The main principle of our nanobiosensor is that it can detect the presence of heavy metals in a sample by measuring the change in temperature after the biosensor is dipped in the sample. This is based on the assumption that heavy metals can interact with the protease enzyme in the biosensor and alter its catalytic activity, which in turn affects the heat production. This principle is based on the concept of nanozymes, which are nanomaterials that display enzyme-like properties and can catalyze reactions. In the context of this biosensor, the protease enzyme acts as a nanozyme that interacts with heavy metals. When heavy metals are present in a sample, they interact with the protease enzyme, altering its catalytic activity. This alteration in catalytic activity leads to heat production, which can be measured as a change in temperature .