Zdenka Bujňáková

Stability studies of As4S4 nanosuspension prepared by wet milling in Poloxamer 407

In this paper the stability of the arsenic sulfide (As4S4) nanosuspension prepared by wet milling in a circulation mill in the environment of copolymer Poloxamer 407 was studied. The obtained As4S4 particles in nanosuspension were of ∼ 100 nm in size. The influence of temperature and UV irradiation on the changes in physical and/or chemical properties was followed. Long-term stability was observed via particle size distribution and zeta potential measurements. Influence of UV irradiation was studied via UV-vis spectroscopy (UV-vis), photoluminicsence (PL) technique and Fourier transform infrared spectroscopy (FTIR) measurements. The best stability of the nanosuspension (24 weeks) was achieved when stored at 4°C and in the dark.

Arsenic Sulphide As4S4 Nanoparticles: Physico-Chemical Properties and Anticancer Effects

In this study, arsenic sulphide As4S4 nanoparticles have been prepared, by high-energy wet milling, in the presence of sodium dodecylsulphate, which acts a surfactant. Solid state properties of the nanoparticles were characterised by XRD, Raman scattering, specific surface area and particle size distribution. Changes in surface areas of the particles, in the 0.2 - 5.4 m2 g-1 range, and nanosize distributions, in the 100 - 250 nm range, characterise the surface and morphological properties of nanorealgar. Raman scattering revealed various species in the milled sample that indicate a disproportionate reaction (3As4S4 → 4As2S3 + 4As) occurring as a consequence of milling. Anticancer effects, of the milled species, were confirmed for the human multiple myeloma U266 and OPM1 cell lines. Dissolution experiments in simulated gastric fluid show a possibility for the application of the realgar nanoparticles as an oral dose in future arsenic drug cancer treatments.

Chalcogenide mechanochemistry in materials science: insight into synthesis and applications (a review)

The aim of this paper on recent development in chalcogenide mechanochemistry is to provide a comprehensive review of advances achieved in the field of mechanochemical synthesis of nanocrystalline binary, ternary and quaternary chalcogenides and their nanocomposites. The synthetic approaches from elements and compounds are reviewed. The current focus of mechanochemical synthesis is on materials with potential utilization in future. In order to demonstrate the suitability of mechanochemically prepared chalcogenides for various applications, the concrete examples of the utilization of these materials in materials engineering, bioimaging and cancer treatment are provided. The possibility of scaling for industrial applications is also reviewed. The simplification of the synthesis processes with their reproducibility and easy way of operation, ecological safety and the product extraordinariness (nanoscale aspects) emphasizes the suitability of mechanochemistry application in chalcogenide synthesis.

Ultrafast mechanochemical synthesis of copper sulfides

Covellite, CuS and chalcocite, Cu2S were prepared within a few seconds by ball milling of the elemental precursors. The morphology of the used copper, related to its preparation method, was found to be the key factor for the ultrafast reaction. The explosive character of the reaction was monitored by the gas pressure changes in the milling vessel and the reaction progress was pursued by X-ray diffraction analysis and Soxhlets extraction. The local temperature at the contact site between the milling media and the milled mixture at the time of explosion was calculated as 950 °C for CuS and 700 °C for Cu2S. The mean crystallite size of the prepared products was 15 nm for CuS and 65 nm for Cu2S.

Mechanochemical approach for the capping of mixed core CdS/ZnS nanocrystals: Elimination of cadmium toxicity

The wet mechanochemical procedure for the capping of the CdS and CdS/ZnS quantum dot nanocrystals is reported. l-cysteine and polyvinylpyrrolidone (PVP) were used as capping agents. When using l-cysteine, the dissolution of cadmium(II) was almost none for CdS/ZnS nanocrystals. Moreover, prepared CdS- and CdS/ZnS-cysteine nanosuspensions exhibited unimodal particle size distributions with very good stability, which was further supported by the zeta potential measurements. The Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy showed the successful embedment of cysteine into the structure of the nanocrystals. Additionally, the optical properties were examined, and the results showed that the cysteine nanosuspension has promising fluorescence properties. On the other hand, PVP was not determined to be a very suitable capping agent for the present system. In this case, the release of cadmium(II) was higher in comparison to the l-cysteine capped samples. The nanosuspensions were successfully used for in vitro studies on selected cancer cell lines. Using fluorescence microscopy, it was evidenced that the nanocrystals enter the cell and that they can serve as imaging agents in biomedical applications.

Positron annihilation lifetime study of polyvinylpyrrolidone for nanoparticle-stabilizing pharmaceuticals.

Positron annihilation lifetime spectroscopy was applied to characterize free-volume structure of polyvinylpyrrolidone used as nonionic stabilizer in the production of many nanocomposite pharmaceuticals. The polymer samples with an average molecular weight of 40,000 g mol(-1) were pelletized in a single-punch tableting machine under an applied pressure of 0.7 GPa. Strong mixing in channels of positron and positronium trapping were revealed in the polyvinylpyrrolidone pellets. The positron lifetime spectra accumulated under normal measuring statistics were analysed in terms of unconstrained three- and four-term decomposition, the latter being also realized under fixed 0.125 ns lifetime proper to para-positronium self-annihilation in a vacuum. It was shown that average positron lifetime extracted from each decomposition was primary defined by long-lived ortho-positronium component. The positron lifetime spectra treated within unconstrained three-term fitting were in obvious preference, giving third positron lifetime dominated by ortho-positronium pick-off annihilation in a polymer matrix. This fitting procedure was most meaningful, when analysing expected positron trapping sites in polyvinylpyrrolidone-stabilized nanocomposite pharmaceuticals.

Microstructure Hierarchical Model of Competitive e+-Ps Trapping in Nanostructurized Substances: from Nanoparticle-Uniform to Nanoparticle-Biased systems

Microstructure hierarchical model considering the free-volume elements at the level of interacting crystallites (non-spherical approximation) and the agglomerates of these crystallites (spherical approximation) was developed to describe free-volume evolution in mechanochemically milled As4S4/ZnS composites employing positron annihilation spectroscopy in a lifetime measuring mode. Positron lifetime spectra were reconstructed from unconstrained three-term decomposition procedure and further subjected to parameterization using x3-x2-coupling decomposition algorithm. Intrinsic inhomogeneities due to coarse-grained As4S4 and fine-grained ZnS nanoparticles were adequately described in terms of substitution trapping in positron and positronium (Ps) (bound positron-electron) states due to interfacial triple junctions between contacting particles and own free-volume defects in boundary compounds. Compositionally dependent nanostructurization in As4S4/ZnS nanocomposite system was imagined as conversion from o-Ps trapping sites to positron traps. The calculated trapping parameters that were shown could be useful to characterize adequately the nanospace filling in As4S4/ZnS composites.

Preparation, properties and anticancer effects of mixed As4S4/ZnS nanoparticles capped by Poloxamer 407

Arsenic sulfide compounds have a long history of application in a traditional medicine. In recent years, realgar has been studied as a promising drug in cancer treatment. In this study, the arsenic sulfide (As4S4) nanoparticles combined with zinc sulfide (ZnS) ones in different molar ratio have been prepared by a simple mechanochemical route in a planetary mill. The successful synthesis and structural properties were confirmed and followed via X-ray diffraction and high-resolution transmission electron microscopy measurements. The morphology of the particles was studied via scanning electron microscopy and transmission electron microscopy methods and the presence of nanocrystallites was verified. For biological tests, the prepared As4S4/ZnS nanoparticles were further milled in a circulation mill in a water solution of Poloxamer 407 (0.5wt%), in order to cover the particles with this biocompatible copolymer and to obtain stable nanosuspensions with unimodal distribution. The average size of the particles in the nanosuspensions (~120nm) was determined by photon cross-correlation spectroscopy method. Stability of the nanosuspensions was determined via particle size distribution and zeta potential measurements, confirming no physico-chemical changes for several months. Interestingly, with the increasing amount of ZnS in the sample, the stability was improved. The anti-cancer effects were tested on two melanoma cell lines, A375 and Bowes, with promising results, confirming increased efficiency of the samples containing both As4S4 and ZnS nanocrystals.

Mechanochemical synthesis and in vitro studies of chitosan-coated InAs/ZnS mixed nanocrystals

In this paper, InAs/ZnS mixed nanocrystals were synthesized by dry high-energy milling approach in the first step. The obtained nanocrystals were characterized from structural point of view by X-ray diffraction analysis and Raman spectroscopy, and from the morphological point of view by scanning electron microscopy. In the next step, the nanocrystals were subjected to wet ultra-fine milling in order to obtain a nanosuspension of chitosan-coated InAs/ZnS nanocrystals with bio-imaging properties. The stability of the nanosuspension was examined by zeta potential and particle size distribution measurements. The prepared nanosuspension was stable with high values of zeta potential. Its optical properties were also studied using UV–Vis and PL spectroscopies. The determined fluorescent properties confirming the potential in bio-imaging applications were verified on cancer cell lines Caco-2, HCT116, HeLa, and MCF7.

Zinc oxide nanoparticles phytotoxicity on halophyte from genus Salicornia

This study deals with the effect of zinc oxide nanoparticles (ZnO NPs) on halophyte from the genus Salicornia. The presence of ZnO nanoparticles (100 and 1000 mg/L) in the solid culture medium resulted in the negative effects on plant growth in the concentration-dependent manner. The shoot length of plant cultivated with 1000 mg/L ZnO NPs decreased by more than 50% compared to non-treated plants. The phytotoxicity was associated with the release of free zinc(II) ions, which was determined by atomic absorption spectroscopy and fluorescence microscopy. Another mechanism involved in ZnO NPs phytotoxicity was closely connected with generation of reactive oxygen species (ROS), which was accompanied by changes in activities and amounts of antioxidant enzymes. Histochemical evaluation showed that ROS were present also in the shoot of plant, which was not in direct contact with NPs. The reduction of activity and amount of antioxidant enzymes such as gamma-ESC, GR, SOD, PER, APX and higher concentration of ROS lead to lipid peroxidation, the latter being almost 3 times higher for the plant treated with 1000 mg/L NPs compared to control. The misbalance in zinc homeostasis and creation of ROS with subsequent oxidative stress led to the initiation of processes of programmed cell death, which was demonstrated by the loss of mitochondrial potential and increase of intracellular calcium (II) ions. Despite halophytes exhibit higher stress resistance than glycophytes, they are prone to negative changes if incubated in the environment containing ZnO nanoparticles.