| Electrochemiluminescence (ECL) sensor, due to their advantages such as good selectivity and high sensitivity, simple operation, easy portability, and easy to realize the advantages of miniaturization, has attracted many interesting of researchers. ECL aptasensor, using aptamers as recognition elements, is a very active area of research combined of biology, chemistry, physics, and information science. The selection and immobilization of ECL luminesces are the important implications for achieving ultra-sensitive ECL sensors. This article intends to solve the shortages of the ECL signal probe (ruthenium compounds), such as water-solubility, difficult immobilization with no functional groups and so on. Nanomaterials, used as carriers to immobilize the ECL reagents or bio-molecules through method of adsorption, doping or accumulation, can improve the efficiency of ECL reagents. A novel [Ru(phen)3]2+derivative, containing ECL reagents and co-reactant as the self-enhanced ECL reagent, can increase the efficiency of luminous for construction of ECL aptasensors. The detail contents are as follows:1 Supersandwich-type electrochemiluminescenct aptasensor based on [Ru(phen)3]2+ functionalized hollow gold nanoparticles as signal tagBased on the signal amplification of supersandwich structure, we designed an electrochemiluminescent (ECL) aptasensor by using of [Ru(phen)3]2+ as ECL luminophore for detection of thrombin (TB). Herein, hollow gold nanospheres (HGNPs) were employed as effective tag-carriers for the immobilization of aptamer (TBA) to form the HGNPs labeled TBA 2 (HGNPs-TBA 2). Subsequently, streptavidin (SA) was used to block the non-specific binding sites of HGNPs-TBA 2 and formed the SA-HGNPs-TBA 2, which could further introduce numerous initiator DNA strands (bio-S1) via biotin-streptavidin. In the supersandwich strategy, bio-S1 co-existed with ssDNA S2 and ssDNA S3 (S3 is partially complementary to the S2) could in situ trigger hybridization chain reaction (HCR) to create a long nicked double helices analogous (dsDNA). [Ru(phen)3]2+, a well-known ECL luminophore, could be intercalated into the grooves of dsDNA with high affinity (Ru-dsDAN) to form the Ru-dsDNA-SA-HGNPs-TBA 2 bioconjugate. Target TB was sandwiched between Ru-dsDAN-SA-HGNPs-TBA 2 and TBA 1. In this strategy, numerous [Ru(phen)3]2+ could be immobilized on the electrode based on the supersandwich structure, resulting in an increased ECL signal output. A supersandwich ECL assay for TB detection was developed with excellent sensitivity of a large concentration variation from 5 fmol L-1 to 50 pmol L-1 and a detection limit of 1.6 fmol L-12 Noncovalent [Ru(phen)3]2+@CNTs nanocomposite and its application as a solid-state electrochemiluminescence signal probeA simple label-free electrochemiluminescence (ECL) aptasensor was constructed for the detection of thrombin (TB) with the [Ru(phen)3]2+@CNTs/nafion film as a signal probe. We explored the possibility of using π-π stacking to synthesis [Ru(phen)3]2+-encapsulated CNTs nanocomposite ([Ru(phen)3]2+@CNTs), which was immobilized on a glassy carbon electrode (GCE) surface by an alternative matrix of composite film consisting of the [Ru(phen)3]2+@CNTs and nafion. Owing to their good electron transfer and biocompatibility, hollow gold nanospheres (HGNPs) were adsorbed onto the modified electrode to immobilize thrombin binding aptamer (TBA). When TB is bound by its TBA, the TB-TBA complex is electrical inertia, resulting in the decrease in ECL intensity. The proposed ECL aptasensor exhibited excellent performance for TB detection with linear range from 20 nmol L-1 to 1.0 pmol L-1 and a detection limit of 0.33 pmol L-1. Thus, this work provided a new method for immobilizing luminophore on an electrode surface and would extend the application of CNTs.3 A novel ECL biosensor for β-lactamase detection:using Ru (Ⅱ) linked-ampicillin complex as the recognition elementIn this work, [Ru(phen)2(cpaphen)]2+linked-ampicillin (Ru-Amp), as the novel specific recognition element, was proposed to construct a simple and sensitive electrogenerated chemiluminescence (ECL) biosensor for determination of β-lactamase. Here, Ru-Amp complex acted not only as a novel specific recognition element for β-lactamase but also as the ECL Luminescent reagent. Through electrostatic adsorption and the intermolecular π-π interactions, a large amount of Ru-Amp was immobilized to gold nanoparticles (TA@AuNPs) prepared by thiophenemalonic acid (TA) to obtain Ru-Amp/TA@AuNPs nanocomposites. The nanocomposites, which can produce very stable films exhibiting excellent ECL behaviors, were self-assembled on the CNTs-Nf modified glassy carbon electrode surface. The presence of the target β-lactamase resulted in autonomous hydrolysis reaction of Amp, achievement of the efficient ECL emission and highly sensitive detection of β-lactamase. The biosensor for β-lactamase detection was developed with excellent sensitivity of a concentration variation from 50 pg mL-1 to 100 ng mL"1 with a low detection limit of 37 pg mL-1. An ECL assay offers the proposed method opportunities for designing new Ru-based ECL luminophores for biosensing applications.4 In situ generation of self-enhanced luminophore by β-lactamase catalysis for highly sensitive Electrochemiluminescent aptasensorThis work described a new ECL aptasensor for ultrasensitive detection of thrombin (TB) based on the in situ generating self-enhanced luminophore by β-lactamase catalysis for signal amplification. Briefly, a ruthenium complex (Ru-Amp), including two regions of [Ru(phen)2(cpaphen)]2+ and ampicillin (Amp), was synthesized as a self-enhanced ECL luminophore, which can produce ECL signal through intramolecular interaction. Then, carbon nanotubes (CNTs) were used for immobilization of Ru-Amp via π-π stacking interaction to form the Ru-Amp@CNTs nanocomposite. Using poly(ethylenimine) (PEI) as linkage reagents, Au nanocages (AuNCs), owing to their electronic property and large surface areas, were decorated to the CNTs to form the Ru-Amp@CNTs-PEI-AuNCs nanocomposites, which were further used to immobilize thrombin binding aptamer Ⅱ (TBAⅡ) to form signal probe (Ru-Amp@CNTs-PEI-AuNCs-TBA Ⅱ). Through "sandwich" tactics, TBA Ⅱ bioconjugates, TB andTBA Iwere immobilized onto the gold nanoparticles modified electrode. Then, with the enzyme catalysis of β-lactamase, a novel self-enhanced ECL luminophore (Ru-AmpA) was in situ produced which could exhibit a significant enhancement of ECL signal, due to the structure transformation of an amide bond into a secondary amine. A sandwich ECL assay for TB detection was developed with excellent sensitivity of a concentration variation from 1.0 fmol L-1 to 1.0 pmol L-1 and a detection limit of 0.33 fmol L-1. Therefore, the self-enhanced ECL luminophore, combining the further enhancement by in situ enzymatic reaction, was expected to have potential applications in biotechnology and clinical diagnosis.5 The Ru complex and hollow gold nanoparticles branched-hydrogel as signal probe for construction of electrochemiluminescent aptasensorWe present a new method for ultrasensitive detection of thrombin (TB) based on Ru complex and hollow gold nanoparticles branched-hydrogel (pNAMM-Ru-HGNPs) as electrogenerated chemiluminescence (ECL) signal probe and dendritic gold nanoparticles reduced by poly(ethyleneimine) (PEI-DAuNPs) as enhancers for the signal amplification tactics. Here, a novel pNAMM-Ru-HGNPs composite were obtained via aqueous free-radical polymerization from two polymer monomers of [Ru(phen)2(cpaphen)]2+ linked N-(3-aminopropyl)methacrylamide and hollow gold nanoparticles functioned N-(3-aminopropyl)methacrylamide. The functionalized hydrogel composite, containing amount of Ru complex and hollow gold nanoparticles, were used as effective tag-carriers for the immobilization of thrombin binding aptamer Ⅱ (TBA Ⅱ) to form the pNAMM-Ru-HGNPs labeled TBA Ⅱ (pNAMM-Ru-HGNPs-TBA Ⅱ). For building the interface of the aptasensor, PEI@DAuNPs was modified on the carbon nanotube-nafion (CNTs-Nf) modified electrode through electrostatic adsorption, which not only was used as matrix for immobilization of thrombin binding aptamer Ⅰ (TBA Ⅰ) but also can enhance the ECL signal because PEI is an efficient co-reactant of Ru complex. Target TB was sandwiched between pNAMM-Ru-HGNPs-TBA Ⅱ and TBA Ⅰ, resulting in the ECL signals relevant to the TB concentrations. Combining the novel pNAMM-Ru-HGNPs containing amount of Ru complex as the ECL signal probe and PEI@DAuNPs as the enhancer for signal amplification, the sandwich ECL aptasensor was constructed for the detection of TB with a wide range of 1.0 fM to 10 pM and a low detection of 0.54 fM. |
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