Table 1.

Intranasal API delivery systems.

Delivery System	Description	Refs.
Liposomes	Spherical vesicles consisting of one or several bilipid layers surrounding the aqueous phase. Hydrophilic drugs can be introduced into the aqueous phase, and hydrophobic drugs can be introduced into the bilipid layer of the liposome. Encapsulation of drugs in a liposomal system avoids degradation of the active pharmaceutical ingredient in the body and multidrug resistance.	[10]
Mucoadhesive polymer particles	They have the ability to adhere to the surface of mucous tissue, which leads to an increase in the concentration of the active pharmaceutical ingredient. This property allows for a reduction in the administered drug total dose.	[11]
In situ gels	Drug delivery systems that are used in the form of solutions or suspensions and are capable of phase transition in a certain place of the body under the influence of external factors such as temperature, pH, etc. These systems provide targeted release of active pharmaceutical ingredients and maintain them at a relatively constant concentration.	[12]
Micro- and nanoemulsions	Liquid-dispersed systems with a very fine distribution of droplets. These systems enable the delivery of hydrophobic drugs at a higher dose and have improved stability than conventional emulsions.	[9]
Solid lipid particles	They combine the advantages of delivery methods such as emulsions and liposomes; may have high capacity of active pharmaceutical ingredients and high API protection against the body environment factors.	[13]
Dendrimers	Highly ordered, branched polymer molecules with a symmetrically branched structure around a multifunctional central core. They have the ability to highly selectively encapsulate APIs.	[14]