The blood-brain barrier(BBB)controls entry of cells and molecules from the blood to the brain.The BBB regulates cell migration,water permeability,ion concentrations and transport of metabolic products to maintain neural tissues homeostasis.Endothelial cells,lining capillaries of the BBB,are characterized by enhanced tight junctions(TJ),with astrocytes playing a major role in their maintenance.Models of BBB in vitro are essential tools to investigate brain vascular diseases,drug delivery to the brain and mechanisms of cell migration across the endothelial barrier.The majority of current BBB models use composed of plastic inserts with polymer membrane at the base.The plastic inserts are placed in culture well plates growing endothelial cells on the top and astrocytes on the bottom.We are investigating a 3D co-culture system using gelatin methacrylate(GelMA)hydrogel to create a BBB model by co-culture of endothelial and astrocytic cell lines with direct contact in a GelMA hydrogel.The astrocytic cells will be encapsulated in the GelMA hydrogel allowing for 3D spatial culture mimicking the basal aspect in vivo while the endothelial cells will be cultured on the surface of the GelMA hydrogel.This novel model will be compared to common co-culture BBB models on Transwell inserts and mono culture BBB models with astrocyte cell media(ACM).The models will be characterized by transendothelial electrical resistance(TEER)as a measure of barrier tightness,Evans blue for functional tightness,trans-endothelial migration of cancer cells and immunofluorscence staining of junctional proteins expressed at the BBB.