Abstract: AimTo study the action of RMP-7 and its derivative on transporting liposome across the blood brain barrier (BBB) into the brain. MethodsRMP-7 and DSPE- PEG-NHS ［1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-n-［poly(ethylene-glycol)］-hydroxy succinamide］ were conjugated together in mild condition and MALDI-TOF-MS (Matrix -Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry) was used to determine their molecular ratio. An in vitro BBB model was established and used to determine in vitro bioactivity of RMP-7 and its derivative. The fluorescence of brain slices and the Evens Blue (EB) concentration in the brain, liver, spleen, lung and kidney of each group were used to evaluate the in vivo bioactivity of RMP-7 and its derivative on transporting liposome across the BBB. ResultsThe average molecular weight (MW) of the reaction product was 4 900, while those of DSPE-PEG-NHS and RMP-7 were 3　224 and 1　098. The results demonstrated that RMP-7 was conjugated to DSPE-PEG-NHS at the molecular ratio of 1∶1, so the product was DSPE-PEG-RMP-7. RMP-7 and DSPE-PEG-RMP-7 was shown to improve the transporting of peralcohol enzyme across the in vitro BBB model 2-3 times higher than the peralcohol enzyme only. DSPE-PEG-RMP-7 could facilitate the transporting of EB into brain more easily than RMP-7. Conclusion Both RMP-7 and DSPE-PEG-RMP-7 could facilitate the transporting of liposome across the BBB, especially DSPE-PEG-RMP-7.