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Biological methods
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Transduction
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A specific DNA donor is required for DNA transfer to recipient bacteria
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Conjugation
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Requiring physical contact of recipient and donor (host strain) with a conjugative plasmid or participation of a third bacterium with a helper plasmid
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Not useful for large-scale delivery applications
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Gene transformation
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Limited to a few naturally competent groups
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Physical methods
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Electroporation
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Highly efficient but requires low ionic strength medium and high voltage
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Not useful for large-scale delivery applications
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Laser irradiation
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Employs a laser to change cell permeability to allow transferal; requires physical contact of laser and cells
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Ultrasound DNA delivery (UDD); Sonoporation
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Appropriate approach for plasmid or DNA fragment transferal to eukaryotic cells (e.g., gene therapy)
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Heat shock transfer
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Mostly used for E. coli (in parallel with the calcium phosphate method)
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Chemical methods
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Protein & Peptides
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Introduced in the late 1950s, this technique originally used high salt concentration and polycationic proteins to enhance nucleic acid entry into the cell.
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Now cationic peptides are using to enhance nucleic acid delivery. Cationic peptides have been found useful for enhancing cellular uptake and/or cell targeting oligonucleotide analogs. These peptides are synthetically conjugated, used as non-covalent complexes, or used in combination with polymer formulation techniques
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Calcium phosphate
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Simple, effective and still widely used for nucleic acid delivery
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Artificial lipids
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DNA has been successfully complexed with cationic, anionic and neutral liposomes. These complexes can be handled easily, but lipid-based systems generally have significant drawbacks, including the lack of targeting and variations arising during fabrication
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Naonparticles
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Using carbon nanotubes, nucleic acid is delivered into cells. Magneto-transformation has also been used for nucleic acid transfer, but in that method, pulsed magnetic fields assisted the delivery of DNA using magnetic nanoparticles.
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