Paclitaxel-Conjugated Virus Nanoparticles for Targeted Breast Cancer Treatment

A critical difficulty in designing nanotherapeutics is in developing highly targeted platforms that can reach target sites with high efficiency. Purely rational improvements to nanoparticle design can be extremely difficult. Additionally, due to the high degree of heterogeneity in breast tumors within a patient as well as between patients, there is currently no one biomarker available that specifically identifies all breast cancer cells.  To overcome these obstacles, we are developing a novel drug delivery system based on adeno-associated virus (AAV) nanoparticles to deliver chemotherapeutic agents specifically to breast cells and limit the exposure of drugs to normal non-breast tissues. AAV is a 25 nm virus nanoparticle that is currently in clinical trials for a variety of gene therapy applications. The AAV capsid is a supramolecular assembly of 60 protein subunits, lending itself well to multivalent conjugation of drug molecules. We have used directed evolution to create virus nanoparticles that can specifically bind breast tissue.  Paclitaxel (taxol), chemically modified with N-hydroxysuccinimide, was covalently attached to the virus capsid surface. Free taxol was successfully removed from the AAV-taxol conjugation.  AAV-taxol was assayed for degree of conjugation with UV-vis, Electrospray Ionization Mass Spectrometry (ESI-MS) and immunoblotting; proper capsid assembly with Enzyme-Linked Immunosorbent Assay (ELISA) and Transmission Electron Microscopy (TEM); genomic packaging with Quantitative Polymerase Chain Reaction (Q-PCR); and cytotoxicity with cell viability assays. This work will offer superior targeting of breast tissues and provide greater drug payload. It has the potential of significantly decreasing the morbidity associated with systemic chemotherapy.