Antibacterial Sutures Coated with Smooth Chitosan Layer by Gradient Deposition

Owing to the significant importance in clinics, antibacterial activity is thought as one indispensable feature of the next generation of absorbable sutures. It is challenging but imperative to arm the existing absorbable sutures with antibacterial functions. The present study describes a “gradient deposition” technique to coat a continuous and smooth layer of chitosan on the surface of absorbable sutures. Specifically, chitosan solution is arranged to undergo gradient pH decline step by step while during each pH interval, the solution is allowed to stand for a predetermined period of time in order to control gradual chitosan deposition. Chitosan nanoparticles are found to be first generated on suture surface and finally developed into a smooth chitosan layer as the antibacterial surface. In vitro and in vivo results demonstrated that coating chitosan on sutures by our technique could relieve wound inflammation, stimulate collagen deposition, regenerate blood vessels, and assist tissue repairing, consequently leading to a significant enhancement of wound healing effect. This technique is highlighted with low cost, extreme convenience and excellent safety without organic solvents. Furthermore, the “gradient deposition” technique would not affect the fundamental properties of matrix and thus hold promises as a universal way for superficial antibacterial modification towards almost all the surgical implanted materials, including but not limited to absorbable sutures.