# Carbon Nanotubes-Based Hydrogels for Bacterial Eradiation and Wound-Healing Applications
## 3 Development of CNT-Based Conductive Hydrogels  
Hydrogels comprise a 3D cross-linked polymeric network structure, holding a large amount of water and maintaining their form even after swelling. Hydrogels are similar to the extracellular matrix and can mimic the microstructure of native cellular environments and provide a moist environment [21]. It can adsorb the fluid excreting from the wound  
Figure 2: Surface and internal view of (**a**) single-walled CNTs, (**b**) double-walled CNTs, and (**c**) multi-walled CNTs [51]. through the porous structure and prevent the growth of anaerobic bacteria by the gaseous exchange phenomenon. It can act as a barrier to prevent bacterial infections and improve epithelization and cell migration into the wound [22; 56; 57; 58; 59; 60]. Hence, hydrogel materials have been broadly used for wound dressing.Conductive hydrogel has received significant attention for various biomedical applications, including wound dressings, drug delivery, biosensors, bio-imaging, and tissue engineering. The hydrogel conductivity is originated due to the presence of conductive ions and electrons. Naturallyderived biopolymers, such as chitosan, peptides, gelatin, and polyamines, are frequently explored to prepare hydrogels due to their excellent biocompatibility [29]. Recently, [PERSON] et al., developed injectable antibacterial hydrogels for enhanced skin generation. The injectable hydrogel has certain advantages, such as wound site filling with irregular space, wound adherence, and feasibility toward the insitu encapsulation of bioactive molecules and cells [30]. These hydrogels can be designed with advanced features such as bilayer types to control the infiltration of microbes and moistures and additional antibacterial and antimicrobial properties to protect wound sites from infections and inflammations. Different stimuli-responsive properties can be generated in hydrogel to deliver therapeutic molecules, inhibit bacterial infections, and promote cellular proliferation. Multifunctional hydrogels are an emerging approach. It is the composition of hydrogel constituent materials with or without modification and the incorporation of nanostructures in the hydrogels. These construction strategies improve properties (electrical, mechanical, surface, biocompatibility, and biodegradability) for wound-healing applications [61; 62; 63; 64; 65]. [PERSON] et al., summarized the literature to fabricate different types of hydrogel material with antibacterial agents for wound-healing applications [29]. They included the types of hydrogels and their specific methods of incorporations such as physical combination (incorporation, swelling diffusion, encapsulated with carrier), chemical combinations (chemical bonding, hydrogel with biomedicine activity), and incorporation of photo-assisted antibacterial hydrogels. The physical combination of antimicrobial methods has been considered a straightforward and effective method, in which hydrogel was physically incorporated with antibiotics, biological extracts, antimicrobial peptides, and inorganic nanoparticles. These materials are utilized for wound healing and other biomedical treatments. In chemical combinations, the hydrogel is combined with an antibacterial and antimicrobial agent by chemical treatments. However, these hydrogel derivatives should go through further purification steps before their utilizations. The chemical combination method has been commonly used to synthesize CNT-based hydrogels, and the most common hydrogels are chitosan-based, cationic group-based, polypeptide-based, and halogen-based hydrogels. These hydrogels exhibit strong antibacterial and antimicrobial properties, which are necessary to heal the wound [59] effectively. However, several researchers are developing new hydrogel materials to fulfill their demand in biomedical applications [29; 66; 67; 68; 69]. The following sections highlight some recent studies and developments of CNT hydrogels for wound healing and antibacterial property.