Ultrasensitive Determination Research Articles

Ultrasensitive SERS Profiling of Intracellular Hydrogen Peroxide Release Based on Enzymatic Amplification and Silent-Region Raman Reporter.

Surface-enhanced Raman scattering spectroscopy (SERS) has been widely applied to screen biomarkers and biological species due to its high sensitivity; however, severe background noise signals significantly limit its practical application. In this study, we develop an ultrasensitive SERS sensor to determine cellular oxidative stress based on the H2O2-induced enzymatic amplification and a silent-range Raman fingerprint. In the presence of horseradish peroxidase, H2O2 could trigger the coupling reaction of 4-hydroxythiophenol (4-MTP) with phenol-d5 to form a new compound, which can bind to the SERS substrate via the Au-S bond and generate the stable SERS signal with nearly zero background signals owing to the Raman-silent fingerprint of phenol-d5 at 2125 cm-1. The high-performance enzymatic reaction and the silent-range Raman fingerprint enable the ultrasensitive determination of H2O2 with a broad linear range of 5 × 10-9 to 1 × 10-3 M and a limit of detection as low as 1.6 nM. Taking advantage of its excellent sensitivity and anti-interference capability, the as-developed SERS sensor is employed to profile the triggered dynamic change of the intracellular H2O2 release, and further to testify the cancerous cells exhibiting a significantly higher level of intracellular oxidative stress than the healthy cells, and the different cell populations possessing the susceptible difference to additional oxidative stimulation. This study paves the way for improving SERS sensing capability through the silent-range fingerprint and signal amplification via an enzymatic reaction and reveals SERS as an effective tool for monitoring the endogenous oxidative behavior of living cells.

An electrochemiluminescence sensor for ultrasensitive determination of tyrosine based on ceria nanomaterial as a novel luminophor

BackgroudRecently, optical nanomaterials have attracted much attention in the field of electrochemiluminescence (ECL). Nanostructured ceria possessed unique optical properties, and it's always used for constructing ECL sensor as catalyst for improving sensing performance, while the ECL property of ceria is rarely studied. In fact, it could be the potential candidate for applying in ECL sensors based on size and shape dependency optical property caused by the quantum scale effects. Therefore, new simple and efficient ceria nanomaterial used as luminophor for constructing the ECL sensor have aroused more research interest and motivation. (91 words). ResultsIn the work, three kinds of nanostructured ceria, ceria nano-cube (CeO2-NC), ceria nano-rods (CeO2-NR) and ceria nano-particle (CeO2-NP), have been prepared by hydrothermal method, and CeO2-NC with the less oxygen vacancy has the highest ECL signal. Moreover, how the shape affects the ECL property was investigated in detail, especially the oxygen vacancy on the surface of the ceria. The less of oxygen vacancy content of CeO2 nanomaterials is more favorable the ECL reaction. Furthermore, a novel ECL sensor was constructed based on reduced graphene oxide (rGO), Au nano-particle (AuNPs) and CeO2-NC for Tyrosine (Tyr) determination owing to the electron transform between the luminous of ceria and Tyr resulting in the cathodic ECL intensity quenched correspondingly, and it has possessed excellent sensing performance with a linear range of 0.005–20 nmol/L and the limit of detection (LOD) value of 1.7 fmol/L (141 words) Significance and noveltyThe proposed method demonstrated excellent selectivity and ultra-sensitivity toward Tyr, which had been used for the determination of Tyr in human serum successfully, possessing outstanding analytical performance. Therefore, nanostructured ceria is a new category of efficient and promising luminophore, which would open new avenues for the potential application in the field of ECL sensing for clinical diagnosis. (57 words).

In situ construction of oriented Au/PPy nanorod arrays-based aptasensor for fast and ultrasensitive determination of thrombin

The dynamic changes in coagulation function indicators provide important references for early warning, disease progression, and prognosis evaluation of clinical cardio-cerebrovascular disease (CCVD) patients. However, current assay methods, such as enzyme-linked immunosorbent assay (ELISA), fluorescence immunoassay and colorimetry, are time-consuming, require bulky equipment, tedious operations, and long analytical period, which are difficult in achieving an on-site and rapid detection. To address above issues, we proposed an ultrasensitive and fast-responded aptasensor for the detection of a typical coagulation function indicator (Thrombin, Tob) through constructing a unique oriented Au/polypyrrole (PPy) nanorod arrays. This architecture has provided both high electrocatalysis and abundant active sites as the signal transfer and DNA carrier. Meanwhile, through the specific DNA-binding representative design, we also designed a target-induced chain release strategy based on the competitive interaction between Tob and cDNA, which remarkably accelerated the Tob recognition process. This aptasensor enables to present an ultralow detection limit of 3 fg/mL and fast detection time of 20 min in real human serum samples, together with the favorable repeatability, stability and anti-interference ability for early warning and prognosis prediction of CCVD. It is promising that this aptasensor can be extended to analyze more disease markers through the change of different bases sequence of the applied DNA stands, which will provide an on-site and convenient technique and device for clinical disease diagnosis.

CuO@3D graphene modified glassy carbon electrode towards the detection of Orange II and Rhodamine B

Synthetic dyes are illegally used in foodstuffs and cause serious health issues in humans due to their carcinogenic nature. To avoid serious health issues, it is compulsory to detect and remove even the minute quantities of these harmful dyes in foodstuffs. Electrochemical sensors are accredited as an efficient and promising platform for the robust and sensitive determination of food toxins in various foodstuffs. Therefore, an efficient, facile, and competent sensor is devised for the simultaneous detection of Orange II (OR II) and Rhodamine B (RhB) supported by rGO and CuO nanoparticles. The synergism between rGO’s immense surface area and the adsorption properties of CuO enhances selectivity and response time for the detection of OR II and RhB. This work elaborated the synthesis, characterization, and electrochemical behavior of CuO@3DGr electrode towards simultaneous sensing of OR II and RhB. Physicochemical techniques were utilized to validate the fabrication of targeted material. On the other hand, the electrochemical features of the developed sensor were characterized by cyclic voltammetry (CV) and electron impedance spectroscopy (EIS). Differential pulse voltammetry technique was employed to detect simultaneously Orange II and Rhodamine B on the surface of bare (GCE), GO/GCE, CuO/GCE, and CuO@3DGr/GCE. Multi-analyte detection is possible with DPV, a sensitive electrochemical method. Based on each toxin’s specific electrochemical signature, the sensor may generate separate peaks by delivering a sequence of potential pulses and detecting the ensuing current. The parameters which influence the performance of the modified sensor were carefully evaluated. Under ambient conditions, the developed sensor exhibited excellent electrocatalytic activity in oxidation at 0.67 V of OR II and 0.96 V RhB with a low limit of detection 08 nM for OR II and 4.5 nM for RhB in Britton- Robinson buffer (BRB pH:7). The described methodology allowed a robust and fast analysis of food toxins in different foodstuff establishing this sensor as a novel tool for detecting food toxins. Tap water was used to analyze the practical applicability of developed electrode material and suitable results were achieved. These results showed that the as-synthesized novel electrochemical sensor has the potential for ultrasensitive determination and detection of toxins in different foodstuffs.

A simple electrochemical immunosensor based on MWCNTs-COOH/Fc-COOH@CoAl-LDH, nanocomposite for sensitive detection of the tumor marker CA724

A novel label-free electrochemical immunosensor for the ultrasensitive determination of cancer antigen (CA724) was developed using a novel composite of CoAl layered double hydroxides (CoAl-LDH) and carboxyl-functionalized multiwall carbon nanotubes (MWCNTs-COOH) as platform and ferrocenecarboxylic acid (Fc-COOH) as signal label. The MWCNTs-COOH/Fc-COOH@CoAl-LDH composite was prepared by a convenient and simple one-step ultrasonic method, and various characterization techniques consisting of scanning electron microscopy (SEM), transimission electronic microscopy (TEM), TEM-Mapping, fourier transform infrared (FT-IR), X-ray diffraction (XRD) and X-ray photoelectronic energy spectrum (XPS) were applied to study the size and morphological features. Due to its large specific surface area and multilayer structure, the CoAl-LDH can be post-doped to embed a large amount of signal probe to realize the amplification of the internal reference signal Fc. In addition, the higher conductivity of MWCNTs-COOH compensates for the deficiency of CoAl-LDH, which effectively strengthened the electron transfer efficiency of electrochemical signaling substances. The optimal experimental conditions were detected to be 2.5 mmol of Fc-COOH, 4.0 mg/mL of concentration, pH 6.0, incubation time of 40 min, and incubation temperature of 37 ℃. Under optimal conditions, the fabricated sensor exhibits linearity in a wide dynamic range covering the physiological concentration, from 0.001 to 100 U/mL and the limit of detection (LOD) was 0.03962 mU/mL, the calibration equation is stated as △I = 7.76363 log10CCA724 + 40.50351 (R2 = 0.99674). The sensor is successfully detects trace levels of CA724 in human serum with excellent recovery rates ranging from 100.52 %-102.30 %, proving the synergy of MWCNTs-COOH/Fc-COOH@CoAl-LDH as a promising platform for electrochemical sensing for clinical detection of other disease markers.

Asymmetric Nanopore Sensor for Logic Detection of Dam and M.SssI Methyltransferases in Combination of DNA Walker and Autocatalytic Hybridization Reaction.

The detection of DNA methyltransferase (MTase) was crucial for understanding gene expression regulation, cancer mechanisms, and various biological processes, contributing significantly to disease diagnosis and drug development. Herein, a nanopore sensor based on cascaded signal amplification of DNA walker and autocatalytic hybridization reaction (AHR) was developed for the ultrasensitive determination of various MTases. In the presence of Dam MTase, the hairpin structure HD underwent methylation and cleavage by DpnI endonuclease, forming T-DNA fragments. These T-DNA fragments were used to activate the DNA walker, which moved across the surface of magnetic beads step by step, generating a large quantity of initiator I by cleaving the substrate. The initiator I subsequently activated the AHR. The AHR included a hybridization chain reaction (HCR) amplifier and a catalytic hairpin assembly (CHA) convertor. The HCR amplifier generated multiple novel CHA triggers, which activated the CHA convertor. This, in turn, stimulated the HCR amplifier, creating an AHR circuit that resulted in the formation of numerous DNA nanowires. These DNA nanowires were adsorbed onto the G4-PAMAM-modified nanopore surface under the influence of an electric field, thereby altering the surface charge of the nanopore and changing the ionic rectification curve. The detection limit of the Dam MTase nanopore sensor reached 0.0002 U/mL. By modification of the recognition sites of the probes, this nanopore system could also be used for the detection of M.SssI MTase. Moreover, a four-input parallel concatenated logic circuit (AND//INHIBIT-OR) had been constructed and applied for the multivariate detection of Dam MTase and M.SssI MTase, presenting a novel conceptual model for advancing the construction of nanopore logic gate systems and their applications in biosensing.

Optimized aptamer-based next generation biosensor for the ultra-sensitive determination of SARS-CoV-2 S1 protein in saliva samples

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus, which rapidly spread worldwide and resulted in a pandemic. Efficient and sensitive detection techniques have been devised since the onset of the epidemic and continue to be improved at present. Due to the crucial role of the SARS-CoV-2 S1 protein in facilitating the virus's entry into cells, efforts in detection and treatment have primarily centered upon this protein. In this study, a rapid, ultrasensitive, disposable, easy-to-use, cost-effective next generation biosensor based on optimized aptamer (Optimer, OPT) was developed by using a disposable pencil graphite electrode (PGE) and applied for the impedimetric determination of SARS-CoV-2 S1 protein. The S1 protein interacted with the OPT in the solution phase and then immobilized onto the PGE surface. Subsequently, measurements using electrochemical impedance spectroscopy (EIS) were conducted in a solution containing a redox probe of 1 mM [Fe(CN)6]3−/4−. Under optimum conditions, the limit of detection (LOD) for the S1 protein in buffer medium at concentrations ranging from 101 to 106 ag/mL was calculated as 8.80 ag/mL (0.11 aM). The selectivity of the developed biosensor was studied against MERS-CoV-S1 protein (MERS) and Influenza Hemagglutinin antigen (HA). Furthermore, the application of the biosensor in artificial saliva medium is demonstrated. The LOD was also calculated in artificial saliva medium in the concentration range of 101–105 ag/mL and calculated as 2.01 ag/mL (0.025 aM). This medium was also used to assess the selectivity of optimized-aptamer based biosensor.

Dually-amplified electrochemical aptasensor based on the self-linking AuPt nanoflowers for ultrasensitive determination of hemagglutinin

BackgroundInfluenza virus can spread from person to person and cause epidemics. Therefore, rapid and sensitive diagnosis of virus is essential in controlling influenza outbreaks. Conventional virus diagnostic techniques are time-consuming, labor-intensive and requires large instruments. In this work, a sandwich electrochemical assay by a pair of aptamers was developed for ultrasensitive determination of hemagglutinin (HA) protein, which is one of the two surface glycoproteins of influenza A (H1N1) virus, using dual signal amplification techniques. ResultsHA was captured and magnetically separated by Fe3O4@SiO2–NH2@Au attached to aptamer 1 (Apt1), creating a sandwich structure with AuPt nanoflowers (AuPtNFs) connected to aptamer 2 (Apt2). Herein, AuPtNFs could catalyze H2O2/hydroquinone (HQ) to generate 1,4-benzoquinone (BQ), and achieved amplification of electrochemical signal detection through differential pulse voltammetry (DPV). The constructed aptasensor expressed a wide linear range (10 pg/mL-100 ng/mL) with limit of detection (LOD) of 2.4 pg/mL. Moreover, a novel strategy for dual signal amplification was developed to further enhance sensitivity. The innovative electrochemical aptasensor could achieve secondary amplification of the detection signal with LOD of 0.3 pg/mL and linear concentration range from 0.5 pg/mL to 100 ng/mL. The secondary amplification could be achieved only through the self-linking process, which allowed for the retention of numerous AuPtNFs by simple complementary base pairing to connect more AuPtNFs onto the above-mentioned sandwich structure. SignificanceOverall, the constructed aptasensor exhibited favorable sensitivity and accuracy, indicating the potential expanded application for the clinical detection of numerous viruses.

A novel composite electrochemical sensor doped ion-imprinted polymer based on N-methacryloyl-L-histidine/ethylene glycol dimethacrylate for ultrasensitive determination of copper (II) ions in food supplements

A novel composite electrochemical sensor doped ion-imprinted polymer based on N-methacryloyl-L-histidine/ethylene glycol dimethacrylate for ultrasensitive determination of copper (II) ions in food supplements

Sodium salicylate as a green fluorescent probe for ultrasensitive determination of vonoprazan fumarate via fluorescence switch off strategy; greenness assessment

A green, simple and sensitive spectrofluorometric approach for determining vonoprazan fumarate in bulk and pharmaceutical dosage form by turning off the fluorescence of sodium salicylate is developed. The addition of vonoprazan fumarate reduced linearly the fluorescence intensity of 0.4 mM sodium salicylate at λem 408 nm and at λex 330 nm. The approach was found to be linear in the 50.0–3000.0 ng/mL range. The limits of detection and quantification were 10.97 and 33.23 ng/mL, respectively. The presented method proved its suitability in determination of vonoprazan fumarate in its pure and pharmaceutical dosage form. This method employs water as the exclusive solvent and utilizes safe reagents, evaluated using the Analytical Eco Scale, Green Analytical Procedure Index (GAPI), and carbon footprint. In contrast, previous methods relied on toxic reagents and required extended heating times, resulting in higher environmental impact. The novel method not only enhances analytical efficiency but also aligns with green chemistry principles, offering a sustainable solution for routine pharmaceutical analysis.

Covalent organic framework-based ratiometric electrochemical sensing platform for ultrasensitive determination of amyloid-β 42 oligomer

Accurate and sensitive detection of amyloid-β 42 oligomer (Aβ42O) is of great significance for early diagnosis of Alzheimer's disease (AD). Herein, a signal on-off ratiometric electrochemical immunosensor was developed for highly selective and quantitative determination of Aβ42O by using novel covalent organic frameworks (COFs) composites as the sensing platform. This immunosensor produced two independent electrochemical signals from the [Fe(CN)6]3−/4− and methylene blue (MB) probes at different potentials based on the electrocatalytic activity of gold nanoparticle−functionalized porphyrinyl COFs nanocomposites toward [Fe(CN)6]3−/4− and the signal probe of MB encapsulated in the aptamer-modified alkynyl COFs. Because the two signals of [Fe(CN)6]3−/4− and MB changed in opposite directions, a signal on−off mode was generated which can correct the results by introducing a reference signal and effectively eliminate background interference. Under optimal experimental conditions, the current ratio (IMB/I[Fe(CN)6]3−/4−) was well linearly related to the logarithmic value of Aβ42O concentrations in the range of 10 pM to 1 μM, and the detection limit was 5.1 pM (S/N = 3). Additionally, the immunosensor exhibited satisfactory performance in case of real cerebrospinal fluid samples. The designed ratiometric electrochemical immunosensor provides a valuable route for early diagnosis of AD and our results also pave the way for designing of sensing platforms using COF-based nanomaterials and extending their functions and applications to bioanalysis.

Facial synthesis of fluorine-engineered magnetic covalent organic framework for selective and ultrasensitive determination of fipronil, its metabolites and analogs in food samples

To improve the adsorption affinity and selectivity of fipronils (FPNs), including fipronil, its metabolites and analogs, a magnetic covalent organic framework (Fe3O4@COF-F) with copious fluorine affinity sites was innovatively designed as an adsorbent of magnetic solid-phase extraction (MSPE). The enhanced surface area, pore size, crystallinity of Fe3O4@COF-F and its exponential adsorption capacities (187.3–231.5 mg g−1) towards fipronils were investigated. Combining MSPE with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), an analytical method was established for the selective determination of fipronils in milk and milk powder samples. This method achieved high sensitivity (LODs: 0.004–0.075 ng g−1), satisfactory repeatability and accuracy with spiked recoveries ranging from 89.9% to 100.3% (RSDs≤5.1%). Overall, the constructed Fe3O4@COF-F displayed great potential for the selective enrichment of fipronils, which could be ascribed to fluorine‑fluorine interaction. This method proposed a feasible and promising strategy for the development of functionalized COF and broadened its application in fluorine containing hazards detection.

Colorimetric and ECL dual-mode aptasensor for smartphone-based onsite sensitive detection of aflatoxin B1 in combination with ZnO@MWCNTs/g-C3N4 nanosheets and CuO@CuPt nanocomposites

The development of dual-mode strategies with superior sensitivity and accuracy have garnered increasing attention for researchers in Aflatoxin B1 (AFB1) analysis. Herein, a colorimetric-electrochemiluminescence (ECL) dual-mode biosensor was constructed for onsite and ultrasensitive determination of AFB1. The multi-wall carbon nanotubes (MWCNTs) were integrated with the ZnO metal organic frameworks (MOFs) to accelerate the electron transfer and boost the ECL intensity of g-C3N4 nanoemitters. Through the aptamer-based DNA sandwich assay, the CuO@CuPt nanocomposites were introduced onto the electrode and acted as the dual functional signal nanoprobes. Due to the good spectrum overlap between the CuO@CuPt nanoprobes and g-C3N4 nanosheets, ECL signal could be efficiently quenched. Additionally, the CuO@CuPt nanoprobes show superior catalytic properties towards the TMB and H2O2 colorimetric reactions, and an obvious color alteration from colorless to blue can be observed using the smartphone. Under optimized conditions, a sensitive and accurate dual-mode analysis of the AFB1 was accomplished with the colorimetric detection limit of 3.26 fg/mL and ECL detection limit of 0.971 fg/mL (S/N = 3). This study combines innovative nanomaterial properties of ZnO@MWCNTs, g-C3N4 and CuO@CuPt for ultrasensitive dual-mode detection, which offers new opportunities for the innovative engineering of the dual-mode sensors and demonstrates significant potential in food safety analysis.

Electrochemical aptasensor for ultrasensitive cadmium detection through hybridization chain-amplified reaction

Detection of cadmium ion (Cd2+) is of great necessity in safeguarding public health by providing accurate information about its presence in food matrices. A signal amplification electrochemical biosensor system with DNA cascade reaction was designed for ultrasensitive determination of Cd2+, in which in-situ synthesized Ag nanoclusters (Ag NCs) were identified as signal reporters. The highly conductive electrode with large active area, produced by gold deposition on the screen-printed electrodes (SPE), was regarded as an electrochemical platform. Cd2+ aptamer (Apt) was immobilized on the Au NPs modified SPE (Au-SPE) through the Au-S bound to capture Cd2+ by conformational change. Meanwhile, the unoccupied Apt was able to be paired with H1 and H2 by base complementation to accelerate the hybridization chain reaction (HCR) cascade, and the in-situ synthesis of Ag NCs on cytosine-rich sequence of H1 to achieve the quantification of Cd2+ according to the linear sweep voltammetry (LSV). The constructed electrochemical aptasensor exhibited a linear range from 0.1 ng/mL to 100 ng/mL, and the detection limit was 0.088 ng/mL for Cd2+ under optimal conditions. This HCR-based electrochemical aptasensor allowed practical application to tea and vegetable samples with satisfactory accuracy, confirming its promising application for rapid detection of targets in complex systems. Therefore, this platform holds promise for the rapid detection of heavy metals.

MOF-derived multi-"hotspot" 3D Au/MOF-808 (Zr) nanostructures as SERS substrates for the ultrasensitive determination of thiram.

Aconvenient self-assembly methodis proposed for synthesis of 3D Au/MOF-808 (Zr) composite nanostructures with a cerium metal-organic framework loaded with gold nanoparticles. We combine adsorption properties of MOF materials with surface plasmon resonance of noble metals to construct hotspot-dense 3D Au/MOF-808 (Zr) SERS substrates, by using a two-step method of solvothermal and reduction reactions. The results show that optimal SERS substrates are obtained from a volume ratio of gold nanoparticles to MOF-808 (Zr) solution of 4:1 and a self-assembly time of 2h. Rhodamine 6G (R6G) is used as a molecular probe to characterize and analyze SERS properties of substrates of 3D Au/MOF-808 (Zr) prepared under the optimal process conditions, where the substrates are capable to detect R6G concentrations down to 10-10 M with a relative standard deviation of 8.81%. Finally, we applied the SERS substrates of 3D Au/MOF-808 (Zr) to the detection of pesticide thiram, and establish a quantitative determination method. 3D Au/MOF-808 (Zr) provides a sensitive detection of thiram in lake water by SERS with a detection limit of 1.49 × 10-9 M. Application tests show that a SERS enhancement factor of the MOF-based SERS substrates for the detection of thiram can be significantly increased to 5.91 × 105. Thus, the above results indicate that such substrate has high sensitivity, good adsorption, homogeneity, and reproducibility, which can be extended for sensitive detection of pesticide residues in food and environment.

A novel photoelectrochemical self-screening aptamer biosensor based on CAU-17-derived Bi2WO6/Bi2S3 for rapid detection of quorum sensing signal molecules

Quorum sensing signal molecule is an important biomarker released by some microorganisms, which can regulate the adhesion and aggregation of marine microorganisms on the surface of engineering facilities. Thus, it is significant to exploit a convenient method that can effectively monitor the formation and development of marine biofouling. In this work, an advanced photoelectrochemical (PEC) aptamer biosensing platform was established and firstly applied for the rapid and ultrasensitive determination of N-(3-Oxodecanoyl)-l-homoserine lactone (3-O-C10-HL) released from marine fouling microorganism Ponticoccus sp. PD-2. The visible-light-driven Bi2WO6/Bi2S3 heterojunction derived from metal-organic frameworks (MOFs) CAU-17 and self-screened aptamer were employed as the photoactive materials and bioidentification elements, respectively. Appropriate amount of MoS2 quantum dots (QDs) conjugated with single-stranded DNA were introduced by hybridization to enhance the photocurrent response of the PEC biosensor. The self-screening aptamer can specifically recognize 3-O-C10-HL, accompanied by increasing the steric hindrance and forcing MoS2 QDs to leave the electrode surface, resulting in an obvious reduction of photocurrent and achieving a dual-inhibition signal amplification effect. Under the optimized conditions, the photocurrent response of PEC aptasensor was linear with 3-O-C10-HL concentration from 1 nM to 10 μM, and the detection limit was as low as 0.26 nM. The detection strategy also showed a high reproducibility, superior specificity and good stability. This work not only provides a simple, rapid and ultrasensitive PEC aptamer biosensing strategy for monitoring quorum sensing signal molecules in marine biofouling, but also broadens the application of MOFs-based heterojunctions in PEC sensors.

Electrochemical aptasensor with signal amplification strategy of covalent organic framework-derived carbon material for ultrasensitive determination of carbendazim

The inadequate conductivity inherent in some covalent organic frameworks (COFs) presents a challenge for their practical use in electrochemical sensors. To enhance the electrical conductivity of COFs, a high-temperature carbonization process can be employed to carbonize COFs in an inert atmosphere, resulting in the production of COF-derived porous carbon materials. In this study, a highly conductive COF-derived carbon material (COF-T800) was obtained through the calcination of a COF known as TPB-DMTP-COF. Cyclic voltammetry (CV) current responses of the TPB-DMTP-COF electrode, when exposed to [Fe(CN)6]3−/4−, were found to be lower compared to those of a bare glassy carbon electrode (GCE). However, after the carbonization of TPB-DMTP-COF, the COF-T800 electrode exhibited significantly higher current responses than bare GCE. The oxidation current response of COF-T800/GCE in [Fe(CN)6]3−/4− was 3.3 times higher than that of TPB-DMTP-COF, demonstrating superior conductivity for this carbonized material. Subsequently, COF-T800 was employed as an electrochemical aptasensor substrate for signal amplification. This aptasensor had ultrasensitive determination of carbendazim (CBZ) with a linear response from 1.0 × 10−12 to 1.0 × 10−7 M. The detection limit of CBZ was 4.0 × 10−13 M. This aptasensor demonstrated high selectivity and applicability for CBZ. The COF-T800-based electrochemical aptasensor was utilized for detecting CBZ in actual samples with success.

Ultra-Sensitive Determination of Fenitrothion Pesticide in Orange Juice by Gold-Printed Electrode Modified with AgNP/Carbon Dot/MWCNT Nanoarchitecture Employing Electrochemical Impedance Spectroscopy

Ultra-Sensitive Determination of Fenitrothion Pesticide in Orange Juice by Gold-Printed Electrode Modified with AgNP/Carbon Dot/MWCNT Nanoarchitecture Employing Electrochemical Impedance Spectroscopy

Electrochemiluminescence aptasensing method for ultrasensitive determination of lipopolysaccharide based on CRISPR-Cas12a accessory cleavage activity

In this study, an ultrasensitive electrochemiluminescence (ECL) aptasensing method was developed for lipopolysaccharide (LPS) determination based on CRISPR-Cas12a accessory cleavage activity. Tris (2,2'-bipyridine) dichlororuthenium (II) (Ru(bpy)32+) was adsorbed on the surface of a glassy carbon electrode (GCE) coated with a mixture of gold nanoparticles (AuNPs) and Nafion film via electrostatic interaction. The obtained ECL platform (Ru(bpy)32+/AuNP/Nafion/GCE) exhibited strong ECL emission. Thiol-functionalized single-stranded DNA (ssDNA) was modified with a ferrocenyl (Fc) group and autonomously assembled on the ECL platform of Ru(bpy)32+/AuNP/Nafion/GCE via thiol-gold bonding, resulting in the quenching of ECL emission. After hybridization of the LPS aptamer strand (AS) with its partial complementary strand (CS), the formed double-stranded DNA (dsDNA) could activate CRISPR-Cas12a to indiscriminately cleave ssDNA-Fc on the surface of Ru(bpy)32+/AuNP/Nafion/GCE, resulting in recovery of the ECL intensity of Ru(bpy)32+ due to the increasing distance between Fc and the electrode surface. The combination of LPS and AS suppressed the formation of dsDNA, inhibited the activation of CRISPR-Cas12a, and prevented further cleavage of ssDNA-Fc. This mechanism aided in upholding the integrity of ssDNA-Fc on the surface of the electrode and was combined with ECL quenching induced by the target. The ECL intensity decreased linearly as the concentration of LPS increased from 1 to 50,000 pg/mL and followed a logarithmic relationship. This method exhibited a remarkably low detection limit of 0.24 pg/mL, which meets the requirement for low-concentration detection of LPS in the human body. The proposed method demonstrates the capacity of CRISPR-Cas12a to perform non-specific cutting of single-stranded DNA and transform the resultant cutting substances into changes in the ECL signal. By amalgamating this approach with the distinct identification abilities of LPS and its aptamers, a simple, responsive, and discriminatory LPS assay was established that holds immense significance for clinical diagnosis.

Chemical isotope labeling-assisted liquid chromatography-mass spectrometry enables sensitive and accurate determination of dipeptides and tripeptides in complex biological samples

Small peptides have attracted increasing attention for their unique features and diverse biological functions. Achieving rapid separation and accurate quantification, however, remains a challenge because of their low abundance and the co-existence of numerous structural isomers. In this study, we developed a novel approach using isotope chemical labeling for ultrasensitive determination of di/tripeptides in biological samples. We successfully synthesized a novel derivatization reagent, 4-(2-(ethoxymethylene)-3-oxobutanamido)-N,N,N-trimethylbenzenaminium iodide (EOTMBA) as well as its deuterium-labeled isotope reagent (d3-EOTMBA). A total of 97 small peptides, including 89 dipeptides and 8 tripeptides, could be completely derivatized in methanol within 1.5 h at 60 °C. After EOTMBA labeling, analysis of these di/tripeptides were achieved within 22 min by LC-MS/MS analysis. The method demonstrated 86.3%–113% accuracy and the limit of quantification ranged from 0.25 fmol/L to 5 nmol/L. Using this method, we achieved ultrasensitive and accurate quantification of di/tripeptides in 147 plasma, 49 urine and 46 bile samples obtained from healthy individuals and patients with biliary tract diseases. The identified differential di/tripeptide biomarker panels showed promising diagnostic performance for patients with biliary tract cancer with area under the receiver operating curve values from 0.870 to 0.996. Furthermore, this method was successfully applied to quantify di/tripeptides in the extract of an animal-derived traditional Chinese medicine, Eupolyphaga sinensis Walker. These findings highlight the possible application of the analytical method in clinics and for the purposes of quality control of traditional Chinese medicines.