Influence of Eu3+ Doping on Physiochemical Properties and Neuroprotective Potential of Polyacrylic Acid Functionalized Cerium Oxide Nanoparticles.

Cerium oxide nanoparticles (CeONPs) exhibiting antioxidant properties are investigated as potential tools for neurodegenerative diseases. Here, we synthesized polyacrylic acid conjugated cerium oxide (CeO) nanoparticles, and further to enhance their neuroprotective effect, Eu3+ was substituted at different concentrations (5, 10, 15 and 20 mol%) to the CeO, which can also impart fluorescence to the system. CeONPs and Eu-CeONPs in the size range of 15-30 nm were stable at room temperature. The X-ray Photoelectron Spectroscopy (XPS) analysis revealed the chemical state of Eu and Ce components, and we could conclude that all Eu3+ detected on the surface is well integrated into the cerium oxide lattice. The emission spectrum of Eu-CeO arising from the 7F0 → 5D1 MD and 7F0 → 5D2 transitions indicated the Eu3+ ion acting as a luminescence center. The fluorescence of Eu-CeONPs was visualized by depositing them at the surface of positively charged latex particles. The developed nanoparticles were safe for human neuronal-like cells. Compared with CeONPs, Eu-CeONPs at all concentrations exhibited enhanced neuroprotection against 6-OHDA, while the protection trend of Eu-CeO was similar to that of CeO against H2O2 in SH-SY5Y cells. Hence, the developed Eu-CeONPs could be further investigated as a potential theranostic probe.

Physicochemical Features and Applicability of Newly Fabricated Phytopharmaceutical-Loaded Hydrogel Alginate Microcarriers with Viscoelastic Polyelectrolyte Coatings.

The design of novel polymeric carrier systems with functional coatings is of great interest for delivering various bioactive molecules. Microcapsules coated with polyelectrolyte (PE) films provide additional functionality and fine-tuning advantages essential for controlled drug release. We developed hydrogel microcarriers coated with functional PE films with encapsulated substances of natural origin, resveratrol (RES), curcumin (CUR), and epigallocatechin gallate (EGCG), which have cytotoxic and chemopreventive properties. Alginate (ALG) based microparticles were loaded with phytopharmaceuticals using the emulsification method, and then their surface was modified with PE coatings, such as chitosan (CHIT) or poly(allylamine hydrochloride) (PAH). The morphology and mean diameter of microcarriers were characterised by scanning electron microscopy, encapsulation efficiency was determined by UV-Vis spectroscopy, whereas the physicochemical properties of functional PE layers were studied using quartz crystal microbalance with dissipation monitoring and streaming potential measurements. The release profiles of active compounds from the hydrogel microparticles were described using the Peppas-Sahlin model. The cytotoxic effect of designed delivery systems was studied by evaluating their impact on the proliferation, mitochondrial metabolic function, and lipid peroxidation level of 5637 human bladder cancer cells. The present work demonstrates that the physicochemical and biological features of fabricated microcarriers can be controlled by the type of encapsulated anti-cancer agent and PE coating.

Physicochemical Characterisation of Polysaccharide Films with Embedded Bioactive Substances.

In this study, sodium carboxymethyl cellulose (CMCNa) bioactive films, crosslinked with citric acid (CA), were prepared and comprehensively examined for their suitability in various applications, focusing on food packaging. The films displayed favourable properties, including appropriate thickness, transparency, and moisture content, essential for packaging purposes. Moreover, the films exhibited excellent moisture absorption rate and barrier properties, attributed to the high concentration of CMCNa and the inclusion of a CA. These films presented no significant effect of crosslinking and bioactive components on their mechanical strength, as evidenced by tensile strength and elongation at break values. Thermal stability was demonstrated in the distinct weight loss events at different temperature ranges, with crosslinking contributing to slightly enhanced thermal performance. Furthermore, the films showed varying antioxidant activity levels, influenced by temperature and the solubility of the films in different media, indicating their potential for diverse applications. Overall, these bioactive films showed promise as versatile materials with desirable properties for food packaging and related applications, where the controlled release of bioactive components is advantageous for enhancing the shelf life and safety of food products. These findings contribute to the growing research in biodegradable and functional food packaging materials.

UV-Vis Sintering Process for Fabrication of Conductive Coatings Based on Ni-Ag Core-Shell Nanoparticles.

The UV-Vis sintering process was applied for the fabrication of conductive coatings composed of low-cost nickel-silver (Ni@Ag) nanoparticles (NPs) with core-shell structures. The metallic films were formed on a plastic substrate (polyethylene napthalate, PEN), which required their sintering at low temperatures to prevent the heat-sensitive polymer from destroying them. The UV-Vis sintering method, as a non-invasive method, allowed us to obtain metallic coatings with good conductivity at room temperature. In optimal sintering conditions, i.e., irradiation with a wavelength of 350-400 nm and time of 90 min, conductivity corresponding to about 30% of that of bulk nickel was obtained for the coatings based on Ni@Ag NPs.

Hydrophobisation of Silica Nanoparticles Using Lauroyl Ethyl Arginate and Chitosan Mixtures to Induce the Foaming Process.

We studied silica suspensions with chitosan and biodegradable synthetic surfactant lauroyl ethyl arginate (LAE). Hydrophilic and negatively charged silica nanoparticles were neutralised due to the coating with chitosan. That presence of LAE led to the partial hydrophobisation of their surface, which favoured their attachment to the surface of a thin foam film. It was found that the presence of small and medium-sized (6-9 nm) hydrophobic particles in the interfacial layer of lamella foam film inhibited the coalescence and coarsening processes, which prolonged the life of the foam. Furthermore, hydrophobising of 30 nm particles allowed the formation of large aggregates precipitating from the mixture under steady-state conditions. These aggregates, however, under the conditions of the dynamic froth flotation process in the foam column, were floated into the foam layer. As a result, they were trapped in the foam film and Plateau borders, effectively preventing liquid leakage out of the foam. These results demonstrate the efficiency of using chitosan-LAE mixtures to remove silica nanoparticles from aqueous phase by foaming and flotation.

Customizing polyelectrolytes through hydrophobic grafting.

This up-to-date review describes the design, fabrication approaches, properties and applications that have been employed in the field of hydrophobically decorated polyelectrolytes (HD-PEs), used as functionalized building blocks for speciality materials with tuneable features. These include, in particular, synthetic strategies for modification/hydrophobization of polyelectrolytes, self-organization of HD-PEs in aqueous systems, adsorption phenomena and applications in the field of surface chemistry. Rationally engineered HD-PEs can be achieved via either step-growth copolymerization of different reactive end groups of monomers, followed by appropriate post-synthesis treatment or as a result of decoration of a given polymer backbone with hydrophobic side groups. The influence of HD-PEs' chemical structure on their self-assembling and interfacial properties is dependent on the overall hydrophobicity, i.e. length, number and type of side chains stretched out to charged segment, number, type and strength of ionizable groups. We also conclude that the linking entity structure (ester, secondary amide, etc.) between the hydrophobic side chain and the charged polyelectrolyte backbone in the tailor-made HD-PEs plays a crucial role in self-aggregation behaviour in water and at interfaces. The examples of the unique ability of HD-PEs to adsorb at hydrophilic and hydrophobic interfaces is discussed considering the effect of the self-aggregation on the interfacial properties.

Multilayered Curcumin-Loaded Hydrogel Microcarriers with Antimicrobial Function.

The design of multifunctional microcarriers has attracted significant attention because they combine various functions within a single system. In this study, we developed a set of multilayered hydrogel microcarriers, which were first loaded with chemotherapeutic curcumin (CUR), then, using the layer-by-layer (LbL) technique, coated through a polyelectrolyte shell consisting of chitosan (CHIT) or poly(allylamine hydrochloride) (PAH). As an outer layer with antimicrobial function, newly synthesised alkylene quaternary ammonium salt functionalised polyelectrolytes (A-QAS-PEs) were applied. For this purpose, poly(acrylic acid) (PAA) was decorated with different hydrophobic side chains (n-hexane and n-dodecane side entities) and different degrees of substitution (m) of quaternary ammonium groups (abbreviated as PAA-C(O)O-(CH2)n-N+(CH3)3(m); n = 6, 12; m = 8-14%). The grafting approach of PAA with the alkylene quaternary ammonium salt moiety was performed under mild reaction conditions using Steglich esterification followed by quaternisation. The structure of antimicrobial decorated PAA was confirmed by 1H NMR and FTIR, and the mean diameter of all multifunctional microparticles was characterised by SEM. The viscoelastic properties of the functional layers were studied using quartz crystal microbalance with a dissipation (QCM-D). The release of CUR from the microcarriers was described using a hybrid model, i.e., a combination of first-order kinetics and the Korsmeyer-Peppas model. The antimicrobial activity of functionalised PAA and multilayered CUR-loaded hydrogel microcarriers with quaternary ammonium function was assessed against Staphylococcus aureus and Serratia marcescens by the agar diffusion assay method. Only a limited inhibition zone of PAA was observed, but in the case of both antimicrobial decorated PAA and the corresponding multilayered nanocarriers, the inhibitory activity increase was achieved against both strains of bacteria.

Anodic Electrodeposition of Chitosan-AgNP Composites Using In Situ Coordination with Copper Ions.

Chitosan is an attractive material for biomedical applications. A novel approach for the anodic electrodeposition of chitosan-AgNP composites using in situ coordination with copper ions is proposed in this work. The surface and cross-section morphology of the obtained coating with varying concentrations of AgNPs were evaluated by SEM, and surface functional groups were analyzed with FT-IR spectroscopy. The mechanism of the formation of the coating based on the chelation of Cu(II) ions with chitosan was discussed. The antibacterial activity of the coatings towards Staphylococcus epidermidis ATCC 35984/RP62A bacteria was analyzed using the live-dead approach. The presented results indicate that the obtained chitosan-AgNP-based films possess some limited anti-biofilm-forming properties and exhibit moderate antibacterial efficiency at high AgNP loads.

Benefits of pH-responsive polyelectrolyte coatings for carboxymethyl cellulose-based microparticles in the controlled release of esculin.

Moderate and prolonged payload release in response to a particular factor is highly demanded for efficient carriers of low-molecular-weight, chemically unstable phytopharmaceuticals. Thus, the objective of our contribution was to establish the effect of pH-responsive polyelectrolyte coatings on the release properties of carboxymethyl cellulose-based microparticles designed to deliver phytopharmaceuticals through the gastrointestinal tract. Microparticles were fabricated via extrusion coupled with external gelation and further coated with polyelectrolytes (PEs) (chitosan, gelatin, or PAH and PSS) involving electrostatic interactions. Successful deposition of PEs was confirmed by FTIR, and their thickness and viscosity were characterized in terms of QCM-D and ellipsometric techniques. The encapsulation efficiency of esculin, used as a model phytopharmaceutical, as proven by UV-Vis studies, was over 57%. SEM and fluorescence microscopy revealed a micrometric size, a mostly spherical shape and an altered topography of the investigated microcapsules. The physical stability of the microcapsules in media of various pH values was confirmed with CLSM and gravimetric studies. Studies on human gingival fibroblasts in vitro revealed that the obtained microparticles did not induce any cytotoxic effects. Payload release was monitored in situ by means of CLSM and ex situ under gastrointestinal conditions in vitro. Mathematical evaluation of the microparticle release profiles using classical models led to the establishment of a new hybrid model that revealed the mechanism behind esculin release. We demonstrated that the application of a polyelectrolyte shell onto CMC-based microspheres may provide controlled delivery of the payload, with its release triggered by the pH and ionic strength of the medium. These observations suggest that the release manner of small-molecule glycosides under gastrointestinal conditions can be tailored by careful selection of suitable materials to obtain biocompatible and functional hydrogel microparticles.

Interactions of Casein and Polypeptides in Multilayer Films Studied by FTIR and Molecular Dynamics.

Multilayer films containing α- and ß-casein and polypeptides, poly-L-lysine (PLL), and poly-L-arginine (PLArg) were formed by the layer-by-layer technique and Fourier Transform InfraRed spectroscopy with Attenuated Total Reflection (FTIR-ATR) and FTIR/Grazing Angle analyzed their infrared spectra. We investigated the changes of conformations of casein and polypeptides in the complexes formed during the build-up of the films. To elucidate the differences in the mechanism of complex formation leading to various growths of (PLL/casein)n and (PLArg/casein)n films, we performed the molecular dynamics simulations of the systems consisting of short PLL and PLArg chains and the representative peptide chains-casein fragments, which consists of several aminoacid sequences. The results of the simulation indicated the preferential formation of hydrogen bonds of poly-L-arginine with phosphoserine and glutamic acid residues of caseins. FTIR spectra confirmed those, which revealed greater conformational changes during the formation of casein complex with poly-L-arginine than with poly-L-lysine resulting from stronger interactions, which was also reflected in the bigger growth of (PLArg/casein)n films with the number of deposited layers.

Colloidal characteristics and functionality of rationally designed esculin-loaded hydrogel microcapsules.

This work reports the development of different types of alginate hydrogel microparticles designed specifically for the esculin (ESC) payload. Negatively charged alginate (ALG) microspheres were prepared by the ionotropic gelation technique, and an oppositely charged polyelectrolyte (PE) shell as a compatible polycation (chitosan (CHIT) or gelatin (GEL)) or a synthetic PEs (poly(allylamine hydrochloride) (PAH) and poly(4-styrenesulfonate) (PSS)) were adsorbed using electrostatic complexation. Thorough characterization of microparticles was performed with advanced microscopic techniques (scanning electron, fluorescence and confocal), followed by stability studies, ESC encapsulation efficacy determination and in vitro release kinetics measurements. We provide an in-depth investigation of the relationships between the properties (thickness, viscosity, areal mass, zeta potential) of the outer shell and the retaining and release abilities of the fabricated microcarriers, using quartz crystal microbalance with dissipation monitoring technique (QCM-D), spectroscopic ellipsometry and streaming potential measurements, combined in a new approach that was not attempted before for micrometric particles. The PAH-PSS and GEL coatings provided sufficient protection against ESC release under simulated gastric conditions that followed a two-stage Corrigan-Gallagher model with a marginal release rate in the first (lag) stage. This seems to be an interesting outcome, since it is rather peculiar for a low-molecular weight hydrophilic compound encapsulated in a highly porous microhydrogel to be released in such a manner.

Biocompatible long-sustained release oil-core polyelectrolyte nanocarriers: From controlling physical state and stability to biological impact.

It has been generally expected that the most applicable drug delivery system (DDS) should be biodegradable, biocompatible and with incidental adverse effects. Among many micellar aggregates and their mediated polymeric systems, polyelectrolyte oil-core nanocarriers have been found to successfully encapsulate hydrophobic drugs in order to target cells and avoid drug degradation and toxicity as well as to improve drug efficacy, its stability, and better intracellular penetration. This paper reviews recent developments in the formation of polyelectrolyte oil-core nanocarriers by subsequent multilayer adsorption at micellar structures, their imaging, physical state and stability, drug encapsulation and applications, in vitro release profiles and in vitro biological evaluation (cellular uptake and internalization, biocompatibility). We summarize the recent results concerning polyelectrolyte/surfactant interactions at interfaces, fundamental to understand the mechanisms of formation of stable polyelectrolyte layered structures on liquid cores. The fabrication of emulsion droplets stabilized by synergetic surfactant/polyelectrolyte complexes, properties, and potential applications of each type of polyelectrolyte oil-core nanocarriers, including stealth nanocapsules with pegylated shell, are discussed and evaluated.

Influence of electropolishing and anodic oxidation on morphology, chemical composition and corrosion resistance of niobium.

The work presents results of the studies performed on electropolishing of pure niobium in a bath that contained: sulphuric acid, hydrofluoric acid, ethylene glycol and acetanilide. After the electropolishing, the specimens were subjected to anodic passivation in a 1moldm(-3) phosphoric acid solution at various voltages. The surface morphology, thickness, roughness and chemical composition of the resulting oxide layers were analysed. Thusly prepared niobium samples were additionally investigated in terms of their corrosion resistance in Ringer's solution. The electropolished niobium surface was determined to be smooth and lustrous. The anodisation led to the growth of barrier-like oxide layers, which were enriched in phosphorus species.

Characterization of casein and poly-L-arginine multilayer films.

Thin films containing casein appear to be a promising material for coatings used in the medical area to promote biomineralization. α- and ß-casein and poly-L-arginine multilayer films were formed by the layer-by layer technique and their thickness and mass were analyzed by ellipsometry and quartz crystal microbalance with dissipation monitoring (QCM-D). (PLArg/casein) films deposited in 0.15M NaCl exhibit fast (exponential-like) growth of the film thickness with the number of layers. The resulting films were c.a. 10 times thicker than obtained for poly-L-arginine and natural polyanions. We investigated the effect of the type of casein used for the film formation, finding that films with α-casein were slightly thicker than ones with ß-casein. The effect of polyethylene imine anchoring layer on the thickness and mass of adsorbed films was similar as for linear polyelectrolyte pairs. Thickness of "wet" films was c.a. two times larger than measured after drying that suggests their large hydration. The analysis of the mass of films during their post-treatment with the solutions of various ionic strength and pH provided the information concerning films stability. Films remain stable in the neutral and weakly basic conditions that includes HEPES buffer, which is widely used in cell culture and biomedical experiments. At the conditions of high ionic strength films swell but their swelling is reversible. Films containing caseins as polyanion appear to be more elastic and the same time more viscous than one formed with polyelectrolyte pairs. XPS elemental analysis confirmed binding of calcium ions by the casein embedded in the multilayers.

Deposition of core latex particles encapsulated in polyelectrolyte shells at modified mica surfaces.

We used an oblique impinging jet (OIJ) cell to determine the initial deposition rates of model microcapsules at bare and modified by multilayer polyelectrolyte (PE) film mica surfaces. The transport conditions in the cell were quantitatively established by studying the kinetics of deposition of negatively charged latex at mica surfaces converted to positively charged by adsorption of (3-aminoprolyl)triethoxysilane. The dependence of reduced particle flux on the Reynolds number of the flow in the OIJ cell was determined by a direct counting of particles deposited on the mica surface. The results are described in terms of convective-diffusion theory taking into account hydrodynamic, dispersive, and electrostatic interactions, between the charged particles/capsules and the mica plate. In this way, transport conditions in the cell were characterized and they were used to interpret the results concerning the deposition of microcapsules with PE shells of various thickness obtained by layer-by-layer polyelectrolyte adsorption on colloidal cores. We demonstrated that the initial deposition rate of capsules is governed by the charge of the solid/liquid interface and the outermost layer of the capsule shell, and is largely independent of the thickness of the capsule shell or the number of PE layers at the mica surface. The deposition rates were in good agreement with theoretical predictions derived from the convective-diffusion theory.

Irreversible adsorption of particles on heterogeneous surfaces.

Methods of theoretical and experimental evaluation of irreversible adsorption of particles, e.g., colloids and globular proteins at heterogeneous surfaces were reviewed. The theoretical models were based on the generalized random sequential adsorption (RSA) approach. Within the scope of these models, localized adsorption of particles occurring as a result of short-ranged attractive interactions with discrete adsorption sites was analyzed. Monte-Carlo type simulations performed according to this model enabled one to determine the initial flux, adsorption kinetics, jamming coverage and the structure of the particle monolayer as a function of the site coverage and the particle/site size ratio, denoted by lambda. It was revealed that the initial flux increased significantly with the site coverage theta(s) and the lambda parameter. This behavior was quantitatively interpreted in terms of the scaled particle theory. It also was demonstrated that particle adsorption kinetics and the jamming coverage increased significantly, at fixed site coverage, when the lambda parameter increased. Practically, for alpha = lambda2theta(s) > 1 the jamming coverage at the heterogeneous surfaces attained the value pertinent to continuous surfaces. The results obtained prove unequivocally that spherically shaped sites were more efficient in binding particles in comparison with disk-shaped sites. It also was predicted that for particle size ratio lambda < 4 the site multiplicity effect plays a dominant role, affecting significantly the structure of particle monolayers and the jamming coverage. Experimental results validating main aspects of these theoretical predictions also have been reviewed. These results were derived by using monodisperse latex particles adsorbing on substrates produced by covering uniform surface by adsorption sites of a desired size, coverage and surface charge. Particle deposition occurred under diffusion-controlled transport conditions and their coverage was evaluated by direct particle counting using the optical and electron microscopy. Adsorption kinetics was quantitatively interpreted in terms of numerical solutions of the governing diffusion equation with the non-linear boundary condition derived from Monte-Carlo simulations. It was proven that for site coverage as low as a few percent the initial flux at heterogeneous surfaces attained the maximum value pertinent to homogeneous surfaces. It also was demonstrated that the structure of larger particle monolayers, characterized in terms of the pair correlation function, showed much more short-range ordering than predicted for homogeneous surface monolayers at the same coverage. The last part of this review was devoted to detection of polyelectrolyte multilayers on various substrates via particle deposition experiments.

Polystyrene latex adsorption at the gold/electrolyte interface.

Irreversible deposition of polystyrene latex particles (average diameter, 1.5 microm) on various solid/electrolyte interfaces was studied experimentally by using the direct microscope observation method. The substrate surfaces included bare mica (reference interface), gold covered mica (layer thickness of 50 nm), and solid gold plate. The morphology and thickness of the gold layer on mica was determined by atomic force microscopy. Well-defined transport conditions of particles were created by using the new impinging-jet cell. A characteristic feature of the cell was that the suspension stream was directed obliquely to the interface. This unique characteristic was advantageous allowing one for direct, in situ, observation of particle deposition at metals and other nontransparent interfaces. Experiments performed for various flow intensities indicated that the initial deposition kinetics at all interfaces was identical within the error bounds, in accordance with the model based on the convective-diffusion theory. It was concluded that the limiting flux was governed by the bulk transport rather than by the specific surface interactions.