A nanoengineered peptidic delivery system with specificity for human brain capillary endothelial cells

The blood–brain-barrier (BBB) is a formidable obstacle for successful translocation of many drug molecules from the systemic circulation into the brain, and therefore a major challenge for neurotherapeutics. Nanoparticles may offer some opportunities for delivery of bioactive molecules into brain, without manipulating the integrity of the BBB. This may be achieved by simultaneous and appropriate nanoparticle surface decoration with polymers that protect nanoparticles against rapid interception by body's defenses and ligands specific for cerebral capillary endothelial cells. To date, the binding avidity of the majority of the so-called ‘brain-specific’ nanoparticles to the brain capillary endothelial cells has been poor, even during in vitro conditions. We have addressed this issue and designed a versatile peptidic nanoplatform with high binding avidity to the human cerebral capillary endothelial cells. This was achieved by selecting an appropriate phage-derived peptide with high specificity for human brain capillary endothelial cells, which following careful structural modifications spontaneously formed a nanoparticle-fiber network. The peptidic network was characterized fully and its uptake by the human brain capillary endothelial cell line hCMEC/D3 was confirmed by live-cell fluorescent microscopy and quantified by flow cytometry. Recognition and internalization was medicated by two receptors leading to endolysosomal accumulation. Furthermore, the network was capable of delivering functional siRNAs to hCMEC/D3 cells, which resulted in unprecedented silencing and with negligible cytotoxicity. These observations have important implications for design and engineering of brain-endothelial cell-specific nanosystems for controlled delivery and release of biologics for treatment of diseases and disorders of the central nervous system.