(584am) Uptake, Co-Localization and Cytotoxicity of Acid-Labile Pegylated Poly(amidoamine)-Doxorubicin Conjugates in An in Vitro Model of the Lung Adenocarcinoma

Lung cancer is the leading cause of cancer death among both men and women in the United States.  Adenocarcinoma accounts for more than 40% of all lung cancer cases.  Doxorubicin (DOX) is an FDA-approved chemotherapeutic that has been widely used as primary anticancer drug in the treatment of a variety of cancers, including lung adenocarcinoma.  However, rapid elimination, uncontrolled release, systemic distribution, and life-threatening cardiotoxicity, reduce tumor cytotoxicity and thereafter curb the application of DOX and other anti-cancer therapeutics in the treatment of several patient populations suffering from lung cancer.  Therefore, the development of DOX delivery carriers (and carriers for other anti-cancer therapeutics for that matter) that can achieve controllable release, reduce toxicity to healthy tissue, and prolonged blood circulation times would be of great relevance in the treatment of lung adenocarcinoma.

In this work, a series of PEGylated poly(amidoamine) dendrimer nanocarriers with acid-labile and acid-nonlabile DOX conjugates were synthesized and characterized.  We employed a two-step PEGylation strategy (pre-PEGylation followed by supplementary PEGylation) to increase the DOX payload.  We investigated the impact of pH (neutral and acidic pH), PEGylation density (low, medium and high) and number of DOX conjugates (low and medium) on the release of DOX from the dendrimer nanocarrier, the kinetics of carrier uptake, intracellular release kinetics of DOX from the nanocarrier, and toxicity in an alveolar adenocarcinoma cell line (A549). PEGylation retards the release of DOX in acidic medium, and also intracellularly, as determined by co-localization studies with confocal microscopy.  We also observed that the kinetics of cellular entry of the nanocarrier with DOX increased significantly compared to free DOX, as determined by flow cytometry.  At the highest PEGylation density, the rate of internalization of the nanocarrier containing DOX was even higher than that of free DOX.  PEGylation density also affects cytotoxicity as seen by an increase in IC₅₀ for DOX-conjugated dendrimer compared to free DOX, due to the controlled release of the therapeutic.