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A novel competitive photoelectrochemical aptasensor for thrombin (TB) detection is proposed using TiO 2 electrode coupled with TB-Au nanoparticles (AuNPs)–glucose oxidase (GOx) labels. To construct the aptasensor, chitosan was coated on the TiO 2 surface for the further immobilization of TB aptamer that was bridged by the use of glutaraldehyde. TB detection was then performed based upon the competitive interaction of TB and TB-AuNPs-GOx bioconjugate with TB aptamer on the electrode. GOx could catalyze the glucose to produce H 2 O 2 , which acts as an effective electron donor to deplete the photogenerated holes located at the valence band of excited TiO 2 , resulting in the enhanced photocurrent response. Under the optimal conditions, the as-prepared PEC aptasensor exhibits excellent analytical property for detection of TB in the range from 1.0 × 10 − 12 mol L − 1 to 1.0 × 10 − 8 mol L − 1 with a detection limit of 1.9 × 10 − 13 mol L − 1 . Moreover, the aptasensor was also successfully applied for the determination of TB in human plasma. The present strategy provides a promising method for the future development of PEC aptasensor for advanced biochemical analysis. [ABSTRACT FROM AUTHOR]

This work describes a novel electrochemiluminescence aptasensor for highly sensitive detection of platelet-derived growth factor BB (PDGF-BB) using aptamer functionalized CdS quantum dots–polyamidoamine as probe (CdS QDs–PAMAM–Apt). CdS QDs–PAMAM nanocomposites were synthesized by one-pot synthesis in methanol. The prepared nanocomposites were linked with the NH 2 –aptamer 2 (Apt2) of PDGF-BB to form the CdS QDs–PAMAM–Apt2 probe by glutaraldehyde as coupling reagent. For constructing the aptasensor, MWCNTs–chitosan composites and NH 2 –aptamer 1 (Apt1) with the same base sequence as Apt2 were immobilized on the electrode by the self-assembled method to recognize the target protein PDGF-BB. In the presence of PDGF-BB, the structure of sandwiched format was formed between the Apt1 and the CdS QDs–PAMAM–Apt2 probe, thereby resulting in a proportional increase of ECL emission. Thanks to the efficient and stable ECL emission of CdS QDs–PAMAM dendrimer and the advantage of MWCNTs for accelerating the electron transfer, the highly sensitive detection of PDGF-BB with a detection limit of 0.13 pM was achieved. The linear range is from 0.5 pM to 1 nM. The present protocol was applied to the analysis of PDGF-BB in human serum samples. The recoveries of PDGF-BB in human serum samples are 87.2–113% and RSD values are less than 3.6%. [ABSTRACT FROM AUTHOR]

A sandwich-type luminol electrochemiluminescence (ECL) aptasensor for highly sensitive and selective detection of platelet-derived growth factor BB (PDGF-BB) is fabricated. For this proposed ECL aptasensor, a multilayered AuNPs-electrochemically reduced graphene (AuNPs-EG) nanocomposite film was formed on the GCE surface as the base of the aptasensor through a co-electrodeposition method. The AuNPs-EG composites possess high conductivity to promote the electron transfer at the electrode interface and good biocompatibility and large surface area to capture large amounts of primary aptamer (Apt1), thus amplifying the detection response. Moreover, glucose oxidase (GOD) functionalized AuNPs labeled secondary aptamer (GOD–Apt2–AuNPs) was designed as the signal probe for the sandwiched aptasensor. Enhanced sensitivity was obtained by in situ generation of H 2 O 2 from reaction between GOD and glucose and the excellent catalytic behavior of AuNPs to the ECL of the luminol–H 2 O 2 system. Under the optimal conditions, the as-prepared ECL aptasensor exhibited excellent analytical property for the detection of PDGF-BB in the range from 1.0×10 –13 to 5.0×10 −10 mol L −1 with a detection limit of 1.7×10 –14 mol L −1 ( S / N =3). The application of the present protocol was demonstrated by analyzing PDGF-BB in human serum and human urine samples with the recoveries from 85.0% to 110%. [ABSTRACT FROM AUTHOR]

A novel label-free electrochemiluminescence (ECL) aptasensor for sensitive and selective detection of thrombin was constructed using Ru(bpy)3 2+ functionalized dopamine-melanin colloidal nanospheres (Dpa-melanin CNSs) and gold nanoparticles (AuNPs) as signal-amplifying tags. Dpa-melanin CNSs were synthesized by a simple chemical route. A large amount of Ru(bpy)3 2+ was coated over the Dpa-melanin CNSs with large surface area using Nafion as a bridge to form the Ru(bpy)3 2+/Nafion/Dpa-melanin CNSs composite which was considered as a sensing platform. AuNPs were introduced to the platform for immobilization of aptamer and further amplification of signal. A label-free ECL aptasensor for thrombin detection was subsequently fabricated by assembling aptamer on AuNPs/Ru(bpy)3 2+/Nafion/Dpa-melanin CNSs modified electrode. Greatly enhanced sensitivity is achieved based on the dual signal amplification strategy. The high sensitive detection of thrombin could be realized and the detection limit of thrombin was down to 2.2×10−13 M with a linear range from 1.0×10−12 to 1.0×10−9 M. The aptasensor was applied to the thrombin analysis of human plasma samples with recoveries of 86.0-97.7%. [ABSTRACT FROM AUTHOR]

A novel electrochemiluminescence (ECL) aptasensor based on CdS–MoS 2 nanocomposites was designed for detection of immunoglobulin E (IgE). The flowerlike CdS–MoS 2 composites were synthesized through a simple one-pot hydrothermal method. The CdS–MoS 2 composites were immobilized on glassy carbon electrode surface as ECL emitter attached a complementary ssDNA (NH 2 –ssDNA) of IgE. IgE aptamer (T-Apt) with DNAzyme–AuNPs can hybridize with NH 2 –ssDNA to form dsDNA. The DNAzyme with horseradish peroxidase-like activity could electrocatalyze the reduction of H 2 O 2 , the coreactant of CdS–MoS 2 ECL emission, leading to an obvious ECL quenching. In the presence of IgE, IgE conjugated with DNAzyme–AuNPs–T-Apt and thereafter the conjugations released, which decreased the consumption of H 2 O 2 by DNAzyme–AuNPs, produced an increased ECL signal. The changed ECL intensity is proportional to concentration of IgE in the range of 0.001–10.0 nM with the detection limit of 0.34 pM ( S / N = 3). The prepared aptasensor has been applied to determination of IgE in human serum samples. The recoveries of IgE in human serum samples are between 83.0% and 108% with the RSD values no more than 3.8%. The developed sensor with CdS–MoS 2 composites and DNAzyme features high sensitivity, good selectivity and wide linear range, suggesting the potential applications in biochemical analysis. [ABSTRACT FROM AUTHOR]

A label-free and ultrasensitive electrochemiluminescence (ECL) aptasensor was constructed for the detection of thrombin. Molybdenum sulfide–graphene nanocomposites with good conductivity and large surface area were immobilized on glassy carbon electrode (GCE), and then Nafion was fixed to chemosorb the Ru(bpy) 3 2+ used as luminescence agent. Subsequently, gold nanoparticles (AuNPs) were modified on the electrode to immobilize the thiol-modified thrombin aptamer for fabrication of the thrombin aptasensor. The proposed ECL aptasensor produced the ultrasensitive detection of thrombin with a low detection limit of 3.6 × 10 −15 M ( S / N = 3) and over a wide target concentration range from 1.0 × 10 −14 to 5.0 × 10 −9 M . The aptasensor has been successfully applied in the determination of thrombin in human plasma samples of both traumatic and non-traumatic injury patients, indicating its promise in biochemical analysis. The recoveries of thrombin in human plasma samples are between 88.6% and 105.0%, and the RSD values are no more than 3.7%. The results demonstrate that this aptasensor has excellent sensitivity, selectivity and stability. [ABSTRACT FROM AUTHOR]