A Doxorubicin-Glucuronide Prodrug Released from Nanogels Activated by High-Intensity Focused Ultrasound Liberated β-Glucuronidase

The poor pharmacokinetics and selectivity of low-molecular-weight anticancer drugs contribute to the relatively low effectiveness of chemotherapy treatments. To improve the pharmacokinetics and selectivity of these treatments, the combination of a doxorubicin-glucuronide prodrug (DOX-propGA3) nanogel formulation and the liberation of endogenous β-glucuronidase from cells exposed to high-intensity focused ultrasound (HIFU) were investigated in vitro. First, a DOX-propGA3-polymer was synthesized. Subsequently, DOX-propGA3-nanogels were formed from this polymer dissolved in water using inverse mini-emulsion photopolymerization. In the presence of bovine β-glucuronidase, the DOX-propGA3 in the nanogels was quantitatively converted into the chemotherapeutic drug doxorubicin. Exposure of cells to HIFU efficiently induced liberation of endogenous β-glucuronidase, which in turn converted the prodrug released from the DOX-propGA3-nanogels into doxorubicin. β-glucuronidase liberated from cells exposed to HIFU increased the cytotoxicity of DOX-propGA3-nanogels to a similar extend as bovine β-glucuronidase, whereas in the absence of either bovine β-glucuronidase or β-glucuronidase liberated from cells exposed to HIFU, the DOX-propGA3-nanogels hardly showed cytotoxicity. Overall, DOX-propGA3-nanogels systems might help to further improve the outcome of HIFU-related anticancer therapy.