LCST behavior of poly(2-ethyl-2-oxazoline) containing diblock and triblock copolymers

Opportunities and Challenges of Switchable Materials for Pharmaceutical Use

Switchable polymeric materials, which can respond to triggering signals through changes in their properties, have become a major research focus for parenteral controlled delivery systems. They may enable externally induced drug release or delivery that is adaptive to in vivo stimuli. Despite the promise of new functionalities using switchable materials, several of these concepts may need to face challenges associated with clinical use. Accordingly, this review provides an overview of various types of switchable polymers responsive to different types of stimuli and addresses opportunities and challenges that may arise from their application in biomedicine.

A review of stimuli-responsive polymeric micelles for tumor-targeted delivery of curcumin

Despite a potential drug with multiple pharmacological activities, curcumin has disadvantages of the poor water solubility, rapid metabolism, low bioavailability, which considerably limit its clinical application. Currently, polymeric micelles (PMs) have gained widespread concern due to their advantageous physical and chemical properties, easy preparation, and biocompatibility. They can be used to improve drug solubility, prolong blood circulation time, and allow passive targeted drug delivery to tumor through enhanced penetration and retention effect. Moreover, studies focused on tumor microenvironment offer alternatives to design stimulus-responsive smart PMs based on low pH, high levels of glutathione, altered enzyme expression, increased reactive oxygen species production, and hypoxia. There are various external stimuli, such as light, ultrasound, and temperature. These endogenous/exogenous stimuli can be used for the research of intelligent micelles. Intelligent PMs can effectively load curcumin with improved solubility, and intelligently respond to release the drug at a controlled rate at targeted sites such as tumors to avoid early release, which markedly improves the bioavailability of curcumin. The present review is aimed to discuss and summarize recent developments in research of curcumin-loaded intelligent PMs based on endogenous and exogenous stimuli, and facilitates the development of novel delivery systems for future research.

SILICON-CONTAINING OLIGOMERIC AZOINITIATORS IN THE SYNTHESIS OF BLOCK COPOLYMERS

A solvothermal synthetic pathway and functional polymer styabilizers was used for synthesis of fine silver structures of different architecture. Using polyvinylpyrrolidone as a stabilizer silver micronized wires with a diameter of 3,8–4,2 μm and aspect ratio of up to 30 were prepared. XRD technique was applied for qualitative determination of silver metal structures. New thermoresponse composite hydrogels with a structure of semi-IPNs were prepared from cross-linked polyvinyl alcohol, linear highly hydrophilic poly(2-ethyl-2-oxazoline) (PEtOx) and as-synthesized silver micro-sized wires. Effect of a structure and a composition of the polymer matrix, and inorganic anisotropic filler on structure arrangement of composite hydrogels were evaluated by DMA studies. A presence of linear hydrophilic PEtOx and anisotropic metal filler in PVA matrix reduces storage modulus Е’ from 275 to 222–230 MPa and increases loss modulus Е” up to 45,5 MPa at room temperature measurements that partially initiated by poor structuration ability of the composites under high solvation level of polymer matrices. Increasing temperature leads to redistribution of hydrogen bonds network and hybridization of PVA nad PEtOx macrochains and enhances energy dissipation ability of unfilled hydrogel. A filler due to conjugation with amine-functionalized PEtOx chains and its localization closed to a surface of metal supresses polymer-polymer interactions and elasticity parameters of composite matrix drops down. As a result, diffusion and permeability coefficients of composite hydrogels reaches 1,06–1,52·10–9 cm2/s and 0,83–1,09·10-9 g/(cm·s), respectively, that higher in comparison with cross-linked PVA matrices. A presence of hydrogen bonds of different energy in hydrogels provides an appearance of multiple relaxation transitions due to different macrochain mobility in a bulk of polymer matrix. Differences of temperature interval of LCTS for hydrogels were found from analysis Е”(T)/dT (62–70 °С) and Δχ(T)/dT (67–70 °С) dependencies are interrelated with kinetic pecularities of diffusion processes that are able to suppress a phase separation at the temperatures closed to LCTS. Phase inversion processes for hydrogel containing 5 % of PEtOx at LCTS are accompanied by desorption of 32–73 % of sorbate. Moreover, thermoresponsive properties of the hydrogels filled with metallic silver wires are higher than that of the unfilled semi-IPNs.

Understanding the effect of monomer structure of oligoethylene glycol acrylate copolymers on their thermoresponsive behavior for the development of polymeric sensors

Oligoethylene glycol acrylate (OEGA) polymers are a class of thermoresponsive polymers. Three new OEGA monomer combinations were investigated, which revealed three different types of thermoresponsive behavior as a function of copolymer composition.