Target-induced DNAzyme recycle amplification strategy for colorimetric detection of cystatin C

Cystatin C (Cys C) is an early biomarker of declining kidney function and is frequently detected during clinical diagnosis. However, existing assays are complex, lengthy, and expensive. To overcome these limitations, a dual DNAzyme-amplified assay for Cys C detection was developed using non-cross-linked aggregates of gold nanoparticles (AuNPs). Target-induced assembly of the two DNAzymes triggers a cascade of cleavage reactions, releasing complementary strands that hybridize with detection probes linked to the AuNPs, leading to enhanced plasmonic signals. The assay demonstrated a linear detection range of 2–32 ng/mL, with a detection limit of 1.1 ng/mL. Furthermore, the proposed method exhibited high specificity for Cys C detection, acceptable intra-assay precision, and robust stability. The assay was successfully applied to detect Cys C in serum samples, highlighting its potential for application in the diagnosis of acute kidney injury. The entire process, including aptamer biorecognition, DNA hybridization, and catalytic cleavage of DNAzymes, was performed in a homogeneous solution, thereby rendering the method highly straightforward and exhibiting high reproducibility.