Molecular Recognition Strategy Research Articles

Molecular Recognition Regulates Coordination Structure of Single‐Atom Sites

AbstractCoordination engineering for single‐atom sites has drawn increasing attention, yet its chemical synthesis remains a tough issue, especially for tailorable coordination structures. Herein, a molecular recognition strategy is proposed to fabricate single‐atom sites with regulable local coordination structures. Specifically, a heteroatom‐containing ligand serves as the guest molecule to induce coordination interaction with the metal‐containing host, precisely settling the heteroatoms into the local structure of single‐atom sites. As a proof of concept, thiophene is selected as the guest molecule, and sulfur atoms are successfully introduced into the local coordination structure of iron single‐atom sites. Ultrahigh oxygen reduction electrocatalytic activity is achieved with a half‐wave potential of 0.93 V versus reversible hydrogen electrode. Furthermore, the strategy possesses excellent universality towards diversified types of single‐atom sites. This work makes breakthroughs in the fabrication of single‐atom sites and affords new opportunities in structural regulation at the atomic level.

Molecular Recognition Regulates Coordination Structure of Single-Atom Sites.

Coordination engineering for single-atom sites has drawn increasing attention, yet its chemical synthesis remains a tough issue, especially for tailorable coordination structures. Herein, a molecular recognition strategy is proposed to fabricate single-atom sites with regulable local coordination structures. Specifically, a heteroatom-containing ligand serves as the guest molecule to induce coordination interaction with the metal-containing host, precisely settling the heteroatoms into the local structure of single-atom sites. As a proof of concept, thiophene is selected as the guest molecule, and sulfur atoms are successfully introduced into the local coordination structure of iron single-atom sites. Ultrahigh oxygen reduction electrocatalytic activity is achieved with a half-wave potential of 0.93 V versus reversible hydrogen electrode. Furthermore, the strategy possesses excellent universality towards diversified types of single-atom sites. This work makes breakthroughs in the fabrication of single-atom sites and affords new opportunities in structural regulation at the atomic level.

Reversible control of tetrazine bioorthogonal reactivity by naphthotube-mediated host-guest recognition

•Naphthotubes can recognize phenyltetrazine-modified biomolecules with high affinity •Reversible control of phenyltetrazine reactivity through molecular recognition •Selective tetrazine residue caging enables sequential IEDDA reactions on proteins •Reversible caging of phenyltetrazine activity in living cells and animals Tetrazine-mediated inverse electron demand Diels-Alder (IEDDA) reactions are widely used ultrafast bioorthogonal reactions, and methods to control such reactions would be extremely useful. Here, we identified a high-affinity host-guest pair between synthetic macrocyclic naphthotubes and phenyltetrazine and developed a molecular-recognition strategy for controlling tetrazine reactions by host caging. Naphthotubes can recognize phenyltetrazine on various biomolecules with low-micromolar and sub-micromolar binding affinities and thus cage their IEDDA reactivity efficiently in a reversible manner. For tetrazine residues on proteins encoded by non-canonical amino acid mutagenesis, their positions could be computationally designed such that exposed residues could be reversibly caged, whereas semiburied residues that were resistant to caging retained their reactivity, thus allowing preparation of site-specific protein dual conjugates and dual protein labeling on living cells with IEDDA reactions. The reactivity of tetrazine can be further regulated in living animals. Our strategy is thus expected to expand the applications of tetrazine chemistry. Tetrazine-mediated inverse electron demand Diels-Alder (IEDDA) reactions are widely used ultrafast bioorthogonal reactions, and methods to control such reactions would be extremely useful. Here, we identified a high-affinity host-guest pair between synthetic macrocyclic naphthotubes and phenyltetrazine and developed a molecular-recognition strategy for controlling tetrazine reactions by host caging. Naphthotubes can recognize phenyltetrazine on various biomolecules with low-micromolar and sub-micromolar binding affinities and thus cage their IEDDA reactivity efficiently in a reversible manner. For tetrazine residues on proteins encoded by non-canonical amino acid mutagenesis, their positions could be computationally designed such that exposed residues could be reversibly caged, whereas semiburied residues that were resistant to caging retained their reactivity, thus allowing preparation of site-specific protein dual conjugates and dual protein labeling on living cells with IEDDA reactions. The reactivity of tetrazine can be further regulated in living animals. Our strategy is thus expected to expand the applications of tetrazine chemistry. Bioorthogonal chemistry: Bridging chemistry, biology, and medicineHartung et al.ChemJune 5, 2023In BriefBioorthogonal chemistry has become a flourishing toolbox of approaches for performing selective reactions in complex biological systems without perturbing natural processes. Through the implementation of this chemistry, chemical biologists have answered previously unanswerable questions, made new and exciting discoveries, and even begun to have an impact on important therapies, including implementing a bioorthogonal reaction at the center of a new cancer-treatment clinical trial. We highlight some key advances and anticipate next steps within this latest Nobel Prize-winning field. Full-Text PDF

Parallel G-Quadruplex DNA Structures from Nuclear and Mitochondrial Genomes Trigger Emission Enhancement in a Nonfluorescent Nano-aggregated Fluorine-Boron-Based Dye.

Molecular self-assembly is a powerful tool for the development of functional nanostructures with adaptive optical properties. However, in aqueous solution, the hydrophobic effects in the monomeric units often afford supramolecular architectures with typical side-by-side π-stacking arrangement with compromised emissive properties. Here, we report on the role of parallel DNA guanine quadruplexes (G4s) as supramolecular disaggregating-capture systems capable of coordinating a zwitterionic fluorine-boron-based dye and promoting activation of its fluorescence signal. The dye's high binding affinity for parallel G4s compared to nonparallel topologies leads to a selective disassembly of the dye's supramolecular state upon contact with parallel G4s. This results in a strong and selective disaggregation-induced emission that signals the presence of parallel G4s observable by the naked eye and inside cells. The molecular recognition strategy reported here will be useful for a multitude of affinity-based applications with potential in sensing and imaging systems.

Sensing guanine and its derivatives: From molecular recognition to applications

Guanine plays an indispensable role in building nucleic acids, and its derivatives take part in various cellular functions such as regulating biological reactions and signal transduction. Monitoring the levels of guanine and its derivatives is critical for understanding their biological roles and related diseases. Aside from traditional chromatography-based methods, majority of the current detections were based on electrochemistry and the oxidation activity of guanine, for which guanine and adenine often had a similar response. Over the last 30 years, various new sensing strategies have been developed. To provide researchers with more options for specific sensing of guanine and its derivatives, herein we review molecular recognition strategies based on nucleic acids, proteins, small organic molecules, molecularly imprinted polymers to nanomaterials. The mechanism of each molecular recognition strategy is discussed. Based on these target recognition molecules, we also critically review representative fluorescent and electrochemical sensors for guanine-related analytes from an application point of view, and provide readers with our perspectives to further grow this direction.

Double molecular recognition strategy based on boronic acid-diol and NHS ester-amine for selective electrochemical detection of cerebral dopamine.

Electrochemical detection of dopamine (DA) usually depends on electrochemical oxidation of DA. This conventional method can hardly provide sufficient sensitivity and selectivity in the determination of the cerebral DA down to nanomolar level, because the ability of DA to be electrochemically oxidized is limited and many electroactive interferents are also oxidized at a similar potential with DA. Here, an electrochemical assay based on a double molecular recognition strategy has been proposed and proved to be of high sensitivity and selectivity for DA measurement in the cerebral system. 3,3'-Dithiodipropionic acid di(N-hydroxysuccinimide ester) (DSP) was anchored on the electrode surface to capture DA target through the specific reaction between N-hydroxysuccinimide (NHS) ester and amine. The captured DA endowed the electrode with a layer of diol groups, which further reacted with the boronic acid to trap of 4-mercaptophenylboronic acid (MBA) molecules, thus leading to the conjunction of electroactive thionine (Th) molecules on the electrode for signal readout. In addition, an Au nanostructure was employed to enhance signal amplification and facilitate the double molecular recognition process. As a consequence, this method was able to quantify DA from 1 to 300nM with a detection limit of 0.74nM, which exhibited a high specificity against cerebral interferents. Furthermore, the practicability of this platform was successfully demonstrated through determination of the dynamics of cerebral DA in the events of high K+ and nomifensine retromicrodialysis. Graphical abstract.

Surface Plasmon Resonance-Based Membrane Protein-Targeted Active Ingredients Recognition Strategy: Construction and Implementation in Ligand Screening from Herbal Medicines

Membrane proteins (MPs) are playing important roles in several biological processes. Screening new candidate compounds targeting MPs is important for drug discovery. However, it remains challenging to characterize the interactions between MPs and small-molecule ligands in a label-free method. In this study, a surface plasmon resonance (SPR)-based membrane protein-targeted active ingredients recognition strategy was constructed. This strategy contains two major modules: affinity detection module and ligand screening module. Through the combination of these two functional modules, it is feasible to screen small molecular ligands targeting MPs from herbal medicines. First, we have constructed high/low comparative C-X-C chemokine receptor type 4 (CXCR4)-expressed lentiviral particles (LVPs) models and characterized the expression levels. Then we immobilized LVPs on CM5 chips and detected the affinity between AMD3100 and CXCR4 by using affinity detection module. The KD of AMD3100 was 32.48 ± 3.17 nM. Furthermore, the suitability and robustness of the ligand screening module were validated by using AMD3100 as a positive compound. Subsequently, this module was applied in the screening of CXCR4 small molecular ligands from herbal medicine extracts. Senkyunolide I was screened out from Chuanxiong extract. The affinity constant between senkyunolide I and CXCR4 was 2.94 ± 0.36 μM. The Boyden chamber assay revealed that senkyunolide I could inhibit cell migration process. In conclusion, an SPR-based small molecular ligand recognition strategy combined with virus-based membrane protein stabilization method was constructed. The SPR-based membrane protein-targeted active ingredients recognition strategy will be an effective tool to screen target components from complex systems acting on MPs.

Incorporation of Boronic Acid into Aptamer-Based Molecularly Imprinted Hydrogels for Highly Specific Recognition of Adenosine.

Molecularly imprinted polymers (MIPs) and aptamers are two types of molecular recognition strategies. We are interested in combining them to further improve specificity. Adenosine is a model analyte for developing aptamer-based biosensors, but the most commonly used DNA aptamer for adenosine can also bind deoxyadenosine with a similar affinity (Ka (adenosine)/Ka (deoxyadenosine) = 1.07). Since adenosine and deoxyadenosine differ by the former having a cis-diol, and boronic acid can bind cis-diol specifically, in this work, an acrydite-modified adenosine aptamer was copolymerized with a boronic acid containing monomer, 3-acrylamidophenylboronic acid (AAPBA) in the presence of adenosine as the template for imprinting. Isothermal titration calorimetry (ITC) and SYBR Green I staining were used to measure its binding. The AAPBA-containing aptamer-MIP exhibited a 115-fold high selectivity for adenosine against deoxyadenosine at pH 6.4, and 230-fold for adenosine against cytidine. We recently found that boronic acid containing hydrogels can nonspecifically adsorb DNA oligonucleotides and inhibit aptamer binding. The ribose in adenosine may interact with the boronic acid unit and decrease its inhibition effect to the aptamer in the MIP. However, for deoxyadenosine, it does not bear a cis-diol and thus cannot rescue the aptamer. This work provides insight into the combination of aptamers with other functional groups, which may further broaden applications in ways that free aptamers cannot achieve alone.

Structure of the saxiphilin:saxitoxin (STX) complex reveals a convergent molecular recognition strategy for paralytic toxins.

Dinoflagelates and cyanobacteria produce saxitoxin (STX), a lethal bis-guanidinium neurotoxin causing paralytic shellfish poisoning. A number of metazoans have soluble STX-binding proteins that may prevent STX intoxication. However, their STX molecular recognition mechanisms remain unknown. Here, we present structures of saxiphilin (Sxph), a bullfrog high-affinity STX-binding protein, alone and bound to STX. The structures reveal a novel high-affinity STX-binding site built from a "proto-pocket" on a transferrin scaffold that also bears thyroglobulin domain protease inhibitor repeats. Comparison of Sxph and voltage-gated sodium channel STX-binding sites reveals a convergent toxin recognition strategy comprising a largely rigid binding site where acidic side chains and a cation-π interaction engage STX. These studies reveal molecular rules for STX recognition, outline how a toxin-binding site can be built on a naïve scaffold, and open a path to developing protein sensors for environmental STX monitoring and new biologics for STX intoxication mitigation.

Advance in boronate affinity-based controllable orientedsurface imprinting

Biomolecules, like antibody, aptamer and lectin, are still the main force for applications involved in selective separation and recognition. However, these biomolecules are usually suffered from many inevitable problems, such as hard to prepare, high cost, poor stability, as well as limited quantities. Molecular imprinting technique (MIT) as a robust biomimetic molecular recognition strategy to mimic the targeting ability of antibody and enzyme plays a significant role in many areas, including chemical separation, biosensing, catalysis, disease diagnosis, etc. Scientists have pay a lot of attention to developing advanced imprinting approaches to enable MIT adapt many more possible applications. Several user-friendly molecular imprinting methods, such as surface imprinting, epitope imprinting and emulsion imprinting, are hence developed to meet the high analytical requirements. Even so, facile MITs with wide-range versatility and high imprinting efficiency are extremely limited, which restrict the applicability of MIT. Boronate affinity-based controllable oriented surface imprinting (BACOSI) allows for easy and efficient preparation of molecularly imprinted polymers specific to saccharide compounds, which covering glycoproteins, glycopeptides, glycans and monosaccharides. In this paper, the principle, preparation process, applications and recent developments of BACOSI are briefly introduced. Three steps, namely template immobilization, oriented imprinting and template removal, are included in this approach. Template molecules (glycoprotein, glycopeptide, glycan or monosaccharide) immobilized on the surface of boronic-acid-functionalized substrate by virtue of boronate affinity interaction, followed by controllable self-polymerization of biocompatible monomer(s) to form an imprinting layer on the template-anchored substrate with tailored thickness in terms of molecule size of templates, and then the templates are effectively removed under suitable conditions (weak acidic solutions with or without surfactant are often utilized for templates removal). Imprinting in this approach is performed in a precise-controllable manner permitting the thickness of the imprinting layer to be fine-tuned via adjusting the imprinting time. This manner not only simplifies the imprinting procedure but also makes the approach widely applicable to a large range of sugar-containing biomolecules. Most of all, it can provide a guidance for design and preparation of other biomimetic molecular recognition materials, and a new level in methodology of MIT has been promoted by the presentation of this approach. In addition, some issues and future prospects of BACOSI are also presented in this paper based on our previous researches. From the viewpoint of preparation mechanism, template anchoring of BACOSI highly relies on the boronate affinity effect between boronic acid and cis-diol groups, thus it does not work for non- cis-diol -containing compounds. Exploiting some other means for template immobilization or template-anchoring-free imprinting modes is benefit for extending the application scope of BACOSI. Likewise, ideal biocompatibility and the ability of targeting are also significant for biological applications, for instance, cell imaging, clinical diagnosis and therapy. (Nevertheless, available aqueous phase polymerization for BACOSI is very limited, and its non-specific effect is also cannot be ignored when used for clinical analysis. The further study and exploration of imprinting system with negligible non-specific effect and suitable for the biomedical analysis is the key to form practical imprinting technology). In summary, BACOSI strategy just opens the pathway for the research and application based on facile and versatile imprinting technique in the future, there is still a long distance from being ready for use on industrial production and commercialization.

Nucleoside Analogue-Based Supramolecular Nanodrugs Driven by Molecular Recognition for Synergistic Cancer Therapy.

The utilization of nanotechnology for the delivery of a wide range of anticancer drugs has the potential to reduce adverse effects of free drugs and improve the anticancer efficacy. However, carrier materials and/or chemical modifications associated with drug delivery make it difficult for nanodrugs to achieve clinical translation and final Food and Drug Administration (FDA) approvals. We have discovered a molecular recognition strategy to directly assemble two FDA-approved small-molecule hydrophobic and hydrophilic anticancer drugs into well-defined, stable nanostructures with high and quantitative drug loading. Molecular dynamics simulations demonstrate that purine nucleoside analogue clofarabine and folate analogue raltitrexed can self-assemble into stable nanoparticles through molecular recognition. In vitro studies exemplify how the clofarabine:raltitrexed nanoparticles could greatly improve synergistic combination effects by arresting more G1 phase of the cell cycle and reducing intracellular deoxynucleotide pools. More importantly, the nanodrugs increase the blood retention half-life of the free drugs, improve accumulation of drugs in tumor sites, and promote the synergistic tumor suppression property in vivo.

Dual molecular recognition strategy for highly sensitive electrochemical detection of dopamine based on amplification of DNA–Au bio–bar codes

We had reported an electrochemical assay for dopamine with high sensitivity and selectivity based on dual molecular recognition strategy and amplification of DNA–Au bio–bar codes. In this assay, carbon nanotubes were first immobilized on the glass carbon electrode surface. Subsequently, a boronic acid-functionalized pyrene probe was self-assembled on the sidewalls of carbon nanotubes via π–π stacking interactions as a capture probe. 3,3′-Dithiodipropionic acid di(N-hydroxysuccinimide ester) (DSP) and double strands DNA functionalized AuNPs (DSP/AuNPs/dsDNA) were designed as signal probes and characterized by transmission electron microscopy and spectroscopic techniques. Upon the binding of dopamine with boronic acid followed by DSP/AuNPs/dsDNA, the AuNPs were captured on the electrode surface to enhance the signal. RuHex, an electroactive complex, which could bind to the anionic phosphate of DNA strands through electrostatic interaction, serves as signaling transducer. Signal amplification and dual recognition were used to quantify dopamine concentration from 30 pM to 30 nM, with a detection limit of 18 pM. Other small molecules could be measured by this assay after modification with differential recognition molecules.

Molecular recognition strategy for detection and antimicrobial susceptibility testing of Staphylococcus aureus by utilizing teicoplanin and porcine IgG as indicator molecules

Timely and accurate anti-infective therapy significantly benefits treatment of various life-threatening bacterial infectious diseases. Unfortunately, owing to the lack of selectivity for recognizing bacterial species, most of the reported phenotypic antimicrobial susceptibility testing protocols suffer from time-consuming bacterial isolation and identification. In this work, a highly-selective molecular recognition-based sandwich fluorimetric assay was developed to rapidly detect Staphylococcus aureus (S. aureus), and furtherly to assess its susceptibility to antibiotics. Immobilized porcine IgG was utilized to capture S. aureus through the selective interaction between Fc fragment of porcine IgG and protein A in the cell wall of S. aureus. Fluorescein isothiocyanate-labeled teicoplanin was adopted as the signal tracer utilizing the binding behavior between teicoplanin and d-Ala-d-Ala moieties in the peptidoglycans of Gram-positive bacterial cell wall. S. aureus could be detected within a wide linear rang of 1.0 × 103 to 1.0 × 107 CFU mL−1. Subsequently, this protocol utilizing porcine IgG and teicoplanin as the indicator molecules was utilized to assess the antimicrobial susceptibility of S. aureus after the bacteria were treated with antibiotics. The minimum inhibitory concentrations of penicillin, cefoxitin, clindamycin, trimethoprim/sulfamethoxazole and erythromycin were estimated to be >0.25,<4, <0.25, <2/38 and <0.5 μg mL−1, respectively. The whole process for antimicrobial susceptibility testing can be completed within 4 h since it avoided extra time-consuming isolation and identification of bacterial species.

Assembly-enhanced molecular recognition of calix[6]arene

We comparatively investigated the molecular recognition of the amphiphilic derivatives of p-sulfonatocalix[n]arenes (SCnA-Rs, n = 4 and 6) both in aqueous solution and at the interface of liposome. When the recognition events transfer from aqueous solution to the self-assembled interface, the binding capability of SC6A-R increases drastically, but not for SC4A-R. It originates from the conformational regulation that the complicated conformation of SC6A-R in aqueous solution was immobilized to the cone shape upon embedding SC6A-R into the liposome. The resulting cone shape is privileged to accommodate guests into its cavity. Such an assembly-enhanced molecular recognition strategy could be transferable to other macrocyclic, acyclic, artificial, and natural receptors with conformational flexibility.

Using Host-Guest Chemistry to Tune the Kinetics of Morphological Transitions Undertaken by Block Copolymer Vesicles.

Host-guest chemistry is exploited to tune the rate at which block copolymer vesicles undergo morphological transitions. More specifically, a concentrated aqueous dispersion of poly(glycerol monomethacrylate-co-glycidyl methacrylate)-poly(2-hydroxypropyl methacrylate) [P(GMA-co-GlyMA)-PHPMA] diblock copolymer vesicles was prepared via polymerization-induced self-assembly (PISA). The epoxy groups in the GlyMA residues were ring-opened using a primary amine-functionalized β-cyclodextrin (NH2-β-CD) in order to prepare β-CD-decorated vesicles. Addition of azobenzene-methoxypoly(ethylene glycol) (azo-mPEG) to such vesicles results in specific binding of this water-soluble macromolecular reagent to the β-CD groups on the hydrophilic P(GMA-co-GlyMA) stabilizer chains. Such host-guest chemistry induces a morphological transition from vesicles to worms and/or spheres. Furthermore, the rate of this morphological transition can be tuned by UV/visible-light irradiation and/or guest molecule competition. This novel molecular recognition strategy offers considerable scope for the design of new stimulus-responsive diblock copolymer vesicles for targeted delivery and controlled release of cargoes.

Native protein hydrogels by dynamic boronic acid chemistry

Bioactive protein-based materials are unique functional systems that incorporate the specificity and intelligent characteristics of biomolecules within synthetic polymers. Herein, we take advantage of the boronic acid/salicyl hydroxamate molecular recognition strategy to crosslink an apoptosis inducing enzyme, cytochrome c, by dynamic covalent interactions to form a bioactive and responsive hydrogel for controlled administration. The material exhibits attractive rheological properties with high storage modulus and modulus crossover despite the perceived conformational sensitivity of the proteins. Upon acidification, the hydrogel matrix dissociated and release active enzymes into A549 cells, which initiates apoptosis. In combination, the chemical strategy facilitates the integration of native enzymes structurally into the hydrogel scaffold while simultaneously providing biological activity under a stimulus controlled release mechanism.

Using Dynamic Covalent Chemistry To Drive Morphological Transitions: Controlled Release of Encapsulated Nanoparticles from Block Copolymer Vesicles.

Dynamic covalent chemistry is exploited to drive morphological order–order transitions to achieve the controlled release of a model payload (e.g., silica nanoparticles) encapsulated within block copolymer vesicles. More specifically, poly(glycerol monomethacrylate)–poly(2-hydroxypropyl methacrylate) (PGMA–PHPMA) diblock copolymer vesicles were prepared via aqueous polymerization-induced self-assembly in either the presence or absence of silica nanoparticles. Addition of 3-aminophenylboronic acid (APBA) to such vesicles results in specific binding of this reagent to some of the pendent cis-diol groups on the hydrophilic PGMA chains to form phenylboronate ester bonds in mildly alkaline aqueous solution (pH ∼ 10). This leads to a subtle increase in the effective volume fraction of this stabilizer block, which in turn causes a reduction in the packing parameter and hence induces a vesicle-to-worm (or vesicle-to-sphere) morphological transition. The evolution in copolymer morphology (and the associated sol–gel transitions) was monitored using dynamic light scattering, transmission electron microscopy, oscillatory rheology, and small-angle X-ray scattering. In contrast to the literature, in situ release of encapsulated silica nanoparticles is achieved via vesicle dissociation at room temperature; moreover, the rate of release can be fine-tuned by varying the solution pH and/or the APBA concentration. Furthermore, this strategy also works (i) for relatively thick-walled vesicles that do not normally exhibit stimulus-responsive behavior and (ii) in the presence of added salt. This novel molecular recognition strategy to trigger morphological transitions via dynamic covalent chemistry offers considerable scope for the design of new stimulus-responsive copolymer vesicles (and hydrogels) for targeted delivery and controlled release of cargoes. In particular, the conditions used in this new approach are relevant to liquid laundry formulations, whereby enzymes require protection to prevent their deactivation by bleach.

The electrochemiluminescence resonance energy transfer between Fe-MIL-88 metal–organic framework and 3,4,9,10-perylenetetracar-boxylic acid for dopamine sensing

Here, the cathodic electrochemiluminescence (ECL) behavior of 3,4,9,10-perylenetetracar-boxylic acid (PTCA) coreacted with hydrogen peroxide was firstly reported. The quenching effect of Fe-MIL-88 MOFs (iron based metal-organic framework) on the ECL of PTCA was found, and the ECL quenching mechanism was investigated, which was speculated to be via the resonance energy transfer from PTCA to Fe-MIL-88 MOFs and steric hindrance effect from Fe-MIL-88 MOFs. Combining with dual molecular recognition strategy and the quenching effect of Fe-MIL-88 MOFs on the ECL of PTCA-H2O2 system, an “on-off” ECL sensor was designed to detect dopamine (DA) with a broad linear range (five orders of magnitude). The detection limit was low to 2.9×10−13M. The PTCA-H2O2 system would provide a new ECL platform, especially for constructing enzyme based ECL sensor with H2O2 as product in enzymatic reaction. Furthermore, the electrochemiluminescence resonance energy transfer between Fe-MIL-88 metal–organic framework and PTCA would expand a new application of Fe-MIL-88 MOFs in ECL field. The dual molecular recognition strategy ensured the selectivity of the sensor for DA detection.

A dual-potential electrochemiluminescence ratiometric sensor for sensitive detection of dopamine based on graphene-CdTe quantum dots and self-enhanced Ru(II) complex

A novel dual-potential ratiometric electrochemiluminescence (ECL) sensor was designed for detecting dopamine (DA) based on graphene-CdTe quantum dots (G-CdTe QDs) as the cathodic emitter and self-enhanced Ru(II) composite (TAEA-Ru) as the anodic emitter. TAEA-Ru was prepared by linking ruthenium(II) tris(2,2′-bipyridyl-4,4′-dicarboxylato) with tris(2-aminoethyl)amine. Firstly, 3-aminopropyltriethoxysilane founctionalized G-CdTe QDs was used as the substrate for capturing target DA via the specific recognition of the diol of DA to the oxyethyl group of APTES. Then, Cu2O nanocrystals supported TAEA-Ru was further bound by the strong interaction between amino groups of DA and carboxyl groups of the Cu2O-TAEA-Ru. With the increase in DA concentration, the loading of Cu2O-TAEA-Ru at the electrode increased. As a result, the anodic ECL signal from TAEA-Ru increased, and the cathodic ECL signal from G-CdTe QDs/O2 system decreased correspondingly. Such a decrease was resulted from the ECL resonance energy transfer (RET) from G-CdTe QDs to TAEA-Ru as well as the dual quenching effects of Cu2O to G-CdTe QDs, namely the ECL-RET from G-CdTe QDs to Cu2O and the consumption of coreactant O2 by Cu2O. Based on the ratio of two ECL signals, the determination of DA was achieved with a linear range from 10.0 fM to 1.0nM and a detection limit low to 2.9 fM (S/N=3). The combination of G-CdTe QDs/O2 and TAEA-Ru would break the limitation of the same coreatant shared in previous ECL ratiometric systems and provide a potential application of ECL ratiometric sensor in the detection of biological small molecules with the assistance of the dual molecular recognition strategy.

Electrochemiluminescence sensor for dopamine with a dual molecular recognition strategy based on graphite-like carbon nitride nanosheets/3,4,9,10-perylenetetracarboxylic acid hybrids

Preparation of an ECL sensor and graphite-like carbon nitride nanosheets/3,4,9,10-perylenetetracarboxylic acid hybrids.