Preparation and Characterization of PLA-PEG-PLA/PEI/DNA Nanoparticles for Improvement of Transfection Efficiency and Controlled Release of DNA in Gene Delivery Systems

Tri-block poly (lactide) poly(ethylene glycol) poly(lactide) (PLA–PEG–PLA) copolymers are among the most attractive nano-carriers for gene delivery into mammalian cells, due to their biocompatibility and biodegradability properties. However, the low efficiency of the gene delivery by these copolymers is an obstacle to gene therapy. Here, we have investigated nanoparticles formulated using the polyethylenimine (PEI) associated with PLA-PEG-PLA copolymer for efficient DNA encapsulation and delivery. PLA-PEG-PLA/DNA and PLA-PEG-PLA/PEI/DNA nanoparticles with different concentrations of PEI were prepared by the double emulsion-solvent evaporation technique. PLA-PEG-PLA/PEI/DNA were characterized for particle size, zeta potential, morphology, biocompatibility, DNA protection, DNA release, and their ability for gene delivery into MCF-7 cells. We found that enhancing the mass ratio of PEI: (PLA-PEG-PLA) (w/w %) in the PLA-PEG-PLA/PEI/DNA nanoparticles results in an increase in particles size, zeta potential, encapsulation efficiency, and DNA release. The electrophoretic analysis confirmed that the PLA-PEG-PLA and PLA-PEG-PLA/PEI could protect DNA from ultrasound damage and nuclease degradation. MTT assay showed that the PLA-PEG-PLA/PEI/DNA had low cytotoxicity than PEI complexes. The potential of PLA-PEG-PLA/PEI/DNA nanoparticles with different concentrations of PEI as a non-viral gene delivery vector for transferring pEGFP-N1 to MCF-7 cells was examined by fluorescent microscopy and flow cytometry. The flow cytometry analysis revealed that by increasing the mass ratio of PEI: (PLA-PEG-PLA) (w/w %) in PLA-PEG-PLA/PEI/DNA nanoparticles, the efficiency of the gene delivery into MCF-7 cells was improved. The results also demonstrated that PLA-PEG-PLA/PEI/DNA nanoparticles in the serum medium improved the efficiency of gene delivery more than two-fold, compared to PEI/DNA complex.