DNA in a sugar shell
A sugar-coated polymer granule delivered DNA to the cell 500 times more efficiently
RNF blog on Naked Science portal
Russian and American scientists have developed an innovative non-viral DNA delivery system to immune cell cultures. There have already been attempts to use DNA granules with a positively charged polymer, but this method had low efficiency. In their work, the scientists additionally coated the granules with sugar mannose and increased the delivery efficiency by 500 times. The development will help treat cancerous tumors.
The results of the study, supported by a grant from the Russian Science Foundation (RNF), are published in the journal Macromolecular Bioscience (Lopukhov et al., Mannosylated Cationic Copolymers for Gene Delivery to Macrophages).
Genetic engineering is increasingly becoming part of every person's daily life: gene modifications are used to increase the yield and resistance of plants to pathogens, as well as to produce new strains of bacteria and fungi that can synthesize almost any substances, from fuel to antibiotics. In addition, this approach can help treat human and animal diseases, for example, restore the ability to see when vision is lost.
For medical purposes, it is necessary to make the delivery of DNA to the target cell as safe as possible. There are many methods, but the most optimal is the use of viral particles: they stick only to proteins on the surface of certain cells and, moreover, do not cause their death. Although virus deliverers do not contain their own genetic material and cannot reproduce in cells, the process of their synthesis and assembly is complex and requires control at all stages of production to prevent the appearance of real viruses.
Non-viral DNA deliverers can also be improved so that the genetic material enters only specific cells of the body, for example, macrophages. Macrophages, one of the immune cells, should normally protect the body from infections and cancer. However, if there is already a tumor, it can "recruit" some of the macrophages to protect itself from the rest of the immunity.
Genetic engineering techniques can help destroy such cellular "traitors" or recruit them back, thereby weakening the tumor. In their work, researchers from Lomonosov Moscow State University, the University of Nebraska (Omaha) and the University of North Carolina (Chapel Hill) efficiently delivered DNA to cells using positively charged polymers.
A positive charge in this case is needed to bind negatively charged DNA. Particles are spontaneously collected from such polymers, which can be further modified: add additional bonds inside the tangle and thereby make it more durable or cover the particle with a shell. Scientists have determined the ability to deliver genetic material in particles from two different polymers containing amino acid monomers from lysine or aspartic acid. They evaluated how additional crosslinking and the mannose sugar shell affect the survival of macrophages and the ability of particles to place genetic material in these cells.
The DNA of fluorescent proteins was delivered to the cell, which is able to make the cell glow. This helped to determine whether nucleic acids were transferred to the cell using polymer particles: the stronger the glow of the cell culture, the more successful the delivery. It turned out that among all the options studied, polymer particles with aspartic acid, coated with mannose and without internal crosslinking are the most effective. In this case, 80 percent of the cells survive, which is higher than some popular methods. For example, when cells are bombarded with gold particles with DNA, only half survive. Moreover, the efficiency of nucleic acid transfer in such particles is 500 times higher than for polymer tangles without a mannose sheath.
"Despite the success of our experiments, the delivery efficiency was slightly less than for some well-known analogues offered for delivery earlier. However, they are not specifically targeted at immune cells and cannot be used on humans due to their high toxicity. Unlike such approaches, our method is suitable for humans," comments Alexander Kabanov, project manager for the RNF grant, Corresponding Member of the Russian Academy of Sciences, Doctor of Chemical Sciences, Head of the Laboratory of Chemical Design of Bionanomaterials of the Chemical Faculty of Lomonosov Moscow State University.
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