Subconjunctivally injected, liposome-encapsulated streptokinase enhances the absorption rate of subconjunctival hemorrhages in rabbits.

Liposome-encapsulated streptokinase (SK) was prepared with distearoyl-phosphatidyl-ethanolamine-N-[methoxy(polyethyleneglycol)-2000] (DSPE-PEG(2000)). In vitro release assay demonstrated over 81% of SK was released from liposomes at 48 h, and the effect of its subconjunctival injection on the absorption rate of induced subconjunctival hemorrhage (SH) in rabbits was evaluated. After 8h of SH induction, eyes were randomly assigned to one of four subconjunctival injection groups (10 eyes each): group A: the free form of SK (1000 IU/mL); group B: liposome-encapsulated SK (1000 IU/mL); group C: 0.1 mL of liposomes; and group D: no injection. SHs were photographed at 8, 24, 48, 72, and 120 h after SH induction and their sizes were compared. Size decrease of the SH was faster in groups A and B than in groups C and D. Group B displayed significantly different absorption rates than group A at 24 and 48 h and with groups C and D at 24, 48, and 72 h, with the shortest mean elapsed time among all groups. The ocular absorption of SK was lower after the injection of the liposome-encapsulated SK than the free form. These results demonstrated that subconjunctival injection of liposome-encapsulated SK enhances the rate of SH absorption, especially in the early phases.