[medhahegde]

Lipofection- It is the most common and generally utilized gene transfer technique in the recent years. Transfection lipids (cationic) are made up of a positively charged head group (for instance amine), a flexible linker group (ether or ester) and 2 or more hydrophobic tail groups. The combined DNA and cationic lipids act instantaneously to form structures called as lipoplexes that are more complex in structure than the simple liposomes. When lipoplexes are prepared under suitable conditions, they sustain an overall positive charge, which enables them to effectively bind to negatively charged cell surfaces and enter the cell by means of endocytosis. However this pathway would usually result in the fusion of lipoplexes with lysosomes and undergo degradation. This problem is overcome by utilizing the neutral helper lipids, for instance dioleoylethanolamine (DOPE), which are generally included along with the cationic lipid. This allows entrapped DNA to escape the endosomes, reach the nucleus and get access to the cell’s transcriptional machinery.

Polymers – In the current era, a diversity of organic polymers are being used to carry out transfection. One of the most well accepted polymer is the, polyethylenimine (PEI). It is a polycationic organic macromolecule that has a high cationic charge density (also called as a proton sponge). It condenses the nucleic acid (DNA) into positively charged particle that interacts with the cell surfaces that are anionic in nature and gains entry into the cells by means of endocytosis. Dendrimers are another group of polymers that are composed of three-dimensional, branched structures known as dendrons. Among them, the polyamidoamine (PAMAM) family of dendrimers have proven to be a useful tool for transfection. Since the sphere-shaped polycationic dendrimers are alike in proportion and shape to the histone clusters, they can compact the DNA to a small size and facilitate its entry into cells.

Targeting Proteins & Peptides - A range of protein and peptide sequences have been utilized to target, enhance or mediate delivery of nucleic acids in a large variety of applications. Such proteins and peptides are regularly utilized along with cationic lipids (example integrin-targeting peptide, Fusogenic peptides such as GALA, N-terminal peptide of influenza hemagglutinin HA2 subunit). The key benefits of utilizing targeting proteins and peptides are that both will enhance the transfection efficiencies and provide targeted delivery.