Biosensing Platform For Ultrasensitive Detection Research Articles

AgAuS Quantum Dots as a Highly Efficient Near-Infrared Electrochemiluminescence Emitter for the Ultrasensitive Detection of MicroRNA.

Herein, the novel alloyed silver gold sulfur quantum dots (AgAuS QDs) with highly efficient near-infrared (NIR) electrochemiluminescence (ECL) emission at 707 nm were successfully prepared to construct a biosensing platform for ultrasensitive detection of microRNA-222 (miRNA-222). Interestingly, AgAuS QDs revealed excellent ECL efficiency (34.91%) compared to that of Ag2S QDs (10.30%), versus the standard [Ru(bpy)3]2+/S2O82- system, which benefited from the advantages of abundant surface defects and narrow bandgaps by Au incorporation. Additionally, an improved localized catalytic hairpin self-assembly (L-CHA) system was developed to display an increased reaction speed by improving the local concentration of DNA strands, which addressed the obstacles of time-consuming traditional CHA systems. As a proof of concept, based on AgAuS QDs as an ECL emitter and improved localized CHA systems as a signal amplification strategy, a "signal on-off" ECL biosensor was developed to exhibit a superior reaction rate and excellent sensitivity with a detection limit of 10.5 aM for the target miRNA-222, which was further employed for the analysis of miRNA-222 from cancer cell (MHCC-97L) lysate. This work advances the exploration of highly efficient NIR ECL emitters to construct an ultrasensitive biosensor for the detection of biomolecules in disease diagnosis and NIR biological imaging.

A ratiometric fluorescent biosensing platform for ultrasensitive detection of Salmonella typhimurium via CRISPR/Cas12a and silver nanoclusters.

Rapid, sensitive and specific detection of bacteria is of great importance. Herein, we developed a versatile biosensing platform for ultrasensitive detection of pathogenic bacteria, termed as SCENT-Cas (Silver nanoCluster Empowered Nucleic acids Test using CRISPR/Cas12a). Simply, the species-specific invA gene of Salmonella typhimurium (S. typhi) was isothermally amplified using LAMP, which subsequently triggered the trans-cleavage of CRISPR/Cas12a. The trans-cleavage degraded any single-stranded DNA (ssDNA) non-specifically. A DNA-templated AgNCs probe was then employed, in which green fluorescence emissive AgNCs effectively converted to red fluorescence emissive AgNCs when placed in close vicinity to a pre-designed converter ssDNA. As such, the trans-cleavage was utilized for shredding converter ssDNA, enabling the green-to-red fluorescent change to form a ratiometric biosensing platform. With this strategy, target nucleic acid was dexterously converted into ratiometric fluorescence that was recorded to detect as low as 1 CFU/mL S. typhi with a dynamic range from 1 to 108 CFU/mL. To our knowledge, this is the first report regarding the use of ratiometric fluorescence in CRISPR/Cas-based detection, which minimizes interference and improves reliability. Lastly, this proposed strategy was challenged by detecting S. typhi contamination in real food samples. Our work enriches CRISPR/Cas toolbox in biosensing by providing a desirable method for bacterial detection.

Photocurrent-Polarity-Switching Photoelectrochemical Biosensor for Switching Spatial Distance Electroactive Tags.

This work presents a photocurrent-polarity-switching-based photoelectrochemical (PEC) biosensing platform for ultrasensitive detection of microRNA-21 (miR-21) through target-triggered catalytic hairpin assembly (CHA) for modulation of methylene blue (MB) and ferrocene (Fc) positional configurations using double-shelled Cu-doped ZnS nanocages (NCs)-Au nanoparticles (NPs) as photoactive materials. In the presence of miR-21, the assembly of MB-labeled HP1 and Fc-labeled HP2 leads to the generation of a large amount of double-stranded DNA (HP1-HP2), which pushes MB away from the electrode surface and brings Fc close to the electrode surface, resulting in effectively quenching the enhanced PEC signal to activate the photocurrent-polarity-switching system. Benefiting from the distance-controllable strategy, the designed PEC bioanalysis can effectively eliminate false-positive and false-negative signals due to the change of different signal expression patterns (from traditional the "signal-on" mode to the photocurrent-polarity-switching mode), thereby significantly improving the sensing specificity and sensitivity. The proposed PEC sensing system exhibited satisfying photocurrent responses toward target miR-21 within the working range from 1.0 fM to 1 nM at a low limit of detection (LOD) of 0.58 fM. More importantly, we demonstrated the successful integration of the proposed PEC biosensor with a handheld wireless device for instant detection of miR-21 concentrations in practical samples.

Real-time multiple signal amplification self-powered biosensing platform for ultrasensitive detection of MicroRNA

A real-time self-powered biosensor is designed for ultrasensitive detection of microRNA-21 based on electrochemical energy device capacitor and target-induced recycling double amplification strategy, which greatly improves the output signal by converting a small number of targets into two glucose oxidase labeled output strand DNAs, and the squeezed-out output strand is recycled by the cathode to fix more signal [Ru(NH3)6]3+ to further improve the detection signal. A digital multimeter (DMM) is connected to computer for real-time displaying the output signal of the self-powered biosensing system, which improves the accuracy of the sensing platform. The sensitivity of the proposed biosensor is 116.15 μA/pM for target microRNA-21, which is 32.26 times higher than that of pure EBFC (3.6 μA/pM). The target concentration is proportional to the open-circuit voltage value in a wide linear range of 0.1–10000 fM with a low detection limit of 0.04 fM (S/N = 3). The method shows high sensitivity and excellent selectivity, and can be applied to detect tumor marker microRNA-21 in biological matrix.

Multiregion Linear DNA Walker-Mediated Ultrasensitive Electrochemical Biosensor for miRNA Detection.

In this work, an intelligent multiregion linear DNA walker (MLDW) with a high walking rate and a high amplification efficiency was explored for ultrasensitive detection of miRNA. Significantly, amounts of functional domain could be concentrated in a long linear DNA obtained by the target miRNA-mediated rolling-circle amplification to simultaneously increase the local concentration and collision probability, resulting in an obviously improved reaction rate. Impressively, the MLDW can accomplish the reaction within 30 min, which is at least 4 times beyond that of traditional single-leg and multiple-leg DNA walkers. As a proof of concept, the high-efficiency MLDW was used to develop an electrochemical biosensing platform for ultrasensitive detection of target miRNA-21 with a low detection limit down to 36 aM. Therefore, the MLDW we designed puts forward an innovative insight to construct a functional DNA nanodevice and promote the investigation of the inherent performance of nucleic acid signal amplification for ultimate application in the detection of biomolecules and clinical disease diagnosis.

Real-Time Multiple Signal Amplification Self-Powered Biosensing Platform for Ultrasensitive Detection of Microrna

Real-Time Multiple Signal Amplification Self-Powered Biosensing Platform for Ultrasensitive Detection of Microrna

Nitrogen-Doped Graphdiyne as a Robust Electrochemical Biosensing Platform for Ultrasensitive Detection of Environmental Pollutants.

Owing to its unique chemical structure, natural pores, high structure defects, good surface hydrophilicity and biocompatibility, and favorable electrical conductivity, nitrogen-doped graphdiyne (NGDY) has been attracting attention in the application of electrochemical sensing. Taking advantage of these fascinating electrochemical properties, for the first time, two types of electrochemical enzymatic biosensors were fabricated for the respective detection of organophosphorus pesticides (OPs) and phenols based on the immobilization of acetylcholinesterase or tyrosinase with NGDY. Results revealed that the sensitivities of the NGDY-based enzymatic biosensors were almost twice higher than that of the matching biosensor in the absence of NGDY, proving that NGDY plays a vital role in immobilizing the enzymes and improving the performance of the fabricated biosensors. The effects of nitrogen doping on improving the biosensing performance were studied in depth. Graphitic N atoms can enhance the electrical conductivity, while imine N and pyridinic N can help to adsorb and accumulate the substance molecules to the electrode surface, all of which contribute to the significantly improved performance. Furthermore, these two types of biosensors also demonstrated excellent reproducibility, high stability, and good recovery rate in real environmental samples, which showed a valuable way for the rapid detection of OPs and phenols in the environment. With these excellent performances, it is strongly anticipated that NGDY has tremendous potential to be applied to many other biomedical and environmental fields.

Development of Field Deployable Sensor for Detection of Pesticide From Food Chain

The use of pesticides in agriculture field remains a serious issue related to public health. This necessitates the need to develop a low cost/portable, sensitive and selective bio-sensing platform for detection of pesticides in food chain. In this work a low-cost biosensing platform for ultrasensitive detection of chlorpyrifos (CPF) is developed. Electrochemical micro Paper Analytical Device ( $\text{E}\mu $ PAD) is fabricated by conventional screen-printing technology. Metal Organic Framework (Z1200 MOF) having zinc metal and imidazole ligand is used as a transducing element which facilitates biocompatible matrix for Acetylcholinesterase (AChE) enzyme immobilization. The limit of detection for CPF is found be 3 ng/L with sensitivity 0.521 $\text{k}\Omega $ /ng $\text{L}^{-1}$ /mm $^{2}$ . The sensor required $100\mu \text{L}$ of reagent and was tested with a linear concentration range of 10 ng/L to 1000 ng/L with response time of 5s. The sensor is further integrated with portable electronics based on Arduino microcontroller and Artificial Intelligence (AI) which provided economical, portable and user-friendly sensing platform. The stability of the sensor was 30 days. The developed sensor was also tested with real samples and the sensor response is in agreement with conventional technique.

3D DNA nanosphere-based photoelectrochemical biosensor combined with multiple enzyme-free amplification for ultrasensitive detection of cancer biomarkers

In this work, a new 3D DNA nanosphere was ingeniously designed and fabricated, which was used to combine with multiple enzyme-free amplification strategy to develop a photoelectrochemical (PEC) biosensing platform for ultrasensitive detection of carcinoembryonic antigen (CEA). The 3D DNA nanostructure was self-assembled by base complementary pairing in a few minutes and rolling circle amplification (RCA) reaction. The intense photocurrent derived from Au NPs/ZnSe QDs can be effectively decreased by 3D DNA nanospheres assembled on the electrode, making photoelectric signal present “off” state. The specific binding of target CEA with its hairpin (HP1) aptamer opens HP1 structure, which initiated multiple enzyme-free strand displacement amplification (SDA) reaction and generated a large number of single strands DNA S1. Then S1 competitively binds to capture DNA on the electrode to release 3D DNA nanospheres, thus the photocurrent signal became “on” state for achieving amplified assay of target CEA. The proposed PEC biosensor exhibits excellent performance with a wide linear range of 1.0 fg/mL to 10 ng/mL and a low detection limit of 0.12 fg/mL for CEA, which was successfully applied for the assay of real serum samples with good precision. The reported strategy opens a new simple way for PEC biosensor using DNA nanostructure, showing huge potential in clinical application research.

A self-enhanced renewable electrochemiluminescence biosensing platform for ultrasensitive detection of sialic acid

Herein, a boronate-affinity renewable electrochemiluminescence (ECL) biosensor was constructed based on a highly efficient Ru (II)-based composite for the sensitive detection of sialic acid (SA). Specifically, the Bi nanobelts (Bi NBs) was first used as coreactant to prepare a self-enhanced Ru(bpy)32+-Bi NBs composite, producing a strong ECL signal by shortening electronic transmission distance and reducing the energy loss. Additionally, HNO3-assisted synthesized rutile TiO2 mesocrystals (Nss-TiO2-RM) with nanoporous nature and single-crystal like structure was employed as scaffold, increasing the immobilization amount of Ru(bpy)32+ and Bi NBs, further enhancing ECL signal. Promisingly, 4-Mercaptophenylboronic acid (4-MPBA) as bionic recognition unit could substitute antibody to capture SA, and moreover a self-cleaning electrode could be obtained after treated by 0.1 M PBS (pH 6). Under optimal conditions, a sandwich-like renewable ECL biosensor was constructed for sensitive detection of SA in the range of 3.5 × 10−5 to 350 ng/mL with a low detection limit of 1.17 × 10−5 ng/mL. This work provided a new thought for other biomarkers determination.

Triple-helix molecular switch-based versatile “off-on” electrochemiluminescence and fluorescence biosensing platform for ultrasensitive detection of lipopolysaccharide by multiple-amplification strategy

Herein, a novel biosensing platform for versatile electrochemiluminescence (ECL) “off” and fluorescence (FL) “on” detection of lipopolysaccharide (LPS) with multiple-amplification strategy is proposed. The specific recognition of target to aptamer on the magnetic beads (MB) firstly released abundant DNA sequences of three kinds. The sequences hybridized with multifunctional molecular beacon (MMB) and initiated numerous bidirectional polymerization and shearing reactions, generating a large number of DNA fragments (a1) by multiple cycling amplification. Then a1 was introduced to the triple-helix sensing system, opening the triple-helix structure. In ECL system, the G-rich chains S2 were exposed to form G-quadruplex-hemin complex in the presence of hemin, which could efficiently quench ECL for “off” detection of LPS. In FL system, the fluorophore FAM and quencher BHQ on S1 chain were separated with opening of triple-helix structure, achieving fluorescence “on” signal for LPS assay. So the versatile platform can achieve greatly amplified ECL and FL signal changes for sensitive assay of LPS, showing wide linear ranges (0.1 fg/mL-0.1 ng/mL by ECL and 10 fg/mL−1-1 μg/mL by FL) and low detection limits (0.012 fg/mL by ECL and 1.269 fg/mL by FL). Therefore, the present ECL “Off” and FL “On” dual-signal detection patterns for LPS displayed many advantages over other reported methods, which provided an outlook for future applications in clinical diagnosis.

Reversible and Distance-Controllable DNA Scissor: A Regenerated Electrochemiluminescence Biosensing Platform for Ultrasensitive Detection of MicroRNA.

Reversing the switching of DNA scissors with precisely control remains a compelling goal. Herein, based on strand displacement reaction within single step, the DNA scissor realized reversible switching and further controlled the distance of end strands along the movement of DNA scissor, which has been applied for the development of a regenerated sensing platform for the ultrasensitive detection of microRNA-21 (miRNA-21) with the electrochemiluminescence (ECL) complex (PEI-Ru(II)) as luminophores and diethylenetriamine (DETA) as the coreactant. In the presence of ferrocene-labeled DNA (Fc-DNA), the DETA-labeled DNA scissor clockwise switched to "off" state based on strand displacement reaction, resulting in the significant ECL quenching of Ru(II) system. Next, by using miRNA-21 as the motive fuel, the configuration of DNA scissor could be anticlockwise switched, which significantly enhanced the ECL intensity of Ru(II) complex due to the releasing of Fc-DNA and the proximity between DETA and Ru(II) complex. The reversible switching of DNA scissor led to the remarkably enhancing of ECL signal, realizing ultrasensitive detection of miRNA-21 with an excellent detection limit of 0.17 fM, which was also applied in miRNA detection successfully from different cancer cells. Impressively, the reversible switching of DNA scissor biosensor was able to realize the regeneration of the biosensing platform by adding an additional single stranded DNA (ssDNA) based on strand displacement reaction within a single step, providing a novel concept for constructing simple and sensitive regenerated biosensor.

Polydopamine induced in-situ growth of Au nanoparticles on reduced graphene oxide as an efficient biosensing platform for ultrasensitive detection of bisphenol A

Bisphenol A (BPA) is one of the most prevalent environmental endocrine disrupting chemicals with potential estrogenic activity. Herein we report a facile electrochemical sensing strategy for ultrasensitive detection of BPA based on the hybrid of AuNPs decorated reduced graphene oxide (RGO). This Au@PDA-RGO hybrid was synthesized by in-situ growth of AuNPs induced by polydopamine (PDA) on RGO. Since PDA acts as a moderate reducing agent and an effective linker, AuNPs scatter well on RGO with controllable density, homogeneous size and uniform distribution. With the aid of chitosan (Chit), an electrochemical tyrosinase (Tyr) biosensor based on Au@PDA-RGO was constructed on glassy carbon electrode (Tyr/Au@PDA-RGO-Chit/GCE). This immobilization matrix possesses high conductivity, large active areas and a suitable biological microenvironment. As a result, the constructed Tyr biosensor exhibited good analytical performance for BPA with a high sensitivity of 0.2569AM−1, a wide linear range from 12.5nM to 3.68μM, and a low detection limit of 0.10nM (S/N=3). This method was also applied to detect BPA in plastic products, showing good agreement with the values detected by HPLC-MS/MS.

Signal-on electrochemical detection of antibiotics based on exonuclease III-assisted autocatalytic DNA biosensing platform

In this work, a novel electrochemical DNA sensor based on exonuclease III (Exo III)-assisted autocatalytic DNA biosensing platform for ultrasensitive detection of antibiotics has been reported.

A versatile immobilization-free photoelectrochemical biosensor for ultrasensitive detection of cancer biomarker based on enzyme-free cascaded quadratic amplification strategy.

In this work, an ultrasensitive immobilization-free photoelectrochemical (PEC) biosensor was successfully developed for the first time based on a novel enzyme-free cascaded quadratic signal amplification strategy. This rationally designed homogeneous dual amplification strategy consists of a target-analog recycling circuit based on catalytic hairpin assembly (CHA) and a hybridization chain reaction (HCR) mediated amplification circuit. In the presence of carcinoembryonic antigen (CEA), a proof-of-concept target, target-analog is released to trigger the upstream CHA recycling circuit. The generated dsDNA complexes from CHA recycling could further induce the downstream HCR amplification, leading to the formation of numerous hemin/G-quadruplex DNAzymes. This would accordingly stimulate the biocatalytic precipitation of 4-chloro-1-naphthol, inducing a distinct decrease in the photocurrent signal due to the formed insoluble/insulating products on electrode surface. Under the optimal conditions, this PEC biosensor achieved ultrasensitive detection of CEA down to the atto-gram level. The introduction of this aptamer-based cascaded quadratic amplification strategy not only remarkably improves the selectivity and sensitivity of CEA assay, but also allows the ultrasensitive detection of other proteins by designing specific aptamers, providing a universal, isothermal and label-free PEC biosensing platform for ultrasensitive detection of different kinds of cancer biomarkers and holding a great potential for early-diagnosis of cancer.

Portable and reusable optofluidics-based biosensing platform for ultrasensitive detection of sulfadimidine in dairy products.

Sulfadimidine (SM2) is a highly toxic and ubiquitous pollutant which requires rapid, sensitive and portable detection method for environmental and food monitoring. Herein, the use for the detection of SM2 of a portable optofluidics-based biosensing platform, which was used for the accurate detection of bisphenol A, atrazine and melamine, is reported for the first time. The proposed compact biosensing system combines the advantages of an evanescent wave immunosensor and microfluidic technology. Through the indirect competitive immunoassay, the detection limit of the proposed optofluidics-based biosensing platform for SM2 reaches 0.05 μg·L−1 at the concentration of Cy5.5-labeled antibody of 0.1 μg·mL−1. Linearity is obtained over a dynamic range from 0.17 μg·L−1 to 10.73 μg·L−1. The surface of the fiber probe can be regenerated more than 300 times by means of 0.5% sodium dodecyl sulfate solution (pH = 1.9) washes without losing sensitivity. This method, featuring high sensitivity, portability and acceptable reproducibility shows potential in the detection of SM2 in real milk and other dairy products.