Table 1.

Advantages and disadvantages of various gene delivery systems

	Capacity	Advantages	Disadvantages	Ref.
		Viral systems
Retrovirus	8 kb	Permanent gene expression	Less effective in vivo; high immunogenic; infects just dividing cells; High carcinogenic risk due to insertional mutagenesis	[2, 10, 11]
Lentivirus	8 kb	Permanent gene expression; transduce both dividing cells and non-dividing	Random integration into genome causes insertional mutagenesis; Probable for tumorigenesis	[2, 10, 11, 25]
Adenovirus	> 7.5 kb	Transduce both dividing and non-dividing cells; Carrie large DNA cargo (up to 38 kb); safe; high titer production	Transient gene expression; pre-existing immunity	[2, 10, 11, 26]
Adeno-associated virus	< 4 kb	Permanent gene expression; non-pathogenic; wide-ranging host and cell type	Deliver low amount of gene cargo due to its small size; Low titer production	[2, 10, 11, 27]

	Capacity	Advantages	Disadvantages	Ref.
		Non-viral systems (Physical Methods)
Microinjection	Small fragments to large size fragments (up to the amount of DNA)	Very high efficacy	In vivo problematical; technically demanding; only a few cells (100–200) can be injected in one experiment;	[28, 29]
Gene gun (gene gun /Biolistic gene transfer)	Small fragments to large size fragments (up to the amount of DNA)	Good efficiency (depends on the loading of genetic material onto the particles, the size of the particle, and the timing of delivery	limited tissue depth (usually used for delivery to the skin); inflammation and damage in tissue in some applications; non-specificity (possibly non-targeted cells transfection); quantities limitation of DNA or RNA on microparticles (so, several transfections needed for tissue engineering applications.)	[17]
Electroporation	Small fragments to large size fragments (up to the amount of DNA)	Easiness; inexpensive; vector free	Invasive; Poor infiltration across (deep) tissues	[15, 30]
Magnetoporation	Small fragments to large size fragments (up to the amount of DNA)	Economic; Non-invasive; make possibly gene delivery to diverse cells (i.e.; hard-to-transfect cells, primary cells, and non or slowly dividing cells)	Poor efficiency with naked DNA	[15, 29, 30]
Sonoporation	Small fragments to large size fragments (up to the amount of DNA)	Noninvasive; high efficiency compares to ultrasound, Imaging during treatment; can be used in vivo; site-specificity;	Lower Reproducibility; Tissue damage; relatively low transfection efficiency (in vitro and in vivo)	[15, 29, 30]
Optoporation (Laser irradiation/ Photoporation)	Small fragments to large size fragments (up to the amount of DNA)	High-efficiency accuracy of the laser beam; might be better for local gene delivery;	Probability tissue damage; low accuracy; Low irradiation area; low transfection rate; limited for clinical use;	[15, 30]

	Capacity	Advantages	Disadvantages	Ref.
		Non-viral systems (Chemical Methods)
Protein-based methods	Several kb (by viral capsid protein) short sequences (by dsRNA-binding proteins and modified oligonucleotides)	Low toxicity Increased stability	Protein purification	[30]
Peptide-based methods	Variable from the length of ASO or siRNA to plasmid DNA	Biocompatible and biodegradable; Low to moderate toxicity; selective targeting and barrier protection; easily synthetizes (in bacterial or mammalian cells and with SPPS technique.)	Synthesis can be expensive in some cases	[30, 31]
Lipid-based methods	Variable from the length of ASO or siRNA to plasmid DNA	Low toxicity (excluding highly cationic particles); Low immunogenicity; Easy to manufacture; biocompatibility; targeting and long-term blood circulation with Surface modification (e.g., ligands and PEGylation; respectively)	Low half-life stability on storage; Historically low transfection efficiency compared to viral vectors	[30, 32]
Polymers, dendrimers, and micelles	Variable from the length of ASO or siRNA to plasmid DNA	non-immunogenic; transient expression; high packaging capacity; Targeting possible via site-specific attachment of ligands; Biodegradability of many polymers (i.e.; chitosan, PLGA, or PLL)	Low gen delivery efficiency in-vivo; Cytotoxicity of highly cationic polymers; Biodegradability issues for certain polymers Immune response to polymers	[30, 32]
Nanoparticles (Carbon allotropes, Metal nanoparticles, Spherical nucleic acids, Porous particles)	Variable from the length of ASO or siRNA to plasmid DNA	High packaging capacity: Low cytotoxicity and non-immunogenic	Difficult in vivo degradation; Low gene delivery efficiency; toxicity (Some carbon allotropes)	[30]