Search Results (27)

Background/Objectives: Focused ultrasound has advantages as an external stimulus for drug delivery as it is non-invasive, has high precision and can penetrate deep into tissues. Here, we report a gold-plated alginate (ALG) hydrogel system that retains highly water-soluble small-molecule fluorescein for sharp off/on release after ultrasound exposure. Methods: The ALG is crosslinked into beads with calcium chloride and layered with a polycation to adjust the surface charge for the adsorption of catalytic platinum nanoparticles (Pt NPs). The coated bead is subject to electroless plating, forming a gold shell. Ultrasound is applied to the gold-plated ALG beads and the release of fluorescein with or without ultrasound stimulation is quantified. Results: Polyethylenimine (PEI), not poly-L-lysine (PLL), is able to facilitate Pt NP adsorption. Gold shell thickness is proportional to the duration of electroless plating and can be controlled. Gold-plated ALG beads are impermeable to the fluorescein cargo and have nearly zero leakage. Exposure to focused ultrasound initiated the release of fluorescein with full release achieved after 72 h. Conclusions: The gold-plated ALG hydrogel is a new material platform that can retain highly water-soluble molecules with a sharp off/on release initiated by focused ultrasound. Full article

Weak polyelectrolyte chains are versatile polymeric materials due to the large number of functional groups that can be used in different environmental applications. Herein, one weak polycation (polyethyleneimine, PEI) and two polyanions (poly(acrylic acid), PAA, and poly(sodium methacrylate), PMAA) were directly deposited through precipitation of an inter-polyelectrolyte coacervate onto the silica surface (IS), followed by glutaraldehyde (GA) crosslinking and extraction of polyanions chains. Four core–shell composites based on silica were synthesized and tested for adsorption of lead (Pb²⁺) and nickel (Ni²⁺) as model pollutants in batch sorption experiments on the laboratory scale. The sorbed/desorbed amounts depended on the crosslinking degree of the composite shell, as well as on the type of anionic polyelectrolyte. After multiple loading/release cycles of the heavy metal ions, the maximum sorption capacities were situated between 5–10 mg Pb²⁺/g composite and 1–6 mg Ni²⁺/g composite. The strong crosslinked composites (r = 1.0) exhibited higher amounts of heavy metal ions (Me²⁺) sorbed than the less crosslinked ones, with less PEI on the surface but with more flexible chains being more efficient than more PEI with less flexible chains. Core–shell composites based on silica and weak polyelectrolytes could act as sorbent materials, which may be used in water or wastewater treatment. Full article

The layer-by-layer (LbL) assembling of oppositely charged polyelectrolytes was studied using semi-synthetic polysaccharide derivatives, namely the polycations 6-aminoethylamino-6-deoxy cellulose (ADC) and cellulose (2-(ethylamino)ethylcarbamate (CAEC), as well as the polyanion cellulose sulfate (CS). The synthetic polymers poly(allylamine) (PAH) and poly(styrene sulfonate) (PSS) were employed as well for comparison. The stepwise adsorption process was monitored by whispering gallery mode (WGM) experiments and zeta-potential measurements. Distinct differences between synthetic- and polysaccharide-based assemblies were observed in terms of the quantitative adsorption of mass and adsorption kinetics. The LbL-approach was used to prepare µm-sized capsules with the aid of porous and non-porous silica particle templates. The polysaccharide-based capsule showed a switchable permeability that was not observed for the synthetic polymer materials. At ambient pH values of 7, low-molecular dyes could penetrate the capsule wall while no permeation occurred at elevated pH values of 8. Finally, the preparation of protein-loaded LbL-capsules was studied using the combination of CAEC and CS. It was shown that high amounts of protein (streptavidin and ovomucoid) can be encapsulated and that no leaking or disintegration of the cargo macromolecules occurred during the preparation step. Based on this work, potential use in biomedical areas can be concluded, such as the encapsulation of bioactive compounds (e.g., pharmaceutical compounds, antibodies) for drug delivery or sensing purposes. Full article

Glucosamine–chitosan synthesized by the Maillard reaction was combined with montmorillonite to obtain a nanohybrid composite to immobilize horseradish peroxidase. The material combines the advantageous properties of clay with those of the chitosan derivative; has improved water solubility and reduced molecular weight and viscosity; involves an eco-friendly synthesis; and exhibits ion exchange capacity, good adhesiveness, and a large specific surface area for enzyme adsorption. The physicochemical characteristics of the composite were analyzed by infrared spectroscopy and X-ray diffraction to determine clay–polycation interactions. The electrochemical response of the different polyphenols to glassy carbon electrodes modified with the composite was evaluated by cyclic voltammetry. The sensitivity and detection limit values obtained with the biosensor toward hydroquinone, chlorogenic acid, catechol, and resorcinol are (1.6 ± 0.2) × 10² µA mM⁻¹ and (74 ± 8) nM; (1.2 ± 0.1) × 10² µA mM⁻¹ and (26 ± 3) nM; (16 ± 2) µA mM⁻¹ and (0.74 ± 0.09) μM; and (3.7± 0.3) µA mM⁻¹ and (3.3 ± 0.2) μM, respectively. The biosensor was applied to quantify polyphenols in pennyroyal and lemon verbena extracts. Full article

The adsorption kinetics of human serum albumin (HSA) on bare and poly-L-arginine (PARG)-modified silica substrates were investigated using reflectometry and atomic force microscopy (AFM). Measurements were carried out at various pHs, flow rates and albumin concentrations in the 10 and 150 mM NaCl solutions. The mass transfer rate constants and the maximum protein coverages were determined for the bare silica at pH 4.0 and theoretically interpreted in terms of the hybrid random sequential adsorption model. These results were used as reference data for the analysis of adsorption kinetics at larger pHs. It was shown that the adsorption on bare silica rapidly decreased with pH and became negligible at pH 7.4. The albumin adsorption on PARG-functionalized silica showed an opposite trend, i.e., it was negligible at pH 4 and attained maximum values at pH 7.4 and 150 mM NaCl, the conditions corresponding to the blood serum environment. These results were interpreted as the evidence of a significant role of electrostatic interactions in the albumin adsorption on the bare and PARG-modified silica. It was also argued that our results can serve as useful reference data enabling a proper interpretation of protein adsorption on substrates functionalized by polyelectrolytes. Full article

Biocidal coatings are of great interest to the healthcare system. In this work, the biocidal activity of coatings based on a complex biocide containing polymer and inorganic active antibacterial components was studied. Silver oxide was distributed in a matrix of a positively charged interpolyelectrolyte complex (IPEC) of polydiallyldimethylammonium chloride (PDADMAC) and sodium polystyrene sulfonate (PSS) using ultrasonic dispersion, forming nanoparticles with an average size of 5–6 nm. The formed nanoparticles in the matrix are not subject to agglomeration and changes in morphology during storage. It was found that the inclusion of silver oxide in a positively charged IPEC allows a more than 4-fold increase in the effectiveness of the complex biocide against E. coli K12 in comparison with the biocidal effect of PDADMAC and IPEC. Polycation, IPEC, and the IPEC/Ag₂O ternary complex form coatings on the glass surface due to electrostatic adsorption. Adhesive and cohesive forces in the resulting coatings were studied with micron-scale coatings using dynamometry. It was found that the stability of the coating is determined primarily by adhesive interactions. At the macro level, it is not possible to reliably identify the role of IPEC formation in adhesion. On the other hand, use of the optical tweezers method makes it possible to analyze macromolecules at the submicron scale and to evaluate the multiple increase in adhesive forces when forming a coating from IPEC compared to coatings from PDADMAC. Thus, the application of ternary IPEC/Ag₂O complexes makes it possible to obtain coatings with increased antibacterial action and improved adhesive characteristics. Full article

Combretastatin derivatives is a promising class of antitumor agents, tubulin assembly inhibitors. However, due to poor solubility and insufficient selectivity to tumor cells, we believe, their therapeutic potential has not been fully realized yet. This paper describes polymeric micelles based on chitosan (a polycation that causes pH and thermosensitivity of micelles) and fatty acids (stearic, lipoic, oleic and mercaptoundecanoic), which were used as a carrier for a range of combretastatin derivatives and reference organic compounds, demonstrating otherwise impossible delivery to tumor cells, at the same time substantially reduced penetration into normal cells. Polymers containing sulfur atoms in hydrophobic tails form micelles with a zeta potential of about 30 mV, which increases to 40–45 mV when cytostatics are loaded. Polymers with tails of oleic and stearic acids form poorly charged micelles. The use of polymeric 400 nm micelles provides the dissolution of hydrophobic potential drug molecules. Micelles could significantly increase the selectivity of cytostatics against tumors, which has been shown using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, Fourier transform infrared (FTIR) spectroscopy, flow cytometry and fluorescence microscopy. Atomic force microscopy presented the difference between the unloaded micelles and those loaded with the drug: the size of the former was 30 nm on average, while the latter had a “disc-like” shape and a size of about 450 nm. The loading of drugs into the core of micelles was confirmed by UV and fluorescence spectroscopy methods; shifts of absorption and emission maxima into the long-wavelength region by tens of nm was observed. With FTIR spectroscopy, a high interaction efficiency of micelles with the drug on cells was demonstrated, but at the same time, selective absorption was observed: micellar cytostatics penetrate into A549 cancer cells 1.5–2 times better than the simple form of the drugs. Moreover, in normal HEK293T, the penetration of the drug is reduced. The proposed mechanism for reducing the accumulation of drugs in normal cells is the adsorption of micelles on the cell surface and the preservation of cytostatics to penetrate inside the cells. At the same time, in cancer cells, due to the structural features of the micelles, they penetrate inside, merging with the membrane and releasing the drug by pH- and glutathione-sensitive mechanisms. From a methodological point of view, we have proposed a powerful approach to the observation of micelles using a flow cytometer, which, in addition, allows us to quantify the cells that have absorbed/adsorbed cytostatic fluorophore and distinguish between specific and non-specific binding. Thus, we present polymeric micelles as drug delivery systems in tumors using the example of combretastatin derivatives and model fluorophore-cytostatic rhodamine 6G. Full article

It is still a challenge to develop advanced materials able to simultaneously remove more than one pollutant. Exclusive cationic composite double- and triple-network cryogels, with adequate sustainability in the removal of Cr₂O₇²⁻ and H₂PO₄⁻ oxyanions, were developed in this work starting from single-network (SN) sponges. Chitosan (CS), as the only polycation originating from renewable resources, and poly(N,N-dimethylaminoethylmethacrylate) (PDMAEMA) and polyethyleneimine (PEI), as synthetic polycations, were employed to construct multi-network cationic composite cryogels. The properties of the composites were tailored by the cross-linking degree of the first network (SN5 and SN20, which means CS with 5 or 20 mole % of glutaraldehyde, respectively) and by the order of the successive networks. FTIR, SEM-EDX, equilibrium water content and compressive tests were used in the exhaustive characterization of these polymeric composites. The sorption performances towards Cr₂O₇²⁻ and H₂PO₄⁻ anions were evaluated in batch mode. The pseudo-first-order, pseudo-second-order (PSO) and Elovich kinetics models, and the Langmuir, Freundlich and Sips isotherm models were used to interpret the experimental results. The adsorption data were the best fitted by the PSO kinetic model and by the Sips isotherm model, indicating that the sorption mechanism was mainly controlled by chemisorption, irrespective of the structure and number of networks. The maximum sorption capacity for both oxyanions increased with the increase in the number of networks, the highest values being found for the multi-network sponges having SN5 cryogel as the first network. In binary systems, all sorbents preferred Cr₂O₇²⁻ ions, the selectivity coefficient being the highest for TN sponges. The high sorption capacity and remarkable reusability, with only a 4–6% drop in the sorption capacity after five sorption–desorption cycles, recommend these composite cryogels in the removal of two of the most dangerous pollutants represented by Cr₂O₇²⁻ and H₂PO₄⁻. Full article

The surface properties of saponin and saponin-chitosan mixtures were analysed as a function of their bulk mixing ratio using vibrational sum-frequency generation (SFG), surface tensiometry and dilational rheology measurements. Our experiments show that saponin-chitosan mixtures present some remarkable properties, such as a strong amphiphilicity of the saponin and high dilational viscoelasticity. We believe this points to the presence of chitosan in the adsorption layer, despite its complete lack of surface activity. We explain this phenomenon by electrostatic interactions between the saponin as an anionic surfactant and chitosan as a polycation, leading to surface-active saponin-chitosan complexes and aggregates. Analysing the SFG intensity of the O-H stretching bands from interfacial water molecules, we found that in the case of pH 3.4 for a mixture consisting of 0.1 g/L saponin and 0.001 g/L chitosan, the adsorption layer was electrically neutral. This conclusion from SFG spectra is corroborated by results from surface tensiometry showing a significant reduction in surface tension and effects on the dilational surface elasticity strictly at saponin/chitosan ratios, where SFG spectra indicate zero net charge at the air–water interface. Full article

A linear polycation, poly(diallyldimethylammonium chloride), electrostatically interacts with anionic latex particles from a carboxylated butadiene–styrene copolymer in aqueous solution thus forming an interpolyelectrolyte complex. A mutual neutralization of oppositely charged latex and polycation groups occurs at W = latex/polycation = 50 w/w ratio. At W = 27, an ultimate polycation adsorption is reached, resulting in the formation of positive polycomplex particles, while at W ˂ 27, two-component systems are formed composed of positive polycomplex particles and free polycation. A film created from the W = 12 formulation shows a high toxicity to Gram-positive and Gram-negative bacteria and yeast. Repeated washing the film leads to partial removal of polycation and a 50% decrease in the activity of the film only towards Gram-negative Pseudomonas aeruginosa. The results indicate the potential for use of the mixed polymer formulations for the fabrication of antimicrobial films and coatings. Full article

In this review, we considered aspects related to the application of polyelectrolytes, primarily synthetic polyanions and polycations, to immobilize enzymes and regulate their properties. We mainly focused on the description of works in which polyelectrolytes were used to create complex and unusual systems (self-regulated enzyme–polyelectrolyte complexes, artificial chaperones, polyelectrolyte brushes, layer-by-layer immobilization and others). These works represent the field of “smart polymers”, whilst the trivial use of charged polymers as carriers for adsorption or covalent immobilization of proteins is beyond the scope of this short review. In addition, we have included a section on the molecular modeling of interactions between proteins and polyelectrolytes, as modeling the binding of proteins with a strictly defined, and already known, spatial structure, to disordered polymeric molecules has its own unique characteristics. Full article

Polyelectrolytes (PEs) have been the aim of many research studies over the past years. PE films are prepared by the simple and versatile layer-by-layer (LbL) approach using alternating assemblies of polymer pairs involving a polyanion and a polycation. The adsorption of the alternating PE multiple layers is driven by different forces (i.e., electrostatic interactions, H-bonding, charge transfer interactions, hydrophobic forces, etc.), which enable an accurate control over the physical properties of the film (i.e., thickness at the nanoscale and morphology). These PE nano-assemblies have a wide range of biomedical and healthcare applications, including drug delivery, protein delivery, tissue engineering, wound healing, and so forth. This review provides a concise overview of the most outstanding research on the design and fabrication of PE nanofilms. Their nanostructures, molecular interactions with biomolecules, and applications in the biomedical field are briefly discussed. Finally, the perspectives of further research directions in the development of LbL nano-assemblies for healthcare and medical applications are highlighted. Full article

Control of nonspecific/specific protein adsorption is the main goal in the design of novel biomaterials, implants, drug delivery systems, and sensors. The specific functionalization of biomaterials can be achieved by proper surface modification. One of the important strategies is covering the materials with functional coatings. Therefore, our work aimed to functionalize multilayer coating to control nonspecific/specific protein adsorption. The polyelectrolyte coating was formed using a layer-by-layer technique (LbL) with biocompatible polyelectrolytes poly-L-lysine hydrobromide (PLL) and poly-L-glutamic acid (PGA). Nonspecific protein adsorption was minimized/eliminated by pegylation of multilayer films, which was achieved by adsorption of pegylated polycations (PLL-g-PEG). The influence of poly (ethylene glycol) chain length on eliminating nonspecific protein adsorption was confirmed. Moreover, to achieve specific protein adsorption, the multilayer film was also functionalized by immobilization of antibodies via a streptavidin bridge. The functional coatings were tested, and the adsorption of the following proteins confirmed the ability to control nonspecific/specific adsorption: human serum albumin (HSA), fibrinogen (FIB), fetal bovine serum (FBS), carcinoembryonic antigen human (CEA) monitored by quartz crystal microbalance with dissipation (QCM-D). AFM imaging of unmodified and modified multilayer surfaces was also performed. Functional multilayer films are believed to have the potential as a novel platform for biotechnological applications, such as biosensors and nanocarriers for drug delivery systems. Full article

Natural and modified clay minerals have been extensively used for the adsorption/desorption of organic substances, especially pesticides, from waters and wastewater, aiming at pollution control and more efficient use of the herbicides through controlled release. While natural clay minerals efficiently remove organic cations such as paraquat and diquat, the adsorption of anionic or neutral species demands surface chemical modification with, for instance, quaternary ammonium salts containing long alkyl chains. Basic pesticides, on the other hand, are better absorbed in clay minerals modified with polycations. Kinetic studies and adsorption/desorption isotherms provide the parameters needed to evaluate the clay mineral’s adsorptive performance towards the pollutant target. However, the direct comparison of these parameters is complicated because the experimental conditions, the analytical techniques, the kinetic and isotherm models, and the numerical fitting method differ among the various studies. The free-energy-related Langmuir constant depends on the degree of site occupation; that is, it depends on the concentration window used to construct the adsorption isotherm and, consequently, on the analytical technique used to quantify the free concentrations. This paper reviews pesticides’ adsorption on natural and modified clay minerals and proposes guidelines for designing batch adsorption/desorption studies to obtain easily comparable and meaningful adsorption parameters. Articles should clearly describe the experimental conditions such as temperature, contact time, total concentration window, the solution to adsorbent ratio, the analytical technique, and its detection and quantification limits, besides the fitting models. Research should also evaluate the competitive effects of humic substances, colloidal inorganic particles, and ionic strength to emulate real-world adsorption experiments. Full article

Natural and synthetic polycations of different kinds attract substantial attention due to an increasing number of their applications in the biomedical industry and in pharmacology. The key characteristic determining the effectiveness of the majority of these applications is the number of macromolecules adsorbed on the surface of biological cells or their lipid models. Their study is complicated by a possible heterogeneity of polymer layer adsorbed on the membrane. Experimental methods reflecting the structure of the layer include the electrokinetic measurements in liposome suspension and the boundary potential of planar bilayer lipid membranes (BLM) and lipid monolayers with a mixed composition of lipids and the ionic media. In the review, we systematically analyze the methods of experimental registration and theoretical description of the laterally heterogeneous structures in the polymer layer published in the literature and in our previous studies. In particular, we consider a model based on classical theory of the electrical double layer, used to analyze the available data of the electrokinetic measurements in liposome suspension with polylysines of varying molecular mass. This model suggests a few parameters related to the heterogeneity of the polymer layer and allows determining the conditions for its appearance at the membrane surface. A further development of this theoretical approach is discussed. Full article