A sensitive electrochemiluminescent aptasensor based on perylene derivatives as a novel co-reaction accelerator for signal amplification

Electrochemiluminescence biosensor for the thyroid cancer biomarker miRNA-146b-5p detection using Zr-based metal-organic framework

Cancer cell-derived exosomes serve as crucial biomarkers for thyroid cancer, which has emerged as the fourth most prevalent malignancy among urban Chinese women. However, achieving high sensitivity and precision in their in vitro detection remains challenging. Traditional diagnostic methods for thyroid cancer, including tumor-associated marker detection and imaging examinations, are limited by high costs and poor sensitivity. Among various biomarkers, miRNA-146b-5p has been identified as a key marker associated with the progression of thyroid cancer, which poses a formidable challenge in achieving exquisite sensitivity and precision in vitro detection. Herein, we developed an electrochemiluminescence (ECL) biosensor for the sensitive detection of the thyroid cancer marker miRNA-146b-5p, based on Zr-PTC and combining an ECL resonance energy transfer (ECL-RET) system with a toehold-mediated strand displacement reaction (TSDR) signal amplification strategy. Initially, Zr-PTC was employed as the ECL signal label, with miRNA-146b-5p as the model target to initiate the TSDR cycle, resulting in the release of the output chain (output). The output chain assisted the unfolding of hairpin DNA H1 (H1), which exposed its complementary sequence that hybridizes with the ECL quenching material (AgCl NPs-S1), thereby resulting in a significant reduction of the ECL signal. The combination of target cyclic amplification and metal-organic framework-based signal labeling significantly enhanced the sensitivity of the proposed biosensor, achieving limit of detection (LOD) for miRNA-146b-5p as low as 0.69 fM (S/N = 3). This innovative analytical methodology presents a promising strategy for detecting exosomal RNA biomarkers associated with thyroid malignancies. The integration of RET system with TSDR signal amplification not only enhanced detection sensitivity but also demonstrated robust reproducibility and stability, offering broad applicability for sensitive nucleic acid detection in human serum samples.

Aggregation-induced Electrochemiluminescence of AgNCs Enhanced with AuNPs@MXene Composites for Ultrasensitive Detection of microRNA

MXene, a two-dimensional nanomaterial, has metal conductivity, high electronegativity, functionalized with surface groups, which make it widely applicable in catalysis and biosensing. However, studies on the principle of enhanced electrochemiluminescence (ECL) by MXene composites and the improvement of their performance in catalyzing the ECL reaction are still in their infancy. In this study, gold nanoparticles (AuNPs) are obtained by mild reductive reduction and loaded in situ on the Ti3C2Tx MXene surface to form the composites (AuNPs@MXene). In oxygenated PBS test buffer, AuNPs@MXene enhance the ECL emission of silver nanoclusters (AgNCs) with aggregation-induced electrochemiluminescence (AIECL) properties as luminophore. Approximately 7.5-fold enhancement of ECL signals is obtained by using two ECL enhancement strategies: an efficient AIECL emitter and a co-reaction accelerator. The special nucleic acid structure with "Three Way Junction (TWJ)" enables an ultra-sensitive detection of microRNA, providing an efficient and ultra-sensitive method for microRNA detection. The biosensor achieves a wide detection range of microRNA-21 from 100 aM to 1 nM, with a low detection limit of 31 aM, and exhibits excellent stability, selectivity and high reproducibility in real samples.

Quenching study of Cu2S-MPA/NGODs composites in electrochemiluminescence detection by modulating resonance energy transfer and adsorption process

This study explores the principles of resonance energy transfer and adsorption modulation using composites of Cu2S-MPA/NGODs. These composites can efficiently control the quenching process of electrochemiluminescence (ECL). Mercaptopropionic acid (MPA) was added during the synthesis of Cu2S-MPA to enhance its attachment to nitrogen-doped graphene quantum dots (NGODs). The UV absorption peaks of NGODs coincided with the emission peaks of luminol ECL, enabling resonance energy transfer and enhancing the quenching capability of Cu2S-MPA. Meanwhile, there is another quenching strategy. When the readily reducible Cu+ ions underwent partial reduction to Cu when they were bound to NGODs. This weakened the electrocatalytic effect on reactive oxygen species (ROS) and had a detrimental impact on electron transfer. Under optimal conditions, the immunosensor ECL intensity decreased linearly with the logarithm of carcinoembryonic antigen (CEA) concentration in the range of 0.00001-40 ng/mL, with a detection limit of 0.269 fg/mL. The sensor was effectively utilized for the identification of CEA in actual serum samples.

Double-Amplified Electrochemiluminescence Immunoassay Sensor for Highly Sensitive Detection of CA19-9 Using a Ternary Semiconductor CdSSe

In this paper, an electrochemiluminescence (ECL) immunosensor for ultrasensitive detection of CA19-9 was constructed using ternary compound CdSSe nanoparticles as ECL emitter. The immunosensor employs Cu2S and gold-doped diindium trioxide (Au-In2O3) nanocubes as coreaction accelerators to achieve a double-amplification strategy. In general, a hexagonal maple leaf-shaped Cu2S with a large surface area was selected as the template, and the in situ growth of CdSSe on its surface was achieved using a hydrothermal method. The presence of Cu2S not only inhibited the aggregation of CdSSe nanoparticles to reduce their surface energy but also acted as an ECL cathode coreaction promoter, facilitating the generation of SO4•-. Consequently, the ECL intensity of CdSSe was significantly enhanced, and the reduction potential was significantly lower. In addition, the template method was employed to synthesize Au-In2O3 nanocubes, which offers the advantage of directly connecting materials with antibodies, resulting in a more stable construction of the immunosensor. Furthermore, In2O3 serves as a coreaction promoter, enabling the amplification strategy for ECL intensity of CdSSe, thus contributing to the enhanced sensitivity and performance of the immunosensor. The constructed immunosensor exhibited a wide linear range (100 μU mL-1 to 100 U mL-1) and a low detection limit of 80 μU mL-1, demonstrating its high potential and practical value for sensitive detection of CA19-9.

Electrochemiluminescence nanoemitters for immunoassay of protein biomarkers

The family of electrochemiluminescent luminophores has witnessed quick development since the electrochemiluminescence (ECL) phenomenon of silicon nanoparticles was first reported in 2002. Moreover, these developed ECL nanoemitters have extensively been applied in sensitive detection of protein biomarker by combining with immunological recognition. This review firstly summarized the origin and development of various ECL nanoemitters including inorganic and organic nanomaterials, with an emphasis on metal-organic frameworks (MOFs)-based ECL nanoemitters. Several effective strategies to amplify the ECL response of nanoemitters and improve the sensitivity of immunosensing were discussed. The application of ECL nanoemitters in immunoassay of protein biomarkers for diagnosis of cancers and other diseases, especially lung cancer and heart diseases, was comprehensively presented. The recent development of ECL imaging with the nanoemitters as ECL tags for detection of multiplex protein biomarkers on single cell membrane also attracted attention. Finally, the future opportunities and challenges in the ECL biosensing field were highlighted.

Synthesis characterization of Zn-based MOF and their application in degradation of water contaminants

Metal-organic frameworks (MOFs) are currently popular porous materials with research and application value in various fields such as medicine and engineering. Aiming at the application of MOFs in photocatalysis, this paper mainly reviews the main synthesis methods of ZnMOFs and the latest research progress of Zn MOF-based photocatalysts to degrade organic pollutants in water, such as organic dyes. This nanomaterial is being used to treat wastewater and has proven to be very efficient because of its exceptionally large surface area and porous nature. The results show that Zn-MOFs are capable of high degradation of the above pollutants and over 90% of degradation was observed in publications. In addition, the reusability percentage was examined and studies showed that the Zn-MOF nanostructure has very good stability and can continue to degrade a high percentage of pollutants after several cycles. This review focuses on Zn-MOFs and their composites. First, the methods of synthesis and characterization of these compounds are given. Finally, the application of these composites in the process of photocatalytic degradation of dye pollutants such as methylene blue, methyl orange, crystal violet, rhodamine B, etc. is explained.

Zinc-Based Metal-Organic Framework with MLCT Properties as an Efficient Electrochemiluminescence Probe for Trace Detection of Trenbolone

In this work, we utilized polycyclic aromatic hydrocarbon (PAH) derivatives as ligands to develop a zinc-based metal-organic framework (Zn-MOF) as an effective detection probe to construct an electrochemiluminescence (ECL) sensor for trenbolone detection. As traditional ECL emitters, PAHs and their derivatives have limited luminescence efficiency because of the aggregation-induced quenching (ACQ) effect. Therefore, Zn-PTC was designed by the coordination of 3,4,9,10-perylenetetracarboxylic (PTC) in the MOF to eliminate the ACQ effect. Meanwhile, Zn-PTC formed based on an aromatic ligand possessed the metal-to-ligand charge-transfer (MLCT) effect, which could transfer the energy of Zn²⁺ to the aromatic ligand for strong luminescence. The ECL efficiency of Zn-PTC was calculated to be approximately 2.2 times that of the ligand (K₄PTC). Second, the Ag@Fe core-shell bimetallic nanocrystal was prepared for efficient activation of persulfate (S₂O₈^2-), thereby generating more sulfate radicals (SO₄^•-) to further promote ECL emission. According to ECL characterizations, UV-vis and fluorescence spectra, and density functional theory calculations, the luminescence and signal amplification mechanisms were investigated. In addition, NKFRGKYKC (NKF) was introduced as an affinity ligand to directionally immobilize the target antibodies, thus releasing specific sites in their Fab fragment to enhance binding activity. Based on the above strategies, the constructed biosensor exhibited high sensitivity, realizing trace detection of TBE with a wide detection range (10 fg/mL-100 ng/mL) and a low detection limit (3.28 fg/mL). This study provided an important reference for sensitive monitoring of steroid pollutants in the environment.

Electrochemiluminescence Systems for the Detection of Biomarkers: Strategical and Technological Advances

Electrochemiluminescence (ECL)-based sensing systems rely on light emissions from luminophores, which are generated by high-energy electron transfer reactions between electrogenerated species on an electrode. ECL systems have been widely used in the detection and monitoring of diverse, disease-related biomarkers due to their high selectivity and fast response times, as well as their spatial and temporal control of luminance, high controllability, and a wide detection range. This review focuses on the recent strategic and technological advances in ECL-based biomarker detection systems. We introduce several sensing systems for medical applications that are classified according to the reactions that drive ECL signal emissions. We also provide recent examples of sensing strategies and technologies based on factors that enhance sensitivity and multiplexing abilities as well as simplify sensing procedures. This review also discusses the potential strategies and technologies for the development of ECL systems with an enhanced detection ability.

Regulation of the Structure of Zirconium-Based Porphyrinic Metal-Organic Framework as Highly Electrochemiluminescence Sensing Platform for Thrombin

An electrochemiluminescence (ECL) sensor provides a sensitive and convenient method for early diagnosis of diseases; however, it is still a challenge to develop simple and sensitive sensing platforms based on efficient ECL signals and luminophore groups. Porphyrin-based metal-organic frameworks (MOFs) show great potential in ECL sensing; however, the mechanism and structure-activity relationship, as well as application, are rarely reported. Herein, hydrothermal reactions obtained porphyrin Zr-MOFs (PCN-222) with different specific surface areas, pore sizes, structures, and surface charge states by tuning the reaction time were developed, which served both as the ECL luminophore, coreaction promoter for S₂O₈^2-, and a connection in the ECL immunoassay. By progressively controlling the condition of the hydrothermal reaction, PCN-222 with large surface area-abundant micropores can be obtained, which has good conductivity and positively charged surfaces, obtaining excellent ECL performance. The ECL performance and the enhancement mechanism were investigated in detail. Using PCN-222-6h with the best ECL intensity as the immobilization matrix for the aptamer, a highly sensitive and selective assay for thrombin was developed. The decrease of the ECL signal was logarithmically linear with the concentration of thrombin in the range from 50 fg mL^-1 to 100 pg mL^-1 with a low detection limit of 2.48 fg/mL. This proposed strategy provides a brand new approach for tuning of the structures of MOFs as effective ECL signal probes, thus providing wider possibilities for effective ECL immunoassays in the detection of other biomarkers in diagnosis of diseases.

Novel Ratiometric Electrochemiluminescence Biosensor Based on BP-CdTe QDs with Dual Emission for Detecting MicroRNA-126

The electrochemiluminescence (ECL) ratiometric assay is usually based on two different ECL luminophores, and the choice of two suitable luminophores and shared co-reactant makes its construction challenging. The single-emitter-based ECL ratio mode could overcome the limitation of two luminophores and simplify the construction process, so it is an ideal choice. In this work, CdTe quantum dots (CdTe QDs) were modulated using black phosphorus (BP) nanosheet to simultaneously emit the cathodic and anodic ECL signals, and H₂O₂ and tripropylamine (TPrA) served as the cathodic and anodic co-reactants, respectively. MicroRNA-126 (miRNA-126) was selected as the template target to exploit the application of BP-CdTe QDs in the single-emitter-based ECL ratio detection. Through the target recycling triggering rolling-circle amplification (RCA) reaction, a large amount of glucose oxidase (GOx)-modified single strand 1 was introduced. GOx catalyzed glucose to produce H₂O₂ in situ, which acted as a dual-role moderator to quench the anodic ECL emission with TPrA as the co-reactant while enhancing the cathodic emission, thereby realizing the ratiometric detection of miRNA-126 with a low detection limit of 29 aM (S/N = 3). The dual-ECL-emitting BP-CdTe QDs with TPrA-H₂O₂ as dual co-reactant provide a superior ECL ratio platform involving enzyme catalytic reaction, expanding the application of single-emitter-based ratio sensing in the diverse biological analysis.

Advances in electrochemiluminescence co-reaction accelerator and its analytical applications

Electrochemiluminescence (ECL) can be produced through two main routes: annihilation route and coreactant route. The vast majority of applications of ECL are based on coreactant ECL which can be generated in aqueous media at relatively low potentials compared with organic solvents. However, the development of more efficient ECL systems remains a compelling goal. Co-reaction accelerator (CRA) can significantly enhance the ECL signal through promoting more production of the coreactant intermediate. Compared with other ECL enhancement strategies, the CRA protocol is distinctive owing to its diverse, simple, and highly effective features. Various species such as inorganic compound, organic compound, and nanomaterials (NMs) have been developed as CRA and NM CRA has gained particular attention owing to their unique properties of excellent catalytic behavior and large surface area. By integration with the inherent advantages of ECL, bioanalysis based on CRA-enhanced ECL showed excellent performance such as ultrahigh sensitivity, wide dynamic range, low cost, simple instrumentation, and measurements in complex media. It has been extensively applied in various fields including clinical diagnosis, environmental monitoring, and food safety. Therefore, it is of great interest to present a systematic and critical review on the advances in ECL CRA. Herein, the recent progress on CRA and its applications in ECL bioanalysis are summarized by illustrating some representative work and a discussion of the future development trends of CRA ECL is offered.

Postsynthesis Ligand Exchange Induced Porphyrin Hybrid Crystalloid Reconstruction for Self-Enhanced Electrochemiluminescence

In traditional coreactant electrochemiluminescence (ECL), the efficiency of the coreactant catalyzed into an active intermediate is one of the dominant factors restricting the luminous intensity. In this work, Co-2-MI-ZnTCPP is designed as a composite material integrating coreaction accelerator (Co-N) and luminophore. Through the catalytic effect of Co-N structures on hydrogen peroxide, the in situ generation and accumulation of active intermediates are achieved, which will react with porphyrin anion radical, thereby bringing out self-enhanced ECL. By adjusting the scanning potential range, the ECL mechanism is thoroughly studied and the contribution of each potential window to the luminescence is obtained. This work provides inspiration for the design of integrated ECL emitters with a coreaction accelerator and luminophore, providing a new way for the construction of a self-enhanced ECL emitter.

A feasibility study of a leaky waveguide aptasensor for thrombin

This proof-of-principle study demonstrates the feasibility of a leaky waveguide (LW) aptasensor, where aptamers were immobilised in a mesoporous chitosan waveguiding film for the detection of thrombin. This work has demonstrated that aptamers immobilised in hydrogels retain their affinity and selectivity towards their target and thus can be used as bioreceptors. The use of antibodies as bioreceptors for sensing thrombin is not viable because it is a serine protease, which will cleave the antibodies. Currently used assays based on clotting time and chromogenic/fluorogenic substrates have limited potential for thrombin measurement in whole blood. Using the initial binding rate over the first 5 min, the limit of detection of our LW aptasensor for thrombin was ∼22 nM. The sensor was tested with spiked serum samples, giving a reading of 46.1 ± 4.6 nM for a sample containing 50 nM thrombin. Our proposed sensor combines the robustness and low cost of aptamers as molecular recognition elements with the simple fabrication process of the chitosan-based leaky waveguide, making LW aptasensors highly attractive for applications in point-of-care diagnostics and healthcare monitoring.

Recent advances in co-reaction accelerators for sensitive electrochemiluminescence analysis

In electrochemiluminescence sensing platforms, co-reaction accelerators are specific materials used to catalyze the dissociation of co-reactants into active radicals, which can significantly boost the ECL emission of luminophores.

Electrochemiluminescence Double Quenching System Based on Novel Emitter GdPO4:Eu with Low-Excited Positive Potential for Ultrasensitive Procalcitonin Detection

Nowadays, the electrochemiluminescence (ECL) immunosensor with the unique superiority of tunable luminescence and ultrahigh sensitivity has become one of the most promising immunoassay techniques, especially for low-abundance biomarkers analysis. However, the use of signal probes with high excited potential and applied emitters which owned good intensity but biotoxicity limited its application. Herein, an ECL resonance energy transfer strategy was developed based on protein bioactivity protection utilizing europium-doped phosphoric acid gadolinium (GdPO₄:Eu) as novel low-potential luminophor (donor) and Pd@Cu₂O as the quenching probe (acceptor). Specifically, GdPO₄:Eu was first prepared by using the hydrothermal synthesis method to apply in ECL, and when it coexisted with K₂S₂O₈, cathode, a strong ECL signal would be generated at a low potential of -1.15 V (vs Ag/AgCl), where the immunocompetence of antigens and antibodies can be maintained well. Electrical pair Eu³⁺/Eu²⁺, as the coreactant promoter, produced by potential excitation could produce more SO₄^•- to accelerate the oxidation process of GdPO₄:Eu. Meanwhile, Cu₂O coated onto Pd (Pd@Cu₂O), as a dual-quencher, enhanced the quenching effect of Pd alone and controlled the ECL intensity of the "signal on" state within a reasonable range. As a result, the proposed biosensor for detection of trace procalcitonin, a biomarker of systemic inflammatory response syndrome, exhibited a far low detection limit, 0.402 fg/mL (S/N = 3). Importantly, this work not only utilized a promising ECL emitter for biosensing platform construction but also had momentous potential in biomarker detection of disease diagnosis and clinical analysis.

Ultrasensitive aptasensing of insulin based on hollow porous C3N4/S2O82-/AuPtAg ECL ternary system and DNA walker amplification

In this work, a high-efficiency electrochemiluminescence (ECL) ternary system was constructed for ultrasensitive assay of insulin based on hollow porous graphitic carbon nitride (HP-C₃N₄) as novel luminophore, S₂O₈^2- as coreactant and tri-metallic AuPtAg as coreaction accelerator. Specifically, in comparison with C₃N₄-based bulk nanomaterials, the as-prepared HP-C₃N₄ exhibits high luminous efficiency though decreased inner filter effect and minimized inactive ECL emitter. Noteworthy, tri-metallic AuPtAg, possessing the superiority of Au, Pt and Ag, was first used as coreaction accelerator to significantly enhance ECL intensity of HP-C₃N₄ and S₂O₈^2-. As a consequence, with the resultant ECL ternary (HP-C₃N₄/S₂O₈^2-/AuPtAg) system as aptasensing platform, a high-intense initial ECL signal was achieved. Subsequently, ferrocene-labeled quenching probe (Fc-HP2) as ECL quencher was used to quench the initial signal and achieve the low-background noise. Eventually, in the presence of insulin, the target-induced triple-helix molecular switch and Nb.BbvCI-assisted DNA walker amplification were executed to recover a strong ECL signal by releasing Fc-HP2 from the electrode surface. As expected, the constructed aptasensor presents an excellent sensitivity and selectivity for detecting insulin range from 0.05 pg mL^-1 to 100 ng mL^-1 with a detection limit of 17 fg mL^-1. This work provides a new avenue for developing highly efficient HP-C₃N₄ based ECL ternary system as well as ultrasensitive ECL aptasensors for bioanalysis.

Highly-branched Cu2O as well-ordered co-reaction accelerator for amplifying electrochemiluminescence response of gold nanoclusters and procalcitonin analysis based on protein bioactivity maintenance

The point of fabricating ultrasensitive electrochemiluminescence (ECL)-based biosensors should be focused on how to maintain high immune recognition of antigens by antibodies in whole process. That is not effortless due to the structure of the protein can be destroyed root in toxic nanocarriers, excessive cyclic potential and superoxide radicals in coreactant, all of which can lead to reduce the bioactivity of antigen and antibody. In this work, the effect of negative voltage and divers coreactant on protein bioactivity were verified. Based on that, a motivated ECL biosensor with good biocompatibility was fabricated for procalcitonin (PCT) detection using Au nanoclusters (Au NCs) as low-potential cathodic luminophor and K₂S₂O₈ as non-toxic coreactant, respectively. Besides, highly-branched Cu₂O was utilized to catalyze K₂S₂O₈ and produce more radical anion SO₄^•-, which can oxidize Au NCs^•- to generate more high-energy-state Au NCs*, thus doubling the ECL intensity to meet the requirements of trace analysis. In addition, protein A (PA) as specific antibody capturer was employed to bind the Fc region of anti-PCT in an orientated way, further maintaining the physiological activity of antibody. As expected, all strategies undoubtedly practically improved the immune recognition of the biosensor and reduced the detection limit to 2.90 fg/mL.

Bioactivity-Protected Electrochemiluminescence Biosensor Using Gold Nanoclusters as the Low-Potential Luminophor and Cu2S Snowflake as Co-reaction Accelerator for Procalcitonin Analysis

The expansion of electrochemiluminescence (ECL) technology to immunoassay at the core of care emphasizes all immune molecules will not be inactivated in the analysis process. That poses a major challenge to ECL-based biosensors due to the deoxynucleotide sequences of an antigen or antibody could be oxidized through a route of excessive cyclic potential. Herein, an ultrasensitive ECL biosensor was developed based on a novel bioactivity-protected sensing strategy utilizing Au nanoclusters (Au NCs) as low-potential luminophor for detection of procalcitonin (PCT). Bovine serum albumin (BSA)-templated Au NCs exhibited a low-potential anodic ECL signal in triethylamine (TEA) solution at 0.87 V, where it is suitable for the survival of immune molecules. Taking advantage of good conductivity and high surface area, a Cu₂S snowflake not only functions as a satisfying substrate for connecting immune molecules but also acts as co-reaction accelerator to produce more cationic radicals TEA^•+, which could improve the ECL intensity needed to meet the requirements of trace analysis. Otherwise, HWRGWVC (HC-7) heptapeptide as specific antibody immobilizer for site-oriented fixation was introduced to further maintain the bioactivity of an antibody. In view of the preceding discussion, the obtained biosensor exhibited ultrahigh immune recognition to targets so that the detection limit was as low as an unprecedented value of 2.36 fg/mL, which will be of great significance to the application and development of a biosensor in the future.

Electrochemiluminescence of 3,4,9,10-perylenetetracarboxylic acid/oxamic hydrazide and its application in the detection of tannic acid

The electrochemiluminescence of 3,4,9,10-perylenetetracarboxylic acid/oxamic hydrazide is reported and used for tannic acid detection for the first time.

A graphene oxide nanosensor enables the co-delivery of aptamer and peptide probes for fluorescence imaging of a cascade reaction in apoptotic signaling

Cytochrome c (Cyt c) and caspase-3 are the key mediators in apoptotic signaling. As is known to all, the release of Cyt c from mitochondria is a vital caspase activation pathway and defines the point of no-return in cell apoptosis. However, it has not been reported that any fluorescence imaging tools could allow simultaneous visualization of Cyt c translocation and caspase-3 activation in apoptotic cells. Here, we develop a sensitive nanosensor that holds the capability of imaging of the released Cyt c from the mitochondria and a caspase-3 activation cascade reaction in apoptotic signaling. The nanosensor is constructed by the assembly of a fluorophore (Cy5)-tagged DNA aptamer on graphene nanosheets that have been covalently immobilized with a FAM-labeled peptide. After a spatially selective delivery into the cytoplasm, the Cy5-tagged DNA aptamer assembled on the nanosensor can bind with Cyt c released from the mitochondria to the cytoplasm and dissociate from graphene, triggering a red fluorescence signal. In addition, the caspase-3 activated by the Cyt c released to the cytoplasm can cleave the FAM-labeled peptide and result in a green fluorescence output. The nanosensor exhibits rapid response, high sensitivity and selectivity for in vitro assays, and high contrast imaging of Cyt c and caspase-3 in living cells. It also provides the method for the study of the kinetic relationship between the Cyt c translocation and caspase-3 activation through simultaneous imaging of Cyt c and caspase-3. The developed nanosensor described here will be an efficient and potential platform for apoptosis research.

Exciton-Plasmon Interaction between AuNPs/Graphene Nanohybrids and CdS Quantum Dots/TiO2 for Photoelectrochemical Aptasensing of Prostate-Specific Antigen

A competitive-displacement reaction strategy based on target-induced dissociation of gold nanoparticle coated graphene nanosheet (AuNPs/GN) from CdS quantum dot functionalized mesoporous titanium dioxide (CdS QDs/TiO₂) was designed for the sensitive photoelectrochemical (PEC) aptasensing of prostate-specific antigen (PSA) through the exciton-plasmon interaction (EPI) between CdS QDs and AuNPs. To construct such an aptasensing system, capture DNA was initially conjugated covalently onto CdS QDs/TiO₂-modified electrode, and then AuNPs/GN-labeled PSA aptamer was bound onto biofunctionalized CdS QDs/TiO₂ via hybridization chain reaction of partial bases with capture DNA. Introduction of AuNPs/GN efficiently quenched the photocurrent of CdS QDs/TiO₂ thanks to energy transfer. Upon addition of target PSA, the sandwiched aptamer between CdS QDs/TiO₂ and AuNPs/GN reacted with the analyte analyte, thus resulting in the dissociation of AuNPs/GN from the CdS QDs/TiO₂ to increase the photocurrent. Under optimum conditions, the aptasensing platform exhibited a high sensitivity for PSA detection within a dynamic linear range of 1.0 pg/mL to 8.0 ng/mL at a low limitat of detection of 0.52 pg/mL. The interparticle distance of exciton-plasmon interaction and contents of AuNPs corresponding to EPI effect in this system were also studied. Good selectivity and high reproducibility were obtained for the analysis of target PSA. Importantly, the accuracy and matrix effect of PEC aptasensor was evaluated for the determination of human serum specimens and newborn calf serum-diluted PSA standards, giving a well-matched result with the referenced PSA ELISA kit.

Graphitic-phase carbon nitride-based electrochemiluminescence sensing analyses: recent advances and perspectives

This review describes the current trends in synthesis methods, signaling strategies, and sensing applications of g-C₃N₄-based ECL emitters.

Electrochemiluminescence biosensing based on different modes of switching signals

Electrochemiluminescence (ECL) has attracted much attention in various fields of analysis owing to low background signals, high sensitivity, and excellent controllability.

Manganese porphyrin decorated on DNA networks as quencher and mimicking enzyme for construction of ultrasensitive photoelectrochemistry aptasensor

In this work, the manganese porphyrin (MnPP) decorated on DNA networks could serve as quencher and mimicking enzyme to efficiently reduce the photocurrent of photoactive material 3,4,9,10-perylene tetracarboxylic acid (PTCA), which was elaborately used to construct a novel label-free aptasensor for ultrasensitive detection of thrombin (TB) in a signal-off manner. The Au-doped PTCA (PTCA-PEI-Au) with outstanding membrane-forming and photoelectric property was modified on electrode to acquire a strong initial photoelectrochemistry (PEC) signal. Afterward, target binding aptamer Ι (TBAΙ) was modified on electrode to specially recognize target TB, which could further combine with TBAII and single-stranded DNA P1-modified platinum nanoparticles (TBAII-PtNPs-P1) for immobilizing DNA networks with abundant MnPP. Ingeniously, the MnPP could not only directly quench the photocurrent of PTCA, but also acted as hydrogen peroxide (HRP) mimicking enzyme to remarkably stimulate the deposition of benzo-4-chlorhexidine (4-CD) on electrode for further decreasing the photocurrent of PTCA, thereby obtaining a definitely low photocurrent for detection of TB. As a result, the proposed PEC aptasensor illustrated excellent sensitivity with a low detection limit down to 3 fM, exploiting a new avenue about intergrating two functions in one substance for ultrasensitive biological monitoring.

Intramolecular Self-Enhanced Nanochains Functionalized by an Electrochemiluminescence Reagent and Its Immunosensing Application for the Detection of Urinary β2-Microglobulin

In this study, polyethylenimine (PEI) is discovered to possess a noticeable amplification effect for the electrochemiluminescence (ECL) of N-(aminobutyl)-N-(ethylisoluminol) (ABEI); thus, a novel self-enhanced ECL reagent (ABEI-PEI) is prepared by covalent cross-linking. Because of the shortened electron-transfer path and reduced energy loss, the intramolecular ECL reaction between ABEI and PEI exhibited enhanced luminous efficiency compared with the traditional intermolecular ECL reaction. Owing to the amine-rich property of PEI, abundant ABEI could be immobilized on the molecular chains of PEI to strengthen the luminous intensity of ABEI-PEI. On account of the reducibility of remaining amino groups, ABEI-PEI, as the self-enhanced ECL reagent, has also been chosen as a reductant and stabilizer for in situ preparation of Au@Ag nanochains (Au@AgNCs) which has the catalytic activity for the ECL reaction. Moreover, using ABEI-PEI as a template to directly prepare Au@AgNCs realizes the immobilization of the ECL reagent with large amounts. Meanwhile, in virtue of the electropositivity of ABEI-PEI-capped Au@AgNCs (ABEI-PEI-Au@AgNCs), polyacrylic acid (PAA) with electronegativity is pervaded on the surface of nanochains and further chelates with Co²⁺ to form an ABEI-PEI-Au@AgNCs-PAA/Co²⁺ complex, which could introduce Co²⁺ as a catalyst to promote H₂O₂ decomposition and thus oxidize ABEI to produce an enhanced ECL signal. Here, the obtained self-enhanced ABEI-PEI-Au@AgNCs-PAA/Co²⁺ complex is utilized to capture the detection antibody (Ab₂). According to sandwiched immunoreactions, a sensitive ECL immunosensor is constructed for the detection of β2-microglobulin with a wide linearity from 0.01 pg mL^-1 to 200 ng mL^-1 and a detection limit of 3.3 fg mL^-1.

Bay- and Ortho-Octasubstituted Perylenes

A key intermediate compound, 2,5,8,11-tetrabromo-1,6,7,12-tetrabutoxyperylene (Per-4Br), was synthesized from 3,6-dibromo-2,7-dioxylnaphthalene via simple regioselective oxidative radical-radical coupling, followed by reduction and nucleophilic substitution. Various bay- and ortho-octasubstituted perylenes containing cyano, methoxy and aryl groups were then obtained by nucleophilic substitution or Pd-catalyzed coupling reactions. X-ray crystallographic analyses reveal that these new perylene molecules process a twisted structure due to steric congestion at the bay-regions and there is no obvious intermolecular π-π interaction. As a result, they exhibit moderate fluorescence quantum yields even in solid state. Therefore, Per-4Br can serve as a versatile building block for various functional perylene dyes with tunable optoelectronic property.