Copper-incorporated SBA-15 with peroxidase-like activity and its application for colorimetric detection of glucose in human serum

Fe-doped biodegradable dendritic mesoporous silica nanoparticles for starvation therapy and photothermal-enhanced cascade catalysis in tumor therapy

Combination therapies have attracted significant attention because they address the limitations of monotherapy while improving overall efficacy. In this study, we designed a novel nanoplatform, named GOx@Fe-DMSN@PDA (GFDP), by integrating Fe2+ into dendritic mesoporous silica nanoparticles (DMSN) and selecting glucose oxidase (GOx) as the model drug loaded into the DMSN pores. Additionally, we coated the surface of the DMSN with polydopamine (PDA) to confer pH/near infrared (NIR) light-responsive controlled-release behavior and photothermal therapy (PTT). The introduction of Fe2+ into the DMSN framework greatly improved biodegradability and enhanced the peroxidase (POD)-like activity of GFDP. In addition, GOx could consume glucose and generate hydrogen peroxide (H2O2) within tumor cells to facilitate starvation therapy and enhance cascade catalysis. The PDA coating provided the DMSN with an intelligent response release ability, promoting efficient photothermal conversion and achieving the PTT effect. Cellular tests showed that under NIR light irradiation, GFDP exhibited a synergistic effect of PTT-enhanced starvation therapy and cascade catalysis, with a half-maximal inhibitory concentration (IC50) of 2.89 μg/mL, which was significantly lower than that of GFDP without NIR light irradiation (18.29 μg/mL). The in vivo anti-tumor effect indicated that GFDP could effectively accumulate at the tumor site for thermal imaging and showed remarkable synergistic therapeutic effects. In summary, GFDP is a promising nanoplatform for multi-modal combination therapy that integrates starvation therapy, PTT, and cascade catalysis.

Quantification of Neuronal Cell-Released Hydrogen Peroxide Using 3D Mesoporous Copper-Enriched Prussian Blue Microcubes Nanozymes: A Colorimetric Approach in Real Time and Anticancer Effect

Despite the effectiveness and selectivity of natural enzymes, their instability has paved the way for developing nanozymes with high peroxidase activity using a straightforward technique, thereby expanding their potential for multifunctional applications. Herein, meso-copper-Prussian blue microcubes (Meso-Cu-PBMCs) nanozymes were successfully prepared via a cost-effective hydrothermal route. It was found that the Cu-PBMCs nanozymes, with three-dimensional (3D) mesoporous cubic morphologies, exhibited an excellent peroxidase-like property. Based on the high affinity of Meso-Cu-PBMCs toward H2O2 (Km = 0.226 μM) and TMB (Km = 0.407 mM), a colorimetric sensor for in situ H2O2 detection was constructed. On account of the high catalytic activity, affinity, and cascade strategy, the Meso-Cu-PBMCs nanozyme generated rapid multicolor displays at varying H2O2 concentrations. Under optimized conditions, the proposed sensor exhibits a preferable sensitivity of 18.14 μA μM-1, a linear range of 10 nM-25 mM, and a detection limit of 6.36 nM (S/N = 10). The reliability of the sensor was verified by detecting H2O2 in spiked human blood serum and milk samples, as well as by detecting in situ H2O2 generated from the neuron cell SH-SY5Y. Besides, the Meso-Cu-PBMCs nanozyme facilitated the catalysis of H2O2 in cancer cells, generating •OH radicals that induce the death of cancer cells (HCT-116 colon cancer cells), which holds substantial potential for application in chemodynamic therapy (CDT). This proposed strategy holds promise for simple, rapid, inexpensive, and effective intracellular biosensing and offers a novel approach to improve CDT efficacy.

Copper Immobilized over 2D Hexagonal SBA-15 for Electrochemical and Colorimetric Sulfite Sensing

Sulfite (SO₃^2-) is considered a highly toxic anion for living organisms. Herein, we report the synthesis of copper immobilized over a 2D hexagonally ordered mesoporous silica material CuMS as an electrochemical and colorimetric dual-technique-based sensing platform for sulfite detection. The immobilization of copper on silica was achieved through the bis[3-(triethoxysilyl)propyl]tetrasulfide (TEPTS) ligand. Morphological and physical properties of the material were confirmed by several characterization techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N₂ sorption, and X-ray photoelectron spectroscopy. The CuMS material retained mesoporosity with a narrow pore size distribution (D ≈ 5.4 nm) and a high Brunauer-Emmett-Teller surface area of 682 m² g^-1 after the immobilization of copper. The prepared catalyst shows promising electrocatalytic activity toward sulfite oxidation. A linear variation in the peak current was obtained for SO₃^2- oxidation in the 0.2-15 mM range with a high sensitivity of 62.08 μA cm^-2, under optimum experimental conditions. The limit of detection (LOD) was found to be 1.14 nM. CuMS also shows excellent activity toward colorimetric detection of sulfite anions with an LOD of 0.4 nM. The proposed sensor shows high selectivity toward the sulfite anion, even in the presence of common interferents. The detection of sulfite in white wine with excellent recovery demonstrates the practical applicability of this sensor.

A gold nanoparticle-intercalated mesoporous silica-based nanozyme for the selective colorimetric detection of dopamine

Highly dispersed aggregation-free gold nanoparticles intercalated into the walls of mesoporous silica (AuMS) were synthesized using thioether-functionalized silica as a nanozyme, which exhibited an excellent peroxidase mimic activity. The AuMS material was characterized via XRD, N₂ adsorption-desorption, FESEM, SEM-EDS particle mapping, TEM, and XPS. The peroxidase-like activity of the AuMS material was studied thoroughly, and the effect of pH and temperature was evaluated. The reproducibility of the peroxidase mimic activity and long-term stability of the AuMS catalyst were also studied. Furthermore, the AuMS catalyst was successfully utilized for the detection and quantification of dopamine, an important neurotransmitter, colorimetrically with a linear range of 10-80 μM and a limit of detection (LOD) value of 1.28 nM. The determination of dopamine concentration in commercially available dopamine hydrochloride injection showed high accuracy, good reproducibility, and high selectivity in the presence of uric acid, ascorbic acid, glucose, tryptophan, phenylalanine, and tyrosine.

Colorimetric detection of hydrogen peroxide and glucose by exploiting the peroxidase-like activity of papain

Papain, a natural plant protease that exists in the latex of Carica papaya, catalyzes the hydrolysis of peptide, ester and amide bonds. In this work, we found that papain displayed peroxidase-like activity and catalyzed the oxidation of 3,3',5',5'-tetramethylbenzidine (TMB) in the presence of H2O2. This results in the formation of a blue colored product with an absorption maximum at 652 nm. The effects of experimental parameters including pH and reaction temperature on catalytic activity of papain were investigated. The increase of absorbance induced by the catalytic effect of papain offers accurate detection of H2O2 in the range of 5.00-90.0 μM, along with a detection limit of 2.10 μM. A facile colorimetric method for glucose detection was also proposed by combining the glucose oxidase (GOx)-catalyzed glucose oxidation and papain-catalyzed TMB oxidation, which exhibited a linear response in the range of 0.05-0.50 mM with a detection limit of 0.025 mM. The method proposed here displayed excellent selectivity, indicating that common coexisting substances (urea, uric acid, ascorbic acid, maltose, lactose and fructose) in urine did not interfere with detection of glucose. More importantly, the suggested method was successfully used to precisely detect the glucose concentration in human urine samples with recoveries over 96.0%.

Peroxidase-Like Activity of Smart Nanomaterials and Their Advanced Application in Colorimetric Glucose Biosensors

Diabetes is a dominating health issue with 425 million people suffering from the disease worldwide and 4 million deaths each year. To avoid further complications, the diabetic patient blood glucose level should be strictly monitored despite there being no cure for diabetes. Colorimetric biosensing has attracted significant attention because of its low cost, simplicity, and practicality. Recently, some nanomaterials have been found that possess unexpected peroxidase-like activity, and great advances have been made in fabricating colorimetric glucose biosensors based on the peroxidase-like activity of these nanomaterials using glucose oxidase. Compared with natural horseradish peroxidase, the nanomaterials exhibit flexibility in structure design and composition, and have easy separation and storage, high stability, simple preparation, and tunable catalytic activity. To highlight the significant progress in the field of nanomaterial-based peroxidase-like activity, this work discusses the various smart nanomaterials that mimic horseradish peroxidase and its mechanism and development history, and the applications in colorimetric glucose biosensors. Different approaches for tunable peroxidase-like activity of nanomaterials are summarized, such as size, morphology, and shape; surface modification and coating; and metal doping and alloy. Finally, the conclusion and challenges facing peroxidase-like activity of nanomaterials and future directions are discussed.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes (II)

An updated comprehensive review to help researchers understand nanozymes better and in turn to advance the field.

Increasing enzyme-like activity by in situ anchoring of Ag3PO4 nanoparticles on keratin–inorganic hybrid nanoflowers

Herein, we propose a facile strategy of rapid assembly of Ag₃PO₄ nanoparticles within three dimensional (3D) keratin–inorganic hybrid nanoflowers (keratin-NF@Ag₃PO₄), which can be used for colorimetric detection of UA.

A photoelectrochemical glucose sensor based on gold nanoparticles as a mimic enzyme of glucose oxidase

This work reports the first construction of the ternary layers of ITO/PbS/SiO₂/AuNPs nanostructure for development of photoelectrochemical (PEC) glucose sensor. Herein, the thioglycolic acid-capped PbS quantum dots was employed as a PEC active probe, which is very sensitive to oxygen. The small gold nanoparticles (AuNPs) were act as nanozyme (mimic enzyme of glucose oxidase) to catalytically oxidize glucose in the presence of oxygen, meanwhile consumed oxygen and then resulted in the decrease of cathodic photocurrent. The insertion layer of SiO₂ nanoparticles between PbS and AuNPs could reduce efficiently the base current due to its low electroconductivity, which improved the detection limit. The proposed PEC sensor exhibited high sensitivity and gold selectivity towards glucose. The linear response of glucose concentrations ranged from 1.0 μM to 1.0 mM with detection limit of 0.46 μM (S/N = 3). The results suggest the potential of design and development of numerous nanozyme-based PEC biosensors with the advantage of the simplicity, stability, and efficiency.

This work reports the first construction of the ternary layers of ITO/PbS/SiO₂/AuNPs nanostructure for development of photoelectrochemical (PEC) glucose sensor.

Colorimetric detection of glucose using lanthanum-incorporated MCM-41

In this study, lanthanum-containing mesoporous MCM-41 (La-MCM-41) with different amount of lanthanum were synthesized and were used for colorimetric detection of glucose. As prepared La-MCM-41 were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The quantitative amounts of incorporated lanthanum into MCM-41 structure were estimated by energy dispersive X-ray spectrometry. The prepared La-MCM-41 provided high intrinsic peroxidase-like activity in the presence of peroxidise 3,3',5,5'-tetramethylbenzidine (TMB) and H₂O₂ for accurate determination of glucose. This process produced a blue color in aqueous solution that directly relates to H₂O₂ concentration. The effect of different parameters such as the content of incorporated lanthanum, pH, temperature and time of reaction on the peroxidase-like activity was studied. The colorimetric detection of H₂O₂ was led to a linear dynamic range from 50 to 1000 μM (r² = 0.9988) and low detection limit of 37.5 μM for glucose in aqueous solution. These results are comparable (close to) or better than some previous reports. Thus, La-MCM-41 can be used as admirable alternative design for colorimetric sensing of glucose.

A facile synthesis of CuFe2O4/Cu9S8/PPy ternary nanotubes as peroxidase mimics for the sensitive colorimetric detection of H2O2 and dopamine

Synergistic effects play an important role in improving the catalytic activity for enzyme-like reactions. Compared to individual nanomaterials, a system consisting of multiple components usually exhibits enhanced catalytic activity as an enzyme mimic. Herein we describe the synthesis of CuFe₂O₄/Cu₉S₈/polypyrrole (PPy) ternary nanotubes as an efficient peroxidase mimic via a three-step approach involving an electrospinning process, annealing treatment and hydrothermal reaction. The remarkably enhanced catalytic activity of CuFe₂O₄/Cu₉S₈/PPy ternary nanotubes as peroxidase mimics over individual CuFe₂O₄ nanofibers, CuFe₂O₄/CuO composite nanofibers, CuFe₂O₄/CuS composite nanofibers, and PPy materials has been achieved, demonstrating the presence of a synergistic effect among the components. The steady-state kinetic experiment suggests a good catalytic efficiency of the CuFe₂O₄/Cu₉S₈/PPy ternary nanotubes. On the basis of high catalytic activity, a colorimetric platform for the sensitive detection of H₂O₂ and dopamine has been developed. This work not only offers a simple approach for the fabrication of a high performance peroxidase-like nanocatalyst, but also provides its promising potential applications in biosensors, medical diagnosis, and environmental monitoring.

A Simple and Effective Colorimetric Assay for Glucose Based on MnO₂ Nanosheets

Simple and effective methods for the detection of the level of blood glucose are closely linked to the monitoring of people's health. In the study, MnO₂ nanosheets with absorption range of 300 nm~500 nm and obvious yellow color were easily prepared and applied to detect glucose through their absorbance and color. The proposed method is based on the fact that a specific concentration of glucose can be quantitatively transformed into hydrogen peroxide (H₂O₂) under the catalytic effect of glucose oxidase. Based on the redox reaction of MnO₂ with H₂O₂, yellow MnO₂ can be converted into colorless Mn²⁺ to monitor the concentration of glucose. Under optimal conditions, a simple and effective visual assay for the sensitive and reliable detection of glucose was developed. The linear range was estimated to the range from 0 μM to 100 μM, with a detection limit of 12.8 μM. Furthermore, the proposed colorimetric assay based on MnO₂ nanosheets can effectively detect blood glucose of clinical serum samples with accuracy and convenience.

Colorimetric detection of glucose based on ficin with peroxidase-like activity

In this work, we developed a colorimetric biosensing system for glucose detection by coupling the peroxidase-like of ficin and the glucose oxidase (GOx). GOx can catalyze the oxidation of glucose to produce H₂O₂, then, ficin catalyzes the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂ to produce a blue color reaction. The present sensing system showed a linear response toward glucose detection over range of 2.0-100μM with a detection limit of 0.5μM. This system is simple, low cost, highly sensitive and selective for glucose detection, and was also applied to measuring glucose in human serum. Furthermore, in order to expand the application of ficin in biological sensing, we immobilized ficin onto the SiO₂@Fe₃O₄ NPs, which exhibited the merits of recycling as well as allowing the repeated detection of glucose. Thus it may provide great potential applications in biomedicine, biotechnology and environmental chemistry.

Synthesis of hierarchical Co3O4@NiO core-shell nanotubes with a synergistic catalytic activity for peroxidase mimicking and colorimetric detection of dopamine

Fabrication of core-shell nanostructured catalyst is a promising way for tuning its catalytic performance due to the highly active interface and rich redox properties. In this work, hierarchical Co₃O₄@NiO core-shell nanotubes are fabricated by the deposition of NiO shells via a chemical bath treatment using electrospun Co-C composite nanofibers as templates, followed by a calcination process in air. The as-prepared Co₃O₄@NiO core-shell nanotubes exhibit a uniform and novel hollow structure with Co₃O₄ nanoparticles attached to the inner wall of NiO nanotubes and excellent catalytic activity toward the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂. Due to the synergistic effect, the peroxidase-like activity of the Co₃O₄@NiO core-shell nanotubes is much higher than that of individual Co₃O₄ and NiO components. Owing to the superior peroxidase-like activity, a simple and rapid colorimetric approach for the detection of dopamine with a detection limit of 1.21µM and excellent selectivity has been developed. It is anticipated that the prepared Co₃O₄@NiO core-shell nanotubes are promising materials applied for biomedical analysis and environmental monitoring.

Enzymatic activity of Fe-grafted mesoporous silica nanoparticles: an insight into H2O2and glucose detection

Iron-grafted MSNs were synthesized by post-synthesis and applied as a biosensor for detection of glucose and H₂O₂.

CeO₂ Nanorods Embedded in Ni(OH)₂ Matrix for the Non-Enzymatic Detection of Glucose

The electrode based on cerium oxide (CeO₂) nanorods embedded in nickel hydroxide (Ni(OH)₂) matrix were prepared and used for detecting glucose non-enzymatically. The materials were characterized by X-ray diffraction, transmission electron microscopy (TEM), and so on. The results indicate that the response of CeO₂/Ni(OH)₂ nanocomposite are significantly improved due to the synergetic effect between CeO₂ and Ni(OH)₂. The optimum CeO₂/Ni(OH)₂ nanocomposite electrode exhibits a detection range from 2 μM to 6.62 mM, a sensitivity of 594 μA mM-1 cm-2, an estimated detection limit of 1.13 μM, and a response time less than 5 s. In addition, this biosensor also shows good selectivity, long term stability, and accurate measurement in juice on sale.

Visual detection of glucose using triangular silver nanoplates and gold nanoparticles

A sensitive spectrophotometric detection of glucose based on triangular silver nanoplates (Ag TNPs) coupled with gold nanoparticles (Au NPs) was carried out.

Difunctional Cu-doped carbon dots: catalytic activity and fluorescence indication for the reduction reaction of p-nitrophenol

The reduction reaction ofp-nitrophenol was catalyzed and monitored using the fluorescence of Cu-doped CDs.