The possibility of using gene therapy for the treatment of brain diseases such as brain cancer, Alzheimer's and Parkinson's diseases, is currently hampered by the lack of gene delivery systems able to cross the blood-brain barrier and deliver DNA to the brain following intravenous administration. On the basis that lactoferrin can effectively reach the brain by using specific receptors for crossing the blood-brain barrier, we propose to investigate if a lactoferrin-bearing generation 3-diaminobutyric polypropylenimine (DAB) dendrimer would allow the transport of plasmid DNA to the brain after intravenous administration.In this work, we demonstrated that the conjugation of lactoferrin to the dendrimer led to an enhanced DNA uptake by 2.1-fold in bEnd.3 murine brain capillary endothelial cells compared to the unmodified dendriplex in vitro. In vivo, the intravenous administration of lactoferrin-bearing DAB dendriplex resulted in a significantly increased gene expression in the brain, by more than 6.4-fold compared to that of DAB dendriplex, while decreasing gene expression in the lung and the kidneys. Gene expression in the brain was significantly higher than in any other major organs of the body. Lactoferrin-bearing generation 3 polypropylenimine dendrimer is therefore a highly promising delivery system for systemic gene delivery to the brain.
KEYWORDSBrain delivery; blood-brain barrier; gene expression; dendrimer; lactoferrin 2 1. Introduction Brain diseases, including glioma, Alzheimer's and Parkinson's diseases, currently represent one of the largest and fastest growing area of unmet clinical need. Brain cancer is the leading cause of cancer death in young people and accounts for more than one third of cancer deaths in children aged under 10. Alzheimer's disease is the most common type of dementia, affecting almost 500 000 people in the UK. The symptoms of this disease develop gradually and become more severe over the course of several years. In addition, there is currently no cure for Parkinson's disease, which affects 127 000 people in the UK [1][2][3][4]. Gene therapy has emerged as a promising therapeutic strategy, as the genetic basis for many of these diseases is known. However, the possibility of using genes as medicines to treat brain pathologies is limited by the lack of safe and efficacious delivery systems able to cross the blood-brain barrier (BBB) and to deliver DNA to the brain after intravenous administration, without secondary effects to healthy tissues. In addition, locally administered treatments fail to achieve a widespread gene expression in the target cells throughout the entire brain, which is necessary for a successful treatment of most brain pathologies [2-3, 5]. There is therefore an urgent need to develop safe and efficacious non-viral gene-based nanomedicines able to cross the BBB after intravenous administration, in order to ultimately provide better treatment options for brain diseases than currently available. Despite acting as an entrance gateway to the brain, the BBB does...