Rapid colorimetric determination of dopamine based on the inhibition of the peroxidase mimicking activity of platinum loaded CoSn(OH)6 nanocubes

Nanozyme-based sensing of dopamine using cobalt-doped hydroxyapatite nanocomposite from waste bones

Dopamine is one of the most important neurotransmitters and plays a crucial role in various neurological, renal, and cardiovascular systems. However, the abnormal levels of dopamine mainly point to Parkinson's, Alzheimer's, cardiovascular diseases, etc. Hydroxyapatite (HAp), owing to its catalytic nature, nanoporous structure, easy synthesis, and biocompatibility, is a promising matrix material. These characteristics make HAp a material of choice for doping metals such as cobalt. The synthesized cobalt-doped hydroxyapatite (Co-HAp) was used as a colorimetric sensing platform for dopamine. The successful synthesis of the platform was confirmed by characterization with FTIR, SEM, EDX, XRD, TGA, etc. The platform demonstrated intrinsic peroxidase-like activity in the presence of H2O2, resulting in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The proposed sensor detected dopamine in a linear range of 0.9-35 μM, a limit of detection of 0.51 µM, limit of quantification of 1.7 µM, and an R2 of 0.993. The optimization of the proposed sensor was done with different parameters, such as the amount of mimic enzyme, H2O2, pH, TMB concentration, and time. The proposed sensor showed the best response at 5 mg of the mimic enzyme, pH 5, 12 mM TMB, and 8 mM H2O2, with a short response time of only 2 min. The fabricated platform was successfully applied to detect dopamine in physiological solutions.

Synthesis of Ag nanoparticles for selective dual detection of glutathione and dopamine using N, N-dimethyl-p-phenylenediamine mediated colorimetric probe

We report a simple and easy method to synthesize Ag nanoparticles (Ag NPs) and demonstrate its potential for the detection of glutathione (GSH) and dopamine (DA) via colorimetric assay. The Ag NPs were found to be monodispersed and spherical with a size of 5 ± 2 nm. The X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM) investigations revealed the formation of crystalline Ag NPs. The colour of N, N-dimethyl-p-phenylenediamine assay changed from dark pink to colourless when the concentration of GSH was increased from 1 to 40 μM. Notably, the suspension colour changed from dark pink to blue when a similar set of experiments were performed with DA. The UV/Visible and interference experiments of Ag NPs exhibited excellent sensitivity and selectivity against both GSH and DA even after the addition of 40 μM of different interference biomolecules. The calculated limit of detection (LOD) was 141 and 245 nM for GSH and DA, respectively. The real-time analysis with serum samples showed satisfactory recovery percentages of >95 and 80-90% for GSH and DA, respectively. Hence, the Ag NPs reported here have huge potential to serve as a sensitive and selective colorimetric sensor for the detection of GSH and DA for diverse applications ranging from catalysis to cancer therapy and theranostics.

Nitrocellulose membranes in situ grown with Prussian blue nanoparticles as stable nanozyme pads for colorimetric detection of dopamine

Prussian blue (PB) is a typical peroxidase mimic with simple preparation, low cost and high eco-friendliness, but it still has drawbacks of poor stability (e.g., decomposition in aqueous dispersions) and intrinsic optical interference (e.g., high extinction coefficient over a wide wavelength range) in colorimetric assays. Herein, we used nitrocellulose (NC) membranes as synthesis hosts of PB nanoparticles (NPs) to develop a new type of three-dimensional (3D) porous nanozyme pad. By means of an in situ synthesis route, PB NPs were uniformly grown on the surfaces of the fiber scaffolds with desirable stability, which also avoided signal interference from PB NPs owing to the easy handling of the pads in a quantitative solid state. The pads showed significant peroxidase-mimicking activity toward the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with the output of colorimetric signals. Based on the reduction of oxidized TMB (oxTMB) by dopamine (DA), the pads were exploited for simple and quantitative colorimetric detection of DA with a limit of detection (LOD) of 0.59 μM and a satisfactory accuracy for analysis of real human urine samples. This is the first attempt at exploiting NC membranes as the synthesis hosts to develop nanozyme pads, which solves the above drawbacks of traditional PB-based peroxidase mimics and has promise for various colorimetric bioanalyses, given the structural benefits of NC membranes and their broad applications in biosensors.

Peroxidase-mimicking poly-L-lysine/alginate microspheres with PtS2 nanoparticles for image-based colorimetric assays

Morphologically controllable ALG@ε-PL water-in-water microspheres were successfully prepared using a two-step method through precise control of the two-phase flow rate. Through further interfacial coagulation, the ALG@ε-PL microspheres possess a dense surface structure and good permeability. The sensor based on PtS₂@ALG@ε-PL microspheres was constructed by encapsulating PtS₂ nanosheets with peroxidase-like properties in ALG@ε-PL water-in-water microspheres. PtS₂ nanosheets catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂ to produce blue oxTMB. The strong reducing property of the model analyte dopamine (DA) can reduce oxTMB, thus causing the blue color to fade and successfully achieving colorimetric detection of DA. The linear range of the assay is 2.0-200 μM, and the detection limit is 0.22 μM. The recoveries of DA in serum samples were determined by the spik method, and the results were reproducible.

Balancing "on" and "off" response of hydroxyl groups to a nanozyme-catalyzing system for the construction of an ultra-sensitive and selective "signal-on" detection platform for dopamine

Targeting the functional groups present in analytes by nanozyme-catalyzed systems is a promising strategy to construct sensitive and selective platforms for the sensing of specific analytes. Herein, various groups (-COOH, -CHO, -OH, and -NH₂) on benzene were introduced in an Fe-based nanozyme system with MoS₂-MIL-101(Fe) as the model peroxidase nanozyme, H₂O₂ as the oxidizing agent, and TMB as the chromogenic substrate, and the effects of these groups at both a low concentration and high concentration were further investigated. It was found that the hydroxyl group-based substance catechol showed an "on" effect at a low concentration to increase the catalytic rate and enhance the absorbance signal, whereas an "off" effect at a high concentration with a decreased absorbance signal. Based on these results, the "on" mode and "off" mode for the biological molecule dopamine, a type of catechol derivative, were proposed. In the control system, MoS₂-MIL-101(Fe) catalyzed the decomposition of H₂O₂ to produce ROS, which further oxidized TMB. In the "on" mode, the hydroxyl groups of dopamine could combine with the Fe(iii) site of the nanozyme to lower its oxidation state, resulting in higher catalytic activity. In the "off" mode, the excess dopamine could consume ROS, which inhibited the catalytic process. Under the optimal conditions, by balancing the "on" and "off" modes, the "on" mode for the detection of dopamine was found to have better sensitivity and selectivity. The LOD was as low as 0.5 nM. This detection platform was successfully applied for the detection of dopamine in human serum with satisfactory recovery. Our results can pave the way for the design of nanozyme sensing systems with sensitivity and selectivity.

Peroxidase-like phosphate hydrate nanosheets bio-synthesized by a marine Shewanella algae strain for highly sensitive dopamine detection

The sensitive and rapid detection of dopamine (DA) is of great significance for early diagnosis of related diseases. Current detection strategies of DA are time-consuming, expensive and inaccurate, while biosynthetic nanomaterials were considered highly stable and environment friendly, which were promising on colorimetric sensing. Thus, in this study, novel zinc phosphate hydrate nanosheets (SA@ZnPNS) biosynthesized by Shewanella algae were designed for the detection of DA. SA@ZnPNS showed high peroxidase-like activity which catalyzed the oxidation reaction of 3,3',5,5'-tetramethylbenzidine in the presence of H₂O₂. Results showed that the catalytic reaction of SA@ZnPNS followed Michaelis-Menton kinetics, and catalytic process conformed to ping-pong mechanism with chief active species of hydroxyl radicals. The colorimetric detection of DA in human serum samples was performed based on SA@ZnPNS peroxidase-like activity. The linear range of DA detection was 0.1-40 μM, and the detection limit was 0.083 μM. This study provided a simple and practical method for the detection of DA and expanded the application of biosynthesized nanoparticles to biosensing fields.

Core-shell Au-Ag nanoparticles as colorimetric sensing probes for highly selective detection of a dopamine neurotransmitter under different pH conditions

Dopamine (DA) is a vital biomarker for the early diagnosis of dopaminergic dysfunction; therefore, it is important to establish a direct and selective detection tool for DA neurotransmitters. This work reports facilely synthesized Au-Ag core-shell nanoparticles (Au@Ag NPs) as colorimetric sensing probes for highly selective detection of the DA neurotransmitter. Our sensing strategy is based on DA-mediated aggregation of the Au@Ag NPs, which can show a distinct color transition from yellow to greenish grey. With the increase of pH from 6 to 10, the response time of colorimetric transition was significantly reduced by a factor of 10 and the limit of detection (LOD) for DA by a spectroscopic device was estimated to be 0.08 μM. Notably, optimized sensing probes of Au@Ag NPs at pH 10 demonstrated an excellent selectivity to DA against various interfering components (including catecholamines (norepinephrine and epinephrine), lysine, glutamic acid, glucose, or metal ions). Our sensing system also exhibited the reliable detection of DA in spiked human serum with the relative standard deviation lower than 4.0%, suggesting its possible application to the direct detection of DA in biological fluids.

A dual-recognition MIP-ECL sensor based on boric acid functional carbon dots for detection of dopamine

We report a molecularly imprinted polymer electrochemiluminescence (MIP-ECL) sensor with dual recognition effects on dopamine (DA). Boric-acid-functionalized carbon dots (B-CDs) with good ECL performance at - 2.0 V (vs. Ag/AgCl) were prepared and immobilized on a glassy carbon electrode (GCE). The MIP was then introduced via electropolymerization using o-phenylenediamine (OPD) as a functional monomer and DA as a template molecule to fabricate the MIP-ECL sensor. The cavities in the MIP after elution were used to capture the target molecular DA. The affinity of boric acid of B-CDs to the cis-diol of DA, as well as the special recognition of MIP, provides dual recognition effects on DA. The selective readsorption of DA onto the sensor leads to the ECL quenching of B-CDs. The quenching effect was used to detect DA from 1.0 × 10^-9 to 1.0 × 10^-5 mol·L^-1 with a detection limit of 2.1 × 10^-10 mol·L^-1. The dual recognition caused the MIP-ECL sensor exhibiting excellent selectivity and sensitivity toward  DA. The sensor was successfully used to determine DA in real samples.

Laccase-mimicking Mn-Cu hybrid nanoflowers for paper-based visual detection of phenolic neurotransmitters and rapid degradation of dyes

Background

Laccase-based biosensors are efficient for detecting phenolic compounds. However, the instability and high cost of laccases have hindered their practical utilization.

Results

In this study, we developed hierarchical manganese dioxide–copper phosphate hybrid nanoflowers (H–Mn–Cu NFs) as excellent laccase-mimicking nanozymes. To synthesize the H–Mn–Cu NFs, manganese dioxide nanoflowers (MnO₂ NFs) were first synthesized by rapidly reducing potassium permanganate using citric acid. The MnO₂ NFs were then functionalized with amine groups, followed by incubation with copper sulfate for three days at room temperature to drive the coordination interaction between the amine moieties and copper ions and to induce anisotropic growth of the petals composed of copper phosphate crystals, consequently yielding H–Mn–Cu NFs. Compared with those of free laccase, at the same mass concentration, H–Mn–Cu NFs exhibited lower K_m (~ 85%) and considerably higher V_max (~ 400%), as well as significantly enhanced stability in the ranges of pH, temperature, ionic strength, and incubation periods evaluated. H–Mn–Cu NFs also catalyzed the decolorization of diverse dyes considerably faster than the free laccase. Based on these advantageous features, a paper microfluidic device incorporating H–Mn–Cu NFs was constructed for the convenient visual detection of phenolic neurotransmitters, including dopamine and epinephrine. The device enabled rapid and sensitive quantification of target neurotransmitters using an image acquired using a smartphone.

Conclusions

These results clearly show that H–Mn–Cu NFs could be potential candidates to replace natural laccases for a wide range of applications in biosensing, environmental protection, and biotechnology.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01560-0.

SERS determination of dopamine using metal-organic frameworks decorated with Ag/Au noble metal nanoparticle composite after azo derivatization with p-aminothiophenol

A specific surface-enhanced Raman scattering (SERS) assay for dopamine (DA) based on an azo derivatization reaction is proposed for the first time by preparation of p-aminothiophenol (PATP)-modified composite SERS substrate, composed of metal-organic framework (MIL-101) decorated with Au and Ag nanoparticles. As the result, the SERS method for detection of the azo reaction between PATP and DA exhibits superior sensitivity, selectivity, and stability. A reasonable linearity in the range 10^-6 to 10^-10 mol∙L^-1 is achieved, and the limit of detection is 1.2 × 10^-12 mol∙L^-1. The reactive SERS assay is free from interference in complex physiological fluid. The feasibility of the proposed SERS method for the detection of DA levels in fetal bovine serum (FBS) samples and human serum samples is validated by HPLC-MS methods, displaying promising application potential in early disease diagnosis.

Template-Regulated Bimetallic Sulfide Nanozymes with High Specificity and Activity for Visual Colorimetric Detection of Cellular H2O2

For the past several decades, most of the research studies on nanozymes have been aimed at improving their catalytic activity and diversity; however, developing nanozymes with strong catalytic activity and great specificity remains a challenge. Herein, a simple and efficient template synthesis method was used to synthesize bimetallic sulfide nanoparticles, NiCo₂S₄ NPs, and prove that they have excellent peroxidase-like activity with good specificity. By regulating polyvinyl pyrrolidone (PVP) and hexadecyl trimethyl ammonium bromide as the templating agent, we have obtained the NiCo₂S₄ (PVP) NPs with a high Ni/Co ratio, thus exhibiting superior peroxidase activity. In addition, the NiCo₂S₄ NPs selectively catalyzed and oxidized colorless 3,3,5,5-tetramethylbenzidine (TMB). On being treated with H₂O₂, TMB turns blue while other substrates did not undergo the oxidation reaction under the same conditions, such as 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium (ABTS) and dopamine. The high specificity of NiCo₂S₄ NPs is due to the strong electrostatic driving coordination between negatively charged NiCo₂S₄ NPs and positively charged TMB. Due to the peroxidase activity of the developed NiCo₂S₄ NPs, a simple, low-cost, and reliable colorimetric method was established. Simultaneously, this method for in situ quantitative monitoring of H₂O₂ produced by MDA-MB-231 cells was also achieved. This study has provided a theoretical basis for the improvement of the activity and specificity of bimetallic sulfide nanozymes and may offer guidance for the further reasonable design of related materials.

Peroxidase-Like Platinum Clusters Synthesized by Ganoderma lucidum Polysaccharide for Sensitively Colorimetric Detection of Dopamine

The sensitive and selective detection of dopamine (DA) is very important for the early diagnosis of DA-related diseases. In this study, we reported the colorimetric detection of DA using Ganoderma lucidum polysaccharide (GLP) stabilized platinum nanoclusters (Pt_n-GLP NCs). When Pt₆₀₀-GLP NCs was added, 3,3’,5,5’-tetramethylbenzidine (TMB) was rapidly catalyzed and oxidized to blue oxTMB, indicating the peroxidase-like activity of Pt₆₀₀-GLP NCs. The catalytic reaction on the substrate TMB followed the Michaelis-Menton kinetics with the ping-pong mechanism. The mechanism of the colorimetric reaction was mainly due to the formation of hydroxyl radical (•OH). Furthermore, the catalytic reaction of Pt₆₀₀-GLP NCs was used in the colorimetric detection of DA. The linear range for DA was 1–100 μM and the detection limit was 0.66 μM. The sensitive detection of DA using Pt-GLP NCs with peroxidase-like activity offers a simple and practical method that may have great potential applications in the biotechnology field.

Nitrogen doped graphene quantum dots based on host guest interaction for selective dual readout of dopamine

Herein, yellow emissive nitrogen doped graphene quantum dots (N@GQDs) were prepared by a novel advanced thermal driven oxidation. The N@GQDs was functionalized with β-cyclodextrin (β-CD) to improve its catalytic performance towards dopamine (DA) detection. The β-CD/N@GQDs exhibited strong fluorescence at λ_em. = 550 nm after excitation at 460 nm with a quantum yield of 38.6%. The β-CD/N@GQDs showed good peroxidase like activity via catalyzing the oxidation of tetramethylbenzidine (TMB) in presence of H₂O₂ to form blue colored product at λ_max = 652 nm. In the colorimetric assay of DA, the detection based on the oxidation of TMB by H₂O₂ in presence of β-CD/N@GQDs as a catalyst. Then, the color of the blue oxidized TMB (oxTMB) product was reduced by addition of DA. While the fluorometric detection of DA based on the "inner filter effect" of the overlapped emission spectrum of β-CD/N@GQDs with the absorption spectrum of oxTMB, where, addition of DA reduces oxTMB to TMB and restores the fluorescence intensity of β-CD/N@GQDs. Under the optimized conditions, the colorimetric method achieved linearity range of 0.12-7.5 µM and LOD (S/N = 3) of 0.04 µM, while the fluorometric method achieved linearity range of 0.028-1.5 µM and LOD (S/N = 3) of 0.009 µM. The peroxidase like activity of β-CD/N@GQDs was used to detect DA in human plasma and serum samples with good % recoveries. The colorimetric and fluorometric methods exhibited good sensitivity and selectivity toward DA detection.

5,10,15,20-tetrakis (4-carboxyl phenyl) porphyrin-functionalized urchin-like CuCo2O4 as an excellent artificial nanozyme for determination of dopamine

Urchin-like peroxidase mimics 5,10,15,20-tetrakis (4-carboxyl phenyl) porphyrin-functionalized CuCo₂O₄ nanospheres (Por-CuCo₂O₄) has been fabricated as an excellent visual biosensor. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) have been employed to characterize the composition, morphologies, and elemental analysis of the as-synthesized Por-CuCo₂O₄. The catalytic activity of Por-CuCo₂O₄ was evaluated by the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) with the aid of H₂O₂, which exhibited a visual blue change with an absorption maximum at 652 nm for only 10 s. The peroxidase-like behaviors of Por-CuCo₂O₄ conformed to the Michaelis-Menten equation. Electrochemistry, radical scavenger, and fluorescence probe experiments verified that electron transfer, •O₂^- radicals, and holes (h⁺) are the important factors during the catalytic oxidation of TMB. Based on the inhibition of dopamine (DA) on TMB oxidation, the Por-CuCo₂O₄-based colorimetric biosensor has been successfully constructed for sensitive determination of DA witha detection limit (LOD) of 0.94 μΜ. In addition, colorimetry was validated to detect DA in serum samples with high sensitivity and good selectivity. 5,10,15,20-tetrakis (4-carboxyl phenyl) porphyrin-functionalized urchin-like CuCo₂O₄ (Por-CuCo₂O₄) with excellent peroxidase activity, ascribed to the synergistic effect between •O₂^- radicals and holes (h⁺). A fast colorimetric sensor on the basis of Por-CuCo₂O₄ has been constructed to quantitatively determine dopamine concentration in human serums.

Discrimination of dopamine by an electrode modified with negatively charged manganese dioxide nanoparticles decorated on a poly(3,4 ethylenedioxythiophene)/reduced graphene oxide composite

A unique nanocomposite was fabricated using negatively charged manganese dioxide nanoparticles, poly (3,4-ethylenedioxythiophene) and reduced graphene oxide (MnO₂/PEDOT/rGO). The nanocomposite was deposited on a glassy carbon electrode (GCE) functionalized with amino groups. The modified GCE was used to electrochemically detect dopamine (DA). The surface morphology, charge effect and electrochemical behaviours of the modified GCE were characterized by scanning electron microscopy, energy dispersive X-ray analysis (EDX), cyclic voltammetry and electrochemical impedance spectroscopy, respectively. The MnO₂/PEDOT/rGO/GCE exhibited excellent performance towards DA sensing with a linear range between 0.05 and 135 µM with a lowest detection limit of 30 nM (S/N = 3). Selectivity towards DA was high in the presence of high concentrations of the typical interferences ascorbic acid and uric acid. The stability and reproducibility of the electrode were good. The sensor accurately determined DA in human serum. The synergic effect of the multiple components of the fabricated nanocomposite were critical to the good DA sensing performance. rGO provided a conductive backbone, PEDOT directed the uniform growth of MnO₂ and adsorbed DA via pi-pi and electrostatic interaction, while the negatively charged MnO₂ provided adsorption and catalytic sites for protonated DA. This work produced a promising biosensor that sensitively and selectively detected DA.

Rapid and sensitive colorimetric detection of dopamine based on the enhanced-oxidase mimicking activity of cerium(iv)

A fast and sensitive approach for colorimetric determination of DA based on the enhanced oxidase-like catalytic activity of Ce⁴⁺ by DA was developed.

N,N-dicarboxymethyl Perylene-diimide modified CeCoO3: Enhanced peroxidase activity, synergetic catalytic mechanism and glutathione colorimetric sensing

N,N-dicarboxymethyl Perylene-diimide (PDI) modified CeCoO₃ nanocomposites were prepared by a two-step method. After modification with PDI molecules, the obtained PDI-CeCoO₃ nanocomposites were demonstrated to possess the heightened peroxidase-like activity, compared with that of pure CeCoO₃ nanoparticles. In the presence of H₂O₂, the heightened peroxidase-like behaviors of PDI-CeCoO₃ were evaluated by the oxidation of the colorless substrate 3,3,5,5-tetramethylbenzidine (TMB) into blue oxTMB, which was detected visually only in 4 min. Importantly, a systematic study of catalytic activity of PDI-CeCoO₃ by different means, including fluorescent probe, electrochemical data, diffuse reflection spectra together with free radical scavenger is executed, verifying that the catalytic activity were from O₂^- and electron holes (h⁺). And, the transfer of photogenerated carriers in the PDI-CeCoO₃ was the Z-scheme heterojuntion mechanism. Furthermore, the peroxidase-like activity of PDI-CeCoO₃ was significantly inhibited by Glutathione (GSH), resulting in fading of blue oxTMB. Based on this, a colorimetric assay for GSH biosensing has been developed. And, the liner range for GSH detection is from 1 to 10 μM with a detection limit of 0.658 μM. The recovery of GSH with different concentrations from 90.0% to 105.9% and the relative standard deviation (RSD) from 1.9% to 5.1%. This colorimetric sensor can be used to detect GSH in real samples.

Rapid colorimetric sensing of ascorbic acid based on the excellent peroxidase-like activity of Pt deposited on ZnCo2O4 spheres

Pt/ZnCo₂O₄ composites were firstly found to act as artificial peroxidases and used to construct colorimetric sensing platforms for detecting H₂O₂ and ascorbic acid.