encapsulation efficiency

Encapsulation efficiency measures how good a job the manufacturing process did at trapping the drug inside the carrier instead of letting it escape into the surrounding liquid. It is the amount of drug actually caught inside the carriers divided by the total amount of drug you added at the start, written as a percentage. If you start with 100 milligrams of drug and 80 milligrams end up inside the particles, the encapsulation efficiency is 80 percent.

It is measured by separating the loaded carriers from the free, unencapsulated drug — for example by centrifugation, filtration or column separation — and then assaying how much drug went each way. High encapsulation efficiency means little drug is wasted, which matters greatly for expensive biologic drugs and for products that must be free of irritating unentrapped material.

Encapsulation efficiency should not be confused with drug loading. A formulation can encapsulate nearly all of a small amount of drug (high efficiency) and yet have low loading if the carrier is heavy; conversely, a process can be inefficient yet still produce well-loaded particles by simply discarding the wasted drug. Both numbers describe different, equally important aspects of how well a carrier carries its cargo.