It depends upon your nature of polymer, nanocapsule prep,  drug, interaction between the drug and polymer, interaction between the medium and polymer/drug, temp, pore size of the capsule - - - - - - 

Please make your question bit more specific 

Dear milad,

1st  you calculate the dose you need to develop then you go for the related supportive articles similar to your excipients used in preparing nanocapsules and also as said by muthu, it depends on several factors. each and every factors affects the drug loading like both physical and chemical properties. so you need to be more specific on several other factors.

regards

It depend on wander waals attraction as well as hydrogen bonding between hyrophillic or lipophillic part of polymer and drug.