One-step In-situ Preparation And Property Study Of Chitosan-Based Biomimetic Adhesives

The highly dynamic living environment determines that every one inevitably needs to actively(such as surgery)or passively(such as accidental injury)face tissue damage in their life cycle.However,traditional wound treatment methods(such as sutures and bone needles)are not only highly invasive,painful,poor in biocompatibility,but also frequently cause secondary damages,which seriously hamper the efficiency of wound treatment and the well-being of patients.As a result,tissue adhesives with simple operation,minimal invasiveness,meanwhile less likely to cause secondary injuries are expected to gradually replace traditional materials,therefore become promising materials for wound treatment.At present,hydrogels have been used in many fields,such as hemostatic and filling materials in surgical operations,shaping materials in plastic surgeries,and sustained drug release systems in other life science research.However,synthetic or biomimetic adhesives,as alternative methods of suture therapy,still have various problems,like tedious synthesis process,harsh storage requirements,and expensive cost,that make them difficult to be promoted on a large scale.Therefore,simplifying preparation process of tissue adhesives,and realizing the one-step in-situ preparation of adhesives are of great significance to further expand their clinical applications.In this paper,chitosan(CS),a natural basic amino polysaccharide with excellent biocompatibility,antibacterial and biodegradability,was chosen as the polymer backbone.3,4-dihydroxybenzaldehyde(DBA)and Fe3+were picked as the biomimetic groups and crosslinker respectively.Firstly,CS-DBA-Fe and CCS-Fe biomimetic adhesives were prepared by the one-step in-situ method and the traditional reductive amination strategy(RA strategy).Subsequently,inspired by pyrogallol groups in ascidian secretions,2,3,4-trihydroxybenzaldehyde(TBA),an analogue of TOPA,was introduced as new biomimetic groups,aiming to further improve adhesion strength,rheological and self-healing properties of the CS-TBA-Fe adhesives by increasing the contents of crosslinkable hydroxyl groups.Results showed that,compared with the reductive amination strategy,once mechanical mixing between chitosan-Fe3+ solution(CS-Fe)and catechol/pyrogallol(DBA/TBA)solution was completed through one-step in-situ method,a brown-color hydrogel can be instantly prepared in situ as results of Schiff base reaction between chitosan and biomimetic groups,plus oxidation-coordination dual interaction between Fe3+and catechol/pyrogallol groups.Notably,preparation time can be significantly shortened to a few minutes.In addition,hydrogels prepared by this method not only have higher preparation efficiency,but also require milder preparation conditions that can dramatically reduce the concentration of raw chitosan,biomimetic groups and Fe3+ solution.Finally,CS-TBA-Fe and CS-DBA-Fe adhesives can achieve adhesion strength of up to 60.3 kPa and 48.8 kPa in the pigskin adhesion test respectively,while maintaining excellent stability and surface adaptability.More intricately,with the inherent antibacterial activity of chitosan,TBA and Schiff base,one-step in-situ method can be utilized to achieve excellent bonding strength while endowing adhesives with excellent antibacterial activity and many other special properties,which provides a feasible technical route for the further development of multifunctional biomimetic adhesives.