Using polyHRP to produce simplified immunoassays and electrochemical immunosensors. Application to MMP-9 detection in plasma and uterine aspirates

Immunoassays and immunosensors are extensively described diagnostic tools. However, they often entail time-consuming multi-step procedures that are difficult to perform outside centralized diagnostic laboratories, such as at point-of-care settings, where extremely simple assay paths are required. In this work, a commercial polymeric enzyme, polyHRP, has been used as a signal amplifier for detection of matrix metalloproteinase 9 (MMP-9). Contrary to previous reports, signal enhancement has been exploited here to reduce the number and duration of the steps of a classical multistep enzyme-linked immunosorbent assay (ELISA) while retaining its original sensitivity. The two assay formats produced, a simplified ELISA and an electrochemical immunosensor, could be carried out in about 1 h and 45 min, respectively, but detected MMP-9 with linear range, limit of detection (LOD), limit of quantification (LOQ), sensitivity, and variability comparable to the original ELISA that took >5 h, and quantitated successfully MMP-9 in plasma samples and uterine aspirates from patients. These results demonstrate that the implementation of signal amplifiers, such as polyHRP, allows the optimization of simplified immunoassays, maintaining the high performance obtained with longer multi-step paths. Furthermore, the strategy reported is extremely simple and potentially implemented elsewhere by other researchers with minimal technical requirements.