Photocontrolled Thermosensitive Electrochemiluminescence Hydrogel for Isocarbophos Detection

Application of photothermal effects of nanomaterials in food safety detection

Numerous nanomaterials endowed with outstanding light harvesting and photothermal conversion abilities have been extensively applied in various fields, such as photothermal diagnosis and therapy, trace substance detection, and optical imaging. Although photothermal detection methods have been established utilizing the photothermal effect of nanomaterials in recent years, there is a scarcity of reviews regarding their application in food safety detection. Herein, the recent advancements in the photothermal conversion mechanism, photothermal conversion efficiency calculation, and preparation method of photothermal nanomaterials were reviewed. In particular, the application of photothermal nanomaterials in various food hazard analyses and the newly established photothermal detection methods were comprehensively discussed. Moreover, the development and promising future trends of photothermal nanomaterial-based detection methods were discussed, which provide a reference for researchers to propose more effective, sensitive, and accurate detection methods.

LuMA-Functionalized Thermosensitive Hydrogel: A Versatile and Robust Dopamine-Triggered Platform for Diverse Biomolecules Sensing

It is of great significance for the analysis of multiple biomarkers because a single biomarker is difficult to accurately achieve early diagnosis, disease course monitoring, and prognosis evaluation. Herein, a luminescence thermosensitive hydrogel was synthesized by radical polymerization using a methacrylic acid derivative monomer of luminol (LuMA) as luminescent, N-isopropylacrylamide (NIPAM) as thermosensitive monomer, and acrydite-oligonucleotides [dopamine (DA) aptamer, DNA C1, and DNA C2] as recognition elements. The combined DA based on the affinity interaction between the DA and the aptamer on the hydrogel polymer chain was electrochemically oxidized to dopamine quinone during the electrochemiluminescence (ECL) scanning, which effectively quenched the ECL signal of LuMA due to the resonance energy transfer (RET). In addition, the thermosensitive hydrogel showed swelling-collapse characteristics when the temperature was below and above the volume phase transition temperature. Undergoing the collapse process initiated by the temperature, the RET efficiency was further enhanced due to the shortened distance between the energy donor and acceptor, showing a 1.4 times signal amplification and achieving sensitive detection of DA with a limit of detection (LOD) of 1.7 × 10-10 M. For a proof of concept application, coupled with the target-induced release of DA from the DNA-magnetic beads bioconjugations based on duplex-specific nuclease (DSN)-assisted target recycling amplification strategy and DNAzyme cleavage reaction, this ECL-RET approach was successfully used to evaluate multiple targets including miRNA-141 and MUC1 with the LOD of 2.5 aM and 1.6 fg/mL, respectively. The excellent performances of the versatile and robust ECL-RET hydrogel in multiple target sensing showed potential applications in clinical diagnosis and disease therapeutic assay.

Screening-Capture-Integrated Electrochemiluminescent Aptasensor Based on Mesoporous Silica Nanochannels for the Ultrasensitive Detection of Deoxynivalenol in Wheat

To prevent the contamination of cereals by mycotoxins, establishing a sensitive and rapid method for the detection of mycotoxins is essential. In this study, a screening-capture-integrated electrochemiluminescence (ECL) aptasensor based on mesoporous silica films (MSFs) was successfully prepared for the ultrasensitive and highly selective detection of deoxynivalenol (DON) in wheat. The narrow nanochannels of MSFs can realize size screening, thereby eliminating the influence of macromolecular substances and providing a pure environment for the signal probe (tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)32+)) to reach the indium tin oxide (ITO) conductive substrate, which significantly improves the anti-interference ability of the screening-capture-integrated ECL sensor. The aptamer (Apt) attached to the surface of the MSFs can specifically capture DON, and the resulting DON-Apt complex has a gated effect on the MSFs, triggering the inhibition of Ru(bpy)32+ in the electrolyte from reaching the ITO surface. Therefore, the ECL intensity of the sensor decreased with increasing DON concentration to achieve a quantitative detection of DON. Under optimized conditions, the linear range of the screening-capture-integrated ECL aptasensor was 0.001-200 μg/kg, and the detection limit was as low as 5.27 × 10-5 μg/kg (S/N = 3). In conclusion, this study developed a screening-capture-integrated ECL aptasensor that combines size screening and specific capture for the detection of DON in wheat, providing a new approach for the early detection of wheat mildew.

Hydrogen Bond Organic Frameworks as Radical Reactors for Enhancement in ECL Efficiency and Their Ultrasensitive Biosensing

Nowadays, electrochemiluminescence (ECL) efficiency of an organic emitter is closely related with its potential applications in food safety and environmental monitoring fields. In this work, 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (TATB) was self-assembled to form hydrogen bond organic frameworks (HOFs), which worked as ideal reactors to generate highly active oxygen-containing radicals, followed by linking with isoluminol (ILu) via amide bond (termed ILu-HOFs). After covalent assembly with aminated indium-tin oxide electrode (labeled NH₂-ITO), the ECL efficiency of the ILu-HOFs NH₂-ITO showed about a 23.4-time increase over that of ILu itself in the presence of H₂O₂. Meanwhile, the enhanced ECL mechanism was mainly studied by electron paramagnetic resonance, theoretical calculation, and electrochemistry. On the above foundation, an aptamer "sandwich" ECL biosensor was constructed for detecting isocarbophos (ICP) via in situ elimination of H₂O₂ with catalase-linked palladium nanocubes (CAT-Pd NCs). The as-built sensor showed a broad linear range (1 pM to 100 nM) and a low limit of detection (LOD) down to 0.4 pM, coupled with efficient assays of ICP in lake water and cucumber juice samples. This strategy provides an effective way for the synthesis of advanced ECL emitter, coupled by showing promising applications in environmental and food analysis.

Plasmon-Enhanced Electrochemiluminescence at the Single-Nanoparticle Level

Plasmon-enhanced electrochemiluminescence (ECL) at the single-nanoparticle (NP) level was investigated by ECL microscopy. The Au NPs were assembled into an ordered array, providing a high-throughput platform that can easily locate each NP in sequential characterizations. A strong dependence of ECL intensity on Au NP configurations was observed. We demonstrate for the first time that at the single-particle level, the ECL of Ru(bpy)₃ ²⁺ -TPrA was majorly quenched by small Au NPs (<40 nm), while enhanced by large Au ones (>80 nm) due to the localized surface plasmon resonance (LSPR). Notably, the ECL intensity was further increased by the coupling effect of neighboring Au NPs. Finite Difference Time Domain (FDTD) simulations conformed well with the experimental results. This plasmon enhanced ECL microscopy for arrayed single NPs provides a reliable tool for screening electrocatalytic activity at a single particle.

A Trilaminar-Thermosensitive Hydrogel Catalytic Reactor Capable of Single/Tandem Catalytic Switchable Ability

The present endeavor is to develop a highly-intelligent catalytic reactor prototype which is able to autonomously adapt to the environment and provides an in-situ double-shift catalytic ability. By seeking inspiration from nature, this objective is achieved by developing a self-adaptive hydrogel catalytic reactor which held a catalytic trilaminar structure capable of reverse thermosensitive properties. With increasing temperatures, the catalytic tri-layers of this catalytic reactor would function in a sequential way (i.e., one negative temperature response layer, one support layer and one positive temperature response layer) and as a result, led to the single-tandem double-shift catalytic ability. This catalytic reactor individually presented single/tandem catalytic process at relatively low temperatures or high temperatures through the cooperative work of the three layers. In this way, this catalytic reactor showed the single-tandem controllable catalytic ability. The novel protocol not only provides a new solution to complicated catalytic processes but also inspires the further application of smart polymers in a broader spectrum of areas.

SERS- and absorbance-based catalytic assay for determination of isocarbophos using aptamer-modified FeMOF nanozyme and in situ generated silver nanoparticles

A new Fe metal-organic framework-loaded liquid crystal 4-octoxybenzoic acid (FeMOF@OCTB) nanosol was synthesized using 1,3,5-phthalic acid, ferrous sulfate, and OCTB as precursors. The FeMOF@OCTB exhibits good stability and strong catalytic effect for the polyethylene glycol 400-Ag (I) indicator reaction, which was evaluated rapidly by the slope procedure. The generated silver nanoparticles have a strong surface-enhanced Raman scattering (SERS) effect and a surface plasmon resonance absorption (Abs) peak at 420 nm. This new bimodal nanosilver indicator reaction was coupled with the isocarbophos (IPS)-aptamer (Apt) reaction. A FeMOF@OCTB nanocatalytic amplified-SERS/Abs bimodal Apt assay for IPS was established. The SERS assay can detect IPS in the concentration range 0.02-1.2 nM, with a detection limit of 0.010 nM. It has been applied to the determination of IPS in rice samples. The relative standard deviation was 4.4-5.8%, and the recovery was 97.7-104%. An Ag nanosol plasmon SERS/Abs dimode aptamer assay was fabricated for trace isocarbophos, based on highly catalysis MOF@OCTB nanoenzyme.

Self-enhanced luminol-based electrochemiluminescent hydrogels: An ultrasensitive biosensing platform for fusion gene analysis coupled with target-initiated DNAzyme motor

BCR/ABL fusion gene has been discovered as an important and reliable biomarker for early diagnosis of chronic myeloid leukemia (CML). Herein, a novel and switching electrochemiluminescence (ECL) biosensor was developed for ultrasensitive determination of the fusion gene based on the self-enhanced polyethyleneimine-luminol (PEI-Lum) hydrogels coupled with target-initiated DNAzyme motor. The facilely prepared PEI-Lum hydrogels could not only immobilize enormous luminol but shorten the distance of binary system, thus facilitating the mass and electron transfer efficiency of the sensing interface, so that the enhanced ECL signal was achieved. Moreover, the engineering DNA motor was powered by Mg²⁺-dependent DNAzyme for isothermal DNA signal amplification. As a result, the fabricated ECL biosensor enabled highly sensitive detection of BCR/ABL fusion gene with a broad linear range from 10.0 fM to 10.0 nM and a low detection limit of 3.75 fM (S/N = 3). Significantly, the developed biosensing method provides a potential tool for nucleic acid analysis in clinical diagnosis and a new avenue to design high-efficient ECL nanomaterials.

A novel electrochemiluminescence aptasensor based on copper-gold bimetallic nanoparticles and its applications

In this work, a novel electrochemiluminescence (ECL) aptasensor was structured for the detection of four organophosphorus pesticides (OPs). Firstly, multi-walled carbon nanotubes (MWCNTs) were used to create a favorable loading interface for the fixation of tris (2, 2'-bipyridyl) ruthenium (II) (Ru (bpy)₃²⁺). At the same time, copper (core)-gold (shell) bimetallic nanoparticles (Cu@Au NPs) were synthesized in the aqueous phase for the sensor construction. Gold nanoparticles (Au NPs) could promote the electrochemiluminescence intensity of Ru (bpy)₃²⁺ with high efficiency by catalyzing the oxidation process of tri-n-propylamine (TPrA). Compared with the Au NPs, Cu@Au NPs increased the solid loading of Au NPs by virtue of the large specific surface area of copper nanoparticles (Cu NPs), which could further improve the sensitivity of aptasensor. When OPs were added, the ECL intensity was significantly reduced, and the concentration of OPs could be detected through the ECL intensity. Under the optimum conditions, the aptasensor had a wider dynamic range and ultra-low detection limit for the detection of four pesticides: profenofos, isocarbophos, phorate, and omethoate, and their detection limits were 3 × 10^-4 ng/mL, 3 × 10^-4 ng/mL, 3 × 10^-3 ng/mL, and 3 × 10^-2 ng/mL respectively (S/N = 3). The aptasensor had the merits of good stability, reproducibility, and specificity, and had a favorable recovery rate in detecting OPs residues in vegetables. This work provided an effective method for the construction of a simple, rapid, and sensitive biosensor.

Photothermal-Induced Electrochemical Interfacial Region Regulation Enables Signal Amplification for Dual-Mode Detection of Ovarian Cancer Biomarkers

Detection sensitivity of an electrochemical immunosensor mainly depends on the accessible distance toward the sensing interface; regulating the electrochemical interfacial region thereon is an effective strategy for signal amplification. Herein, a photothermal-regulated sensing interface was designed based on a near-infrared (NIR)-responsive hydrogel probe for ultrasensitive detection of human epididymis protein 4 (HE4). Silver nanoparticle-deposited graphene oxide nanosheet (AgNPs@GO) hybrids as electrochemical signal tags and a photothermal transducer, which were encapsulated in the poly(N-isopropylacrylamide) (pNIPAM) hydrogel, were used to develop the NIR-responsive GO@AgNPs-pNIPAM hydrogel probe. Under NIR light irradiation, the excellent photothermal effect of AgNPs@GO hybrids not only rapidly converted NIR light into heat for temperature readout but also triggered the shrinkage behavior of the hydrogel for electrochemical signal amplification. Compared with the conventional sandwich immunoassay, the shrinkage behavior of the hydrogel signal probe endowed itself with interface regulation capability to improve the electrochemical reaction efficiency; on the basis of ensuring the extended outer Helmholtz plane (OHP) region, the proposed photothermal-induced interface regulation also shortened the OHP, leading to higher sensitivity. Moreover, the obtained dual-mode signals provided satisfactory accuracy for the detection of tumor markers. Therefore, this detection scheme provided an opportunity for the broad applications of the photothermal effect in clinical diagnosis.

Electrochemiluminescence aptasensor for Siglec-5 detection based on MoS2@Au nanocomposites emitter and exonuclease III-powered DNA walker

Lectins are highly specific binding proteins for glycoproteins which widely exist in living organisms, playing a vital role in exploring the biological evolution process, such as cellular proliferation, differentiation, carcinogenesis and apoptosis. Therefore, the content monitoring of lectin becomes particularly significant and urgent in the bioanalytical application. In this work, we fabricated an aptasensor, majorly capitalizing the eminent affinity between sialic acid-binding immunoglobulin (Ig)-like lectin 5 (Siglec-5) and nucleic acids aptamer (K19), with nontoxic MoS₂@Au nanocomposites as electrochemiluminescence (ECL) emitters based on exonuclease III (Exo III)-powered DNA walker for the bioassays of Siglec-5. The DNA track was constructed on the emitters' surface, providing a reliable platform for the DNA walker's autonomous move. In the assay, the primer DNA in the DNA duplex was replaced by Siglec-5 due to the aptamer interactions and repeatedly released to participate in the movement of the DNA walker, further triggering cascade signal amplification. Finally, our aptasensor indicates significant potential for assays of Siglec-5 with a detection limit of 8.9 pM.

Spatially-resolved dual-potential sandwich electrochemiluminescence immunosensor for the simultaneous determination of carbohydrate antigen 19-9 and carbohydrate antigen 24-2

A new electrochemiluminescence (ECL) immunosensor based on spatially-resolved dual-potential technology was designed for the simultaneous determination of carbohydrate antigen 19-9 (CA 19-9) and carbohydrate antigen 24-2 (CA 242). Luminol-AgNPs@ZIF-67 was used as the anodic probe, and Pt nanoparticle-functionalized graphitic carbon nitride nanosheets (g-C₃N₄@PtNPs) were used as the cathodic probe. Two spatially-resolved areas on the dual-disk glassy carbon electrode (DDGCE) were modified with a AuNPs film by electrodeposition to improve the conductivity of the sensing interface. By recording the ECL responses at two different excitation potentials, the linear range for CA 19-9 was determined to be 0.0001-10 U/mL, with a limit of detection of 31 μU/mL. The linear range for CA 242 was 0.0005-10 U/mL, with a limit of detection of 0.16 mU/mL. Moreover, the ECL immunosensor possessed high selectivity and stability and successfully detected CA 19-9 and CA 242 in real samples. This immunosensor provides a new platform for clinical immunoassays.

A potential-resolved electrochemiluminescence resonance energy transfer strategy for the simultaneous detection of neuron-specific enolase and the cytokeratin 19 fragment

An electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor was developed based on the potential-resolved technology for the simultaneous detection of neuron-specific enolase (NSE) and the cytokeratin 19 fragment (CYFRA21-1). The absorption spectrum of gold nanorods (AuNRs) perfectly overlapped with the ECL spectra of SnS2@Pt and Ru(bpy)32+/Zn-MOF, so they exhibited an excellent ECL-RET effect with high efficiency. Zn-MOF possesses a large surface area, which allows for the loading of Ru(bpy)32+. This results in a signal probe of Ru(bpy)32+/Zn-MOF/Ab1 showing a strong ECL emission. Simultaneously, owing to the excellent electronic conductivity of PtNPs, they can increase the electron transfer rate between S2O82- and tin disulfide nanoflowers (SnS2NFs). Hence, the ECL signal of SnS2NFs can be enhanced. Under the optimal conditions, the linear range for NSE is 0.2 pg mL-1-20 ng mL-1 with a detection limit of 79 fg mL-1. The linear range for CYFRA21-1 is 1.25 pg mL-1-12.5 ng mL-1 with a detection limit of 0.43 pg mL-1. The proposed immunosensor can be used for the sensitive simultaneous detection of NSE and CYFRA21-1 in human serum and has promise for clinical diagnostics.

Advances and trends of hydrogel therapy platform in localized tumor treatment: A review

Due to limitations of treatment and the stubbornness of infiltrative tumor cells, the outcome of conventional antitumor treatment is often compromised by a variety of factors, including severe side effects, unexpected recurrence, and massive tissue loss during the treatment. Hydrogel-based therapy is becoming a promising option of cancer treatment, because of its controllability, biocompatibility, high drug loading, prolonged drug release, and specific stimuli-sensitivity. Hydrogel-based therapy has good malleability and can reach some areas that cannot be easily touched by surgeons. Furthermore, hydrogel can be used not only as a carrier for tumor treatment agents, but also as a scaffold for tissue repair. In this review, we presented the latest researches in hydrogel applications of localized tumor therapy and highlighted the recent progress of hydrogel-based therapy in preventing postoperative tumor recurrence and improving tissue repair, thus proposing a new trend of hydrogel-based technology in localized tumor therapy. And this review aims to provide a novel reference and inspire thoughts for a more accurate and individualized cancer treatment.