Cellular response to star-shaped polyacids. Solution behavior and conjugation advantages

The nanosized (∼10 nm in 0.01 M PBS and 210 nm in water) star-shaped polymethacrylates with various content of pendant carboxyl groups were characterized via basic physicochemical and biological properties toward their use as drug carriers for intravenous administration. The carboxyl groups in polymer were employed to conjugate fluorescein (FA) or doxorubicin (DOX) via amide bond formation. In case of DOX, the conjugation efficiency was higher (4.0–16.0%) than of FA conjugation (1.5–4.5%) for corresponding copolymers. The solubility of conjugates strongly depended on the type of attached compound, that is free carriers and their FA conjugates were water-soluble, whereas DOX conjugates were insoluble in water. Cytotoxicity tests performed on model fibroblast and epithelial cell lines showed that negatively charged copolymers (ZP ranged from −75 to −25 mV) were slightly toxic for normal cells (NHDF) and non-toxic for cancer cell lines (HCT-116 and MCF-7/R). The copolymer dose equal to 125 μg/mL resulted in cell viability 118% towards NHDF and 90% for HCT116 cells. The internalization of a representative polymer-fluorescein conjugate by HCT-116 and its accumulation in cytoplasm was proven via fluorescence microscopy. MMA/MAA stars showed no adverse effect on HCT-116 cells, hence fluorescein-tagged polymers might be applied as fluorescence probes for in vitro imaging, whereas doxorubicin-tagged polymers might be developed as a new polymeric drug carriers.