Redox-active Microcapsules as Drug Delivery System in Breast Cancer Cells and Spheroids

The purpose of our study was to develop new delivery systems for drugs effective against breast cancer by using biodegradable and biocompatible capsules. Redox-active microcapsules based on thiolated polymethacrylic acid (PMA) were employed. The interaction of these PMASH capsules with breast cancer cells and the mechanism of their internalization was investigated. PMASH biocompatibility was evaluated by MTT assay. To analyze their potential as drug carrier, we incorporated doxorubicin into the capsules. Confocal microscopy observations showed the presence of capsules inside the cells. Although some drug molecules still appeared co-localized with PMASH capsules, strong doxorubicin fluorescence was observed both in the cytoplasm and nucleus, indicating the disassembling of the capsule into PMASH-drug conjugate after internalization. These results were confirmed by both flow cytometry (time course of capsule uptake) and scanning electron microscopy. PMASH capsules were also internalized in 3D cell structures (spheroids) suggesting their potential use as drug delivery system for treatment of