22.6 Challenges of transposon as gene delivery system:

(i) Gene delivery efficiency is low

The efficiency of transposon system which is carried by naked DNA plasmids is limited by getting the plasmid into the cell by physical and chemical means. Transfection is easy in some primary cells and cell lines (e.g. HEK293, HeLa, Hepatocytes) and the transposition efficiency of transposons is quite high. Nucelofection and electroporation are some of the methods that are used for transfection is toxic to cells leading to cell death thereby reducing the efficiency of a stable transfection. Novel delivery methods like cell-penetrating peptides (CPP)- piggyBac fusions are being developed to overcome such difficulties. Though some researchers have encapsulated transposon system within viruses to use the virus in delivering the DNA to target site but the problem of immunogenicity of viruses still remains unsolved.

(ii) Integration of profile randomly

With respect to genomic elements transposons' have random preference to sites when it comes to integration of the gene. This leaves the transposed gene under the influence of the neighboring genomic region. The risk of possible genotoxicity increases when there is uncontrolled or not site-directed integration.

(iii) Silencing of the integrated transgene

When sleeping beauty is used in cultured cells silencing of gene has been observed. Whereas with piggyBac , silencing of transgene and modification of epigenetic transgene has not been studied well.