Electrophoretic Light Scattering Research Articles

Four-Component Statistical Copolymers by RAFT Polymerization.

This manuscript serves as the starting point for in-depth research of multicomponent, statistical, methacrylate-based copolymers that potentially mimic the behavior of proteins in aqueous solutions. These synthetic macromolecules are composed of specially chosen comonomers: methacrylic acid (MAA), oligoethylene glycol methyl ether methacrylate (OEGMA475), 2-(dimethylamino)ethyl methacrylate (DMAEMA) and benzyl methacrylate (BzMA). Monomer choice was based on factors such as the chemical nature of pendant functional groups, the polyelectrolyte/polyampholyte and amphiphilic character and the overall hydrophobic-hydrophilic balance (HLB) of the obtained quaterpolymers. Their synthesis was achieved via a one-pot reversible addition fragmentation chain transfer (RAFT) polymerization in two distinct compositions and molecular architectures, linear and hyperbranched, respectively, in order to explore the effects of macromolecular topology. The resulting statistical quaterpolymers were characterized via 1H-NMR and ATR-FTIR spectroscopies. Their behavior in aqueous solutions was studied by dynamic (DLS) and electrophoretic light scattering (ELS) and fluorescence spectroscopy (FS), producing vital information concerning their self-assembly and the structure of the formed aggregates. The physicochemical studies were extended by tuning parameters such as the solution pH and ionic strength. Finally, the quaterpolymer behavior in FBS/PBS solutions was investigated to test their colloid stability and biocompatibility in an in vivo-mimicking, biological fluid environment.

Physico-Chemical Properties of CdTe/Glutathione Quantum Dots Obtained by Microwave Irradiation for Use in Monoclonal Antibody and Biomarker Testing.

In this report, we present the results on the physicochemical characterization of cadmium telluride quantum dots (QDs) stabilized with glutathione and prepared by optimizing the synthesis conditions. An excellent control of emissions and the composition of the nanocrystal surface for its potential application in monoclonal antibody and biomarker testing was achieved. Two samples (QDYellow, QDOrange, corresponding to their emission colors) were analyzed by dynamic light scattering (DLS), and their hydrodynamic sizes were 6.7 nm and 19.4 nm, respectively. Optical characterization by UV-vis absorbance spectroscopy showed excitonic peaks at 517 nm and 554 nm. Photoluminescence spectroscopy indicated that the samples have a maximum intensity emission at 570 and 606 nm, respectively, within the visible range from yellow to orange. Infrared spectroscopy showed vibrational modes corresponding to the functional groups OH-C-H, C-N, C=C, C-O, C-OH, and COOH, which allows for the formation of functionalized QDs for the manufacture of biomarkers. In addition, the hydrodynamic radius, zeta potential, and approximate molecular weight were determined by dynamic light scattering (DLS), electrophoretic light scattering (ELS), and static light scattering (SLS) techniques. Size dispersion and the structure of nanoparticles was obtained by Transmission Electron Microscopy (TEM) and by X-ray diffraction. In the same way, we calculated the concentration of Cd2+ ions expressed in mg/L by using the Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-OES). In addition to the characterization of the nanoparticles, the labeling of murine myeloid cells was carried out with both samples of quantum dots, where it was demonstrated that quantum dots can diffuse into these cells and connect mostly with the cell nucleus.

Gold Nanoprobes for Detection of a Crucial EGFR Deletion for Early Diagnosis of Non-Small-Cell Lung Cancer

Gold nanoparticles (AuNPs) exhibit improved optical and spectral properties compared to bulk materials, making them suitable for the detection of DNA, RNA, antigens, and antibodies. Here, we describe a simple, selective, and rapid non-cross linking detection assay, using approx. 35 nm spherical Au nanoprobes, for a common mutation occurring in exon 19 of the epidermal growth factor receptor (EGFR), associated with non-small-cell lung cancer cells. AuNPs were synthesized based on the seed-mediated growth method and functionalized with a specific 16 bp thiolated oligonucleotide using a pH-assisted method. Both AuNPs and Au nanoprobes proved to be highly stable and monodisperse through ultraviolet-visible spectrophotometry, dynamic light scattering (DLS), and electrophoretic light scattering (ELS). Our results indicate a detection limit of 1.5 µg mL−1 using a 0.15 nmol dm−3 Au nanoprobe concentration. In conclusion, this work presents an effective possibility for a straightforward, fast, and inexpensive alternative for the detection of DNA sequences related to lung cancer, leading to a potential platform for early diagnosis of lung cancer patients.

Natural-Origin Betaine Surfactants as Promising Components for the Stabilization of Lipid Carriers.

In the present work, we demonstrate studies involving the influence of the formulation composition on the physicochemical properties of nanocarriers: solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs). Novel lipid-origin platforms were prepared using two "green" betaine-based surfactants, cocamidopropyl betaine (ROKAmina K30) and coco betaine (ROKAmina K30B), in combination with three different solid lipids, cetyl palmitate (CRODAMOL CP), trimyristin (Dynasan 114), and tristearin (Dynasan 118). Extensive optimization studies included the selection of the most appropriate lipid and surfactant concentration for effective SLN and NLC stabilization. The control parameters involving the hydrodynamic diameters of the obtained nanocarriers along with the size distribution (polydispersity index) were determined by dynamic light scattering (DLS), while shape and morphology were evaluated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Electrophoretic light scattering (ELS) and turbidimetric method (backscattering profiles) were used to assess colloidal stability. The studied results revealed that both betaine-stabilized SLN and NLC formulations containing CRODAMOL CP as lipid matrix are the most monodisperse and colloidally stable regardless of the other components and their concentrations used, indicating them as the most promising candidates for drug delivery nanosystems with a diverse range of potential uses.

Ketoconazole-loading strategy to improve antifungal activity and overcome cytotoxicity on human renal proximal tubular epithelial cells

Ketoconazole (KTZ), an antifungal agent used to treat localized or systemic fungal infections by inhibiting ergosterol synthesis, exhibits restricted efficacy within eukaryotic cells owing to its elevated toxicity and limited solubility in water. This study aims to improve the biological activity and overcome cytotoxic effects in the renal system of the hydrophobic KTZ by incorporating it into poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) utilizing biomaterial nano-engineering techniques. KTZ-loaded PLGA NPs (KTZ-NPs) were prepared by single emulsion solvent evaporation method and characterized by using dynamic light scattering (DLS), electrophoretic light scattering (ELS), Fourier transform-infrared (FT-IR) spectroscopy and scanning light microscopy (SEM). Particle size and zeta potential of KTZ-NPs were determined as 182.0 ± 3.27 nm and −27.4 ± 0.56 mV, respectively. Antifungal activity was analyzed with the time-kill and top agar dilution methods on Candida albicans (C. albicans) and Aspergillus flavus (A. flavus). Both KTZ and KTZ-NPs caused a significant decrease in A. flavus cell growth; however, the same effect was only observed in time-killing analysis on C. albicans, indicating a methodological difference in the antifungal analysis. According to the top agar method, the MIC value of KTZ-NPs against A. flavus was 9.1 μg ml−1, while the minimum inhibition concentration (MIC) value of KTZ was 18.2 μg ml−1. The twofold increased antifungal activity indicates that nanoparticular drug delivery systems enhance the water solubility of hydrophobic drugs. In addition, KTZ-NPs were not cytotoxic on human renal proximal tubular epithelial cells (HRPTEpCs) at fungistatic concentration, thus reducing fungal colonization without cytotoxic on renal excretion system cells.

Synthesis of polyaluminum chloride: Optimization of process parameters, characterization and performance investigation for water treatment

The present work was aimed to synthesis of polyaluminum chloride (PAC) using calcium oxide as a basification agent and optimization of process parameters on the yield of medium polymer species in PAC. The synthesis parameters were concentration of aluminum chloride hexahydrate (0.4 to 0.8 M), basicity ratio (2.0 to 2.4), reaction temperature (60 to 80 °C) and time (180 to 360 min). The performance of PΑC for water treatment was also investigated. The monomeric, medium polymeric and colloidal species of PAC were determined by Ferron test method. The PAC samples were characterized using various analytical techniques such as X-ray diffractometer (XRD), Fourier transformer infrared spectrometer (FTIR), scanning electron microscope (SEM), differential scanning calorimeter (DSC), dynamic light scattering (DLS) and electrophoretic light scattering (ELS). The turbidity and natural organic matter (NOM) of water samples were also determined using turbidimeter and UV–vis methods, respectively. The optimum yield of medium polymeric (Alb) content in PΑC species was predicted to 74.6 %, and the verification experiment result was 73.5 % at 0.5 M, 2.2, 75 °C and 273 min. The performance of PAC for water treatment revealed that the removals efficiencies of turbidity and NOM were reached to 98 % (pH = 7.2) and 86 % (pH = 6.8), respectively, at coagulant dose of 15 mg L−1 as Al. The residual aluminum concentration in the treated water was <0.2 mg L−1 which confirmed that the PAC could be used to treat drinking water.

Synthesis and characterization of phosphorylated cellulose nanocrystals for enhanced UV stability of epoxy nanocomposite films

Epoxy resins offer excellent chemical resistance, low-temperature curing, and low shrinkage. Despite these excellent properties, they are susceptible to UV degradation, which compromises their durability in outdoor applications. Herein, we fabricated a nanocomposite epoxy film based on phosphorylated cellulose nanocrystal (P-CNC) to improve the UV stability of cured epoxy resin by incorporating liquid ammonia-treated P-CNC into an epoxy matrix using integral blending method. Ammonium phosphate groups ((NH4)2HPO4) were formed by nucleophilic attack of phosphates by ammonia on the P-CNC surface. The functional groups, morphology, crystallinity index, and surface charges of P-CNC were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and electrophoretic light scattering (ELS), respectively. The effect of P-CNC on the UV stability of the fabricated epoxy nanocomposite film was investigated using FTIR and UV–Vis before and after exposure to UV photons. The results showed that the incorporation of 1.0 wt.% of surface-treated P-CNC into the epoxy matrix maintained the UV stability of the nanocomposite film up to 800 h. Finally, a mechanism for UV stability of P-CNC epoxy nanocomposite film was proposed whereby the (NH4)2HPO4 groups grafted onto the P-CNC surface absorb UV photons and convert them into low-energy thermal energy or short wavelength electromagnetic waves, which are not sufficient to initiate photodegradation of the nanocomposite film. Thus, this new film provides resistance against UV degradation for extended service life for outdoor applications of epoxy resin.

Synthesis, Characterization, and In Vitro Cytotoxicity Evaluation of Doxorubicin-Loaded Magnetite Nanoparticles on Triple-Negative Breast Cancer Cell Lines.

In this study, we investigated the cytotoxicity of doxorubicin (DOX)-loaded magnetic nanofluids on 4T1 mouse tumor epithelial cells and MDA-MB-468 human triple-negative breast cancer (TNBC) cells. Superparamagnetic iron oxide nanoparticles were synthesized using sonochemical coprecipitation by applying electrohydraulic discharge treatment (EHD) in an automated chemical reactor, modified with citric acid and loaded with DOX. The resulting magnetic nanofluids exhibited strong magnetic properties and maintained sedimentation stability in physiological pH conditions. The obtained samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, UV-spectrophotometry, dynamic light scattering (DLS), electrophoretic light scattering (ELS), vibrating sample magnetometry (VSM), and transmission electron microscopy (TEM). In vitro studies using the MTT method revealed a synergistic effect of the DOX-loaded citric-acid-modified magnetic nanoparticles on the inhibition of cancer cell growth and proliferation compared to treatment with pure DOX. The combination of the drug and magnetic nanosystem showed promising potential for targeted drug delivery, with the possibility of optimizing the dosage to reduce side-effects and enhance the cytotoxic effect on cancer cells. The nanoparticles' cytotoxic effects were attributed to the generation of reactive oxygen species and the enhancement of DOX-induced apoptosis. The findings suggest a novel approach for enhancing the therapeutic efficacy of anticancer drugs and reducing their associated side-effects. Overall, the results demonstrate the potential of DOX-loaded citric-acid-modified magnetic nanoparticles as a promising strategy in tumor therapy, and provide insights into their synergistic effects.

Preparation and optimization of hyaluronic acid decorated irinotecan-loaded poly(lactic-co-glycolic acid) nanoparticles by microfluidics for cancer therapy applications

Polymer-based nanoparticles have been largely investigated in the cancer therapy field for their features to generate colloidal delivery systems of hydrophobic drugs to improve drug stability, specific delivery and reduce toxicity. In particular, nanoparticles surface functionalized with hyaluronic acid have been widely employed for their active tumor-targeting efficiency. Furthermore, the control of the physicochemical properties as well as high drug encapsulation efficiency, yield and batch-to-batch reproducibility of nanoparticles obtained by means of microfluidics, pave the way to overcome the drawbacks related to the fabrication of NPs obtained via traditional bulk methods and consequently increase cancer cell killing effect. For these reasons, we here investigated the effects of process parameters on the preparation and optimization of poly(lactic-co-glycolic acid)-poloxamers nanoparticle formulations (PLGA/PF68+PF127 NPs) decorated with HA (HA-based NPs) by using microfluidics for intravenous delivery of a model chemotherapeutic agent, irinotecan (IRIN). The study on the aggregation behavior and morphology of NPs were investigated by Dynamic Light Scattering (DLS), Electrophoretic Light Scattering (ELS), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC). Our results revealed that by increasing the polymer weight fractions of organic and water phases the size, the NP yield, and the drug encapsulation efficiency of NPs are increased. Furthermore, by increasing the flow rate ratios from 0.05 to 0.3, a raise of dH from ∼85.6 to ∼176.4, for PLGA/PP NPs, and from ∼101.6 to ∼283.3 for HA/PLGA/PP is detected. The optimized HA-based NP formulation showed a spherical morphology, with a core-shell structure, small hydrodynamic diameter (dH∼120 nm), uniform size distribution (PDI<0.06) and high: i) drug loading (DL∼22.7%), ii) drug encapsulation efficiency (DEE∼87.8%) and iii) yield (92.4%). Moreover, the in vitro IRIN kinetic release and stability of IRIN-loaded HA-based NPs were evaluated showing the complete release in 15 days. Thus, this study highlighted a microfluidic method to fabricate IRIN-loaded HA-based NPs without any chemical modifications to provide novel understanding of the effect of process parameters, by varying the polymer weight fractions of both organic and water phases and flow rate ratio, on the physicochemical properties and consequently on nanoparticle formulation qualities for cancer therapy applications.

Biologically produced elemental sulfur clogging induced by thiols in gas biodesulfurization systems

The gas bio-desulfurization process involves the biotic oxidation of hydrogen sulfide (H2S) into hydrophilic and usable sulfur, which possesses favorable settleability, facilitating its separation and recovery from the bioreactor. Nonetheless, in thiol-containing gas bio-desulfurization systems, elemental sulfur is prone to aggregating and adhering to packings, pipes, pumps, and valves, leading to sulfur clogging and impeding the operation of the BDS process. This study systematically investigates the underlying mechanisms of sulfur agglomeration and clogging. A suite of analytical techniques, including laser diffraction, scanning electron microscopy (SEM), electrophoretic light scattering (ELS), X-ray diffraction (XRD), and sessile drop method, were employed to analyze the sulfur clogging phenomenon. The results reveal that the presence of thiols is a primary contributor to sulfur agglomeration and clogging. Thiols are commonly found in natural gas, biogas, and landfill gas and have a lowering effect on the surface hydrophilicity of sulfur particles, making them more hydrophobic and exacerbating sulfur aggregation. The accumulation of more agglomerated and less hydrophilic sulfur particles on packings and pipes leads to sulfur clogging. It occurs due to the nucleophilic S8 dissolution that promotes polysulfide formation and removes the hydrophilic biomacromolecules on the particle surface, making the sulfur particles more prone to aggregation. This study represents a pioneering effort to illuminate the mechanism behind sulfur clogging and attribute it to thiols, offering valuable insights for addressing the industrial challenge of sulfur clogging and expanding the application scope of gas bio-desulfurization.

Poly(lactic acid)/β-cyclodextrin based nanoparticles bearing ruthenium(II)-arene naproxen complex: preparation and characterisation. Analytical validation for metal determination by microwave-induced plasma optical emission spectrometry

The objectives of this work are to develop nanocarrier systems for the Ru(II)-p-cymene naproxen antitumor metallodrug, [Ru(η6-p-cymene)(npx)Cl] or Rupcy, based on polymeric nanoparticles (NPs) composed by the biodegradable poly(lactic acid) (PLA) and the hydrophilic polymerised β-cyclodextrin (PolyCD); to validate an analytical method for determination of Ru incorporated into the metallodrug loaded-NPs. The PolyCD was prepared by single step condensation and polymerisation reaction and incorporated as a polymer blend during the fabrication of PLA/PolyCD blends NPs and also as a core/shell structure built by adsorption of the PolyCD onto the surface of PLA NPs to give PLA(core)/PolyCD(shell) NPs. Three different loaded-systems incorporating the metallodrug (Rupcy-PLA NPs (1), Rupcy-PLA/PolyCD blends (2), and Rupcy-PLA(core)/PolyCD(shell) NPs (3)) were prepared by nanoprecipitation. The characterisation was performed by Proton Nuclear Magnetic Resonance, Matrix Assisted Laser Desorption/Ionization Time-of-Flight, Fourier-Transform Infra-red and UV-VIS Electronic Absorption Spectroscopies, Thermogravimetric Analysis, Differential Scanning Calorimetry, Dynamic Light Scattering, and Electrophoretic Light Scattering. Ru was determined by Microwave Induced Plasma Optical Emission Spectrometry (MIP-OES) with validation of the method. The metallodrug entrapment efficiency was around 90% (w/w) and drug loading was at 3–4% (w/w). The characterised metallodrug-loaded systems exhibited monomodal size distributions and appropriate hydrodynamic diameters [218.3 ± 13.5 (1), 205.4 ± 14.4 (2), 231.5 ± 22.0 (3) nm] and zeta potential values [−31.5 ± 2.2 (1), −26.1 ± 4.5 (2), −28.8 ± 6.1 (3) mV]. The validation of the MIP-OES method by evaluating selectivity, linearity, precision, accuracy, and limits of detection and quantification succeeded. The NPs parameters are compatible with colloidally stable systems. The MIP-OES method showed to be simple, reliable, and feasible to quantify indirectly the amount of the metallodrug-loaded into the PLA NPs.

A Simple Synthesis of Reduction-Responsive Acrylamide-Type Nanogels for miRNA Delivery

MicroRNAs (miRNAs) have great therapeutic potential; however, their delivery still faces huge challenges, especially given the short half-life of naked miRNAs due to rapid hydrolysis or inactivation by abundant nucleases in the systemic circulation. Therefore, the search for reliable miRNA delivery systems is crucial. Nanogels are one of the more effective nanocarriers because they are biocompatible and have a high drug-loading capacity. In this study, acrylamide-based nanogels containing cationic groups and redox-sensitive crosslinkers were developed for cellular delivery of anti-miR21 (a-miR21). To achieve this, post-polymerization loading of a-miR21 oligonucleotides into nanogels was performed by utilizing the electrostatic interaction between positively charged nanogels and negatively charged oligonucleotides. Different molar ratios of the amine groups (N) on the cationic nanogel and phosphate groups (P) on the miRNA were investigated. An N/P ratio of 2 allowed high miRNA loading capacity (MLC, 6.7% w/w) and miRNA loading efficiency (MLE, 99.7% w/w). Successful miRNA loading was confirmed by dynamic light scattering (DLS) and electrophoretic light scattering (ELS) measurements. miRNA-loaded nanogels (NG/miRNA) formed stable dispersions in biological media and showed an enhanced miRNA release profile in the presence of glutathione (GSH). Moreover, the addition of heparin to dissociate the miRNA from the cationic nanogels resulted in the complete release of miRNA. Lastly, a cell uptake study indicated that NG/miRNA could be easily taken up by cancer cells.

Effect of ZnO nanofluids on thermo-hydraulic characteristic of flow in a heated duct

ABSTRACT Utilizing nanofluids in place of traditional fluids is an innovative technique to boost heat exchange capability, as conventional fluids are ineffectual due to their limited thermal conductivity. In this study, nanofluids containing zinc oxide are produced at concentrations ranging from 0% to 1.5% by volume. Nanofluids are evaluated for zeta potential and particle size using a particle analyzer based on dynamic light scattering (DLS) and electrophoretic light scattering (ELS). The particle distribution curve for 0.2% concentration peaks at approximately 102 nm, but for 1.5% it moves to 185 nm, demonstrating that agglomeration increases at greater concentrations. All of the produced nanofluids are stable and exhibit zeta potentials greater than 30 mV. The stable nanofluids are characterized for viscosity and thermal conductivity as a function of concentration and temperature. The thermal conductivity of nanofluid is observed to increase with concentration and temperature, whereas the viscosity increases with concentration but decreases with temperature. A maximum increase of 12.1% in thermal conductivity and 30% increase in viscosity are found at 1.5% concentration. By passing it through a heated rectangular duct, the heat transfer characteristics of a ZnO nanofluids are determined numerically. The Nusselt number and entropy generation rate are examined at various temperatures and concentrations. Nusselt number is observed to rise with concentration with a maximum of 9.2% augmentation at 60 for 1.5% concentration whereas the rate of entropy generation decreases with concentration. In addition, the thermal performance index of the flow is found to rise with concentration from 0.956 at 0.2% concentration to 0.991 at 1.5% concentration.

Comparison of the Antibacterial Effect of Different Biological Silver Nanoparticles Synthetized and Integrated with Honeys

This study compares the morphologies, zeta potentials, and antibacterial effects a total 12 different microcompounds containing honey and silver nanoparticles, in a novel study of the difference between honey samples in nanoparticle synthesis, as well as the antibacterial interaction that those honey samples can have with the silver nanoparticles synthetized using them. Microcompounds were synthetized by combining silver nitrate solution with a honey sample and performing one of methods of biogenic synthesis: sunlight exposure, basification to pH 5 or basification to pH 10. Samples of each microcompound were also submitted to heat treatment, obtaining thus heated variants. Morphology and size data were obtained by Dynamic Light Scattering (DLS) analysis and Scanning Electron Microscopy (SEM); while zeta potential was measured by Electrophoretic Light Scattering. Broth microdilution, time-kill curves and SEM were used to access the antibacterial effect. Mean diameter of particles inside all microcompounds varied between 100 nm and 150 nm; and the zeta potential varied depending on the honey used. Minimal Inhibitory Concentrations (MIC) of microcompounds were between 15 μM and 500 μM. Time-kill curves showed that microcompounds had a faster and stronger effect against Escherichia coli than Staphylococcus aureus. Microcompounds obtained by basification to pH 5 or by sunlight were bactericidal, as they were capable of inhibiting bacterial growth (resulting in an antibacterial efficiency of 100% in 24 hours) at 125 μM against S. aureus and 62.5 μM against E. coli. SEM micrographs showed bacterial cells with lower cell density, blebs and other alteration after microcompound treatment.

Temperature Control of Yellow Photoluminescence from SiO2-Coated ZnO Nanocrystals.

In this study, we aimed to elucidate the effects of temperature on the photoluminescence from ZnO–SiO2 nanocomposite and to describe the preparation of SiO2-coated ZnO nanocrystals using a chemical precipitation method, as confirmed by Fourier transform infrared (FTIR) and powder X-ray diffraction analysis (XRD) techniques. Analyses using high-resolution transmission microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), and electrophoretic light scattering (ELS) techniques showed that the new nanocomposite has an average size of 70 nm and 90% silica. Diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and photoluminescence-excitation (PLE) measurements at different temperatures revealed two emission bands at 385 and 590 nm when the nanomaterials were excited at 325 nm. The UV and yellow emission bands were attributed to the radiative recombination and surface defects. The variable-temperature, time-resolved photoluminescence (VT-TRPL) measurements in the presence of SiO2 revealed the increase in the exciton lifetime values and the interplay of the thermally induced nonradiative recombination transfer of the excited-state population of the yellow emission via deep centers (DC). The results pave the way for more applications in photocatalysis and biomedical technology.

Interaction of surfactants with phospholipid vesicles in the low concentration regime

The interactions between diluted phospholipid vesicles (0.3 μM - 40 μM) and surfactants (around their cmc) have been investigated as model of the phenomena taking place when enveloped viruses are challenged by detergent formulations such as mouthwashes or dishwashing liquids. We have used negatively charged Small Unilamellar Vesicles (SUVs) to simulate the negatively charged viral envelope and surfactants with different charges: the anionic Sodium Dodecyl Sulphate (SDS), the cationic Cetylpyridinium Chloride (CPC) and the non-ionic Octaethylene glycol monodecyl ether (C10E8). Dynamic and Electrophoretic Light Scattering have been used to probe variations in size and surface charge of the vesicles. The surfactants effect on the membrane permeability was investigated by measuring the fluorescence of SUVs secluding the fluorophore calcein. All the surfactants perturb the bilayer inducing graded dye leakage. Irrespective of the chemical nature of the surfactant, the membrane leakage follows the same sigmoidal master curve when it is plotted against the ratio surfactant concentration/cmc. The membrane leakage is negligible below cmc/2 and above such a value increases up to the cmc where all the dye has been fully released. For ionic SDS and CPC the dependence of leakage halftime on such a scaled concentration is the same irrespective of the charge of the surfactant and the vesicles. The nonionic surfactant C10E8 induces the dye release from the SUV two orders-of-magnitude faster than the ionic surfactants. These results show that the rate-determining parameter for the permeabilization of the lipid bilayers is the electrostatic penalty to the flip-flop required to transport the surfactant inside the vesicle.

Inhibitory Effect against Listeria monocytogenes of Carbon Nanoparticles Loaded with Copper as Precursors of Food Active Packaging.

Human listeriosis is a serious foodborne disease of which outbreaks are occurring increasingly frequently in Europe. Around the world, different legal requirements exist to guarantee food safety. Nanomaterials are increasingly used in the food industry as inhibitors of pathogens, and carbon nanomaterials are among the most promising. In the present study, novel carbon nanoparticles loaded with copper (CNP-Cu) were prepared, and their antimicrobial activity against Listeria monocytogenes was assessed. CNPs of two sizes were synthesized and characterized by dynamic light scattering (DLS), electrophoretic light scattering (ELS) and electron microscopy (EM). The minimum inhibitory concentration (MIC) of CNP-Cu was determined in accordance with the available standard. To get insights into its mechanism of action, the release of copper ions into a cell media was assessed by inductively coupled plasma optical emission (ICP-OE), and the ability of loaded CNPs to generate cytotoxic reactive oxygen species (ROS) was evaluated by EPR spectroscopy. Finally, the extent of release of copper in a food simulant was assessed. The results demonstrated the antimicrobial effectiveness of CNP-Cu, with growth inhibition up to 85% and a release of copper that was more pronounced in an acidic food simulant. Overall, the results indicate CNP-Cu as a promising agent for the design of active food packaging which is able to improve food shelf-life.

Synthesis of High Molecular Weight Water-Soluble Polymers as Low-Viscosity Latex Particles by RAFT Aqueous Dispersion Polymerization in Highly Salty Media.

We report the synthesis of sterically-stabilized diblock copolymer particles at 20% w/w solids via reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of N,N′-dimethylacrylamide (DMAC) in highly salty media (2.0 M (NH4)2SO4). This is achieved by selecting a well-known zwitterionic water-soluble polymer, poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC), to act as the salt-tolerant soluble precursor block. A relatively high degree of polymerization (DP) can be targeted for the salt-insoluble PDMAC block, which leads to the formation of a turbid free-flowing dispersion of PDMAC-core particles by a steric stabilization mechanism. 1H NMR spectroscopy studies indicate that relatively high DMAC conversions (>99%) can be achieved within a few hours at 30 °C. Aqueous GPC analysis indicates high blocking efficiencies and unimodal molecular weight distributions, although dispersities increase monotonically as higher degrees of polymerization (DPs) are targeted for the PDMAC block. Particle characterization techniques include dynamic light scattering (DLS) and electrophoretic light scattering (ELS) using a state-of-the-art instrument that enables accurate ζ potential measurements in a concentrated salt solution. 1H NMR spectroscopy studies confirm that dilution of the as-synthesized dispersions using deionized water lowers the background salt concentration and hence causes in situ molecular dissolution of the salt-intolerant PDMAC chains, which leads to a substantial thickening effect and the formation of transparent gels. Thus, this new polymerization-induced self-assembly (PISA) formulation enables high molecular weight water-soluble polymers to be prepared in a highly convenient, low-viscosity form. In principle, such aqueous PISA formulations are highly attractive: there are various commercial applications for high molecular weight water-soluble polymers, while the well-known negative aspects of using a RAFT agent (i.e., its cost, color, and malodor) are minimized when targeting such high DPs.

Reproducibility of methods required to identify and characterize nanoforms of substances

Nanoforms (NFs) of a substance may be distinguished from one another through differences in their physicochemical properties. When registering nanoforms of a substance for assessment under the EU REACH framework, five basic descriptors are required for their identification: composition, surface chemistry, size, specific surface area and shape. To make the risk assessment of similar NFs efficient, a number of grouping frameworks have been proposed, which often require assessment of similarity on individual physicochemical properties as part of the group justification. Similarity assessment requires an understanding of the achievable accuracy of the available methods. It must be demonstrated that measured differences between NFs are greater than the achievable accuracy of the method, to have confidence that the measured differences are indeed real. To estimate the achievable accuracy of a method, we assess the reproducibility of six analytical techniques routinely used to measure these five basic descriptors of nanoforms: inductively coupled plasma mass spectrometry (ICP-MS), Thermogravimetric analysis (TGA), Electrophoretic light scattering (ELS), Brunauer–Emmett–Teller (BET) specific surface area and transmission and scanning electron microscopy (TEM and SEM). Assessment was performed on representative test materials to evaluate the reproducibility of methods on single NFs of substances. The achievable accuracy was defined as the relative standard deviation of reproducibility (RSDR) for each method.Well established methods such as ICP-MS quantification of metal impurities, BET measurements of specific surface area, TEM and SEM for size and shape and ELS for surface potential and isoelectric point, all performed well, with low RSDR, generally between 5 and 20%, with maximal fold differences usually <1.5 fold between laboratories. Applications of technologies such as TGA for measuring water content and putative organic impurities, additives or surface treatments (through loss on ignition), which have a lower technology readiness level, demonstrated poorer reproducibility, but still within 5-fold differences. The expected achievable accuracy of ICP-MS may be estimated for untested analytes using established relationships between concentration and reproducibility, but this is not yet the case for TGA measurements of loss on ignition or water content. The results here demonstrate an approach to estimate the achievable accuracy of a method that should be employed when interpreting differences between NFs on individual physicochemical properties.

The Effect of Submicron Polystyrene on the Electrokinetic Potential of Cell Membranes of Red Blood Cells and Platelets.

In recent years, many scientists have studied the effects of polymer micro- and nanostructures on living organisms. As it turns out, plastic can be a component of the blood of livestock, eaten by humans around the globe. Thus, it seems important to investigate possible changes in the physicochemical parameters and morphology of the cell membranes of blood morphotic elements (red blood cells and platelets) under the influence of polymer particles. The article presents research in which cell membranes were exposed to plain polystyrene (PS) and amino-functionalized polystyrene (PS-NH2) of two different sizes. The polymers were characterized by infrared spectroscopy and dynamic light-scattering methods. To analyze possible changes caused by polymer exposure in the structure of the membranes, their zeta potentials were measured using the electrophoretic light-scattering technique. The concentration of the polymers, as well as the exposure time, were also taken into the consideration during the research. Based on the obtained results, we concluded that 100 and 200 nm PS, as well as 100 nm PS-NH2, internalize into the cells. On the contrary, 200 nm PS-NH2 particles attach to cell membranes. Our study clearly shows that particle size and surface chemistry determine the interaction with biological membranes.