Molecular Planar Rigidity Promoted Aggregation-Induced Delayed Electrochemiluminescence of Organic Dots for Nucleic Acid Assay.

Developing organic aggregation-induced delayed electrochemiluminescence (AIDECL) active emitters is attractive due to their full utilization of excited species. However, current molecular designs primarily focus on the electron-deficient core benzophenone, resulting in relatively low ECL efficiency due to its flexible skeleton. Herein, we design a rigid electron acceptor, i.e., xanthenone, by inserting an oxygen bridge into the benzophenone moiety, and an AIDECL-active organic dot (OD) composed of a xanthenone-dimethylacridine compound is constructed. High ECL efficiency is achieved for the resultant ODs, with a 3-fold enhancement compared to control ODs. Oxygen bridge-induced planar moiety rigidifies the molecular configuration, further inhibiting intramolecular motions and thus suppressing nonradiative decay, supported by the single-crystal data together with theoretical calculations. Significantly, an ECL biosensor is constructed employing these ODs as emitters for the sensitive analysis of miR-21 associated with pancreatic cancer, which demonstrates a low detection limit of 2.8 fM. Our investigation provides a promising way to design efficient ECL emitters and deepens the understanding of structure-property relationships.

Logic Signal Amplification System for Sensitive Electrochemiluminescence Detection and Subtype Identification of Cancer Cells.

Achieving sensitive detection and accurate identification of cancer cells is vital for diagnosing and treating the disease. Here, we developed a logic signal amplification system using DNA tetrahedron-mediated three-dimensional (3D) DNA nanonetworks for sensitive electrochemiluminescence (ECL) detection and subtype identification of cancer cells. Specially designed hairpins were integrated into DNA tetrahedral nanostructures (DTNs) to perform a catalytic hairpin assembly (CHA) reaction in the presence of target microRNA, forming hyperbranched 3D nanonetworks. Benefiting from the "spatial confinement effect," the DNA tetrahedron-mediated catalytic hairpin assembly (DTCHA) reaction displayed significantly faster kinetics and greater cycle conversion efficiency than traditional CHA. The resulting 3D nanonetworks could load a large amount of Ru(phen)32+, significantly enhancing its ECL signal, and exhibit detection limits for both miR-21 and miR-141 at the femtomolar level. The biosensor based on modular logic gates facilitated the distinction and quantification of cancer cells and normal cells based on miR-21 levels, combined with miR-141 levels, to further identify different subtypes of breast cancer cells. Overall, this study provides potential applications in miRNA-related clinical diagnostics.

Enhanced Aggregation-Induced Delayed Electrochemiluminescence Triggered by Spatial Perturbation of Organic Dots.

Development of highly efficient, heavy-metal-free electrochemiluminescence (ECL) materials is attractive but still challenging. Herein, we report an aggregation-induced delayed ECL (AIDECL) active organic dot (OD) composed of a tert-butoxy-group-substituted benzophenone-dimethylacridine compound, which shows high ECL efficiency. The resultant ODs exhibit 2.1-fold higher ECL efficiency compared to control AIDECL-active ODs. Molecular stacking combined with theoretical calculations suggests that tert-butoxy groups effectively participate in the intermolecular interactions, further inhibiting the molecular motions in the aggregated states and thus accelerating radiative decay. On the basis of these ODs exhibiting excellent ECL performance, a proof-of-concept biosensor is constructed for the detection of miR-16 associated with Alzheimer's disease, which demonstrates excellent detection ability with the limit of detection of 1.7 fM. This work provides a new approach to improve the ECL efficiency and enriches the fundamental understanding of the structure-property relationship.

Interfacial Hydrogen-Bond Interactions Driven Assembly toward Polychromatic Copper Nanoclusters.

Constructing versatile metal nanoclusters (NCs) assemblies through noncovalent weak interactions between inter-ligands is a long-standing challenge in interfacial chemistry, while compelling interfacial hydrogen-bond-driven metal NCs assemblies remain unexplored so far. Here, the study reports an amination-ligand o-phenylenediamine-coordinated copper NCs (CuNCs), demonstrating the impact of interfacial hydrogen-bonds (IHBs) motifs on the luminescent behaviors of metal NCs as the alteration of protic solvent. Experimental results supported by theoretical calculation unveil that the flexibility of interfacial ligand and the distance of cuprophilic CuI···CuI interaction between intra-/inter-NCs can be tailored by manipulating the cooperation between the diverse IHBs motifs reconstruction, therewith the IHBs-modulated fundamental structure-property relationships are established. Importantly, by utilizing the IHBs-mediated optical polychromatism of aminated CuNCs, portable visualization of humidity sensing test-strips with fast response is successfully manufactured. This work not only provides further insights into exploring the interfacial chemistry of NCs based on inter-ligands hydrogen-bond interactions, but also offers a new opportunity to expand the practical application for optical sensing of metal NCs.

Ultrasensitive Nucleic Acid Assay Based on AIE-Active Polymer Dots with Excellent Electrochemiluminescence Stability.

Aggregation-induced emission (AIE) active Pdots are attractive nanomaterials applied in electrochemiluminescence (ECL) fields, while the irreversible redox reaction of these Pdots is a prevailing problem, resulting in instability of ECL emission. Herein, we first designed and synthesized an AIE-active Pdot with reversible redox property, which contains a tetraphenylethene derivate and benzothiadiazole (BT) to achieve stable ECL emission. BT has a good rigid structure with excellent electrochemical behaviors, which is beneficial for avoiding the destruction of the conjugated structure as much as possible during the preparation of Pdots, thus maintaining good redox property. The tetraphenylethene derivate, as a typical AIE-active moiety, provides a channel for highly efficient luminescence in the aggregated states. The Pdots exhibited reversible and quasi-reversible electrochemical behaviors during cathodic and anodic scanning, respectively. The stable annihilation, reductive-oxidative, and oxidative-reductive ECL signals were observed. Subsequently, we constructed an ultrasensitive ECL biosensor based on the oxidative-reductive ECL mode for the detection of miRNA-21 with a detection limit of 32 aM. This work provides some inspiration for the future design of ECL materials featuring AIE-active property and stable ECL emission.

Dual Recognition DNA Triangular Prism Nanoprobe: Toward the Relationship between K+ and pH in Lysosomes.

Lysosomal acidification is essential for its degradative function, and the flux of H+ correlated with that of K+ in lysosomes. However, there is little research on their correlation due to the lack of probes that can simultaneously image these two ions. To deeply understand the role of K+ in lysosomal acidification, here, we designed and fabricated a nanodevice using a K+-aptamer and two pH-triggered nanoswitches incorporated into a DNA triangular prism (DTP) as a dual signal response platform to simultaneously visualize K+ and pH in lysosomes by a fluorescence method. This strategy could conveniently integrate two signal recognition modules into one probe, so as to achieve the goal of sensitive detection of two kinds of signals in the same time and space, which is suitable for the detection of various signals with the correlation of concentration. By co-imaging both K+ and H+ in lysosomes, we found that the efflux of K+ was accompanied by a decrease of pH, which is of great value in understanding lysosomal acidification. Moreover, this strategy also has broad prospects as a versatile optical sensing platform for multiplexed analysis of other biomolecules in living cells.

Simulation-Assisted DNA Nanodevice Serve as a General Optical Platform for Multiplexed Analysis of Micrornas.

Small frame nucleic acids (FNAs) serve as excellent carrier materials for various functional nucleic acid molecules, showcasing extensive potential applications in biomedicine development. The carrier module and function module combination is crucial for probe design, where an improper combination can significantly impede the functionality of sensing platforms. This study explores the effect of various combinations on the sensing performance of nanodevices through simulations and experimental approaches. Variances in response velocities, sensitivities, and cell uptake efficiencies across different structures are observed. Factors such as the number of functional molecules loaded, loading positions, and intermodular distances affect the rigidity and stability of the nanostructure. The findings reveal that the structures with full loads and moderate distances between modules have the lowest potential energy. Based on these insights, a multisignal detection platform that offers optimal sensitivity and response speed is developed. This research offers valuable insights for designing FNAs-based probes and presents a streamlined method for the conceptualization and optimization of DNA nanodevices.

Boron-enriched rice-like homologous carbon nanoclusters with a 51.5% photoluminescent quantum yield for highly sensitive determination of endogenous hydroxyl radicals in living cells.

Exploring the ultrahigh quantum efficiency of a carbon-based probe via a green and simple technique, and utilisation of its sensing ability for highly bioactive molecule detection is still highly challenging. Herein, we prepared a novel boron-enriched rice-like homologous carbon nanoclusters (BRCNs) with an ultrahigh quantum efficiency of ∼51.5% by introduction of a conjugated structure attached to the CN bond and an electron-withdrawing boron active centre. Unexpectedly, the BRCNs obtained showed a stable dispersion of rice-like carbon nanograins, composed of small carbon dot assembled nanoclusters with an average diameter size of ∼30 nm, and containing boron units of ∼24.68 at%. What's exciting is that the BRCNs obtained exhibited an "on-off-on" three-state emission with the addition of an hydroxyl radical (OH˙) and its antioxidants. Thus, two distinctive fluorescent responses for OH˙ and antioxidants based on the BRCN probe had been developed, and the mechanism has been determined using TEM, XPS, FT-IR, FL, UV-vis spectrophotometry, UPS and fluorescent lifetimes. The OH˙, generated from the Fenton's reagent, preferentially attack the electron-deficient vacancy p orbit of the boron atom in the surface of the BRCNs, which results in the boron atom being easily substituted/attacked by OH˙, and leading to spontaneous aggregation induced quenching (AIQ) due to the existence of a strong intermolecular hydrogen bond between denatured BRCNs. Furthermore, the proposed method was also successfully applied to monitor endogenous OH˙ generation in HeLa cells by confocal imaging, which could be used for elucidating OH˙-induced oxidative damage to biological tissues and proteins.

Visual analysis of Alzheimer disease biomarker via low-potential driven bipolar electrode.

Developing a simple, economical, and accurate diagnostic method has positive practical significance for the early prevention and intervention of Alzheimer's disease (AD). Herein, combining a closed bipolar electrode (BPE) chip with multicolor electrochemiluminescence (ECL) imaging technology, we constructed a low-voltage driven portable visualized ECL device for the early screening of AD. By introducing parallel resistance, the total resistance of the circuit was greatly reduced. A classical mixture of Ir(ppy)3 and Ru(bpy)32+ was used as multicolor emitters of the anode with TPrA as the co-reactant. Capture of amyloid-ß (Aß) through antigen-antibody recognition, and signal amplification by electroactive covalent organic frameworks (COF) probe at the cathode of BPE caused the significantly increased faradaic current. The electrical balance of the BPE system resulted in the change of the emission color from green to red at the anode. The ECL-BPE sensor shows good reproducibility and high sensitivity with detection limit of 1 pM by naked eye. The driving voltage is 3.0 V, which means the chip could be driven by two fifth batteries. The visualized ECL-BPE sensor provides a promising point-of-care testing (POCT) tool for the screening of Alzheimer's-related diseases in the early stage.

Intracellular activated logic nanomachines based on framework nucleic acids for low background detection of microRNAs in living cells.

DNA molecular machines based on DNA logic circuits show unparalleled potential in precision medicine. However, delivering DNA nanomachines into real biological systems and ensuring that they perform functions specifically, quickly and logically remain a challenge. Here, we developed an efficient DNA molecular machine integrating transfer-sensor-computation-output functions to achieve high fidelity detection of intracellular biomolecules. The introduction of pH nanoswitches enabled the nanomachines to be activated after entering the cell, and the spatial-confinement effect of the DNA triangular prism (TP) enables the molecular machine to process complex information at the nanoscale, with higher sensitivity and shorter response time than diffuse-dominated logic circuits. Such cascaded activation molecular machines follow the logic of AND to achieve specific capture and detection of biomolecules in living cells through a multi-hierarchical response, providing a new insight into the construction of efficient DNA molecular machines.

Near-infrared photothermally activated DNA nanotweezers for imaging ATP in living cells.

By assembling nanotweezers with ATP-splitting aptamers on gold nanorods (AuT123L), we constructed a near-infrared-activated ATP sensing device that could time-controllably image ATP levels in living cells. By replacing the aptamers on the nanotweezers, the nanoplatform can be applied to other important biomolecules, opening up more possibilities for the study of time controllable nanodevices.

Ultrasensitive electrochemical detection of neuron-specific enolase based on spiny core-shell Au/CuxO@CeO2 nanocubes.

As a specific biomarker, neuron-specific enolase (NSE) is an essential clinical indicator for diagnosing small cell lung cancer. In this paper, a sandwich-type electrochemical immunosensor was designed for the quantitative detection of NSE. AuPt nanoblock spherical nanoarchitectonics (AuPt NSNs), a bimetallic nanoparticle with a rugged morphology, were utilized as the substrate, which could enhance the electronic conduction and increase the immobilization capacity of the primary antibody (Ab1). Moreover, through a simple hydrothermal method, Au/CuxO@CeO2 was prepared as a spiny core-shell nanocube with cerium dioxide (CeO2) and gold nanoparticles (Au NPs) loading. The combination of Cu2O, CuO, and CeO2 showed favorable catalytic activity toward hydrogen peroxide (H2O2). Furthermore, the deposition of Au NPs on the spiny surface structure enhanced the specific surface area and biocompatibility, thereby rendering it more effective for loading the second antibody (Ab2). As the label material, the Au/CuxO@CeO2 achieved signal amplification and sensitive detection with the immunosensor. Under optimal conditions, the designed immunosensor possessed a broad linear range of 50 fg mL-1 to 100 ng mL-1 and a limit of detection of 31.3 fg mL-1, along with satisfactory performance in sensitivity, selectivity, and stability.

Mulberry-like Au@PtPd porous nanorods composites as signal amplifiers for sensitive detection of CEA.

Effective detection of cancer biomarkers plays a crucial role in the prevention of early cancer. Here, a sandwich-type electrochemical immunosensor was successfully constructed for sensitive detection of carcinoembryonic antigen (CEA) using MoS2/CuS-Au as sensing platform and mulberry-like Au@PtPd porous nanorods (Au@PtPd MPs) as signal amplifiers. The large surface area and good biocompatibility of MoS2/CuS-Au increased the loading of primary antibody. And the good conductivity of MoS2/CuS-Au accelerated the electron transport rate of the electrode surface. Au@PtPd MPs with large specific surface area and a large number of catalytically active sites showed excellent electrocatalytic performance for hydrogen peroxide reduction. The sandwich-type immunosensor prepared by the signal amplification strategy exhibited a wide linear detection range (50 fg/mL to 100 ng/mL) and a low detection limit of 16.7 fg/mL (S/N = 3), featuring good selectivity, stability and reproducibility. Moreover, the satisfactory results in analysis of human serum samples indicated that it possessed a potential application promising in early clinical diagnoses.

An enzyme-free immunosensor for sensitive determination of procalcitonin using NiFe PBA nanocubes@TB as the sensing matrix.

In this work, a label-free electrochemical immunosensor was developed for the detection of procalcitonin (PCT), using toluidine blue functionalized NiFe Prussian-blue analog nanocubes (NiFe PBA nanocubes@TB) as a signal amplifier. NiFe PBA nanocubes was synthesized by a simple and efficient self-templating method in this work. NiFe PBA nanocubes with open-framework construction not only provides a larger specific area to load a mass of antibodies but produces an excellent signal without adding extra reaction reagent. Besides, the electrochemical performance of NiFe PBA nanocubes can be enhanced after functionalized with TB. The developed immunosensor exhibited favorable performance for PCT detection with a linear range from 0.001 to 25 ng mL-1 and a detection limit of 3 × 10-4 ng mL-1. Moreover, the immunosensor with acceptable reproducibility, selectivity, and stability may provide a new strategy in the clinical detection of PCT.

AuCu xO-Embedded Mesoporous CeO2 Nanocomposites as a Signal Probe for Electrochemical Sensitive Detection of Amyloid-Beta Protein.

A sandwich-type electrochemical immunosensor for detecting amyloid-beta protein was fabricated based on Au NP-functionalized reduced graphene oxide (Au@rGO) as an effective sensing platform and AuCu xO-embedded mesoporous CeO2 (AuCu xO@m-CeO2) nanocomposites as the catalytic matrix. The AuCu xO@m-CeO2 composites were obtained by adjusting the amount of m-CeO2 in the reaction to expose enormous active sites. Also, AuCu xO@m-CeO2 was applied as a matrix to immobilize antibodies by forming bridged bonds between m-CeO2 and carboxyl functional groups of antibodies without additional agents. Furthermore, AuCu xO with prominent catalytic activities dramatically improved the performance of the fabricated immunosensor. Also, the morphology, structure, and electronic state of the surface were characterized by SEM, XRD, TEM, and XPS. In addition, the immunosensor demonstrated a wide linear range of 100 fg mL-1 to 10 ng mL-1. This study may provide a way for sensitively detecting various biomarkers.

Sandwich-type electrochemical immunosensor based on Au@Pt DNRs/NH2-MoSe2 NSs nanocomposite as signal amplifiers for the sensitive detection of alpha-fetoprotein.

A sandwich-type electrochemical immunosensor was fabricated for the quantitation of alpha fetoprotein (AFP). To this end, the Au@Pt dendritic nanorods loaded with amino functionalized molybdenum selenide nanosheets (Au@Pt 41 DNRs/NH2-MoSe2 NSs) with enhanced peroxidase-like properties were selected as the secondary antibody label (Ab2) to achieve signal amplification. The as-obtained Au@Pt DNRs/NH2-MoSe2 NSs exhibited better catalytic activity toward hydrogen peroxide reduction and offered rich anchors for bioconjugation. Meanwhile, gold nanoparticles anchored on an amino functionalized graphene (Au NPs/NH2-GS) composite with admirable conductivity and biocompatibility was used as the matrix material to improve sensitivity. Under optimal conditions, amperometric current responses had a good linear relationship with the logarithm values of AFP concentration in the range 10 fg mL-1 to 200 ng mL-1 with a detection limit of 3.3 fg mL-1 (S/N = 3). Additionally, the immunosensor had excellent reproducibility, selectivity, and stability, which indicated superior performance for AFP detection compared with previous reports. The satisfactory results of human serum samples analysis showed that the designed immunosensor has potential applicability for the sensitive detection of other tumor markers.

Sandwich-type electrochemical immunosensor for sensitive detection of CEA based on the enhanced effects of Ag NPs@CS spaced Hemin/rGO.

An ultrasensitive sandwich-type electrochemical immunosensor was designed by using gold nanoparticles (Au NPs) as the substrate material and microporous carbon spheres (CS) loading silver nanoparticles (Ag NPs) spaced Hemin/reduced graphene oxide (Hemin/rGO) porous composite materials (Ag NPs@CS-Hemin/rGO) as the detection antibodies (Ab2) label for detecting carcinoembryonic antigen (CEA). The Au NPs with good electrical conductivity and biocompatibility could accelerate the electron transfer on the electrode interface and enhance the load capacity of capture antibodies (Ab1). Hemin is peroxidase-like substance which has excellent catalytic ability for H2O2 reduction but easy to molecular aggregation and oxidative self-destruction. Reduced graphene oxide (rGO) is a good supporting material for Hemin to mitigate this disadvantage. CS loading Ag NPs (Ag NPs@CS) as the spacer inserts into Hemin/rGO sheet can overcome the irreversible stacking of rGO, and form complex porous structure which exposes more active sites of Hemin. Moreover, Ag NPs loaded on CS also has catalytic ability for H2O2 reduction. Thus the Ag NPs@CS-Hemin/rGO used as the Ab2 label has a large working surface area and high utilization rate, which heightens the catalytic ability for H2O2 reduction to amplify the current signal effectually. The current signal and the logarithm of CEA concentration presented a wide linear response range of 20 fg/mL to 200 ng/mL, and the detection limit of CEA was 6.7 fg/mL. Furthermore, the designed immunosensor exhibited a good reproducibility, selectivity and stability, which confirms a broad development prospect when applying it in early clinical detection.