In conclusion, we successfully 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. Our biosensor is simple, fast, cheap, and sensitive to detect heavy metal contamination by measuring the change in temperature after dipping the biosensor in a sample. We demonstrated the performance of our biosensor on five common heavy metal salts and observed different responses in terms of temperature change and color change. We also discussed the limitations and challenges of our biosensor, such as low selectivity and sensitivity, and proposed some possible solutions and enhancements, such as coupling it with electronic devices or modifying it with different enzymes or nanoparticles. Our biosensor has a broad spectrum of applications for various industrial sectors that need to monitor and control the heavy metal contamination in their products or processes. We invite experimentalists from different industrial sectors to perform this experiment as it may help them to increase the efficiency and accuracy of their concerned section.