Preparation of paraoxonase‐1 liposomes and studies on their in vivo pharmacokinetics in rats

A liposome formulation of the enzyme paraoxonase‐1 (PON1) was prepared for purposes of prolonging and maintaining its activity in vivo. Following purification of PON1 from rabbit serum, liposomes containing PON1 (L‐PON1) were prepared using a film‐dispersion method with a soybean phospholipid–cholesterol mixture (5 : 1, w/w). The pharmacokinetic behaviour of conventional injectable PON1 and L‐PON1 was compared following a single intravenous injection in rats. The enzyme activity of PON1 and its pharmacokinetic parameters were calculated based on a two‐compartment model following conventional injection. The level of PON1 encapsulation in L‐PON1 was 86.20 ± 3.12%. The particle size distribution of L‐PON1 was a narrow unimodal form, with an average diameter of 126 nm. The results suggest that compared with conventional injectable PON1, L‐PON1 has an improved half‐life and enhanced enzyme activity in rats. In conclusion, PON1 can be encapsulated into a lipid bilayer for enhanced stability.