Transfection polymer-protein

It should be emphasized at this point that the use of physicochemical methods is so far the only way to demonstrate the import of transgene DNA into the mitochondrial matrix in living mammalian cells. The unavailability of a mitochondria-specific reporter plasmid designed for mitochondrial expression severely hampers current efforts toward the development of effective mitochondrial expression vectors. Although any new nonviral transfection system (i.e., cationic lipids, polymers, and others) aimed at the nuclear-cytosolic expression of proteins can be systematically tested and subsequently improved by utilizing anyone of many commercially available reporter gene systems, such a methodical approach to develop mitochondrial transfection systems is currently impossible. 

Although some cells in skin, muscle, brain, and so on can spontaneously take up exogenous injected naked pDNA or mRNA [18], this process is relatively inefficient and can consequently be used only when a local expression of a protein is desired, i.e., for vaccination. Even if physical methods exist to enhance the uptake of naked nuclei acids (electroporation or hydrodynamic delivery see Section 1222), increasing the efficacy of transfection in vivo is best reached using encapsulation of the nucleic acids. Two methods are used cationic polymers or liposomes. 

To date, a variety of methods have been developed for the efficient delivery of QDs into cells [204, 205]. These include nonspecific endocytosis [206-209] or receptor-mediated endocytosis that involves QDs decorated with transfection reagents (peptides [210-215], proteins [65, 216-219], cationic liposomes [204], dendrimers [204], polymers [220,221] or small molecules [222,223]) that were used for the intracellular delivery of QDs. Physical techniques such as, electroporation [204, 224] or microinjection [204, 225, 226] have also been employed to deliver QDs into cells. 

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