Simple Colorimetric Biosensor Research Articles

Cu2O nanoparticles with morphology-dependent peroxidase mimic activity: a novel colorimetric biosensor for deoxynivalenol detection.

Different morphological Cu2O nanoparticles including cube, truncated cube, and octahedron were successfully prepared by a selective surface stabilization strategy. The prepared cube Cu2O exhibited superior peroxidase-like activity over the other two morphological Cu2O nanoparticles, which can readily oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to form visually recognizable color signals. Consequently, a sensitive and simple colorimetric biosensor was proposed for deoxynivalenol (DON) detection. In this biosensor, the uniform cube Cu2O was employed as the vehicle to label the antibody for the recognition of immunoreaction. The sensing strategy showed a detection limit as low as 0.01ng/mL, and a wide linear range from 2 to 100ng/mL. Concurrently, the approximate DON concentration can be immediately and conveniently observed by the vivid color changes. Benefiting from the high sensitivity and selectivity of the designed biosensor, the detection of DON in wheat, corn, and tap water samples was achieved, suggesting the bright prospect of the biosensor for the convenient and intuitive detection of DON in actual samples.

Paper chip-based colorimetric biosensor for glucose by using CuFe2O4@GO as nanozyme

The development of nanomaterials with notable enzyme-like activity is of great significance to the field of bioanalysis. Herein, a nanomaterial composed of copper ferrite nanoparticles (CuFe2O4 NPs) and graphene oxide (GO) was successfully prepared (CuFe2O4@GO). The obtained CuFe2O4@GO was proved to have peroxidase-like (POD-like) activity, which could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to generate oxidized TMB (ox-TMB) in the presence of H2O2 with an obvious color change. On this basis, a colorimetric biosensor using a UV–vis spectrometer as readout and a paper chip-based colorimetric biosensor using a smartphone as readout was constructed for glucose detection, respectively, as glucose oxidase (GOD) could oxidize glucose to form H2O2. The UV–vis spectrometer-based approach exhibits a linear range of 0 to 1000 μM and a limit of detection (LOD) of 0.79 μM for glucose. The smartphone-based method shows a linear range of 0.1 to 50 mM and a LOD of 0.04 mM for glucose. Moreover, the fabricated colorimetric biosensors have good selectivity towards glucose and the sample matrixes cannot affect the detection of glucose. Finally, the concentration of glucose in human serum samples was successfully detected using two different ways, and the results are close to the clinical values. The proposed method embraces several good merits. Firstly, the colorimetric biosensors combining UV–vis spectrometer and smartphone offer precise results, which could effectively prevent the occurrence of false events. Secondly, paper-based microfluidic analytical device (μPAD) as analytical platform and smartphone as readout provides a versatile approach for constructing sensitive, cost-effective, and simple colorimetric biosensor for the visual monitoring of glucose. Lastly, except for glucose detection, this work also shows great application prospects for other small molecules detection that could generate H2O2.

Reduced graphene oxide-persimmon tannin/Pt@Pd nanozyme-based cascade colorimetric sensor for detection of 1,5-anhydroglucitol.

1,5-anhydroglucitol (1,5-AG) is of considerable clinical relevance as a biochemical marker of glucose metabolism in the assessment and monitoring of diabetes. Herein, a simple colorimetric biosensor was constructed for the identification and detection of 1,5-AG by using pyranose oxidase (PROD) enzyme cascaded with reduced graphene oxide/persimmon tannin/Pt@Pd (RGO-PT/Pt@Pd NPs) nanozyme. The as-prepared RGO-PT/Pt@Pd NPs had excellent peroxidase-like activity and can be applied as a nanozyme. First, PROD enzyme reacts with the target 1,5-AG, decomposing 1,5-AG into 1,5-anhydrofuctose (1,5-AF) and H2O2. At this point, the highly catalytic RGO-PT/Pt@Pd NPs nanozyme produces a cascade with PROD enzyme which catalyzes the decomposition of H2O2 to produce O2. This in turn oxidizes the substrate 3,3',5,5'-tetramethylbenzidine (TMB) and produces a color change in the solution. Finally, the detection of 1,5-AG was achieved by measuring the absorption peak at 652nm with an ultraviolet visible (UV-vis) spectrophotometer. Under optimal conditions, the linear operating range of the 1,5-AG enzyme cascade colorimetric sensor was 1.0-100.0μg/mL, and the limit of detection (LOD) was 0.81μg/mL. The proposed colorimetric biosensor was successfully applied to detect 1,5-AG in spiked human serum samples with the recoveries of 97.2-103.9% and RSDs of 1.94-4.48%. It provides a promising developmental assay for clinical detection of 1,5-AG.

Aptamer-enhanced the Ag(I) ion-3,3′,5,5′-tetramethylbenzdine catalytic system as a novel colorimetric biosensor for ultrasensitive and selective detection of paraquat

A facile and simple colorimetric biosensor was first established for paraquat (PQ) detection based on the aptamer-enhanced oxidation process of 3,3′,5,5′-tetramethylbenzidine (TMB) by Ag+. The study confirmed that the interaction of PQ-15 aptamer with Ag+ accelerates the electron transfer from the aptamer-Ag+ complex to dissolved oxygen, which enhances the release of superoxide anion radicals (O2̇−) and facilitates the catalytic oxidation of the chromogenic substrate. PQ-15 aptamer will preferentially bind to PQ molecules, resulting in no further enhancement of the catalytic activity of Ag+. Molecular docking results revealed that the PQ molecules are attached to the stem-loop region of the PQ-15 aptamer through σ-π conjugation interactions. The proposed method is simple that only contains Ag+ and corresponding aptamer. The limit of detection (LOD) of the constructed colorimetric biosensor for PQ detection was determined to be 16.5 μg·L-1, belowing the maximum residue limit in fruits and vegetables set by the EU. Moreover, the colorimetric biosensor showed excellent selectivity and anti-interference properties, which was validated for detecting PQ residues in several typical agricultural and water samples.

Optical detection of thiocyanate in human saliva based on the colorimetric response of (2-(2-hydroxyphenyl)-1H-benzo[d]imidazol-5-yl)(phenyl) methanone (HBPM)/Co2+ ions conjugate

Simple colorimetric biosensor was designed for the quantification SCN− ions based on the principle of colorimetric reactions between Co2+ and SCN− ions reaction using synthesized chromophore (2-(2-hydroxyphenyl)-1H-benzo[d]imidazol-5-yl)(phenyl) methanone (HBPM)/Co2+ ions conjugate which was synthesized via greener ultrawave sonication method. The structural characterization of the HBPM chromophore was confirmed by using NMR, ESI-MASS spectral techniques and the photophysical properties, sensor studies were done by using UV–Vis Spectrophotometer. Our designed HBPM/Co2+ ions conjugates have selectively detected SCN− ions qualitatively and quantitatively in the presence of other human salivary interferents. As per clinical point of view, three different ranges of SCN− ions from 0.1 to 2 mM for normal, 3 to 10 mM for disease, and 100–600 µM for below normal ranges were tested successfully by our developed sensor and the LoD was calculated as 5.43 nM. The real potent application of the developed biosensor was tested in human salivary samples of both smokers and non-smokers under different ages and obtained results shown good agreement with existing clinical methods.

Colorimetric Nucleic Acid Detection Based on Gold Nanoparticles with Branched DNA

Nucleic acid detection is becoming increasingly important in the diagnostics of genetic diseases for biological analysis. We herein propose gold nanoparticles as probe for colorimetric detection of nucleic acids with branched DNA nanostructures, which enables a novel and simple colorimetric biosensor. In our system, the target DNA specifically triggered two short-chain ssDNA probes to generate branched DNA nanostructures (Y-shape DNA), which prevent AuNPs from aggregation in aqueous NaCl solution. On the contrary, when the target DNA did not exist, gold nanoparticles were unstable and aggregated easily because there is no anti-aggregation function from Y-shape DNA. Sensor response was found to be proportional to the target DNA concentration from 5 to 100[Formula: see text]nM, with detection limits determined as 5[Formula: see text]nM. The developed platform is for colorimetric nucleic acid detection without enzymes, label and modification holds great promise for practical applications.

A colorimetric detection of microRNA-148a in gastric cancer by gold nanoparticle–RNA conjugates

For the early diagnosis of gastric cancer, microRNA-148a (miRNA-148a) as a promising biomarker is measured by a simple colorimetric biosensor due to its unique surface plasmon resonance (SPR) absorption of gold nanoparticles (AuNPs). In the assay system, the sensing probes are facilitated by the conjugation of AuNPs with RNA probes (RNAP) via Au–S bonds, which align in a tail-to-tail fashion onto the target RNA. When miRNA-148a is introduced, a sandwich hybridization reaction is triggered between the AuNP–RNAP conjugates and targets, resulting in changes in the SPR absorption band, microscopic distribution and macroscopic color of the AuNP solution. Following this principle, this colorimetric method is able to quantitatively detect miRNA-148a at nanomolar level with a limit of ∼1.9 nM, and exhibits high sensitivity and selectivity by a low-cost UV–vis spectrometer or even the naked eye. Moreover, the AuNP network materials with a characteristic sharp ‘melting transition’ provide significant guidance for the reusability of DNA or RNA biosensors.

3,4:9,10-perylene tetracarboxylic acid-modified zinc ferrite with the enhanced peroxidase activity for sensing of ascorbic acid

3,4:9,10-perylene tetracarboxylic acid (PTCA) modified litchi-like zinc ferrite (ZnFe2O4) was prepared by a simple hydrothermal method and was found to possess the enhanced peroxidase-like activity. Under the catalysis of PTCA-ZnFe2O4, the colorless colorimetric substrate 3,3′,5,5′-tetramethylbenzidine (TMB) was rapidly oxidized by H2O2 and fast turned into blue color. Comparatively, the peroxidase-like activity of PTCA-ZnFe2O4 nanocomposites is higher than that of pure ZnFe2O4. In addition, it is hydroxyl radical that plays the key role in the process of catalysis reaction, which verified by fluorescent probe. On the basis of the higher peroxidase-like activity of PTCA-ZnFe2O4, a simple colorimetric biosensor platform has been proposed for detection of ascorbic acid (AA) in the linear range of 1−10 μM with the detection limit of 0.834 μM.

An unmodified gold nanorods-based DNA colorimetric biosensor with enzyme-free hybridization chain reaction amplification

A novel and simple colorimetric biosensor was developed by combining the unique optical properties of unmodified gold nanorods (AuNRs) with the amplification strategy of hybridization chain reaction (HCR), which was capable of detecting DNA sensitively and selectively. The detection mechanism is based on the dispersion/aggregation of AuNRs under the high concentration of salt. When target DNA introduces, the hybridization of hairpin DNA is triggered and a nicked double-helix DNA as HCR product forms which sticks tightly with AuNRs through a strong electrostatic adsorption and protects AuNRs from aggregation in high salt concentration condition. When no target DNA appears, AuNRs undergo aggregation due to the weak protection of hairpin DNA. The approach is able to detect target DNA in a range of 0–60 nM with a detection limit of 1.47 nM and exhibits high selectivity to distinguish fully matched and single-base mismatched DNA. Results demonstrate this method is label-free, modification-free, and enzyme-free, which holds great promise for routine sensing applications.

Digital camera-based lipase biosensor for the determination of paraoxon

This work is focused on construction of a biosensor containing unique bacterial homogenate with high lipase activity and colorimetric type of assay where camera of a smartphone was chosen as a detector. The biosensor was constructed as a tool of lipase inhibitors and paraoxon served as a representative analyte inhibiting the lipase.Psychrophilic strains of bacteria isolated from in Antarctica were tested and the best isolate P4368 having huge lipase activity was chosen. Tween assay was performed as a standard method for lipase activity determination and indoxylacetate served as a substrate of lipase measurable by smartphone camera and R, G and B color channels digital analysis. Bacteria were homogenized and immobilized on polyvinylidene difluoride membrane and indoxylacetate was immobilized in the proximity of the homogenate. Paraoxon ethyl was analyzed by the standard method and by the camera-based biosensor.The biosensor-based assay was found to determine paraoxon with limit of detection 3.72 × 10−8 mol/l and IC50 value for paraoxon was 4.00 × 10-6 mol/l. A volume 5 μl of sample was sufficient for the assay and the sample was applied directly without any processing.In a conclusion, a simple colorimetric biosensor for the determination of venomous compounds like organophosphorus pesticides and nerve agents was constructed and promising analytical parameters were received during its characterization.

CoxFe3−xO4 hierarchical nanocubes as peroxidase mimetics and their applications in H2O2 and glucose detection

A facile approach was proposed for the synthesis of hierarchical CoxFe3−xO4 (CF) nanocubes, using Prussian Blue (PB) as precursor. Then, an efficient and simple colorimetric biosensor for H2O2 and glucose was fabricated using CF nanocubes as peroxidase mimetic.