Quantum dot-modified aptamer probe for chemiluminescence detection of carcino-embryonic antigen using capillary electrophoresis

• A new method is proposed for determination of carcino-embryonic antigen (CEA) based on quantum dot (QD)-modified aptamer probe by capillary electrophoresis-chemiluminescence (CE-CL) detection system.

A new method is proposed for determination of carcino-embryonic antigen (CEA) based on quantum dot (QD)-modified aptamer probe by capillary electrophoresis-chemiluminescence (CE-CL) detection system. An oligonucleotide sequence A contains two parts, one is CEA aptamer and the other is bridging segment. Horseradish peroxidase (HRP) conjugates with sequence A (HRP-DNAA) and then mixes with QD labeling complementary bridging segment (QD-DNAB), forming HRP-DNAA-B-QD probe. When CEA exists, the specific combination of the aptamer in sequence A and CEA can form CEA/HRP-DNAA-B-QD complex. After separation of CEA/HRP-DNAA-B-QD complex and HRP-DNAA-B-QD probe by capillary electrophoresis (CE), the chemiluminescence (CL) catalyzed by CEA/HRP-DNAA-B-QD complex can be detected without any interference, and the content of CEA can be estimated by the CL intensity. It has been proved that the separation efficiency of HRP-DNAA-B-QD and CEA/HRP-DNAA-B-QD complex is improved greatly after QD modification, then the interference issue resulted from free HRP-DNAA-B-QD probe is solved well; and the specific combination of HRP-DNAA-B-QD and CEA leads to a closer distance of HRP and QD, then chemiluminescent resonance energy transfer (CRET) occurs, which confirms the validity of the strategy. Results show that the CL intensity has a linear relationship with the concentration of CEA in the range from 0.0654 to 6.54 ng/mL, and the limit of detection is approximately 8 pg/mL (S/N = 3). This proposed method with high specificity has been applied for the accurate analysis of content of CEA in patient's serum.