µPAD-based colorimetric nanogold aptasensor for CRP and IL-6 detection as sepsis biomarkers

Point-of-care testing is defined as medical diagnostic testing at or near the time and place of a patient. The integration of microfluidics with functionalized nanomaterials provides a rapid and sensitive detection method for biomarkers. Due to their optical characteristics, gold nanoparticles (GNPs) and aptamers can be used in a colorimetric technique. In this research, accurate and quick aptasensors were created using aptamers for two sepsis biomarkers, interleukin-6 (IL-6) and C-reactive protein (CRP). Aptamers were combined with GNPs to create aptasensors, which were then used to analyze various biomarker concentrations after aptamer-protein docking on the online HDOCK server to verify aptamer-protein interactions. To improve the results' stability and ease of use during the reaction time, microfluidic paper-based analytical devices (µPAD) was employed. The linear diagnostic ranges in this method were 50–1000 mg L−1 and 1–25 ng/L, and limit of detection values were 1.9 mg L−1 and 0.07 ng/L for CRP and IL-6, respectively; These values decreased when µPADs were used and became more suitable to diagnosis of sepsis. Two aptasensors were highly stable, reproducible, accurate, and recoverable. Our result suggests that colorimetric GNPs can be used to detect a specific analyte through color changes visible to the naked eye for monitoring purposes or as simple optical detectors for quantitative measurements.