Towards braided shape memory polymer surgical sutures

Abstract

Surgical sutures are used for wound closure in surgeries and injuries by bringing the edges of an open wound together. Conventional way of applying surgical sutures is to secure the wound with surgical knots and tight stitches. Compared to conventional ones, braided sutures have advantages in terms of pliability, handling, and knot security. Some of the typical suture materials are chromic/plain catgut, silk, and syntheticpolymers such as polyglactin and polyamide. In this study, a type of smart material, namely shape memory polymer (SMP), is proposed as an alternative surgical suture material to produce braided sutures that can be stitched loosely and are able to self-tighten when their shape memory effect (SME) is activated. Mechanical and SME properties of SMPs can be improved by reinforcing them with cellulose nanocrystals (CNCs) which is a biocompatible nanosized material that offers high mechanical properties. In the present study, braided SMPs and CNC reinforced SMPs are produced. The effect of braiding parameters along with effect of the amount of CNC wt% in SMPs are investigated through a series of experiments to analyze mechanical and SME properties. The results indicated that mechanical properties reduced with increasing braid angle. A prediction model for the elastic modulus of braided SMPs were adopted and accurate results were obtained between the predicted and experimentally obtained values. Shape recovery rate decreased with increasing number of core filaments, whereas maximum shape recovery was not affected by any of the braiding parameters. Recovery stresses were similar with the exception of braids with three core filaments where they showed poorer performance. Addition of CNC reduced the mechanical performance of the braids, while SME properties were improved. Recovery stresses increased by 100.5% when the braids made of neat SMP and SMP with 4.0 wt% CNC were compared. Although elastic moduli of all type of braids were comparable to that of commercially available sutures, relatively poor tensile strength should be addressed.