Photothermal Paper-Based Microfluidic Analytical Device Integrated with Carbon Nanomaterials and Molecularly Imprinted Polymers for Sensitive Perfluorooctanesulfonate Quantification

The global prevalence of perfluoroalkyl and polyfluoroalkyl substance (PFAS) contamination highlights the need for sensitive, accessible, simple, and cost-effective analytical tools. In this article, we present the first photothermal-based microfluidic paper-based analytical device (PT-μPAD) for the detection of perfluorooctanesulfonate (PFOS), one of the most widespread PFAS, in various matrices, including water, food, and human samples. By integration of a molecularly imprinted polymer (MIP) with carbon dots (CDs), the device achieves selective and sensitive PFOS monitoring by measuring the temperature change on the μPAD sensor. Additionally, the detection signal is rapidly obtained via a wireless near-field communication (NFC) system embedded in a portable and user-friendly platform. Under optimization, the developed sensor delivers a linear range between 1.5 and 7.0 pg mL^-1 (R² = 0.9989) and a detection limit (limit of detection (LOD)) of 7.0 fg mL^-1. Our developed sensor also exhibits high selectivity, with no observed interferent effects. The method also demonstrates remarkable accuracy and precision for PFOS quantification across real-world samples, achieving recovery percentages of 92.5-110.0% and the highest relative standard deviation (RSD) of 7.3%. Correspondingly, the results obtained using our method are comparable to those from the high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) method, as confirmed by a 95% confidence level in the t test analysis. Therefore, this sensor is well-suited for PFOS monitoring across various sample matrices, offering key advantages, such as simplicity, cost-effectiveness, portability, and ease of use by unskilled operators. Overall, this approach can be extended to the detection of other target molecules through MIP modification, showing its versatility. Furthermore, this concept holds great potential for broader applications, including medical point-of-care (POC) diagnostics and prognostics, on-site environmental analysis, and food safety.