Determination of the Encapsulation Efficiency and Drug loading content

The percent Encapsulation Efficiency (EE%) and the percent Drug Loading (DL%) content of res-loaded nanoparticles was determined by analysis of the supernatant obtained from the washes during synthesis (un-encapsulated drug) against a standard calibration curve of pure res. A representative 2 mL sample from each wash was centrifuged at 10,000 r.p.m. for 10 min at room temperature. The supernatant was collected and analysed on a multimodal microplate reader (Tecan Spark 20M) to measure the fluorescence intensity of the sample (excitation wavelength of 356 nm and an emission wavelength of 383 nm). For the calibration curve pure res was first diluted in DMSO to form a stock solution. This was further diluted in PBS to form a series of concentrations for the calibration curve. All experiments were performed in triplicates.

The % entrapment efficiency (EE%) is calculated from equation (1) ⁴⁵:

The % drug loading content (DL%) is calculated from equation (2) ⁴⁵:

where C₁ is the amount of res encapsulated in res-loaded NPs, C₂ is the total amount of res used during synthesis and C₃ is the total amount of polymer used during synthesis.