Surgical medical meshes are key in recovery procedures for damaged-tissue surgeries – their flexible and conformable design holds muscles tight and reduces recovery time compared to sewing and stitching methods. However, these meshes carry the risk of bacterial contamination during surgery and formation of an infectious biofilm over mesh surfaces.

Biofilms impede antibiotic agents from reaching and attacking bacteria on the film, meaning antibiotic therapies could fail against resistant bacteria.

Post-surgery aseptic protocols have been implemented in the past, but none have completely eliminated bacteria.

Surgical implants, covered with gold nanoparticles (left) compared to the original surgical meshes (right).
Scanning electron microscope (SEM) micrographs of the S. aureus biofilm.

Institute of Photonic Sciences (ICFO) researchers Dr. Ignacio de Miguel and Arantxa Albornoz, led by Catalan Institution for Research and Advanced Studies (ICREA) professor at ICFO Romain Quidant, collaborated with researchers Irene Prieto, Dr. Vanesa Sanz, Dr. Christine Weis, and Dr. Pau Turon from medical device and pharmaceutical device maker B. Braun Surgical to devise a technique that uses nanotechnology and photonics to combat biofilms. Researchers developed a medical mesh with a chemically modified surface, allowing the mesh to anchor millions of gold nanoparticles that efficiently convert light into heat at localized regions.

In the in-vitro experiment, the surgical mesh was coated with millions of gold nanoparticles – using a scanning electron microscope (SEM) to observe a homogenous distribution of nanoparticles – and tested to ensure long-term stability of particles, non-degradation of material, and non-detachment or release of nanoparticles into the surrounding environment. Once the modified mesh was ready, it was exposed to S. aureus bacteria for 24 hours until a biofilm formed on the surface. It was then exposed to short, intense pulses of near-infrared light (800nm) for 30 seconds to ensure thermal equilibrium was reached. This treatment was repeated 20 times with 4 seconds of rest between each pulse. Discoveries included:

Illuminating the mesh at the specific frequency induced localized surface plasmon resonances in the nanoparticles – a mode that results in the efficient conversion of light into heat, burning the bacteria at the surface.
  • Biofilm bacteria that remained alive became planktonic cells, recovering their sensitivity or weakness toward antibiotic therapy and immune system response.
    • Increasing the amount of light delivered to the mesh’s surface caused dead bacteria to lose adherence and peel off.
    • Operating at near infrared light ranges was compatible with in-vivo settings, meaning that such a technique would likely not damage the surrounding healthy tissue.
    • Recurrent heating of the mesh did not affect its conversion efficiency capabilities.
    • “The study’s results have paved the way toward using plasmon nanotechnologies to prevent the formation of bacterial biofilm at the surface of surgical implants,” Quidant says. “Several issues still need to be addressed, but it is important to emphasize that this technique will signify a radical change in operation procedures and further patient post recovery.”

    The researchers hope to eventually extend this technology to other areas where infectious biofilms pose a problem.