Development and benchtop testing of an aptamer-based sweat sensor for CRP detection

The development of an assay is presented for an aptamer-based flexible sensor aimed at the non-invasive detection of C-reactive protein in sweat that is passively perspired. CRP is a well-preserved plasma protein and a homopentameric acute-phase inflammatory protein crucial to the body's inflammatory responses. A significant advancement in this platform is the incorporation of aptamers, which provide notable benefits compared to conventional antibodies in biosensor applications. Incorporating aptamers enables the flexible sensor to deliver accurate and ongoing monitoring capabilities, converting cytokine binding into quantifiable electrical signals. The device's features render it especially effective for monitoring dynamic fluctuations in inflammatory biomarkers. This study presents the benchtop validation of a novel aptamer-based sensor designed to detect CRP in phosphate buffer solution (PBS) and human sweat. The dynamic range of CRP was established between 0.5 and 8.0 ng/mL, exhibiting a sensitivity of 0.22 ng/mL, while the limit of quantification (LOQ) was determined to be 0.65 ng/mL. Studies on cocktails have confirmed that the sensor showed no significant interference from biomarkers such as TNF-α, IL6, and IL8 for the CRP sensor. The evaluation of the flexible sensor demonstrated its capability to detect biomarkers in human sweat samples with impressive accuracy in approximately 3 min of incubation. The limits of detection and quantification were 1.20 ng/mL and 3.60 ng/mL, respectively. The sensing mechanism of the flexible sensor indicates that the interaction between the biomarker and the aptamer on the electrode surface modifies the electrical characteristics of the interface. This alteration generally results in a more conductive pathway, attributed to conformational changes in the aptamer, which facilitate an increased transfer of electrons between the electrode and the solution, ultimately resulting in a reduced impedance reading.