However, non-covalent strategies appear to be better for siRNA delivery with a more significant biological response. In one study, MPG/siRNA complexes formed through stable non-covalent strategy showed successful introduction of siRNA into cultured cells and induced robust regulation of target mRNA. Furthermore, MPG/siRNA complexes have also been applied for delivery of siRNA "in vivo" into mouse blastocytes for gene regulation. MPG forms highly stable complexes with siRNA with a low degradation rate and can be easily functionalized for specific targeting, which are major advantages compared with the covalent CPP technology.