Chitosan-reduced Graphene Oxide Research Articles

Sensitivity of chitosan/reduced graphene oxide/manganese dioxide modified electrodes for cholesterol detection using cyclic voltammetry

Cholesterol detection needs to be carried out to detect early symptoms of dangerous diseases such as heart disease. The process of detecting cholesterol in the human blood requires a sensitive detection tool in order to produce accurate values. This paper reports the performance of chitosan thin films modified with reduced graphene oxide (rGO) and manganese dioxide (MnO2) as the sensitive layer of working electrodes in detecting cholesterol. The electrode substrate is a copper-screen printed electrode (copper-SPE) which was patterned into 5 mm of sensitive area. The chitosan and chitosan-reduced graphene oxide (rGO) matrices were deposited on the top of working electrodes. The characterization of chitosan, chitosan/rGO, and chitosan/rGO/MnO2 thin films was performed using AFM, FE-SEM, and FTIR. The electrochemical sensing properties of modified working electrode were observed using an electrochemical method of cyclic voltammetry (CV). The novelty of this research is the utilization of chitosan/rGO/MnO2 thin film-based working electrode for detecting cholesterol. The testing results indicated that the sensitivity of the modified working electrodes increased when working electrodes based on chitosan/rGO/MnO2 thin film were used for cholesterol detection compared to the working electrodes based on the chitosan thin film. It was proven from the sensitivity of working electrodes based on chitosan/rGO/MnO2 thin film which gave the lowest value of 3.21 × 10−5 µA/µM as well as the ability of working electrodes based on chitosan/rGO/MnO2 thin film which worked at limit of detection (LoD) 0.26 µM/L and limit of quantification (LoQ) 0.87 µM/L. Based on the sensitivity, LoD, and LoQ values, the chitosan/rGO/MnO2 modified electrodes can be used as working electrodes to measure cholesterol concentration in blood.

Sensitivity of Chitosan Film Based Electrode Modified with Reduced Graphene Oxide (rGO) for Formaldehyte Detection Using Cyclic Voltammetry

This paper reports the ability of chitosan-reduced graphene oxide (rGO) modified electrode as a sensitive layer of working electrode in detecting formaldehyde. The electrode substrate is in the form of copper-SPE which has been shaped into 5 mm of sensitive area. On top of the working electrode, a number of chitosan and chitosan-reduced graphene oxide (rGO) matrices were placed in the form of a thin film layer that works as a working electrode. Characterization of chitosan and chitosan-reduced graphene oxide (rGO) thin films was done using SEM, TEM, AFM and FTIR. The test for electrochemical sensing ability of working electrode was observed using cyclic voltammetry (CV), whereas chitosan and chitosan-rGO films were deposited onto the surface of working electrodes. The novelty of this research is the utilization of chitosan-rGO thin film based working electrode for detecting formaldehyde. The testing results showed sensitivity and response of working electrode increased when chitosan-reduced graphene oxide modified electrode was used for formaldehyde detection compared to chitosan film based working electrode. It was proven from the sensitivity value of chitosan-rGO based working electrode at the lowest value of 4.6 × 10−4 µA/µM and linear range at 1–12 × 10−4 µM/L, as well as the ability of chitosan-rGO based working electrode which worked at limit of detection (LoD) 0.36 µM/L and limit of quantification (LoQ) 1.21 µM/L.

Development of nanocomposites based on chitosan/reduced graphene oxide for wound healing application

Nanocomposites containing different effective materials have various effects, such as antioxidant, and anti-inflammatory activity, which are desirable for wound dressing. Herein, nanocomposites based on chitosan/reduced graphene oxide (CS/rGO) containing curcumin (CS/rGO/Cur), curcumin and papain (CS/rGO/Cur/Pa), curcumin, papain, and collagen peptide (CS/rGO/CP/Cur/Pa), prepared using ionic gelation method and characterized by Fourier Transform Infrared (FTIR), Differential Light Scattering (DLS), X-ray diffraction (XRD), and Scanning Electron Microscope (SEM). Subsequently, the nanocomposite's potential for wound healing was studied through parameters such as porosity, swelling, degradability, anti-inflammatory, antioxidant, antibacterial, cell viability, and in-vivo. The results of FTIR, XRD, SEM, and DLS showed that the nanocomposites synthesized properly with an almost spherical morphology, an average diameter of below 100 nm (mostly 40–85 nm), and a hydrodynamic diameter of 455–616 nm. The various tests demonstrated the nanocomposite's effectiveness in wound healing. The results showed that CS/rGO/CP/Cur/Pa increased the anti-inflammatory and cell viability up to 99.7 % and 395 %, respectively, which is higher than others. Animal tests on rats showed that CS/rGO/CP/Cur/Pa accelerated the wound healing rate up to 70 %. In conclusion, the results showed that the nanocomposites based on CS/rGO significantly improve wound healing, and the presence of collagen peptides boost their wound healing potency.

Manufacturing N,O-carboxymethyl chitosan-reduced graphene oxide under freeze-dying for performance improvement of Li-S battery

Lithium-sulfur (Li-S) batteries can provide far higher energy density than currently commercialized lithium ion batteries, but challenges remain before it they are used in practice. One of the challenges is the shuttle effect that originates from soluble intermediates, like lithium polysulfides. To address this issue, we report a novel laminar composite, N,O-carboxymethyl chitosan-reduced graphene oxide (CC-rGO), which is manufactured via the self-assembly of CC onto GO and subsequent reduction of GO under an extreme condition of 1 Pa and −50 °C. The synthesized laminar CC-rGO composite is mixed with acetylene black (AB) and coated on a commercial polypropylene (PP) membrane, resulting in a separator (CC-rGO/AB/PP) that can not only completely suppress the polysulfides penetration, but also can accelerate the lithium ion transportation, providing a Li-S battery with excellent cyclic stability and rate capability. As confirmed by theoretic simulations, this unique feature of CC-rGO is attributed to its strong repulsive interaction to polysulfide anions and its benefit for fast lithium ion transportation through the paths paved by the heteroatoms in CC.

Water-based chitosan/reduced graphene oxide ink for extrusion printing of a disposable amperometric glucose sensor

Recently, developing appropriate printing techniques and conductive inks has received considerable attention in the field of (bio)sensors. Extrusion printing technology is an interesting alternative to conventional screen-printing for making flexible and disposable electronics due to its special features such as, direct printing, easy control of design, and manufacturing processes. Moreover, fabricating highly dispersed and stable graphene inks with appropriate conductivity and printability is always a challenge in (bio)sensors. Here, a water-based chitosan/reduced graphene oxide (CS/rGO) ink was obtained using extrusion printing to make conductive electrodes on paper. CS/GO ratio of 0.2 showed the best stability, electrochemical performance and hydrophilicity (water contact angle of 85° ± 6). The resulting sensor was a simple two-electrode device based on the chronoamperometry technique, representing a good potential for detecting glucose in the linear range of 0.5 to 4 mM and with a limit of detection (LOD) of 0.45 mM (S/N = 3). Furthermore, this non-enzymatic sensor showed proper selectivity against interfering substances, as well as an excellent stability during 28 days (2.9% response fall). Ultimately, the developed conductive ink can be considered as an innovative material with high stability and dispersivity of rGO for the future studies on disposable (bio)sensors and flexible electronics.

Simple immunosensor for ultrasensitive electrochemical determination of biomarker of the bone metabolism in human serum.

Ultrasensitive and selective determination of biomarkers of the bone metabolism in serum is crucial for early screening, timely treatment, and monitoring of the curative effect of osteoporosis, which is a silent disease with serious health threats. Immunoassay with a simple sensing interface and ultrahigh sensitivity is highly desirable. Herein, a simple electrochemical immunosensor is demonstrated based on gold nanoparticles (AuNPs) electrodeposited on chitosan-reduced graphene oxide (CS-G) composite modified electrode, which can achieve sensitive determination of the important biomarker of bone metabolism, bone gamma-carboxyglutamate protein (BGP). To overcome the agglomeration of graphene and introduce a biocompatible matrix with functional amino groups, CS-G is prepared and modified on the supporting glassy carbon electrode (GCE). Then, AuNPs are electrodeposited on CS-G through their interaction between amine groups of CS. The immobilized AuNPs provide numerous binding sites to immobilize anti-BGP antibodies (AbBGP). The specific recognition between BGP and AbBGP results in a reduction in the mass transfer of the electrochemical probe (Fe(CN)6 3-/4-) in solution, leading to a reduced electrochemical signal. Based on this mechanism, fast and ultrasensitive electrochemical detection of BGP is achieved when the concentration of BGP ranges from 100 ag ml−1 to 10 μg mL−1 with a limit of detection (LOD) of 20 ag ml−1 (S/N = 3). The determination of BGP in human serum is also realized with high reliability.

Highly Stable and Reproducible Biosensor Interface based on Chitosan and 2,5-Di(thienyl)pyrrole based Conjugated Polymer

Interface design is the most crucial part of biosensor development because its rational design methodologies are directly related to the quality of sensing performance, such as sensitivity, reproducibility, stability, and linearity. In this study, a thienyl pyrrole derived electroactive monomer [N1, N4-bis(2,5-di(thiophene-2-yl)-1H-pyrrol-1-yl)terephthalamide] (TP) has been synthesized and electropolymerized onto chitosan (CS) and chitosan-reduced graphene oxide (rGO) modified electrode to produce highly stable and reproducible sensor platforms for glucose detection. The synergistic interactions of chitosan and p(TP) have produced the sensor platform inherent properties such as conductivity in three dimensions, ability to covalently bind the enzyme, interface compatibility of components, hydrophilicity. CS/p(TP)/GOx bioelectrodes offer higher sensitivity (0.322 μA μM−1 cm−2), detection limit (0.097 μM) and good selectivity compared to CS-rGO/p(TP)/GOx (0.531 μA μM−1 cm−2 and 0.159 μM) bioelectrodes. Also, CS/p(TP)/GOx bioelectrodes show excellent longer-term storage stability, retaining 98.6% sensitivity after nine weeks, whereas the CS-rGO/p(TP)/GOx bioelectrode lost initial activity in two weeks when stored at 4 °C. Aside from the excellent stability and sensitivity, multiple sensor electrodes prepared under the same conditions gave the same glucose response without needing to be recalibrated.

Direct removal of nitrate and phosphate anions together in a continuous fixed bed column down flow technique

Synthetic adsorbent was used for the direct removal of nitrate and phosphate anions from aqueous solution. Synthetic absorbent was prepared in laboratory using different processes, which have high adsorption capacities for effective removal of selected ions in a column chromatography. Chitosan-reduced graphene-SiO2 in a column was used as a potent adsorbent for this selected method and final results were compared with another approach using chitosan-SiO2 in a Photo Catalytic Reactor (PCR). PCR process is easier, but the removal efficiency is less when compared with the Fixed Bed Column (FBC). The removal percentage using fixed bed column with a potent adsorbent was greater than 60% whereas it is less than 35% using photocatalytic reactor. Adsorption of nitrate and phosphate from aqueous solutions on both photocatalytic reactor and continuous fixed-bed column are studied with effects of various parameters such as contact time, dosage of adsorbent and pH of the aqueous solutions. Absorbents were fabricated using sol-gel for nano silica, chitosan and thermal heating method for reduced graphene oxides. Out of these, fixed bed columns with chitosan-reduced graphene oxide - SiO2 performed better when compared with the chitosan-SiO2 in a photocatalytic reactor.

Localized SPR for Pb(II) ion sensing utilizing chitosan/reduced graphene oxide nanocomposite

In this work, a simple and highly sensitive localized surface plasmon resonance (LSPR) technique had been developed for detection of Pb(II) utilizing chitosan/reduced graphene oxide (CS/rGO) nanocomposite as the sensing material. Gold nanoparticles (AuNP) had been incorporated with the nanocomposite material to induce strong LSPR responses. CS/rGO nanocomposite was coated on top of AuNP and had been utilized as active layer for Pb(II) ion sensing. The morphology and physical properties of gold nanoparticle-chitosan/reduced graphene oxide (AuNP-CS/rGO) nanocomposite was studied using field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and x-ray diffraction (XRD) analysis. FESEM exhibits a rough and wrinkle surface of AuNP-CS/rGO after the addition of rGO. AFM shows a higher surface roughness for AuNP-CS/rGO due to the presence of oxygen atoms in rGO where these oxygen atoms provide more sites for adsorption of Pb(II), hence enhance the sensitivity of the sensor. A good sensitivity of the LSPR sensor for detection of Pb(II) utilizing AuNP-CS/rGO was obtained which is 1.544 ppm-1 and the linearity of the sensor are 0.99 and 0.97. In stability study, AuNP-CS/rGO exhibits a good repeatability with relative standard deviation of 2% for 0.01 ppm.

Preparation of chitosan-reduced graphene oxide microcapsules

Preparation of chitosan-reduced graphene oxide microcapsules

Preparation of chitosan-reduced graphene oxide (CS-RGO) microcapsules and its application in UV/moisture-induced self-healing coatings

Self-healing coatings healed by the synergistic action of ultraviolet light and moisture are developed. Firstly, a polysiloxane-based healing agent, containing acryloyloxy (CH2=C(CH3)COO-)and methoxy silane(-SiOCH3)groups, is synthesized and encapsulated in chitosan-reduced graphene oxide (CS-RGO) microcapsules with compact CS-RGO shell structures. The CS-RGO microcapsules containing the polysiloxane core are then embedded in epoxy-modified silicone resin to achieve efficient self-healing coatings. Herein, an assembly time of 2.5 h results in a complete stacking of GO sheets on the emulsion droplets. As the CS/GO ratio increase, the reduction degree of GO, the sphericity of the CS-RGO microcapsules, and the average diameter all increase. Moreover, the compact CS-RGO shell formed by the assembly and stacking GO sheets as well as the interactions between CS and GO helps to maintain effectiveness of the core and stability of the microcapsules. The result shows that embedding of the CS-RGO microcapsules in the resin matrix improves the mechanical properties and anti-corrosion properties of the matrix. What’s more, the self-healing coatings with the UV/moisture dual healing mode is beneficial for achieving superior self-healing effects, which is promising for various industries, especially the over-water construction of ships, bridges, pipelines, etc.

Production of metal oxides nanoparticles based on poly-alanine/chitosan/reduced graphene oxide for photocatalysis degradation, anti-pathogenic bacterial and antioxidant studies

A novel AgO-CoO-CdO/Poly(alanine)-chitosan-reduced graphene oxide (PACSGO) nanocomposite was developed to study the degradation efficiency under visible light irradiation. The AgO, CoO, CdO nanoparticles and AgO-CoO-CdO heterometal oxides were prepared by using the chemical method. The crystallite structure and phase studies were studied by the X-ray diffraction assay. The SEM images were evaluated to explore the morphology of the prepared materials. EDS analysis and FTIR spectra confirmed the formation of nano-materials with high purity. The optical bandgap values were measured via Kubelka-Munk plot showing that the metal oxides produced a new energy state in the electronic level for high photocatalysis efficiency. The incorporation of AgO-CoO-CdO in PACSGO showed a novel nano-photocatalyst for substantial degradation of dye in low process time. The catalysis data displayed that PACSGO based AgO-CoO-CdO nanocomposites ensured a strong potential to degradation of organic dye compounds from water in during photocatalysis reaction. The beneficial anti-pathogenic bacterial performance of the AgO-CoO-CdO/PACSGO nanocomposites was further demonstrated by a substantial reduction in the amount of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and B. cereus medium and increase in inhibition zone value with the addition of the AgO-CoO-CdO/PACSGO nanocomposites.

A novel Fe-hemin-metal organic frameworks supported on chitosan-reduced graphene oxide for real-time monitoring of H2O2 released from living cells

Herein, a kind of novel hemin-based metal organic frameworks (Fe-hemin-MOFs) with unique peroxidase-like bioactivity was developed for the first time. The synthesized Fe-hemin-MOFs exhibited satisfactory catalytic activity toward hydrogen peroxide (H2O2). When it was further supported on Chitosan-reduced graphene oxide (CS-rGO), amplified electrochemical signal could be obtained. The Fe-hemin-MOFs/CS-rGO composite was used to construct a novel H2O2 electrochemical sensor. The electrocatalytic reduction of H2O2 displayed two segments linearity range from 1 to 61 μM and 61–1311 μM, as well as a low detection limit of 0.57 μM. Furthermore, the proposed sensor was successfully used for real-time monitoring of H2O2 released from living cells, which extended the practical application of MOFs-based sensors in monitoring the pathological process in living cells.

Chitosan-reduced graphene oxide hybrids encapsulated Pd(0) nanocatalysts for H2 generation from ammonia borane

The hybrids consisting of chitosan (CS) and reduced graphene oxide (rGO) were assembled with an in-situ reduction strategy. Then, the resulting CS-rGO was used to encapsulate palladium nanoparticles (Pd NPs) via reducing PdCl2 with NaBH4. The mass ratios of CS to GO were optimized to increase the catalytic activity of the resultant Pd NPs/CS-rGO catalysts for the hydrolysis of ammonia borane (AB). The analytic results revealed that the Pd NPs (1.1–2.3 nm in diameter) were evenly encapsulated in the CS-rGO hybrids. Under the present conditions, the optimized Pd NPs/CS-rGO offered a high turnover frequency (TOF) value of 42.5 molH2molPd−1min−1. The activation energy of the AB hydrolysis was 39.02 kJ mol−1 and the corresponding orders of Pd and AB concentrations were 0.90 and 0.33, respectively. In addition, the Pd NPs/CS-rGO catalysts retain a stable hydrogen generation activity after four runs.

Efficient combined near-infrared-triggered therapy: Phototherapy over chemotherapy in chitosan-reduced graphene oxide-IR820 dye-doxorubicin nanoplatforms

Significant efforts are currently being funneled into the improvement of therapeutic outcomes in cancer by designing hybrid nanomaterials that synergistically combine chemotherapeutic abilities and near-infrared (NIR) light-activated photothermal (PTT) and photodynamic (PDT) activity. Herein, a nanotherapeutic platform is specifically designed to integrate combinational functionalities: chemotherapy, PTT, PDT and traceable optical properties. The system, based on chitosan-reduced graphene oxide (chit-rGO), incorporates and carries a large payload of IR820 dye with dual PTT and PDT activity and a chemotherapeutic drug, doxorubicin (DOX). The potential of the fabricated nanoplatforms to operate as an NIR activatable therapeutic agent is first assessed in aqueous solution by investigating its ability to generate singlet oxygen and heat under NIR irradiation with 785 nm laser irradiation. The in vitro anticancer activity of chit-rGO-IR820-DOX is evaluated against murine colon carcinoma cells (C26). The fabricated nanosystem exhibits synergistic anticancer activity against C26 cancer cells by combining IR820 induced PDT, simultaneous graphene and IR820 induced PTT and the chemotherapeutic effect of DOX. Notably, the therapeutic performance of chit-rGO-IR820-DOX can be controlled by the ratio between IR820 and DOX. Moreover, chit-rGO-IR820-DOX facilitates localization inside cancer cells correlated with the release of DOX via mapping by confocal Raman microscopy.

5-Fluorouracil and curcumin co-encapsulated chitosan/reduced graphene oxide nanocomposites against human colon cancer cell lines

Recent attention on chemotherapy against cancer is to explore the effective therapy through targeted delivery of anticancer agents to the tumor site by manipulating pharmacokinetic properties of nanocarriers. 5-Fluorouracil (5-FU) and curcumin (CUR) loaded chitosan/reduced graphene oxide (CS/rGO) nanocomposite has been prepared via simple chemical method. The polymer matrix-type chitosan/rGO nanocomposite, before and after encapsulation, has been analyzed by various characterizations. Entrapment and loading efficiencies were estimated. The results that demonstrated higher entrapment efficiency (> 90%) were achieved by CS/rGO nanocarrier. Various kinetic models were used to analyze the release model and to elucidate the release mechanism of the drug from CS/rGO nanocomposite. The synergistic cytotoxicity was observed on addition of 5-FU + CUR-loaded CS/rGO nanocomposite which shows the effectiveness of the system toward the inhibition of growth of HT-29 colon cancer cells. The better cytotoxicity with an IC50 of 23.8 μg/mL was observed for dual-drug-loaded nanocomposite.

Chitosan-reduced graphene oxide composites with 3D structures as effective reverse dispersed solid phase extraction adsorbents for pesticides analysis.

Chitosan-reduced graphene oxide composites with 3D structures (3D CS-rGO) were prepared via a facile solvothermal synthetic strategy. The reduction of GO and crosslinking of rGO nanosheets with CS into 3D structures were achieved simultaneously in one step. The resulting 3D CS-rGO composite achieves high adsorption capacities of catechins, caffeine and pigments from tea acetonitrile extraction, especially for catechins, which is 10 times higher than that of GO (179.3 mg g-1vs. 18.7 mg g-1). The 3D CS-rGO composite exhibits the best removal efficiency of matrix interference in comparison to other traditional adsorbents, which could diminish the matrix effect on targeted pesticides by 1%-55%. A determination method of 70 kinds of pesticides is successfully established for tea based on 3D CS-rGO composite as an efficient reverse dispersed solid phase extraction adsorbent. The established method has the great advantages of operation simplicity, being time saving and high purification performance using only one kind and a low amount of adsorbent. 3D graphene based materials are expected to be promising adsorbents for sample pretreatment in trace contaminant analysis of complex food samples.

Chitosan and graphene oxide/reduced graphene oxide hybrid nanocomposites – Evaluation of physicochemical properties

In this paper we have presented results of our studies on chitosan/graphene oxide (CS/GO) and chitosan/reduced graphene oxide (CS/rGO) hybrid nanocomposites. First, L-ascorbic acid (L-AA), grape extract (GE), and green tea extract (GT) were tested as green reducing agents for reduced graphene oxide synthesis. Structural and chemical properties of the obtained rGOs were examined by X-ray diffraction (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). Next, GO and rGOs were introduced into the chitosan matrix to prepare a series of hybrid nanocomposites. Their physicochemical properties were evaluated by XRD, ATR-FTIR, DSC (differential scanning calorimetry), SEM (scanning electron microscopy), wettability and mechanical testing. It was found that all of the introduced nanofillers affected the structural, thermal, microstructural, mechanical, and surface properties of the nanocomposites. Addition of GO resulted in the increase of Young's modulus by 35%, while the composites reinforced with rGO_L-AA were soft and easy to bend in hand without cracking. We showed that simultaneous synthesis of rGO-L-AA and fabrication of the CS/rGO_L-AA hybrid nanocomposite allowed to fully exploit the potential of the chitosan/rGO system. The developed materials, after detailed biological characterization, may be potentially applicable in bone and cartilage tissue engineering.

Cu-Hemin Metal-Organic-Frameworks/Chitosan-Reduced Graphene Oxide Nanocomposites with Peroxidase-Like Bioactivity for Electrochemical Sensing

Herein, a Cu-hemin metal-organic-frameworks (MOFs)/chitosan (CS)-reduced graphene oxide (CS-rGO) nanocomposite with unique peroxidase-like bioactivity and good electrical conductivity was prepared for electrochemical H2O2 sensing for the first time. The prepared Cu-hemin MOFs/CS-rGO nanocomposites were well characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray powder diffraction, UV–vis spectroscopy and electrochemical techniques. The results showed that after the Cu-hemin MOFs were formed on the CS-rGO surface, the crystalline structure of the Cu-hemin MOFs was kept while the size of Cu-hemin MOFs was decreased and the electrical conductivity of the nanocomposites was enhanced greatly as compared with that of Cu-hemin MOFs. The unique peroxidase-like bioactivity and good electrical conductivity as well as some novel properties of Cu-hemin MOFs/CS-rGO nanocomposites resulted in perfect electrochemical performances towards the reduction of hydrogen peroxide (H2O2), superior to some mimic enzymes. The Cu-hemin MOF/CS-rGO was used to construct a novel H2O2 electrochemical sensor which exhibited wide linear range (0.065–410μM) and low detection limit (0.019μM). The study might provide a new proposal for preparing perfect hemin-based materials as mimetic peroxidase in the electrochemical sensing.

PH-Switchable Electrochemical Sensing Platform based on Chitosan-Reduced Graphene Oxide/Concanavalin A Layer for Assay of Glucose and Urea

A facile and effective electrochemical sensing platform for the detection of glucose and urea in one sample without separation was developed using chitosan-reduced graphene oxide (CS-rGO)/concanavalin A (Con A) as a sensing layer. The CS-rGO/Con A with pH-dependent surface net charges exhibited pH-switchable response to negatively charged Fe(CN)6(3-). The principle for glucose and urea detection was essentially based on in situ pH-switchable enzyme-catalyzed reaction in which the oxidation of glucose catalyzed by glucose oxidase or the hydrolyzation of urea catalyzed by urease resulted in a pH change of electrolyte solution to give different electrochemical responses toward Fe(CN)6(3-). It was verified by cyclic voltammograms, differential pulse voltammograms, and electrochemical impedance spectroscopy. The resistance to charge transfer or amperometric current changed proportionally toward glucose concentration from 1.0 to 10.0 mM and urea concentration from 1.0 to 7.0 mM. On the basis of human serum experiments, the sensing platform was proved to be suitable for simultaneous assay of glucose and urea in a practical biosystem. This work not only gives a way to detect glucose and urea in one sample without separation but also provides a potential strategy for the detection of nonelectroactive species based on the enzyme-catalyzed reaction and pH-switchable biosensor.