Preparation And Performance Of Tannic Acid-based Antioxidant Antibacterial Hydrogels With NIR/pH Response

Hydrogels with good biocompatibility and biodegradability are a promising biomedical materials in the future.They have been applied in wound dressings,sustained drug release,gingival tissue regeneration and bone repair.However,the existing hydrogels have some technical defects such as poor mechanical properties,weak tissue adhesion and easy bacterial contamination,which may lead to wound infection when applied.Currently,the problem of wound infection is mainly solved by combining adhesive hydrogels with antibiotics,but the abuse of antibiotics will bring the risk of bacterial resistance,cytotoxicity and poor cell affinity.In recent years,the development of new adhesive antibacterial hydrogels without antibiotics has attracted extensive attention.Compared with the weak tissue penetration ability of UV light and its potential carcinogenic risk,as well as the low power and efficiency of visible light,NIR light has attracted much attention due to its advantages of good tissue penetration and almost no damage to tissue,so the synergistic antibacterial strategy of introducing NIR light into hydrogels can effectively play its advantages.Thus,we designed and developed two types of antibacterial and antioxidant hydrogels with potential application of wound dressings,in which the release of antibacterial agents is responsive to p H stimulation,and under the synergistic antibacterial action of NIR light,the highly effective antibacterial and anti-inflammatory effect is achieved,and the bacterial resistance is expected to be further reduced.The specific research contents and results are as follows:1.Preparation and properties of Gel-OD-TA@Fe³⁺hydrogelThe ideal hydrogel dressing should have good biocompatibility,low toxicity and antibacterial activity to effectively prevent wound infection and accelerate wound healing.Our design idea is to synthesize hydrogels from biological macromolecular proteins and polysaccharide macromolecules by a simple method,and at the same time introduce non-resistant antimicrobial agents with near-infrared light response,thus endowing hydrogels with excellent antibacterial activity.Herein,Gel-OD-TA@Fe³⁺antibacterial hydrogel composed of gelatin（Gel）,oxidized glucan（ODex）,and tannic acid/iron chelate(TA@Fe³⁺)was prepared by reversible Schiff base bond crosslinking method,and their structure,morphology and properties were characterized and analyzed.The results showed that the release of TA in Gel-OD-TA@Fe³⁺was responsive to p H stimulation,and the release of TA in acidic environment was significantly higher than that in neutral or alkaline environment.Due to the introduction of TA@Fe³⁺under NIR irradiation,on the one hand,it can rapidly absorb energy and increase local temperature;on the other hand,it promotes the release of TA and achieve the controlled release effect of near-infrared light.Based on the synergistic antibacterial effect of the two,the sterilization rate of Gel-OD-TA@Fe³⁺to E.coli and S.aureus is over 99%,and it also has antioxidant and hydroxyl radical scavenging functions,which would effectively prevent bacterial infection and prevent free radical damage to healthy tissues.2.Preparation and properties of PAM/GM/Cu₂O-TA hydrogelIt was found that TA@Fe³⁺has good antibacterial activity and excellent photothermal conversion ability,while TA@Fe³⁺has catalytic initiation performance for common initiators（such as APS）.Therefore,Gel MA,AM,TA@Fe³⁺and Cu₂O-TA were used as raw materials to prepare antibacterial hydrogels with high strength and adhesion initiated by TA@Fe³⁺auto-catalysis polymerization of acrylamide monomer,and the synthesized hydrogels were systematically and completely studied and characterized.The results show that the synthesized Cu₂O-TA nanoparticles are spherical with uniform size and high stability.PAM/GM/Cu₂O-TA hydrogel has a high bactericidal effect and an obvious p H response to the release of TA and copper ions.In addition,PAM/GM/Cu₂O-TA could trigger the release of more TA and copper ions under near-infrared light.Due to the synergistic effect of near-infrared light,the antibacterial effect is further strengthened,and the excellent antibacterial effect can be achieved with lower TA and Cu₂O-TA content,which is expected to reduce the resistance of bacteria.PAM/GM/Cu₂O-TA hydrogel also show good antioxidant properties,which will be beneficial to the antioxidant effect of the wound.In summary,we constructed antibacterial hydrogels with multiple antibacterial strategies through different preparation methods,introduced near-infrared light synergistic antibacterial,and realized efficient bactericidal and antioxidant effects,providing new ideas and new approaches for solving technical bottlenecks such as wound infection,accelerating wound healing and reducing bacterial drug resistance.