Caspases play an important role as mediators of cell death in acute and chronic neurological disorders. Although peptide inhibitors of
caspases provide neuroprotection, they have to be administered intracerebroventricularly because they cannot cross the blood–brain
barrier (BBB). Herein, we present a nanocarrier system that can transfer chitosan nanospheres loaded with N-benzyloxycarbonyl-
Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl ketone (Z-DEVD-FMK), a relatively specific caspase-3 inhibitor, across BBB.
Caspase-3 was chosen as a pharmacological target because of its central role in cell death. Polyethylene glycol-coated nanospheres were
conjugated to an anti-mouse transferrin receptor monoclonal antibody (TfRMAb) that selectively recognizes the TfR type 1 on the
cerebral vasculature. We demonstrate with intravital microscopy that this nanomedicine is rapidly transported across the BBB without
being measurably taken up by liver and spleen. Pre- or post-treatment (2 h) with intravenously injected Z-DEVD-FMK-loaded nano-
spheres dose dependently decreased the infarct volume, neurological deficit, and ischemia-induced caspase-3 activity in mice subjected
to 2 h of MCA occlusion and 24 h of reperfusion, suggesting that they released an amount of peptide sufficient to inhibit caspase activity.
Similarly,nanospheresinhibitedphysiologicalcaspase-3activityduringdevelopmentintheneonatalmousecerebellumonpostnatalday
17afterclosureoftheBBB.NeithernanospheresfunctionalizedwithTfRMAbbutnotloadedwithZ-DEVD-FMKnornanosphereslacking
TfRMAb but loaded with Z-DEVD-FMK had any effect on either paradigm, suggesting that inhibition of caspase activity and subsequent
neuroprotection were due to efficient penetration of the peptide into brain. Thus, chitosan nanospheres open new and exciting oppor-
tunities for brain delivery of biologically active peptides that are useful for the treatment of CNS disorders.
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