Cataluminescence-Based Array Imaging for High-Throughput Screening of Heterogeneous Catalysts

High-throughput screening of catalysts could dramatically improve performance and reduce costs in the discovery and study of various catalysts. Here we report a cataluminescence-based array imaging as a high-throughput screening technique in the combinatorial discovery of active catalysts for CO oxidation. This strategy is based on the fact that the CO oxidation generates cataluminescence emission on the surface of nanomaterials, whose intensity is correlated to the activity of the catalyst. To demonstrate the feasibility of the cataluminescence-based array imaging for high-throughput screening of catalysts, different nanosized metal catalysts supported on TiO2 nanoparticles were prepared. These catalysts include monometallic Au, Pt, and the bimetallic Au−Pt heteroaggregate catalysts, at total metal loadings of 0.5%, 1.0%, and 2.5%, and with atomic ratios of 1:1, 1:2, and 2:1 (Au/Pt). A 4 × 4 array was integrated by depositing these nanosized catalysts onto the ceramic chip, and the brightness of each spot in the image was recorded. The catalytic activities of those catalysts for the CO oxidation were evaluated parallelly by both the cataluminescence imaging and the gas chromatography method. The correlation coefficient is 0.914 for the two techniques, indicating that the cataluminescence imaging technique can be applied for the evaluation of the catalytic activities. Moreover, fast evaluation of multiple catalysts at a series of working temperature can be achieved by this cataluminescene-based array imaging. With the development of nanotechnology as well as the catalyst industry, the cataluminescence-based array imaging will address its importance in the high-throughput screening of catalysts

Spatiotemporally Controlled DNA Nanoclamps: Single-Molecule Imaging of Receptor Protein Oligomerization

Cell membrane surface receptor proteins play an important role in cellular biological processes. There are numerous methods to detect receptors, yet developing an artificially controlled and specific detection and treatment strategy remains a challenge. Herein, we develop such a strategy based on upconversion nanoparticles (UCNPs) loaded DNA probes that enable two-color ratiometric imaging excitated by a 980 nm laser. The light response controllable signal opening strategy avoids waste during probe transportation and improves sensitivity. Thereby the number of receptors on individual DU145 cell membranes is counted by single-molecule detection. Due to the different expression of specific receptor proteins, the number of single fluorescent dots counted can be used as a basis for distinguishing DU145 from other cells. This work is highly controllable to increase sensitivity, providing a platform for cancer diagnosis and treatment

Computation-Assisted Design of ssDNA Framework Nanorobots for Cancer Logical Recognition, Toehold Disintegration, Visual Dual-Diagnosis, and Synergistic Therapy

Single-stranded DNA (ssDNA) allows flexible and directional modifications for multiple biological applications, while being greatly limited by their poor stability, increased folding errors, and complicated sequence optimizations. This greatly challenges the design and optimization of ssDNA sequences to fold stable 3D structures for diversified bioapplications. Herein, the stable pentahedral ssDNA framework nanorobots (ssDNA nanorobots) were intelligently designed, assisted by examining dynamic folding of ssDNA in self-assemblies via all-atom molecular dynamics simulations. Assisted by two functional siRNAs (S1 and S2), two ssDNA strands were successfully assembled into ssDNA nanorobots, which include five functional modules (skeleton fixation, logical dual recognition of tumor cell membrane proteins, enzyme loading, dual-miRNA detection and synergy siRNA loading) for multiple applications. By both theoretical calculations and experiments, ssDNA nanorobots were demonstrated to be stable, flexible, highly utilized with low folding errors. Thereafter, ssDNA nanorobots were successfully applied to logical dual-recognition targeting, efficient and cancer-selective internalization, visual dual-detection of miRNAs, selective siRNA delivery and synergistic gene silencing. This work has provided a computational pathway for constructing flexible and multifunctional ssDNA frameworks, enlarging biological application of nucleic acid nanostructures

TEMED Enhanced Photoluminescent Imaging Detection of Proteins in Human Serum Using Quantum Dots after PAGE

In this paper, the development of a novel enhanced photoluminescent (PL) imaging method for human serum proteins detection after polyacrylamide gel electrophoresis (PAGE) is described. Thioglycolic acid (TGA)-capped CdTe QDs and enhanced reagent tetramethylethylenediamine (TEMED) have been introduced, resulting in direct detection of various proteins in native polyacrylamide gels and expanded application scope to SDS gels. Some relatively low-abundance proteins such as Zinc-α2-glycoprotein (ZAG) and α2-HS-glycoprotein (α2-HSG) are easily detected by TEMED enhanced PL imaging and identified by MS and MS/MS techniques. In the present study, the PL imaging conditions such as QDs concentration, alkali concentration, and enhanced reagents are optimized and the possible mechanisms are analyzed. The sensitivity of TEMED enhanced PL imaging is satisfying, with a linear range of 11.7−375 ng for ferritin, comparing with 46.9−375 ng in CBB-R250 staining and 23.4−375 ng in direct PL imaging. As a novel PL imaging detection method that is simple, fast, and sensitive, it shows great analytical potential in proteome research and in biochemistry

Single-Molecule Evaluation of the SARS-CoV‑2 Nucleocapsid Protein Using Gold Particle-in-a-Frame Nanostructures Enhanced Fluorescent Assay

Ultrasensitive evaluation of low-abundance analytes, particularly with limits approaching a single molecule, is a key challenge in the design of an assay for profiling severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen. Herein, we report an aptamer claw strategy for directly evaluating the SARS-CoV-2 antigen based on gold particle-in-a-frame nanostructures (Au PIAFs). Au PIAF was used as a metal-enhanced fluorescence material. The assay integrated with a microplate reader achieved a sensitivity of 44 fg·mL–1 in under 3 min and accurately detected the SARS-CoV-2 nucleocapsid protein (N protein) in human saliva samples. When our assay is combined with a single-molecule counting platform, the limit of detection can be as low as 0.84 ag·mL–1. This rapid and ultrasensitive assay holds promise as a tool for screening SARS-CoV-2 and other contagious viruses

Development of a Plasma-Assisted Cataluminescence System for Benzene, Toluene, Ethylbenzene, and Xylenes Analysis

A novel method has been proposed to enhance efficiency of cataluminescence reaction by applying a plasma-assisted cataluminescence (PA-CTL) system. The obtained results clearly indicated that the PA-CTL system exhibited substantially higher sensitivity for the detection of benzene, toluene, ethylbenzene, and xylenes (BTEX) on the surface of nanosized ZrO2. There are two distinctive advantages in the PA-CTL system; on one hand, the plasma activates the BTEX molecules for the detection, and on the other hand, the working temperature range of the catalytic reaction is lowered with the plasma assistance. A detection limit (LOD = 3σ) of 20 ng mL−1 was achieved for benzene in air samples. Using a graphite electrode in the designed plasma provides an additional opportunity for solid-phase microextraction (SPME) sampling of volatile organic compounds (VOCs) on its surface followed by PA-CTL detection. This ability has been investigated for detection of m-xylene in air samples

Venturi-Electrosonic Spray Ionization Cataluminescence Sensor Array for Saccharides Detection

In this article, a Venturi electrosonic spray ionization (V-ESSI) cataluminescence (CTL) sensor array was reported for discriminating saccharides in solution. Integrating electrosonic spray ionization (ESSI), a liquid system of Venturi self-pumping injection for the CTL reaction, was fabricated for enhancing CTL reactivity of aqueous samples. Comparing with simple Venturi injection by air and Venturi easy ambient sonic-spray ionization without electric assistance (V-EASI), the remarkable enhancement of CTL signals resulted from V-ESSI. This system showed higher cross-reactive CTL responses catalyzed by alkaline earth metal-nanomaterials than other catalysts, giving different signals for a given saccharide on different catalysts and different responses for different saccharides on the same catalyst. Then, a 4 × 2 CTL sensor array was used for obtaining “fingerprints” of distinct CTL response patterns. Analyzed by linear discriminant analysis (LDA), this V-ESSI CTL sensor array not only achieved the well discrimination of different saccharides (99.9% of total variation) but also discriminated four groups of urine sugar-level for urine samples from diabetic patients (98.1% of discrimination accuracy). It had good reproducibility and gave a linear range of 22.5–67558 μg/mL (R > 0.99) for xylose with a detection limit of 7.4 μg/mL on MgO. As a new artificial tongue, this system provided a simple, rapid, low cost, low energy consumption, and environmentally friendly pathway for aqueous sample discrimination. It has dramatically expanded applications of the CTL-based senor array and will be applicable to clinical diagnoses, environment monitoring, industrial controls, food industry, and various marine monitoring

Near-Infrared-Fluorescent Probes for Bioapplications Based on Silica-Coated Gold Nanobipyramids with Distance-Dependent Plasmon-Enhanced Fluorescence

Optical antennas with anisotropic metal nanostructures are widely used in the field of fluorescence enhancement based on localized surface plasmons (LSPs). They overcome the intrinsic defects of low brightness of near-infrared (NIR) dyes and can be used to develop sensitive NIR sensors for bioapplications. Here, we demonstrate a novel NIR plasmon-enhanced fluorescence (PEF) system consisting of elongated gold nanobipyramids (Au NBPs) antennas, silica, and NIR dyes. Silica was chosen as the rigid spacer to regulate the distance between the metal nanostructures and dyes. Maximum enhancement was observed at a distance of approximately 17 nm. The enhanced fluorescence could be quenched by Cu2+ and recovered by pyrophosphate (PPi) owing to the strong affinity between PPi and Cu2+. Thus, the Au NBP@SiO2@Cy7 nanoparticles (NPs) detect PPi via “switch-on” fluorescence signals, with a detection limit of 80 nM in the aqueous phase. The probe not only detects PPi in living cells but also can be used for a microRNA assay with a detection limit of 8.4 pM by detecting PPi in rolling circle amplification (RCA). Additionally, gold nanorods (Au NRs) with the same longitudinal plasmon resonance wavelength (LPRW) as the Au NBPs were prepared to synthesize Au NR@SiO2@Cy7 NPs for comparison. The experimental and finite-different time-domain (FDTD) simulation results indicate that the stronger electric fields of Au NBPs contribute to a fluorescence enhancement that is several times higher than that of Au NRs, confirming the superior properties of Au NBPs as novel ideal substrates to develop PEF biosensors

In Situ H₂O Meter by Visualization in Hydrogels

The solvent content strongly affects the viscoelastic properties and network structure of hydrogels. Because of the gels’ structural susceptibility and autofluorescence background, there is still no visual method to evaluate the water content in micropores. Herein, a colorimetric molecular probe (DHBYD) was synthesized for in situ visualization of water content in the micropores of hydrogels. The rapid and reversible colorimetric responses of DHBYD to solvents were obtained, which resulted a full linearity range (0 to 100%) for detecting water content in real time. Demonstrated by theoretical calculations, the sensing was attributed to changes in intramolecular charge transfer via deprotonation of phenol group. A cubic polynomial, on correlation of RGB values with water content, was established for real detection of water content in hydrogels. It reveals a new pathway for simple, in situ, and full-range evaluation of solvent content in micropores of hydrogels without any complicated procedures or expensive instruments. This would achieve fast and in situ monitoring of hydrogels to improve gel properties for better applications. It can be extended to evaluate the solvent content in other fields such as synthesis and industrial applications