Colorimetric Glucose Research Articles

Rapid in-situ growth of gold nanoparticles on cationic cellulose nanofibrils: Recyclable nanozyme for the colorimetric glucose detection

Novel microwave-assisted green in-situ synthesis of positively charged gold nanoparticles (AuNPs) supported by cationic cellulose nanofibrils (C.CNF) within 30 s and devoid of additional reducing agent is reported. Peroxidase activity of these positive AuNPs was studied and that appeared to be superior over its negative charged counterpart. Further the AuNPs@C.CNF is casted into a film which makes it reusable. Using TMB substrate, simple and sensitive colorimetric detection methods for H2O2 and glucose were established. Under optimal conditions, the linear ranges were found to be 0.5–30 μM and 1–60 μM, and the detection limits were 0.30 and 0.67 μM for H2O2 and glucose, respectively. The film was potentially reused for the detection of glucose up to five cycles without a decrease in the activity. Further, this technique was employed to quantify glucose in human serum samples, and the obtained results were comparable with those of the standard GOD-POD method.

Breaking the pH limitation of peroxidase-like CoFe2O4 nanozyme via vitriolization for one-step glucose detection at physiological pH

In recent years, a growing number of nanosized materials that can mimic the catalytic characteristics of some natural enzymes have experienced a period of rapid development. Among these nanomaterials defined as ‘nanozymes’, peroxidase-mimicking materials draw intensive interest because of their potential applications in various fields, including biosensing, medicine, and environmental engineering. Nonetheless, most of currently explored peroxidase nanozymes exhibit favorable activity only in acidic environments, which greatly restricts their use especially in biochemical analysis. Developing peroxidase mimics with good catalytic performance in a broad pH range is highly desired and still challenging. Herein, we report a vitriolization strategy to broaden the catalytic pH scope of peroxidase-like CoFe2O4. The vitriolization process endows the nanomaterial with sustainable acidity on its surface. As a result, the obtained peroxidase nanozyme (SO42−/CoFe2O4) exhibits good catalytic activity in neutral or even weak alkaline solutions. This provides us a one-step assay for colorimetric glucose detection in one pot at physiological pH via combining the proposed peroxidase mimic with glucose oxidase, which shows advantages of easier operation and faster detection while offering comparable analytical performance.

Photopolymerization-Based Synthesis of Uniform Magnetic Hydrogels and Colorimetric Glucose Detection.

Magnetic hydrogels have been commonly used in biomedical applications. As magnetite nanoparticles (MNPs) exhibit peroxidase enzyme-like activity, magnetic hydrogels have been actively used as signal transducers for biomedical assays. Droplet microfluidics, which uses photoinitiated polymerization, is a preferred method for the synthesis of magnetic hydrogels. However, light absorption by MNPs makes it difficult to obtain fully polymerized and homogeneous magnetic hydrogels through photoinitiated polymerization. Several methods have been reported to address this issue, but few studies have focused on investigating the light absorption properties of photoinitiators. In this study, we developed a simple method for the synthesis of poly(ethylene glycol) (PEG)-based uniform magnetic hydrogels that exploits the high ultraviolet absorption of a photoinitiator. Additionally, we investigated this effect on shape deformation and structural uniformity of the synthesized magnetic hydrogels. Two different photoinitiators, Darocur 1173 and lithium phenyl (2,4,6–trimethylbenzoyl) phosphinate (LAP), with significantly different UV absorption properties were evaluated based on the synthesis of magnetic hydrogels. The magnetic characteristics of the PEG-stabilized MNPs in hydrogels were investigated with a vibrating sample magnetometer. Finally, the colorimetric detection of hydrogen peroxide and glucose was conducted based on the enzyme-like property of MNPs and repeated several times to observe the catalytic activity of the magnetic hydrogels.

A Hybrid of FeS2 Nanoparticles Encapsulated by Two-Dimensional Carbon Sheets as Excellent Nanozymes for Colorimetric Glucose Detection.

Recently, the development of nanozymes with high catalytic performance is gaining more and more attention due to the ever-growing demands for their practical applications. The elaborate design of its morphology has demonstrated to be an effective approach to improve the performance of these nanozymes. Herein, a hybrid of iron disulfide nanoparticles (FeS2 NPs) encapsulated by two-dimensional (2D) carbon nanosheets (NSs), denoted as FeS2@C NSs, demonstrates both superior peroxidase-like activity and excellent stability. The incorporation of 2D carbon sheets endows the proposed FeS2@C nanozymes with high specific surface area, providing abundant active sites to facilitate the contact with substrates. Moreover, the embedded FeS2 NPs are kept from aggregation due to the encapsulation and confinement of 2D carbon sheets, avoiding the conventional failure of single-component nanozymes. Based on glucose oxidase (GOx) and the elaborately designed FeS2@C nanozymes, a colorimetric method for glucose detection is then developed with excellent simplicity and sensitivity. The detection limit of the sensing platform is as low as 0.19 μM for a glucose assay. More notably, this method can be successfully employed for the glucose assay in some real samples, indicating the great potential of this FeS2@C NS-based nanozymes in the fields of biotechnology and clinical diagnostics.

A colorimetric and ratiometric glucose sensor based on conformational switch of i-motif DNA

Colorimetric methods to detect glucose are promising for the wide applications in the assays of diabetes diagnosis, environments and foods, but traditional colorimetric methods for glucose detection are usually limited in the use of peroxidase or the complex chemical synthesis of nanomaterials, and improving sensitivity remains a challenging task. In this paper, based on the conformational switch of i-motif DNA triggered by the variation of pH value resulting from the oxidation of glucose, a facile colorimetric and ratiometric biosensor for selective and sensitive detection of glucose is propounded. In such an assay protocol, glucose was detected expediently by the color difference between free methylene blue (MB) and MB bound with a cytosine-rich single-stranded DNA without using any peroxidase or nanomaterials. Delightedly, the assay demonstrated a wide linear response for the glucose concentration in a range from 5 to 800 µmol/L with a low detection limit of 1.43 µmol/L (3 s / slope). Besides, this biosensor was applied in detecting glucose in human serum samples successfully, suggesting its potential of applying in the healthcare of monitoring glucose with a cheap, convenient and enzyme-free method.

Vanadium‐Substituted Tungstosulfate Polyoxometalates as Peroxidase Mimetics and Their Potential Application in Biosensing

AbstractThis article reports on the peroxidase‐like catalytic activity of polyoxometalates (POMs) and their potential use as natural peroxidases for developing a simple and efficient colorimetric glucose sensor. Two Keggin‐type vanadium‐substituted tungstosulfates, [SVW11O40]3− (SVW11) and [SV2W10O40]4− (SV2W10), were tested for their potential as natural enzyme mimetics and exhibited strong peroxidase‐like catalytic activity. The catalysis reaction was found to be in accordance with Michaelis‐Menten and Lineweaver‐Burk kinetics models. Michaelis‐Menten constant (Km) and maximum velocity (Vmax) parameters were calculated to be 0.0759 mM and 0.329×10−8 Ms−1 for SVW11, and 0.0543 mM and 2.67×10−8 Ms−1 for SV2W10, respectively, indicating a high catalytic activity and a strong affinity of POMs towards 3,3,5,5‐tetramethylbenzidine (TMB). In the case of H2O2, these values were found to be 57.1 mM and 0.325×10−8 mMs−1 for SVW11, and 47.7 mM and 2.72×10−8 mMs−1 for SV2W10. The peroxidase‐like catalytic activity of these POMs was used to develop colorimetric glucose sensors as a proof‐of‐concept model for the POM‐based naked‐eye detection of biomolecules. The limit of detcetion (LOD) of glucose for SVW11 and SV2W10 was 1.14 μM and 1.24 μM, respectively. Our findings propose broad‐ranging potential applications of these novel POMs in biosensing and bioanalytical chemistry.

One-pot, direct glucose detection in human whole blood without using a dilution factor by a magnetic nanozyme with dual enzymatic activity

The necessity of sample pretreatment, the limited absorbance variation in the concentration range of calibration plot are the common restrictions of the colorimetric glucose sensors used with the complex samples. A calibration plot in a concentration range far below the common level of complex biological sample mostly involves to use a high dilution factor for finding the actual glucose level in the complex sample. Glucose oxidase immobilized-Au nanoparticle attached-magnetic SiO2 (GOx@Au@MagSiO2) microspheres were proposed as a new magnetic nanozyme, allowing one-pot and direct determination of glucose concentration in human whole blood without using a sample pretreatment and a high dilution factor. As an unusual approach which is not coherent with the common strategy followed for colorimetric determination of blood glucose level, a calibration plot based on the common range of human whole blood (i.e. 2.8–38.9 mM) is generated with the synthesized nanozyme. GOx was directly linked onto Au nanoparticles (Au NPs) immobilized on the magnetic SiO2 microspheres via a simple protocol, using the thiol groups of its cysteine residues, as a unique property of GOx’s, for the first time. The activity of free GOx could be highly preserved by the selected immobilization protocol. GOx@Au@MagSiO2 microspheres exhibited peroxidase-like activity due to Au NPs immobilized on the magnetic microspheres, together with the glucose oxidation ability originated from GOx linked to Au NPs. The nanozyme was efficiently used for one-pot, direct determination of glucose level in human whole blood in the concentration range of 50–700 mg/dL (i.e. 2.8–38.9 mM).

Ultrarapid, size-controlled, high-crystalline plasma-mediated synthesis of ceria nanoparticles for reagent-free colorimetric glucose test strips

We describe an ultrarapid (within several minutes), size-controlled (<100 nm in diameter), and high-crystalline plasma-mediated synthesis of ceria nanoparticles and their application in reagent-free colorimetric test strips. Glucose oxidase (GOx) incorporated onto the paper matrix generates H2O2 with glucose, subsequently inducing color changes of the embedded ceria nanoparticles from white/yellow to yellow/orange without any involvement of colorimetric substrate or dye. The optimized protocol yielded ∼2-fold higher color intensity compared to that of commercially available ceria nanoparticles, presumably due to its much larger surface area and higher Ce3+ content, facilitating the oxidation from Ce3+ to Ce4+ and formation of peroxide complexes at the nanoparticle surfaces. Using the colorimetric test strip, glucose was specifically detected over a wide linear range (0.1−10 mM), with excellent reusability, storage stability, precision, and reproducibility. The innovative plasma-mediated ultrarapid synthesis of size-controlled and high-crystalline ceria nanoparticles and their utilization on reagent-free colorimetric test strip allow for a straightforward sensing platform for the point-of-care detection of glucose and can be expanded to other oxidative enzymes for facile colorimetric detection of various clinically important target molecules.

Silver nanoparticles-decorated reduced graphene oxide: A novel peroxidase-like activity nanomaterial for development of a colorimetric glucose biosensor

In this study, we present a novel approach to prepare of a colorimetric chemical sensor for H2O2 and a glucose biosensor basing on the use of peroxidase-like activity of silver nanoparticles decorated on reduced graphene oxide sheets (AgNPs@rGO) nanocomposite. Herein, AgNPs@rGO nanocomposite was synthesized by a one-step hydrothermal reducing method and its physico-chemical properties were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Ultraviolet–visible spectroscopy (UV–Vis), Fourier-Transform Infrared spectroscopy (FT-IR) and Energy Dispersive X-ray spectroscopy (EDX). Obtained evaluation results shown that the synthesized AgNPs/rGO nanocomposite has performed an efficient peroxidase-like activity for the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMBred) by H2O2, leading to the oxidized form (TMBox) which presents a typical blue color (maximum of absorbance at λmax = 655 nm). A colorimetric assay for H2O2 detection was designed and fabricated with a limit of detection of 20 μM. Moreover, we have used of AgNPs/rGO nanocomposite combining with glucose oxidase (GOx) to develop of a colorimetric glucose biosensor with a low limit of detection of 40 μM and a linear dynamic range from 125 μM to 1 mM. This glucose test was applied to the detection of glucose in human serum samples.

Highly sensitive smartphone-integrated colorimetric glucose sensor based on MnFe2O4 – graphitic carbon nitride hybrid nanostructure

An extremely sensitive colorimetric glucose sensor was fabricated using a novel hybrid nanostructure comprised of manganese ferrite oxide– graphitic carbon nitride (MnFe2O4/g-C3N4). A neural network-based glucose analytical smartphone application can be used to easily monitor the glucose concentration with a high accuracy by only taking images with the smartphone camera. The as-synthesized MnFe2O4/g-C3N4 exhibited a very high affinity toward 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2, as calculated via Michaelis-Menten kinetics. The glucose sensors using as-synthesized MnFe2O4/g-C3N4 exhibit a wide linear range and very low detection limits of 20.5 nM for H2O2 and 17.3 nM for glucose, which are one of the lowest values ever reported.The instrumental analysis with XPS, XRD, and TEM revealed that MnFe2O4/g-C3N4 had a highly crystalline structure of MnFe2O4 and g-C3N4 with abundant oxygen vacancies and well-developed hybrid structures, which might result in excellent catalytic activity and glucose sensitivity.

Introducing Colorimetric Analysis with Document Scanner for High School Students

Spectrophotometer is modern analytical instrument for analysis the amount of substance based on the color change. However, for high school laboratory practice, only few schools had this instrument for chemical analysis. There are many studies reported the use of daily life electronic for colorimetric analysis such as smartphone, scanner and digital camera. This work demonstrated the used of document scanner for colorimetric glucose determination for easy learn the daily life instrument as analytical device. The color detection was based on the reaction of glucose with glucose oxidase enzyme to produce H2O2. The H2O2 was then reacted with TiOSO4 to produce yellow color. The color formation was captured with a document scanner and the digital image was analyzed using ImageJ software. The result of the used of document scanner showed Horwitz Ratio of 0.40, recovery of 98.4%, linear responses from 0.5 mM to 3.0 mM (r = 0,9989), limit of detection of 0.15 mM and limit of quantification of 0.40 mM.

High-strength paper enhanced by chitin nanowhiskers and its potential bioassay applications

In this paper, nanochitin was used as an alternative natural nanomaterial to combine with cellulose fibers for fabricating high-strength paper. Two typical chitin nanowhiskers having contrasting sign of surface charge were compared to evaluate the enhancement performance on paper in details. The results show that nanochitin with positive charges on the surface has a significant effect on the strength properties of the prepared paper, especially on wet strength. When the dosage of chitin nanowhiskers was 2%, the wet strength index was increased to 2.48 N·m/g, which is important for paper-based analytical devices with the common use in liquid analysis. Typical colorimetric glucose assays were successfully performed, suggesting the improved analytical performance on these prepared paper.

Enzyme Encapsulation in Glycerol–Silicone Membranes for Bioreactions and Biosensors

Efficient enzyme immobilization is one of the main challenges in biocatalysis. Properly immobilized enzymes ensure enzyme reusability and high conversion efficiency of biocatalytic reactions, which ultimately leads to reduction of the process costs and increased sustainability. Here a simple, versatile, and cost-efficient platform technology for physical encapsulation of enzymes within elastomeric membranes is presented. The membranes are obtained by simple mixing of two immiscible liquids, a commercial silicone prepolymer and glycerol, which results in formation of glycerol-in-silicone emulsions. Upon curing of the silicone phase free-standing elastomers are obtained, and the glycerol droplets are randomly dispersed in the silicone matrix. Enzymes are dissolved in the glycerol phase prior to the emulsification process; thus, each glycerol reservoir of the glycerol–silicone membrane becomes a microsize bioreactor. In a simple experiment an enzyme-containing glycerol–silicone membrane was immersed in water with dissolved substrate of a bioreaction. The concentration gradient induces the migration of the substrate to the glycerol reservoirs where it is converted by the enzyme to a product, which is subsequently released from the membrane. In this article the performances of processes involving diffusion and enzymatic reactions within the glycerol–silicone membranes are compared. The glycerol content in the membranes was found to have a significant impact on the reaction rate. This concept was also utilized to create a proof-of-concept elastomeric colorimetric glucose biosensor.

A colorimetric bioassay for quantitation of both basal and insulin-induced glucose consumption in 3T3-L1 adipose cells

IntroductionThe quantitation of glucose consumption in animal cell cultures is mainly based on the use of radiolabeled or fluorescent analogues, resulting in expensive and tedious procedures, requiring special equipment and, sometimes, with potential health and environmental risks. ObjectivesThe objective of this work was to evaluate the application of a blood plasma colorimetric assay to quantify glucose consumption in in vitro cultures of adipose cells. MethodsWe worked with 3T3-L1 adipose cells differentiated by 7–8 days, which were exposed to different initial glucose concentrations (5.5, 2.8 and 1.4 mM) for variable times, either in the absence or the presence of 100 nM insulin. Using a commercial colorimetric glucose assay, extracellular glucose was determined, and glucose uptake was calculated as the difference between the initial and final glucose concentration. ResultsThe colorimetric assay allowed us to quantify glucose uptake in our cell model, observing a linear response over time (r2≥0.9303) to the different glucose concentrations, both in the basal and insulin-induced condition. The insulin-stimulated glucose consumption was higher than basal consumption at all glucose concentrations evaluated, but significant differences were observed at 120-, 360- and 480-min in glucose 5.5 mM (p ≤ 0.01, n = 5), and 240 min in glucose 1.4 mM (p ≤ 0.01, n = 5). A Vmax of 4.1 and 5.9 nmol/ml/min (basal and insulin-induced, respectively) and a Km of 1.1 mM (same in basal vs insulin-stimulated) were calculated. The bioassay was also useful in a pharmacological context: in glucose 1.4 mM, glucose consumption showed an effect that depended on insulin concentration, with a calculated EC50 of 18.4 ± 1.1 nM. ConclusionsA simple and low-cost bioassay is proposed to quantify glucose consumption in 3T3-L1 adipose cells.

Low-cost and real-time color detector developments for glucose biosensor

One of the analytical methods widely developed is a biosensor, which has several advantages. We reported the development of a real-time colorimetric detector for glucose biosensor using low-cost electrical components of LDR, TCS230 and webcam. The detection was based on the color recognition from the devices resulted in RGB color intensity of the yellow color of hydrogen peroxide and titanium oxysulfate reaction. The comparison of three developed low-cost methods showed that the detector based on TCS230 had the best sensitivity. The real-time colorimetric glucose biosensor using TCS230 showed a good linearity, in the glucose detection of 0.1 to 2.5 mM with the regression equation of y = 27.89x + 35.31 (R2 = 0.993). Furthermore, the calculated limit of detection of 0.14 mM and calculated limit of quantification of 0.58 mM. The glucose biosensor was also showed high selectivity to detect glucose in the blood sample with good agreement compare to commercial glucose biosensor.

Protein-mediated sponge-like copper sulfide as an ingenious and efficient peroxidase mimic for colorimetric glucose sensing.

Strenuous efforts have been made to develop nanozymes for achieving the performance of natural enzymes to broaden their application in practice, but the fabrication of high-performance and biocompatible nanozymes via facile and versatile approaches has always been a great challenge. Here, sponge-like casein-CuS hybrid has been facilely synthesized in the presence of amphiphilic protein-casein through a simple one-step approach. Casein-CuS hybrid exhibits substrates-dependent peroxidase-like activity. Casein-CuS hybrid exhibits well peroxidase-like activity with 3,3′,5,5′-tetramethylbenzidine (TMB) and 1,2-diaminobenzene (OPD) as substrates, and the affinity of OPD towards the hybrid nanozyme is much higher than that of TMB. More importantly, due to the high affinity of OPD and the well biocompatibility of the hybrid nanozyme, a superior enzyme cascade for glucose based on the well cooperative effect of casein-CuS hybrid and glucose oxidase is developed. The proposed glucose sensor exhibits a wide linear range of 0.083 to 75 μM and a detection limit of 5 nM. This suggests the promising utilization of protein–metal hybrid nanozymes as robust and potent peroxidase mimics in the medical, food and environmental detection fields.

Glucose oxidase and Au nanocluster co-encapsulated metal–organic frameworks as a sensitive colorimetric sensor for glucose based on a cascade reaction

The GOx &amp; AuNCs@ZIF-8 composite was simply obtained as a colorimetric glucose sensor with high sensitivity and selectivity and long-term storage stability.

Smartphone based platform for ratiometric fluorometric and colorimetric determination H2O2 and glucose

In this work, a new strategy for ratiometric fluorescent and colorimetric determination of H2O2 and glucose is proposed. The sensing system involves catalytic oxidation reaction of glucose oxidase (GOx) with glucose to generate H2O2. Under the catalysis of Fe2+, the 580 nm emission of carbon dots (C-dots) upon 365 nm excitation is reduced by H2O2, while the fluorescence emission at 450 nm of thiochrome (oxVB1) enhances with the oxidation reaction between H2O2/Fe2+system and VB1 (thiamine). Simultaneously, the color of the carbon dots (C-dots) suspension changes from purplish-red to colorless. Thus, the fluorescence intensity ratio (I450/I580) and the absorbance (A557) can be used to quantitatively determine H2O2 and glucose. Furthermore, we integrated fluorometric and colorimetric output with a smartphone platform to conduct on-site analysis of glucose without the need of spectrometer. A smartphone application (APP) was designed to take pictures and analyze R, G, B values of fluorometric and colorimetric signals, which delivered excellent analytical result for glucose. This ratiometric fluorescent and colorimetric sensing system on a smartphone platform ensures sensitive and convenient determination of glucose and H2O2, hence having great prospects in biomedical analysis.

Precise engineering of ultra-thin Fe2O3 decorated Pt-based nanozymes via atomic layer deposition to switch off undesired activity for enhanced sensing performance

Unlike natural enzymes, nanozymes possess often multiple enzyme-mimic activities, which can be the impediment for their applications. Current strategies in activity engineering are based mainly on extensive cut-and-try screening and lack accurate engineering methods. It has not been reported through rational design to exaggerate the desired activity and suppress unwanted ones. In this study, inspired by catalytic theories in traditional nanocatalysis, ultra-thin Fe2O3 decorated Pt in inverse catalyst model (Fe2O3/Pt/CNTs) with high ratio of Pt0/Pt2+, new Pt-O-Fe3+ bonds and more interface sites was designed for excellent peroxidase activity and inhibited oxidase activity. Atomic layer deposition (ALD), as a novel approach for nanozyme preparation, enables the fine tailoring of surface microstructure of Fe2O3/Pt/CNTs. Activity analysis verified our design and the final Fe2O3/Pt/CNTs possess greatly enhanced peroxidase activity while the oxidase activity was eliminated. The detection limit of a colorimetric glucose sensor based on Fe2O3/Pt/CNTs was almost 10-fold lower over Pt/CNTs through the elimination of false-positive signal caused by the oxidase activity. These results demonstrated that, in virtue of the meticulous engineering method like ALD, rational design is feasible and powerful to engineer nanozymes with desired activity.

Photothermal-enhanced tandem enzyme-like activity of Ag2-xCuxS nanoparticles for one-step colorimetric glucose detection in unprocessed human urine

It is greatly significant and difficult to realize the purpose of natural enzyme free and “one-step” for traditional colorimetric urine glucose detection. Here, ultra-small Ag2-xCuxS nanoparticles (NPs) with tandem enzyme-like activity, i.e. they simultaneously exhibit glucose oxidase (GOx)- and peroxidase-like activities, are developed for tandem glucose oxidation and colorimetric H2O2 detection. Cu doping content has a great influence on the enzyme-like activity. Ag1.8Cu0.2S NPs (i.e. Ag2-xCuxS NPs with 10 % Cu) exhibit the best catalytic performance. The tandem enzyme-like activity can be further enhanced to ∼10 times under laser irradiation due to photothermal effect. Furthermore, accurate glucose detection has been realized in unprocessed human urine based on the photothermal-enhanced tandem enzyme-like activity of Ag1.8Cu0.2S NPs. This natural enzyme free and “one-step” colorimetric glucose detection strategy exhibits the potential application of the new generation of tandem enzyme-like nanomaterials.