Background: Effective encapsulation of drugs into the delivery systems could increase the efficiency of nanoparticles in prevention and treatment of diseases.

Objective: The purpose of this study was to compare the different methods for determination of encapsulation efficiency of a model protein in the PLGA nanoparticles.

Methods: The various direct methods include dichloromethane, acetonitrile, modified acetonitrile and NaOH based extraction and radioactive methods were used to directly calculate the encapsulation efficiency of the loaded protein in the PLGA nanoparticles. Furthermore, indirect methods include BCA, Fluorescent and radioactive methods were compared.

Results: The encapsulation efficiencies determined by indirect methods include dichloromethane, acetonitrile, modified acetonitrile, NaOH based extraction and radioactive methods were 12.62% ± 1.97, 17.43% ± 2.51, 64.69% ± 4.31, 86.36% ± 2.25 and 90.15% ± 1.78, respectively. Moreover, the encapsulation efficiencies determined by indirect methods include BCA, fluorescent and radioactive methods were 81.46% ± 1.92, 88.23% ± 1.15 and 89.6% ± 1.9, respectively.

Conclusions: Among the results obtained by indirect methods, radioactive and fluorescent methods showed more reliable. Moreover, NaOH and radioactive methods were the most reliable methods among the direct methods.

Keywords: Encapsulation efficiency; PLGA; direct methods; indirect methods; nanoparticles.