Immobilization strategies to develop enzymatic biosensors

Two-dimensional covalent organic frameworks (2D COFs) are candidate materials for charge storage devices because of their micro- or mesoporosity, high surface area, and ability to predictably organize redox-active groups. The limited chemical and oxidative stability of established COF linkages, such as boroxines and boronate esters, precludes these applications, and no 2D COF has demonstrated reversible redox behavior. Here we describe a β-ketoenamine-linked 2D COF that exhibits reversible electrochemical processes of its anthraquinone subunits, excellent chemical stability to a strongly acidic electrolyte, and one of the highest surface areas of the imine- or enamine-linked 2D COFs. Electrodes modified with the redox-active COF show higher capacitance than those modified with a similar non-redox-active COF, even after 5000 charge–discharge cycles. These findings demonstrate the promise of using 2D COFs for capacitive storage.

β-Ketoenamine-linked covalent organic frameworks capable of pseudocapacitive energy storage

Glucose enzyme biosensors have been shown useful for a range of applications from medical diagnosis, bioprocess monitoring, to beverage industry and environmental monitoring. We present here a highly sensitive glucose enzyme sensor based on Pt nanoparticles (PtNPs)-polyaniline (PAni) hydrogel heterostructures. High-density PtNPs were homogeneously loaded onto the three-dimensional (3D) nanostructured matrix of the PAni hydrogel. The PtNP/PAni hydrogel heterostructure-based glucose sensor synergizes the advantages of both the conducting hydrogel and the nanoparticle catalyst. The porous structure of the PAni hydrogel favored the high density immobilization of the enzyme and the penetration of water-soluble molecules, which helped efficiently catalyze the oxidation of glucose. In addition, the PtNPs catalyzed the decomposition of hydrogen peroxide that was generated during the enzymatic reaction. The transferred charges from these electrochemical processes were efficiently collected by the highly conducting...

Highly Sensitive Glucose Sensor Based on Pt Nanoparticle/Polyaniline Hydrogel Heterostructures

A contact lens with embedded sensor for monitoring tear glucose level

https://cmapspublic3.ihmc.us/rid=1LTYW6MQS-2275MBW-29XF/articulo%20de%20polimeros.pdf

Conductive polymer-based sensors for biomedical applications

Polypyrrole nanotube array sensor for enhanced adsorption of glucose oxidase in glucose biosensors.

Human plasma low density lipoprotein (LDL) immunosensor based on surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) was fabricated by immobilizing antiapolipoprotein B (AAB) onto self-assembled monolayer (SAM) of 4-aminothiophenol (ATP). The AAB/ATP/Au immunosensor can detect LDL up to 0.252 microM (84 mg/dL) and 0.360 microM (120 mg/dL) with QCM and SPR, respectively. The SPR and QCM measurements were further utilized to study the reaction kinetics of the AAB-LDL interaction. The adsorption process involved was explored using Langmuir adsorption isotherm and Freundlich adsorption models. The thermodynamic parameters such as change in Gibb's free energy (DeltaG(ads)), change in enthalpy (DeltaH(ads)), and change in entropy (DeltaS(ads)) determined at 283, 298, and 308 K revealed that the AAB-LDL interaction is endothermic in nature and is governed by entropy. Kinetic, thermodynamic, and sticking probability studies disclosed that desorption of the water molecules from the active sites of AAB and LDL plays a key role in the interaction process and increase in temperature favors binding of LDL with the AAB/ATP/Au immunosensor. Thus, the studies were utilized to unravel the most important subprocess involved in the adsorption of LDL onto AAB-modified ATP/Au surface that may help in the fabrication of LDL immunosensors with better efficiency.

Low density lipoprotein detection based on antibody immobilized self-assembled monolayer: investigations of kinetic and thermodynamic properties.

Usage of nanoporous polypyrrole on H2O2 bi-functional sensing after immobilizing horseradish peroxidase (HRP) is described in this paper. Nanoporous alumina membranes were used to produce nanopores on polypyrrole surface. Nanopores increased the effective surface area available for enzyme immobilizing. Further, this increased area enhances the electron flow caused by the catalytic reactions. When the sensor was deployed to sense H2O2 at 0.2 V a high sensitivity of 3.9 A M−1 cm−2 was observed at a fast response time of 5 s. When the working potential was reversed to −0.1 V, a wider linear range of 10 nM to 25 μM was achieved. These novel findings will lead the way to a new path of biosensor design for low substrate concentrations with enhanced characteristics.

Bi-functional amperometric biosensor for low concentration hydrogen peroxide measurements using polypyrrole immobilizing matrix

Characteristic dependency of nano scale polypyrrole (PPy) glucose biosensors, achieved by three different immobilizing techniques namely, coentrapment, physical adsorption and a two step method of coentrapment superimposed with physical adsorption is reported. Different enzyme loading and material properties resulted in varied immobilizing methods lead to dissimilarities in characteristics. In this study, Pt coated AnodiscTMs (0.2 µm) were used as electrodes to polymerize PPy at 0.3 mA cm-2 using a solution containing 0.05 M Pyrrole and 0.1 M NaPF6. The polymerization time was optimized to 90 s. In the coentrapment method, glucose oxidase (GOx) (1 mg ml-1) was added to the monomer solution while an aliquot of GOx (5 µl) was placed on the pre-polymerized electrode for physical adsorption. A combined procedure of these two techniques was used as the last immobilization technique. Physical adsorption method gave a sensitivity of 3 mA cm-2 M-1 and a linear range of 0.5–13 mM with a response time of a 3 s. Sensitivity in the case of coentrapment was 3.75 mA cm-2 M-1 while it showed a value of 4.45 mA cm-2 M-1 in two step immobilization thus giving 25 and 48% increases respectively. Response times of 9 and 8 s in latter cases reveal the possible repercussion taking place at enzyme immobilization in three dimensional (3-D) PPy matrix and the delay occur in glucose to reach the enzyme. Linear range of the two step method was extended up to 16 mM due to the reinforced enzyme loading.

Effect of Glucose Oxidase Immobilizing Techniques on Performances of Nano Scale Polypyrrole Glucose Biosensors

Sensor networks play a significant role in modern day structures. From large bridges to sky scrapers, application of sensor networks –  both wireless and wired – has strengthened the structural reliability and hence the safety of their users. The objective of this survey paper is to identify different usages of sensor networks in structures and further elaborate on different types of sensing together with the techniques associated with processing the parameters sensed by the sensor networks to achieve the desired implementation goals.

E. M. I. Mala Ekanayake

Papers

Polypyrrole nanotube array sensor for enhanced adsorption of glucose oxidase in glucose biosensors.

Low density lipoprotein detection based on antibody immobilized self-assembled monolayer: investigations of kinetic and thermodynamic properties.

Bi-functional amperometric biosensor for low concentration hydrogen peroxide measurements using polypyrrole immobilizing matrix

Effect of Glucose Oxidase Immobilizing Techniques on Performances of Nano Scale Polypyrrole Glucose Biosensors

Sensor Network Applications in Structures – A Survey