Glatiramer acetate (GA) is the active substance of Teva's Copaxone drug, which contains random polypeptides used to treat multiple sclerosis. Glatiramer acetate was originally developed to emulate human myelin basic protein, which contains four different residues [alanine (A), glutamic acid (E), tyrosine (T), and lysine (K)]. We found that GA can complex, condense, and transfect plasmid DNA. Mixing the positively charged GA and the negatively charged genetic material in correct proportions produced small, stable, and highly positively charged nanoparticles. This simple GA-pDNA formulation produced high levels of transfection efficiency with low toxicity in HeLa and A549 cells (lung and cervical cancer cells). Additionally, we studied and compared the nanoparticle properties, gene expression, and cytotoxicity of K100-pDNA (high-molecular-weight polylysine) and K9-pDNA (low-molecular-weight polylysine) nanoparticles to those of GA-pDNA nanoparticles. We also studied the effect of calcium, which was previously reported to reduce the size and enhance gene expression resulting from similar polyelectrolyte complexes. Adding calcium did not reduce particle size, nor improve the transfection efficiency of GA-pDNA nanoparticles as it did for polylysine-pDNA nanoparticles. GA-pDNA nanoparticles may be prepared by mixing a genetic payload with approved GA therapeutics (e.g., Copaxone), thus offering intriguing possibilities for translational gene therapy studies.
Keywords: Copaxone; gene delivery; glatiramer acetate; polyelectrolyte; polyethylenimine; polylysine; transfection efficiency.