Question about using public domain characters that are still trademarked in a new fiction novel

I found this in a couple places, but I'm still confused, and have a specific question that I have not found an answer to about story characters and using them in a new book. My question is, if a character from an old novel is now in the public domain, and so is that book, but that character is trademarked, can I use those characters as secondary supporting characters (not my main protagonist) in my fiction novel? I'm trying to write a book with multiple public domain worlds where my own protagonist goes in and out of them in a portal-like system. I researched all the characters I want to use, which are all public domain, but they are also trademarked, and I'm still confused about that. I'm not planning on using the trademarked characters in an odd way, like making Peter Pan a serial killer. I want to stay as true to these characters as possible, but put new sentences in their mouths, relevant to my plot, and have my own protagonist enter their story worlds, wile being as true to the public domain novels setting as possible. Can I do this? I'm not planning on putting these trademarked characters' names on the front cover of my novel, or as part of my title. Thank you so much for all your help!