Immobilization Of Glucose Oxidase Research Articles

Litchi-like glucose oxidase-integrated magnetic metal-organic framework as glucose-triggered cascade catalyst for antibacterial treatment

The abuse of conventional antibiotic is considered to be one of the main factors hindering the healing of bacteria-infected wound, which has severely threatened the public health. Reactive oxygen species (ROS), such as the common commercial H2O2 have been used as a healing strategy to combat wound infection. However, the low efficiency limits its application. Herein, a litchi-like glucose oxidase-integrated magnetic metal-organic framework (pFe3O4@MOF-GOx) with satisfactory biocompatibility has been constructed as glucose-triggered cascade reagent for antibacterial application. The immobilized glucose oxidase (GOx) can catalyze the decomposition of non-toxic glucose into H2O2 and gluconic acid. Subsequently, the generated H2O2 is catalyzed by the intrinsic peroxidase-like of pFe3O4@MOF to produce toxic hydroxyl radicals. In vitro antibacterial investigations demonstrate the synthesized hybrids display broad-spectrum antibacterial performance with the presence of glucose. Meanwhile, external H2O2 is not required in this developed strategy, which avoids the undesired damage to normal tissues caused by the H2O2 with relatively high concentration in peroxidase-like system. Altogether, the construction of glucose-triggered cascade strategy with effective antibacterial activity provides an alternative method for the treatment of bacterial infected wound.

Electrochemical biosensors based on in situ grown carbon nanotubes on gold microelectrode array fabricated on glass substrate for glucose determination

A highly sensitive electrochemical sensor is reported for glucose detection using carbon nanotubes grown in situ at low temperatures on photolithographically defined gold microelectrode arrays printed on a glass substrate (CNTs/Au MEA). One of the main advantages of the present design is its potential to monitor 64 samples individually for the detection of glucose. The selectivity of the fabricated MEA towards glucose detection is achieved via modification of CNTs/Au MEA by immobilizing glucose oxidase (GOx) enzyme in the matrix of poly (paraphenylenediamine) (GOx/poly (p-PDA)/CNTs/Au MEA). The electrocatalytic and electrochemical responses of the proposed sensing platform towards glucose determination were examined via cyclic voltammetry and electrochemical impedance spectroscopy. The developed impedimetric biosensor exhibits a good linear response towards glucose detection, i.e., 0.2–27.5 µM concentration range with sensitivity and detection limits of 168.03 kΩ−1 M−1 and 0.2 ± 0.0014 μM, respectively. The proposed glucose biosensor shows excellent reproducibility, good anti-interference property, and was successfully tested in blood serum samples. Further, the applicability of the proposed sensor was successfully validated through HPLC. These results supported the viability of using such devices for the simultaneous detection of multiple electroactive biomolecules of physiological relevance.Graphical

Immobilization of Glucose Oxidase on Sodium Alginate Microspheres

Glucose oxidase from Aspergillus niger was immobilized by covalent cross-linking on the surface of alginate microspheres obtained by emulsification/internal gelation method. The catalytic properties of the free and immobilized enzyme were compared. The size of the resulting microspheres was less than 200 μm. Experiments have shown that the immobilized enzyme has an activity 40% lower than the free glucose oxidase, but it has a high activity in a wider range of temperatures and pH values. Kinetic parameters for native glucose oxidase: limit reaction rate – 0.341 mM · min–1, Michaelis constant – 5.41 mM; for immobilized: limit reaction rate – 0.203 mM · min–1, Michaelis constant – 11.43 mM. In infrared Fourier spectra of diffusion reflection of semi-products of biocatalyst synthesis, peaks corresponding to the formed covalent bonds between the enzyme and the carrier were revealed. Synthesized biocatalyst can be used in food industry as bakery improver, in chemical and pharmaceutical industry for production of gluconic acid and in analytical chemistry for determination of glucose concentration.

Dipole moment as the underlying mechanism for enhancing the immobilization of glucose oxidase by ferrocene-chitosan for superior specificity non-invasive glucose sensing.

Non-invasive methods for sensing glucose levels are highly desirable due to the comfortableness, simplicity, and lack of infection risk. However, the insufficient accuracy and ease of interference limit their practical medical applications. Here, we develop a non-invasive salivary glucose biosensor based on a ferrocene-chitosan (Fc-Chit) modified carbon nanotube (CNT) electrode through a simple drop-casting method. Compared with previous studies that relied mainly on trial and error for evaluation, this is the first time that dipole moment was proposed to optimize the electron-mediated Fc-Chit, demonstrating sturdy immobilization of glucose oxidase (GOx) on the electrode and improving the electron transfer process. Thus, the superior sensing sensitivity of the biosensor can achieve 119.97 μA mM-1 cm-2 in phosphate buffered saline (PBS) solution over a wide sensing range of 20-800 μM. Additionally, the biosensor exhibited high stability (retaining 95.0% after three weeks) and high specificity toward glucose in the presence of various interferents, attributed to the specific sites enabling GOx to be sturdily immobilized on the electrode. The results not only provide a facile solution for accurate and regular screening of blood glucose levels via saliva tests but also pave the way for designing enzymatic biosensors with specific enzyme immobilization through fundamental quantum calculations.

Boosting the performance of an iontophoretic biosensing system with a graphene aerogel and Prussian blue for highly sensitive and noninvasive glucose monitoring.

Diabetes and impaired glucose regulation (IGR) threaten the lives and health of numerous patients. Interstitial fluid (ISF) glucose, displaying an excellent correlation with blood glucose, is highly desired to address the limitations of invasive and minimally invasive glucose detection. Herein, we present a screen-printed iontophoretic biosensing system to extract ISF noninvasively and perform in situ instant glucose detection. A three-dimensional graphene aerogel combined with Prussian blue (GA@PB) was introduced as an electron mediator, providing suitable support for glucose oxidase (GOx) immobilization, highly boosting the detection sensitivity. Additionally, a self-made diffuse cell and an ex vivo model were developed to demonstrate the efficacy of ISF extraction based on reverse iontophoresis technology. Highly sensitive and accurate detection of ISF glucose could be achieved with an LOD of 0.26 mM over a 0-15 mM range. Finally, tests on healthy volunteers were conducted to further validate the feasibility of this as-proposed system. Combined with its well flexible and biocompatible features, it holds considerable prospects in the development of wireless wearable biosensors for continuous blood glucose monitoring.

A porphyrin-MOF-based integrated nanozyme system for catalytic cascades and light-enhanced synergistic amplification of cellular oxidative stress.

Peroxidase (POD)-like nanozymes have been found to act as nanoreactors for the generation of reactive oxygen species (ROS) to resolve drug resistance in the tumor microenvironment (TME). Amplifying cellular oxidative stress is considered to be a drug-free strategy to efficiently induce apoptosis in tumor cells. However, the limited content of intracellular hydrogen peroxide (H2O2) extremely restricts the performance of POD-like nanozymes to amplify cellular oxidative stress. Moreover, additional operational processes combined with exogenous reagents to achieve oxidative stress lead to a dilemma of extra cytotoxicity. Here, an integrated iron-porphyrin-MOF-based nanozyme composite named HA@GOx@PCN-224(Fe) (HGPF) was precisely designed and constructed. Generally, the POD-like nanozyme PCN-224(Fe) was used as a platform to immobilize glucose oxidase (GOx), and further embedded with hyaluronic acid (HA) to enable the targeting ability of tumor cells. When endocytosed by tumor cells, intracellular glucose was oxidized to H2O2 and gluconic acid catalyzed by immobilized GOx of HGPF. Afterwards, inspired by heme analogs, H2O2 was catalyzed by iron-porphyrin active sites of the HGPF nanozyme to generate hydroxyl radicals (˙OH). Under light irradiation, the iron-porphyrin of HGPF acted as a photosensitizer to facilely produce singlet oxygen (1O2). Such a synergistic generation of ROS strikingly amplified oxidative stress and induced severe apoptosis in tumor cells. HGPF was expected to integrate intracellular oxygen sources and overcome the dilemma of limited intracellular H2O2 content. Consequently, HGPF was constructed as an integrated nanoreactor to simultaneously achieve light-enhanced catalytic oxidation cascades, providing a promising strategy for a synergistic amplification of cellular oxidative stress.

Preparation of a novel glucose oxidase-N-succinyl chitosan nanospheres and its antifungal mechanism of action against Colletotrichum gloeosporioides

In this work, a new glucose oxidase-N-succinyl chitosan (GOD-NSCS) nanospheres was prepared through the immobilization of glucose oxidase (GOD) on N-succinyl chitosan (NSCS) nanospheres. Compared to the free GOD, GOD-NSCS nanospheres demonstrated the excellent anti-Colletotrichum gloeosporioides activity with the EC50 values of 211.2 and 10.7 μg/mL against mycelial growth and spores germination. The computational biology analysis demonstrated that the substrate presented the similar binding free energy with GOD-NSCS nanospheres (−27.64 kcal/mol) compared with the free GOD (−24.04 kcal/mol), indicating that GOD-NSCS nanospheres had the same oxidation efficiency and produced more H2O2. Moreover, the enzyme activity stability of GOD-NSCS nanospheres could be prolonged to 10 d. The cell membrane was destructed by the treatment of H2O2 produced by GOD, leading to the cell death. In vivo test, GOD-NSCS nanospheres treatment significantly prolonged the preservation period of mangoes 2-fold. Collectively, these results suggested that GOD-NSCS nanospheres suppresses anthracnose in postharvest mangoes by inhibiting the growth of C. gloeosporioides and might become a potential natural preservative for fruits and vegetables.

Immobilization of Glucose Oxidase on Glutathione Capped CdTe Quantum Dots for Bioenergy Generation

An efficient immobilization of Glucose oxidase (GOx) on an appropriate substrate is one of the main challenges of developing fuel cells that allow energy to be obtained from renewable substrates such as carbohydrates in physiological environments. The research importance of biofuel cells relies on their experimental robustness and high compatibility with biological organisms such as tissues or the bloodstream with the aim of obtaining electrical energy even from living systems. In this work, we report the use of 5,10,15,20 tetrakis (1-methyl-4-pyridinium) porphyrin and glutathione capped CdTe Quantum dots (GSH-CdTeQD) as a support matrix for the immobilization of GOx on carbon surfaces. Fluorescent GSH-CdTeQD particles were synthesized and their characterization by UV-Vis spectrophotometry showed a particle size between 5–7 nm, which was confirmed by DLS and TEM measurements. Graphite and Toray paper electrodes were modified by a drop coating of porphyrin, GSH-CdTeQD and GOx, and their electrochemical activity toward glucose oxidation was evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Additionally, GOx modified electrode activity was explored by scanning electrochemical microscopy, finding that near to 70% of the surface was covered with active enzyme. The modified electrodes showed a glucose sensitivity of 0.58 ± 0.01 μA/mM and an apparent Michaelis constant of 7.8 mM. The addition of BSA blocking protein maintained the current response of common interferent molecules such as ascorbic acid (AA) with less than a 5% of interference percentage. Finally, the complex electrodes were employed as anodes in a microfluidic biofuel cell (μBFC) in order to evaluate the performance in energy production. The enzymatic anodes used in the μBFC allowed us to obtain a current density of 7.53 mAcm−2 at the maximum power density of 2.30 mWcm−2; an open circuit potential of 0.57 V was observed in the biofuel cell. The results obtained suggest that the support matrix porphyrin and GSH-CdTeQD is appropriate to immobilize GOx while preserving the enzyme’s catalytic activity. The reported electrode arrangement is a viable option for bioenergy production and/or glucose quantification.

Highly sensitive detection of glucose via glucose oxidase immobilization onto conducting polymer-coated composite polyacrylonitrile nanofibers

Current study introduces composite polyacrylonitrile - multiwall carbon nanotubes nanofibers (PAN-MWCNTs NFs) coated with conducting polymers (polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene) (PEDOT)) by chemical vapor deposition for efficient glucose detection. The potential of nanofibrous assemblies and nano-conducting elements in biosensing was explored as pre-processing of NFs with MWCNTs and post-processing with CPs were both employed. These ‘core-shell’ conducting NFs were further employed as platforms for glucose oxidase immobilization for enzymatic detection of glucose. The performance of the biosensors was closely correlated with the concentration of immobilized enzyme and with the type of conducting polymer. The biosensors showed high sensitivities of 92.94 and 81.72 µA/mM.cm−2 for (PAN-MWCNTs)/ PEDOT and (PAN-MWCNTs)/ PPy accompanied by low limit of detection values of 2.30 and 2.38 µM, respectively. Good operational stability was observed throughout twenty-five consecutive measurements, over 90% activity was maintained for both sensors. This study represents proof of concept for the methodology, showcasing the advantages of nanomaterial synthesis for bio-applications. The work was compared thoroughly with previously reported biosensors showing some of the best results reported to date in terms of analytical characteristics.

Glucose oxidase immobilization on Hemin@PCN-222 (Mn): Integrated biomimetic and bioenzyme activities in cascade catalytic process

On accounting of the structure advantages of MOFs in the enzyme mimics and enzyme immobilization, in this work, the Hemin@PCN-222 (Mn) is constructed through an in-situ hydrothermal route by covalently bonded the –COOH of Hemin with the Zr(IV) of PCN-222 (Mn). With the help of the synergistic effects, the resulting Hemin@PCN-222 (Mn) represents excellent peroxidase-like activities in comparison with the single Hemin and PCN-222 (Mn) with a special enzyme activity of 6.71 U mg−1. The Hemin@PCN-222 (Mn) was then employed as a carrier to immobilize the glucose oxidase (GOx), the immobilization conditions were optimized. Based on that, the optimized GOx@hemin@PCN-222 (Mn) was applied in the following cascade reaction: the glucose oxidation in the presence of oxygen catalyzed by the immobilized GOx firstly, and then the produced H2O2 worked as an oxidant to oxidize ABTS. The quantity of produced ABTS+ was monitored to assess the catalytic efficiency, and the contrast experiments were conducted over the mixture of the natural GOx and HRP. The above cascade process could also be used to detect the glucose, and the detection limit is determined. The high efficiency and the stability of the resulting GOx@hemin@PCN-222 (Mn) highlights the prospect applications of the MOFs-based enzyme mimics in the bio-catalysis and biosensing.

A Noninvasive Sweat Glucose Biosensor Based on Glucose Oxidase/Multiwalled Carbon Nanotubes/Ferrocene-Polyaniline Film/Cu Electrodes.

Diabetes remains a great threat to human beings' health and its world prevalence is projected to reach 9.9% by 2045. At present, the detection methods used are often invasive, cumbersome and time-consuming, thus increasing the burden on patients. In this paper, we propose a novel noninvasive and low-cost biosensor capable of detecting glucose in human sweat using enzyme-based electrodes for point-of-care uses. Specifically, an electrochemical method is applied for detection and the electrodes are covered with multilayered films including ferrocene-polyaniline (F-P), multi-walled carbon nanotubes (MWCNTs) and glucose oxidase (GOx) on Cu substrates (GOx/MWCNTs/F-P/Cu). The coated layers enhance the immobilization of GOx, increase the conductivity of the anode and improve the electrochemical properties of the electrode. Compared with the Cu electrode and the F-P/Cu electrode, a maximum peak current is obtained when the MWCNTs/F-P/Cu electrode is applied. We also study its current response by cyclic voltammetry (CV) at different concentrations (0-2.0 mM) of glucose solution. The best current response is obtained at 0.25 V using chronoamperometry. The effective working lifetime of an electrode is up to 8 days. Finally, to demonstrate the capability of the electrode, a portable, miniaturized and integrated detection device based on the GOx/MWCNTs/F-P/Cu electrode is developed. The results exhibit a short response time of 5 s and a correlation coefficient R2 of 0.9847 between the response current of sweat with blood glucose concentration. The LOD is of 0.081 mM and the reproducibility achieved in terms of RSD is 3.55%. The sweat glucose sensor is noninvasive and point-of-care, which shows great development potential in the health examination and monitoring field.

Optimizing Covalent Immobilization of Glucose Oxidase and Laccase on PV15 Fluoropolymer-Based Bioelectrodes.

Enzymatic biofuel cells (EBCs) represent a promising technology for biosensors, biodevices, and sustainable green energy applications, thanks to enzymes' high specificity and catalytic efficiency. Nevertheless, drawbacks such as limited output power and short lifetime have to be solved. Nowadays, research is addressed to the use of 3D electrode structures, but the high cost and the industrialization difficulties of such electrodes represent a key issue. The purpose of the paper is thus to describe the use of a low-cost commercial conductive polymer (Sigracell® PV15) as support for the covalent immobilization of glucose oxidase and laccase, for bioanode and biocathode fabrication, respectively. Efficient immobilization protocols were determined for the immobilized enzymes in terms of employed linkers and enzyme concentrations, resulting in significant enzymatic activities for units of area. The analysis focuses specifically on the optimization of the challenging immobilization of laccase and assessing its stability over time. In particular, an optimum activity of 23 mU/cm2 was found by immobilizing 0.18 mg/cm2 of laccase, allowing better performances, as for voltage output and electrochemical stability, and a direct electron transfer mechanism to be revealed for the fabricated biocathode. This study thus poses the basis for the viable development of low-cost functional EBC devices for biomedical applications.

Glucose biosensor based on a flexible Au/ZnO film to enhance the glucose oxidase catalytic response

• The indirect isoelectric effect boosts the glucose oxidase immobilization. • The flexible electrode is mechanically stable. • Biosensor performance toward glucose detection is improved by ZnO thin film. • The bioelectrode shows high sensibility and low LOD and LOQ. • The area covered by ZnO shows higher current density toward glucose oxidation. The present work shows the influence of the isoelectric indirect effect of the semiconductor ZnO in the enzymatic immobilization in a glucose biosensor. For this purpose, thin films based on Au and Au/ZnO were synthesized on a microstructured flexible substrate of polyamide filter membrane (P.F) and characterized by FESEM and XRD. Both flexible surfaces were used to immobilize glucose oxidase (GOx) enzyme mixed with ferrocene methanol (Fc) and multiwalled carbon nanotubes (GOx-Fc/MWCNT). Subsequently, these surfaces were used as working electrodes to be evaluated as glucose biosensors. The effect of the ZnO film was compared. The performance of the flexible substrate based on Au/GOx-Fc/MWCNT and Au/ZnO/GOx-Fc/MWCNT as glucose sensor showed similar linearity between 0 – 12 mM glucose; however a higher sensitivity (30.00 µA mM -1 cm -2 ) and lower limit of detection and quantification values were obtained (0.25 mM and 0.83 mM, respectively) when ZnO thin film was used. The results suggest that the ZnO thin film in junction with GOx enzyme enhance the immobilization process of the biocatalyst, resulting in an improvement of the glucose biosensor parameters.

Nanocellulose coated paper diagnostic to measure glucose concentration in human blood.

A new generation of rapid, easy to use and robust colorimetric point of care (POC) nanocellulose coated-paper sensors to measure glucose concentration in blood is presented in this study. The cellulose gel containing the enzyme with co-additive is coated and dried onto a paper substrate. Nanocellulose gel is used to store, immobilize and stabilize enzymes within its structure to prolong enzyme function and enhance its availability. Here, we immobilize glucose oxidase within the gel structure to produce a simple colorimetric blood glucose sensor. Increase in blood glucose concentration increases the concentration of reaction product which decreases the system pH detected by the pH indicative dye entrapped in the nanocellulose gel. The sensor produces a color change from red to orange as pH decreases due to the enzymatic reaction of glucose into gluconic acid and hydrogen peroxide. This sensor can measure glucose concentrations of 7-13mM (medical range for diabetes control) at temperatures of 4°C-40°C. Stability tests confirm that no denaturation of enzyme occurs by measuring enzyme activity after 4weeks. A prototype device is designed to instantly measure the glucose concentration from blood in a two steps process: 1) red blood cell separation and 2) quantification of glucose by color change. This study demonstrates nanocellulose sensor as an economical, robust, and sensitive diagnostic technology platform for a broad spectrum of diseases.

A Mediated Enzymatic Electrochemical Sensor Using Paper-Based Laser-Induced Graphene.

Laser-induced graphene (LIG) has been applied in many different sensing devices, from mechanical sensors to biochemical sensors. In particular, LIG fabricated on paper (PaperLIG) shows great promise for preparing cheap, flexible, and disposable biosensors. Distinct from the fabrication of LIG on polyimide, a two-step process is used for the fabrication of PaperLIG. In this study, firstly, a highly conductive PaperLIG is fabricated. Further characterization of PaperLIG confirmed that it was suitable for developing biosensors. Subsequently, the PaperLIG was used to construct a biosensor by immobilizing glucose oxidase, aminoferrocene, and Nafion on the surface. The developed glucose biosensor could be operated at a low applied potential (-90 mV) for amperometric measurements. The as-prepared biosensor demonstrated a limit of detection of (50-75 µM) and a linear range from 100 µM to 3 mM. The influence of the concentration of the Nafion casting solution on the performance of the developed biosensor was also investigated. Potential interfering species in saliva did not have a noticeable effect on the detection of glucose. Based on the experimental results, the simple-to-prepare PaperLIG-based saliva glucose biosensor shows great promise for application in future diabetes management.

Ti3C2Tx MXene/Graphene/AuNPs 3D porous composites for high sensitivity and fast response glucose biosensing

Glucose oxidase (GOx) is one of the typical enzymes widely used in glucose sensors. In recent years, novel nanomaterials have been developed to immobilize the enzyme, which is of great importance for the development of biosensors. Here we constructed 3D porous Ti3C2Tx MXene/Graphene/AuNPs (MGA) composites by a simple mixing-freeze-drying and self-reduction process. The abundant hydrophilic groups on the surface of Ti3C2Tx MXene nanosheets endow the MGA composites with highly hydrophilic microenvironment. The 3D porous composites provide a more open structure and promote the entry of GOx into the internal pores, which may enhance the stable immobilization and retention of GOx in the film. The unique electrocatalytic properties and synergistic effects between AuNPs and Ti3C2Tx MXene/Graphene are used to further enhance the electron transport in the 3D porous composites and reduce the redox potential. The MGA/GOx glucose sensor shows linear current in the range of glucose concentration from 2 μM to 0.4 mM and 0.4 mM to 6 mM, with sensitivities of 169.49 μA/(mM·cm2) and 34.13 μA/(mM·cm2) respectively, showing high sensitivity at low concentrations. The detection limit of glucose sensor reaches 2 μM and the response time is less than 3 s. This sensor can be applied to the detection of glucose in human sweat.

Glucose test strips with the largest linear range made via single step modification by glucose oxidase-hexacyanoferrate-chitosan mixture

We report on the amperometric second-generation glucose test strips with the linear calibration range covering blood glucose concentrations. Chitosan membrane was used for immobilization of both enzyme and mediator in a single step. Optimal chitosan concentration in membrane-forming mixture corresponds to the highest enzyme activity and dramatically improved mediator adsorption in final membrane. On one hand, the immobilized glucose oxidase activation with an increase of the chitosan polymer content in the membrane has been noticed. On the other hand, positively charged chitosan matrix retains mediator (hexacyanoferrate (III) ion) in the membrane, due to its negative charge. Additionally, the excessive adsorption of the mediator on screen-printed electrodes coated with membranes was proved by means of cyclic voltammetry and impedance spectroscopy. Glucose test strips have been elaborated via single-step modification of the sensor support with the enzyme-mediator-polymer mixture. Apparently, the record linear calibration range from 1 mM to 50 mM glucose was achieved recording amperometric response at 5th second after potential was applied. The elaborated test strips have been validated through analysis of standard serum and blood samples. In whole blood test strips keep 84–98% of their sensitivity in buffer solution.

Tannic Acid‐Promoted Deposition of Glucose Oxidase on Titanium Surfaces for Mitigation of Persistent Bacterial Infections

AbstractMicrobial contamination of the surfaces of biomedical materials/devices is a major obstacle to their clinical applications. Therefore, developing a simple, efficient, and sustainable antibacterial coating is of increasing importance. Inspired by the surface adhesive effect of polyphenols, tannic acid (TA) is utilized to immobilize glucose oxidase (GOD) on the surface of biomedical materials, via hydrogen bonding. Under appropriate physiological conditions, antibacterial and anti‐infection effects of the as‐constructed TA/GOD coatings are explored. Through enzymatic conversion of glucose to gluconic acid and hydrogen peroxide (H2O2), the TA/GOD coating shows strong antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The TA/GOD coating also effectively resists biofilm formation of E. coli and S. aureus. Both in vitro and in vivo studies reveal that the TA/GOD coating does not induce significant adverse side effects during the treatment period. Thus, the present strategy produces an effective coating that resists both bacterial adhesion and persistent infection associated with biomedical materials/implants in the glucose‐containing physiological environment.

Tailoring enzymatic loading capacity on 3D macroporous gold by catalytic hairpin assembly and hybridization chain reaction: Application for ultrasensitive self-powered microRNA detection

It is important to develop effective strategies to construct enzymatic biofuel cell based self-powered biosensors. We report here the facile regulation of enzymatic loading capacity on the bioanode by utilizing a concatenated catalytic hairpin assembly (CHA)/hybridization chain reaction (HCR) and its application for self-powered microRNA-141 (miRNA-141) detection. To construct the bioanode, a concatenated CHA/HCR process triggered by miRNA-141 was conducted on the three-dimensional macroporous gold (3DMG) electrode to generate long double-stranded DNA nanowires for glucose oxidase immobilization. Quartz crystal microbalance study reveals that the enzymatic loading capacity on the bioanode increases at an increasing miRNA-141 concentration, leading to enhanced catalytic performance for glucose oxidation. The short-circuit currents of the assembled glucose/O2 biofuel cells increase at increasing miRNA-141 concentrations, enabling ultrasensitive detection of miRNA-141. The self-powered biosensor features a wide dynamic range for detecting miRNA-141 from 10−17 to 10−11 M, with an ultralow detection limit of 1.3 aM. This work provides a highly sensitive self-powered biosensing platform for miRNA detection.

Numerical Model of an Enzymatic Glucose Sensor with a Blocking Layer on the Electrode

Glucose oxidase-based biosensors are a primary method for continuous glucose monitoring. b-glucose reacts with immobilized glucose oxidase to form gluconic acid and hydrogen peroxide. Hydrogen peroxide is oxidized on an adjacent electrode. The resulting anodic current is proportional to the concentration of glucose. The measured current may be influenced by oxidation of secondary species, such as ascorbic acid and acetaminophen, or fouling of the sensor via foreign body response.[1-3] A blocking layer, placed between the electrode and the immobilized enzyme layer, may act to prevent diffusion of secondary species to the electrode, and reduce the influence of the foreign body response.[3]The influence of a blocking layer on the steady and transient operation of the sensor was evaluated numerically. A blocking layer was added to the steady and transient glucose sensor model outlined in previous work [4] to address the potential influence of acetaminophen. Sensor performance was evaluated for multiple blocking layer thicknesses, reacting species diffusion coefficients, and oxygen concentration. The polarization behavior of the sensor was modeled. Selectivity to glucose was improved by addition of a blocking layer, but sensitivity to oxygen was increased with increasing blocking layer thickness.Numerical simulations of the transient response to a step change in glucose for a sensor with the blocking layer had a response time comparable to the response without the blocking layer, except when the hydrogen peroxide diffusion was greatly reduced in the blocking layer. A step change in acetaminophen yielded time constants comparable to that of the glucose step change in the absence of a blocking layer. The results are sensitive to the thickness of the blocking layer and to the diffusivity of the interfering species in the blocking layer.References Basu, A., & Veettil, S. (2016). Direct Evidence of Acetaminophen Interference with Subcutaneous Glucose Sensing in Humans: A Pilot Study. Diabetes Technology & Therapeutics, 18(S2), 43-47.Surani, S., & Sharma, M. (2021). Interaction between vitamin C and point of care glucose monitoring. Are we overly wary of it or is it a valid concern? Current Medical Research and Opinion, 37(7), 1111-1113.Yang, Y., Zhang, S., & Kingston, M. (2000). Glucose sensor with improved haemocompatibility. Biosensors and Bioelectronics, 15, 221-227.Jacobs and M. E. Orazem, ``Transient Response of a Continuous Glucose Monitor," presented at the 240th Meeting of the Electrochemical Society, Orlando, Florida, October 10-14, 2021. AcknowledgementThe support of Medtronic Diabetes (Northridge, CA) is gratefully acknowledged.