Sorry to hear about your transplant failure.
When and where was your transplant done? Was it done by a qualified surgeon? If it is under one year dont lose hope. The hair may still grow if the transplant was performed properly.
of any good brand should be fine. You can ask your doc about alternate options. I hope you are also using Minoxidil
with it. If not consult your surgeon regarding these. Biotin alone is not capable of preventing hair thinning.