Synthesis of Magneto-Controllable Polymer Nanocarrier Based on Poly(N-isopropylacrylamide-co-acrylic Acid) for Doxorubicin Immobilization

Effect of Polymer Network Architecture on Adsorption Kinetics at Liquid-Liquid Interfaces: A Comparison Between Poly(NIPAM-co-AA) Copolymer Microgels and Interpenetrating Network Microgels

Understanding the adsorption features of polymer microgels with different chemical compositions and structures is crucial in studying the mechanisms of respective emulsion stabilization. Specifically, the use of stimuli-responsive particles can introduce new properties and broaden the application range of such complex systems. Recently, we demonstrated that emulsions stabilized by microgels composed of interpenetrating networks (IPNs) of poly-N-isopropylacrylamide (PNIPAM) and polyacrylic acid (PAA) exhibit higher colloidal stability upon heating compared to PNIPAM homopolymer and other relevant PNIPAM-based copolymer counterparts. In the present work, using pendant drop tensiometry, we studied the evolution of water-tetradecane interfacial tension during the adsorption of PNIPAM-PAA IPN particles, comparing them with single-network P-(NIPAM-co-AA) and PNIPAM microgels. The results showed that, despite having the same chemical composition, copolymer particles exhibit completely different adsorption behavior in comparison to other microgel architectures. The observed disparity can be attributed to the nonuniform distribution of charged acrylic acid groups within the P-(NIPAM-co-AA) network obtained through precipitation polymerization. Oppositely, the presence of IPN architecture provides a uniform distribution of different monomers inside respective microgels. Additionally, hydrogen bonding between PNIPAM and PAA subchains appears to reduce the electrostatic energy barrier, enhancing the ability of IPN particles to successfully cover the liquid interface. Overall, our findings confirm the efficiency of using PNIPAM-PAA IPN microgels for the preparation of oil-in-water emulsions and their stability, even when the temperature rises above the lower critical solution temperature of PNIPAM.

Redox-Active Water-Soluble Low-Weight and Polymer-Based Anolytes Containing Tetrazine Groups: Synthesis and Electrochemical Characterization

Polymer-based aqueous redox flow batteries (RFBs) are attracting increasing attention as a promising next-generation energy storage technology due to their potential for low cost and environmental friendliness. The search for new redox-active organic compounds for incorporation into polymer materials is ongoing, with anolyte-type compounds in high demand. In response to this need, we have synthesized and tested a range of new water-soluble redox-active s-tetrazine derivatives, including both low molecular weight compounds and polymers with different architectures. S-tetrazines are some of the smallest organic molecules that can undergo a reversible two-electron reduction in protic media, making them a promising candidate for anolyte applications. We have successfully modified linear polyacrylic acid and poly(N-isopropylacrylamide-co-acrylic acid) microgels with pendent 1,2,4,5-tetrazine groups. Electrochemical testing has shown that the new tetrazine-containing monomers and, importantly, the water-soluble redox polymers, both linear and microgel, demonstrate the chemical reversibility of the reduction process in an aqueous solution containing acetate buffer. This expands the range of water-soluble anodic materials suitable for water-based organic RFBs. The reduction potential value can be adjusted by changing the substituents in the tetrazine core. It is also worth noting that the choice of electrode material plays an important role in the kinetics of the tetrazine reaction: the use of carbon electrodes is particularly beneficial.

Theoretical Study of Microgel Functional Groups' Mobility

Polymer microgels, micrometer-sized cross-linked polymer particles, are considered to be a promising type of advanced materials for a wide range of applications. To enhance the microgels' applicability, it is essential to incorporate various functional groups into a microparticle polymer network. Yet, the availability of functional groups for the interaction with surroundings depends strongly on the properties of the polymer network and has a great impact on further effective usage. In this theoretical study, we address this question and, with the help of coarse-grained molecular dynamics computer simulations, assess the segmental mobility and accessibility of functional groups bound to polymer network depending on microgel architecture and solvent quality. Additionally, we evaluate the minimum number of functional groups needed to facilitate the hopping mechanism between the functional groups (i.e., charge transfer). As an example of practical implementation of the obtained results, we estimate the optimal network topology for redox-active microgels to provide the maximum charge capacity for the dispersion electrolyte in redox-flow batteries.

Ag2O-Containing Biocidal Interpolyelectrolyte Complexes on Glass Surfaces-Adhesive Properties of the Coatings

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.

Ensembles of carboxymethyl cyclodextrins on cationic liposomes as highly efficient nanocontainers for the delivery of hydrophobic compounds

The increase of payload is one of the key tasks in creation of nanocontainers for the delivery of bioactive substances (BAS). In this work the adsorption of anionic carboxymethyl cyclodextrins (CMCDs) on the surface of cationic liposomes was studied as mechanism of formation of capacious nanocontainers for the encapsulation and delivery of hydrophobic BAS. The formation and physico-chemical characteristics of complexes were studied by means of laser microelectrophoresis, dynamic light-scattering, conductometry and atomic force microscopy (AFM). As a model, bioactive molecule hydrophobic curcumin was chosen for the investigation. The encapsulation of curcumin was controlled by UV-Vis spectrometry. Interaction of CMCDs/liposomes complexes with model cell membranes was visualized by fluorescent microscopy. Finally, cytotoxicity of nanocontainers was studied by MTT-test. It was estimated that colloid stable complexes with net positive charge could contain up to 2.5÷5 CMCD molecules per one cationic lipid. Incorporation of curcumin in CMCDs does not change the character of interaction of oligosaccharides with liposomal membranes of individual liposome. CMCDs/liposomes complexes adsorb on model cell membranes without significant loss of CMCD molecules. This fact in addition to low cytotoxicity of cationic CMCDs/liposomes complexes demonstrates potential of their application as nanovehicles for the delivery of BAS.