RESUMO
Polystyrenesulfonate (PSS), as one of the most important categories of polyelectrolytes, has received increasing attention due to its great potential in the applications of energy- and biomedical-related fields. However, most of the previous studies only focused on linear PSS and its derivatives, but little attention was paid to nonlinear topological PSSs. So far, the synthesis of nonlinear PSSs with well-defined structures is still a challenging task, and the main obstacle lies in the stability issue of functional chemical linkages during the sulfonation process of polystyrene (PS) precursors, such as the carbon-oxygen-containing linkages. Herein, by rationally designing the chemical structure of the functional linkage, we introduce a versatile and efficient strategy for the preparation of topological PSSs. Specifically, by embedding firm triazole linkages (without carbon-oxygen linkages) into the backbone structure of cyclic and hyperbranched PS precursors, the backbone and functional linkages are found to present excellent chemical stability under certain sulfonation conditions, which eventually lead to the successful preparation of cyclic and hyperbranched PSSs. By using two sets of PSS samples with varied molar masses, the scaling relations between the number of repeating units and the sedimentation coefficient are established for both linear and cyclic PSSs. We believe that our proposed synthetic strategy is universal and could be extended to the synthesis of other types of topological PSSs.
RESUMO
Reduction-responsive polymer micelles are highly promising drug carriers with better tumor therapeutic effect, which can be achieved by controlled drug release under stimulation. Gold nanorods (AuNRs) have attracted considerable attention due to their unique optical and electronic properties when used for biomedical applications. Herein, the lipoic-acid-functionalized reduction-responsive amphiphilic copolymer poly(ε-caprolactone)-b-poly[(oligoethylene glycol) acrylate] (LA-PCL-SS-POEGA) with a disulfide group between the two blocks was prepared to modify AuNRs via Au-S bonds. The size and morphology of AuNRs@LA-PCL-SS-POEGA were measured by dynamic laser light scattering (DLS) and transmission electron microscopy (TEM) methods. The stabilities of AuNRs@LA-PCL-SS-POEGA in different types of media were studied by UV/vis spectroscopy and DLS techniques. The results show that AuNRs@LA-PCL-SS-POEGA gradually aggregate in a concentrated salt solution containing 150 mM dithiothreitol (DTT), but exhibit high stability in a non-reducing environment. Near infrared (NIR)-induced heating of AuNRs@LA-PCL-SS-POEGA was investigated in an aqueous solution under NIR laser irradiation (808 nm), revealing that AuNRs@LA-PCL-R-POEGA maintain excellent photothermal conversion efficiency after modification. When compared with non-reduction responsive AuNRs@LA-PCL-CC-POEGA, the in vitro internalization of AuNRs@LA-PCL-SS-POEGA demonstrates that the reduction-responsive polymer could enhance the cellular uptake of nanoparticles measured by inductively coupled plasma mass spectrometry (ICP-MS) and TEM.
