How to Set a bool to Individual Scenes (C#)

I am making a game in c# and have been stuck on this for hours now. I am trying to set a bool on a “key” object to true so that once it’s picked up it will disappear and not be able to be picked up again and again each time the scene is re-entered. The problem is that upon changing the bool for that one key to true, therefore destroying it after 1 key is picked up like I want, it destrouys all of the other keys in other scenes by changing their bool to true also. I was wondering if or how you could assign a bool to just one scene by having the same bool have different values depending on the level… if that makes sense. Heres the code for the destroy key-
public static bool isCollected = false;

	public void Update ()
	{
	if (isCollected == true) 
		{
		Destroy (this.gameObject);
		}
	}

So if the key isCollected is equal to true, then it gets destroyed, but that destroys all keys even though that code is attached to each one individually. Here’s the code for the player coming in contact with the key-

void DeleteKey ()
	{
		DestroyKey.isCollected = true;
	}

	if (other.transform.tag == "Key") 
        {
		manager.keyCount += 1;
		DeleteKey ();
	}

If anything is unclear, you need to see additional code from the game, or you need more details tell me. Thanks for the help.

Turn isCollected into a dictionary.
Then on the gameobject, have a string with the level name that is entered in through the inspector. Each level will then have it’s own key bool.

public String levelName;
public static Dictionary<String, bool> isCollected

------- in code
void DeleteKey ()
{
      isCollected[levelName] = true;
}

etc