Synthesis of spin labeled ethylene glycol based polymers and study of their segmental motion

Dynamics in Controllable Stimuli-Responsive Self-Assembly of Polymer Vesicles with Stable Radical Functionality

Self-assembled polymer vesicles have emerged as exciting and promising materials for their potential application in drug delivery, but the dynamics of stimuli-responsive polymers in these areas with pendant functionality in order to understand the structure-property relationship under different physicochemical conditions is still open to discussion. In this work, nitroxide radical-containing copolymers were synthesized and utilized to investigate local dynamics in their vesicular assemblies. Herein, electron paramagnetic resonance (EPR) spectroscopy was applied to reveal the smart supramolecular vesicular structure and polymer chain dynamics in stimuli-responsive controlled assemblies by considering molecular-level interactions. These interactions and dynamics were dependent on the microenvironment of the assemblies, which might be affected by physicochemical parameters such as radical concentration, pH, redox agent, polarity, and viscosity. These observations help to accomplish quantitative insights into the stimuli-responsive colloidal vesicular assemblies. The vesicles were used as an anticancer drug carrier, which showed high drug loading efficiency (63.65%). The reduction-responsive prompt disassembly accelerated the release. Furthermore, the biocompatibility and anticancer activity were examined by cellular experiments against normal fibroblasts (L929) and human cervical cancer (HeLa) cell lines, respectively. The results demonstrate that this effort provides an easy strategy for designing controllable stimuli-responsive polymer nanosystems which promotes their promising application in cancer treatment.

Multiple-stimuli-responsiveness and conformational inversion of smart supramolecular nanoparticles assembled from spin labeled amphiphilic random copolymers

HYPOTHESIS

Organic radical polymers with tailored pendant functionalities have emerged as exciting and promising materials for their application versatility. Moreover, eco-friendly polymer-based organic nanomaterials with redox-active pendant side groups can replace the harmful heavy metal-based inorganic materials. On the other hand, self-assembled nanomaterials are of great interest and attracted more attention recently for their promising application in different advanced fields, but it is yet challenging to predict suitable hydrophilic-lipophilic balance (HLB) for stimuli-responsive random copolymers assembly due to structural irregularity. Among several experimental techniques, electron paramagnetic resonance (EPR) spectroscopy plays a unique and promising role in revealing structural and dynamic information of nanostructured radical containing materials.

EXPERIMENTS

In this study, a series of spin labeled amphiphilic random copolymers poly(methyl methacrylate-co-acrylic acid) have been synthesized and characterized by FT-IR, UV-Vis spectroscopies, TGA, DSC and water contact angle (CA) techniques. Their electrochemical properties have been determined by cyclic voltammetry (CV) in different organic solvents. EPR spectroscopy has been applied with other analytical techniques to elucidate the smart supramolecular nanoparticles (SNPs) formation, stimuli-responsiveness and structural changes through the dynamics of different molecular interactions.

FINDINGS

The structural and dynamic information of self-assembled nanoparticles have been observed to be dependent on multiple-stimuli-responsiveness in different microenvironments by applying physiological and chemical parameters such as the different concentration of radicals, pH, temperature, nature of the solvent and reducing agent. The obtained results reveal the knowledge to understand insight into the mechanism for the formation of stimuli-responsive colloidal nanoparticles assembled from amphiphilic random copolymers with apt HLB value. The CV results reveal that the charge transfer process of the nanoparticles in solution was diffusion regulated and depended on the accessibility of radicals. The radical (spin labeled) polymers offer a broad way to develop stimuli-responsive materials in various colloidal nanostructures by changing the microenvironment, appreciating their potential advanced applications in electronic devices, catalysis, stimuli-triggered drug/gene delivery and reactive oxygen species (ROS) scavenger.