Strategy For Colorimetric Detection Research Articles

Au@Fe3O4 Nanoparticle-Based Colorimetric Aptasensor for Noninvasive Screening of Colorectal Cancer via Detection of Parvimonas micra.

Colorectal cancer (CRC) is a common malignancy requiring early screening to improve patient outcomes. Current screening methods such as colonoscopy and fecal occult blood tests have several limitations including high cost, poor specificity, invasiveness, and inconvenience. Recent research has identified specific bacterial communities associated with CRC, notably Parvimonas micra (P. micra), which serves as a biomarker for early screening and diagnosis owing to its accumulation in the malignant tissues and feces of CRC patients. Herein, we employed the whole-bacterium systematic evolution of ligands by the exponential enrichment (SELEX) method to isolate high-affinity aptamers against P. micra using 17 selection cycles. These aptamers were subsequently bound to Au@Fe3O4 nanoparticles, and the interaction of P. micra and aptamers inhibited the peroxidase-like activity of Au@Fe3O4 nanoparticles, thereby blocking the 3,3',5,5'-tetramethylbenzidine (TMB) chromogenic reaction and resulting in a measurable reduction in absorbance. This colorimetric detection strategy demonstrated a linear response across a range of 100-108 CFU/mL for P. micra with a limit of detection of 11 CFU/mL. Using a colorimetric aptasensor, we assessed the abundance of P. micra in clinical fecal samples and found significantly higher levels in the feces of CRC patients as compared to that of healthy individuals, which was consistent with the quantitative polymerase chain reaction results. This study therefore represents the first successful identification of an aptamer with high affinity and specificity for P. micra, leading to the development of a highly specific and sensitive aptasensor for its detection. The presented approach has a significant potential for CRC screening and diagnosis.

Visual detection of kanamycin with functionalized Au nanoparticles.

A simple and rapid colorimetric detection strategy, based on hydrogen bond identification of 6-thioguanine (6-TG) functionalized Au nanoparticles (AuNPs), is proposed for highly selective and sensitive determinationof kanamycin (KA). In this strategy, the hydrogen bond interaction between 6-TG and kanamycin induces AuNPs to agglomerate, with a consequent color change of AuNPs from wine red to purple or even blue. The kanamycin concentrations can be quantified by employing UV-vis spectrophotometer. The results display that kanamycin concentrations (0.005 to 18µM) are linearly related to A620/A520 (the absorbance ratio of 620nm and 520nm) with a LOD of 1.8nM and a LOQ of 5.9nM (S/N = 3). This strategy also reveals a high degree of selectivity among a series of common interfering species. Moreover, the strategy can be employed to detect trace amounts of kanamycin in real-life samples, and it shows satisfying resultscompared with high performance liquid chromatography. In general, this developed strategy is facile and inexpensive without the need for complex processing procedures and expensive instruments. In addition, this work may further exploit detection strategies for other organic contaminants, as well as make a strong contribution to the development of the colorimetric method.

Innovative Colorimetric NQO1 Detection Strategy via Substrate Competitive and Biomimetic Cascade Reactions with a Highly Active NADH Oxidase Mimic.

NAD(P)H: quinone oxidoreductase-1 (NQO1) plays critical roles in antioxidation and abnormally overexpresses in tumors. Developing a fast and sensitive method of monitoring NQO1 will greatly promote cancer diagnosis in clinical practice. This study introduces a transformative colorimetric detection strategy for NQO1, harnessing an innovative competitive substrate mechanism between NQO1 and a new NADH oxidase (NOX) mimic, cobalt-nitrogen-doped carbon nanozyme (CoNC). This method ingeniously exploits the differential consumption of NADH in the presence of NQO1 to modulate the generation of H2O2 from CoNC catalysis, which is then quantified through a secondary, peroxidase-mimetic cascade reaction involving Prussian blue (PB) nanoparticles. This dual-stage reaction framework not only enhances the sensitivity of NQO1 detection, achieving a limit of detection as low as 0.67 μg mL-1, but also enables the differentiation between cancerous and noncancerous cells by their enzymatic activity profiles. Moreover, CoNC exhibits exceptional catalytic efficiency, with a specific activity reaching 5.2 U mg-1, significantly outperforming existing NOX mimics. Beyond mere detection, CoNC serves a dual role, acting as both a robust mimic of cytochrome c reductase (Cyt c) and a cornerstone for enzymatic regeneration, thereby broadening the scope of its biological applications. This study not only marks a significant step forward in the bioanalytical application of nanozymes but also sets the stage for their expanded use in clinical diagnostics and therapeutic monitoring.

A colorimetric platform for sensitive sensing of Hg2+ and S2− based on Se-AuNPs with Hg2+-activated peroxidase-like activity

Herein, the selenium (Se) modified gold nanoparticles (Se-AuNPs) was synthesized using cerium doped carbon dots (Ce-CDs) as a reducing agent and template. As desired, Se-AuNPs displays enhanced peroxidase (POD)-like activity in the presence of Hg2+. The mechanism for the enhanced activity was attributed to the increased affinity between Se-AuNPs-Hg2+ and the substrate, in which Se and Au elements have a strong binding capacity to Hg2+, forming Hg–Se bonds and Au–Hg amalgam to generate more ·OH. This POD-like activity of Se-AuNPs-Hg2+ correlates with the colorimetric reaction by the catalytic reaction between 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2. The oxidation of TMB was completely inhibited by the introduction of the reductive S2−. Based on the above findings, a strategy for the colorimetric detection of Hg2+ and S2− by Se-AuNPs was established with linear ranges of 0.33–66 μg/L and 0.625–75 μg/L, and low detection limits of 0.17 μg/L and 0.12 μg/L (3.3 δ/k), respectively. When the colorimetric probes for detection of Hg2+ and S2− was applied in environmental water samples, the recoveries were in the range of 90.3–108.0 %. This method will provide a new idea for the colorimetric detection strategy of Hg2+ due to the strong interaction between Hg and Se.

A new strategy for colorimetric detection and removal of butyl xanthate in mineral processing wastewater: Based on a novel nanozyme of Ag@Fe3O4-MnO2

Butyl xanthate (BX) is a commonly used sulfide collector in the froth flotation process. However, its potential toxicity would cause environmental problems if not handled properly or in case of leaks. Therefore, it is important to establish efficient methods for detecting and removing BX from mineral processing wastewater. In this study, a new nanozyme named Ag@Fe3O4-MnO2 was synthesized using a two-step hydrothermal process. This nanozyme, exhibiting both oxidase and catalase-mimicking properties, was successfully used in a multi-color change detection method for BX. Additionally, Ag@Fe3O4-MnO2 activated persulfate (PS) to break down BX. Under the optimal conditions of 2.0 mg/L catalyst dosage, 2.0 mM PS, and initial pH 7.82, more than 97.17 % of BX was degraded in the simulant wastewater in 30 min. Overall, this study offers valuable new insights into the detection and removal of BX, expanding the potential application of nanozymes in the environmental field.

Hg2+-enhanced oxidase-like activity of platinum nanoparticles immobilized on porphyrin-based porous organic polymer for the colorimetric detection and removal of Hg2.

Porphyrin-based porous organic polymer (POP) with uniformly immobilized platinum nanoparticles (Pt NPs) were designed and synthesized, and it was demonstrated that such nanocomposites (Pt/POP) have oxidase-like activity. Surprisingly, Hg2+ significantly enhanced the oxidase-like activity of Pt/POP. The enhancement was attributed to the capture of Hg2+ by the thioether group in Pt/POP and the subsequent redox reaction of Hg2+ with Pt NPs, accelerating the electron transfer. In the presence of Hg2+, Pt/POP catalyzed the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to turn blue rapidly and changed its absorbance at 652nm. Based on this, a fast-response colorimetric sensor was constructed for the sensitive detection of Hg2+ with a linear range of 0.2-50μM and a detection limit of 36.5nM. Importantly, Pt/POP can be used as an adsorbent for the efficient removal of Hg2+ with a removal efficiency as high as 99.4%. This work provides a valuable strategy for colorimetric detection and efficient removal of Hg2+.

Development of tumor marker detection and tumor treatment based on silver nanozymes

Nanomaterials with intrinsic enzyme activity (nanozymes) have been widely used as artificial enzymes in biomedicine, especially in tumor diagnosis and treatment. Herein, a kind of water-soluble silver nanozyme (Ag@GQD) was developed with a simple method, which showed two enzymatic activities (peroxidase and oxidase-like activity). Based on the excellent catalytic performance of oxidase-like activity, a simple and highly sensitive colorimetric detection strategy for glutathione (GSH) was established. What’s more, after absorbing DOX, Ag/DOX@GQD could realize the combined treatment of reactive oxygen species and chemotherapy. In conclusion, this study provided evidences that Ag@GQD is effective in tumor diagnosis and treatment, which provided new ideas for exploring nanozymes based on the integration of diagnosis and treatment.

Synthesis of Two-Dimensional (Cu-S)n Metal-Organic Framework Nanosheets Applied as Peroxidase Mimics for Detection of Glutathione.

Facilely synthesized peroxidase-like nanozymes with high catalytic activity and stability may serve as effective biocatalysts. The present study synthesizes peroxidase-like nanozymes with multinuclear active sites using two-dimensional (2D) metal-organic framework (MOF) nanosheets and evaluates them for their practical applications. A simple method involving a one-pot bottom-up reflux reaction is developed for the mass synthesis of (Cu-S)n MOF 2D nanosheets, significantly increasing production quantity and reducing reaction time compared to traditional autoclave methods. The (Cu-S)n MOF 2D nanosheets with the unique coordination of Cu(I) stabilized in Cu-based MOFs demonstrate impressive activity in mimicking natural peroxidase. The active sites of the peroxidase-like activity of (Cu-S)n MOF 2D nanosheets were predominantly verified as Cu(I) rather than Cu(II) of other Cu-based MOFs. The cost-effective and long-term stability of (Cu-S)n MOF 2D nanosheets make them suitable for practical applications. Furthermore, the inhibition of the peroxidase-like activity of (Cu-S)n MOF nanosheets by glutathione (GSH) could provide a simple strategy for colorimetric detection of GSH against other amino acids. This work remarkably extends the utilization of (Cu-S)n MOF 2D nanosheets in biosensing, revealing the potential for 2D (Cu-S)n MOFs.

A simply visual and rapidly colorimetric detection of Hg2+ in cosmetics based on gold nanoparticles modified by sulfadiazine

Mercury is one of the most potentially toxic metals, which is much harmful to the human health. Therefore, It is great important to detect mercury ions. In this work, proposed was a simply visual and rapidly colorimetric strategy for detection of Hg2+ based on gold nanoparticles (AuNPs) modified with sulfadiazine (SDZ) and characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD), UV–vis. The solution color from red to blue gray with increasing Hg2+ concentration resulted from the aggregation of AuNPs with fine anti-interference. The limit of detection (LOD) is 1.0 μg·mL-1 by the naked eye, and 0.071 μg·mL-1 by UV–vis spectroscopy with the good linear relationship (R2 = 0.994) indicating that AuNPs modified with sulfadiazine could be used for the quantitative determination of Hg2+. The selectivity of SDZ-AuNPs detection system for Hg2+ is much more excellent compared with other interferents in cosmetics, which exhibit this sensor could be successfully applied to detect Hg2+ in real samples.

Toxic Ag+ detection based on Au@Ag core shell nanostructure formation using Tannic acid assisted synthesis of Pullulan stabilized gold nanoparticles

Herein, a sensitive colorimetric detection strategy is proposed for Ag+ detection based on the use of environmentally friendly synthesis of gold nanoparticles (AuNPs), at room temperature, using (tannic acid, TA), as the reductant and pullulan (PUL) as stabilizing agent. The colloidal solution (TA/PUL-AuNPs), at the optimal synthesis conditions, showed maximum absorbance at 529 nm with a berry red color. TEM and FESEM validated that the particles are spherical and monodispersed, while other characterization results elucidated the role of pullulan in the nano-synthesis. Ag+ addition to the probe (TA/PUL-AuNPs), pH 11, resulted in naked-eye color changes, owing to Au@Ag core shell nanostructure formation. Further, the added Ag+ is reduced to AgNPs, on the surface of the TA/PUL-AuNPs probe. A hypsochromic shift in the absorption maximum, from 529 to 409 nm was observed, while (AAg+-Abl)@409 nm exhibited linearity with Ag+ concentrations, from 0.100 to 150 µM. The estimated limit of detection was 30.8 nM, which is far lower than the acceptable limit of 0.930 µM from the regulatory agency. The TA/PUL-AuNPs probe was further tested for Ag+ detection in lake water samples, and it displayed satisfactory detection performances for real sample applications.

Development of aptamer based colorimetric assay for whole blood glycated hemoglobin (HbA1c) estimation using gold nanoparticles

Thiol-modified aptamer oligonucleotides containing gold nanoparticles (G@NPs) bound to glycated hemoglobin (HbA1c) with high affinity in whole blood samples. Aptamer thiol groups enhanced the stability of aptamers adsorbed on the surface of G@NPs. A detection strategy was used to visually confirm the presence of HbA1c and the absorbance of the colored compounds at selected wavelengths. Modified G@NPs are used in many colorimetric detection strategies due to their high extinction coefficient and strongly distance-dependent optical properties. In the present study, as the target analyte reports a method to prepare gold nanoparticle-bound purple aptamer aggregates that rapidly collapse into bluish red dispersed nanoparticles upon binding of HbA1c. HbA1c was detected in unpretreated whole blood after dilution at pH 7.4 and with UV-VIS double beam spectrophotometer with a lower limit of detection (LOD) (0.1 μM) and a much broader linear detection range (0.1 μM–100 μM). This current colorimetric method provides a rapid (7 min), accurate and high determination of whole blood HbA1c with minimal interference from uric acid, bovine serum albumin, hemoglobin, and glucose. The lower detection limit and broader linearity of aptamer-bound G@NPs hybrids improve the accuracy and precision of HbA1c measurements.

Dual-amplification colorimetric detection of bisphenol A based on catalytic hairpin assembly and DNAzyme-caused fragment self-assembly hybridization chain reaction.

An efficient and innovative strategy for colorimetric detection of bisphenol A (BPA) is shown here based on target-induced catalytic hairpin assembly (CHA) and DNAzyme-caused fragment self-assembly hybridization chain reaction (HCR). BPA can bind with its aptamer hairpin to trigger CHA, thus forming Y-shaped DNA nanostructures with an enzyme-strand (E-DNA) tail. Subsequently, the E-DNA can cyclically cleave the substrate hairpin, generating many fragments which can cause self-assembly HCR to form long strand DNA. Finally, the formed long strand DNA can hybridize with short single strand DNA on AuNPs, causing the color change of AuNPs from red to blue. Six important detection conditions of the proposed aptasensor were optimized. Under optimal conditions, the biosensor has high sensitivity for BPA detection at concentrations ranging from 0.8 pM to 500 pM and the detection limit is as low as 0.2 pM, providing a promising prospective ultrasensitive detection of BPA.

An ingenious cellulose membrane sensor design strategy for colorimetric detection of Ag+/Hg2+ based on redox reaction

This paper describes an ingenious cellulose membrane sensor design strategy for colorimetric detection of Ag+/Hg2+ based on redox reaction. The colorless 3,3′,5,5′-tetramethylbenzidine (TMB) can be oxidized to blue oxidized TMB (oxTMB) when exposed to Ag+/Hg2+ that with strong oxidizing properties. Based on this phenomenon, TMB can be design as a colorimetric probe for Ag+/Hg2+, and the reaction mechanism and sensing performance of TMB as Ag+/Hg2+ were explored. In addition, the TMB probe-immobilized cellulose membranes (TMB@CMs) were developed by combining TMB with high-purity cellulose membranes (CMs) carrier with porous and polyhydroxy structures. As a platform for probe immobilization, TMB@CMs can effectively improve colorimetric sensing response and stability of TMB. The colorimetric mechanism of TMB@CMs was investigated including in situ oxidation of TMB and immediate immobilization of oxTMB. The experimental results showed that the visual detection limit (VLOD) of Ag+/Hg2+ was 10 μM when TMB was used as colorimetric probe, while the VLOD of the TMB@CMs was 1 μM. In addition, TMB@CMs had good reusability and stability. Through the analysis of SEM, EDS and XPS results, the mechanism of TMB colorimetric detection of Ag+/Hg2+ was that blue oxTMB and Ag/Hg elementals were generated by redox reaction between them. This study not only verified the feasibility of TMB as an Ag+/Hg2+ colorimetric probe, but also designed a probe-immobilized cellulose membrane model with convenient operation, uniform color development and stable color, which effectively improved the colorimetric sensing response and stability.

Sunlight‐assisted environmentally-friendly synthesis of graphene-like δ-MnO2 nanosheets for colorimetric sensing

Manganese dioxide (MnO2) has received increasing attention for sensing applications due to its versatile properties. Thus, there is a need to develop a facile strategy to synthesize MnO2. Herein, a template-free, green, photoinduced synthesis method for graphene-like δ-MnO2 nanosheets (GLMNS) was developed using potassium permanganate as the precursor. In the proposed synthesis strategy, trace ethanol was employed as the electron acceptor to direct the template-free, one-step growth of dispersed ultrathin multi-layered GLMNS under sunlight irradiation, without requiring another reducing agent or surface stabilizer. As a proof of concept, as-synthesized GLMNS were employed as a homogeneous nanocatalyst and signal-reporting material for two different sensitive colorimetric detection methods for triclosan and total antioxidant capacity. The two colorimetric methods were also evaluated by detecting triclosan in real sewage and silt samples, as well as the total antioxidant capacity of human blood serum. This study indicates that using sunlight irradiation to prepare two-dimensional MnO2 nanosheets is a promising strategy and also offers promising homogeneous MnO2-based colorimetric detection strategies. As a result of this work, we may be able to prepare MnO2 nanosheets in a new way, and it is also possible that GLMNS may be a good candidate for other applications, such as pseudocapacitive and adsorbent.

CunO/Au heterostructure dendrimer anchored on Cu foam as dual functional catalytic nanozyme for glucose sensing by enzyme mimic cascade reaction.

Multifunctional catalytic performance plays a crucial role in bio-applications through the diversity and durability of artificial nanozymes. An effective synergy with sufficient accessible active sites and high specific surface area is a challenge for composite catalysts, especially to avoid uncontrollable aggregation and structural instability. Here, we fabricated a CunO/Au heterostructure dendrimer on copper foam (CunO/Au HD/CF) as dual functional catalytic nanozyme to achieve enzyme mimic cascade reactions for efficient colorimetric analysis. A highly porous CF skeleton-based CuO nanowire array (CuO NWA) with a large specific surface area supported an efficient load capacity to assemble sufficient CunO/Au HD by electrodeposition. The bimetallic Au-Cu nanozyme successfully achieved an oxidase-like and peroxidase-like cascade catalysis by a target-responsive sensing mechanism. Due to the confirmed catalytic performance of selectivity, anti-interference ability, and reproducibility, aCunO/Au HD/CF-based quantitative analytical method was developed for glucose detection with a wide linear range and considerable detection limit of 8.4μM. The robust nonenzymatic catalytic strategy for colorimetric detection not only confirmed the dual functional catalytic activity of CunO/Au HD/CF, but also showed great potential for applications in clinical diagnostics and biochemical analysis.

A colorimetric detection strategy and micromotor-assisted photo-Fenton like degradation for hydroquinone based on the peroxidase-like activity of Co3O4–CeO2 nanocages

Co3O4–CeO2 micromotors were fabricated and the colorimetric detection and micromotor-assisted photodegradation capability were studied.

Nanozyme-Based Detection of Alkaline Phosphatase

Herein, a colorimetric detection strategy for alkaline phosphatase (ALP) activity was established based on an Fe-doped carbon-based nanozyme. By doping Fe into a Zn MOF and introducing dicyandiamid...

Gold nanostar@graphene quantum dot as a new colorimetric sensing platform for detection of cysteine

We here report on a facile method for preparation of gold nanostar-graphene quantum dot (AuNS@GQD) composite, which produces highly active surfactant-free AuNSs. The etching reaction of this composite with Na2SO3 was studied and used as a new sensing strategy for colorimetric detection of nM levels of cysteine. In the presence of Na2SO3, the shape of AuNSs changes to sphere-like nanoparticles, leading to a distinct color change of solution from light green to indigo. This phenomenon results from the redox reaction of Au atoms at the apexes and sharp corners of the NSs with oxygen which leads to the formation of [Au(SO3)2]3−. Our studies indicated that the stars with larger sizes show greater activity in etching reaction since they have more branches and sharper tips. Due to the strong coordination between Au and thiols, pre-added cysteine can protect the AuNSs from SO32− etching and so the shape and the color of AuNSs remain unaltered. This anti-etching effect was used for the detection of cysteine with the detection limit as low as 0.35 nM. The developed colorimetric sensor was validated by HPLC method and applied for analysis of human plasma samples.

Construction of Bio-Nano Interfaces on Nanozymes for Bioanalysis.

Nanomaterials with enzyme-like activity (nanozymes) have been of great interest in broad applications ranging from biosensing to biomedical applications. Despite that much effort has been devoted to the development of the synthesis and applications of nanozymes, it is essential to understand the interactions between nanozymes and most commonly used biomolecules, i.e., avidin, streptavidin (SA), bovine serum albumin (BSA), immunoglobulin G (IgG), and glutathione (GSH), yet they have been rarely explored. Here, a series of bio-nano interfaces were constructed through direct immobilization of proteins on a variety of iron oxide and carbon-based nanozymes with different dimensions, including Fe3O4 nanoparticles (NPs, 0D), Fe3O4@C NPs (0D), Fe3O4@C nanowires (NWs, 1D), and graphene oxide nanosheets (GO NSs, 2D). Such interfaces enabled the modulation of the catalytic activities of the nanozymes with varying degrees, which allowed a good identification of multiplex proteins with high accuracy. Given the maximum inhibition on Fe3O4@C NP by BSA, we established molecular switches based on aptamer and toehold DNA, as well as Boolean logic gates (AND and NOR) in response to both DNA and proteins. Also importantly, we developed an on-particle reaction strategy for colorimetric detection of GSH with ultrahigh sensitivity and good specificity. The proposed sensor achieved a broad dynamic range spanning 7 orders of magnitude with a detection limit down to 200 pg mL-1, which was better than that of an in-solution reaction-based biosensor by 2 orders of magnitude. Furthermore, we explored the mechanisms of the interactions at bio-nano interfaces by studying the interfacial factors, including surface coverage, salt concentration, and the curvature of the nanozyme. This study offered new opportunities in the elaborate design and better utilization of nanozymes for bioanalysis in clinical diagnosis and in vivo detection.

Online Monitoring Strategies for Colorimetric Detection of Cadmium Ions and pH Based on Gold Nanomaterials with a Low-Cost Color Sensor

Gold triangular nanoplates (AuTNPs) and gold nanorods (AuNRs) have been widely used in colorimetric sensing due to their shape-dependent localized surface plasmon resonance properties. Herein, we report new colorimetric detection strategies based on a low-cost RGB colorimetry system equipped with an industrial-grade color sensor and provide two demonstrations for the potential applications. The first is the online detection of cadmium ions (Cd²⁺) through the Cd²⁺-promoted etching of glutathione-stabilized AuTNPs that was initialized by H₂O₂ and iodide. For the first time, the etching time corresponding to the inflection point of the first derivative of the Red channel transmission curve was used for calibration. The method was finally applied in the detection of Cd²⁺ in fortified rice samples. In the second demonstration, the RGB values continuously acquired using the instrument were converted to HSV (hue, saturation, and value) space, which was successfully employed in pH detection via etching of AuNRs. Importantly, the overaged AuNRs with poor homogeneity could be discerned by the method at the beginning of analysis, which is helpful in achieving reliable measurements. Our results suggest that integration of the low-cost portable instrument and the new strategies has the promising potential for sensitive, accurate, precise, and good-linearity detection.