Poly(2-dimethylaminoethyl Methacrylate) Based Nanocarriers And Delivery Efficiency For Sirna In Vitro And In Vivo

The achievement of the in vivo function of siRNA relies on the effectivedelivery of carriers. In order to provide information on the ideal polymer design forsiRNA delivery, siRNA delivery systems with poly(2-dimethylaminoethylmethacrylate)(PDMAEMA) as cationic segments, polycaprolactone (PCL) ashydrophobic segments, and methoxy poly(ethylene glycol)(PEG) as hydrophilicsegments, were developed in this manuscript.Firstly, two kinds of self-assembly nanoparticles formed by block copolymermPEG-PCL-b-PDMAEMA (PECbD) and comb copolymermPEG-PCL-g-PDMAEMA (PECgD), were used to deliver siRNA for in vitro and invivo studies. At the same DP of DMAEMA, PECgD NPs/siRNA complexespossessed higher zeta potentials than PECbD NPs/siRNA complexes, which may bethe reason that PECgD NPs/siRNA complexes can deliver more siRNA into thecytoplasm and lead to higher in vitro luciferase and lamin A/C silencing efficiencythan PECbD NPs/siRNA complexes. The in vivo imaging measurement confirmedthat siRNA could be delivered to lungs, livers, pancreas and HeLa-Luc tumors moreefficiently by PECgD NPs than PECbD NPs.Based on the previous work, a kind of sheddable nanoparticles with micellearchitecture for siRNA delivery were fabricated by using an intracellular-activatedpolycation-detachable copolymer (PECssD), which was prepared by introducinghighly reducing environments-responsive disulfide linkages between PEGylated PCLand the grafted polycation PDMAEMA. Especially, the cleavage of the disulfidelinkages in the intracellular microenvironment and the subsequently dissociation ofthe PDMAEMA/siRNA polyplexes from the PEGylated PCL cores ofPECssD/siRNA micelleplexes were confirmed, which facilitated the endosomalescape and the efficient release of siRNA. As a result, the distribution of siRNA incytoplasm was enhanced and subsequently promoting the efficiency of siRNA in genesilencing. Furthermore, systemic administration of the nanoparticles carrying siPlk1induced a tumor suppression effect in the HeLa-Luc xenograft murine model.The above PDMAEMA based comb polymer delivery systems existed certaintoxicity. Therefore, in order to reduce the toxic and side effect caused by cationicpolymer, two strategies were carried out.A low cytotoxic and high efficiency delivery system is needed for theapplication of siRNA delivery. For these prerequisites, cationic polymer-mesoporous silica nanoparticles (ssCP-MSNs) were prepared by surface functionalizedmesoporous silica nanoparticles with disulfide bonds cross-linked PDMAEMA. Thein vitro and in vivo evaluations were performed. The ssCP-MSNs showed excellentbinding capacity for siRNA, enhancement in the cell uptake and cytosolic availabilityof siRNA. Promoted RNA interference was observed in HeLa-Luc cells, which wasequal to Lipofectamine2000. Significantly, compared to Lipofectamine2000, thessCP-MSNs were more biocompatible with low cytotoxicity even non-cytotoxicityand promotion of cell proliferation to HeLa-Luc cells. The in vivo systemicdistribution studies certificated ssCP-MSNs/siRNA could prolong the duration ofsiRNA in vivo after intravenous injection. Encouragingly, with the ability ofdelivering siRNA to tumor, ssCP-MSNs/siRNA showed tumor suppression effect inthe HeLa-Luc xenograft murine model after intravenous injection.The second strategy was to delevop a carrier system without positive charge. Weused mPEG-PNIPAM, DC-Chol and siRNA to design a thermo-responsivelytriggered on-demand siRNA release system. The cold shock changed the morphologyand size of nanoparticles, leading to the facilitated siRNA release from nanoparticlesin vitro. The carrier showed potent gene silencing efficacy in HeLa-luc cells, whichwas further enhanced by a cold shock. In vivo distribution showed most of siRNA wasaccumulated in kidney instead of RES.