Va Ab

See how to determine the encapsulation efficiency of a hydrophobic drug in liposomes

https://www.cd-bioparticles.net/blog/method-for-measuring-drug-encapsulation-efficiency/

You can use the Separation of free drug from encapsulated drug. There are several separation methods to remove unencapsulated (free) drug (Centrifugation (ultracentrifugation), Dialysis, Size-exclusion chromatography (SEC), Ultrafiltration).

• To determine the encapsulation efficiency (EE%) of a hydrophobic drug in liposomal formulations, a precise analytical approach is employed involving separation and quantification techniques. Initially, liposomes are prepared by conventional methods such as thin-film hydration or ethanol injection, incorporating the hydrophobic drug within the lipid bilayer due to its affinity for nonpolar environments. To quantify only the entrapped drug, it is essential to separate the unencapsulated (free) drug using methods like ultracentrifugation (e.g., 100,000 × g for 1 h at 4°C), dialysis against phosphate-buffered saline (PBS, pH 7.4) using a membrane with a molecular weight cut-off (MWCO) of 12–14 kDa for 12–24 h, or size-exclusion chromatography (e.g., Sephadex G-50 column). Following separation, the total drug content is determined by lysing the liposomes with organic solvents such as methanol or Triton X-100 and quantifying the drug using UV-visible spectrophotometry, HPLC, or LC-MS/MS, depending on the drug’s physicochemical properties. Free drug content is similarly quantified in the separated phase. Encapsulation efficiency is calculated using the equation: EE% = [(Total drug – Free drug)/Total drug] × 100. Care must be taken to ensure that the organic solvent completely dissolves the hydrophobic drug and disrupts the liposomal bilayer without degrading the analyte. Accurate quantification, preferably in triplicates, with method validation ensures reproducibility and reliability. This methodology has been widely adopted in liposomal drug delivery research, as reported in studies such as Pattni et al. (2015, Nature Reviews Drug Discovery, 14(12), 771–785) and Akbarzadeh et al. (2013, Nanoscale Research Letters, 8, 102).

Dear Va Ab,

For a valid and reliable analysis in liposomal drugs, you can use the monograph of the drug in pharmacopoeia books such as the USP, BP, EP or Japanese Pharmacopoeia. These references list the solvents in which the drug is dissolved. Also, liposome disruption and drug quantification are two different issues that should be considered separately. Dr. Mani Sharma's answer and explanations are very valuable and a very good guide to your question.

Good luck.