Recent Progress in Plasmonic based Electrochemiluminescence Biosensors: A Review

Dual emitting aggregation-induced electrochemiluminescence from tetrastyrene derivative for chloramphenicol detection

Chloramphenicol (CAP) poses a threat to human health due to its toxicity and bioaccumulation, and it is very important to measure it accurately and sensitively. This work explored a host-guest recognition strategy to mediate dual aggregation-induced electrochemiluminescence (AIECL) of 1,1,2,2-tetrakis(4-(pyridin-4-yl) phenyl)-ethene (TPPE) for ratio detection of CAP, in which, cucurbit[8]uril (CB[8]) served as host to assemble guest TPPE. The resulting supramolecular complex CB[8]-TPPE exhibited excellent dual-AIECL-emission with signal strength approximately four times that of TPPE aggregates and black hole quencher-1 (BHQ1) could efficiently quench dual-AIECL signal. CB[8]-TPPE coupled dual-function quencher BHQ1 and high-efficiency DNA reactor to achieve ultra-sensitive detection of CAP, exhibiting a linearity range of 10 fmol·L-1-100 nmol·L-1 and limit of detection of 1.81 fmol·L-1. CB[8]-TPPE provides a novel way to improve the dual-emission of TPE derivatives and sets up a promising platform for CAP detection, demonstrating a good practical application potential.

Electrochemiluminescence Reveals the Structure-Catalytic Activity Relationship of Heteroatom-Doped Carbon-Based Materials

Heteroatom doping can change the chemical environment of carbon-based nanomaterials and improve their catalytic performance. Exploring the structure-catalytic activity relationship of heteroatom-doped carbon-based materials is of great significance for studying catalytic mechanisms and designing highly efficient catalysts, but remains a significant challenge. Recently, reactive oxygen species (ROS)-triggered electrochemiluminescence (ECL) has shown great potential for unveiling the mechanism by which heteroatom-doped carbon-based materials catalyze the oxygen reduction reaction (ORR), owing to the high sensitivity of these materials to the properties of the electrode surface. Herein, two kinds of heteroatom-doped porous carbon (denoted as NP-C and N-C) are synthesized and analyzed by monitoring the cathodic ECL of luminol-H2O2 in the low negative-potential region. P, N-doped NP-C exhibits better catalytic ability for activating H2O2 to generate large amounts of •OH and O2 •-, compared with N-C. A sensitive antioxidant-mediated ECL platform is successfully developed for detecting the antioxidant levels in cells, exhibiting considerable potential for evaluating the antioxidant capacity. The relationship between the structure and catalytic mechanism of heteroatom-doped carbon-based materials is successfully explored using ECL, where this method can be universally applied to carbon-based materials.

Bright luminol electrochemiluminescence mediated by a simple TEMPO radical for visualized multiplex detection

In this work, a series of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) radicals bearing different functional groups were exploited as a simple catalyst to promote electrochemiluminescence (ECL) generation in luminol/H2O2 system. These TEMPO radicals were found to facilitate the electrochemical oxidation of H2O2 and luminol through different catalytic mechanisms, as well as the subsequent ECL generation of luminol/H2O2 system. The electrochemical oxidation and luminol ECL generation could be tuned by the functional group on the para-position of TEMPO, for which the structure/activity relationship was revealed. Finally, with the combination of enzymatic system, luminol ECL enhancement up to 9.6-fold was obtained through the catalysis of 4-hydroxyl-TEMPO. The enhanced luminol ECL allows acquiring brighter ECL images in a single-electrochemical system (SEES) for multiplex detection of cholesterol, H2O2 and glucose.

Dual "on-off" signal conversion strategy based on surface plasmon coupling and resonance energy transfer for visual electrochemiluminescence ratiometric analysis of MiRNA-141

An electrochemiluminescence (ECL) biosensor with a pair of new ECL emitters and a novel sensing mechanism was designed for the high-sensitivity detection of microRNA-141 (miRNA-141). Sulfur-doped boron nitrogen quantum dots (S-BN QDs) were initially employed to modify the cathode of the bipolar electrode (BPE), while the anode reservoir was [Ir(dfppy)2(bpy)]PF6/TPrA system. The next step involved attaching H1-bound ultra-small WO3-x nanodots (WO3-x NDs) to the S-BN QDs-modified BPE cathode via DNA hybridization. A strong surface plasmon coupling (SPC) effect was observed between S-BN QDs and WO3-x NDs, which allowed for the enhancement of the red and visible ECL emission from S-BN QDs. After target-induced cyclic amplification to produce abundant Zn2+ and Au NPs-DNA3-Au NPs (Au NPs-S3-Au NPs), Zn2+ could cleave DNA at a nucleotide sequence-specific recognition site to release the WO3-x NDs, resulting in the first diminution of cathode ECL signal and the first enhancement of anode ECL signal. Moreover, the ECL signal at cathode decreased for the second time and the emission of [Ir(dfppy)2(bpy)]PF6 was continuously enhanced after the introduction of Au nanoparticles-S3-Au nanoparticles on the cathode surface. Our sensing mode with a dual "on-off" signal conversion strategy shows a good detection capability for miRNAs ranging from 10-17 to 10-10 M, with a limit of detection (LOD) as low as 10-17 M, which has great application potential in biomedical research and clinical diagnosis.

Plasmonic silver and gold nanoparticles: shape- and structure-modulated plasmonic functionality for point-of-caring sensing, bio-imaging and medical therapy

Silver and gold nanoparticles have found extensive biomedical applications due to their strong localized surface plasmon resonance (LSPR) and intriguing plasmonic properties. This review article focuses on the correlation among particle geometry, plasmon properties and biomedical applications. It discusses how particle shape and size are tailored via controllable synthetic approaches, and how plasmonic properties are tuned by particle shape and size, which are embodied by nanospheres, nanorods, nanocubes, nanocages, nanostars and core-shell composites. This article summarizes the design strategies for the use of silver and gold nanoparticles in plasmon-enhanced fluorescence, surface-enhanced Raman scattering (SERS), electroluminescence, and photoelectrochemistry. It especially discusses how to use plasmonic nanoparticles to construct optical probes including colorimetric, SERS and plasmonic fluorescence probes (labels/reporters). It also demonstrates the employment of Ag and Au nanoparticles in polymer- and paper-based microfluidic devices for point-of-care testing (POCT). In addition, this article highlights how to utilize plasmonic nanoparticles for in vitro and in vivo bio-imaging based on SERS, fluorescence, photoacoustic and dark-field models. Finally, this article shows perspectives in plasmon-enhanced photothermal and photodynamic therapy.

Nitrogen-Doped Graphene Quantum Dots as Electrochemiluminescence-Emitting Species for Sensitive Detection of KRAS G12C Mutation via PET-RAFT

The levels of KRAS G12C point mutation is recognized to be closely related to the earlier diagnosis of non-small cell lung cancer (NSCLC). Here, based on nitrogen-doped graphene quantum dots (NGQDs) and photo-induced electron/energy transfer reversible addition-fragment chain transfer (PET-RAFT) signal amplification strategy, we fabricated a novel electrochemiluminescence (ECL) biosensor for the detection of KRAS G12C mutation for the first time. NGQDs as ECL-emitting species with cathodic ECL were prepared by a simple calcination method. Firstly, KRAS G12C mutation DNA, i. e., target DNA (tDNA), was captured by specific identification with hairpin DNA (hDNA). Then, PET-RAFT was initiated by blue light, and large numbers of monomers were successfully polymerized to form controllable polymer chains. Lastly, massive NGQDs was introduced via amidation reaction with N-(3-aminopropyl)methacrylamide hydrochloride (APMA), which significantly amplified the ECL signal intensity. Under optimal conditions, this biosensor achieved a good linear relationship between ECL intensity and logarithm of the levels of KRAS G12C mutation in the range from 10 fM to 10 nM. Moreover, this strategy exhibited high selectivity and excellent applicability for KRAS G12C mutation detection in the serum samples. Therefore, this biosensor has great potential in clinical diagnosis and practical application.

Molybdenum Disulfide as Tunable Electrochemical and Optical Biosensing Platforms for Cancer Biomarker Detection: A Review

Cancer is a common illness with a high mortality. Compared with traditional technologies, biomarker detection, with its low cost and simple operation, has a higher sensitivity and faster speed in the early screening and prognosis of cancer. Therefore, extensive research has focused on the development of biosensors and the construction of sensing interfaces. Molybdenum disulfide (MoS2) is a promising two-dimensional (2D) nanomaterial, whose unique adjustable bandgap shows excellent electronic and optical properties in the construction of biosensor interfaces. It not only has the advantages of a high catalytic activity and low manufacturing costs, but it can also further expand the application of hybrid structures through different functionalization, and it is widely used in various biosensors fields. Herein, we provide a detailed introduction to the structure and synthesis methods of MoS2, and explore the unique properties and advantages/disadvantages exhibited by different structures. Specifically, we focus on the excellent properties and application performance of MoS2 and its composite structures, and discuss the widespread application of MoS2 in cancer biomarkers detection from both electrochemical and optical dimensions. Additionally, with the cross development of emerging technologies, we have also expanded the application of other emerging sensors based on MoS2 for early cancer diagnosis. Finally, we summarized the challenges and prospects of MoS2 in the synthesis, functionalization of composite groups, and applications, and provided some insights into the potential applications of these emerging nanomaterials in a wider range of fields.

Enhanced Förster resonance energy transfer on layered metal-dielectric hyperbolic metamaterials: an excellent platform for low-threshold laser action

Förster resonance energy transfer (FRET) is a well-known physical phenomenon, which has been widely used in a variety of fields, spanning from chemistry, and physics to optoelectronic devices. In this study, giant enhanced FRET for donor-acceptor CdSe/ZnS quantum dot (QD) pairs placed on top of Au/MoO₃ multilayer hyperbolic metamaterials (HMMs) has been realized. An enhanced FRET transfer efficiency as high as 93% was achieved for the energy transfer from a blue-emitting QD to a red-emitting QD, greater than that of other QD-based FRET in previous studies. Experimental results show that the random laser action of the QD pairs is greatly increased on a hyperbolic metamaterial by the enhanced FRET effect. The lasing threshold with assistance of the FRET effect can be reduced by 33% for the mixed blue- and red-emitting as QDs compared to the pure red-emitting QDs. The underlying origins can be well understood based on the combination of several significant factors, including spectral overlap of donor emission and acceptor absorption, the formation of coherent closed loops due to multiple scatterings, an appropriate design of HMMs, and the enhanced FRET assisted by HMMs.