Design of A Novel Phosphohydrolase Mimic Enzyme And Its Enhanced Phosphohydrolase Activity for Rapid and Colorimetric Detection of Organophosphorus Pesticides

In the global effort to keep food safe, a persistent challenge involves the invisible traces of chemical pesticides that can linger on fruits and vegetables. Among these, a specific group known as organophosphorus pesticides is widely used to protect crops from insects, but their presence in food poses serious health risks to humans, including potential damage to the nervous system. Because these chemicals are so dangerous, international health organizations have set strict limits on how much can remain in the food supply. However, checking for these tiny amounts is difficult. The standard methods used in laboratories require massive, expensive machines and highly trained experts, making them too slow and costly for quick checks in the field. Scientists have long sought a simpler way to detect these poisons, often looking to nature for inspiration. In the human body, natural enzymes act as biological machines that can break down these harmful chemicals, but harvesting these natural enzymes is difficult, expensive, and they often lose their power when conditions change. This has led researchers to explore the creation of artificial versions, called nanozymes, which are tiny man-made structures designed to mimic the work of natural enzymes but with greater strength and stability.

A team of researchers at Zhengzhou University of Light Industry has now designed a new type of these artificial enzymes that works with surprising speed and precision. They created a material made of two distinct parts working together: a core of cerium oxide, a type of metal oxide, wrapped in a shell of a porous, cage-like structure called a metal-organic framework. The researchers named this new material CeO2@ZIF-90. Their goal was to build a machine that could not only break down the pesticide but also signal its presence in a way that is easy to see or measure. When this new material meets a specific pesticide called methyl parathion, it acts like a pair of molecular scissors, cutting the chemical apart. This cutting action transforms the invisible pesticide into a different substance called para-nitrophenol. This new substance is special because it turns a bright yellow color, making the invisible threat visible to the naked eye.

The researchers tested how well this new material worked by mixing it with the pesticide in a laboratory setting. They found that the material was highly effective at breaking down the chemical, producing a strong yellow color that could be measured with a simple light sensor. The more pesticide present in the sample, the more intense the yellow color became, allowing the team to calculate exactly how much poison was there. They discovered that this method could detect the pesticide in very small amounts, ranging from a tiny fraction of a millimole up to a slightly larger concentration, with a clear limit of detection that is low enough to be useful for food safety. To prove the material was not just a one-trick pony, the team also tested it using an electrical method. Because the yellow substance produced by the reaction can carry an electrical current, they attached the material to an electrode and measured the electrical signal. This second method was even more sensitive, capable of spotting even smaller traces of the pesticide, confirming that the material works well in two different ways at once.

One of the most important tests for any new sensor is whether it gets confused by other things. In a bowl of fruit juice or a sample of soil, there are many different chemicals that could trick a detector. The researchers tested their new material against a long list of common substances, including sugars, salts, and other types of pesticides. The results showed that the material was remarkably picky. It reacted strongly only to the specific pesticide it was designed to find, methyl parathion, and largely ignored the other chemicals. This high level of selectivity means that the sensor is unlikely to give a false alarm when used on real food. Furthermore, the material proved to be tough and reliable. It could be used repeatedly without losing its ability to work, and it remained effective even after being stored for nearly a month, suggesting it is stable enough for practical use outside of a controlled lab.

To see if this discovery could work in the real world, the team tested their method on actual food samples. They took celery, apples, and grapes and added small, known amounts of the pesticide to them. Using their new material, they were able to detect the added poison with high accuracy, recovering nearly all of the pesticide they had put in. This success in real food samples suggests that the method is ready to move beyond the laboratory and into the field. The researchers conclude that this new material offers a powerful tool for food safety. By combining the ability to break down the poison with the ability to detect it through color or electricity, the CeO2@ZIF-90 material provides a fast, cheap, and reliable way to monitor food for dangerous residues, potentially helping to protect consumers and ensure that the food on our tables is safe to eat.