Gene Delivery Using Lipoplexes and Polyplexes: Principles, Limitations and Solutions.

Gene therapy has attracted considerable attention for the treatment of genetic and acquired diseases. Successful gene therapy occurs when the therapeutic genes penetrate targeted cells and become available to the intracellular active site. Currently, a promising approach in gene delivery is the use of nonviral gene delivery vectors that lack immunogenicity but have low toxicity and potential tissue specificity. The widely used, existing nonviral gene vectors are cationic lipids and polymers that can pass across extracellular and intracellular barriers. However, the toxicity of these vectors is a barrier to their use. Currently, the disadvantages of nonviral vectors have been minimized by several modifications. The main purpose of this review is to describe the pros and cons of gene delivery using cationic lipids and polymers.

Liposome Circulation Time is Prolonged by CD47 Coating.

INTRODUCTION: Bio-degradable nano-particles have many applications as drug delivery vehicles because of their good bio-availability, controlled release, low toxicity and potential for encapsulation. However, the most important obstacle to nanoparticulate drug delivery is elimination by macrophages which reduces the residence time of nanoparticles in the blood. To overcome this problem, the surface of the nanoparticle can be passivated by coating with Polyethylene glycol (PEG). However, the use of PEG has its own disadvantages. CD47 receptor acts as a self marker on the surface of many cells and inhibits phagocytosis. This study used a CD47 mimicry peptide as a substitute for PEG to fabricate "stealth" nanoliposome with reduced macrophage clearance. METHODS: Doxorubibin was used as a model drug because of its inherent fluorescence. Doxorubicin- containing liposomes were coated with different percentages of CD47 mimicry peptide (0.5% and 1%). PEG-functionalized doxorubicin-containing liposomes, were used as a comparator. The liposomal formulations were intravenously injected into mice. Serum was collected at pre-defined time points and tissue samples were taken at 24 hours. Fluorescence was used to determine the concentration doxorubicin in serum, heart, spleen, kidney, liver and lung tissues. RESULTS: Tissue biodistribution and serum kinetic studies indicated that compared with PEG, the use of CD47 mimicry peptide increased the circulation time of doxorubicin in the circulation. Moreover, unwanted accumulation of doxorubicin in the reticuloendothelial tissues (liver and spleen), kidney and heart was significantly decreased by the CD47 mimicry peptide. CONCLUSION: The use of a CD47 mimicry peptide on the surface of nanoliposomes improved the residence time of liposomal doxorubicin in the circulation. The accumulation of drug in non-target tissues was reduced, thereby potentially reducing toxicity.