Does one need to be concerned with the remote possibility that chomatz may have gotten on the floor from soles of shoes?

Shalom U'vracha, There is no need to worry about that. Even if there was a crumb that got onto the floor of the house, it was most likely inedible for a dog to eat. Therefore, it is no longer considered chametz. Even if the crumb is, in fact, edible for a dog, it is highly unlikely that it will get stuck to your apple (if the apple falls to the floor). Finally, you have no intention (kavanah) to eat it, should the apple have a chametz crumb stuck to it. To sum it up: There is no suspicion here ('chashash') of eating chametz. Wishing you a most happy summer!