Pegylated poly-l-arginine derivatives of chitosan for effective delivery of siRNA.

For delivery of siRNA, chitosan (CS) was derivatized with poly-l-arginine (PLR) and polyethylene glycol (PEG). The formation of polyplexes with siRNA was confirmed by gel retardation. The PLR-grafted CS formed nanosized particles with siRNA. PLR-grafted CS showed higher cellular delivery efficiency of siRNA than did CS, pegylated CS, PLR, or pegylated PLR. The extent of reduction in the expression of fluorescent proteins was highest following treatment of the cells using PLR derivatives of CS in complexes with specific siRNAs. Cell viability was greater in populations treated with pegylated CS-PLR than in those treated with PLR. Hemolysis of erythrocytes was reduced upon conjugation of PLR with CS. The delivery of siRNAs via pegylated CS-PLR revealed little dependence on serum. Molecular imaging techniques revealed that the intratumoral administration of red fluorescent protein-specific siRNA in complexes with pegylated CS-PLR significantly silenced the expression of red fluorescent proteins in tumor tissues in vivo. These results indicate that pegylated CS-PLR might be useful for in vivo delivery of therapeutic siRNAs.

Effects of nuclear factor-kappaB small interfering RNA on posterior capsule opacification.

PURPOSE: The effects of small interfering (si)RNA of nuclear factor kappa B (NF-kappaB) on the development of posterior capsule opacification (PCO) were investigated both in vitro and in vivo in rabbits. METHODS: After application of p105 NF-kappaB siRNA to lens epithelial cells (LECs), Western blot analyses were performed to detect p105 and p50 NF-kappaB and a scratch assay was used to determine cell migration. In the capsular bag model, immunocytochemistry was performed to determine expression of p50 NF-kappaB and Western blot analyses for the presence of epithelial-to-mesenchymal transition (EMT) markers. Two sequences of p105 NF-kappaB siRNA were used in cataract surgery in 15 New Zealand White rabbits. PCO grading was conducted by slit lamp biomicroscopy and a computer-based PCO grading program. One month after surgery, the eyes of the rabbits were enucleated, and sections were prepared for examination of the posterior capsule and other ocular tissues by light microscopy. RESULTS: Application of p105 NF-kappaB siRNA to LECs decreased p105 NF-kappaB and p50 NF-kappaB expression, and migration of LECs was shown to be inhibited on the scratch assay. In the capsular bag model, the LEC count was significantly decreased, and immunocytochemistry showed reduced p50 NF-kappaB expression on the posterior capsule. EMT markers were significantly decreased after application of p105 NF-kappaB siRNA in the capsular bag model. In the in vivo study in rabbits, p105 NF-kappaB siRNA effectively decreased PCO, as determined by both slit lamp examination and the PCO grading program. CONCLUSIONS: NF-kappaB seems to be related to migration and proliferation of LECs. NF-kappaB siRNA was effective in inhibiting the migration and proliferation of LECs in vitro and decreased PCO formation after cataract surgery in an in vivo rabbit model.

Cell surface modification by activated polyethylene glycol prevents allosensitization after islet transplantation.

The necessity to transplant islet tissue without the need for immunosuppressant therapy has led to the development of materials for immune modulation. Pegylation makes islets antigenically silent, protecting them from the adsorption of foreign protein and thus avoiding immune injury. The aim of this study is to determine whether pegylation of islets prolongs islet survival and function both during tissue culture and posttransplantation. We used cyanuric chloride-activated methoxy-polyethylene glycol for cell surface modification. To detect the pegylation effect on splenocytes, we measured antibody binding inhibition and abrogation of lymphocyte proliferation. To detect the pegylation effect on islet grafts, we performed rodent islet transplantation. Islet viability and function were maintained after pegylation. Pegylated islets showed a 90% decrease in antibody binding and decreased lymphocyte proliferation in a mixed lymphocyte culture. However, when pegylated islets were transplanted, no prolongation of graft survival was observed. When a subtherapeutic dose of immunosuppressant was given at the time of transplantation of pegylated islets, islet graft survival was significantly prolonged. In addition, when rats were sensitized with donor splenocytes, graft survival was prolonged by pegylation. We observed that pegylation of islets, combined with a subtherapeutic dose of immunosuppressant, protects the graft from rejection. Prolonged graft survival in sensitized recipients showed that pegylation of islets shifted the pattern of rejection from an acute humoral response to a less aggressive cellular alloresponse.