Self-amplifying cascade-triggered Au NP assembly strategy for ultrasensitive cTnI detection with dynamic light scattering

Abstract

Here, we report an ultrasensitive dynamic light scattering (DLS) immunosensor for cardiac troponin I (cTnI) that leverages a novel self-cascading reaction synergistic amplification strategy by using metal organic framework (MOF) materials. This synergistic amplification system was designed to combine enzymatic (glucose oxidase, GOD) catalysis, acid-responsive MOF disintegration, Fenton reaction and gold nanoparticle (Au NP) stability modulation. When the target cTnI was present, a sandwich structure was formed between the multifunctional probes (Ab-GOD/Fe-MOF) and the Ab-modified 96-well plates, which subsequently induced self-cascading reactions upon further addition of glucose. In the process, glucose was oxidized to gluconic acid (creating an acidic micro-environment) by O₂ under the catalysis of MOF-conjugated GOD and produced H₂O₂, and the acidic micro-environment triggered the breakdown of Fe-MOF and the release of Fe²⁺, which reacted with H₂O₂ via the Fenton reaction to etch the protective DNA layer that modified the Au NPs, enabling the salt-induced aggregation of the AuNPs. Crucially, the DLS assay achieved a low limit of detection (LOD) of 1.5 × 10⁻¹³ g mL⁻¹. Furthermore, this cascade amplification strategy realized the quantitative detection of cTnI in clinical samples with high sensitivity and specificity.