Nanoparticle Formulation of Brusatol: A Novel Therapeutic Option for Cancers

Objective: Challenges to the use of brusatol for cancer chemotherapy include its reversible and short-lived effect on Nrf2 which is limited to a few hours, its non-selective inhibition of protein synthesis which renders it potentially toxic to non-cancerous cells resulting in adverse effects and poor water solubility. A nanoparticle formulation of brusatol is expected to overcome these challenges and facilitate the clinical use of brusatol. In this proof-of-principle study, a brusatol-loaded nanoparticle formulation is developed and characterized.

Method: Brusatol-loaded mPEG-PLGA nanoparticles were prepared using the oil-in-water emulsification solvent diffusion method and characterized. The drug content of the nanoparticle formulation was determined by High Performance Liquid Chromatography. Toxicity of the brusatol-loaded nanoparticles in prostate cancer cell lines was evaluated over 120 hours using the Cell Titer 96® Non- Radioactive Cell Proliferation Assay and nanoparticle uptake was studied by confocal microscopy.

Results: Scanning electron microscopy revealed the formation of nanoparticles. The average hydrodynamic particle size is 309.23 ± 2.3 nm. The in vitro release isotherm showed a biphasic and sustained release of the encapsulated drug. Data from cytotoxicity studies reveal that the nanoparticle formulation showed more toxicity compared to control brusatol solution in PC-3 and LNCaP cell lines. Confocal microscopy studies showed internalization of the nanoparticles in PC-3 cells at 6 hours. In addition, z-stack images confirm the presence of nanoparticles at various depths within the cells.

Conclusion: The stealth nanoparticle formulation allows the sustained release of brusatol with the potential to modulate its short-lived effect on Nrf2. In addition, the potential of the nanoparticle formulation to target the tumor microenvironment via the enhanced permeability and retention effect and prevent toxicity to non cancerous cells is achieved. We report the preparation and characterization of a stealth nanoparticle formulation of brusatol to facilitate the clinical use of the drug for  he treatment of cancers.