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Chitosan-Stabilized Platinum Nanoparticles as an Effective Oxidase Mimics for Colorimetric Detection of Acid Phosphatase
Abstract and Figures
Capping molecules on the surface of nanomaterials not only enhance the dispersion and stability of nanomaterials but also greatly facilitate their surface modification and biological applications. However, most capping molecules can severely block the active sites of the catalytic core, thereby decreasing the enzymatic activity of nanomaterial-based enzyme mimics. This work demonstrates the superiority of chitosan (Ch) as a capping molecule for synthesizing catalytic platinum nanoparticles (PtNPs). The experimental results show that Ch simultaneously exhibits an excellent stabilizing effect and enhances the oxidase-like activity of PtNPs. Kinetic studies indicate that the Ch-PtNPs have a higher affinity for 3,3',5,5'-tetramethylbenzidine (TMB) than other kinds of oxidase mimics. Furthermore, the TMB chromogenic reaction catalyzed by Ch-PtNPs is found to be much faster in an acidic medium, thus adapting well to the optimum pH for acid phosphatase (ACP). Therefore, a novel colorimetric approach for ACP determination is developed for the first time, which is based on the Ch-PtNP-catalyzed oxidation of TMB, the inhibitory effect of ascorbic acid (AA) on the oxidase-like activity of Ch-PtNPs, and the ACP-catalyzed hydrolysis of AA 2-phosphate (AAP) into AA. The linear range for ACP is 0.25-2.5 U/L and the limit of detection is measured to be 0.016 U/L. This new colorimetric method is utilized to detect ACP in real biological samples and to screen ACP inhibitors. We believe these new PtNPs, which exhibit high colloidal stability, excellent catalytic performance, good biocompatibility, simple preparation, and easy modification, can be a promising candidate for a broad range of applications in optical sensing, environmental monitoring, clinical diagnosis, and drug discovery.
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... According to the reported method, AuNCs@GSH was synthesized using a one-pot hydrothermal method [28], and the detailed preparation scheme is shown in S2.As shown in the flowchart of S3, on the basis of the existing synthesis method [29], we improved to prepare platinum nanoparticles (Ch-PtNPs) using a simple chemical reduction method. After optimization of the conditions tested, 500 μL, 5 mM of TMB solution was added to HAuCl4 solution (500 μL, 0.04 mM), PtNPs solution (900 μL, 0.04 mM), and HAc-NaAc (0.2 mM) buffer solution with pH 4. The mixture was filtered after incubation for one hour and the solution was used for the next step of the experiment. ...
Fluorescence detection is a commonly used analytical method with the advantages of fast response, good selectivity and low destructiveness. However, fluorescence detection, a single-mode detection method, has some limitations, such as background interference that affects the accuracy of the fluorescence signal, lack of visualization of the detection results, and low sensitivity for detecting low-concentration samples. In order to overcome the shortcomings of fluorescence single-mode detection, we used the dual-mode method of fluorescence and colorimetry to detect ascorbic acid. The dual-mode detection of AA by fluorescence and colorimetry in the probe system enhances the specificity and accuracy of the detection. This bimodal detection method solved the problem of low detection sensitivity in the low concentration range of the analytes to be tested, and was linear in the lower (0-50 {\mu}M) and higher (50-350 {\mu}M) concentration ranges, respectively, and had a lower detection limit (0.034 {\mu}M). This glutathione-based gold cluster assay is characterized by simplicity, rapidity and accuracy, and provides a new way for the quantitative analysis of ascorbic acid. In addition, the method was validated during the determination of AA in beverages, which has the advantages of high sensitivity and fast response time.
... The unique benefit of oxidase mimics makes them desirable for developing optical sensing systems with simple operability and high reliability. However, Pt-group metals are the primary focus of the majority of oxidase mimics [6,7]; their limited availability and high cost restrict their mass production and large-scale utilization. Even though oxidase-like activity was discovered in transition metal oxides like MnO 2 [8] and Co 3 O 4 [9], their oxidase-like activity is insufficient and they are susceptible to self-decomposition. ...
A novel dual-mode fluorometric and colorimetric sensing platform is reported for determining glutathione S-transferase (GST) by utilizing polyethyleneimine-capped silver nanoclusters (PEI-AgNCs) and cobalt-manganese oxide nanosheets (CoMn-ONSs) with oxidase-like activity. Abundant active oxygen species (O2•−) can be produced through the CoMn-ONSs interacting with dissolved oxygen. Afterward, the pink oxDPD was generated through the oxidation of colorless N,N-diethyl-p-phenylenediamine (DPD) by O2•−, and two absorption peaks at 510 and 551 nm could be observed. Simultaneously, oxDPD could quench the fluorescence of PEI-AgNCs at 504 nm via the inner filter effect (IFE). However, in the presence of glutathione (GSH), GSH prevents the oxidation of DPD due to the reducibility of GSH, leading to the absorbance decrease at 510 and 551 nm. Furthermore, the fluorescence at 504 nm was restored due to the quenching effect of oxDPD on decreased PEI-AgNCs. Under the catalysis of GST, GSH and1-chloro-2,4-dinitrobenzo (CDNB) conjugate to generate an adduct, initiating the occurrence of the oxidation of the chromogenic substrate DPD, thereby inducing a distinct colorimetric response again and the significant quenching of PEI-AgNCs. The detection limits for GST determination were 0.04 and 0.21 U/L for fluorometric and colorimetric modes, respectively. The sensing platform illustrated reliable applicability in detecting GST in real samples.
Graphical Abstract
We investigated the effects of chitosan (CS) on the hydrogen adsorption and reversibility of hierarchical carbon scaffold (HCS) loaded with Ni nanoparticles. As size-controllable, stabilizing, and shape-directing agents for the green synthesis of metal nanoparticles of CS, Ni nanoparticles with uniform distribution and shape are deposited onto HCS. The latter results in the superior specific surface area of Ni nanoparticles for hydrogen chemisorption. The best hydrogen adsorption capacities at room temperature under 20–70 bar H2 of 0.5–1.70 wt% H2 were obtained from 10 wt% Ni-doped HCS–CS. Although macropores of the HCS collapsed upon cycling due to hydrogen pressure applied during adsorption, average hydrogen capacities of 1.17 ± 0.05 wt% H2 (T = 25 °C and p(H2) = 50 bar) were maintained for 14 cycles. This is because not only uniform distribution and shape of Ni nanoparticles and microporous structures of the HCS were preserved upon cycling but also the interactions between Ni and heteroatoms (N and O) of the HCS and CS prevented particle agglomeration.
α-Glucosidase (α-Glu) is implicated in the progression and pathogenesis of type II diabetes (T2D). In this study, we developed a rapid colorimetric technique using platinum nanoparticles stabilized by chitosan (Ch-PtNPs) to detect α-Glu activity and its inhibitor. The Ch-PtNPs facilitate the conversion of 3,3′,5,5′-tetramethylbenzidine (TMB) into oxidized TMB (oxTMB) in the presence of dissolved O2. The catalytic hydrolysis of 2-O-α-d-glucopyranosyl-l-ascorbic acid (AA-2G) by α-Glu produces ascorbic acid (AA), which reduces oxTMB to TMB, leading to the fading of the blue color. However, the presence of α-Glu inhibitors (AGIs) hinders the generation of AA, allowing Ch-PtNPs to re-oxidize colorless TMB back to blue oxTMB. This unique phenomenon enables the colorimetric detection of α-Glu activity and AGIs. The linear range for α-Glu was found to be 0.1–1.0 U mL−1 and the detection limit was 0.026 U mL−1. Additionally, the half-maximal inhibition value (IC50) for acarbose, an α-Glu inhibitor, was calculated to be 0.4769 mM. Excitingly, this sensing platform successfully detected α-Glu activity in human serum samples and effectively screened AGIs. These promising findings highlight the potential application of the proposed strategy in clinical diabetes diagnosis and drug discovery.
In this work the morphology evolution of Au nanoparticles (AuNPs), obtained by direct reduction, was studied as a function of time, temperature, and Au(III)/sodium ascorbate molar ratio. The NPs morphology was examined by transmission electron microscope with image analysis, while time evolution was investigated by visible and near-infrared absorption spectroscopy and dynamic light scattering. It is found that initially formed star-like NPs transform in more spheroidal particles and the evolution appears more rapid by increasing the temperature while a large amount of reducing agent prevents the remodeling of AuNPs. An explication of morphology evolution is proposed.
Graphical Abstract
Cerium oxide nanoparticles (CeONPs) have received much attention because of their excellent catalytic activities, which are derived from quick and expedient mutation of the oxidation state between Ce4+ and Ce3+. The cerium atom has the ability to easily and drastically adjust its electronic configuration to best fit its immediate environment. It also exhibits oxygen vacancies, or defects, in the lattice structure; these arise through loss of oxygen and/or its electrons, alternating between CeO2 and CeO2−x during redox reactions. Being a mature engineered nanoparticle with various industrial applications, CeONP was recently found to have multi-enzyme, including superoxide oxidase, catalase and oxidase, mimetic properties that produce various biological effects, such as being potentially antioxidant towards almost all noxious intracellular reactive oxygen species. CeONP has emerged as a fascinating and lucrative material in biological fields such as bioanalysis, biomedicine, drug delivery, and bioscaffolding. This review provides a comprehensive introduction to CeONP’s catalytic mechanisms, multi-enzyme-like activities, and potential applications in biological fields.
In this research, we found that the peroxidase-like activities of noncovalent DNA-Pt hybrid nanoparticles could be obviously blocked,when Pt nanoparticles (PtNPs) were synthesized in situ using DNA as a template. Moreover, this self-assembled synthetic process was very convenient and rapid (within few mintues), and the inhibition mediated by DNA was also very effective. First, by the paper-based analytical device (PAD) we found the catalytic activities of DNA-Pt hybrid nanoparticles exhibited a linear response to the concentration of DNA in the range from 0.0075 µM to 0.25 µM. Then,with the magnetic bead isolated system and target DNA-induced hybridization chain reaction (HCR), we realized the specific target DNA analysis with a low detection of 0.228 nM, and demonstrated its effectivity in distinguishing the target DNA from other interferences. To our knowledge, this is the first report that used the nanoassembly between DNA and PtNPs for colorimetric detection of nucleic acids, which was based on DNA-mediated inhibition of catalytic activities of platinum nanoparticles.The results may be useful for understanding the interactions between DNA and metal nanoparticles, and for development of other convenient and effective analytical strategies.
The cytotoxicity of nanozymes has drawn much attention recently because their peroxidase-like activity can decompose hydrogen peroxide (H2 O2 ) to produce highly toxic hydroxyl radicals (•OH) under acidic conditions. Although catalytic activities of nanozymes are highly associated with their surface properties, little is known about the mechanism underlying the surface coating-mediated enzyme-like activities. Herein, it is reported for the first time that amine-terminated PAMAM dendrimer-entrapped gold nanoclusters (AuNCs-NH2 ) unexpectedly lose their peroxidase-like activity while still retaining their catalase-like activity in physiological conditions. Surprisingly, the methylated form of AuNCs-NH2 (i.e., MAuNCs-N(+) R3 , where R = H or CH3 ) results in a dramatic recovery of the intrinsic peroxidase-like activity while blocking most primary and tertiary amines (1°- and 3°-amines) of dendrimers to form quaternary ammonium ions (4°-amines). However, the hidden peroxidase-like activity is also found in hydroxyl-terminated dendrimer-encapsulated AuNCs (AuNCs-OH, inside backbone with 3°-amines), indicating that 3°-amines are dominant in mediating the peroxidase-like activity. The possible mechanism is further confirmed that the enrichment of polymeric 3°-amines on the surface of dendrimer-encapsulated AuNCs provides sufficient suppression of the critical mediator •OH for the peroxidase-like activity. Finally, it is demonstrated that AuNCs-NH2 with diminished cytotoxicity have great potential for use in primary neuronal protection against oxidative damage.
We demonstrate that nickel-palladium hollow nanoparticles (NiPd hNPs) exhibit triple-enzyme mimetic activity: oxidase-like activity, peroxidase-like activity and catalase-like activity. As peroxidase mimetics, the catalytic activity of NiPd hNPs was investigated in detail. On this basis, a simple glucose biosensor with a wide linear range and low detection limit was developed.
A novel magnetic-enhanced colorimetric assay was constructed based on aptamer conjugated PtCo bimetallic nanoparticles (NPs) with high oxidase-like catalytic activity, high water solubility, low cell toxicity, and superparamagnetic properties. It was found that the incorporation of magnetic metal Co atoms into NPs could not only be facilitated for magnetic separation, but also resulted in the significantly improved oxidase-like catalytic activity of the nanoparticles for cancer-cell detection without the destructive H2O2. The present work demonstrates a general strategy for the design of multifunctional materials based on bimetallic nanoparticles for different applications, such as biosensors, nanocatalysts and nanomedicine.
... of Pt@hmC was performed using the procedure for fabrication of a hollow- core /mesoporous- shell ... within the sensitivity of this measurement indicates that the surface of the Pt nanoparticle is free ... encapsulated by a pore system of relatively small pore size,12 the carbon shell of Pt ...
A novel and convenient one-pot but two-step synthesis of fluorescent gold nanoclusters, incorporating glutathione (GSH) and 11-mercaptoundecanoic acid (MUA) as the functionalized ligands (i.e. AuNCs@GSH/MUA), is demonstrated. Herein, the mixing of HAuCl4 and GSH in aqueous solution results in the immediate formation of non-fluorescent GSH-Au(+) complexes, and then a class of ∼2.6 nm GSH-coated AuNCs (AuNCs@GSH) with mild orange-yellow fluorescence after several days. Interestingly, the intense orange-red emitting ∼1.7 nm AuNCs@GSH/MUA can be synthesized within seconds by introducing an alkaline aqueous solution of MUA into the GSH-Au(+) complexes or AuNC@GSH solution. Subsequently, a reliable AuNC@GSH/MUA-based real-time assay of acid phosphatase (ACP) is established for the first time, inspired by the selective coordination of Fe(3+) with surface ligands of AuNCs, the higher binding affinity between the pyrophosphate ion (PPi) and Fe(3+), and the hydrolysis of PPi into orthophosphate by ACP. Our fluorescent chemosensor can also be applied to assay ACP in a real biological sample and, furthermore, to screen the inhibitor of ACP. This report paves a new avenue for synthesizing AuNCs based on either the bottom-up reduction or top-down etching method, establishing real-time fluorescence assays for ACP by means of PPi as the substrate, and further exploring the sensing applications of fluorescent AuNCs.
A facile approach is proposed for growth of platinum nanoparticles on graphene oxide (PtNPs/GO). The resulting PtNPs/GO hybrid has been proved to function as peroxidase mimics that can catalyze the oxidation of peroxidase substrates in the presence of hydrogen peroxide (H2O2). Kinetic studies indicate that the PtNPs/GO nanocomposite has a much higher affinity for both 3,3’,5,5’-tetramethylbenzidine (TMB) and H2O2 than those of other platinum-based peroxidase mimics. Furthermore, colorimetric recognition and sensing of L-cysteine with high sensitivity and selectivity is presented based on target-induced shielding against the peroxidase-like activity of PtNPs/GO. We envision that this material will be an ideal candidate for a wide range of potential application in the fields of biomedicine and environmental chemistry.
In this work, we suggest a chitosan-modified popcorn-like Au-Ag nanoparticles (CSPNPs) based assay for high sensitive detection of melamine, in which CSPNPs not only provide with an intrinsic peroxidase-like activity but also act as surface enhanced Raman scattering (SERS) substrates. CSPNPs can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to the charge transfer complex (CTC), which contributes to a tremendous surface-enhanced resonant Raman scattering (SERRS) signals with 632.8nm laser excitation. The target molecule melamine can generate an additional compound with H2O2, which means the available amount of H2O2 for the oxidation of TMB reduced. Correspondingly, the SERRS intensity of CTC is decreased. The decreased Raman intensity is proportional to the concentration of melamine over a wide range from 10nM to 50μM (R(2)=0.989), with a limit of detection (LOD) of 8.51nM. Moreover, the proposed highly selective method is fully capable of rapid, separation-free detection of melamine in milk powder.
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