Antibody-Bridged DNAzyme Walker for Sensitive Detection of Small Molecules

Sensitive detection of small molecules with biological and environmental interests is important for many applications, such as food safety, disease diagnosis, and environmental monitoring. Herein, we propose a highly selective antibody-bridged DNAzyme walker to sensitively detect small molecules. The antibody-bridged DNAzyme walker consists of a track, small-molecule-labeled DNAzyme walking strand, and antibody against small molecules. The track is built by co-modifying fluorophore-labeled substrates and small-molecule-labeled DNA linkers onto a gold nanoparticle (AuNP). In the absence of the target molecule, the antibody binds small molecule labels at the DNAzyme walking strand and the DNA linker, driving the DNAzyme walking strand on the surface of the AuNP. The attached DNAzyme walking strand moves along the track and cleaves substrates to generate high fluorescence signals to achieve signal amplification. As target molecules exist, they competitively bind with antibody to displace the small-molecule-labeled linker and DNAzyme walking strand, rendering the DNAzyme walker inactive in substrate cleavage and causing weak fluorescence. By using this antibody-bridged DNAzyme walker, we achieved sensitive detection of two biologically important small molecules, digoxin and folic acid. This work provides a new paradigm by combining the signal amplification strategy of a DNA walker and immunorecognition for sensitive and selective detection of small molecules

Structure, fluorescence, and carbon dioxide capture of a carboxylate cadmium complex

<p>A new cadmium complex, [Cd₂(dcpa)·2H₂O]_<i>n</i>·H₂O (<b>1</b>), has been synthesized by hydrothermal reaction based on the multiple acid ligand 4-(2,5-dicarboxyphenoxy)phthalic acid (H₄dcpa). Single crystal X-ray diffraction analysis reveals that <b>1</b> is a three-dimensional structure with pores. The fluorescence test results show that the complex has excellent blue fluorescence. The adsorption of nitrogen and carbon dioxide gas test results show that the complex has adsorption effects on carbon dioxide.</p

Fluorescence Anisotropy Reduction of Allosteric Aptamer for Sensitive and Specific Protein Signaling

Real time protein signaling in a complex medium may provide a promising way for high-throughput protein analysis, but it is largely unmet due to the challenge of signal transduction and the interferences of nonspecific binding and high background. Our recent work indicates that a fluorescent aptamer can display a protein binding-induced reduction of fluorescence anisotropy (FA) (Zhang, D.; Lu, M.; Wang, H. <i>J. Am. Chem. Soc.</i> <b>2011</b>, <i>133</i>, 9188–9191), which is exclusively different from a traditionally simplified concept hinting a molecular size increase-induced FA increase. Inspired by this unexpected observation, we describe a novel FA reduction approach for protein signaling. The feasibility of this approach is demonstrated through the assays of a blood protein human α-thrombin and an oncoprotein human platelet-derived growth factor B-chain (PDGF-BB) using two screened fluorescent aptamers, respectively. By the developed FA reduction method, the spiked human α-thrombin in diluted serum can be detected at the concentration as low as 250 pM. In contrast, in a traditional molecular size-dependent FA assay, the thrombin spiked in diluted serum cannot induce reliable FA change even at a 256-fold higher concentration (64 nM). The results clearly show that the FA reduction approach has a dramatically enhanced specificity against target protein and high sensitivity in complex medium and is applicable to the no-separation based detection of proteins in biological matrixes

Aptamer Capturing of Enzymes on Magnetic Beads to Enhance Assay Specificity and Sensitivity

Activity and specificity of enzyme molecules are important to enzymatic reactions and enzyme assays. We describe an aptamer capturing approach that improves the specificity and the sensitivity of enzyme detection. An aptamer recognizing the target enzyme molecule is conjugated on a magnetic bead, increasing the local concentration, and serves as an affinity probe to capture and separate minute amounts of the enzyme. The captured enzymes catalyze the subsequent conversion of fluorogenic substrate to fluorescent products, enabling a sensitive measure of the active enzyme. The feasibility of this technique is demonstrated through assays for human alpha thrombin and human neutrophil elastase (HNE), two important enzymes. Thrombin (2 fM) and 100 fM HNE can be detected. The incorporation of two binding events, substrate recognition and aptamer binding, greatly improves assay specificity. With its simplicity, this approach is applicable to biosensing and detection of disease biomarkers

Tuning the Pore Size in Gradient Poly(ionic liquid) Membranes by Small Organic Acids

Highly charged porous polymer membranes with adjustable pore size and gradient pore structure along the membrane cross-section were prepared by ammonia-triggered electrostatic complexation between an imidazolium-based cationic poly­(ionic liquid) (PIL) and multivalent benzoic acid derivatives. The PIL and the acid compound were first dissolved homogeneously in DMSO, cast into a thin film onto a glass plate, dried, and finally immersed into an aqueous ammonia solution. The diffusion of ammonia from the top to the bottom into the film neutralized the acid and introduced the gradient pore structure and in situ electrostatic cross-linking to fix the pores. The pore size and its distribution of the membranes were found controllable in terms of the multivalency of the acids, the imidazolium/carboxylate ratio, and the nature of the PIL counteranion

Smart Nanocarrier: Self-Assembly of Bacteria-like Vesicles with Photoswitchable Cilia

Bioinspired cell deformation aids in the design of smart functional molecular self-assemblies. We report on a system of bacteria-like vesicles which release entrapped drug upon developing hairs triggered by UV irradiation, just like cilia stretching from the surface of bacteria. The formation of cilia leads to a less intact membrane, which allows release of entrapped drug. This bioinspired design created a smart nanocarrier that releases the payload <i>via</i> deformation rather than complete breaking

Luminescent Chemodosimeters for Bioimaging

Luminescent Chemodosimeters for Bioimagin

Poly(ionic liquid) Complex with Spontaneous Micro-/Mesoporosity: Template-Free Synthesis and Application as Catalyst Support

A facile, template-free synthetic route is reported toward poly­(ionic liquid) complexes (PILCs) which for the first time exhibit stable micro-/mesoporous structure. This is accomplished via <i>in situ</i> ionic complexation between imidazolium-based PILs and poly­(acrylic acid) in various alkaline organic solvents. The PILC can be highly loaded with copper salts and can be used as a catalytic support for effective aerobic oxidation of activated hydrocarbons under mild conditions

Functional Near Infrared-Emitting Cr³⁺/Pr³⁺ Co-Doped Zinc Gallogermanate Persistent Luminescent Nanoparticles with Superlong Afterglow for <i>in Vivo</i> Targeted Bioimaging

Near infrared (NIR)-emitting persistent luminescent nanoparticles (PLNPs) have great potential for <i>in vivo</i> bioimaging with the advantages of no need for <i>in situ</i> excitation, high signal-to-noise ratio, and deep tissue penetration. However, functional NIR-emitting PLNPs with long afterglow for long-term <i>in vivo</i> imaging are lacking. Here, we show the synthesis of NIR-emitting long-persistent luminescent nanoparticles (LPLNPs) Zn_2.94Ga_1.96Ge₂O₁₀:Cr³⁺,Pr³⁺ by a citrate sol–gel method in combination with a subsequent reducing atmosphere-free calcination. The persistent luminescence of the LPLNPs is significantly improved via codoping Pr³⁺/Cr³⁺ and creating suitable Zn deficiency in zinc gallogermanate. The LPLNP powder exhibits bright NIR luminescence in the biological transparency window with a superlong afterglow time of over 15 days. A persistent energy transfer between host and Cr³⁺ ion in the LPLNPs is observed and its mechanism is discussed. PEGylation greatly improves the biocompatibility and water solubility of the LPLNPs. Further bioconjugation with c­(RGDyK) peptide makes the LPLNPs promising for long-term <i>in vivo</i> targeted tumor imaging with low toxicity