Collagen biomaterial can be heparinised for Growth Factor delivery. Other than the most common EDC/NHS method to heparinise collagen, what are the other methods in vitro? In some study collagen and heparin are layer-by-layer assembled just utilising physical absorption (opposite charge), how long can this physical immobolisation last?

In vivo, collagen in ECM can also be heparinised as a storage and inhibitor for growth factor. How is collagen heparinised in vivo?

In heparinisation in vitro, is the heparin connected to the same site on collagen for heparinisation in vivo?

Any important material in collagen heparinisation is very welcomed.

Thank you!