatively water insoluble and when these particulate compounds (2-4 µm) are added to various types of cultured fibroblasts, they exhibit striking differences in their phagocytosis. These differences in uptake were directly related to their surface charge, since crystalline NiS had a negative surface charge (-27 mV, zeta potential) while amorphous NiS had a positively charged surface (+9 mV, zeta potential). Chemical reduction of amorphous NiS with LiA1H4 resulting in acquisition of a negative surface charge, enhanced phagocytosis and caused an incidence of transformation equalling that of crystalline NiS. Following phagocytosis of crystalline NiS, video time lapse microscopy and studies using(63)NiS show that the particles undergo cytoplasmic dissolution that appears to be mediated by lysosomal interaction. Later, the phagocytized NiS particles aggregate in the perinuclear region, their movement by saltation decreases and in some instances vacuoles form around the particles. Particle dissolution products then enter the nucleus and induce strand breaks in the DNA as determined by alkaline sucrose gradient and alkaline elution techniques. Cesium chloride gradient analysis also indicates that phagocytized NiS particles induce repair of DNA. Damage to DNA appears to be a very selective and sensitive action of all metal compounds with potential carcinogenic activity.

Application of a modified 203Hg binding assay for metallothionein

A sensitive and rapid method to estimate concentrations of functional metallothionein in small biological samples, based upon the acid stability of 203Hg binding and solubility of this protein in trichloroacetic acid is described. Sephadex G-10 minicolumns supported in centrifuge tubes afforded separation and quantitation of isotope bound metallothionein from unbound metal. Elution of metallothionein bound 203Hg was achieved by short term-low speed centrifugation that segregated chelator-ligand complex into the eluate while unbound ligand remained in the gel. A well characterized standard of pure metallothionein protein was utilized to verify the specificity and sensitivity of the modified assay. Metallothionein levels were estimated by 203Hg binding in extracts of wild type and cadmium resistant Chinese hamster ovary cells treated with maximum tolerable concentrations of CdCl 2. Similar separation methods demonstrated [ 35S]-cysteine incorporation into induced metallothionein. Additionally, induction of metallothionein was observed after treatment with particulate CdS but not crystalline NiS particles. These results demonstrate that the modified assay system is easily applied to serial measurement of metallothionein levels in multiple small biological samples.

Extracellular requirements for the endocytosis of carcinogenic crystalline nickel sulfide particles by facultative phagocytes

Various culture medium components were examined for their effect upon the phagocytosis of carcinogenic crystalline and non-carcinogenic amorphous NiS by cultured fibroblastic cells using both a visual and radioactive assay for phagocytosis. Crystalline NiS was phagocytosed by cells in a simple salts/glucose maintenance medium to an extent similar to that observed in complex culture medium fortified with 10% fetal bovine serum (FBS), suggesting that serum proteins and other components in complex culture medium exert little influence upon the uptake of these heavy metal particles. Phagocytosis of crystalline NiS was shown to be highly dependent upon Ca 2+since omission of Ca 2+ from the salts/glucose medium substantially reduced phagocytosis, while readdition of Ca 2+ stimulated uptake in a concentration-dependent manner. The uptake of the NiS particles was inhibited by trifluoperazine, a calmodulin antagonist, implicating intracellular Ca 2+ in this phagocytosis process. Since the opposite surface charge of crystalline and amorphous NiS has been related to their different phagocytic uptake by cells whose primary function is not phagocytosis (facultative phagocytes), these results show that the culture medium components do not modify the surface charge of these particles in a way that significantly influences their uptake.

Comparison of protein, RNA, and DNA binding and cell-cycle-specific growth inhibitory effects of nickel compounds in cultured cells

Crystalline NiS particles are potent inducers of morphological transformation and are actively phagocytosed by cells. Water-soluble nickel compounds are less potent, possibly because the total amount of nickel that enters cells is less, and its subcellular distribution differs in a number of ways from that following the entry of NiS in the form of an internalized particle. To further study this problem, we have examined the binding of 63Ni to DNA, RNA, and protein isolated from cultured Chinese hamster ovary cells treated with either crystalline 63NiS or 63NiCl 2. Treatment of cultured cells with 63NiS at 10 μg/ml for 3 days resulted in binding of nickel to DNA, RNA, or protein in the range of 1 μg of nickel bound per milligram macromolecule. However, similar treatment of cells with 63NiCl 2 at 10 μg/ml for 1 to 5 days resulted in approximately one to several orders of magnitude less nickel bound to DNA, RNA, and protein. In the case of 63NiCl 2 treatment, cellular proteins contained about 100 times more 63Ni bound than the respective RNA or DNA fractions. However, the protein fraction obtained from cells treated with crystalline NiS contained about 15 times more nickel bound than the same fraction isolated from cells that were similarly treated with 63NiCl 2. RNA or DNA had 300 to 2000 times more bound nickel following crystalline NiS treatment compared to cells treated similarly with NiCl 2. In contrast to the selective binding of 63NiCl 2 to protein, cultured cells treated with crystalline 63NiS had equivalent levels of nickel associated with RNA, DNA, and protein. Since the interaction of 63Ni with these macromolecules following crystalline 63NiS treatment was not due to the binding of the actual particles, the dissolution of intracellular 63NiS particles probably plays an important role in governing the distribution of 63Ni ions available for binding. The greater intracellular macromolecular binding of 63Ni resulting from treatment of cells with 63NiS compared to cultures similarly exposed to 63NiCl 2 paralleled the more potent effects of crystalline NiS in slowing and arresting cell proliferation. Crystalline NiS caused pronounced cell cycle specific blockage at a considerably lower concentration than was required for NiCl 2 to similarly arrest cell growth. Flow cytometry analysis showed that both compounds selectively blocked cell cycle progression in S phase (DNA synthetic stage). These results are suggestive of a common mechanism and site of toxicity inherent to both compounds and related to the cell growth phase during which DNA is replicated.

Cytoplasmic dissolution of phagocytized crystalline nickel sulfide particles: a prerequisite for nuclear uptake of nickel.

The intracellular fate of particulate crystalline alpha NiS, an inducer of neoplastic transformation which is readily phagocytized by cultured cells, was compared with that of particulate amorphous NiS, which does not have these properties. Amorphous and crystalline NiS both dissolve slowly in complete medium; phagocytized alpha NiS particles remain in the cytoplasm, where they dissolve more rapidly than extracellular particles. Thus the selective phagocytosis of alpha NiS accounts for both high intracellular particle accumulation and high levels of soluble Ni relative to the surrounding medium. Since phagocytized alpha NiS particles do not enter the nucleus, dissolution in the cytoplasm may represent an activation step in carcinogenesis, forming soluble Ni which diffuses into the nucleus. Dissolution products from phagocytized alpha NiS were detected in subcellular fractions isolated from treated cells; the highest levels were found in the nuclei, mitochondria, and lysosomes. That the Ni in the subcellular fractions was dissolved is suggested by the fact that dissolution products from phagocytized alpha NiS were detected in nuclei after centrifugation on sucrose pads, which substantially reduced contamination from cytoplasmic alpha NiS particles. Cytoplasmic dissolution of alpha NiS was enhanced by prior exposure of cells to the same compound. Loss of visible particles from cells was compared with loss of total Ni by use of alpha 63 NiS particles; the particles disappeared from almost half the cells during the first 2 d of treatment, while the total radioactivity associated with the cells and the total number of cells in the monolayer remained the same. The accelerated dissolution of alpha NiS after exposure to the same particles may be due to enhancement of lysosomal enzyme activity by particle phagocytosis. A 20-30% increase in intracellular acid phosphatase activity was observed after treatment with crystalline, but not amorphous, NiS, suggesting enhanced lysosomal activity.

Surface reduction of amorphous NiS particles potentiates their phagocytosis and subsequent induction of morphological transformation in Syrian hamster embryo cells

The incidence of morphological transformation following exposure of Syrian hamster embryo (SHE) cells to crystalline αNis particles was considerably greater than that following a similar exposure to amorphous NiS particles. These differences in potency were attributable to the selective phagocytosis of crystalline αNiS particles into cells, since untreated amorphous NiS particles were not readily taken up. Chemical reduction of the amorphous NiS particles' surface with LiAlH 4 resulted in an increase both in their phagocytic uptake by Chinese hamster ovary (CHO) cells and in their ability to induce transformation in SHE cells. The phagocytosis and transforming activity of crystalline αNiS particles was also enhanced by LiAlH 4 reduction. These results are consistent with previous observations showing that untreated crystalline NiS particles have a negative surface charge while amorphous NiS particles possess positively charged surfaces. These findings support the general hypothesis that the transforming activity of particulate metal compounds is proportional to their phagocytic uptake. Specifically, these observations show that the entry of metal sulfide particles into cells is related to their surface properties and, in particular, to the degree of negative charge on the surface microenvironment.