Antibody- and enzyme-free point-of-care detection of procalcitonin via synergistic nanomachines-activated catalytic assembly (SNCA) assay for early sepsis monitoring.

Procalcitonin (PCT) is an important biomarker for the early assessment and dynamic monitoring of sepsis. However, its routine measurement largely relies on centralized laboratory testing and protein-based recognition or signal-amplification components. Here, we developed an antibody- and enzyme-free synergistic nanomachines-activated catalytic assembly (SNCA) assay for rapid point-of-care detection of PCT. The assay integrates two functionally coupled nanomachines. The NanoTransducer consists of gold nanoparticles functionalized with an aptamer-based recognition probe carrying a catalyst strand. In cooperation with a second aptamer probe, it converts PCT-mediated dual recognition into nanoconfinement-triggered strand release. The released strand subsequently initiates catalytic hairpin assembly on a NanoAmplifier-loaded conductive PAAM/PA/PDA hydrogel electrode, producing an amplified differential pulse voltammetric signal. The assay exhibited a linear response from 10-3 to 103 ng/mL, with a detection limit of 2.35 × 10-4 ng/mL, and showed good specificity against potential interferents. A disposable ready-to-use reaction cartridge and a miniaturized wireless electrochemical analyzer were further developed, enabling automated PCT measurement in 15 min. As the entire process operates without protein-based antibodies or enzymes, the reaction cartridges demonstrated good storage stability. Clinical evaluation showed excellent agreement between the SNCA assay and the central laboratory reference method, while point-of-care testing provided higher temporal resolution for tracking postoperative PCT dynamics.