In this study, we developed an enzyme-based nanobiosensor for detecting heavy metals using sol-gel synthesis of selenium oxide nanoparticles and crude protease enzyme extract from chicken intestine. The biosensor works by measuring the change in temperature after dipping the biosensor in a sample containing heavy metals. The change in temperature reflects the interaction between the heavy metals and the enzyme, which alters its catalytic activity and heat production . We chose selenium oxide nanoparticles as the nanomaterial for our biosensor because of their high binding affinity with heavy metals such as mercury, which facilitates the detection process . We also chose protease enzyme as the biorecognition element for our biosensor because of its wide availability and low cost. Protease enzyme is an enzyme that catalyzes the hydrolysis of peptide bonds in proteins . Heavy metals can affect the structure and function of protease enzyme by binding to its thiol groups or other active sites, which results in changes in its catalytic activity and heat production .In pursuit of sustainability and cost-effectiveness, we innovatively synthesized a crude protease enzyme extracted from chicken intestine. This strategic approach aimed at harnessing enzymatic activity efficiently for the development of our biosensors designed to detect heavy metals in food samples. Figure illustrates the globular structure of the protease enzyme. We tested our biosensor on five common heavy metal salts: chromic chloride (CrCl3), copper (II) sulfate (CuSO4), mercuric chloride (HgCl2), cadmium carbonate (CdCO3), and arsenic chloride (AsCl3). We observed different responses of our biosensor to these heavy metal salts in terms of temperature change and color change. We also discussed the limitations and challenges of our biosensor, such as low selectivity and sensitivity for different heavy metals. We suggested some potential improvements and applications of our biosensor for various industrial sectors that need to monitor and control the heavy metal contamination in their products or processes.