Chitosan Hydrogels for Synergistic Delivery of Chemotherapeutics to Triple Negative Breast Cancer Cells and Spheroids.

PURPOSE: This study aimed to develop a hydrogel system for treating aggressive triple negative breast cancer (TNBC) via kinetically-controlled delivery of the synergistic drug pair doxorubicin (DOX) and gemcitabine (GEM). A 2D assay was adopted to evaluate therapeutic efficacy by determining combination index (CI), and a 3D assay using cancer spheroids was implemented to assess the potential for translation in vivo. METHODS: The release of DOX and GEM from an acetylated-chitosan (ACS, degree of acetylation χAc = 40 ± 5%) was characterized to identify a combined drug loading that affords release kinetics and dose that are therapeutically synergistic. The selected DOX/GEM-ACS formulation was evaluated in vitro with 2-D and 3-D models of TNBC to determine the combination index (CI) and the tumor volume reduction, respectively. RESULTS: Therapeutically desired release dosages and kinetics of GEM and DOX were achieved. When evaluated with a 2-D model of TNBC, the hydrogel afforded a CI of 0.14, indicating a stronger synergism than concurrent administration of DOX and GEM (CI = 0.23). Finally, the therapeutic hydrogel accomplished a notable volume reduction of the cancer spheroids (up to 30%), whereas the corresponding dosages of free drugs only reduced growth rate. CONCLUSIONS: The ACS hydrogel delivery system accomplishes drug release kinetics and molar ratio that affords strong therapeutically synergism. These results, in combination with the choice of ACS as affordable and highly abundant source material, provide a strong pre-clinical demonstration of the potential of the proposed system for complementing surgical resection of aggressive solid tumors.

A combined approach for predicting the cytotoxic effect of drug-nanoaggregates.

We present a combined spectroscopic and computational approach aimed to elucidate the mechanism of formation and activity of etoposide nanoaggregates upon release from dextran-etoposide conjugates. Etoposide is an anticancer drug that inhibits cell growth by blocking Topoisomerase II, the key enzyme involved in re-ligation of the DNA chains during the replication process. In silico and spectroscopic analysis indicate that released etoposide nanoaggregates have a different structure, stability, and bioactivity, which depend on the pH experienced during the release. Molecular dynamics simulation and in silico docking of etoposide dimers suggest that the aggregation phenomena inhibit etoposide bioactivity, yet without drastically preventing Topoisomerase II binding. We correlated the diminished cytotoxic activity exerted by dextran-etoposide conjugates on the A549 lung cancer cells, compared to the free drug, to the formation and stability of drug nanoaggregates.