Poly(2-oxazolines) with varying alkyl chain lengths (e.g., methyl, ethyl, aryl) and molar masses have been tested for cell cytotoxicity in vitro. A standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used for the estimation of cell viability. Two monomers, 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline, were found to provide polymers with non-cytotoxic properties. The dependence of cell viability on molar mass confirmed the expected trend; the viability increased with the higher molar mass of poly(2-ethyl-2-oxazoline) (PETOX), up to 15,000 g/mol. The results obtained for the polymers with aliphatic side chains were compared with the analogues that possessed an aromatic moiety. All results confirmed low cytotoxicity of the polymers prepared by cationic polymerization of 2-alkyl- and 2-aryl-2-oxazolines, which supports their utilization in biomedical applications. Fluorescence microscopy and steady-state fluorescence were used to observe pyrene-labeled polymer interactions with living cells. Polymer accumulated within the cells was found to be dependent on polymer concentration in media. The immunoefficiency of aromatic and aliphatic oxazoline polymers and copolymers was also studied. Phagocytic and metabolic activities of macrophages were used to assess the immunosuppressive effects of the selected copolymers for possible applications in drug delivery and immunobiology. Overall, the tested polymers demonstrated no significant influences on the cellular immunological parameters.

Recently, ratiometric pH nanosensors have emerged as a robust tool for the fluorescence sensing and imaging, but there is no report of ratiometric sensors based on hyperbranched polymers for intracellular pH sensing. Herein, we describe the first example of hyperbranched polymer-based tunable fluorescent pH nanosensor with aggregation-induced emission activity, which exhibits great potential for ratiometric sensing of intracellular pH. These polymer nanoparticles can selectively accumulate in the acidic organelles of living cells by endocytosis process, and no obvious cytotoxicity was observed. The quantitative analysis of the intracellular pH values in HeLa cells was successfully conducted based on this new sensing platform. This platform provides a new choice for future developments of ratiometric fluorescent nanosensors, targeting not only protons but also a variety of other analytes of biological interest, such as metal ions, anions, and other biomolecules.

Core-shell type stars synthesized via atom transfer radical polymerization were used for the delivery of nucleic acids. The interior of the stars consisted of hyperbranched poly(arylene oxindole), while the arms were composed of poly(N,N-dimethylaminoethyl methacrylate).The length of the star arms varied in degree of polymerization (DP) from 14 to 98. The hydrodynamic radius of the structures measured in water indicated the presence of small aggregates, while isolated stars ranging in size from 14 to 29 nm were seen in organic solvent.The phase transition temperatures of the stars in water, measured in basic conditions, were shifted to lower values with increasing DP of the arms. Stable polyplexes of stars with plasmid DNA were formed. Their size varied from 300 nm to 400 nm, depending upon the DP of arms. The zeta potential of the polyplexes was positive, which facilitated their cellular uptake. The DP of the arms influenced the transfection efficiency of HT-1080 cells, demonstrating that stars are promising candidates for synthetic gene vectors.