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.