Liposomes have been extensively studied as a vehicle for in vivo and in vitro delivery vehicles. The use of liposomes to deliver DNA into different types of eukaryotic cells is more efficient and reproducible than other methods.

Among them, the surface of cationic liposome is positively charged, which can encapsulate DNA molecules with the phosphate group of nucleic acid through electrostatic interaction to form a DNA-lipid complex, and can also be adsorbed by the cell membrane with negative charge on the surface, and then pass through the fusion of the membrane, and endocytosis of cells, leads to the delivery of DNA into cells. Afterwards, the delivered DNA can be released from the inclusion bodies and into the cytoplasm. The exogenous DNA in the cytoplasm can be transcribed and expressed in the cell after entering the nucleus.

Figure 1. Lipoplex-mediated transfection and endocytosis.(Alan L Parker, et al.; 2003)

The basis for using cationic lipids as delivery systems for negatively charged DNA/RNA is that positively charged hydrophilic heads can condense with DNA/RNA, while hydrophobic tails can form micelles or bilayer structures around DNA/RNA. This complex surrounding DNA is called a lipoplex and creates protection for DNA/RNA against degradation by nucleases. There are many lipid structures that have been tested to find the optimal lipid complex structure with DNA/RNA. For example, the head groups of lipids can be primary, secondary and tertiary amines, or quaternary ammonium salts and groups such as phosphorus, guanidino, arsenic, imidazole and pyridine. The hydrophobic tail consists of an aliphatic chain, which may be unsaturated or saturated, and is attached to the hydrophilic head by a linker usually consisting of an ester, ether, carbamate, or amide. Cholesterol, as well as other steroids, are often included in the formulations of these lipid complexes to increase the stability and flexibility of these vectors and have been shown to improve transfection in vivo. All these components are important for formulating promising non-viral gene delivery vectors critical. Subtle changes in the ratio of these components can dramatically alter transfection efficiency and affect cellular uptake and release from endosomes. Electrostatic interactions between negatively charged cell membranes and positively charged lipid headgroups are critical for achieving higher levels of cellular uptake.

Although simple early-stage lipid complexes are capable of delivering genetic material to cells, they have drawbacks including low transfection rates, inability to target specific cells, short half-lives, and toxicity due to the use of positively charged lipids. To address the short circulation and toxicity issues of cationic lipid carriers, PEG has been introduced to the surface of these carriers to shield positive charges and reduce opsonization from the reticuloendothelial system.  The addition of PEG increased the cycle time, giving these vectors more time to transfect cells; however, surface PEG prevented the interaction between the cationic lipid complex and the anionic cell membrane, thereby reducing the overall transfection efficiency. Therefore, CD BioSciences employed the conjugation of cell-specific targeting ligands to the distal end of PEG, as well as the addition of shorter alkylated chains to the PEG-lipid conjugates that can shed themselves over time in the circulation and other strategies to improve liposome delivery systems. Furthermore, our incorporation of chemosensitive bonds also ameliorated the problem of PEG shedding in acidic or reducing environments such as endosomes or cytoplasm.

Extended circulation times and reduced toxicity due to surface modifications enable targeted gene delivery to cells located in interstitial regions. In addition to applications in systemic delivery, local DNA and siRNA delivery has great potential for gene delivery directly to the respiratory tract to treat cystic fibrosis and to the cornea and retina to treat ocular degeneration.

Advantages of our liposomes as transfection vehicles:

1. It can enhance the adsorption capacity of the delivery carrier on the cell membrane, thereby improving the uptake of cells;

2. Low cytotoxicity;

3. Longer internal circulation time;

4. The liposome carrier can prevent the degradation of nucleic acid in vivo;

5. The cationic liposomes after adding PEG can be more convenient for functional modification, for example, targeting ligand modification.

6. PEGylated targeting liposomes can target specific regions, thereby allowing the contained genes to be expressed in specific tissues or cells.

Our Service:

• Customized lipofection kits according to customer needs
• Provide liposome carriers with different proportions for users to choose
• Can provide screening of different vectors to determine the best transfection vector
• Professional design and service team to provide you with reliable service and technical support
• Timely feedback of technical reports

CD BioSciences specializes in developing transfection systems and customizing transfection reagents for gene transfection using our core technologies. With our high-quality products and services, your transfection results can be greatly improved.

Reference

1. Audouy SA, et al.; In vivo characteristics of cationic liposomes as delivery vectors for gene therapy. Pharm Res. 2002, 19(11):1599-605.
2. F. Xiong, et al.; Cationic liposomes as gene delivery system: transfection efficiency and new application. Pharmazie. 2011, 66: 158–164.
3. Alan L Parker, et al.; Nonviral Gene Delivery: Techniques and Implications for Molecular Medicine. Expert Reviews in Molecular Medicine. 2003, 5(22):1-15.

* For research use only. Not for use in clinical diagnosis or treatment of humans or animals.