Development of bioresorbable polycaprolactone composite mesh for antimicrobial control release and haemostatic properties

Abstract

Tissue traumas are often prone to complications such as haemorrhages and inflammation, which can hinder healing. The challenge is to develop a system that curbs these problems by providing haemostatic and localized controlled antimicrobial effects. The strategy developed in this study involves using a haemostatic fused deposition modeled (FDM)-formed mesh composed of Polycaprolactone (PCL) and 20wt% tricalcium phosphate (TCP), loaded with a model antimicrobial drug, gentamicin sulfate (GS; 15wt%), that will be released within a short duration to inhibit bacterial activity without affecting subsequent tissue regeneration. This platform technology can be applied to a variety of applications requiring interventions of haemostasis and drug elution.

A series of in vitro and in vivo experiments were conducted to optimize and characterize this drug eluting haemostatic mesh¿s drug eluting and haemostatic aspect. Haemostatic effect was preliminarily evaluated through optimizing the FDM-formed PCL-TCP mesh (85% porosity, 1mm thickness) for blood absorption.

PCL was observed to promote platelet adhesion and activation, more prominently than glass positive control. Although in terms of contact activation, PCL performed poorer than glass, it was still regarded as a relevant haemostat as it showed significant haemostatic properties comparing to negative control.

Upon adding TCP, both surface chemistry and topography were altered. To isolate surface topography effect, experimentations on gold sputtered specimens showed a decrease in platelet adhesion with increased surface roughness due to increasing TCP incorporation (0-25wt%). When evaluated with surface chemistry effect, it yielded a general increase in platelet coverage with increasing TCP content. In the balance of the two aspects, PCL with 20wt% TCP was selected for its optimal platelet adhesion.

Architectural influence to haemostasis was also studied by comparing micro-scaled (FDM), sub-micron (nanofibers) and macro-scaled (film) architectures. It was shown that FDM-formed PCL structures had comparable blood contact activation and platelet adhesion to glass, justifying its use for this system.

For the antimicrobial aspect, the incorporation of GS was optimised. 15wt% GS incorporation rendered most efficient even with bacterial reinoculations. 93% of total GS was released within 168 hours and was found to be non-cytotoxic to human dermal fibroblast. The burst release can be attributed to the hydrophilic surfaces caused by high TCP content in the FDM-formed mesh, with direct relation found between GS release rate and TCP content. Therefore, TCP content of 20wt% was once again chosen for optimum GS release during the critical infectious period while allowing subsequent tissue regeneration.

When tested against gauze using an infected full-thickness wound mice model, the mesh eliminated the bacteria in wound effectively with no observable signs of overall infection after 7 days, led to excellent wound healing with 94.2% reduction in wound area by day 14 and stimulated faster wound healing as indicated from the improved neo-collagen deposition and re-epithelisation.

In conclusion, the drug eluting haemostatic mesh was successfully developed using FDM technique. Besides haemostatic potential, this mesh was also showed to be an effective drug delivery platform for GS in both in vitro and in vivo environment and heal infected wounds more rapidly when compared to gauze.