Effects of surface modification of PLGA-PEG-PLGA nanoparticles on loperamide delivery efficiency across the blood–brain barrier

In this study, we developed a nanoparticle system for drug delivery across the blood–brain barrier (BBB). The nanoparticle consisting of loperamide and poly(lactide-co-glycolide)-poly(ethylene glycol)-poly(lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymer were prepared by the nanoprecipitation method; then the nanoparticles were coated with poloxamer 188 or polysorbate 80. The effects of poloxamer 188 or polysorbate 80 on the physicochemical and pharmaceutical properties of the coated nanoparticles were investigated. Loperamide, which does not cross the blood–brain barrier (BBB) but exerts antinociceptive effects after direct injection into the brain, was encapsulated by different polymeric materials and used as a model drug. The in vitro BBB penetration study shows that the surfactant-coated PLGA-PEG-PLGA nanoparticles could have penetration of 14.4–21.2%, which was better than the PLGA-PEG-PLGA nanoparticles (PEP) (8.2%) and the PLGA nanoparticles (PN) (4.3%). The biopsy studies also confirm that the PEP coated by surfactant could increase the penetration. The results of nanoparticles accumulation in brain tissue show that the PEP coated by surfactant had a much higher concentration than both the PEP and the PN. Moreover, the maximal possible antinociception effect (MPE) for the surfactant-coated PEP was 21–35% at 150 min after administering the drug intravenously, which was significantly better than just the PEP (MPE: 11.6%). The results of the formalin test show that the surfactant-coated PEP administered intravenously 150 min prior to the formalin injection could greatly reduce the pain response in the first phase. The results demonstrate that the surfactant-coated PEP could help to deliver loperamide across the BBB.