Saint-Maximin has been outstanding for the Magpies this season and is attracting interest from elsewhere.
Bruce, who has also seen Miguel Almiron linked with Atletico Madrid, said: "To be linked with other clubs, they have to be performing well. My job is to make sure they keep performing well and then let that other stuff look after itself.
"They've only been here a short while and they've performed very well. Our job is to keep our best players. We certainly don't want to be losing them – we want to be building around them and that's the plan."
He added: "Allan has only just arrived here. He signed a six-year deal in the summer. If people are talking about him, good. It means he's doing it on the pitch. That's all they can focus on and let the rest look after themselves."