Katarzyna Zielińska

Electroless deposition of Ni-P-nano-ZrO2 composite coatings in the presence of various types of surfactants.

Ni-P-nano-ZrO(2) coatings were produced using the electroless deposition technique. To prevent agglomeration of zirconia nanoparticles in the plating bath, various surfactant additives (anionic, cationic, and nonionic) were used. The most stable bath was obtained with the addition of dodecyltrimethylammonium bromide (DTAB). The impact of this surfactant on the deposition rate, coating composition, and topography, as well as ζ potential of particles, was examined. Surface morphology and composition of the Ni-P-nano-ZrO(2) composite coatings was analyzed by various techniques including scanning electron microscopy (SEM) equipped with in situ energy-dispersive X-ray (EDX) spectroscopy. Coatings with a clearly greater amount of zirconia (21.88-22.10 wt.%) were obtained from baths containing DTAB in concentrations equal to or above its critical micelle concentration (cmc). For these surfactant concentrations, the reduction of Ni and P content was observed.

New approach to hydrophobic cyanine-type photosensitizer delivery using polymeric oil-cored nanocarriers: Hemolytic activity, in vitro cytotoxicity and localization in cancer cells

We report on encapsulation of cyanine IR-768 in oil-in-water (o/w) microemulsion, i.e. fabrication of templated polymeric nanocapsules as effective nanocarriers for a new generation of photodynamic agents suitable for photodynamic therapy (PDT). Discussed here are nanocapsule imaging, their in vitro biological evaluation, cyanine encapsulation potential, and the cellular localization of cyanine IR-768 delivered in the nanocapsules to MCF-7 cancer cells. Oil-cored poly(n-butyl cyanoacrylate) (PBCA) nanocapsules were prepared by interfacial polymerization in o/w microemulsions formed by the nonionics Tween 80 (polysorbate 80, polyoxyethylene 20 sorbitan monooleate), and Brij 96 (polyoxyethylene 10 oleyl ether). Iso-propyl myristate (IPM), ethyl oleate (EOl), iso-octane (IO), and oleic acid (OA) were used as the oil phases and iso-propanol (IP) and propylene glycol (PG) as the cosurfactants. Such o/w droplets, also containing hydrophobic IR-768 in the oil phase, were applied in the interfacial polymerization of n-butyl cyanoacrylate at 10 degrees C at pH 5.0. The isolated cyanine-loaded nanoparticles were visualized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), which proved their unimodal size distribution and spherical shape, with diameters dependent upon the monomer content and the template type. The entrapment efficiency of cyanine increased with increasing n-butyl cyanoacrylate concentration and varied from 65.7% to 91.7%. The results of in vitro erythrocyte hemolysis and the cell viability of breast cancer MCF-7 cells showed that the PBCA nanocapsules are quite safe carriers of IR-768 in the circulation, having a very low hemolytic potential and being non-toxic to the studied cells. Fluorescence microscopy visualized the cyanine intracellular distribution and, furthermore, demonstrated that PBCA-nanocarriers effectively delivered the IR-768 molecules to the MCF-7 doxorubicin-sensitive and -resistant cell lines. Photoirradiation of the cancer cells with entrapped photosensitizer decreased cell viability, demonstrating that this effect may be utilized in PDT.

Microstructure and structural transition in microemulsions stabilized by aldonamide-type surfactants.

Significant efforts were undertaken to characterize the microstructure and structural properties of water-in-oil (w/o), oil-in-water (o/w), and bicontinuous (bc) microemulsions composed of N-alkyl-N-methylgluconamides (n-alkyl = n-C(12)H(25), n-C(14)H(29), n-C(16)H(33)) and n-alcohols (ethanol, n-propanol, n-butanol) or iso-alcohols (iso-propanol, iso-butanol) as cosurfactants, as well as iso-octane and water. The internal structure of so created four-component system was elucidated by means of an analysis of isotropic area magnitudes in phase diagrams and conductivity measurements. Dynamic light scattering (DLS) measurements provided the microemulsion size and polydispersity. Polarity and viscosity of microemulsion microenvironment were acquired by means of electron paramagnetic resonance (EPR), UV-vis absorption spectroscopy (in the case of w/o droplets), and steady-state fluorescence (SSF) (in the case of o/w droplets). The results show that both the surfactant and the cosurfactant types affect the shape and extent of microemulsions. The size of droplets depends strongly on the type of examined microemulsion and the type of cosurfactant (linear or brunched) but is almost independent of the length of the surfactant alkyl chain. The size of microemulsion droplets ranges from 8.1 to 22.6 nm and from 3.7 to 14.3 nm respectively, for o/w and o/w microemulsions, making them good candidates for both template-based reactions and household components solubilizing media.

Biocompatible microemulsions of dicephalic aldonamide-type surfactants: Formulation, structure and temperature influence

The temperature effects upon microemulsion systems composed of dicephalic N-dodecyl-N,N-bis[(3-D-aldonylamido)propyl]amines C12-DX (gluconyl GA or lactobionyl LA)/iso-butanol/hydrophilic (diethylene glycol monoethyl ether) or hydrophobic (iso-octane) oils/water were investigated by evaluating isotropic area magnitudes in the pseudoternary phase diagrams, as well as droplet characteristics by electron paramagnetic resonance (EPR) and dynamic light scattering (DLS) spectroscopies at 25, 40 and 55 degrees C. We concluded that in the examined systems a cosurfactant, such as middle-chain alcohol, was needed to obtain large mesophase isotropic areas. The phase behavior and structure of the examined systems were temperature insensitive but they were intimately determined by the nature of the C12-DX and the polarity of the oil phase. By adjusting the nature of the oil, as well as the surfactant hydrophilicity, the performed isotropic systems containing low amounts of nonaggressive surfactant could be formulated successfully. Interfacial properties and the dynamic structure of the surfactant/cosurfactant monolayer were studied by the spin probe technique using the 16-doxylstearic acid methyl ester (16-DSE) as the appropriate probe. The polarity of the interface was not affected by temperature but the interface rigidity was dependent upon the nature of the surfactant and oil as well as on temperature. The size of the dispersed domains, evaluated by dynamic light scattering (DLS), was found to be a function of temperature, surfactant content and type of additives. The investigated o/w microemulsions (i.e., ranging from 3.0 to 8.8 nm) constituted promising templates for a variety of syntheses of nanostructures with small size and high-capacity solubilizing media.

Speciation Analysis of Aqueous Nanoparticulate Diclofenac Complexes by Solid-Phase Microextraction

The dynamic sorption of an organic compound by nanoparticles (NPs) is analyzed by solid-phase microextraction (SPME) for the example case of the pharmaceutical diclofenac in dispersions of impermeable (silica, SiO(2)) and permeable (bovine serum albumin, BSA) NPs. It is shown that only the protonated neutral form of diclofenac is accumulated in the solid phase, and hence this species governs the eventual partition equilibrium. On the other hand, the rate of the solid/water partition equilibration is enhanced in the presence of the sorbing nanoparticles of SiO(2) and BSA. This feature demonstrates that the NPs themselves do not enter the solid phase to any appreciable extent. The enhanced rate of attainment of equilibrium is due to a shuttle-type of contribution from the NP-species to the diffusive supply of diclofenac to the water/solid interface. For both types of nanoparticulate complexes, the rate constant for desorption (k(des)) of bound diclofenac was derived from the measured thermodynamic affinity constant and a diffusion-limited rate of adsorption. The computed k(des) values were found to be sufficiently high to render the NP-bound species labile on the effective time scale of SPME. In agreement with theoretical prediction, the experimental results are quantitatively described by fully labile behavior of the diclofenac/nanoparticle system and an ensuing accumulation rate controlled by the coupled diffusion of neutral, deprotonated, and NP-bound diclofenac species.

Photo-oxidative action in MCF-7 cancer cells induced by hydrophobic cyanines loaded in biodegradable microemulsion-templated nanocapsules.

Searching for photodynamic therapy-effective nanocarriers which enable a photosensitizer to be selectively delivered to tumor cells with enhanced bioavailability and diminished dark cytotoxicity is of current interest. We have employed a polymer-based nanoparticle approach to encapsulate the cyanine-type photosensitizer IR-780 in poly(n-butyl cyanoacrylate) (PBCA) nanocapsules. The latter were fabricated by interfacial polymerization in oil-in-water (o/w) microemulsions formed by dicephalic and gemini saccharide-derived surfactants. Nanocarriers were characterized by SEM, AFM and DLS. The efficiency of PBCA nanocapsules as a potential system of photosensitizer delivery to human breast cancer cells was established by dark and photocytotoxicity as the function of the cellular mitochondria. The photodynamic effect of cyanine IR-780 was determined by investigation of oxidative stress markers. The nanocapsules were the main focus of our studies to examine their cellular uptake and dark and photocytotoxicity as the function of the cellular mitochondria as well as oxidative stress markers (i.e., lipid peroxidation and protein damage) in MCF-7/WT cancer cells. The effects of encapsulated IR-780 were compared with those of native photosensitizer. The penetration of the nanocapsules into cancer cells was visualized by CLSM and their uptake was estimated by FACS analysis. Cyanine IR-780 delivered in PBCA nanocapsules to MCF-7/WT cells retains its sensitivity upon photoirradiation and it is regularly distributed in the cell cytoplasm. The intensity of the photosensitizer-generated oxidative stress depends on IR-780 release from the effective uptake of polymeric nanocapsules and seems to remain dependent upon the surfactant structure in o/w microemulsion-based templates applied to nanocapsule fabrication.

Partitioning of Humic Acids between Aqueous Solution and Hydrogel: Concentration Profiling of Humic Acids in Hydrogel Phases

The partitioning of the natural polyelectrolyte humic acid (HA) from an aqueous dispersion into a model biomimetic gel (alginate) and a synthetic polyacrylamide gel (PAAm) is explored. In both gels, the spatial distribution of HA in the gel body, as measured by confocal laser scanning microscopy, is markedly nonhomogeneous. A striking feature is the enhanced accumulation of HA in a thin film of thickness ca. 15 μm at the surface of the gel body, resulting in average local concentrations that are, for PAAm and alginate respectively, a factor of 10 and 4 greater than that in the bulk solution. The time dependence of accumulation in the surface film is predominantly controlled by the diffusive supply of HA from the aqueous medium, with a time constant on the order of 10(3) s for both gels. The concentration of HA within the bulk gel body differs significantly from that in the bulk aqueous medium: substantially higher for PAAm but much lower for alginate. The results are significant for understanding the nature and rate of sink/source functioning at permeable phases in contact with aqueous media, e.g., biofilms and gel-like layers at biological interfaces or employed in chemical speciation sensors.

Human Erythrocyte Hemolysis Induced by Bioinspired Sugar Surfactants

Hemolytic activity of single-head single-tail nonionic saccharide – derived surfactants (i.e., N-alkanoyl-N-methyllactitolamines and N-alkyl-N-methylaldonylamides) as well as dicephalic (i.e., (N-dodecyl-N,N-bis[(3-D-aldonylamido)propyl]amines; aldonyl = gluconyl and lactobionyl) and gemini structures (i.e., N,N’-bisdodecyl-N,N’-bis[(3-aldonylamide)propyl]ethylenediamines; aldonyl = gluconyl and lactobionyl) were examined and discussed in relation to both their critical micelle concentration (CMC) values, and structural aspects. The red blood cells lysis is found to depend on the surfactants structure and the hydrophobic tail length, as well as to correlate well with the CMC magnitudes.

Partitioning of Humic Acids between Aqueous Solution and Hydrogel. 2. Impact of Physicochemical Conditions

The effects of the physicochemical features of aqueous medium on the mode of partitioning of humic acids (HAs) into a model biomimetic gel (alginate) and a synthetic polyacrylamide gel (PAAm) were explored. Experiments were performed under conditions of different pH and ionic strength as well as in the presence or absence of complexing divalent metal ions. The amount of HA penetrating the gel phase was determined by measuring its natural fluorescence by confocal laser scanning microscopy. In both gel types, the accumulation of HA was spatially heterogeneous, with a much higher concentration located within a thin film at the gel surface. The thickness of the surface film (ca. 15 μm) was similar for both types of gel and practically independent of pH, ionic strength, and the presence of complexing divalent metal ions. The extent of HA accumulation was found to be dependent on the composition of the medium and on the type of gel. Significantly more HA was accumulated in PAAm gel as compared to that in alginate gel. In general, more HA was accumulated at lower background salt concentration levels. The distribution of different types of HA species in the gel body was linked to their behavior in the medium and the differences in physicochemical conditions inside the two phases.

Role of nanoparticles in analytical solid phase microextraction (SPME)

Environmental context Organic hydrophobic compounds are present in water in low concentrations, and they can be analysed by means of a preconcentration technique called solid phase microextraction. We investigate the role of sorbing nanoparticles in the solid phase microextraction analysis of organic compounds. Our results show that nanoparticles are capable of partitioning between water and the solid phase and aggregate at the interface leading, most probably, to substantial overestimation of the original sample concentration. Abstract Solid phase microextraction (SPME) is commonly used to measure the free concentration of fairly hydrophobic substances in aqueous media on the basis of their partitioning between sample solution and a solid phase. Here we study the role of nanoparticles that may sorb the analyte in the sample medium. As an example case, the solid phase poly(dimethylsiloxane) (PDMS) is exposed to an aqueous dispersion containing silica nanoparticles with 10-nm radius. Confocal laser microscopic data show that these SiO2 nanoparticles do enter the PDMS and partition between the sample solution and solid phase. Moreover, they form aggregates at the surface of the solid phase. The overall partitioning of the SiO2 nanoparticles in the aqueous sample–PDMS system is examined and potential effects on the SPME analysis of organic analytes are indicated.