Multi-enzyme layer-by-layer assembly for dual amplified ultrasensitive electronic detection of cancer biomarkers

The preparation and use of multi-enzyme layer-by-layer (LBL) assembled single wall carbon nanotube (SWCNT) composite labels for amplified ultrasensitive electrochemical detection of a cancer biomarker is described. The target protein, carcinoembryonic antigen (CEA), is sandwiched between an electrode surface-confined capture anti-CEA antibody and the secondary signal anti-CEA/enzyme-LBL/SWCNT bioconjugate. The dual biocatalytic signal amplification for CEA monitoring is achieved through both the numerous enzymes loaded on the CNTs and redox-recycling of the enzymatic products in the presence of the secondary enzyme and the corresponding substrate. Our novel dramatic signal amplification strategy, with a detection limit of 0.04 pg mL−1, shows about 2–4 orders of magnitude improvement in sensitivity for CEA detection compared with other universal signal amplified assays, which makes our signal amplification approach hold great potential applications in detection of ultra-trace protein biomarkers.