Highly active DNAzyme-peptide hybrid structure coupled porous palladium for high-performance electrochemical aptasensing platform

Herein, we developed a high-performance electrochemical aptasensor for the detection of carcinoembryonic antigen (CEA) using highly active peptide-conjugated hemin/G-quadruplex (hGQ-peptide) and porous Pd nanoparticles (PdNPs). Of note, the hGQ-peptide showed an enhanced catalytic activity as compared to the unmodified hGQ, and thus served as efficient electrocatalyst in this biosensor. Porous PdNPs acted as supported matrixes for high immobilization of hGQ-peptide hybrids, aptamer, redox-active toluidine blue (Tb) and alcohol dehydrogenase (ADH), resulting in the formation of ADH/Tb/hGQ-peptide/aptamer/PdNPs as the proposed bioprobes. Upon the sandwich-type specific reaction between aptamer and CEA, the bioprobe was presented on the sensing interface. Highly effective signal amplification could be then achieved by the bioprobe catalyzed cascade enzymatic reaction. Compared with the original hGQ, the hGQ-peptide yielded more than 2-fold improvement in signal amplification because of the peptide-enhanced catalysis. Therefore, the designed aptasensor displayed a wide linear range from 0.0001 to 100 ng mL−1 with a lower detection limit of 20 fg mL−1 for CEA determination, presenting the better analytical performance as compared to the relevant prior biosensors. This work further expanded the application of hGQ DNAzyme in biosensor. With the good anti-interference ability and selectivity, the proposed electrochemical aptasensor held great promise for ultrasensitive detection of other proteins in clinical diagnosis.