I have recently started culturing primary human brain endothelial cells that were commercially purchased from cell biologics (https://cellbiologics.com/document/data-sheet/Human/Human/Human%20EC/H-6023.pdf). I have used their supplied coating solution (0.1% gelatine) and tried some other routine solutions such as collagen and collagen+fibronectin. They have currently been in culture for 5 days and are not wanting to attach to the coating matrix at all. Weirdly, they seem to be growing and multiplying happily but in suspension which is very non-endothelial cell like.

I have been "rescuing" cells from the floating media, however facing the same attachment issues over and over again. I will attach a few pictures here for reference.

I was just hoping to reach out and see if anyone has observed anything similar or have any advice for me.

Thanks for your help