Figure 2.

Schematic representation of the LHRH-targeted, PPIG4 dendrimer-based nanoplatform for siRNA delivery. The developed nanoparticles contain four components: 1) DJ-1 siRNA, as suppressors of the corresponding mRNA in the ovarian cancer cells; 2) PPIG4 dendrimers as carriers for DJ-1 siRNA; 3) PEG, as an enhancer of nanoparticles stability and biocompatibility and 4) LHRH peptide, as a targeting moiety to the ovarian cancer cells. The approach for preparation of the nanoplatform consists of the following steps: 1) Complexation of negatively charged DJ-1 siRNA by the positively charged PPIG4 into nanometer-sized complexes via electrostatic interactions; 2) Modification of the PPIG4-siRNA complexes with hydrophilic polymer by conjugation of PEG to PPIG4 amino groups on the nanoplatform surface; (3) Conjugation of LHRH peptide to the distal end of PEG layer through the maleimide (MAL) groups on the PEG and the thiol groups in LHRH peptide. Due to the electrostatic interactions, the positively-charged dendrimer and negatively-charged siRNA molecules spontaneously self-assemble into nanoparticles. An excess of dendrimers results in encapsulation of siRNA molecules inside of the nanoparticles and provides net positive charge on the nanoparticle surface, which in turn protect the siRNA against serum nuclease degradation and facilitate cellular internalization.