Development of a Gold Nanoparticle-Based Colorimetric Sensor for Water for Injection At-Line Impurity Testing

The best-known rapid test using gold nanoparticles (AuNPs) is the human chorionic gonadotropin pregnancy test. AuNPs are a powerful tool in point-of-care testing because of their flexibility, modifiability, and visibility. Here, we report a method to detect impurities for at-line process control in water-for-injection (WFI) manufacturing through the example of endotoxins. If a distinct concentration of these amphipathic molecules, originated from gram-negative bacteria, enters the human body, it will result in septic shock, followed by organ failure and possibly death. Every fluid given parenterally is subject to strict regulatory requirements and therefore endotoxin testing. Through use of traditional methods like the limulus amebocyte lysate (LAL) test, it takes more than 2 h to complete. With the presented method, one-fifth of the sample volume is sufficient compared with the LAL test. Once the assay components have been mixed, the result can be interpreted visually within 2 min without the use of further instruments.