The self-powered electrochemical biosensing platform with multi-amplification strategy for ultrasensitive detection of microRNA-155

WS2 nanosheets-based electrochemical biosensor for highly sensitive detection of tumor marker miRNA-4484

In this paper, a few-layer WS2 nanosheets-based electrochemical biosensor was fabricated for the highly sensitive detection of breast cancer tumor marker miRNA-4484. Firstly, few-layer WS2 nanosheets were prepared by shear stripping and characterized by SEM, TEM, AFM and UV spectrophotometer. After modification of few-layer WS2 nanosheets on the electrode surface, the miRNA probe was fixed on the few-layer WS2 nanosheets by polycytosine (PolyC). Then short-chain miRNA containing PolyC was used as the blocking agent to close the excess active sites on the surface of WS2 nanosheets to complete the fabrication of the sensor biosensing interface. Finally, the current changes caused by the specific binding of miRNA-4484 to the probe were analyzed by differential pulse voltammetry (DPV). The results showed that the sensor had a good linear relationship for the detection of miRNA-4484 in the concentration range of 1 aM-100 fM, and the detection limit was as low as 1.61 aM. In addition, the electrochemical sensor had excellent selectivity, stability and reproducibility. The artificial sample tests indicated that the developed biosensors have the potential for clinical application in the future.

Cascade branch migration-triggered strand displacement amplification for specific and sensitive detection of microRNA

MicroRNAs (miRNAs) have been involved in many biological processes and are regarded as promising biomarkers. The short sequence, low abundance and highly homologous interference sequences greatly hinder the accurate detection of miRNAs. Here, a cascade branch migration-triggered strand displacement amplification (CBM-TSDA) strategy was developed for the first time for specific and sensitive detection of miRNA-155 (miR-155). In the presence of target miR-155, the CBM was initiated and two Y-shaped probes were eventually produced. Next, the Y-shaped probes were transformed into three-way junction (3WJ) structures and triggered the SDA to produce a large number of G-quadruplex (G4) structures. Finally, the increased fluorescence signal of G4/Thioflavin T (ThT) was used to quantify miR-155. Meanwhile, the colorimetric responses of the G4-hemin DNAzyme could be used as supplementary detection to obtain a dual-mode signal readout. This detection strategy showed high detection sensitivity, and the limit of detection was 0.28 pM in the fluorescence detection mode and 0.34 pM in the colorimetric detection mode. Notably, it showed high detection specificity, being able to discriminate the single-base mutations of the target with a high discrimination factor. The strategy also possessed excellent capacity for miR-155 detection in cell lysates and real human blood samples. The developed strategy provides a promising detection platform for miRNA, which may be applied to early clinical diagnosis.

Anti-aggregation colorimetric sensing of cysteine using silver nanoparticles in the presence of Pb2

Using silver nitrate as the silver source and sodium borohydride as the reducing agent, we synthesized negatively charged silver nanoparticles (AgNPs). Subsequently, the AgNPs solution was mixed with positively charged lead ions, resulting in AgNPs aggregation via electrostatic interactions. This led to a color change in the solution from yellow to purple and eventually to blue-green. Our study focused on a colorimetric method that exhibited high selectivity and sensitivity in detecting cysteine using AgNPs-Pb2+ as a sensing probe. Upon the introduction of cysteine to the AgNPs-Pb2+ system, the absorbance of AgNPs increased at 396 nm and decreased at 520 nm. The formation of a complex between cysteine and lead ions prevented the aggregation of silver nanoparticles, enabling the colorimetric detection of cysteine. The relationship between the concentration of ΔA396/A520 and cysteine showed linearity within the range of 0.01 to 0.1 μM; the regression equation of the calibration curve is ΔA396/A520 = 9.0005c - 0.0557 (c: μM), with an R2 value of 0.9997. The detection limit was found to be 3.8 nM (S/N = 3). This method demonstrated exceptional selectivity and sensitivity for cysteine and was effectively used for the determination of cysteine in urine. Our findings offer a new perspective for the future advancement of anti-aggregation silver nanocolorimetry.

Self-assembly of a AuNPs/Ti3C2 MXene hydrogel for cascade amplification of microRNA-122 biosensing

A three-dimensional (3D) self-assembled AuNPs/Ti3C2 MXene hydrogel (AuNPs/Ti3C2 MXH) nanocomposite was prepared for the fabrication of a novel microRNA-122 electrochemical biosensor. The 3D hydrogel structure was gelated from two-dimensional MXene nanosheets with the assistance of graphite oxide and ethylenediamine. MXene hydrogels supported the in situ formation of Au nanoparticles (AuNPs) that predominantly exploring the (111) facet, and these AuNPs are utilized as carriers for hairpin DNA (hpDNA) probes, facilitating DNA hybridization. MXene acted as both a reductant and stabilizer, significantly improving the electrochemical signal. In addition, the conjugation of PAMAM dendrimer-encapsulated AuNPs and H-DNA worked as an ideal bridge to connect targets and efficient electrochemical tags, providing a high amplification efficiency for the sensing of microRNA-122. A linear relationship between the peak currents and the logarithm of the concentrations of microRNA-122 from 1.0 × 10-2 to 1.0 × 102 fM (I = 1.642 + 0.312 lgc, R2 = 0.9891), is obtained. The detection limit is  0.8 × 10-2 fM (S/N = 3). The average recovery for human serum detection ranged from 97.32 to 101.4% (RSD < 5%).

Advancements in Bio-inspired Self-Powered Wireless Sensors: Materials, Mechanisms, and Biomedical Applications

The rapid maturation of smart city ecosystems is intimately linked to advances in the Internet of Things (IoT) and self-powered sensing technologies. Central to this evolution are battery-less sensors that are critical for applications such as continuous health monitoring through blood metabolites and vital signs, the recognition of human activity for behavioral analysis, and the operational enhancement of humanoid robots. The focus on biosensors that exploit the human body for energy-spanning wearable, attachable, and implantable variants has intensified, driven by their broad applicability in areas from underwater exploration to biomedical assays and earthquake monitoring. The heart of these sensors lies in their diverse energy harvesting mechanisms, including biofuel cells, and piezoelectric, triboelectric, and pyroelectric nanogenerators. Notwithstanding the wealth of research, the literature still lacks a holistic review that integrates the design challenges and implementation intricacies of such sensors. Our review seeks to fill this gap by thoroughly evaluating energy harvesting strategies from both material and structural perspectives and assessing their roles in powering an array of sensors for myriad uses. This exploration offers a comprehensive outlook on the state of self-powered sensing devices, tackling the nuances of their deployment and highlighting their potential to revolutionize data gathering in autonomous systems. The intent of this review is to chart the current landscape and future prospects, providing a pivotal reference point for ongoing research and innovation in self-powered wireless sensing technologies.

Research Progress in Enzyme Biofuel Cells Modified Using Nanomaterials and Their Implementation as Self-Powered Sensors

Enzyme biofuel cells (EBFCs) can convert chemical or biochemical energy in fuel into electrical energy, and therefore have received widespread attention. EBFCs have advantages that traditional fuel cells cannot match, such as a wide range of fuel sources, environmental friendliness, and mild reaction conditions. At present, research on EBFCs mainly focuses on two aspects: one is the use of nanomaterials with excellent properties to construct high-performance EBFCs, and the other is self-powered sensors based on EBFCs. This article reviews the applied nanomaterials based on the working principle of EBFCs, analyzes the design ideas of self-powered sensors based on enzyme biofuel cells, and looks forward to their future research directions and application prospects. This article also points out the key properties of nanomaterials in EBFCs, such as electronic conductivity, biocompatibility, and catalytic activity. And the research on EBFCs is classified according to different research goals, such as improving battery efficiency, expanding the fuel range, and achieving self-powered sensors.

A highly sensitive colorimetric DNA sensor for MicroRNA-155 detection: leveraging the peroxidase-like activity of copper nanoparticles in a double amplification strategy

A novel and highly sensitive colorimetric DNA sensor for determination of miRNA-155 at attomolar levelsis presented that combines the peroxidase-like activity of copper nanoparticles (CuNPs) with the hybridization chain reaction (HCR) . The utilization of CuNPs offers advantages such as strong interaction with double-stranded DNA, excellent molecular recognition, and mimic catalytic activity. Herein, a capture probe DNA (P1) was immobilized on carboxylated magnetic beads (MBs), allowing for amplified immobilization due to the 3D surface. Subsequently, the presence of the target microRNA-155 led to the formation of a sandwich structure (P2/microRNA-155/P1/MBs) when P2 was introduced to the modified P1/MBs. The HCR reaction was then triggered by adding H1 and H2 to create a super sandwich (H1/H2)n. Following this, Cu2+ ions were attracted to the negatively charged phosphate groups of the (H1/H2)n and reduced by ascorbic acid, resulting in the formation of CuNPs, which were embedded into the grooves of the (H1/H2)n. The peroxidase-like activity of CuNPs catalyzed the oxidation reaction of 3,3',5,5'-Tetramethylbenzidine (TMB), resulting in a distinct blue color measured at 630 nm. Under optimal conditions, the colorimetric biosensor exhibited a linear response to microRNA-155 concentrations ranging from 80 to 500 aM, with a detection limit of 22 aM, and discriminate against other microRNAs. It was also successfully applied to the determination of microRNA-155 levels in spiked human serum.

Constructed a self-powered sensing platform based on nitrogen-doped hollow carbon nanospheres for ultra-sensitive detection and real-time tracking of double markers

Acute myocardial infarction (AMI) is acute necrosis of a portion of the myocardium caused by myocardial ischemia, which seriously threatens people's health and life safety. Its early diagnosis is a difficult problem in clinical medicine. Research has found that the abnormal expression of microRNA-199a (miR-199a) and microRNA-499 (miR-499) was closely related to AMI disease. In this work, we took advantage of the structural advantages of nitrogen-doped hollow carbon nanospheres (N-HCNSs) to design an ultra-sensitive, portable real-time monitoring visual self-powered biosensor system, which based on dual-target miRNAs triggered catalytic hairpin assembly (CHA) for sensitive detection of miR-199a and miR-499. In addition, the capacitor and the smartphone are introduced into the system to realize the secondary improvement of system sensitivity and portable real-time visual monitoring. Under optimized conditions, in the linear range of 0.1-100000 aM, the detection limits of miR-199a and miR-499 are 0.031 and 0.027 aM, respectively. At the same time, the ultra-sensitive detection of miRNAs is realized in the serum sample, and the recovery rate of miR-199a and miR-499 are 98.0-106.0% (RSD: 0.6-8.1%) and 94.0-109.7% (RSD: 1.8-7.7%), respectively. The method is simple, sensitive and can be used for real-time tracking and portable monitoring of related diseases.

Nitrogen and fluoride co-doped graphdiyne with metal-organic framework (MOF)-derived NiCo2O4-Co3O4 nanocages as sensing layers for ultra-sensitive pesticide detection

Heteroatom doped graphdiyne (GDY) has been demonstrated to be an effective strategy for achieving outstanding electrochemical properties, including improved electrocatalytic activity, tunable electronic properties and high electronic conductivity, by producing numerous heteroatomic defects as well as active sites. Extensive efforts have been devoted to the issue of single element doping of GDY. Introducing two or more kinds of heteroatoms into GDY materials may create a synergic effect between the co-dopants, thus generating superior electrochemical performance. Nevertheless, little research on multiple elements co-doped GDY, especially in the application of constructing electrochemical biosensor. Herein, nitrogen and fluoride co-doped GDY (N-F-GDY) has been synthesized and employed to combine with NiCo₂O₄-Co₃O₄ hollow multishelled nanocages to establish an ultrasensitive electrochemical biosensor for the assay of pesticide residue. The as-prepared electrochemical biosensor possesses a wide linear range of 0.448 pM-44.8 nM for monocrotophos detection and a low detection limit of 0.0166 fM (S/N = 3).

Electrochemical sensing mechanism of ammonium ions over an Ag/TiO2 composite electrode modified by hematite

Here, we demonstrate a new electrochemical sensing mechanism of ammonium ions (NH₄⁺) involving a two-electron oxygen reduction reaction (ORR) and a hydrazine reaction. The NH₄⁺ are electrooxidized to hydrazine by H₂O₂ derived from the ORR over a self-supporting Ag/TiO₂ nanotube array composite electrode modified by hematite (Ag/Fe₂O₃/TNTs). The Ag/Fe₂O₃/TNT sensor exhibits a high sensitivity of 1876 µA mM^-1 cm^-2 with a detection limit of 0.18 µM under non-alkaline conditions, a short response time of 3 s, good reproducibility, and fine selectivity among various interferents, and is also successfully used in real water bodies to display high accuracy. Furthermore, this new mechanism has a certain universality in a range of Ag (main catalyst)/transition metal oxide (cocatalyst)/TNT sensing systems. This work offers a new design basis for the urgently needed electrochemical ammonia nitrogen sensors.