Polyethylenimines (PEIs) and PEG-PEIs for the therapeutic application of siRNA in vivo

摘要

An essential prerequisite for the therapeutic application ofRNA interference (RNAi) in vivo is the efficient deliveryof siRNAs. Polyethylenimines (PEIs) are water-solublesynthetic polymers with protonable amino groups whichare able to form non-covalent complexes with siRNAs,mediating their protection against nucleolytic degradationas well as cellular uptake and intracellular release. Criticalfor siRNA delivery are the PEIs or PEI derivatives beingused, including poly(ethylene glycol) (PEG)-grafted PEIs.Here, we assess the in vitro and in vivo behavior of a largeset of various PEG-PEI/siRNA complexes with differentdegrees and patterns of PEGylation. We show that, asopposed to DNA transfection efficacies, siRNA-mediatedgene targeting in vitro is less dependent on certainPEGylation patterns of PEI, thus extending the panel ofPEG-PEIs available for siRNA delivery. Biodistributionstudies in vivo reveal distinct siRNA delivery profilesgoverned by the route of injection and the degree andpattern of PEI PEGylation. Complexes based on differentPEG-PEIs vary with regard to blood circulation time,tissue uptake and siRNA biodistribution. A more detailedanalysis reveals that the induction of erythrocyteaggregation and hemorrhage in the lung upon I.v.Injection are critical parameters. Furthermore, in liver andspleen, but not in lung and kidney, siRNA levels aredependent on macrophage activity.Thus, we identify optimal PEG-PEIs which are promisingcandidates for therapeutic siRNA-mediated gene targetingand which may represent an attractive delivery platformfor siRNAs in RNAi-based therapies.