Hydrogel Dressings Assembled With Gel Microparticles For Wet Tissue Repair

Bioadhesive hydrogels have been widely used in clinical practice as adhesives and sealants due to their simple operation,non-invasive adhesion,instant sealing and hemostasis,and effective shortening of surgical time.However,there are still three challenges which need to be solved:（1）Minimally invasive treatment is the first choice in clinical practice,it not only needs to solve the problem of gel delivery,but also requires the gel to exist stably in the body to provide sufficient time for the tissue to heal;（2）The existence of a hydration layer on the tissue surface is not conducive to the adhesion of hydrogels,so its wet adhesion performance needs to be further improved;（3）The mechanical strength of most bioadhesive hydrogels is insufficient to provide an effective sealing effect.Therefore,it is necessary to prepare a bioadhesive hydrogel that can be delivered in vivo,quickly adhered to wet tissue surfaces and possess strong mechanical properties while being stable in the in vivo environment.Therefore,on the basis of traditional prefabricated hydrogels,thesis proposes a design concept to prepare them into gel powders to solve the problem of in vivo delivery.Then,the adhesion mechanism of powdered hydrogels was preliminarily discussed.First,polyacrylic acid（PAA）,polyvinyl alcohol（PVA）,polyacrylamide（PAM）,sodium alginate（SA）,agarose（Agar）and tannic acid（TA）as raw materials,six kinds of hydrogel powders,PAA,PAA-SA,PAM-SA,PVA-SA,PVA-TA and PAA-Fe-Agar,were prepared.Then,the adhesion strength and stability of these hydrogels prepared based on pure chemical crosslinking and pure physical crosslinking were explored.The results show that compared with the pure chemically crosslinked powdered hydrogel,the pure physical crosslinking hydrogel has better adhesion strength but insufficient stability.Based on this,a physical and chemical double-crosslinked PAA-Fe-CS gel powders were prepared in thesis.The physical crosslinking was achieved by the coordination bond between PAA and Fe³⁺ions,and amide bond was formed between PAA and CS to achieve chemical cross-linking,resulting in stable and fast adhesion to wet surfaces.In the experiment,the adhesion mechanism of the powdered hydrogel was verified by laser confocal microscopy;the structure and morphology of the gel powder were analyzed by Fourier Transform Infrared Spectrometer and Scanning Electron Microscope;the adhesion strength,stability and biological characterizations indicated that the powder-prepared PAA-Fe-CS hydrogel had high adhesive strength,high stability,good biocompatibility and hemostasis;and through endoscopic simulation of in vivo wound repair,the feasibility of the powders in minimally invasive application was demonstrated;through spraying on the surface of a large piece of pig skin,the feasibility of its application in large-area wound repair was demonstrated.