Polymeric Micelles for siRNA Delivery - RNA Interference from Biology to Therapeutics - page 173

Fig. 8.8 Stimuli-responsive groups for the design of smart polymeric micelles. Adapted with
permission from [ 78 ] . Copyright 2011 American Chemical Society
are not co-localized with green, the siRNA is already released into the cytoplasm.
As a control, a non-charge-conversional polymer was used (PEG-PAsp(DET-Car)).
A special feature of this calcium phosphate hybrid system allowed the slow disas-
sembly of calcium crystals in a low ionic compartment, which resulted in the release
of siRNA after 24 h in noncharge conversional polymers as well [ 53 ] , although not
as efficiently as the CCP containing system.
Among the pH-sensitive groups, the disulfide linkage is well characterized as a
chemical bond that is cleaved specifically in the cytoplasm. Once it is reduced by
glutathione (GSH), whose intracellular concentration is much higher than the extra-
cellular, it allows the disassembly of the particles carrying siRNA that are stabilized