Fabrication Of Electrochemiluminescence Aptasensor Based On Molybdenum Disulfide Nanocomposites And Its Applications

Electrochemiluminescence (ECL) presents several inherent advantages because of the combination of chemiluminescence and electrochemistry, such as high sensitivity, simplified setup, wide linear range and small analyte consumption and so on. Owing to QDs unique size-dependent electronic, optical, and electrochemical properties, ECL systems based on QDs have been widely studied for biological applications.Aptamers have many advantages over traditional recognition molecules, for example simpler synthesis, easier storage, lower cost, higher specificity, and wider applicability. These unique properties make aptamers ideal recognition elements for detecting the ligands. To date, they have been used widely for recognition, separation, and detection of various targets from small molecules to proteins, even whole cells.Nanomaterials, not only as a good matrix for proteins but also as biological labels for bioassay, have been developed rapidly to promote the progress of ECL biosensors because of their good biocompatibility and conductivity, the high surface areas, unique electronic and catalytic properties.This work combined the advantanges of ECL, QDs, aptamers and nanomaterials, the ECL aptasensors were fabricated for detection of proteins. The main investigations are as follows:1. In this work, we constructed a novel sandwich electrochemiluminescence (ECL) aptasensor for sensitive detection of thrombin based on molybdenum disulfide nanosheets-graphene (MoS2-GR) composites and Au nanoparticles. The MoS2-GR composites were characterized by SEM, TEM, XRD and Raman. In the protocol, MoS2-GR composites were firstly synthesized and assembled on the glassy carbon electrode (GCE) to promote the electron transfer. Subsequently, gold nanoparticles (AuNPs) were covered on the electrode to improve the immobilized amount of aptamerl (Aptl) and could further amplify the ECL signal as well. Afterwards, Aptl was conjugated to the electrode via Au-S bond. Finally, the target thrombin and the quantum dots labeled aptamer2(QDs-Apt2) as signal probe were successively attached to the GCE to fabricate a sandwich ECL aptasensor. With the excellent features of the MoS2-GR composites, AuNPs, and sandwich structure, multiple signal amplification for the ECL aptasensor has been achieved. The ECL intensity depended linearly on the logarithm of the thrombin concentration in the range from0.02to5.0pM and a detection limit of1.3fM (S/N=3). Furthermore, the aptasensor was successfully applied to the determination of thrombin in human plasma with the recoveries of90.0-102.4%and the RSDs of2.1-3.7%. The protocol could serve as a new tool for protein detection in biochemical analysis2. The molybdenum disulfide-gold nanoparticles (MoS2-AuNPs) composites were synthesized by the simple method of in situ growth of AuNPs on layered MoS2. The MoS2-AuNPs composites were characterized by scanning electron microscope and transmission electron microscopy. The results showed that the AuNPs were uniformly decorated on the layered MoS2. A sandwich ECL aptasensor was fabricated via layer-by-layer assembly for detection of platelet-derived growth factor BB (PDGF-BB) using MoS2-AuNPs composites as matrix and quantum dots as signal probe. The MoS2-AuNPs composites exhibited good conductivity and enhanced the immobilized amount of aptamerl and further generated amplified ECL signals. Under the optimal conditions, the ECL aptasensor has high sensitivity, selectivity and stability for PDGF-BB detection with a wider linear range from0.01pM to100pM and a lower detection limit of1.1fM (S/N=3). Moreover, the aptasensor has been used for determination of PDGF-BB in human serum samples with the recoveries of88.0-100.1%and the RSDs of1.6-4.3%. This work paves a novel way for functionalization of MoS2with AuNPs and provides a promising strategy for the development of various ECL aptasensor.