Table 1.

Summary of the advantages and disadvantages of different viral vectors that have been utilized for siRNA delivery

Delivery vector		Advantages	Disadvantages
Viruses	Adenovirus	Highly efficient transduction profile111	Immunological responses, nonspecific cell targetting,111 acute toxicity151
	AAV	Highly efficient transduction profile,111 reduce inflammatory and immune responses152, 153	Requires helper virus,152 small cloning capacity154
	Retrovirus	High gene transduction	Dependence of cell differentiated state,155 insertion into host genomes115
	Lentivirus	High gene transduction, cell differentiated state independence156	Insertion into host genomes115
Lipids	Cationic	Good transfection efficiency, electrostatic interactions with siRNA115	Poor stability, cellular toxicity, immune response elicitation106, 157
	Neutral	Reduced cytotoxicity115	Reduced ability to complex with siRNA115
	Nanoparticles	Charge variable, complex formation prior to administration, neutralized at physiological pH, reduced toxicity and immunological responses, increased membrane destabilizing capacity, higher endosomolytic activity110, 115, 158	Synthetic challenges
Polymers	Polycations	Modifiable size115	Weaker interactions with siRNA115
	Nanoparticles	Biocompatible, biodegradable, synthetic diversity115	Large surface area causes aggregation159
Peptides	PLL	Electrostatic interactions with siRNA, synthetic diversity120	Toxicity, nonspecific binding, poor endosomal escape102, 160, 161
	CPPs	Synthetic diversity, covalent and noncovalent complex formation120	Membrane permeability challenges, poor endosomal escape120, 162