Discuss two non –viral strategies for the in-vivo delivery of genes into cells?
1. Successful treatment of genetic diseases by gene therapy is required for efficient delivery of “DNA” into specific cells, followed by safe and long term expression of the encoded gene product.
2. Problems with gene expression is associated with it been recognised as foreign material so when transferred into the cells is unstable. Stabilising the DNA in the cell prolongs the clinical effect in “vivo”. Stabilisation involves altering the backbone of the DNA which alters certain properties.
“PS” more stable
“MP” more easily crosses the lipid membrane, no repulsion form negative membrane.
“PNA” no phosphate associated, so not charged stronger interaction with DNA, stronger binding makes more stable and more stable towards enzymes.
3. In order for genes to be expressed they must reach the nucleus, but there is numerous obstacles to overcome. Limitations factors in therapeutic gene delivery can be extracellular such as undesired interactions with blood plasma proteins in the circulatory system, extracellular matrix proteins and with cells that are not intended delivery targets. A solution to this is the attachment of hydrophobic molecules such as “Polyethylene Glycol” or by encapsulating the vector either in a lipid vesicle.
4. Other barriers to gene delivery or intracellular delivery barriers in the form of the “Endosomal membrane,” “entrapment within the endosome/lysosme vesicles.” After entry into the cell by endocytosis, the vector/DNA complex must exit from the endosome to escape degradation through the lysosomal pathway. A solution to this is to destabilise the endosome via an osmotic imbalance created by the so called “Proton Sponge Effect” in which more an more ions are pumped into the endosome in an effort to acidify it against the large backdrop of the basic polymeric vector. The nuclear envelope which encapsulates the nucleus is an effective barrier to...