Nm For Particles Research Articles

Effect of Particle Size of Nano-Oxides on Color Stability and Mechanical Properties of Maxillofacial Silicone Elastomers: An In Vitro Study.

To evaluate the physical and mechanical properties of maxillofacial silicone elastomers following the incorporation of a specific particle size and concentration of nano-titanium dioxide (TiO2) and nano-zinc oxide (ZnO). Nano-TiO2 and nano-ZnO of 20-nm and 40-nm particle sizes and in 1% and 2% concentrations were chosen. Silicone elastomer samples were prepared according to the manufacturer's recommendations. The nano-oxides were incorporated via hand spatulation. The samples were subsequently tested for hardness and color stability and were then subjected to aging in an aging chamber for 1,008 hours, following which they were again evaluated for hardness, color stability, and surface roughness. A significant change was noted in the physical and mechanical properties post-aging in all the groups. The samples with nano-TiO2 of 40-nm particle size/2% concentration had the highest hardness, while color stability and surface roughness were higher in samples with nano-TiO2 of 20-nm particle size/1% and 2% concentrations, respectively. It can be concluded that 20-nm nano-TiO2 particles best maintain the ideal properties of maxillofacial silicone elastomers and can potentially be used as alternative opacifiers when mixed with A-2186 maxillofacial silicone elastomers.

Towards the molecular architecture of the peroxisomal receptor docking complex

Import of yeast peroxisomal matrix proteins is initiated by cytosolic receptors, which specifically recognize and bind the respective cargo proteins. At the peroxisomal membrane, the cargo-loaded receptor interacts with the docking protein Pex14p that is tightly associated with Pex17p. Previous data suggest that this interaction triggers the formation of an import pore for further translocation of the cargo. The mechanistic principles, however, are unclear, mainly because structures of higher-order assemblies are still lacking. Here, using an integrative approach, we provide the structural characterization of the major components of the peroxisomal docking complex Pex14p/Pex17p, in a native bilayer environment, and reveal its subunit organization. Our data show that three copies of Pex14p and a single copy of Pex17p assemble to form a 20-nm rod-like particle. The different subunits are arranged in a parallel manner, showing interactions along their complete sequences and providing receptor binding sites on both membrane sides. The long rod facing the cytosol is mainly formed by the predicted coiled-coil domains of Pex14p and Pex17p, possibly providing the necessary structural support for the formation of the import pore. Further implications of Pex14p/Pex17p for formation of the peroxisomal translocon are discussed.

Terahertz plasmonic nanotrapping with graphene coaxial apertures

Noninvasive and noncontact approaches of trapping nanoscale biospecimens have gained extensive interest due to their biological and nanotechnological applications. Here, we have proposed a tunable plasmonic nanotweezers that works in the terahertz region, and numerically demonstrated that a deep trapping potential well for a nanoscale dielectric nanoparticle can be generated through confining and enhancing the submillimeter-scale terahertz waves into a nanogap of graphene coaxial apertures. In addition, we further show the THz plasmonic nanotweezers is capable of stable trapping a 20-nm particle with a refractive index of 1.5 while the incident waves intensity is as low as $3.5\phantom{\rule{0.16em}{0ex}}\mathrm{mW}/\ensuremath{\mu}{\mathrm{m}}^{2}$ and the photon energy is below 20 meV. It is expected that the proposed THz nanotweezers could trap and manipulate nanoscale living biospecimens via a noninvasive approach.

Biosynthesis of zinc oxide nanoparticles using leaf extracts of Alchornea laxiflora and its tyrosinase inhibition and catalytic studies

Zinc oxide nanoparticles (ZnO-NPs) were synthesized using a simple, low cost and safe method involving aqueous leaf extracts of Alchornea laxiflora and a zinc precursor salt. The nanoparticles were characterized by ultraviolet-visible (UV–vis), Fourier transform (FT-IR) spectroscopy, Energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Scanning electron microscope (SEM). They were evaluated for their potentials as tyrosinase inhibitors and as catalysts in the degradation of Congo red dye. The UV–vis spectra gave characteristic surface Plasmon bands within the range 276−456 nm. The band gap energies of the ZnO-NPs were of the range, 2.50–3.67 ev. The SEM results showed average sizes of 29 nm and 38 nm for particles obtained using 1 mL and 2 mL of the plant extracts respectively. EDX plot showed the elemental compositions of the nanoparticles with zinc and oxygen being pronounced. The ZnO nanoparticles exhibited good photocatalytic efficiency of 87 % degradation of Congo red (CR) dye molecules in 60 min, They also showed good anti-tyrosinase ability with an IC50 of 66.28 μg/mL. Overall the biogenic ZnO nanoparticles are promising materials for dual applications as photocatalysts in the degradation of Congo red dye and as tyrosinase inhibitors.

Novel bimetallic nano particles for sorption of mercury (II) from drinking water: Adsorption experiment and computational studies

The current study proposes fabrication of novel manganese and copper (Mn/Cu) based bimetallic nano particles (NPs) for adsorptive removal of mercury (Hg) ions from aqueous media and examines computational models for adsorption. The Mn/Cu bimetallic NPs were characterized for Atomic Force Microscope (AFM), Energy Dispersive X-rays Spectroscopy (EDS), X-Ray Diffraction (XRD) and Dynamic Light Scattering (DLS) techniques to investigate morphology, surface elemental composition and particle size analysis. Sorption of Hg was carried out using batch experiments in triplicate and residual Hg concentration after sorption was determined using cold vapor atomic absorption spectrometer (CV-AAS). The effect of various parameters such as pH, mass of nano particles, Hg concentration and contact time were optimized. Maximum removal efficiency was 95 % with 2.89 % RSD and maximum adsorption capacity (Q max) observed was 400 mg g-1. AFM images well separated morphology and mean grain size of 450 ± 50 nm of particles, DLS measured average particles size as 110 nm while XRD pattern and EDS results showed successful adsorption of Hg on Mn/Cu bimetallic surface. Ab initio based computational models for different geometries were optimized using semi empirical method through Gaussian software. Computational molecular models were optimized for structures before and after Hg sorption and important physical parameters such as electron spin, Root mean square (RMS) gradient, Adsorption energy, Mulliken charge density (Q) and bond lengths (BL) before and after adsorption were computed. It was concluded that Langmuir adsorption isotherm was favorable for this study and interaction of Hg was more favorable with Mn than Cu because of less adsorption energy (-112.48 eV) and stronger bond formation between them having bond length of 1.6433 Å.

Bigger or Smaller? Size and Loading Effects on Nanoparticle Uptake Efficiency in the Nasal Mucosa.

PLGA nanoparticles hold great promise for nasal administration, but only with careful design will efficient, effective, and safe delivery systems be developed. To better understand the size dependence of nasal epithelial uptake, PLGA nanoparticles (60nm or 125nm) loaded with Nile Red were prepared, and their uptake into excised sections of bovine nasal respiratory or olfactory mucosa was measured for 30 or 60min. The epithelial layer and the submucosal tissues were separated, and the amount of Nile Red was used to calculate the number of nanoparticles in each tissue region. Both particle sizes were able to be internalized into the nasal tissues in as little as 30min, but their total uptake represented less than 5% of the nanoparticles available. Nanoparticles were present both in the epithelial cells and in the submucosal tissues, and greater numbers of the 60-nm particles were present in the submucosa than the epithelium, while greater numbers of the 125-nm particles remained in the epithelial cell layer. The amount of Nile Red recovered from the mucosal tissues after exposure to 125-nm nanoparticles was at least 2-fold greater than from the 60-nm nanoparticles, however, due to the higher (~ 9-fold) loadingcapacity of the larger particles. The greater mass transfer of the Nile Red from the larger particles suggests that it may not be necessary to develop small nanoparticulate delivery systems for efficient drug delivery via the nasal mucosa. Well-designed nanoparticles with diameters > 100nm show good uptake into the nasal epithelium and are capable of transfer to the submucosal tissues, near the location of significant populations of blood and lymphatic vessels. Graphical abstract.

Lauroylated Histidine-Enriched S413-PV Peptide as an Efficient Gene Silencing Mediator in Cancer Cells.

This study aimed to endow the cell-penetrating peptide (CPP) S413-PV with adequate features towards a safe and effective application in cancer gene therapy. Peptide/siRNA complexes were prepared with two new derivatives of the CPP S413-PV, which combine a lauroyl group attached to the N- or C-terminus with a histidine-enrichment in the N-terminus of the S413-PV peptide, being named C12-H5-S413-PV and H5-S413-PV-C12, respectively. Physicochemical characterization of siRNA complexes was performed and their cytotoxicity and efficiency to mediate siRNA delivery and gene silencing in cancer cells were assessed in the absence and presence of serum. Peptide/siRNA complexes prepared with the C12-H5-S413-PV derivative showed a nanoscale (ca. 100nm) particle size, as revealed by TEM, and efficiently mediated gene silencing (37%) in human U87 glioblastoma cells in the presence of 30% serum. In addition, the new C12-H5-S413-PV-based siRNA delivery system efficiently downregulated stearoyl-CoA desaturase-1, a key-enzyme of lipid metabolism overexpressed in cancer, which resulted in a significant decrease in the viability of U87 cells. Importantly, these complexes were able to spare healthy human astrocytes. These encouraging results pave the way for a potential application of the C12-H5-S413-PV peptide as a promising tool in cancer gene therapy.

Airborne Release Fractions from Surrogate Nuclear Waste Fires Containing Lanthanide Nitrates and Depleted Uranium Nitrate in 30% Tributyl Phosphate in Kerosene

Airborne contaminants from fires containing nuclear waste represent significant health hazards and shape the design and operation of nuclear facilities. Much of the data used to formulate DOE-HDBK-3010-94, “Airborne Release Fractions/Rates and Respirable Fractions for Nonreactor Nuclear Facilities,” from the U.S. Department of Energy, were taken over 40 years ago. The objectives of this study were to reproduce experiments from Pacific Northwest Laboratories conducted in June 1973 employing current aerosol measurement methods and instrumentation, develop an enhanced understanding of particulate formation and transport from fires containing nuclear waste, and provide modeling and experimental capabilities for updating current standards and practices in nuclear facilities. A special chamber was designed to conduct small fires containing 25 mL of flammable waste containing lutetium nitrate, ytterbium nitrate, or depleted uranium nitrate. Carbon soot aerosols showed aggregates of primary particles ranging from 20 to 60 nm in diameter. In scanning electron microscopy, ~200-nm spheroidal particles were also observed dispersed among the fractal aggregates. The 200-nm spherical particles were composed of metal phosphates. Airborne release fractions (ARFs) were characterized by leaching filter deposits and quantifying metal concentrations with mass spectrometry. The average mass-based ARF for 238U experiments was 1.0 × 10−3 with a standard deviation of 7.5 × 10−4. For the original experiments, DOE-HDBK-3010-94 states, “Uranium ARFs range from 2 × 10−4 to 3 × 10−3, an uncertainty of approximately an order of magnitude.” Thus, current measurements were consistent with DOE-HDBK-3010-94 values. ARF values for lutetium and ytterbium were approximately one to two orders of magnitude lower than 238U. Metal nitrate solubility may have varied with elemental composition and temperature, thereby affecting ARF values for uranium surrogates (Yb and Lu). In addition to ARF data, solution boiling temperatures and evaporation rates can also be deduced from experimental data.

Assessment of 10-nm Particle Number (PN) Portable Emissions Measurement Systems (PEMS) for Future Regulations.

The particle number (PN) emissions of vehicles equipped with particulate filters are low. However, there are technologies that can have high PN levels, especially below the currently lower regulated particle size of 23 nm. Sub-23-nm particles are also considered at least as dangerous as the larger ultrafine particles. For this reason, the European Union (EU) is planning to regulate particles down to 10 nm. In this study we compared prototype portable emission measurement systems (PEMS) and reference laboratory systems measuring from 10 nm. The tests included cycles and constant speeds, using vehicles fuelled with diesel, gasoline or liquefied petroleum gas (LPG). The results showed that the PEMS were within ±40% of the reference systems connected to the tailpipe and the dilution tunnel. Based on the positive findings and the detection efficiencies of the prototype instruments, a proposal for the technical specifications for the future regulation was drafted.

Mosquito Cell-Derived Japanese Encephalitis Virus-Like Particles Induce Specific Humoral and Cellular Immune Responses in Mice.

The Japanese encephalitis virus (JEV) is the major cause of an acute encephalitis syndrome in many Asian countries, despite the fact that an effective vaccine has been developed. Virus-like particles (VLPs) are self-assembled multi-subunit protein structures which possess specific epitope antigenicities related to corresponding native viruses. These properties mean that VLPs are considered safe antigens that can be used in clinical applications. In this study, we developed a novel baculovirus/mosquito (BacMos) expression system which potentially enables the scalable production of JEV genotype III (GIII) VLPs (which are secreted from mosquito cells). The mosquito-cell-derived JEV VLPs comprised 30-nm spherical particles as well as precursor membrane protein (prM) and envelope (E) proteins with densities that ranged from 30% to 55% across a sucrose gradient. We used IgM antibody-capture enzyme-linked immunosorbent assays to assess the resemblance between VLPs and authentic virions and thereby characterized the epitope specific antigenicity of VLPs. VLP immunization was found to elicit a specific immune response toward a balanced IgG2a/IgG1 ratio. This response effectively neutralized both JEV GI and GIII and elicited a mixed Th1/Th2 response in mice. This study supports the development of mosquito cell-derived JEV VLPs to serve as candidate vaccines against JEV.

Small silica nanoparticles transiently modulate the intestinal permeability by actin cytoskeleton disruption in both Caco-2 and Caco-2/HT29-MTX models.

Amorphous silica nanoparticles are widely used as pharmaceutical excipients and food additive (E551). Despite the potential human health risks of mineral nanoparticles, very few data regarding their oral toxicity are currently available. This study aims to evaluate and to understand the interactions of silica particles at 1 and 10mgmL-1 with the intestinal barrier using a Caco-2 monolayer and a Caco-2/HT29-MTX co-culture. A size- and concentration-dependent reversible increase of the paracellular permeability is identified after a short-term exposure to silica nanoparticles. Nanoparticles of 30nm induce the highest transepithelial electrical resistance drop whereas no effect is observed with 200nm particles. Additive E551 affect the Caco-2 monolayer permeability. Mucus layer reduces the permeability modulation by limiting the cellular uptake of silica. After nanoparticle exposure, tight junction expression including Zonula occludens 1 (ZO-1) and Claudin 2 is not affected, whereas the actin cytoskeleton disruption of enterocytes and the widening of ZO-1 staining bands are observed. A complete permeability recovery is concomitant with the de novo filament actin assembly and the reduction of ZO-1 bands. These findings suggest the paracellular modulation by small silica particles is directly correlated to the alteration of the ZO-actin binding strongly involved in the stability of the tight junction network.

Simulation investigation of effect on nanoparticles discharging pattern of a car caused by a following one on a typical city road

Vehicle emission is supposed to contribute a great part to the urban air pollution in China, and many relative studies were carried out on a macro base at “city valley” scale. This article, on the “micro” individual scale otherwise, attempts to explore the fine particles’ spreading process after leaving the tailpipe of a typical car equipped with the inner-combustion engine in city main road through 3D CFD simulation. two geometries of typical cars driving in typical city road were built up with detailed structures: one is one car driving on the main city street and the other is two cars, one followed the former established car, all with a driving speed of 40 km/h. Eulerian multiphase model is adopted to describe the dynamics of the multiphase: air, particles in 10nm diameter, and particles in 70nm diameter. The simulation results show that the diffusion process of 70nm particles is mainly governed by gravity, more than 80% of which concentrate within the region behind the car with a volume of 4.0m in length, 3.0m in height, and 2.0m in horizontal width along the centreline of tailpipe, while the 10nm particles exhibit a wider and more random distribution pattern, it spreads throughout the simulation volume with noticeable volume fraction: above, beneath, and behind the driving car, the high volume fraction regions mostly occur within a volume of 12.0m in length, 4.0m in height, and 4.0m in width associated with the tailpipe. The followed car causes a “compressing and lifting” effect, it is found that the high-volume fraction regions of particles are compressed to, in one hand, move around to the bodies of the two cars, and the other hand move towards the sides of the road. The particles in 70nm diameter are less affected by the followed car than that 10nm, especially the lifting effect of high-volume fraction regions of 10nm particles. This suggests some nonconventional management measures should be taken to control the urban air pollution of vehicles.

Light-Harvesting Nanoparticle Probes for FRET-Based Detection of Oligonucleotides with Single-Molecule Sensitivity.

Controlling the emission of bright luminescent nanoparticles by a single molecular recognition event remains a challenge in the design of ultrasensitive probes for biomolecules. Herein, we developed 20-nm light-harvesting nanoantenna particles, built of a tailor-made hydrophobic charged polymer poly(ethyl methacrylate-co-methacrylic acid), encapsulating circa 1000 strongly coupled and highly emissive rhodamine dyes with their bulky counterion. Being 87-fold brighter than quantum dots QDots 605 in single-particle microscopy (with 550-nm excitation), these DNA-functionalized nanoparticles exhibit over 50 % total FRET efficiency to a single hybridized FRET acceptor, a highly photostable dye (ATTO665), leading to circa 250-fold signal amplification. The obtained FRET nanoprobes enable single-molecule detection of short DNA and RNA sequences, encoding a cancer marker (survivin), and imaging single hybridization events by an epi-fluorescence microscope with ultralow excitation irradiance close to that of ambient sunlight.

Use of a Glycan Library Reveals a New Model for Enteric Virus Oligosaccharide Binding and Virion Stabilization.

Enteric viruses infect the gastrointestinal tract, and bacteria can promote replication and transmission of several enteric viruses. Viruses can be inactivated by exposure to heat or bleach, but poliovirus, coxsackievirus B3, and reovirus can be stabilized by bacteria or bacterial polysaccharides, limiting inactivation and aiding transmission. We previously demonstrated that certain N-acetylglucosamine (GlcNAc)-containing polysaccharides can stabilize poliovirus. However, the detailed virus-glycan binding specificity and glycan chain length requirements, and thus the mechanism of virion stabilization, have been unclear. A previous limitation was our lack of defined-length glycans to probe mechanisms and consequences of virus-glycan interactions. Here, we generated a panel of polysaccharides and oligosaccharides to determine the properties required for binding and stabilization of poliovirus. Poliovirus virions are nonenveloped icosahedral 30-nm particles with 60 copies of each of four capsid proteins, VP1 to VP4. VP1 surrounds the 5-fold axis, and our past work indicates that this region likely contains the glycan binding site. We found that relatively short GlcNAc oligosaccharides, such as a six-unit GlcNAc oligomer, can bind poliovirus but fail to enhance virion stability. Virion stabilization required binding of long GlcNAc polymers of greater than 20 units. Our data suggest a model where GlcNAc polymers of greater than 20 units bind and bridge adjacent 5-fold axes, thus aiding capsid rigidity and stability. This study provides a deeper understanding of enteric virus-bacterial glycan interactions, which are important for virion environmental stability and transmission.IMPORTANCE Enteric viruses are transmitted through the fecal-oral route, but how enteric viruses survive in the environment is unclear. Previously, we found that bacterial polysaccharides enhance poliovirus stability against heat or bleach inactivation, but the specific molecular requirements have been unknown. Here, we showed that certain short-chain oligosaccharides can bind to poliovirus but do not increase virion stability. Long-chain polysaccharides bind and may bridge adjacent sites on the viral surface, thus increasing capsid rigidity and stability. This work defines the unique interactions of poliovirus and glycans, which provides insight into virion environmental stability and transmission.

Synthesis and crystal structures of Pb(II) dithiocarbamates complexes: precursors for PbS nanophotocatalyst

ABSTRACT Pb(II) complexes of N-ethyl-N-phenyl dithiocarbamate [Pb(EtPhdtc)2] and N-benzylmethyl dithiocarbamate [Pb(BzyMedtc)2] were synthesized and characterized by single crystal X-ray crystallography. The molecular structures of compounds reveal a distorted tetrahedral geometry around the Pb(II) ions. [Pb(EtPhdtc)2] crystalized as a dimeric structure with Pb … Pb and Pb … S interactions while [Pb(BzyMedtc)2] crystallized as monomeric complex with weak C–H interactions. Thermogravimetric analysis of the Pb(II) complexes shows they decomposed to give lead sulphide (PbS). The complexes were thermolysed in oleic acid (OA) at 120°C, 160°C and 200°C to study the influence of temperature on OA capped PbS nanoparticles. Powder X-ray diffraction patterns confirms that the as-prepared PbS are cubic rock salt crystalline phase of PbS. High resolution transmission electron microscopy (HRTEM) micrographs crystallite average size of 2.64 nm for particles prepared at 120°C, 4.12 nm for particles prepared at 160°C, and 1.93 nm for particles prepared at 200°C from [Pb(EtPhdtc)2]. The average crystallite sizes of PbS nanoparticles obtained from [Pb(BzyMedtc)2] are 6.61 nm at 120°C, 13.88 nm at 160°C, and 10.82 nm at 200°C. The as-prepared PbS nanocrystals were used as photocatalyst for the degradation of methylene blue with the highest degradation efficiency of 73.89% recorded for OAPbS1a.

Synthesis and characterisation of magnetite nanoparticles using gelatin and starch as capping agents.

Nanoparticles of magnetite passivated with gelatin and starch were synthesised using a co-precipitation technique. The nanoparticles were characterised using ultraviolet-visible (UV-vis), dynamic light scattering (DLS), Zeta potential, transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The UV-vis spectra showed characteristic surface plasmon resonance of magnetite nanoparticles. The DLS results showed the nanoparticles to have average hydrodynamic diameters of 138 ± 2 and 283 ± 21 nm for particles passivated with gelatin and starch, respectively. The stability in a colloidal solution was greater in nanoparticles passivated with gelatin than nanoparticles obtained with starch, as can be seen by their Zeta potential value (-31 ± 2 and -16 ± 0.5 mV, respectively). According to the TEM evaluation, the use of gelatin allowed to obtain nanoparticles with a spherical morphology and an average size of 10 ± 2 nm. However, when using starch the nanoparticles exhibited diverse morphologies with an average size of 25 ± 7 nm. The XRD results confirmed the crystalline structure of the samples, which showed crystallite sizes of 14.90 and 24.43 nm for nanoparticles passivated with gelatin and starch, respectively. FTIR analysis proved the establishment of interactions between functional groups of biopolymers and magnetite nanoparticles.

Electron Microscopic Detection of Single Membrane Proteins by a Specific Chemical Labeling.

SummaryElectron microscopy (EM) is a technology that enables visualization of single proteins at a nanometer resolution. However, current protein analysis by EM mainly relies on immunolabeling with gold-particle-conjugated antibodies, which is compromised by large size of antibody, precluding precise detection of protein location in biological samples. Here, we develop a specific chemical labeling method for EM detection of proteins at single-molecular level. Rational design of α-helical peptide tag and probe structure provided a complementary reaction pair that enabled specific cysteine conjugation of the tag. The developed chemical labeling with gold-nanoparticle-conjugated probe showed significantly higher labeling efficiency and detectability of high-density clusters of tag-fused G protein-coupled receptors in freeze-fracture replicas compared with immunogold labeling. Furthermore, in ultrathin sections, the spatial resolution of the chemical labeling was significantly higher than that of antibody-mediated labeling. These results demonstrate substantial advantages of the chemical labeling approach for single protein visualization by EM.

Oxalate oxidase from Abortiporus biennis – protein localisation and gene sequence analysis

We have described for the first time the localisation of oxalate oxidase (OXO, EC 1.2.3.4) in Abortiporus biennis cells, using histochemical and immunochemical methods coupled with transmission electron microscopy. Rabbit anti-oxalate oxidase immunoglobulins with anti-rabbit secondary antibody conjugated with 10-nm gold particles were used. Moreover, the formation of electron dense precipitation of reaction of diaminobenzidine (DAB) with horseradish peroxidase (HRP) for histochemical localisation of the enzyme was found. OXO was localised close to the membranous structures of the cell membranes, in membranous vesicles located close to the outer cell membrane, and vacuolar membranes surrounding vacuoles. The positive immunoreaction to OXO was also intense in cell wall areas. Moreover, we proved that gene coding for OXO was expressed in the same cultures. Corresponding mRNA was isolated, full length cDNA was synthesized, cloned and sequenced. Two copies of cupin domains were found in the sequence of amino-acids conserved domain coding for the cupin enzyme. Comparison of the genomic DNA and cDNA sequences has revealed the presence of seventeen introns in the gene. The isoelectric point of the protein was estimated at pH 4.5 and several possible N-glycosylation sites were predicted.

Stability, Thermal Conductivity, Viscosity, and Tribological Characterization of Zirconia Nanofluids as a Function of Nanoparticle Concentration

Commercially prepared spherical zirconia (ZrO2) nanoparticles with an average particle diameter of 5 nm and functionalized with a hydrocarbon ligand were dispersed in a polyalphaolefin (PAO) base oil, producing a 10-nm stabilized zirconia nanofluid. The resulting nanofluid’s properties were characterized, including thermal conductivity and viscosity. A preliminary study of the nanofluid’s ability to generate protective tribofilms was conducted. Long-term stability was verified using dynamic light scattering (DLS) and average particle size was quantified as a function of time. A 10 wt% ZrO2 nanofluid maintained a 10-nm average particle size over 25 months, with no signs of agglomeration or sedimentation, and redispersion was not necessary before analysis. The tribological performance of several concentrations of ZrO2 nanofluids wasdisc characterized with a ball-on-disc tribometer. Tribofilm growth over time was collected via optical interference imaging. Friction data collected over time are also reported. Nanoparticle concentration was varied to understand its effect on tribofilm growth. The ZrO2 tribofilm morphology and chemistry were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM).

Synthesis of high payload nanohydrogels for the ecapsulation of hydrophilic molecules via inverse miniemulsion polymerization: caffeine as a case study

The association of an active principle with a nanocarrier is known to improve its stability and protect it from external factors. Nevertheless, loading of nanoparticles with highly hydrophilic substances like caffeine remains a tricky issue. In the present study, inverse miniemulsion systems were successfully coupled to UV radiation to synthesize polymeric nanohydrogels for drug delivery. The proper choice of the continuous and dispersed phase chemical composition led to the entrapment of active principle into the miniemulsion droplets. Our confinement-based strategy enabled unprecedented caffeine encapsulation efficiency inside 100-nm particles. Dimensional, thermal, and spectroscopic characterizations were carried out to investigate both unloaded and loaded nanohydrogels. Furthermore, in vitro release studies evaluated caffeine release kinetics from nanohydrogels by means of dialysis tests. It was demonstrated that controlled and sustained release occurred within the first 50 hours. Experimental data were found to fit the Higuchi model suggesting that the active principle release is diffusion controlled.