**7. Conclusion**

The silencing of gene through RNAi is a natural process that can be found in cells which are mainly involved in the degradation of mRNA and occur in the post-transcriptional phase. Their current status in treatment and diagnosis faces severe challenges because the traditional drugs are not very efficient and also because resistance to the treatment has developed. Silencing the gene that causes this resistance or the genes which cause tumors to form can be regulated by inhibiting them. RNAi i.e., miRNA and siRNA hold great promise in this situation in that these RNAs are involved in silencing the gene. Since their discovery, just over 20 years ago, these genes have been applied as therapeutics and for this they are synthesized synthetically. Not only in cancer, but also in the treatment of other disease as well, they have had a great contributory effect. The genes are very attractive in therapeutic approaches: they have the potential to target any gene in a virtual aspect since they can be synthesized as complementary to their target gene. If compared with conventional drugs, however, their mechanism of action depend on binding with the target site of the target molecule. Though the use of siRNA and miRNA as therapeutics has been found effective, it faces technical barriers such as its delivery to the target tissue, specificity and chemical modification. Delivery to the target tissue requires proper administration to obtain the desired effect. The gene should design carefully, lest it bring about the silencing of other related genes and unwanted effects. A proper safety profile should be maintained in designing the delivery of the RNAi which is highly important for its efficacy. Along with these factors, information regarding silencing effect of the gene, the dosage required for the desired effect, the stability of the RNA molecules, the release of the RNA from the delivery system, and its half-life and turnover of the target proteins are equally important.
