Colorimetric detection of estrogen using gold nanoparticles is susceptible to microbial matrix interference

Nanobiosensors are an emerging technology with fantastic potential to replace the traditional chromatographic workflows, which are used almost exclusively to measure environmental organic micropollutants. However, lack of widespread implementation within environmental research and monitoring suggests there may be a gap in the use case of the technology. Biological degradation is seen as one of the most effective approaches towards removal of environmental micropollutants, and thus, rapid measurement of degradation supports clean water strategies and meeting of key UN Sustainable Development Goals. While nanobiosensors based on aptamers and gold nanoparticles (AuNPs) have been extensively developed towards environmental water samples, here we seek to demonstrate the use of the technology for measuring micropollutants in microbial degradation systems. Using estrogen as a model contaminant, we adapted the colorimetric AuNP aptasensor mechanism of aggregation by exploiting the intrinsic high ionic strength of the sample matrix, biological culture media. The developed aptasensor allows for accurate and precise quantitation of E2 from 15 μM in minimal salts media, with an extended working range thanks to a cyclodextrin-based supramolecular complexation strategy. We then evaluated the biological selectivity of the assay in the presence of two estrogen-degrading bacteria, N. europaea and C. tardaugens. Each interfered with AuNP aggregation via a different mechanism, and through rigorous evaluation of the analytical performance and biological selectivity, we can posit that AuNP-based biosensors which rely on particle aggregation must overcome the high osmolarity of the sample matrix and biological interferences to be fit for purpose in measuring micropollutants in biodegradation systems. From this work we suggest strategies for future rapid appraisal of biological micropollutant degregation.