Electrochemical Wearable Biosensors and Bioelectronic Devices Based on Hydrogels: Mechanical Properties and Electrochemical Behavior

Abstract

Hydrogel-based wearable electrochemical biosensors (HWEBs) are emerging biomedical devices that have recently received immense interest. The exceptional properties of HWEBs include excellent biocompatibility with hydrophilic nature, high porosity, tailorable permeability, the capability of reliable and accurate detection of disease biomarkers, suitable device–human interface, facile adjustability, and stimuli responsive to the nanofiller materials. Although the biomimetic three-dimensional hydrogels can immobilize bioreceptors, such as enzymes and aptamers, without any loss in their activities. However, most HWEBs suffer from low mechanical strength and electrical conductivity. Many studies have been performed on emerging electroactive nanofillers, including biomacromolecules, carbon-based materials, and inorganic and organic nanomaterials, to tackle these issues. Non-conductive hydrogels and even conductive hydrogels may be modified by nanofillers, as well as redox species. All these modifications have led to the design and development of efficient nanocomposites as electrochemical biosensors. In this review, both conductive-based and non-conductive-based hydrogels derived from natural and synthetic polymers are systematically reviewed. The main synthesis methods and characterization techniques are addressed. The mechanical properties and electrochemical behavior of HWEBs are discussed in detail. Finally, the prospects and potential applications of HWEBs in biosensing, healthcare monitoring, and clinical diagnostics are highlighted.

Challenges and Advances of Hydrogel-Based Wearable Electrochemical Biosensors for Real-Time Monitoring of Biofluids: From Lab to Market. A Review

“…56 Cross-linking mechanisms are integral to tailoring the mechanical and physicochemical properties of hydrogels, and their understanding is crucial for harnessing the full potential of HWEBs (Table 1). 26 The cross-linking methodologies can be classified into two main categories including physical and chemical cross-linking, as described in the following subsections.…”

“…78 The electrical conductivity of hydrogels is of prime importance because it significantly influences the electrochemical sensing performance through effective electron transfer between the biological sensing element and the electrode surface. 26 This approach has been used to deposit several conductive polymers such as poly-(acetylene), poly(ethylene dioxythiophene), poly(p-phenylenevinylene), poly(pyrrole), and poly(aniline). 77 The electrodeposition method facilitates the in situ formation of a uniform layer of a hydrogel-based electrode on the surface with controlled thickness.…”

“…The sensitivity and precision of HWEBs are closely linked to their exceptional electrocatalytic and biological performance, as well as their ability to store sweat. 26 For instance, composite hydrogels can enhance the conductivity and accessibility of the target to detect adsorbed biological molecules, thereby increasing biosensor sensitivity. 101 Lin et al have developed a noninvasive sweat glucose sensor that utilizes multiple layers of conductive PB−PEDOT hydrogels, GOx immobilization layer, and a protective layer made of Nafion.…”

“…25 In our previous review paper, we extensively explored the mechanical properties and electrochemical behaviors of hydrogel-based wearable electrochemical biosensors. 26 Building on that foundation, this review focuses on assessing the diverse fabrication methods of hydrogels for use in HWEBs. We also delve into the practical application of HWEBs in biofluids.…”

“…Currently, there is a substantial enthusiasm for the application of HWEBs in healthcare monitoring . In our previous review paper, we extensively explored the mechanical properties and electrochemical behaviors of hydrogel-based wearable electrochemical biosensors . Building on that foundation, this review focuses on assessing the diverse fabrication methods of hydrogels for use in HWEBs.…”