Table 1.

siRNA delivery systems.

Material	Advantages	Disadvantages
Liposomes	Cheap synthesis Easy functionalization Biodegradable	Tendency to accumulate in the liver and lung if not functionalized Possible induction of mild inflammation
GalNac *	Targeting properties Biodegradable
Exosomes	Excellent biodistribution and biocompatibility	Production by patient cells
PLGA *	Biocompatible biodegradable FDA approved	Not easy siRNA encapsulation due to PLGA hydrophobic nature
Chitosan	Easy functionalization	Low transfection efficiency and low solubility
Hyaluronic acid	Targeting ability toward cluster determinant 44, over-expressed in cancer cells Biodegradable Biocompatible	Functionalization required to bind siRNA due to its negative electric charge
Dendrimers	Great loading capacity related to the size	Possible toxicity related to particle size
Mesoporous silica	Biocompatible High surface area, the large pore volume, chemical and thermal stability	Functionalization required for targeting purposes
Gold nanoparticles	High surface area to volume ratio, possible multi-functionalization, easy synthesis, non-toxic non-immunogenic	Functionalization required to bind siRNA due to the negative electric charge

* GalNac: N-Acetylgalactosamine; PLGA: Copolymer of polylactic acid (PLA) and polyglycolic acid (PGA).