Green Synthesized Gold Nanoparticles Using Olive Leaf Extract as an Electrochemical Sensor for Paracetamol and Aspirin in Pharmaceutical and Biological Samples

In the world of modern medicine, doctors and pharmacists rely on precise measurements to ensure that life-saving drugs are present in the right amounts and free from harmful contaminants. To achieve this, scientists use analytical tools that can detect tiny traces of chemicals in complex mixtures like blood, urine, or pill formulations. For decades, the gold standard for these measurements has been high-performance liquid chromatography, a technique that separates chemicals using powerful pumps and organic solvents. While effective, this method often generates significant chemical waste and requires expensive equipment. In recent years, a quieter revolution has been taking place in the field of green chemistry, which seeks to perform these necessary analyses using less energy, fewer toxic materials, and more sustainable resources. The goal is to create sensors that are not only accurate but also gentle on the environment, turning the very act of measurement into a practice that protects the planet.

This shift toward sustainability is the backdrop for a new study conducted by researchers at Najran University and the University of Tabuk in Saudi Arabia. The team set out to build a highly sensitive electronic sensor capable of detecting two of the most common pain relievers in the world: paracetamol and aspirin. Instead of using the harsh, toxic chemicals typically required to manufacture the tiny metal particles that make these sensors work, the scientists turned to nature. They harvested fresh olive leaves, a crop residue abundant in their region, and used an extract from these leaves to create gold nanoparticles. These nanoparticles are microscopic spheres of gold, so small that thousands could fit on the head of a pin, which act as powerful amplifiers for electrical signals. By using the olive leaf extract as both a reducing agent to turn gold ions into solid metal and a stabilizing agent to keep the particles from clumping, the researchers created a sensor that is both effective and environmentally friendly.

The process began with the careful preparation of the olive leaves. The researchers collected fresh leaves from mature trees in the Aljofe region, washed them thoroughly, and dried them in the shade to preserve their natural chemical properties. They then ground the dried leaves into a fine powder and boiled them in water to create a rich, brownish-yellow liquid extract. This extract is packed with natural compounds like phenols and flavonoids, which are known for their ability to donate electrons. When this extract was mixed with a solution containing gold salts and heated, a remarkable transformation occurred. The gold ions in the solution, which were initially pale yellow, rapidly turned a deep wine-red color. This color change signaled that the gold ions had been successfully reduced into solid nanoparticles, a process driven entirely by the natural chemicals in the olive leaves. The resulting nanoparticles were spherical, with an average diameter of about 19, and they remained stable in the solution without clumping together, thanks to the natural coating provided by the leaf extract.

To test if these nature-made nanoparticles could function as a sensor, the researchers deposited them onto a smooth glassy carbon electrode, a standard tool in electrochemical analysis. They then compared this new sensor against two other versions: one made with nanoparticles created using traditional chemical methods involving synthetic citrate, and a bare electrode with no nanoparticles at all. When they introduced paracetamol and aspirin to the sensor, the results were striking. The olive-leaf sensor was able to detect both drugs simultaneously with high precision. It identified paracetamol at concentrations as low as 0.032 micromolar and aspirin at 0.15 micromolar. These detection limits are comparable to, and in some cases better than, many sensors built with chemically synthesized nanoparticles. The sensor worked by measuring the electrical current generated when the drugs oxidized on the surface of the gold particles. The presence of the nanoparticles made this reaction happen much faster and at lower voltages than it would on a bare electrode, allowing the sensor to pick up even the faintest signals from the drugs.

The researchers did not stop at proving the sensor worked in a laboratory setting; they tested it on real-world samples to see if it could handle the complexity of actual medicines and human fluids. They analyzed commercial tablets of paracetamol and aspirin, dissolving them and measuring the drug content. The sensor's readings matched the labeled amounts on the bottles with an accuracy of over 98 percent, aligning closely with results from the standard laboratory chromatography method. They also tested the sensor on human urine and saliva samples that had been spiked with known amounts of the drugs. In these biological fluids, which contain many other substances that could interfere with the measurement, the sensor maintained its accuracy, recovering between 96.8 and 103.8 percent of the added drugs. This demonstrated that the olive-leaf nanoparticles were selective enough to ignore the background noise of salts, proteins, and other metabolites found in the body, focusing only on the target drugs.

A crucial part of this study was evaluating the environmental impact of the new method. The researchers used a specialized scoring system called AGREE, which rates analytical techniques based on twelve principles of green chemistry, such as waste reduction, energy efficiency, and the use of safe solvents. The sensor built with olive-leaf nanoparticles received an excellent score of 0.82 out of 1.0, placing it in the top tier of green analytical methods. In contrast, the sensor built with chemically synthesized nanoparticles scored 0.61, and the traditional liquid chromatography method scored only 0.38. The high score for the new sensor was largely due to its use of water as a solvent, the avoidance of toxic reducing agents, and the utilization of agricultural waste as a raw material. This quantitative assessment confirmed that the researchers had successfully created a sensing platform that does not compromise performance for the sake of the environment.

The study concludes that using olive leaf extract to synthesize gold nanoparticles offers a viable and sustainable path for building electrochemical sensors. The method transforms a common agricultural byproduct into a high-tech tool capable of monitoring drug levels in both pharmaceutical products and biological samples. While the researchers noted that further testing on authentic clinical samples from patients would be valuable, their current findings provide strong evidence that green synthesis can produce sensors that are just as reliable as those made with conventional chemistry. By integrating the principles of green chemistry with advanced nanotechnology, this work suggests a future where the tools used to protect human health are themselves designed to protect the planet.