Smart Sutures

The primary aim of this PhD is to develop a 'Smart Suture' that will help prevent postoperative infections. Sutures are use in most surgical procedures, to close wounds and repair tissues damaged by trauma or surgical intent. Septic complications frequently arise at the site of wound trauma, including superficial wound infections and deep infections.

The aim of the 'Smart Suture' is to develop a novel method for antimicrobial drug delivery as soon as there is a sign of surgical site infection. Sutures are almost always present at surgical site infections, and are therefore the ideal carrier for an antimicrobial agent. The objective is to adapt existing polymer technology for targeted drug delivery to the "at risk" surgical site. Our novel idea is to use sacrificial threads, which are hollow threads made of long chain polymers that are filled with fluid monomers. These monomers can flow into any gaps, created if a breakage occurs, and solidify. Here we would adapt the idea where the internal monomers can be replaced by small microcapsules that contain an anti-microbial agent. If a large shear force is applied to a suture, the thread would break and release an anti-microbial agent. Alternatively, the sutures may not break, but simply stretch under tension of the healing wound. Sutures would be fabricated such that they contain dehydrated microcapsules containing anti-microbial drugs. Upon rehydration in the tissues the microcapsules would rehydrate, creating large pores in the microcapsule shell, allowing the encapsulants to diffuse out of the microcapsule into the surrounding environment to exert their biological effect. When the suture is stretched, the surface area in contact with the aqueous environment increases and so many more microcapsules can be rehydrated releasing their beneficial cargo. As bacterial infections can also cause pore formation in lipid membranes, we will explore lipid-based capsules as an alternative means of sustained release of anti-microbial drugs. This mechanically triggered release however is not the only delivery mechanism that could be utilised. Microcapsule stability is highly dependent upon its material composition which may be functionalised to degrade upon exposure to enzymes or exotoxins produced by infections. This opens up the possibility of impregnating surgical implants that may benefit from sustained anti-microbial delivery, such as prosthetic meshes commonly used in a variety of tissue repairs. Continuous delivery would be of immense benefit in this scenario because mesh infection is a serious complication, frequently necessitating removal of the prosthesis.
The concept of impregnating biological materials with a sustained antimicrobial release system is attractive to many clinical applications. The idea of a drug release mechanism based on rehydration of a microcapsule is novel. The project has been developed out of an unmet clinical need identified during a Leeds NIHR Healthcare Technologies Co-operative (HTC) networking event, and will continue to receive support from the HTC.