A colorimetric and electrochemical dual-mode biosensor for thrombin using a magnetic separation technique

Molecularly imprinted electrochemical biosensor for thrombin detection by comparing different monomers

Aim: Investigating molecularly imprinted polymers (MIPs) in electrochemical biosensors for thrombin detection, an essential protein biomarker. Comparing different monomers to showcase distinct sensitivity, specificity and stability advantages. Materials & methods: Dopamine, thionine and ethanolamine serve as monomers for MIP synthesis. Electrochemical methods and atomic force microscopy characterize sensor surfaces. Performance is evaluated, emphasizing monomer-specific electrochemical responses. Results: Monomer-specific electrochemical responses highlight dopamine's superior signal change and stability over 30 days. Notably, a low 5 pg/ml limit of detection, a broad linear range (5-200 pg/ml) and enhanced selectivity against interferents are observed. Conclusion: Dopamine-based MIPs show promise for high-performance electrochemical thrombin biosensors, suggesting significant applications in clinical diagnostics.

Multi-modal nanoprobe-enabled biosensing platforms: a critical review

Nanomaterials show great potential for applications in biosensing due to their unique physical, chemical, and biological properties. However, the single-modal signal sensing mechanism greatly limits the development of single-modal nanoprobes and their related sensors. Multi-modal nanoprobes can realize the output of fluorescence, colorimetric, electrochemical, and magnetic signals through composite nanomaterials, which can effectively compensate for the defects of single-modal nanoprobes. Following the multi-modal nanoprobes, multi-modal biosensors break through the performance limitation of the current single-modal signal and realize multi-modal signal reading. Herein, the current status and classification of multi-modal nanoprobes are provided. Moreover, the multi-modal signal sensing mechanisms and the working principle of multi-modal biosensing platforms are discussed in detail. We also focus on the applications in pharmaceutical detection, food and environmental fields. Finally, we highlight this field's challenges and development prospects to create potential enlightenment.

Colorimetric and electrochemical dual-mode uric acid determination utilizing peroxidase-mimicking activity of CoCu bimetallic nanoclusters

We present the preparation of CoCu bimetallic nanoclusters (Co@Cu-BNCs) by a hydrothermal and one-step pyrolysis method to build a colorimetric and electrochemical dual-mode sensing platform for uric acid (UA) detection. In the presence of H2O2, Co@Cu-BNCs with peroxidase-mimicking activity may convert colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue-colored oxidized TMB (oxTMB). However, due to the inhibitory effect of uric acid (UA) on the oxidation process of TMB, the characteristic absorption peak intensity of oxTMB decreased when UA was added into a mixed solution. In this approach, a colorimetric assay platform for the detection of UA was demonstrated, with a linear range of 0.1-195 μM and a low limit of detection of 0.06 μM (S/N ratio of 3). In addition, an even wider detection range is achieved in the electrochemical method, due to the pronounced electrocatalytic activity of Co@Cu-BNCs. The surface of the glassy carbon electrode was modified with Co@Cu-BNCs to build an electrochemical sensor for detecting UA. The sensor achieves a wider linear range from 2 to 1000 μM and a limit of detection of 0.61 μM (S/N ratio of 3). Moreover, the detection of UA in a human serum sample showed satisfactory results. The results proved that the colorimetric and electrochemical dual-mode detection platform was sensitive, convenient and accurate.

A colorimetric/electrochemical sensor based on coral-like CuCo2O4@AuNPs composites for sensitive dopamine detection

As a central neurotransmitter, DA (dopamine) plays a vital part in human metabolism, and its accurate detection is of great significance in disease diagnosis. In this work, we used Cu/Co bimetallic metal-organic frameworks (MOFs) as templates and gold nanoparticles (AuNPs) to construct novel nanocomposite coral-like CuCo2O4@AuNPs with strong peroxidase activity and electrochemical response. The coral-like CuCo2O4@AuNPs showed excellent peroxidase activity, and the Km value was as low as 0.358 mM. In the presence of H2O2, the colorless substrate 3,3',5,5', -tetramethylbenzidine (TMB) can be catalytically oxidized into a blue product. Simultaneously, coral-like CuCo2O4@AuNPs, as an electroactive substance, possess strong electrocatalytic activity, which enhances the electron-transfer rate and promotes excellent current response. In the presence of DA, coral-like CuCo2O4@AuNPs can catalyze the oxidation of DA to dopaquinone, which further enhances the electrochemical signal. In addition, DA captures hydroxyl radicals and inhibits the oxidation of TMB, resulting in an obvious color change (blue turns colorless) and realizing colorimetric detection with the naked eye. On this basis, we successfully established a dual-mode colorimetric/electrochemical sensor using coral-like CuCo2O4@AuNP nanocomposites as a dual-signal probe. Combining colorimetric and electrochemical detection, the sensor achieved a wide linear range (0-1 mM) and a low detection limit (0.07 μM) for DA concentration. It was also successfully used for the detection of DA in human serum and urine with good results. In summary, this work provides an intuitive, economical, sensitive, and promising platform for DA detection.

Recent Advances in the DNA-Mediated Multi-Mode Analytical Methods for Biological Samples

DNA-mediated nanotechnology has become a research hot spot in recent decades and is widely used in the field of biosensing analysis due to its distinctive properties of precise programmability, easy synthesis and high stability. Multi-mode analytical methods can provide sensitive, accurate and complementary analytical information by merging two or more detection techniques with higher analytical throughput and efficiency. Currently, the development of DNA-mediated multi-mode analytical methods by integrating DNA-mediated nanotechnology with multi-mode analytical methods has been proved to be an effective assay for greatly enhancing the selectivity, sensitivity and accuracy, as well as detection throughput, for complex biological analysis. In this paper, the recent progress in the preparation of typical DNA-mediated multi-mode probes is reviewed from the aspect of deoxyribozyme, aptamer, templated-DNA and G-quadruplex-mediated strategies. Then, the advances in DNA-mediated multi-mode analytical methods for biological samples are summarized in detail. Moreover, the corresponding current applications for biomarker analysis, bioimaging analysis and biological monitoring are introduced. Finally, a proper summary is given and future prospective trends are discussed, hopefully providing useful information to the readers in this research field.

Dual-mode biosensor platform based on synergistic effects of dual-functional hybrid nanomaterials

Detection of biomarkers is very vital in the prevention, diagnosis and treatment of diseases. However, due to the poor accuracy and sensitivity of the constructed biosensors, we are now facing great challenges. In addressing these problems, nanohybrid-based dual mode biosensors including optical-optical, optical-electrochemical and electrochemical-electrochemical have been developed to detect various biomarkers. Integrating the merits of nanomaterials with abundant active sites, synergy and excellent physicochemical properties, many bi-functional nanohybrids have been reasonable designed and controllable preparation, which applied to the construction dual mode biosensors. Despite the significant progress, further efforts are still needed to develop dual mode biosensors and ensure their practical application by using portable digital devices. Therefore, the present review summarizes an in-depth evaluation of the bi-functional nanohybrids assisted dual mode biosensing platform of biomarkers. We are hoping this review could inspire further concepts in developing novel dual mode biosensors for possible detection application.

Aptamer-Based Sensors for Thrombin Detection Application

Thrombin facilitates the aggregation of platelet in hemostatic processes and participates in the regulation of cell signaling. Therefore, the development of thrombin sensors is conducive to comprehending the role of thrombin in the course of a disease. Biosensors based on aptamers screened by SELEX have exhibited superiority for thrombin detection. In this review, we summarized the aptamer-based sensors for thrombin detection which rely on the specific recognitions between thrombin and aptamer. Meanwhile, the unique advantages of different sensors including optical and electrochemical sensors were also highlighted. Especially, these sensors based on electrochemistry have the potential to be miniaturized, and thus have gained comprehensive attention. Furthermore, concerns about aptamer-based sensors for thrombin detection, prospects of the future and promising avenues in this field were also presented.

Selecting specific aptamers that bind to ovine pregnancy-associated glycoprotein 7 using real serum sample-assisted FluMag-SELEX to develop magnetic microparticle-based colorimetric aptasensor

The pregnancy-associated glycoproteins (PAGs) have been widely used as biomarkers for the early diagnosis of pregnancy in cattle and sheep. This study aimed to obtain the single-stranded DNA aptamers that specifically bound to ovine pregnancy-associated glycoprotein 7 (ovPAG7) with high affinity (K_d = 9.8-32.4 nM) using real serum sample-assisted FluMag-systematic evolution of ligands by exponential enrichment (SELEX). Subsequently, the selected aptamers were applied to fabricate an ultrasensitive colorimetric aptasensor for ovPAG7 detection based on functionalized magnetic microparticles and hybridization chain reaction. Under the optimized conditions, the colorimetric aptasensor exhibited a broad linear range (0.2-500 ng mL^-1), low detection limit (0.081 ng mL^-1), good recovery rate (94.5-109.1%), and high repeatability (relative standard deviation of 4.02-8.16%) in ovPAG7-spiked serum. Furthermore, this aptasensor was applied to measure the ovPAG7 in serum samples of ewes for pregnancy diagnosis. Blood samples were collected from Chinese Merino ewes on days 22, 28 after artificial insemination (AI) for ovPAG7 detection, respectively. Transrectal ultrasonography diagnosis of pregnancy 45 days after AI was the reference (gold) standard for all PAG tests. Diagnostic sensitivity, specificity, and accuracy of the proposed aptasensor were 95.8, 87.5, and 92.5% at day 22 and 95.8, 90.6, and 93.7% at day 28, respectively. The degree of agreement (Kappa) between developed aptasensor and ultrasonography diagnosis 22 and 28 day after AI were higher than 0.8. These results illustrated that the aptasensor was proved to be a sensitive, reliable and cost-effective way of measuring PAG and might be a useful means of pregnancy detection in ewes.

Development of a phos-tag-based fluorescent biosensor for sensitive detection of protein kinase in cancer cells

Protein kinase can catalyze the phosphorylation of peptides/proteins, and it is closely associated with various human diseases such as cancer, immune deficiencies, and Alzheimer’s disease. Sensitive monitoring of protein kinase...

A Fluorescence Kinetic-Based Aptasensor Employing Stilbene Isomerization for Detection of Thrombin

It is important to detect thrombin due to its physiological and pathological roles, where rapid and simple analytical approaches are needed. In this study, an aptasensor based on fluorescence attenuation kinetics for the detection of thrombin is presented, which incorporates the features of stilbene and aptamer. We designed and synthesized an aptasensor by one-step coupling of stilbene compound and aptamer, which employed the adaptive binding of the aptamer with thrombin to cause a change in stilbene fluorescence attenuation kinetics. The sensor realized detection of thrombin by monitoring the variation in apparent fluorescence attenuation rate constant (k_app), which could be further used for probing of enzyme–aptamer binding. In comprehensive studies, the developed aptasensor presented satisfactory performance on repeatability, specificity, and regeneration capacity, which realized rapid sensing (10 s) with a limit of detection (LOD) of 0.205 μM. The strategy was successful across seven variants of thrombin aptasensors, with tunable k_app depending on the SITS (4-Acetamido-4′-isothiocyanato-2,2′-stilbenedisulfonic acid disodium salt hydrate) grafting site. Analyte detection mode was demonstrated in diluted serum, requiring no separation or washing steps. The new sensing mode for thrombin detection paves a way for high-throughput kinetic-based sensors for exploiting aptamers targeted at clinically relevant proteins.

Aptamer functionalized and reduced graphene oxide hybridized porous polymers SPE coupled with LC-MS for adsorption and detection of human α-thrombin

In this study, reduced graphene oxide (rGO) hybridized high internal phase emulsions were developed and polymerized as porous carriers for aptamer (5'/5AmMC6/-AGT CCG TGG TAG GGC AGG TTG GGG TGA CT-3') modification to enrich human α-thrombin from serum. The structure and properties of the materials were confirmed by scanning electron microscope (SEM), Fourier transform infrared spectroscope (FT-IR), and X-ray photoelectron spectra (XPS). The adsorption ability and selectivity were studied and the thrombin was detected with liquid chromatography-mass spectrometry (LC-MS). The adsorption of thrombin onto the sorbent was achieved within 30 min and the desorption was realized using 5.0 mL of acetonitrile/water (80/20, v/v). The thrombin was quantified by LC-MS according to its characteristic peptide sequence of ELLESYIDGR.

Dual-recognition colorimetric sensing of thrombin based on surface-imprinted aptamer-Fe3O4

Thrombin plays an essential role in blood coagulation and some physiological and pathological processes. The convenient, rapid, sensitive, and specific detection of thrombin is of great significance in clinical research and diagnosis. Herein, surface molecularly imprinted polymer (MIP) was modified on aptamer-functionalized Fe3O4 nanoparticles (MIP-aptamer-Fe3O4 NP) for thrombin colorimetric assay by taking advantage of the peroxidase-like activity of Fe3O4 NP. With the adsorption of thrombin into imprinted cavities, the exposed surface area of Fe3O4 NP decreased, causing a decrease in its peroxidase-like activity toward 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. On the other hand, the reductive amino acids on the thrombin surface also impeded the oxidation of TMB. Both phenomena caused the light blue color of the sensing solution. Thus, a specifically sensitive colorimetric approach for the visual detection of thrombin was proposed with a linear range and limit of detection of 108.1 pmol L-1-2.7 × 10-5 mol L-1 and 27.8 pmol L-1, respectively. Moreover, due to the double recognition elements of MIP and aptamer, the prepared MIP-aptamer-Fe3O4 NP showed higher selectivity to thrombin than that based on only one recognition element. It is worth noting that no special property (e.g. electrochemical or fluorescence activity) of the template was required in this work. Thus, more template molecules can be easily, selectively, and sensitively detected based on the proposed MIP-aptamer-mimic enzyme colorimetric sensing strategy.

Guanosine-rich aptamers@Cu2O nanoparticles: enhanced peroxidase activity and specific recognition capability at neutral pH

The decoration of Cu2O nanoparticles with guanosine-rich aptamers can significantly enhance their peroxidase activity at neutral pH and endow them with specific recognition capabilities. Both the phosphate backbone and guanine of the aptamers contribute to the enhancement. The excellent enzyme-like properties of this Cu2O-aptamer system make it a versatile platform for the development of neutral pH biosensors.

Hybridization Chain Reaction-Amplified Electrochemical DNA-Based Sensors Enable Calibration-Free Measurements of Nucleic Acids Directly in Whole Blood

Hybridization chain reaction (HCR) amplification strategy has been extensively explored for the application of electrochemical DNA-based sensors. Despite the enhancement in its sensitivity using the HCR, such sensor platform exhibited significant sensor-to-sensor variations in current due to variations in probe counts and lengths. To circumvent this, we are developing here a calibration-free "O-N" approach to generate a ratiometric, unitless value that is independent of these variations. Specifically, this approach employs two types of redox reporters, denoted as "One reporter" and "N reporters", with the former attached on the capture DNA and the latter on H1 and H2 strands. By optimizing the attachment sites of these reporters onto DNA strands, we demonstrate a significantly enhanced sensitivity of such sensor platform by four orders of magnitude, achieving accurate, calibration-free measurement of nucleic acids including ctDNA directly in undiluted whole blood without the requirement to calibrate each individual sensor.

Investigation of the Influence of Liquid Motion in a Flow-based System on an Enzyme Aggregation State with an Atomic Force Microscopy Sensor: The Effect of Water Flow

The influence of liquid motion in flow-based systems on the aggregation state of an enzyme and on its enzymatic activity was studied, with horseradish peroxidase (HRP) as an example. Our experiments were carried out in a setup modeling the flow section of the biosensor communication with a measuring cell containing a protein solution. Studies were conducted for a biosensor measuring cell located along the axis of a spiral-moving liquid flow. The aggregation state of the protein was determined with an atomic force microscopy-based sensor (AFM sensor). It has been demonstrated that upon flowing of water through silicone biosensor communications, an increased aggregation of HRP protein was observed, but, at the same time, its enzymatic activity did not change. Our results obtained herein are useful in the development of models describing the influence of liquid flow in biosensor communications on the properties of enzymes and other proteins. This is particularly important for the development of serologic protein biosensors, which are beginning to be used for the early diagnosis of oncological diseases (such as brain cancer, prostate cancer, breast cancer etc.). The results obtained herein should also be taken into account when considering possible changes in hemodynamics due to increased protein aggregation.

An LC-MS/MS method for protein detection based on a mass barcode and dual-target recognition strategy

A mass barcode mediated signal amplification strategy was developed and applied to the determination of protein. A new compound, N'-((2-aminopyridin-3-yl)methylene)-5-(1,2-dithiolan-3-yl)pentanehydrazide (TAPA), was synthesized from the linker and the signal barcode, and used as the bonding barcode. For the realization of signal transduction, TAPAs and the target catcher aptamers, were both modified on gold nanoparticles (AuNPs) to establish the relationship between TAPAs and the target. Owing to the fact that the amount of TAPAs was much greater than the target, the signal of the target was not only transduced to the signal of the mass barcodes, but also amplified greatly. Thrombin, an important biomarker for coagulation abnormality diseases, was selected as a model analyte. Two kinds of thrombin recognition aptamers, aptamer 29 (apt29) and aptamer 15 (apt15), were modified onto the magnetic beads (MBs) and AuNPs, respectively. The modified AuNPs were further functionalized with lots of TAPA and formed apt15-AuNPs-TAPA. MBs-apt29 and apt15-AuNPs-TAPA could both recognize the target thrombin and form the sandwich complex (MBs-apt29/thrombin/apt15-AuNPs-TAPA). After the complex was separated by an extra magnetic field, NaClO oxidant solution was added to release the signal barcodes, 2-Amino-3-pyridinecarboxaldehyde (APA), which were then collected after centrifuging and analyzed by LC-MS/MS. Under optimized conditions, the mass response intensity was proportional to thrombin concentration in the range of 0.05-10 nM, with a 0.007 nM detection limit. This method was applied to the determination of thrombin in spiked serum samples, and the average recoveries ranged from 89.6% to 110.4%, which confirmed the applicability of this method.

Fe–Ni metal–organic frameworks with prominent peroxidase-like activity for the colorimetric detection of Sn2+ ions

The synthesized Fe–Ni-MOF could oxidize TMB to produce oxTMB with blue color. The presence of Sn²⁺ ions could make the oxTMB color lighter, hence colorimetric detection of Sn²⁺ ions is realized.