Synthesis and characterization of poly(styrene-co-fluorescein O-methacrylate)/poly(N-isopropylacrylamide)–Fe3O4 core/shell composite particles

Switching it Up: The Promise of Stimuli-Responsive Polymer Systems in Biomedical Science

Responsive polymer systems have the ability to change properties or behavior in response to external stimuli. The properties of responsive polymer systems can be fine-tuned by adjusting the stimuli, enabling tailored responses for specific applications. These systems have applications in drug delivery, biosensors, tissue engineering, and more, as their ability to adapt and respond to dynamic environments leads to improved performance. However, challenges such as synthesis complexity, sensitivity limitations, and manufacturing issues need to be addressed for successful implementation. In our review, we provide a comprehensive summary on stimuli-responsive polymer systems, delving into the intricacies of their mechanisms and actions. Future developments should focus on precision medicine, multifunctionality, reversibility, bioinspired designs, and integration with advanced technologies, driving the dynamic growth of sensitive polymer systems in biomedical applications.

pH-Controlled fluorescence switching in water-dispersed polymer brushes grafted to modified boron nitride nanotubes for cellular imaging

pH-Switchable, fluorescent, hybrid, water-dispersible nanomaterials based on boron nitride nanotubes (BNNTs) and grafted copolymer brushes (poly(acrylic acid-co-fluorescein acrylate) - P(AA-co-FA)) were successfully fabricated in a two-step process. The functionalization of BNNTs was confirmed by spectroscopic, gravimetric and imaging techniques. In contrast to "pure" BNNTs, P(AA-co-FA)-functionalized BNNTs demonstrate intense green fluorescence emission at 520 nm. Under neutral or alkaline pH values, P(AA-co-FA)-functionalized BNNTs are highly emissive in contrast to acidic pH conditions where the fluorescent intensity is absent or low. No increase in the absorption was observed when the suspension pH was increased from 7 to 10. The functionalized BNNTs are easily taken up by human normal prostate epithelium (PNT1A) and human prostate cancer cell lines (DU145) and are suitable for further evaluation in cellular imaging applications.

Detection of in Situ Early Corrosion on Polymer-Coated Metal Substrates

Protective coating systems (PCS) are a common and facile method to protect metal substrates from corrosion. The corrosion control performance of polymer-coated metal substrates is still predominantly evaluated by visual assessment. Unfortunately, for many decades, PCS material development and performance testing has basically been a complicated process of waiting to determine which coating, in relative terms, allows corrosion to occur first from an intentionally created breach through the coating. This type of testing provides only relative ratings between PCS performance. Electrochemical methods, such as electrochemical impedance spectroscopy, each have caveats and pitfalls for qualifying or quantifying polymer-coated metal substrates. When these data are studied carefully, these measurements result in many false positive and false negative results compared with real environmental testing and the paths to failure vary dramatically. The critical issue is that these methods do not result in a scientific basis for understanding either the pathway(s) or progressive milestones toward diminished PCS performance, failure, and the loss of substrate structural integrity for coated substrates. Data supports that ultimately all PCS fail to provide the necessary substrate protection. However, to make substantive gains, scientists and engineers require a rational basis to design, engineer, test, quantify, and/or estimate service life and remaining service life and repair future generations of PCS. Our research goal was to establish a quantifiable characterization protocol (CP) that directly detected, monitored, and ideally quantified the pathway(s) and important milestones of PCS corrosion spatially and temporally, with or without defects which related with testing and assessment variables regardless of environmental severity (real, laboratory, or accelerated). We report herein the CP and the results from an embedded pH-sensitive "turn-on" fluorescent probe blended with a simplified thermoplastic model PCS. The results support that the average-localized macroscopic pH is detected and tracked, and these "molecular titrations" result in values consistent with literature pH citations for premacroscopic corrosion processes, that is, before delamination and a detectable breach. The CP results are an improvement over visual corrosion detection and yet proportional to the steel substrate corrosion. The CP results deliver extreme early detection (within minutes), spatial and temporal tracking, and potentially quantifiable performance differences for the pathways and milestones toward failure of coated substrates with validated sensitivity to variables such as defect versus defect-free films, blending solvent type(s) influence, differences from varied degrees of annealing relative to T_g (thermoplastic films), substrate topography, and preparation differences. The CP utilizes small sample areas (25 mm spheres) and gathers data in a manner designed to improve statistical relevancy, provide results within short timeframes using real-time testing, diminish materials-testing timelines, and connect results with laboratory, accelerated, and real environmental severity differences. The results support that the CP directly measured the earliest possible in situ corrosion processes using defect and defect-free simplified model PCS.

Biocompatible magnetic core-shell nanocomposites for engineered magnetic tissues

The inclusion of magnetic nanoparticles into biopolymer matrixes enables the preparation of magnetic field-responsive engineered tissues. Here we describe a synthetic route to prepare biocompatible core-shell nanostructures consisting of a polymeric core and a magnetic shell, which are used for this purpose. We show that using a core-shell architecture is doubly advantageous. First, gravitational settling for core-shell nanocomposites is slower because of the reduction of the composite average density connected to the light polymer core. Second, the magnetic response of core-shell nanocomposites can be tuned by changing the thickness of the magnetic layer. The incorporation of the composites into biopolymer hydrogels containing cells results in magnetic field-responsive engineered tissues whose mechanical properties can be controlled by external magnetic forces. Indeed, we obtain a significant increase of the viscoelastic moduli of the engineered tissues when exposed to an external magnetic field. Because the composites are functionalized with polyethylene glycol, the prepared bio-artificial tissue-like constructs also display excellent ex vivo cell viability and proliferation. When implanted in vivo, the engineered tissues show good biocompatibility and outstanding interaction with the host tissue. Actually, they only cause a localized transitory inflammatory reaction at the implantation site, without any effect on other organs. Altogether, our results suggest that the inclusion of magnetic core-shell nanocomposites into biomaterials would enable tissue engineering of artificial substitutes whose mechanical properties could be tuned to match those of the potential target tissue. In a wider perspective, the good biocompatibility and magnetic behavior of the composites could be beneficial for many other applications.

Polymer grafted magnetic nanoparticles for delivery of anticancer drug at lower pH and elevated temperature

Efficient and controlled delivery of therapeutics to tumor cells is one of the important issues in cancer therapy. In the present work, a series of pH- and temperature-responsive polymer grafted iron oxide nanoparticles were prepared by simple coupling of aminated iron oxide nanoparticle with poly(N-isopropylacrylamide-ran-poly(ethylene glycol) methyl ether acrylate)-block-poly(acrylic acid) (P(NIPA-r-PEGMEA)-b-PAA). For this, three water soluble block polymers were prepared via reversible addition fragmentation transfer (RAFT) polymerization technique. At first, three different block copolymers were prepared by polymerizing mixture of NIPA and PEGMEA (with varying mole ratio) in presence of poly(tert-butyl acrylate) (PtBA) macro chain transfer agent. Subsequently, P(NIPA-r-PEGMEA)-b-PAA copolymers were synthesized by hydrolyzing tert-butyl acrylate groups of the P(NIPA-r-PEGMEA)-b-PtBA copolymers. The resulting polymers were then grafted to iron oxide nanoparticles, and these functionalized nanoparticles were thoroughly characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), zeta potential measurements, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) and Fourier transform infrared spectroscopy (FTIR). Doxorubicin (DOX), an anti-cancer drug, was loaded into the polymer coated nanoparticles and its release behavior was subsequently studied at different pH and temperatures. The drug release pattern revealed a sustained release of DOX preferentially at the desired lysosomal pH of cancer cells (pH 5.0) and slightly above the physiological temperature depending upon the composition of the copolymers. The potential anticancer activity of the polymer grafted DOX loaded nanoparticles were established by MTT assay and apoptosis study of cervical cancer ME 180cells in presence of the nanoparticles. Thus, these particles can be utilized for controlled delivery of anticancer drugs at the desired lysosomal pH and/or by slightly heating the cells using magnetic hyperthermia.

Hydrogel adsorbents of poly(N-isopropylacrylamide-co-methacryloyloxymethyl-12-crown-4) for Li+ recovery prepared by droplet microfluidics

This article describes the synthesis and application of hydrogel adsorbents for lithium ion (Li⁺) recovery from seawater.