Nanomaterial-based biohybrid hydrogel in bioelectronics

Abstract

Despite the broadly applicable potential in the bioelectronics, organic/inorganic material-based bioelectronics have some limitations such as hard stiffness and low biocompatibility. To overcome these limitations, hydrogels capable of bridging the interface and connecting biological materials and electronics have been investigated for development of hydrogel bioelectronics. Although hydrogel bioelectronics have shown unique properties including flexibility and biocompatibility, there are still limitations in developing novel hydrogel bioelectronics using only hydrogels such as their low electrical conductivity and structural stability. As an alternative solution to address these issues, studies on the development of biohybrid hydrogels that incorporating nanomaterials into the hydrogels have been conducted for bioelectronic applications. Nanomaterials complement the shortcomings of hydrogels for bioelectronic applications, and provide new functionality in biohybrid hydrogel bioelectronics. In this review, we provide the recent studies on biohybrid hydrogels and their bioelectronic applications. Firstly, representative nanomaterials and hydrogels constituting biohybrid hydrogels are provided, and next, applications of biohybrid hydrogels in bioelectronics categorized in flexible/wearable bioelectronic devices, tissue engineering, and biorobotics are discussed with recent studies. In conclusion, we strongly believe that this review provides the latest knowledge and strategies on hydrogel bioelectronics through the combination of nanomaterials and hydrogels, and direction of future hydrogel bioelectronics.

Keywords: Bioelectronics; Biohybrid hydrogel; Biorobotics; Flexible devices; Nanomaterial.

Fig. 1

Schematic diagram of nanomaterial-based biohybrid hydrogel in bioelectronics to develop flexible/wearable bioelectronic device, tissue engineering, and biorobot

Fig. 2

a Schematic diagram of the localized surface plasmon resonance (LSPR) shift on Au nanomaterials depending on their different shapes (nanosphere, prism, cube, star, or rod). Reproduced with permission from [30], copyright MDPI, 2020. b Schematic images of the structures of representative allotropes of carbon nanomaterials. Reproduced with permission from [34], copyright American Chemical Society, 2015. c Schematic illustration of the crystal structure of MoS₂, which consists of a transitional metal (Mo) atomic layer sandwiched between two chalcogen (S) atomic layers. Reproduced with permission from [37], copyright American Chemical Society, 2015. d Schematic illustration of the atomic structure and constituting elements of the Ti₃C₂T_x MXene. Reproduced with permission from [39], copyright American Chemical Society, 2018

Fig. 3

a Schematic diagram of the control of hydrogel stiffness by manipulating the crosslinking density using DNA crosslinkers. Reproduced with permission from [56], copyright John Wiley and Sons, 2021. b Schematic and optical images of nitro-dopamine-modified MNP incorporated into a collagen-based hydrogel, and SEM image of its internal microstructure. Reproduced with permission from [67], copyright American Chemical Society, 2016. c Schematic and optical images of an rGO-based hydrogel nanocomposite and its application for the growth and differentiation of myoblasts. Reproduced with permission from [69], copyright Elsevier, 2016

Fig. 4

a Schematic image for the development process of pure regenerated cellulose-based hydrogel (PGC bionanosheet-assembled hydrogel (PGCNSH)) via chemical crosslinking of a (PGO)-hybridized cellulose bionanosheet (PGCNS) by using ECH. Reproduced with permission from [70], copyright John Wiley and Sons, 2021. b Scheme and optical images of artificial electronic skin composed of engineered silk protein hydrogel, ZnO NRs, and Ag NWs, and its flexibility and adhesion properties. Reproduced with permission from [77], copyright Elsevier, 2020. c Optical image and biosensing mechanism of a wearable electrochemical glucose biosensor composed of a transparent nanofiber-type hydrogel with encapsulated Au NPs and GOx, and d Schematic illustration of the steps for developing a transparent nanofiber-type hydrogel with encapsulated Au NPs and GOx for use in electrospinning. Reproduced with permission from [83], copyright Springer Nature, 2020

Fig. 5

a Schematic diagram of a visible-light-mediated nano-biomineralization method for the synthesis of BTH through the photocatalytic activity of ruthenium. Reproduced with permission from [88], copyright American Chemical Society, 2022. b Schematic images of the fabrication process of GelMA-BP@Mg composed of GelMA and BP@Mg and exhibiting the photothermal properties of the GelMA-BP@Mg. Reproduced with permission from [90], copyright John Wiley and Sons, 2021. c Schematic images of the fabrication process of ECM-Au NP-based composite hydrogel and encapsulation of cardiac cells for heart disease (ischemia–reperfusion) treatment. Reproduced with permission from [94], copyright John Wiley and Sons, 2021

Fig. 6

a Schematic diagram of a conductive hydrogel electrode with a 3D tissue model for the application of electrical stimulation to induce muscle contraction. Reproduced with permission from [104], copyright John Wiley and Sons, 2020. b Schematic diagram of a wirelessly powered 3D-printed hierarchical biohybrid robot composed of four parts: (i) A CNT/GelMa hydrogel layer for the elastic body, (ii) stretchable wirelessly-powered bioelectronics for cell stimulation, (iii) 3D-printed accordion-inspired scaffolds, and (iv) iPSC-derived muscle tissues. Reproduced with permission from [106], copyright John Wiley and Sons, 2022. c Schematic diagram of the actuation process of an electroactive nanobiohybrid actuator composed of MoS₂ nanosheets and a hydrogel-based skeletal muscle structure. Reproduced with permission from [108], copyright Springer Nature, 2022. d Schematic diagram of a biohybrid robot composed of HA-Au NPs-embedded muscle hydrogel. Reproduced with permission from [110], copyright American Chemical Society, 2022