s:** - Compare uptake with/without magnetic particles using tight junction integrity markers - Test whether clustering occurs at BBB-relevant TfR expr

SUMMARY

# s:** - Compare uptake with/without magnetic particles using tight junction integrity markers - Test whether clustering occurs at BBB-relevant TfR expr ## Background and Rationale # Magnetic Particle-Enhanced Transcytosis at the Blood-Brain Barrier: A Falsification Study of Tight Junction Integrity and Transferrin Receptor Clustering The blood-brain barrier (BBB) represents one of the most significant obstacles to effective neurotherapeutic delivery, with tight junction (TJ) proteins forming t

METHODOLOGY NOTES

**Phase 1: Cell Culture Preparation (Days 1-7)** • Culture brain microvascular endothelial cells (hCMEC/D3 or bEnd.3) on Transwell inserts (0.4 μm pore, 24-well format) • Maintain cells in EBM-2 medium with 2.5% FBS and growth supplements • Allow monolayer formation for 5-7 days until TEER >150 Ω·cm² • Confirm tight junction integrity using immunofluorescence for ZO-1, claudin-5, and occludin • Validate TfR expression levels via Western blot and flow cytometry (target: 50,000-100,000 receptors/cell) **Phase 2: Magnetic Nanoparticle Preparation (Day 6)** • Prepare transferrin-conjugated magnetic nanoparticles (50-100 nm diameter) • Synthesize control transferrin without magnetic core • Characterize particle size, zeta potential, and transferrin conjugation efficiency • Prepare fluorescently-labeled molecular tracers: FITC-dextran (4 kDa, paracellular) and Alexa647-transferrin (transcytosis) • Sterilize all preparations via 0.22 μm filtration **Phase 3: Transport Assay Setup (Day 7)**