Most certainly it could be, and in fact it is, a symbol.
In Elie Wiesel's autobiographical novel, Night, the prisoners of the concentration camp are kept under sub-human conditions. The sole fact that they are trapped receiving mistreatment, cruelty, and extreme humiliation is bad enough. To be surrounded by imminent death everywhere you look is nerve-wracking. The men know perfectly well that those barbed wires in the horizon represent death: A quick death. Everything else represents a slow, cruel, and lingering never-ending death both physical and psychological. The barb wire, to their disgrace, would have represented their only hope to at least die a fast death at their own hands, and not at the hands of the enemy.
Wiesel certainly thinks so, as he says in his own words:
I'll run into the electrified barbed wire. That would be easier than a slow death in the flames
Therefore, this unthinkable human crime is intensified by the symbols that are ever-present in their everyday mortified existence. The smell of the ovens, the shouts and noises, the scary SS soldiers, their own bodies becoming emaciated, the fear of death...and the barb wire staring down at them, tempting them to make the punishment end faster.
If you remember that symbol stands for or represents something else, yes, the barbed wire may be used as a symbol. To help you, think about what the barbed wire does; as a separation tool, it works perfectly. Now think about who Elie is separated from and how the fence could be a symbol of not only a physical separation, but a mental or emotional separation as well. He cannot hug his father, nor spend time with him as he would like to do and always with the threat of violence hanging in the air. He is also separated from the outside world.
The barbed wire is not only a fence but sharp and dangerous. When you think about Elie in a concentration camp, almost everything around him is sharp or dangerous; for example, the guns of guards, the sharp teeth of dogs, the need to do exactly as the guards demand or face dangerous consequences are all dangers to be faced.
I hope this helps you; keep reminding yourself about symbols representing something else which should help you do fine.