CdZnTeS quantum dots based electrochemiluminescent image immunoanalysis

Sulfur vacancy defects mediated CdZnTeS@BC heterojunction: Artificial intelligence-assisted self-enhanced electrochemiluminescence molecularly imprinted sensing of CTC

Environmental pollution caused by tetracycline antibiotics is a major concern of global public health. Here, a novel and portable molecularly imprinted electrochemiluminescence (MIECL) sensor based on smartphones for highly sensitive detection of chlortetracycline (CTC) has been successfully established. The high-performance ECL emitter of biomass carbon (BC) encapsulated CdZnTeS (CdZnTeS@BC) was successfully synthesized by hydrothermal. The enhanced ECL performance was ascribed to the introduction of the BC and increased the overall electrical conductivity of the nanoemitter, as well as increased the number of sulfur vacancies and doping on the surface of the emitter based on density functional theory calculations. An aniline-CTC molecular imprinted polymer was synthesized on the surface of the CdZnTeS@BC modified electrode by in-situ electropolymerization. The decrease in MIECL signal was attributed to the increase in impedance effect. The MIECL nanoplatform enabled a wide linear relationship in the range of 0.05-100 μmol/L with a detection limit of 0.029 μmol/L for spectrometer sensors. Interestingly, the light emitted during the MIECL reaction can be captured by a smartphone. Thus, machine learning was used to screen the photos that were taken, and color analysis was carried out on the screened photos by self-developed software, thus achieving a portable, convenient, and intelligent sensing mode. Finally, the sensor obtains satisfactory results in the detection of actual samples, with no significant differences from those of liquid chromatography.

Optical nanomaterial-based detection of biomarkers in liquid biopsy

Liquid biopsy, which is a minimally invasive procedure as an alternative to tissue biopsy, has been introduced as a new diagnostic/prognostic measure. By screening disease-related markers from the blood or other biofluids, it promises early diagnosis, timely prognostication, and effective treatment of the diseases. However, there will be a long way until its realization due to its conceptual and practical challenges. The biomarkers detected by liquid biopsy, such as circulating tumor cell (CTC) and circulating tumor DNA (ctDNA), are extraordinarily rare and often obscured by an abundance of normal cellular components, necessitating ultra-sensitive and accurate detection methods for the advancement of liquid biopsy techniques. Optical biosensors based on nanomaterials open an important opportunity in liquid biopsy because of their enhanced sensing performance with simple and practical properties. In this review article, we summarized recent innovations in optical nanomaterials to demonstrate the sensitive detection of protein, peptide, ctDNA, miRNA, exosome, and CTCs. Each study prepares the optical nanomaterials with a tailored design to enhance the sensing performance and to meet the requirements of each biomarker. The unique optical characteristics of metallic nanoparticles (NPs), quantum dots, upconversion NPs, silica NPs, polymeric NPs, and carbon nanomaterials are exploited for sensitive detection mechanisms. These recent advances in liquid biopsy using optical nanomaterials give us an opportunity to overcome challenging issues and provide a resource for understanding the unknown characteristics of the biomarkers as well as the mechanism of the disease.

Functionalized nanomaterials-based electrochemiluminescent biosensors and their application in cancer biomarkers detection

To detect a range of trace biomarkers associated with human diseases, researchers have been focusing on developing biosensors that possess high sensitivity and specificity. Electrochemiluminescence (ECL) biosensors have emerged as a prominent research tool in recent years, owing to their potential superiority in low background signal, high sensitivity, straightforward instrumentation, and ease of operation. Functional nanomaterials (FNMs) exhibit distinct advantages in optimizing electrical conductivity, increasing reaction rate, and expanding specific surface area due to their small size effect, quantum size effect, and surface and interface effects, which can significantly improve the stability, reproducibility, and sensitivity of the biosensors. Thereby, various nanomaterials (NMs) with excellent properties have been developed to construct efficient ECL biosensors. This review provides a detailed summary and discussion of FNMs-based ECL biosensors and their applications in cancer biomarkers detection.

Electrochemiluminescence of Semiconductor Quantum Dots and Its Biosensing Applications: A Comprehensive Review

Electrochemiluminescence (ECL) is the chemiluminescence triggered by electrochemical reactions. Due to the unique excitation mode and inherent low background, ECL has been a powerful analytical technique to be widely used in biosensing and imaging. As an emerging ECL luminophore, semiconductor quantum dots (QDs) have apparent advantages over traditional molecular luminophores in terms of luminescence efficiency and signal modulation ability. Therefore, the development of an efficient ECL system with QDs as luminophores is of great significance to improve the sensitivity and detection flux of ECL biosensors. In this review, we give a comprehensive summary of recent advances in ECL using semiconductor QDs as luminophores. The luminescence process and ECL mechanism of semiconductor QDs with various coreactants are discussed first. Specifically, the influence of surface defects on ECL performance of semiconductor QDs is emphasized and several typical ECL enhancement strategies are summarized. Then, the applications of semiconductor QDs in ECL biosensing are overviewed, including immunoassay, nucleic acid analysis and the detection of small molecules. Finally, the challenges and prospects of semiconductor QDs as ECL luminophores in biosensing are featured.

High electrochemical active Au-NP/2D zinc-metal organic frameworks heterostructure-based ECL sensor for the miRNA-522 detection in triple negative breast cancer

In this work, a novel electrochemiluminescence (ECL) sensor has been developed to detect the miRNA-522 in the tumor tissues of triple-negative breast cancer (TNBC) patients. Au NPs/Zn MOF heterostructure was obtained by in situ growth and used as novel luminescence probe. Firstly, zinc-metal organic framework nanosheets (Zn MOF NSs) were synthesized with Zn²⁺ as the central metal ion and 2-aminoterephthalic acid (NH₂-BDC) as the ligand. 2D MOF nanosheets with ultra-thin layered structure and relatively large specific surface areas can enhance the catalytic activity in the ECL generation. Furthermore, the electron transfer capacity and the electrochemical active surface area of MOF were greatly improved by the growth of Au NPs. Therefore, Au NPs/Zn MOF heterostructure showed the significant electrochemical activity in the sensing process. In addition, the magnetic Fe₃O₄@SiO₂@Au microspheres were used as capture units in the magnetic separation step. The magnetic spheres with hairpin aptamer H1 can capture target gene. Then the captured miRNA-522 triggered the target catalyzed hairpin assembly (CHA) sensing process and linked Au NPs/Zn MOF heterostructure. The concentration of miRNA-522 can be quantified by the ECL signal enhancement of the Au NPs/Zn MOF heterostructure. Due to the high catalytic activity of Au NPs/Zn MOF heterostructure and their unique structural and electrochemical properties, the prepared ECL sensor achieved high-sensitive detection of miRNA-522 in the range of 1 fM to 0.1 nM with the detection limit of 0.3 fM. This strategy can provide a potential alternative for miRNA detection in medical research and clinical diagnosis of triple negative breast cancer.

Lead Monoxide Nanostructures for Nanophotonics: A Review

Black-phosphorus-analog lead monoxide (PbO), as a new emerging 2D material, has rapidly gained popularity in recent years due to its unique optical and electronic properties. Recently, both theoretical prediction and experimental confirmation have revealed that PbO exhibits excellent semiconductor properties, including a tunable bandgap, high carrier mobility, and excellent photoresponse performance, which is undoubtedly of great interest to explore its practical application in a variety of fields, especially in nanophotonics. In this minireview, we firstly summarize the synthesis of PbO nanostructures with different dimensionalities, then highlight the recent progress in the optoelectronics/photonics applications based on PbO nanostructures, and present some personal insights on the current challenges and future opportunities in this research area. It is anticipated that this minireview can pave the way to fundamental research on functional black-phosphorus-analog PbO-nanostructure-based devices to meet the growing demands for next-generation systems.

Electrochemiluminescence nanoemitters for immunoassay of protein biomarkers

The family of electrochemiluminescent luminophores has witnessed quick development since the electrochemiluminescence (ECL) phenomenon of silicon nanoparticles was first reported in 2002. Moreover, these developed ECL nanoemitters have extensively been applied in sensitive detection of protein biomarker by combining with immunological recognition. This review firstly summarized the origin and development of various ECL nanoemitters including inorganic and organic nanomaterials, with an emphasis on metal-organic frameworks (MOFs)-based ECL nanoemitters. Several effective strategies to amplify the ECL response of nanoemitters and improve the sensitivity of immunosensing were discussed. The application of ECL nanoemitters in immunoassay of protein biomarkers for diagnosis of cancers and other diseases, especially lung cancer and heart diseases, was comprehensively presented. The recent development of ECL imaging with the nanoemitters as ECL tags for detection of multiplex protein biomarkers on single cell membrane also attracted attention. Finally, the future opportunities and challenges in the ECL biosensing field were highlighted.

Preparation of an electrochemical immunosensor based on a Cu/Cu2O-rGO@Au signal synergistic amplification strategy and efficient and sensitive detection of alpha-fetoprotein

The effective amplification of the signal is the prerequisite for the ultrasensitive detection of electrochemical immunosensors. To quantitatively detect alpha-fetoprotein (AFP), we prepared a sandwich-type electrochemical immunosensor. Using a gold nanoparticles (Au NPs) modified glassy carbon electrode (GCE) as the sensing platform and Cu/Cu₂O-rGO@Au as the signal label, differential pulse voltammetry (DPV) was used to achieve sensitive detection of AFP. We found that the nanomaterials can undergo electro-oxidation and electro-reduction reactions between Cu(I) and Cu(II) in a buffer solution of pH = 6.0. It is worth mentioning that the incorporation of metals into metal oxide substrates is a new strategy to combine the catalytic activity of metal oxides with the electrical conductivity of metals. Reduced graphene oxide (rGO), which is rich in oxygen-containing groups, can load more Cu/Cu₂O and Au NPs and increase the conductivity. The modification of Au NPs makes them have better biocompatibility and conductivity. Under the best detection conditions, the prepared immunosensor realizes the specific and ultrasensitive detection of AFP. The detection range is 0.01-50 ng mL^-1 and the limit of detection (LOD) was as low as 0.589 pg mL^-1 (S/N = 3); meanwhile it also has good practical application ability. Therefore, this immunosensor provides an important means for the early screening and detection of AFP.

In situ growth of WO3/BiVO4 nanoflowers onto cellulose fibers to construct photoelectrochemical/colorimetric lab-on-paper devices for the ultrasensitive detection of AFP

In this work, novel dual-mode lab-on-paper devices based on in situ grown WO₃/BiVO₄ heterojunctions onto cellulose fibers, as signal amplification probes, were successfully fabricated by the integration of photoelectrochemical (PEC)/colorimetric analysis technologies into a paper sensing platform for the ultrasensitive detection of alpha-fetoprotein (AFP). Specifically, to achieve an impressive PEC performance of the lab-on-paper device, the WO₃/BiVO₄ heterojunction was in situ grown onto the surface of cellulose fibers assisted with Au nanoparticle (Au NP) functionalization for enhancing the conductivity of the working zone of the device. With the target concentration increased, more immune conjugates could be captured by the proposed paper photoelectrode, which could lead to a quantitative decrease in the photocurrent intensity, eventually realizing the accurate PEC signal readout. To meet the requirement of end-user application, a colorimetric signal readout system was designed for the lab-on-paper device based on the color reaction of 3,3'5,5'-tetramethylbenzidine (TMB) oxidized by WO₃/BiVO₄ nanoflowers in the presence of H₂O₂. Noticeably, it is the first time that the WO₃/BiVO₄ heterojunction is in situ grown onto cellulose fibers, which enhances the sensitivity in view of both their PEC activity and catalytic ability. By controlling the conversion process of hydrophobicity and hydrophilicity on the lab-on-paper device combined with diverse origami methods, the dual-mode PEC/colorimetric signal output for the ultrasensitive AFP detection was realized. Under optimal conditions, the proposed dual-mode lab-on-paper device could enable the sensitive PEC/colorimetric diagnosis of AFP in the linear range of 0.09-100 ng mL^-1 and 5-100 ng mL^-1 with the limit of detection of 0.03 and 1.47 ng mL^-1, respectively.

Enhanced electrochemiluminescence of CdS quantum dots capped with mercaptopropionic acid activated by EDC for Zika virus detection

Enhanced electrochemiluminescence (ECL) signals of CdS quantum dots capped with 3-mercaptopropionic acid (MPA@CdS QDs) have been observed after using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) to activate the carboxyl groups. The generated ECL signals are strong enough that their images can be captured using a Huawei mobile phone. A possible mechanism for the generation of enhanced ECL signals has been proposed. Then, a sandwich immunosensor platform for detecting Zika virus (ZIKV) was fabricated with silica microspheres as the carrier and MPA@CdS QDs as ECL signal labels. Due to the dual signal amplification of EDC activation and microsphere enrichment, good linearity from 1.0 fg mL-1 to 1.0 ng mL-1 was exhibited by the QD-based ECL immunosensor for ZIKV detection. The detection limit was 0.3 fg mL-1.

Continuous preparation of antimony nanocrystals with near infrared photothermal property by pulsed laser ablation in liquids

Antimony nanocrystals (Sb NCs) are of interest in energy storage, catalysis and cancer therapy for its special physical, chemical and biomedical properties. However, methodology challenges still remain in preparation of colloidal Sb NCs, due to the restricted reaction solution systems, high temperature and time costing for common routes. Herein, size controllable colloidal Sb NCs were continuously prepared by pulsed laser ablation of Sb target in different solvents, owning to the metal nanodroplet explosive ejection and thermal evaporation mechanisms. These well dispersed and stable Sb NCs showed excellent photothermal property in the near-infrared-II window.

Recent developments in electrochemiluminescence nanosensors for cancer diagnosis applications

In recent years, electrochemiluminescence (ECL) nanosensing systems have undergone rapid development and made significant progress in ultrasensitive analysis and cell imaging. Because of the unique advantages of high selectivity, ultra-sensitivity, and good reproducibility, ECL nanosensors can open new paths for cancer diagnosis. With the development of ECL nanosensors, high-throughput analysis, visual detection and spatially resolved ECL imaging of single cells are being realized. The innovations of ECL nanosensors consist of electrochemical excitation, coreactant catalysis, light radiation and luminescence signal amplification, which involve several fields such as nanotechnology, catalysis, optics, and electrochemistry. The developments of ECL instruments also relate to imaging technology. Herein, we review the construction modes, sensing strategies and cancer diagnosis applications of ECL nanosenors. Firstly, the nano-components of the ECL sensing system are discussed. The construction and signal amplification methods of the nanosensing system are emphasized. Secondly, the high-efficiency cancer identification strategies are presented, including protein tumor marker detection, nucleic acid assay, cancer cell identification and exosome detection. The recent advances in representative examples of ECL nanosenors in cancer diagnosis are highlighted, including high-throughput ECL analysis, in situ assay, visual ECL detection, single-cell imaging diagnosis, and so on. Finally, the challenges are featured based on the recent development of the ECL nanosensing system in the clinical diagnosis. The ECL nanosensors provide effective and reliable analytical methods and open new paths for cancer diagnosis. It is noteworthy that the prospects of the ECL nanosensing system in clinical diagnosis are instructive to the developments of other nanosensor research.

Electrochemiluminescence Detection of Sunset Yellow by Graphene Quantum Dots

Use of food additives, such as colorants and preservatives, is highly regulated because of their potential health risks to humans. Therefore, it is important to detect these compounds effectively to ensure conformance with industrial standards and to mitigate risk. In this paper, we describe the preparation and performance of an ultrasensitive electrochemiluminescence (ECL) sensor for detecting a key food additive, sunset yellow. The sensor uses graphene quantum dots (GQDs) as the luminescent agent and potassium persulfate as the co-reactant. Strong and sensitive ECL signals are generated in response to trace amounts of added sunset yellow. A detection limit (signal-to-noise ratio = 3) of 7.6 nM and a wide linear range from 2.5 nM to 25 μM are demonstrated. A further advantage of the method is that the luminescent reagents can be recycled, indicating that the method is sustainable, in addition to being simple and highly sensitive.

Electrochemical Sensing of α-Fetoprotein Based on Molecularly Imprinted Polymerized Ionic Liquid Film on a Gold Nanoparticle Modified Electrode Surface

A molecularly imprinted sensor was fabricated for alpha-fetoprotein (AFP) using an ionic liquid as a functional monomer. Ionic liquid possesses many excellent characteristics which can improve the sensing performances of the imprinted electrochemical sensor. To demonstrate this purpose, 1-[3-(N-cystamine)propyl]-3-vinylimidazolium tetrafluoroborate ionic liquid [(Cys)VIMBF₄] was synthesized and used as a functional monomer to fabricate an AFP imprinted polymerized ionic liquid film on a gold nanoparticle modified glassy carbon electrode (GCE) surface at room temperature. After removing the AFP template, a molecularly imprinted electrochemical sensor was successfully prepared. The molecularly imprinted sensor exhibits excellent selectivity towards AFP, and can be used for sensitive determination of AFP. Under the optimized conditions, the imprinted sensor shows a good linear response to AFP in the concentration range of 0.03 ng mL⁻¹~5 ng mL⁻¹. The detection limit is estimated to be 2 pg mL⁻¹.

Dual-signal-amplified electrochemiluminescence biosensor for microRNA detection by coupling cyclic enzyme with CdTe QDs aggregate as luminophor

In this work, a dual-signal-amplified electrochemiluminescence (ECL) biosensor was proposed for the first time to detect microRNAs (miRNAs) based on cyclic enzyme and seeded-watermelon-like mesoporous nanospheres (mSiO₂@CdTe@SiO₂, mSQS NSs). mSQS NSs were successfully fabricated by inlaying the CdTe quantum dots (QDs) into the mesoporous silica (mSiO₂) and future coating the surface with the silica layer. The obtained mSQS NSs contained tens of QDs and exhibited much stronger ECL signal than single QDs. The ECL biosensor achieved firstly signal amplification by using mSQS NSs to label the functional oligonucleotide probe (DNA-F) as enhanced ECL signal probes. Well-dispersed Fe₃O₄@Au nanoparticles were prepared as immobilization matrices to load hairpin-structured DNA probe (DNA-P). When the target miRNAs were present, hairpin DNA undertook conformation changes. Meanwhile, RNA/DNA duplexes was formed which cleaved by duplex-specific nuclease (DSN) to release miRNAs. Target miRNAs were cycled to hybridize with hairpin DNA, which achieved secondly signal amplification of the ECL biosensor. Thereafter, the complementarily parts between DNA-F and the rest DNA-P generated conjugates. The obtained conjugates would be collected on the surface of the electrode by effecting of magnet. Under the optimal conditions, the developed biosensor showed a wide linear range from 0.1 pM to 100 pM with a low detection limit of 33 fM (S/N = 3). The results of detection for the stability, specificity and reproducibility of ECL biosensor were outstanding. Simultaneously, the potential application of ECL biosensor was verified by using biosensor in serum sample.

Rapid Detection of Severe Fever with Thrombocytopenia Syndrome Virus via Colloidal Gold Immunochromatography Assay

To develop the point-of-care testing method to facilitate the clinical detection of severe fever with thrombocytopenia syndrome virus (SFTSV), colloidal gold paper-based lateral flow immunochromatography test strips (LFITSs) have been fabricated for the rapid detection for the first time. The pH value and the amount of monoclonal antibody to prepare colloidal gold nanoparticle-labeled monoclonal antibody bioconjugates were optimized. In addition, 0.4% bovine serum albumin was considered to be the best concentration for blocking nitrocellulose membranes. Under optimal conditions, the limit of detection for SFTSV was as low as 1 ng/mL depending on a visual line. Meanwhile, the entire detection process required no more than 10 min with a volume of only 50 μL of the analyte solution. Moreover, paper-based LFITSs were evaluated in real samples of human serum of patients with satisfactory results. In addition, all strips were of high stability and specificity. In the light of advantages such as simple, portable, rapid, and low cost, the developed LFITSs will extensively come into service, especially in remote areas.