Preparation And Properties Of Highly Adhesive Polyvinyl Alcohol Hydrogels Based On ?-cyclodextrin

Hydrogels are soft and flexible three-dimensional materials with high water contents,they have good compatibility with biological tissue,and have been very appealing in the field of medical industry,especially for wound dressing materials,and gradually become a research hotspot in recent years due to the strong tunability of their functionalities.However,the current wound dressing hydrogels often have limited adhesion and poor mechanical properties,which greatly restricts their applications.As a derivative of natural starch,?-cyclodextrin(?-CD)has special physicochemical properties and the advantages of easily available materials,environmental friendliness and low cost,and has attracted increasing attention in the research of medication.In this paper,?-CD was introduced into the hydrogel network of polyvinyl alcohol(PVA),due to the characteristic features of?-CD,such as hydrophilic outer wall,hydrophobic inner cavity and strong hydrogen bonding capability.It can not only effectively solubilize hydrophobic drug in aqueous solution,but also give hydrogels high adhesion properties.In this paper,PVA was used as the skeleton of the gel,?-CD was used as the functional enhancement component,and silica nanoparticles(SiO₂)and polydopamine(PDA)were employed to enhance the gel's mechanical behavior.Eventually,curcumin(Cur)-?-CD/PVA/SiO₂ antibacterial adhesive hydrogels and PVA/?-CD/PDA bio-based conductive adhesive hydrogels were prepared through the freezing-thawing method,and their mechanical properties,adhesion and antibacterial/conductive properties were explored..The main research contents are divided into the following three parts:1.The Cur was encapsulated in the?-CD by the host-guest interaction between?-CD and natural antibacterial Cur,and the complex was introduced into the PVA-based hydrogel by taking the advantage of the hydrophilicity of?-CD.By adding SiO₂nanoparticles as structural reinforcement fillers in the hydrogel,the environmentally friendly physically crosslinked antibacterial composite hydrogel was successfully prepared.Various methods were used to explore the effects of different components on the mechanical and adhesion properties of hydrogels.Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and X-ray diffraction(XRD)were used to characterize the structure of the hydrogel.The mechanical and adhesive properties of the hydrogel were characterized by a texture analyzer.The experimental results show that the PVA/?-CD/SiO₂ hydrogel is a three-dimensional physical cross-linked network mainly formed by the crystallization structure of PVA molecular chain in the freezing process as well as the hydrogen bonding generated between SiO₂ and PVA and?-CD in the gel network.In addition,the addition of?-CD can reduce the mechanical properties of the gel for the possible reason that the strength of entanglement,crystallization and hydrogen bonds of the rigid?-CD are weaker than those interactions of PVA molecules,thereby reducing the interactions in the three-dimensional network of the composite gel.After the addition of SiO₂ nanoparticles,the mechanical properties of the gel structure were significantly improved with the strength increased from 112.0 k Pa to 562.0 k Pa and the elongation at break increased by nearly two times compared with the samples without SiO₂ particles,which clearly indicates that SiO₂ particles can act as physical crosslinking points in the gel system to improve the crosslinking density and interactions of the system and thus strengthen the mechanical properties of the gel network.The adhesion test results show that the introduction of SiO₂ nanoparticles has no significant effect on its adhesion,while the introduction of?-CD effectively endows the hydrogel with high adhesion.The adhesion strengths of the hydrogel samples reinforced by?-CD reach 33.32 k Pa,23.57 k Pa and15.74 k Pa on metal,glass and porcine skin,respectively.2.The characteristics of PVA/?-CD-Cur/PDA hydrogels,such as water retention rate,swelling ratio,drug-release kinetics and antibacterial properties,were studied.The experimental results show that the water retention performance has been significantly improved with the addition of SiO₂ nanoparticles and the swelling rate is also increased,which can be conducive to the improved the absorption capacity of dressing hydrogel for exudate intake from the wound.In addition,the composite hydrogel has good sustained-release performance within 24 h,which means the slow and safe release of drug molecules,and thus is helpful for the sustained and stable efficiency of drugs.The results of in vitro antibacterial test show that the hydrogel has good antibacterial properties against Escherichia coli(Gram-negative bacteria)and Staphylococcus aureus(Gram-positive bacteria).3.In order to further expand the functionality and application of the composite hydrogels,the composite hydrogels based on PVA/?-CD/PDA were further prepared.The effects of PDA component on the mechanical properties and electrical conductivity of the hydrogel were investigated,and the fatigue resistance of the hydrogel was tested.The experimental results show that PDA can improve the mechanical strength and electrical conductivity of hydrogel simultaneously,which provides an approach for the preparation of wearable flexible sensing gel.