Applicability of cerebral open flow microperfusion and microdialysis to quantify a brain-penetrating nanobody in mice

The use of biologics in the therapeutic landscape has increased exponentially since last 3 decades. Nevertheless, patients with central nervous system (CNS) related disorders could not yet benefit from this revolution because blood-brain barrier (BBB) severely hampers entering brain. Considerable effort been put into generating methods to modulate or circumvent BBB for delivery therapeutics CNS. A promising strategy is receptor-mediated transcytosis (RMT). Recently, Wouters et al. (2020) discovered a mouse anti-transferrin receptor nanobody that able deliver biologically active peptide brain via RMT. present study aims sample derivative brain-penetrating (Nb105) Therefore, we compared applicability cerebral open flow microperfusion (cOFM) and microdialysis as sampling techniques directly obtain high molecular weight substances interstitial fluid. custom AlphaScreen™ assay was validated quantify concentrations samples. In vitro probe (AtmosLM™, 1 MDa cut-off) recovery by gain loss Nb105 18.3 ± 3.2% 27.0 2.5% respectively, whereas cOFM it 87.2 4.0% 97.3 1.6%. Although large difference observed between microdialysis, vivo similar results were obtained. Immunohistochemical stainings showed an astrocytic microglial reaction immediate vicinity along implantation track both types. Coronal sections higher fluorescein isothiocyanate-dextran immunoglobulin G extravasation around than after experiments, however leakage clearly limited positive control where disrupted. This first samples bispecific brain's fluid function time, providing pharmacokinetic profile nanobodies Furthermore, time performed awake freely moving mice, data on inflammation integrity Overall, work demonstrates that, while taking account (bio)analytical considerations, are suitable quantification