In vitro assessment of an antibacterial quaternary ammonium-based polymer loaded with chlorhexidine for the coating of polypropylene prosthetic meshes

Purpose

This study assesses the use of an absorbable polymer loaded with chlorhexidine (CHX) as an antibacterial coating for polypropylene (PP) meshes employed in hernia repair.

Methods

The polymer N,N-dimethyl-N-benzyl-N-(2-methacryloyloxyethyl) ammonium bromide was loaded with CHX (1 % w/w). Fragments (1 cm²) of Optilene^® Mesh Elastic were coated either with the unloaded (POL) or CHX-loaded polymer (POL–CHX). Uncoated fragments (PP) served as controls. The release kinetics of the POL–CHX coating was monitored by HPLC. Sterile fragments were placed on agar plates previously contaminated with 10⁶ CFU of Staphylococcus aureus (Sa) ATCC25923, Staphylococcus epidermidis (Se) ATCC12228, or Escherichia coli (Ec) ATCC25922 and incubated at 37 °C for 1/2/7 days. At each time point, inhibition halos were measured and bacterial adhesion to the meshes quantified by sonication and scanning electron microscopy. Coating cytotoxic effects were examined on cultured fibroblasts.

Results

The polymer coating gradually released CHX over 3 days. Inhibition halos were produced only around the POL–CHX-coated meshes and these were significantly smaller for Ec than Sa or Se (p < 0.01). While POL–CHX prevented bacterial adhesion to the mesh, the reduced bacterial yields over time were observed for the POL-coated versus control PP meshes (p < 0.001). By day 7, only Ec remained attached to the surface of control meshes. The POL coating was not cytotoxic, yet POL–CHX reduced the viability of cultured fibroblasts.

Conclusions

When loaded with the antiseptic CHX, this quaternary ammonium-based polymer coating released its contents in a controlled manner indicating its potential prophylactic use to reduce the risk of infection following PP mesh implantation.