Gold-silica hybrid nanolabels decorated with recognition and signaling bioreagents for enhanced electrochemical immunodetection of chemokine ligand-12 in colorectal cancer early diagnosis and monitoring.

The use of gold-silica nanoconjugates (Au@SiO₂NCs) decorated with biotinylated detection antibodies (b-dAb) and horseradish peroxidase (HRP) is reported for the improved electrochemical immunosensing of chemokine ligand-12 (CXCL12), a relevant chemokine implicated in colorectal cancer (CRC) progression. Implemented on an amperometric sandwich immunoplatform the resulting nanobioconjugates provided significant signal amplification which is attributed to the high enzyme loading capacity and improved antibody orientation. The role played by each of the nanomaterials forming the nanohybrid was evaluated. Under optimized conditions, the developed immunoplatform exhibited a linear response ranging from 72 to 1000 pg mL, a 4 times higher sensitivity than the conventional labeling-based immunoplatform, a LOD of 22 pg mL, and a storage stability of 1 month. The immunoplatform was applied to the determination of CXCL12 in plasma from healthy individuals and CRC patients. The clinically relevant results obtained demonstrate the potential of plasma CXCL12 levels as a biomarker for both the early diagnosis of CRC and the monitoring of its progression.