ABSTRACT
Hurdles in cell-specific delivery of small interfering RNA (siRNA) in vivo hinder the clinical translation of RNA interference (RNAi). A fundamental problem concerns conflicting requirements for the design of the delivery vehicles: cationic materials facilitate cargo condensation and endosomolysis, yet hinder in vivo targeting and colloidal stability. Here, we describe a self-assembled, compact (~30 nm) and biocompatible ribonucleoprotein-octamer nanoparticle that achieves endosomal destabilization and targeted delivery. The protein octamer consists of a poly(ethylene glycol) scaffold, a sterically masked endosomolytic peptide and a double-stranded RNA-binding domain, providing a discrete number of siRNA loading sites and a high siRNA payload (>30 wt%), and offering flexibility in both siRNA and targeting-ligand selection. We show that a ribonucleoprotein octamer against the polo-like kinase 1 gene and bearing a ligand that binds to prostate-specific membrane antigen leads to efficient gene silencing in prostate tumour cells in vitro and when intravenously injected in mouse models of prostate cancer. The octamer's versatile nanocarrier design should offer opportunities for the clinical translation of therapies based on intracellularly acting biologics.
Subject(s)
Drug Delivery Systems/methods , RNA, Small Interfering , Ribonucleoproteins , Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacokinetics , Cell Line, Tumor , Gene Silencing , Humans , Polyethylene Glycols/chemistry , RNA, Small Interfering/chemistry , RNA, Small Interfering/genetics , RNA, Small Interfering/pharmacokinetics , Ribonucleoproteins/chemistry , Ribonucleoproteins/pharmacokineticsABSTRACT
Sm ribonucleoprotein complex was immunopurified and labelled with 125I. After i.v. injection into normal mice 125I-Sm was cleared with a half life of less than 3 min, mainly to the liver (54% at 15 min). With time there was a progressive reduction in liver uptake (13.3% at 1 h), and this was associated with the appearance of increasing amounts of trichloroacetic acid soluble 125I in serum, suggesting complete Sm catabolism. Injection of 125I-Sm as a preformed immune complex with human anti-Sm antibody was associated with slower antigen removal from the circulation (half life 15 min), more gradual liver uptake (27% at 1 hr), and less degradation products in the serum than after injection of antigen alone. These data suggest that release of 125I-Sm into the circulation is followed by specific organ uptake and antigen degradation. In the form of an immune complex, the rapid removal mechanism is impaired, and antigen persists in the circulation in an undegraded form. Simultaneous production of anti-Sm antibody and Sm antigen release following tissue destruction could lead to amplification of any primed immune response as a result of autoantigen drive in systemic lupus erythematosus.
