Electrochemiluminescence quenching of luminol by CuS in situ grown on reduced graphene oxide for detection of N-terminal pro-brain natriuretic peptide

Exploring T7 RNA polymerase-assisted CRISPR/Cas13a amplification for the detection of BNP via electrochemiluminescence sensing platform

Brain natriuretic peptide (BNP) is considered to be an important biomarker of heart failure (HF) attracting attention. However, its low concentration and short half-life in blood lead to a low-sensitivity detection of BNP, which is a challenge that has to be overcome. In this work, we propose a highly specific, highly sensitive T7 RNA polymerase-assisted clustered regularly interspaced short palindromic repeats (CRISPR)/Cas13a system to detect BNP via an electrochemiluminescence (ECL) sensing platform and incorporate exonuclease III (Exo III)-hairpin and dumbbell-shaped hybridization chain reaction (HCR) technologies. In this detection scheme, the ECL sensing platform possesses low background signal and high sensitivity. Firstly, the T7 promoter-initiated T7 RNA polymerase acts as a signal amplification technique to generate large amounts of RNAs that can activate CRISPR/Cas13a activity. Secondly, CRISPR/Cas13a is able to trans-cleave the surrounding trigger strand to produce DNA1. Thirdly, DNA1 is involved in the co-amplification reaction of Exo III and hairpin DNA, which subsequently triggers a dumbbell-shaped HCR technology. Eventually, a large number of Ru (II) molecules are inserted into the interstitial space of the dumbbell-shaped HCR to generate a strong ECL signal. The CRISPR/Cas13a possesses outstanding specificity for a single base and increased sensitivity. The tightly conformed dumbbell-shaped HCR provides higher sensitivity than the traditional linear HCR amplification technique. Ultimately, the clever combination of several amplification reactions enables the limit of detection (LOD) as low as 3.2 fg/mL. It showed promise for clinical sample testing, with recovery rates ranging from 98.4% to 103% in 5% human serum samples. This detection method offered a valuable tool for early HF detection, emphasizing the synergy of amplification strategies and specificity conferred by CRISPR/Cas13a technology.

Advanced Nanomaterial-Based Biosensors for N-Terminal Pro-Brain Natriuretic Peptide Biomarker Detection: Progress and Future Challenges in Cardiovascular Disease Diagnostics

Cardiovascular diseases (CVDs) represent a significant challenge in global health, demanding advancements in diagnostic modalities. This review delineates the progressive and restrictive facets of nanomaterial-based biosensors in the context of detecting N-terminal pro-B-type natriuretic peptide (NT-proBNP), an indispensable biomarker for CVD prognosis. It scrutinizes the escalation in diagnostic sensitivity and specificity attributable to the incorporation of novel nanomaterials such as graphene derivatives, quantum dots, and metallic nanoparticles, and how these enhancements contribute to reducing detection thresholds and augmenting diagnostic fidelity in heart failure (HF). Despite these technological strides, the review articulates pivotal challenges impeding the clinical translation of these biosensors, including the attainment of clinical-grade sensitivity, the substantial costs associated with synthesizing and functionalizing nanomaterials, and their pragmatic deployment across varied healthcare settings. The necessity for intensified research into the synthesis and functionalization of nanomaterials, strategies to economize production, and amelioration of biosensor durability and ease of use is accentuated. Regulatory hurdles in clinical integration are also contemplated. In summation, the review accentuates the transformative potential of nanomaterial-based biosensors in HF diagnostics and emphasizes critical avenues of research requisite to surmount current impediments and harness the full spectrum of these avant-garde diagnostic instruments.

Biosensors for natriuretic peptides in cardiovascular diseases. A review

Heart failure (HF) is a complex clinical syndrome associated with high rates of morbidity and mortality. Over the years, it has been crucial to find accurate biomarkers capable of doing a precise monitor of HF and provide an early diagnosis. Of these, it has been established an important role of natriuretic peptides in HF assessment. Moreover, the development of biosensors has been garnering interest as new diagnostic medical tools. In this review we first provide a general overview of HF, its pathogenesis, and diagnostic features. We then discuss the role of natriuretic peptides in heart failure by characterizing them and point out their potential as biomarkers. Finally, we adress the evolution of biosensors development and the available natriuretic peptides biosensors for disease monitoring.

An electrochemiluminescence resonance energy transfer biosensor based on Luminol-LDH and CuS@Pt for detection of alpha-fetoprotein

Alpha-fetoprotein (AFP) is the best diagnostic marker for hepatocellular carcinoma (HCC) and plays an important role in the general surveillance of the population. Therefore, the establishment of an ultra-sensitive AFP assay is essential for the early screening and clinical diagnosis of HCC. In this work, we designed a signal-off biosensor for ultra-sensitive detection of AFP based on an electrochemiluminescent resonance energy transfer (ECL-RET) strategy using luminol intercalated layered bimetallic hydroxide (Luminol-LDH) as an ECL donor and Pt nanoparticles-grown on copper sulfide nanospheres (CuS@Pt) as ECL acceptor. The (Au NPs/Luminol-LDH)_n multilayer nanomembrane synthesized by our intercalation and layer-by-layer electrostatic assembly process not only effectively immobilizes luminol but also significantly enhances the ECL signal. The CuS@Pt composite has well visible light absorption ability and can burst the light emitted from luminol by ECL-RET. The biosensor showed good linearity in the range from 10^-5 ng mL^-1 to 100 ng mL^-1 and a minimum detection limit of 2.6 fg mL^-1. Therefore, the biosensor provides a novel and efficient strategy for the detection of AFP, which is important for the early screening and clinical diagnosis of HCC.

A sensitive dual-signal electrochemiluminescence immunosensor based on Ru(bpy)32+@HKUST-1 and Ce2Sn2O7 for detecting the heart failure biomarker NT-proBNP

A sensitive dual-signal electrochemiluminescence (ECL) immunosensor was proposed based on Ru(bpy)₃²⁺@HKUST-1/TPA and Ce₂Sn₂O₇/K₂S₂O₈ probes for detecting the NT-proBNP biomarker of heart failure. HKUST-1 with a high specific surface area facilitates the loading of more Ru(bpy)₃²⁺, effectively improving the anodic signal intensity, while the emerging Ce₂Sn₂O₇ emitter displays a potential-matching cathodic emission with moderate intensity. Two ECL probes were characterized with field emission scanning electron microscopy, X-ray diffraction, XPS, FT-IR spectroscopy and UV-Vis diffuse reflectance spectroscopy. This dual-signal immunosensor has a wide linear range (5 × 10^-4-1 × 10⁴ ng mL^-1) and a low quantitative detection limit, simultaneously showing high sensitivity, stability and reproducibility, as well as the detection capability of actual serum samples. This dual signal-calibrated immunoassay platform not only reduces the false positive rate of detection results but also provides a promising method for the early diagnosis of heart failure.

Green syntheses of graphene and its applications in internet of things (IoT)-a status review

Internet of Things (IoT) is a trending technological field that converts any physical object into a communicable smarter one by converging the physical world with the digital world. This innovative technology connects the device to the internet and provides a platform to collect real-time data, cloud storage, and analyze the collected data to trigger smart actions from a remote location via remote notifications, etc. Because of its wide-ranging applications, this technology can be integrated into almost all the industries. Another trending field with tremendous opportunities is Nanotechnology, which provides many benefits in several areas of life, and helps to improve many technological and industrial sectors. So, integration of IoT and Nanotechnology can bring about the very important field of Internet of Nanothings (IoNT), which can re-shape the communication industry. For that, data (collected from trillions of nanosensors, connected to billions of devices) would be the 'ultimate truth', which could be generated from highly efficient nanosensors, fabricated from various novel nanomaterials, one of which is graphene, the so-called 'wonder material' of the 21st century. Therefore, graphene-assisted IoT/IoNT platforms may revolutionize the communication technologies around the globe. In this article, a status review of the smart applications of graphene in the IoT sector is presented. Firstly, various green synthesis of graphene for sustainable development is elucidated, followed by its applications in various nanosensors, detectors, actuators, memory, and nano-communication devices. Also, the future market prospects are discussed to converge various emerging concepts like machine learning, fog/edge computing, artificial intelligence, big data, and blockchain, with the graphene-assisted IoT field to bring about the concept of 'all-round connectivity in every sphere possible'.

Electroanalytical point-of-care detection of gold standard and emerging cardiac biomarkers for stratification and monitoring in intensive care medicine - a review

Determination of specific cardiac biomarkers (CBs) during the diagnosis and management of adverse cardiovascular events such as acute myocardial infarction (AMI) has become commonplace in emergency department (ED), cardiology and many other ward settings. Cardiac troponins (cTnT and cTnI) and natriuretic peptides (BNP and NT-pro-BNP) are the preferred biomarkers in clinical practice for the diagnostic workup of AMI, acute coronary syndrome (ACS) and other types of myocardial ischaemia and heart failure (HF), while the roles and possible clinical applications of several other potential biomarkers continue to be evaluated and are the subject of several comprehensive reviews. The requirement for rapid, repeated testing of a small number of CBs in ED and cardiology patients has led to the development of point-of-care (PoC) technology to circumvent the need for remote and lengthy testing procedures in the hospital pathology laboratories. Electroanalytical sensing platforms have the potential to meet these requirements. This review aims firstly to reflect on the potential benefits of rapid CB testing in critically ill patients, a very distinct cohort of patients with deranged baseline levels of CBs. We summarise their source and clinical relevance and are the first to report the required analytical ranges for such technology to be of value in this patient cohort. Secondly, we review the current electrochemical approaches, including its sub-variants such as photoelectrochemical and electrochemiluminescence, for the determination  of important CBs highlighting the various strategies used, namely the use of micro- and nanomaterials, to maximise the sensitivities and selectivities of such approaches. Finally, we consider the challenges that must be overcome to allow for the commercialisation of this technology and transition into intensive care medicine.

A dual-quenched ECL immunosensor for ultrasensitive detection of retinol binding protein 4 based on luminol@AuPt/ZIF-67 and MnO2@CNTs

Background

Retinol binding protein 4 (RBP4) has been regarded as an important serological biomarker for type 2 diabetes mellitus (T2DM). Hence, the construction of a highly sensitive detection method for RBP4 is the key to early prevention and multidisciplinary intervention of T2DM. In this work, a dual-quenched electrochemiluminescence (ECL) immunosensor has been fabricated for ultrasensitive detection of RBP4 by combining zeolitic imidazolate framework-67/AuPt-supported luminol (luminol@AuPt/ZIF-67) with MnO₂ nanosheets-grown on carbon nanotubes (MnO₂@CNTs).

Results

AuPt/ZIF-67 hybrids with high-efficiency peroxidase-like activity could provide multipoint binding sites for luminol and antibodies and significantly boost the amplified initial signal of the ECL immunosensor. Upon glutathione/H₂O₂ coreactants system, MnO₂@CNTs composites could quench the initial signal by inhibiting mimic peroxidase activity of luminol@AuPt/ZIF-67. Moreover, the absorption spectrum of the MnO₂@CNTs composites completely overlaps with the emission spectrum of luminol, which can further reduce initial signal by ECL resonance energy transfer (ECL-RET).

Conclusions

Benefiting from the above-mentioned properties, the designed immunoassay sensitivity exhibited excellent sensitivity and relative stability for RBP4 detection range from 0.0001 to 100 ng mL⁻¹ with a low detection limit of 43 fg mL⁻¹. Therefore, our ECL immunosensor provides an alternative assaying strategy for early diagnosis of T2DM.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01020-1.

A label-free and signal-on electrochemiluminescence strategy for sensitive amyloid-beta assay

Development of a simple, cost-effective and sensitive biosensing strategy is highly desirable to advance the applications in Alzheimer's disease diagnosis. In this paper, we present a simple, label-free and signal-on electrochemiluminescence (ECL) aptasensor for the detection of amyloid-beta (Aβ) peptide using luminol as ECL emitter and in-situ generated reactive oxygen species (ROS) as coreactant via catalytic reaction between Cu²⁺-Aβ and the dissolved O₂ in the presence of ascorbic acid (AA). Aβ₁₆, the binding site of Cu²⁺ in the monomeric full-length Aβ, was used as a model in present study. As a result, this signal-on ECL aptasensor has exhibited favorable analytical performance for Aβ₁₆ monomer with a linear range of 1.0 × 10^-13 mol/L-1.0 × 10^-8 mol/L and a limit of detection of 3.5 × 10^-14 mol/L (S/N=3). Furthermore, the proposed biosensor was also able to detect the full length Aβ₄₀ not only in the phosphate buffer saline (PBS) solution but also in human serum. The presented biosensor represents a promising, simple, turn-on and label-free diagnostic tool for blood analysis.

Engineering of CdTe/SiO2 nanocomposites: Enhanced signal amplification and biocompatibility for electrochemiluminescent immunoassay of alpha-fetoprotein

Electrochemiluminescent (ECL) performance and cytotoxicity of CdTe quantum dots (QDs)-based nanocomposites and its possible application for ECL immunoassay were investigated. Two types of CdTe-based nanocomposites, i.e., SiO₂-coated CdTe (CdTe@SiO₂) and CdTe-functionalized SiO₂ (SiO₂@CdTe), were synthesized and comprehensively compared in regarding of the cytotoxicity and ECL performance. The in vitro cytotoxicity of SiO₂@CdTe and CdTe@SiO₂ nanoparticles was assessed in L02 cells using standard CCK-8 assay, and their ECL performance was investigated by constructing sandwiched immunosensor using SiO₂@CdTe and CdTe@SiO₂ as tags for the labelled antibody, respectively. The results showed that CdTe@SiO₂ exhibited much lower cytotoxicity and a higher ECL intensity than SiO₂@CdTe. Taking the analysis of alpha-fetoprotein (AFP) as an example, the ECL immunosensor using CdTe@SiO₂ as an emitter was proved to have a wide linear dynamic range from 1.0 pg mL^-1 to 100 ng mL^-1 with a low detection limit of 0.22 pg mL^-1 (S/N ratio of 3). The ECL immunosensor also demonstrated satisfactory recovery and excellent reproducibility and stability, indicating that this method has prospects in practical application in the clinical diagnosis of AFP.

Sensitivity enhancement of cloth-based closed bipolar electrochemiluminescence glucose sensor via electrode decoration with chitosan/multi-walled carbon nanotubes/graphene quantum dots-gold nanoparticles

In this work, a novel facile closed bipolar electrochemiluminescence (C-BP-ECL) sensor has been developed for highly sensitive detection of glucose based on the integration of chitosan (CS), poly(diallyldimethylammonium chloride)-functioned multi-walled carbon nanotubes (PDDA-MWCNTs) and graphene quantum dots-gold nanoparticles (GQDs-AuNPs) on the wax/carbon ink-screen-printed cloth-based device. When CS, PDDA-MWCNTs and GQDs-AuNPs are successively decorated onto the cathode of closed bipolar electrode (C-BPE), the C-BPE anode can emit much stronger C-BP-ECL signals. Moreover, the cathodic decoration of the C-BPE can generate a stronger ECL signal in comparison with its anodic decoration. Under optimized conditions, glucose can be detected in the range of 0.1-5000 μM, and the limit of detection is estimated to be 64 nM, which is about three orders of magnitude lower than that in case of the bare C-BPE cathode (31 μM). It has been shown that the proposed sensor has high detection sensitivity, wide dynamic range, and as well acceptable reproducibility, selectivity and stability. Finally, the applicability and validity of the C-BP-ECL sensor are demonstrated for the detection of glucose in human serum samples. We believe that this novel highly-sensitive sensor will have potential applications in various areas such as clinical diagnosis, food analysis and environmental monitoring.