Abstract
A novel sandwich-type electrochemical immunosensor using the new amino group functionalized silicoaluminophosphates molecular sieves (NH2-SAPO-34) supported Pd/Co nanoparticles (NH2-SAPO-34-Pd/Co NPs) as labels for the detection of bladder cancer biomarker nuclear matrix protein-22 (NMP-22) was developed in this work. The reduced graphene oxide-NH (rGO-NH) with good conductivity and large surface area was used to immobilize primary antibody (Ab1). Due to the excellent catalytic activity toward hydrogen peroxide, NH2-SAPO-34-Pd/Co NPs were used as labels and immobilized secondary antibody (Ab2) through adsorption capacity of Pd/Co NPs to protein. The immunosensor displayed a wide linear range (0.001–20 ng/mL) and low detection limit (0.33 pg/mL). Good reproducibility and stability have showed satisfying results in the analysis of clinical urine samples. This novel and ultrasensitive immunosensor may have the potential application in the detection of different tumor markers.
Highlights
Reduced graphene oxide, a two-dimensional nanomaterial consisted of sp2-hybridized carbon atoms to form a one-atom thick honeycomb lattice, has been considered as a promising candidate for electron-acceptor and electron-transfer material due to its excellent optical and electrical properties, which has been extensively studied in the field of electrochemical immunoassay[14,15,16,17,18]
The reduced graphene oxide-NH (rGO-NH) with large surface area was used to increase the amount of captured Ab1
The Scanning electron microscope (SEM) images (Fig. 2a,b) of the Reduced graphene oxide (rGO)-NH showed that the rGO-NH had a wrinkle paper-like structure with irregular size, further indicating the large surface area of rGO-NH
Summary
Reduced graphene oxide (rGO), a two-dimensional nanomaterial consisted of sp2-hybridized carbon atoms to form a one-atom thick honeycomb lattice, has been considered as a promising candidate for electron-acceptor and electron-transfer material due to its excellent optical and electrical properties, which has been extensively studied in the field of electrochemical immunoassay[14,15,16,17,18]. The silicoaluminophosphates molecular sieves (SAPO-34) with high stability, microporosity, large specific surface area and acid sites[32,33,34,35] can immobilize more Pd/Co nanoparticles and enhance the sensitivity of immunosensor. The novel amino group functionalized silicoaluminophosphates molecular sieves (NH2-SAPO-34) supported Pd/Co nanoparticles (NH2-SAPO34-Pd/Co NPs) were first used as labels of the secondary antibody (Ab2). A sandwich-type electrochemical immunosensor for the detection of NMP-22 was prepared by using NH2-SAPO-34-Pd/Co NPs as labels and rGO-NH as sensing platform for the signal amplification. The high catalysis of NH2-SAPO-34-Pd/Co NPs toward the reduction of H2O2 could improve the sensitivity of the immunosensor. A conventional three-electrode system was used for all electrochemical measurements: the modified glassy carbon electrode (GCE, 4 mm in diameter) as the working electrode, a saturated calomel electrode (SCE) as the reference electrode, and platinum wire electrode as the counter electrode
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