An in situ gelling liquid crystalline system based on monoglycerides and polyethylenimine for local delivery of siRNAs.

The development of delivery systems able to complex and release siRNA into the cytosol is essential for therapeutic use of siRNA. Among the delivery systems, local delivery has advantages over systemic administration. In this study, we developed and characterized non-viral carriers to deliver siRNA locally, based on polyethylenimine (PEI) as gene carrier, and a self-assembling drug delivery system that forms a gel in situ. Liquid crystalline formulations composed of monoglycerides (MO), PEI, propylene glycol (PG) and 0.1M Tris buffer pH 6.5 were developed and characterized by polarized light microscopy, Small Angle X-ray Scattering (SAXS), for their ability to form inverted type liquid crystalline phases (LC2) in contact with excess water, water absorption capacity, ability to complex with siRNA and siRNA release. In addition, gel formation in vivo was determined by subcutaneous injection of the formulations in mice. In water excess, precursor fluid formulations rapidly transformed into a viscous liquid crystalline phase. The presence of PEI influences the liquid crystalline structure of the LC2 formed and was crucial for complexing siRNA. The siRNA was released from the crystalline phase complexed with PEI. The release rate was dependent on the rate of water uptake. The formulation containing MO/PEI/PG/Tris buffer at 7.85:0.65:76.5:15 (w/w/w/w) complexed with 10 µM of siRNA, characterized as a mixture of cubic phase (diamond-type) and inverted hexagonal phase (after contact with excess water), showed sustained release for 7 days in vitro. In mice, in situ gel formation occurred after subcutaneous injection of the formulations, and the gels were degraded in 30 days. Initially a mild inflammatory process occurred in the tissue surrounding the gel; but after 14 days the tissue appeared normal. Taken together, this work demonstrates the rational development of an in situ gelling formulation for local release of siRNA.

Properties of the tibialis anterior muscle after treatment with laser therapy and natural latex protein following sciatic nerve crush.

INTRODUCTION: In this study we evaluated the characteristics of the tibialis anterior muscle after sciatic nerve crush and treatment with low-level laser therapy (LLLT) or the protein from natural latex (P1). METHODS: We studied the following 6 groups of male Wistar rats: control (CG); exposed nerve (EG); injured nerve (IG); injured nerve with LLLT (LG); injured nerve with P1 (PG); and injured nerve with P1 and LLLT (LPG). RESULTS: After 4 weeks, muscle morphology showed improvement in the treated groups; after 8 weeks, the treated groups resembled controls, especially the PG. Morphometry revealed muscle fiber atrophy after nerve injury, with time-dependent recovery. Histochemical analysis revealed increased intermediate fiber area. The PG was more similar to controls with NADH staining, whereas the LPG more closely resembled controls with SDH staining. CONCLUSION: Treatment using only P1 proved most efficient, revealing a negative interaction between P1 and LLLT.

Self-assembling gelling formulation based on a crystalline-phase liquid as a non-viral vector for siRNA delivery.

Liquid crystalline systems (LCSs) form interesting drug delivery systems. These include in situ gelling delivery systems, which present several advantages for use as self-assembling systems for local drug delivery. The aim of this study was to develop and characterize in situ gelling delivery systems for local siRNA delivery. The influence of the components that form the systems was investigated, and the systems were characterized by polarized light microscopy, Small Angle X-ray Scattering (SAXS), swelling studies, assays of their ability to form a complex with genes and of the stability of the genes in the system, as well as assays of in situ gelling formation and local toxicity using an animal model. The system containing a mixture of monoglycerides (MO), oleylamine (OAM), propylene glycol (PG) and tris buffer (8.16:0.34:76.5:15, w/w/w/w) was considered the most appropriate for local siRNA delivery purposes. The molecular structure was characterized as hexagonal phase; the swelling studies followed a second order kinetic model and the water absorption was a fast process reaching equilibrium at 2 h. The system formed a complex with siRNA and remained in a stable form. The gel was formed in vivo after subcutaneous administration of a precursor fluid formulation in mice and was biodegradable in 30 days. The inflammatory process that took place was considered normal. Therefore, the developed liquid crystalline delivery system shows the appropriate characteristics for use as a local siRNA delivery method for gene therapy.