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Light and nanotechnology prevent bacterial infections in medical implants

Invented about 50 years ago, surgical nets have become key elements for restoring damaged tissue surgery, with hernia repair being the most common. When implanted in a patient's tissue, its flexible and flexible design helps keep the muscles tense and allows patients to recover more quickly than conventional surgery.

However, the implant of this type of mesh in the patient's body carries the risk of bacterial contamination during surgery and subsequent formation of infectious biofilm on the surface of the surgical net. These biofilms tend to act as a plastic coating that prevents any type of antibiotic agent from reaching and attacking the bacteria formed in the biofilm to stop the infection.

Antibiotic therapy, which is limited in time, could fail against these resistant bacteria, and the patient might end up in recurring or endless operations that could even lead to death. According to the European Antimicrobial Surveillance Network (EARS-Net), more than 30,000 deaths in Europe in 2015 were associated with antibiotic-resistant bacterial infections.

Several methods have been sought in the past to prevent implant contamination during surgery. Although post-operative aseptic protocols have been implemented to combat these antibiotic-resistant bacteria, none have been able to solve this problem completely.

Now, in a recent study published in Nano Letters and featured in Nature Photonics, researchers ICFO Ignacio de Miguel and Arantxa Albornoz, led by ICREA Romain Quidant, in collaboration with researchers Irene Prieto, Vanesa Sanz, Christine Weis and Pau Turon of Medical Devices and Pharmaceutical Companies B. Braun invented a new technique that uses nanotechnology and photonics to drastically improve the performance of medical networks in surgical implants.

With continued collaboration since 2012, the group has developed a medical network with a specific feature: the net surface is chemically modified to anchor millions of gold nanoparticles. Why? Because gold nanoparticles have been shown to be very effective in converting light into heat in very localized areas.

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These are surgical nets. The ones in the copper color on the left are covered with gold nanoparticles and the white ones on the right are the originals before the nanoparticle treatment. (Photo: ICFO)

The technique of using gold nanoparticles in light and heat conversion processes has already been demonstrated in previous studies in cancer treatment. Specifically, ICFO has been implemented in several previous studies supported by the Cellex Foundation, another excellent example of how visionary philanthropic support that focuses on solving basic problems can lead to important practical applications.

In this particular case, since more than 20 million hernia repair operations are carried out every year, it was believed that this method could reduce the cost of medical care in repeated operations, while eliminating the costly and inefficient antibiotic treatment that is in place. currently used to combat this problem.

Therefore, in an in vitro experiment and an exhaustive process, the team covered millions of gold nanoparticles and distributed them evenly throughout the structure. They tested the eyes to ensure long-term stability of the particles, non-degradation of the material and release or release of nanoparticles in the environment (flask). They observed a homogeneous distribution of nanoparticles on the structure using a scanning electron microscope (SEM).

As soon as the treated mesh was prepared, the team exposed it to S. aureus bacteria for 24 hours until biofilm formation on the surface was observed. Subsequently, they exposed the net to short, intense pulses close to infrared light (800 nm) for 30 seconds to ensure thermal equilibrium was achieved and the procedure was repeated 20 times with a four second rest interval between each pulse.

They discovered the following: they first saw that they illuminate the network with a specific frequency-induced surface plasmon resonance located in the nanoparticles, resulting in the efficient conversion of light into heat, thereby burning the bacteria on the surface. Secondly, using a confocal fluorescence microscope, they saw how many bacteria had died and how many were still alive.

Regarding the surviving bacteria, they found that biofilm cells became plankton cells, restoring their sensitivity to antibiotic treatment and immune system response. As far as dead bacteria are concerned, they have found that by increasing the amount of light that strikes the surface of the mesh, the bacteria lose their grip and detach from the surface.

Thirdly, they confirmed that near infrared light operation was perfectly compatible with in vivo conditions, so it is likely that this technique did not harm the surrounding healthy tissue. Finally, they repeated the processing and confirmed that repeated heating of the network did not affect its conversion from light to heat.

As Quidant notes, "the results of this study paved the way for the use of plasmon nanotechnology to prevent the formation of bacterial biofilms on the surface of surgical implants." There are a few more issues that need to be addressed, but it is important to emphasize that this technique will mean a radical change in surgery and subsequent patient recovery.

Pau Turon, Head of Research and Development at B. Braun, explains: "Our commitment to health professionals to help them avoid hospital infections leads us to develop new strategies for combating bacteria and biofilms. In addition, the research team is exploring the possibility of extending this technology to other sectors in which biofilms should be avoided. (Source: ICFO)

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