Shape-Controlled Gold Nanoarchitectures: Synthesis, Superhydrophobicity, and Electrocatalytic Properties

A simple one-step electrodeposition method was used to fabricate various gold nanostructures on glassy carbon electrodes in a low concentration of HAuCl4 solution (5 mM). The morphologies of final gold nanostructures can be easily controlled by varying the pH of the precursors or the deposition temperature. X-ray powder diffraction, scanning electronic microscopy, transmission electron microscopy, contact angle measurements, and electrochemical methods were used to characterize them. Hierarchical waxberry-like gold nanostructures with high active surface areas were obtained in pH 4 bath, and they had a higher catalytic performance for the reduction of oxygen than the other nanogold. These gold structures also displayed an extraordinary superhydrophobicity and the contact angle increased with the increase of deposition temperature and time. Their electrocatalytic response to the oxidation of glucose was also investigated. A sensitive enzyme-free sensor can be easily developed for the detection of glucose in pH 7.4 phosphate buffer solution

Unveiling the Dynamic Electrocatalytic Activity of Online Synthesized Bimetallic Nanocatalysts via Electrochemiluminescence Microscopy

Effective bimetallic nanoelectrocatalysis demands precise control of composition, structure, and understanding catalytic mechanisms. To address these challenges, we employ a two-in-one approach, integrating online synthesis with real-time imaging of bimetallic Au@Metal core–shell nanoparticles (Au@M NPs) via electrochemiluminescence microscopy (ECLM). Within 120 s, online electrodeposition and in situ catalytic activity screening alternate. ECLM captures transient faradaic processes during potential switches, visualizes electrochemical processes in real-time, and tracks catalytic activity dynamics at the single-particle level. Analysis using ECL photon flux density eliminates size effects and yields quantitative electrocatalytic activity results. Notably, a nonlinear activity trend corresponding to the shell metal to Au surface atomic ratio is discerned, quantifying the optimal surface component ratio of Au@M NPs. This approach offers a comprehensive understanding of catalytic behavior during the deposition process with high spatiotemporal resolution, which is crucial for tailoring efficient bimetallic nanocatalysts for diverse applications

Electrochemiluminescence Ratiometry: A New Approach to DNA Biosensing

Inspired by dual-wavelength fluorescence ratiometric method which could reduce the influence from the environmental change, here, we present a novel dual-potential electrochemiluminescence (ECL) ratiometric sensing approach. CdS nanocrystal (NC) and luminol as two different ECL emitters are employed. ECL from CdS NCs coated on glassy carbon electrode at −1.25 V (vs SCE) could be quenched by closely contacted Pt nanoparticles (NPs) via a biological binding event, while ECL from luminol at +0.45 V (vs SCE) could be enhanced by the same Pt NPs, in the presence of their common coreactant of H₂O₂. Thus, the quenching of ECL from CdS NCs and the enhancement of ECL from luminol could indicate the same biological binding event. With the mp53 oncogene as a model DNA molecule, a molecular beacon (MB) containing a 20-base loop, which is complementary with the mp53 oncogene, is immobilized on CdS NCs/GCE first; Pt NPs are then captured on CdS NCs surface by DNA hybridization between the MB and mp53 oncogene labeled on Pt NPs. By measuring the ratio of ECL intensities at two excitation potentials, this approach could sensitively detect the concentration of target DNA in a wide range from 5.0 fM to 1.0 pM. The sensing scheme is general and can be utilized for many other biological binding events

Efficient quenching of electrochemiluminescence from K-doped graphene-CdS:Eu NCs by G-quadruplex-hemin and target recycling-assisted amplification for ultrasensitive DNA biosensing

Based on the K-doped graphene-CdS:Eu NC composites and the nicking endonuclease (NEase) assisted strand-scission cycle, we have developed an ultrasensitive and selective electrochemiluminescence (ECL) DNA biosensor using the G-quadruplex-hemin-based DNAzyme which acts as an electrocatalyst for the reduction of H(2)O(2), the coreactant of CdS:Eu NCs ECL

Flexible gold electrode array for multiplexed immunoelectrochemical measurement of three protein biomarkers for prostate cancer

In this work, we report a simple and novel electrochemical multiplexed immunosensor on a flexible polydimethylsiloxane (PDMS) slice deposited with 8 × 8 nano-Au film electrodes for simultaneous detection of prostate specific antigen (PSA), prostate specific membrane antigen (PSMA), and interleukin-6 (IL-6). Primary antibodies linked with magnetic beads (Ab1-MBs) were modified on the nano-Au film electrodes via magnetic force. In the presence of corresponding antigen, horse radish peroxidase-secondary antibody-conjugated gold nanorods (HRP-Ab2-gold NRs) were brought into the surface of electrodes, generating obvious electrochemical signals of H2O2 reduction reactions. Based on this, the designed immunosensor provide good performance in sensitivity and specificity during the detection of above three biomarkers for prostate cancer. The electrochemical multiplexed immunosensor was verified for selective and accurate detection of complex samples in human serum. Data suggested that the reported multiplexed immunosensing strategy holds great promise for applications in clinical assay and diseases diagnosis

Selective Detection of Hypertoxic Organophosphates Pesticides via PDMS Composite based Acetylcholinesterase-Inhibition Biosensor

We report on a pair of highly sensitive amperometric biosensors for organophosphate pesticides (OPs) based on assembling acetylcholinesterase (AChE) on poly(dimethylsiloxane) (PDMS)−poly(diallydimethylammonium) (PDDA)/gold nanoparticles (AuNPs) composite film. Two AChE immobilization strategies are proposed based on the composite film with hydrophobic and hydrophilic surface tailored by oxygen plasma. The twin biosensors show interesting different electrochemical performances. The hydrophobic surface based PDMS-PDDA/AuNPs/choline oxidase (ChO)/AChE biosensor (biosensor-1) shows excellent stability and unique selectivity to hypertoxic organophosphate. At optimal conditions, this biosensor-1 could measure 5.0 × 10−10 g/L paraoxon and 1.0 × 10−9 g/L parathion. As for the hydrophilic surface based biosensor (biosensor-2), it shows no selectivity but can be commonly used for the detection of most OPs. Based on the structure of AChE, it is assumed that via the hydrophobic interaction between enzyme molecules and hydrophobic surface, the enzyme active sites surrounded by hydrophobic amino acids face toward the surface and get better protection from OPs. This assumption may explain the different performances of the twin biosensors and especially the unique selectivity of biosensor-1 to hypertoxic OPs. Real sample detection was performed and the omethoate residue on Cottomrose Hibiscus leaves was detected with biosensor-1

In Situ Visualization of hERG Potassium Channel via Dual Signal Amplification

Dysfunction of the human ether-a-go-go related gene (hERG)-encoded potassium channel is identified as a major cause of the long QT syndrome, a marker for lethal cardiac arrhythmia. Furthermore, recent studies revealed that hERG K+ channel is a regulator of tumor cell apoptosis and proliferation. Herein, an ultrasensitive fluorescence assay combining DNA-functionalized gold nanoparticles and rolling circle amplification (RCA) was attempted for the first time to visualize hERG channels in living cells. The spherical nucleic acid gold nanoparticles, which can anchor on hERG channels in the cell membrane, not only act as the primary amplification elements but also trigger the subsequent RCA reaction to achieve the secondary amplification. Within 30 min, the ratio of reporter to target can reach up to 104, realizing the detection of hERG channels in cells with low-level expression. Therefore, the strategy provides a valuable tool for hERG-related studies. More importantly, it opens a new horizon for imaging various membrane proteins which possess specific aptamers or antibodies

Thermal/Plasma-Driven Reversible Wettability Switching of a Bare Gold Film on a Poly(dimethylsiloxane) Surface by Electroless Plating

We report an approach for fabricating a tunable wettability surface by electroless gold plating on poly(dimethylsiloxane) (PDMS). A two-layer structured gold film with a tight layer and a loose layer can be obtained on the surface of a PDMS chip when the PDMS chip is immersed in a gold plating solution at 30 °C for 4 h. Its wettability can be rapidly switched between superhydrophilicity and superhydrophobicity by plasma and heat treatments without any self-assembled monolayer, and the superhydrophobicity can be even changed from the gecko-foot-hair-like character to the lotus-leaf-like character. Benefiting from the various wettabilities of the prepared gold/PDMS composites, protein patterning is successfully achieved on a patterned superhydrophobic/superhydrophilic gold/PDMS composite; a superhydrophobic needle for transferring supersmall water droplets (1 μL) to a superhydrophobic surface is successfully fabricated

Metallic Inverse Opals: An Electrochemiluminescence enhanced Substrate for Sensitive Bioanalysis

Here, we proposed a novel local surface plasmon resonance (LSPR) enhanced ECL strategy based on the metallic inverse opals and Ru­(bpy)32+-doped silica nanoparticles (RuSi NPs). Gold inverse opals (GIOs), as a plasmonic array, could interact with the ECL of RuSi NPs and excite the electromagnetic (EM) field at the gold surface. The triggered EM field could enhance the ECL emission of RuSi NPs. We compared the electrochemical and ECL performances of RuSi NPs modified on the gold electrodes with different surface morphologies and found that the ECL emission of RuSi NPs patterned at the inner surface of GIOs exhibited the highest intensity. The finite-difference time-domain (FDTD) simulations indicated that the EM field was related to the surface morphology of the metallic nanostructure, and the highest EM field was observed at the inner surface of the GIOs. Because of the superior ECL performances, the inner surfaces of GIOs were developed for nucleic acid detection with a detection limit of 3.3 fM (S/N = 3), which shows great promise for bioanalysis

Tumor-Marker-Mediated “on-Demand” Drug Release and Real-Time Monitoring System Based on Multifunctional Mesoporous Silica Nanoparticles

“On-demand” drug release can maximize therapeutic efficacy for specific states of malignancies and minimize drug toxicity to healthy cells. Meanwhile, there is lack of a real-time monitoring platform to accurately investigate the amount of anticancer drugs released, especially nonfluorescent ones. So it is significant to integrate both issues in one ideal drug delivery system. To achieve this, here we present a novel stimuli-responsive controlled drug delivery system toward the tumor marker survivin mRNA, using a real-time monitoring approach based on the fluorescence resonance energy transfer (FRET) strategy to quantify the process of drug release. First, 7-amino-4-methlcoumarin (AMCA) dye terminated short oligonucleotide (Flare_A) will hybridize with fluorescein isothiocyanate (FITC) labeled long oligonucleotide (S1_F), which contains a recognition element to a specific RNA transcript, to form a FRET pair capped on the pores of mesoporous silica nanoparticles (MSNs). Following a target-recognition reaction, the target with a longer strand displaces the Flare_A strand to form a longer and more stable duplex with S1_F, which leads to the removal of the capped oligonucleotide from the MSNs and triggers the release of the entrapped cargo while FRET between AMCA and FITC is broken. The relevant change in donor and acceptor fluorescence signal can be used to monitor the unlocking and release event in real-time. Further investigations have also demonstrated that this release system possesses the capacity of modulating the extent of drug release according to the cell states, giving the platform an equally broad spectrum of applications in anticancer therapy