Tailoring Polymer-Based Nanoassemblies for Stimuli-Responsive Theranostic Applications

Polymer assemblies on the nanoscale represent a powerful toolbox for the design of theranostic systems when combined with both therapeutic compounds and diagnostic reporting ones. Here, recent advances in the design of theranostic systems for various diseases, containing-in their architecture-either polymers or polymer assemblies as one of the building blocks are presented. This review encompasses the general principles of polymer self-assembly, from the production of adequate copolymers up to supramolecular assemblies with theranostic functionality. Such polymer nanoassemblies can be further tailored through the incorporation of inorganic nanoparticles to endow them with multifunctional therapeutic and/or diagnostic features. Systems that change their architecture or properties in the presence of stimuli are selected, as responsivity to changes in the environment is a key factor for enhancing efficiency. Such theranostic systems are based on the intrinsic properties of copolymers or one of the other components. In addition, systems with a more complex architecture, such as multicompartments, are presented. Selected systems indicate the advantages of such theranostic approaches and provide a basis for further developments in the field

Mechanically induced cis-to-trans isomerization of carbon–carbon double bonds using atomic force microscopy

Cis-to-trans isomerization of carbon–carbon double bonds can be induced by the application of mechanical force. Using single molecule force spectroscopy by means of atomic force microscopy (AFM) we pulled polymer molecules which contained cis double bonds in the backbone. In the force versus extension profiles of these polymers, a sudden extension increase is observed which is due to the conversion of shorter cis isomers into longer trans isomers. The added length to the polymer results in relaxation in probed force. We find that the isomerization occurs at forces of 800 ± 60 pN, independent of AFM tip and solid substrate chemistries. Investigation of similar polymers which exclusively contained single bonds in the backbone showed no evidence of a similar transition

Synthesis and properties of poly(norbornene)s with lateral aramid groups

This paper deals with the synthesis and investigation of comb-like poly(norbornene)s carrying lateral rod-like aramid groups. Two types of norbornene-based monomers were synthesized and copolymerized with a norbornene carrying an aliphatic side chain using ring opening metathesis polymerization (ROMP). The new monomers contain aramid derivatives that display different types of non-covalent interactions. The first monomer contains linear tri(p-benzamide)s, which exhibit the typical H-bonds that aramids are known for. The second monomer features tri(p-benzamide)s with bulky ethylhexyloxy side-chains, which suppress intermolecular hydrogen bonding and favor π–π-stacking. The monomers were copolymerized in various ratios and the influence of the composition on the material properties was investigated using Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA), and powder X-ray diffraction (XRD) experiments. The results show that the glass transition temperature increases proportionally with the concentration of the H-bonding monomer

Metal cation responsive anionic microgels: behaviour towards biologically relevant divalent and trivalent ions

Anionic poly(vinylcaprolactam- co -itaconicacid- co -dimethylitaconate) microgels were synthesized via dispersion polymerization and their responsiveness towards cations, namely Mg 2+ , Sr 2+ , Cu 2+ and Fe 3+ , was investigated. The itaconic moieties chelate the metal ions which act as a crosslinker and decrease the electrostatic repulsion within the network, leading to a decrease in the gel size. The responsiveness towards the metal ion concentration has been studied via dynamic light scattering (DLS) and the number of ions bonded within the network has been quantified with ion chromatography. Through the protonation of the carboxylate groups in the gel network, their interaction with the cations is significantly lowered, and the metals are consequently released back in solution. The number of ions released was assessed also via ion chromatography for all four ions, whilst Mg 2+ was also used as a model ion to display the reversibility of the system. The microgels can bond and release divalent cations over multiple cycles without undergoing any loss of functionality. Moreover, these gels also selectively entrap Fe 3+ with respect to the remaining divalent cations, opening the possibility of using the proposed gels in the digestive tract as biocompatible chelating agents to fight iron overaccumulation