Silver/polyethylene glycol (Ag/PEG) nanofluids have recently emerged as promising system for neuromorphic engineering due to the ability to form long-range conductive connections between electrodes through the nanoparticle (NP) self-organization in an electric field. These connections exhibit reversible resistive switching between multiple resistance states, making them attractive candidates for reconfigurable neuromorphic systems. However, the use of PEG as liquid matrix presents challenges for operational stability. Its hygroscopicity and ionic conductivity render the system highly sensitive to environmental conditions, including temperature and humidity. To investigate these effects, we performed detailed electrical characterization of Ag/PEG nanofluids under varying temperatures in ambient atmosphere and under vacuum. The results showed that both factors strongly influence switching behaviour. Although operation of the nanofluids at elevated temperatures enhances the conductivity of PEG by increasing ion mobility, the probability of switching events decreases, leading the system to stabilize in transition resistance state. Similar stabilization was observed after transferring the system to vacuum, where the number of cycles required for switching to low resistance state increased significantly. Afterwards, the path was locked in transition resistance states. These phenomena are attributed to the reduced electrophoretic mobility of Ag NPs, directly linked to decrease in their zeta-potential with increasing temperature. The simultaneous desorption of water from PEG and desorption of PEG chains from NP surfaces likely contribute to reduction in NP mobility. Overall, these findings highlight the role of environmental control in achieving stable and reproducible resistive switching in Ag/PEG nanofluids, providing valuable insights for the design of liquid neuromorphic systems.

Potentiometric ion sensors represent a significant subgroup of electrochemical sensors. In this study, we have developed a potentiometric sensor using an electrically conductive copolymer of 2,2'-bithiophene (BT) and 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) for the selective detection of Ca2+ ions in extracellular interstitial fluids. The integration of BAPTA with its highly selective calcium chelating properties into a polymer matrix via electrochemical polymerization results in a sensitive conductive polymer layer that effectively detects the presence of calcium ions. This sensor aims at the early detection of inflammation or infection around implants because local calcium concentration is strongly elevated in interstitial fluid in such pathologies. The potentiometric study proves the incorporation of BAPTA into the polymer matrix was successful and its potential decreased upon calcium binding demonstrating the Nernstian behavior with a slope of approximately 20 ± 0.3 mV per decade in the concentration range from 0.1 mM to 1 mM. Moreover, the selectivity coefficient of -0.4 was measured by SSM and calculated from the Nicolsky-Eisenmann equation, which indicates selectivity towards Ca2+ ions with respect to Mg2+ ions.

Gel polymer electrolytes for lithium-ion batteries are typically prepared by swelling a preprepared cross-linked polymer network with a solution of lithium salt. This step of the electrolyte preparation is assumed to be straightforward, and very little attention has been paid to the investigation of the swelling mechanism. We questioned the common assumption that the feed solution swells the polymer network at the same concentration and fed a polyoxazoline network with several concentrations of lithium bis(oxalato)borate and lithium bis(trifluoromethane)sulfonimide solutions in propylene carbonate and diglyme. We thoroughly analyzed the obtained gels using NMR and Raman spectroscopy and evaluated the content of the solvent and salt in the polymer matrix, their mutual interactions, and mobilities. We found that this assumption was invalid and created a model of swelling of a polyoxazoline network with a salt solution. Our model implies the importance of often neglected solvent-polymer interactions or lack thereof. In the context of the function of the polyoxazoline system, our results provide insights into the efficiency of polymer matrices for gel polymer electrolytes, which will help avoid inefficient polymer matrices in the future.

We investigated the stimuli-responsive behavior of hybrid κ-carrageenan-based polymers grafted with poly(2-isopropyl-2-oxazoline-co-2-butyl-2-oxazoline) (POX), focusing on how these polymers respond simultaneously to mono- and divalent metal cations as well as changes in temperature. The aim of this study was to explore their potential for biological and radiopharmaceutical applications, where their responsiveness to specific stimuli is crucial. To achieve this, we used dynamic light scattering and small-angle X-ray scattering as key methodologies. We examined how the length and density of POX grafts influenced the polymers' solubility transitions and formation of nanogel clusters. Our results showed that shorter POX grafts resulted in smaller nanogel clusters, with graft length having a more significant effect on particle size compared to graft density. In addition, polymers with shorter grafts exhibited a higher temperature at which solubility changes occurred. The study also examines the effects of metal ions (Na+, K+, Rb+, Ca2+, and Sr2+) on the nanogel structure. We found that the fractal dimension of the clusters decreased for K+ and Ca2+ when the POX groups lost their solubility above the lower critical solution temperature (LCST), whereas it remained stable for Na+. Our findings highlight the complex molecular interactions and stimulus-responsivity cross-talks that govern the stimulus-responsive behavior of these hybrid copolymers. Understanding these interactions opens up avenues for future applications.

Developing novel memristive systems aims to implement key principles of biological neuron assemblies - plasticity, adaptivity, and self-organization - into artificial devices for parallel, energy-efficient computing. Solid-state memristive devices, such as crossbar arrays and percolated nanoparticle (NP) networks, already demonstrate these properties. However, closer similarity to neural networks is expected from liquid-state systems, including polymer melts, which remain largely unexplored. Here, the resistive switching in silver/poly(ethylene glycol) (Ag/PEG) nanofluids, prepared by depositing gas-aggregated Ag NPs into PEGs of varying molecular mass, is investigated. These systems form long-range conductive NP bridges with reconfigurable resistance states in response to an electric field. The zeta-potential of Ag NPs and molecular mobility of PEG determine the prevalence of low resistance (ohmic) state, high resistance states (poor conductance) or intermediate transition states governed by space-charge-limited conduction or electron tunneling. The occurrence of these states is given by the interparticle gaps, which are determined by the conformation of PEG molecules adsorbed on the NPs. It is presented, for the first time, an equivalent circuit model for the Ag/PEG system. These findings pave the way to adopt polymer melts as matrices for neuromorphic engineering and bio-inspired electronics.

The permeability and responsiveness of polymer membranes are absolutely relevant in the design of polymersomes for cargo delivery. Accordingly, we herein correlate the structural features, permeability, and responsiveness of doxorubicin-loaded (DOX-loaded) nonresponsive and stimuli-responsive polymersomes with their in vitro and in vivo antitumor performance. Polymer vesicles were produced using amphiphilic block copolymers containing a hydrophilic poly[N-(2-hydroxypropyl)methacrylamide] (PHPMA) segment linked to poly[N-(4-isopropylphenylacetamide)ethyl methacrylate] (PPPhA, nonresponsive block), poly[4-(4,4,5,5-tetra-methyl-1,3,2-dioxaborolan-2-yl)benzyl methacrylate] [PbAPE, reactive oxygen species (ROS)-responsive block], or poly[2-(diisopropylamino)ethyl methacrylate] (PDPA, pH-responsive block). The PDPA-based polymersomes demonstrated outstanding biological performance with antitumor activity notably enhanced compared to their counterparts. We attribute this behavior to a fast-triggered DOX release in acidic tumor environments as induced by pH-responsive polymersome disassembly at pH < 6.8. Possibly, an insufficient ROS concentration in the selected tumor model attenuates the rate of ROS-responsive vesicle degradation, whereas the nonresponsive nature of the PPPhA block remarkably impacts the performance of such potential nanomedicines.

Advanced materials based on polyoxazoline chemistry are presented as electrochemically, mechanically and thermally stable, efficient and versatile "green" gel polymer electrolytes (GPEs). A series of GPEs was prepared by cationic ring-opening copolymerization (CROP) of two 2-oxazolines with different ratios of the comonomers and their subsequent crosslinking and swelling in Li salt solution. The samples were investigated in terms of their ionic conductivity, thermal properties and ionic diffusion. Finally, a lithium stripping/plating experiment was used to evaluate their electrochemical stability. Promising electrolytes possessing high conductivity (3.7 center dot 10(-4) S/cm at 20 degrees C) and excellent durability were obtained.

Self-assembled bilayer structures such as those produced from amphiphilic block copolymers (polymersomes) are potentially useful in a wide array of applications including the production of artificial cells and organelles, nanoreactors, and delivery systems. These constructs are of important fundamental interest, and they are also frequently considered toward advances in bionanotechnology and nanomedicine. In this framework, membrane permeability is perhaps the most important property of such functional materials. Having in mind these considerations, we herein report the manufacturing of intrinsically permeable polymersomes produced using block copolymers comprising poly[2-(diisopropylamino)-ethyl methacrylate] (PDPA) as the hydrophobic segment. Although being water insoluble at pH 7.4, its pKa(PDPA) ∼ 6.8 leads to the presence of a fraction of protonated amino groups close to the physiological pH, thus conducting the formation of relatively swollen hydrophobic segments. Rhodamine B-loaded vesicles demonstrated that this feature confers inherent permeability to the polymeric membrane, which can still be modulated to some extent by the solution pH. Indeed, even at higher pH values where the PDPA chains are fully deprotonated, the experiments demonstrate that the membranes remain permeable. While membrane permeability can be, for instance, regulated by introducing membrane proteins and DNA nanopores, examples of membrane-forming polymers with intrinsic permeability have been seldom reported so far, and the possibility to regulate the flow of chemicals in these compartments by tuning block copolymer features and ambient conditions is of due relevance. The permeable nature of PDPA membranes possibly applies to a wide array of small molecules, and these findings can in principle be translocated to a variety of disparate bio-related applications.

Due to their wide availability, polypeptide/protein venoms produced by certain insects are of high interest as potential active pharmacological ingredients; however, the number of clinical studies on these venoms remains poor. In this paper, we describe an extremely efficient platform to form polyplexes from cationic amphiphilic animal venoms, such as the hemolytic poison melittin. The idea is based on supramolecular melittin cationic charge compensation with nanoparticles (micelles composed of hydrophobic glassy polystyrene core and hydrophilic poly(meth)acrylic acid corona, PMA and PAA acid homopolymers) with high anion charge density at physiological pH. An instant "mix and go" process and efficient melittin complexation with nanoparticles at concentrations down to micrograms per milliliter of PBS solution was achieved and proven by inhibition of melittin-induced hemolysis. We studied in detail how the structural features of the nanoparticles influence their potency; we found that the most important parameter is the number of carboxylates in the polyanion chain (proportional to the molecular weight and length of the anionic poly(meth)acrylic acid block). The poly(meth)acrylic acid-based polymer nanoparticles may be useful as melittin (and possibly other cationic amphiphilic animal venoms) antidotes but also as models for constructing future delivery systems to apply the venoms therapeutically.

The ability to tune size and morphology of self-assemblies is particularly relevant in the development of delivery systems. By tailoring such structural parameters, one can provide larger cargo spaces or produce nanocarriers that can be loaded by hydrophilic and hydrophobic molecules starting ideally from the same polymer building unit. We herein demonstrate that the morphology of block copolymer-based pH-triggered nanoplatforms produced from poly(2-methyl-2-oxazoline)m-b-poly[2-(diisopropylamino)-ethyl methacrylate]n (PMeOxm-b-PDPAn) is remarkably influenced by the overall molecular weight of the block copolymer, and by the selected method used to produce the self-assemblies. Polymeric vesicles were produced by nanoprecipitation using a block copolymer of relatively low molecular weight (Mn ∼ 10 kg.mol-1). Very exciting though, despite the high hydrophobic weight ratio (wPDPA > 0.70), this method conducted to the formation of core-shell nanoparticles when block copolymers of higher molecular weight were used, thus suggesting that the fast (few seconds) self-assembly procedure is controlled by kinetics rather than thermodynamics. We further demonstrated the formation of vesicular structures using longer chains via the solvent-switch approach when the "switching" to the bad solvent is performed in a time scale of a few hours (approximately 3 hs). We accordingly demonstrate that using fairly simple methods one can easily tailor the morphology of such block copolymer self-assemblies, thereby producing a variety of structurally different pH-triggered nanoplatforms via a kinetic or thermodynamically-controlled process. This is certainly attractive towards the development of nanotechnology-based cargo delivery systems.

We developed acid-functionalized glycogen conjugates as supramolecular carriers for efficient encapsulation and inhibition of a model cationic peptide melittin─the main component of honeybee venom. For this purpose, we synthesized and characterized a set of glycogens, functionalized to various degrees by several different acid groups. These conjugates encapsulate melittin up to a certain threshold amount, beyond which they precipitate. Computer simulations showed that sufficiently functionalized conjugates electrostatically attract melittin, resulting in its efficient encapsulation in a broad pH range around the physiological pH. Hemolytic assays confirmed in vitro that the effective inhibition of melittin's hemolytic activity occurs for highly functionalized samples, whereas no inhibition is observed when using low-functionalized conjugates. It can be concluded that functional glycogens are promising carriers for cationic molecular cargos or antidotes against animal venoms under conditions, in which suitable properties such as biodegradability and biocompatibility are crucial.

The influence of magnetite nanoparticles coated with poly(acrylic acid) (Fe3O4@PAA NPs) on the organization of block copolymer thin films via a self-assembly process was investigated. Polystyrene-b-poly(4-vinylpyridine) films were obtained by the dipcoating method and thoroughly examined by X-ray reflectivity, transmission electron microscopy, atomic force microscopy, and grazing incidence small-angle scattering. Magnetic properties of the films were probed via superconducting quantum interference device (SQUID) magnetometry. It was demonstrated that due to the hydrogen bonding between P4VP and PAA, the Fe3O4@PAA NPs segregate selectively inside P4VP domains, enhancing the microphase separation process. This in turn, together with employing carefully optimized dip-coating parameters, results in the formation of hybrid thin films with highly ordered nanostructures. The addition of Fe3O4@PAA nanoparticles does not change the average interdomain spacing in the film lateral nanostructure. Moreover, it was shown that the nanoparticles can easily be removed to obtain well-ordered nanoporous templates.

We show that the cloud point temperature (TCP) of thermoresponsive polyacrylamides is considerably lower in physiologically relevant solvents (phosphate-buffered saline, serum) than in pure water. This decrease of TCP may be critical for some biomedical applications.

In situ 1H NMR characterization of copolymerization reactions of various 2-oxazoline monomers at different molar ratios offers detailed insight into the build-up and composition of the polymer chains. Various 2-oxazolines were copolymerized in one single solvent, butyronitrile, with 2-dec-9′-enyl-2-oxazoline, where the double bond allows for post-polymerization modification and can function as a crosslinking unit to form polymer networks. The types of the monomers and their molar ratios in the feed have a strong effect on the microstructure of the forming copolymer chains. Copolymers comprising 2-dec-9′-enyl-2-oxazoline and either 2-ethyl-, 2-isopropyl-, 2-butyl-, 2-heptyl, 2-nonyl- or 2-phenyl-2-oxazoline, show significant differences in sequential structure of copolymers ranging from block to gradient and random ordering of the monomer units. 1H NMR was found to be a powerful tool to uncover detailed oxazoline copolymerization kinetics and evolution of chain composition.

CROP and RAFT polymerization was used to produce PMeOxm-b-PDPAn block copolymers. The microfluid technique enabled the manufacturing of pH-triggered nanoplatforms with different morphologies as driven by the overall molecular weight of the chains.

The static and dynamic properties of a range of molecular weights (2 x 10(4) to 1.6 x 10(5) g/mol) of poly(benzyl methacrylate) have been assessed in four different imidazolium- and pyrrolidinium-based ionic liquids over a wide temperature range (27-155 degrees C), primarily using light scattering techniques. All four systems exhibit lower critical solution temperature phase behavior. The relevant structural, dynamic, and thermodynamic parameters were examined as a function of concentration, temperature, and molecular weight. Some interesting observations were revealed. The phase boundaries suggest a shift of the critical composition toward the polymer-rich region, in contrast to the low critical concentrations for polymers commonly observed in polymer solutions. Surprisingly, the second virial coefficient (A(2)) remains positive, even at temperatures close to phase separation, where A(2) < 0 is anticipated. Furthermore, A(2) also shows stronger dependence on molecular weight than commonly observed for polymers in good solvents. On the dynamic side, the diffusion virial coefficients (k(d)) remained positive over the given temperature range, further corroborating the apparent good solvent behavior of A(2). The excluded volume exponents (v approximate to 0.53-0.54) obtained from the dependence of hydrodynamic radii on molecular weight also indicate good solvent characteristics.

1H NMR methods in combination with dynamic light scattering were applied to study temperature behavior of poly(2-isopropyl-2-oxazoline) (PIPOx) homopolymer as well as PIPOx-b-poly(2-methyl-2-oxazoline) (PMeOx) and poly(2-ethyl-2-oxazoline) (PEtOx)-b-PMeOx diblock copolymers in aqueous solutions. 1H NMR spectra showed a different way of phase transition for the main and side chains in PIPOx-based solutions. Additionally, the phase transition is irreversible for PIPOx homopolymer and partially reversible for PIPOx-b-PMeOx copolymer. As revealed by NMR, the phase transition in PEtOx-based copolymers solutions exists despite the absence of solution turbidity. It is very broad, virtually independent of the copolymer composition and reversible with some hysteresis. Two types of water molecules were detected in solutions of the diblock copolymers above the phase transition—“free” with long and “bound” with short spin–spin relaxation times T2. NOESY spectra revealed information about conformational changes observed already in the pre-transition region of PIPOx-b-PMeOx copolymer solution.

Magnetic and temperature-sensitive solid lipid particles (mag. SLPs) were prepared in the presence of oleic acid-coated iron oxide (IO-OA) nanoparticles with 1-tetradecanol and poly(ethylene oxide)-block-poly(ε-caprolactone) as lipid and stabilizing surfactant-like agents, respectively. The particles, typically ~850 nm in hydrodynamic size, showed heat dissipation under the applied alternating magnetic field. Cytotoxic activity of the mag.SLPs, non-magnetic SLPs, and iron oxide nanoparticles was compared concerning the mammalian cancer cell lines and their drug-resistant counterparts using trypan blue exclusion test and MTT assay. The mag.SLPs exhibited dose-dependent cytotoxicity against human leukemia cell lines growing in suspension (Jurkat and HL-60/wt), as well as the doxorubicin (Dox)- and vincristine-resistant HL-60 sublines. The mag.SLPs showed higher cytotoxicity toward drug-resistant sublines as compared to Dox. The human glioblastoma cell line U251 growing in a monolayer culture was also sensitive to mag.SLPs cytotoxicity. Staining of U251 cells with the fluorescent dyes Hoechst 33342 and propidium iodide (PI) revealed that mag.SLPs treatment resulted in an increased number of cells with condensed chromatin and/or fragmented nuclei as well as with blebbing of the plasma membranes. While the Hoechst 33342 staining of cell suggested the pro-apoptotic activity of the particles, the PI staining indicated the pro-necrotic changes in the target cells. These conclusions were confirmed by Western blot analysis of apoptosis-related proteins, study of DNA fragmentation (DNA laddering due to the inter-nucleosomal cleavage and DNA comets due to single strand breaks), as well as by FACS analysis of the patterns of cell cycle distribution (pre-G1 phase) and Annexin V/PI staining of the treated Jurkat cells. The induction of apoptosis or necrosis by the particles used to treat Jurkat cells depended on the dose of the particles. Production of the reactive oxygen species (ROS) was proposed as a potential mechanism of mag.SLPs-induced cytotoxicity. Accordingly, hydrogen peroxide and superoxide radical levels in mag.SLPs-treated Jurkat leukemic cells were increased by ~20-40 and ~70%, respectively. In contrast, the non-magnetic SLPs and neat iron oxides did not influence ROS levels significantly. Thus, the developed mag.SLPs can be used for effective killing of human tumor cells, including drug-resistant ones.

ABSTRACTThe current work presents a pivotal study of the nanogelation of the linear poly(N5‐2‐hydroxypropyl‐L‐glutamine) polymer precursor containing tyramine (TYR) units in an inverse miniemulsion by horseradish peroxidase/H2O2‐mediated crosslinking. The effects of various nH2O2/nTYR ratios on the kinetics of nanogelation in the inverse miniemulsion and on the reaction time are investigated by linear sweep voltammetry, while the formation of dityramine crosslinking is explored by fluorescence spectroscopy. The study is completed using dynamic light scattering measurements, nanoparticle tracking analysis, and cryogenic transmission electron microscopy to acquire comprehensive information about the formed nanoparticulate systems. With the optimal ratio nH2O2/nTYR = 2, the strategy yields in the high‐quality ~ 130 nm poly(amino acid)‐based nanogel, which is prepared in 2 h. The nanogel is colloidally stable under different temperature and pH conditions for over 168 h. Moreover, the demonstrated nanogel is noncytotoxic for HeLa cells and human primary fibroblasts and is quickly enzymatically hydrolyzed into small fragments during a biodegradation study in human blood plasma. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48725.

This work studies the influence of dip-coating parameters on self-assembly in ultra-thin films of asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymers from a 1-chloropentane solution using a combination of several experimental techniques. Small-Angle X-ray Scattering, Atomic Force Microscopy, Grazing Incidence Small Angle X-ray Scattering and Transmission Electron Microscopy were used to characterize the fabricated films. We have shown a facile fabrication route to smooth films with a wide range of thicknesses. Arranged domains of P4VP oriented perpendicularly to the substrate were observed. The domain sizes and spacing varied in the range from 13 up to 35 nm and from 39 to 115 nm, respectively.