Femtomolar-level detection of procalcitonin using a split aptamer-based fiber optic nanogold-linked sorbent assay for diagnosis of sepsis.

Sepsis requires very sensitive and rapid detection of biomarkers to guide antibiotic therapy to lower the patient mortality rate. Here, we report an ultrasensitive, rapid, and low-cost method for detection of the most popular sepsis biomarker, procalcitonin (PCT), based on a split aptamer-based fiber optic nanogold-linked sorbent assay. After successful development of a novel aptamer for PCT by SELEX, a pair of split aptamer fragments from the parent aptamer was predicted through molecular interaction simulation via free webservers. Then one fragment (AptF1) is modified on a sensor fiber and the other fragment (AptF2) is conjugated to a gold nanoparticle (AuNP@AptF2). The interactions among PCT and the two aptamer fragments lead to the formation of a AuNP@AptF2-PCT-AptF1 sandwich-like nanocomplex on the fiber core surface, leading to strong nanoplasmonic absorption near the fiber core surface. This method provides a linear response ranging from 500 fg/mL to 5.0 ng/mL and a detection limit of 50 fg/mL (3.9 fM). The method had been validated against the clinical accepted electrochemiluminescence immunoassay using clinical samples and very good correlation between the results by both methods was found. Therefore, this method offers a potential for point-of-care diagnosis of sepsis.