Establishing Novel Doxorubicin-Loaded Polysaccharide Hydrogel for Controlled Drug Delivery for Treatment of Pediatric Brain Tumors

Abstract

According to the National Cancer Institute, of the more than 10 million cancer survivors alive in the United States at least 270,000 were originally diagnosed under the age of 21. While the 5-year survival rates for most childhood cancers appear very promising, the long-term survival rates are still very dismal. There is significant long-term morbidity and mortality associated with treatment of childhood cancer, and the risk of these effects continues to increase years after completion of therapy. Among childhood cancer survivors the cumulative incidence of a chronic health condition is 73.4% 30 years after the original cancer diagnosis, with a cumulative incidence of 42.4% for severe, disabling, life-threatening, or death due to a chronic condition caused by the chemotherapy used to treat the initial malignancy. Brain tumors are the most prevalent solid tumor diagnosed in children, and account for 20 percent of all childhood cancer deaths. The efficacy of all chemotherapy agents can be limited by their toxicity, their instability, and their ability to be formulated into practical drug products for use in the clinical setting To address this gap, our group has developed a novel carbohydrate-based hydrogel, Amygel, that is capable of being loaded with drugs and injected directly into the site of disease. Local drug delivery using Amygel has potential to improve childhood cancer treatment outcomes and prevent the devastating effects of systemic chemotherapy exposure. Development of Amygel for clinical use has three focus areas including: increasing drug concentration at the target site; improving chemotherapy penetration through tumor tissue, and; establishing chemotherapy dosage forms for pediatric use. For this study, we formulated Amygel with dimethyl sulfoxide and integrated the chemotherapy doxorubicin (DOX). High-performance liquid chromatography (HPLC) was used to confirm the quality of DOX after hydrogel synthesis, rheology and syringability tests to characterize the mechanical properties, and performed an in vitro cytotoxicity test against the pediatric medulloblastoma cell line DAOY. On HPLC, we found that after integrating DOX into the Amygel matrix the drug maintained a strong band on the chromatograph at the same point with the same intensity as the control free drug, indicating there were no changes in the structural properties of DOX. The mechanical tests showed that there was a proportionate increase in the storage modulus of the drug-loaded hydrogels as the concentration of amylopectin increased from 3 wt% to 20 wt%, but even at 20 wt% the hydrogel remained below the medical standard for injectables that the burst force should not exceed 40 N and the sliding force below 20 N. Correlating with the rheology findings, as the concentration of amylopectin increased, and therefore the strength of the hydrogel, there was an increase in the magnitude of force required for gel injection. These mechanical studies additionally provide evidence that the mechanical stability of the gel is not dampened by the incorporation of DOX. Drug release and cytotoxicity studies demonstrated a sufficient release of DOX from the hydrogels, and that the DOX released was able to achieve significant (p<0.01) cell death.