Conductive Hydrogel-Based Electrochemical Sensor: A Soft Platform for Capturing Analyte

Abstract

Electrode modifications for electrochemical sensors attract a lot of attention every year. Among them, hydrogels are a relatively special class of electrode modifier. Since hydrogels often contain polymers, even though they are conductive polymers, they are not ideal electrode modifiers because of their poor conductivity. However, the micro-aqueous environment and the three-dimensional structure of hydrogels are an excellent platform for immobilizing bioactive molecules and maintaining their activity. This gives the hydrogel-modified electrochemical sensor the potential to perform specific recognition. At the same time, the rapid development of nanomaterials also makes the composite hydrogel have good electrical conductivity. This has led many scientists to become interested in hydrogel-based electrochemical sensors. In this review, we summarize the development process of hydrogel-based electrochemical sensors, starting from 2000. Hydrogel-based electrochemical sensors were initially used only as a carrier for biomolecules, mostly for loading enzymes and for specific recognition. With the widespread use of noble metal nanoparticles and carbon materials, hydrogels can now be used to prepare enzyme-free sensors. Although there are some sporadic studies on the use of hydrogels for practical applications, the vast majority of reports are still limited to the detection of common model molecules, such as glucose and H2O2. In the review, we classify hydrogels according to their different conducting strategies, and present the current status of the application of different hydrogels in electrochemical sensors. We also summarize the advantages and shortcomings of hydrogel-based electrochemical sensors. In addition, future prospects regarding hydrogel for electrochemical sensor use have been provided at the end.

Algal Polysaccharides-Based Hydrogels: Extraction, Synthesis, Characterization, and Applications

“…Changes in pH, temperature, and ion concentration are common in vivo or in different parts of human bodies; as such, hydrogels sensitive to those external triggers are ideal candidates for controlled drug delivery [ 232 ]. Additionally, hydrogels that can respond to molecules, light, pressure, moisture, and electrical signals also show promising potential in controlled delivery systems, biosensors, and bioseparation [ 233 , 234 ]. For the sensitive test, an equilibrium in the water content is introduced.…”

Shaping Macromolecules for Sensing Applications—From Polymer Hydrogels to Foldamers

“…Such phase transition results in changing hydrogel properties, e.g., swelling, collapse, or solution-to-gel transition, transparency, and conductivity, which can be exploited to construct sensor probes [ 7 , 24 , 56 ]. They can change their properties under external inputs, e.g., the presence of particular ions [ 61 ] or bioactive molecules, pH [ 62 , 63 , 64 ], temperature [ 65 ], light radiation [ 66 ], electric [ 67 , 68 ] or magnetic [ 69 , 70 ] fields, etc. [ 71 ].…”

Recent Implementations of Hydrogel-Based Microbial Electrochemical Technologies (METs) in Sensing Applications

“…Hydrogel networks can either be chemically or physically crosslinked, ensuring structural stability during water absorption [ 15 ]. This allows the hydrogel to immobilise the biological substrate as well as create a microenvironment in which the analyte can be confined, thus improving the sensitivity [ 16 ]. These properties make hydrogels extremely suitable for electrochemical biosensing applications and development [ 17 ].…”