I'm also interviewing at BU, Northeastern, and Emerson!
As someone who's had a bunch of job interviews in the past few years (I'm an out-of-field applicant, and mainly worked in schools prior to this year), I'd wear anything that's professional and appropriate that you feel comfortable in. For me, that's a pencil skirt and blouse, with black tights and ankle boots. For someone else, it could look totally different. Basically, wear something that's, like, one step fancier than you'd usually wear to work or clinic. I wouldn't wear a skirt if you usually never do, or flats if you prefer heels, for example.
As bags go, I'm planning to bring a smallish purse to keep my phone, chapstick, and any papers I'm given in. I'm also planning on bringing a notebook with a folder pocket in it, to hold my CV. I don't think we'll need our CVs (in fact, one of my professors said that we probably wouldn't), but better safe than sorry. I was just going to carry the notebook in my hand, but that's not for any professional reason--I just like to have something to hold on to.
And best of luck for your interviews!