Antibacterial agents have become widely used in various products, such as hand sanitizers, disinfectants, and cleaning solutions.[1] Using antibacterial agents only when appropriate can help reduce the potential negative impacts on traffic and public health.[2–4] In order to maximize the efficiency of antibacterial properties, it is necessary to utilize antibacterial agents that are specifically designed and integrated for the appropriate niche. Hydrogel has been approved as an excellent niche due to its water-swollen, crosslinked polymer network, which that is widely used in various fields, including cancer therapy, antibacterial agents, etc.[5–9]
The hydrogel can be made from synthetic or natural polymers, such as polyethylene glycol, polyvinyl alcohol, or hyaluronic acid, among others.[10] One of the most significant advantages of hydrogel is its ability to absorb and retain large amounts of water. This property makes it an excellent material for wound healing, as it helps maintain a moist environment that facilitates faster healing.[11] Additionally, hydrogels have been shown to have excellent biocompatibility and low toxicity, making them an ideal option for use in various medical applications, including tissue engineering and drug delivery systems.[12] Hydrogels are also used in agriculture, where they can be used to improve crop yields and reduce water usage.[13] Hydrogel-based soil amendments can improve soil structure and water retention capacity, which helps plants grow in water-stressed environments. Additionally, hydrogels can be used to release fertilizers and pesticides in a controlled manner, reducing environmental contamination and increasing the effectiveness of these chemicals.[14] In engineering, hydrogels are used to develop smart materials that respond to environmental stimuli such as temperature, pH, or light. These materials have applications in areas such as sensors, actuators, and drug delivery systems.[15]
Hydrogel can be created through several methods, depending on the desired properties and applications of the final product. One of the most common methods is free-radical polymerization, which involves crosslinking monomers under the influence of free radicals. This process typically involves the use of a crosslinking agent, such as ethylene glycol dimethacrylate, and a free-radical initiator, such as ammonium persulfate.[16] Another method for creating hydrogel is through physical crosslinking, which involves using physical interactions, such as hydrogen bonding or electrostatic interactions, to form a polymer network. This method typically involves the use of natural polymers, such as chitosan or hyaluronic acid, and requires no chemical crosslinking agents or initiators.[17] A third method for creating hydrogel is through ionotropic gelation, which involves the use of ionic interactions to crosslink polymers. This method typically involves the use of a cationic polymer, such as chitosan, and an anionic crosslinking agent, such as tripolyphosphate, sulfobetaine.[18–22]
As we known, maleimide-thiol conjugation is a popular method for crosslinking hydrogels that involves the reaction of a maleimide functional group with a thiol functional group.[23–25] This method is widely used in the synthesis of hydrogels for biomedical applications, including drug delivery systems and tissue engineering.
Maleimide functional groups have a high affinity for thiol groups, making them an ideal choice for crosslinking hydrogels. The reaction between the maleimide and thiol groups forms a covalent bond, resulting in a stable crosslinked network. The reaction can be performed under mild conditions, which minimizes the risk of damage to bioactive molecules or cells encapsulated within the hydrogel.[26] One of the advantages of using maleimide-thiol conjugation to crosslink hydrogels is its high specificity. The reaction only occurs between maleimide and thiol groups, which reduces the likelihood of non-specific binding or unwanted reactions.[27] Another advantage of this method is its versatility. Maleimide functional groups can be incorporated into a variety of polymers, including synthetic and natural polymers, to create hydrogels with tailored properties. Additionally, thiol functional groups can be easily introduced into biomolecules, such as peptides or proteins, allowing for the creation of hydrogels with biologically active components.[28]
However, previous investigated hydrogels based on maleimide-thiol conjugation have many existing defects, including toxicity and slow gelation time. For instance, a typically example is from Zeng etc., who created a novel chitosan-PEG hydrogels from maleimide-thiol conjugation.[29] However, they utilized initiator UV lamp, which could be harmful to the cells in the biomedical application. And the gelation time at least 30 seconds with very high amount 20% precursors.
To conquer both defects mentioned above, in this paper, we selected two biocompatible nature materials chitosan and dextran. Then, we functionalized chitosan and dextran with shorter chain thiol groups and maleimide groups. Also, we didn’t use the initiator due to its toxicity. Meanwhile, we investigated conjugated hydrogel with its gelation speed, swelling behavior, viscoelastic property, degradation rate and antibacterial properties.