Stimuli-sensitive and degradable capsules as drug carriers with decreased toxicity against healthy cells

Novel hollow hydrogel capsules, stimuli-sensitive and degradable polymer-based, were synthesized. These capsules were prepared by a facile method based on precipitation polymerization of N-isopropylacrylamide (NIPA) with crosslinking agent -N,N′-bis(acryloyl)cystine (BISS) on -C = C- modified sacrificial dimethyldiethoxysilane emulsion templates (DMDES). The capsules were formed after the removal of the silica core by ethanol. The presence of carboxylic groups from BISS gave the capsules stability and sensitivity to pH. The presence of the -S-S- groups, in turn, made the polymer network susceptible to degradation by the reducing agent glutathione, which is present at elevated concentration in some cancer cells. The anticancer drug Doxorubicin (DOX) was loaded and released from capsules after their degradation. The highest release of drug was observed at 37 °C and cGSH = 40 mM, which corresponds well with the conditions present in most cancer cells. The MTT assay indicated that the DOX-loaded capsules were more cytotoxic against MCF-7 breast cancer cells than DOX alone. Importantly, they were less toxic against the healthy MCF-10A cells. The unloaded gel nanoparticles did not inhibit proliferation of the cells.