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Antimicrobial FLEXible POLymers for its use in hospital environments

Periodic Reporting for period 2 - FLEXPOL (Antimicrobial FLEXible POLymers for its use in hospital environments)

Reporting period: 2018-07-01 to 2019-12-31

Facing the increasing population growth going along with higher health awareness the problem of infections due to resistant bacteria or other microorganism is gaining a new level of significance. Conventional treatments like antibiotics and other drug strategies have proved less efficient against resistant germs and other microorganisms. The center of potential infection and further spread to others are health environments like medical offices and hospitals. The project FLEXPOL takes the approach of eliminating the spread of multi resistant microorganisms and bacterial infections by providing a completely new way of surface sterilization for sanitary environments. This leads to fewer infections, less antibiotics, lower hospitalization cost, less sick-days, less fatalities as well as less usage of chemical detergents and an enhanced epidemic control.

FLEXPOL develops a pilot line for the production of a cost effective antimicrobial adhesive film for its use in hospitals. The obtained adhesive film will inhibit growth of a wide range of microbes and will be suitable for high-touch surfaces, providing a durable protection with good resistance. It will assure the highest level of hygiene and patient safety, reducing the use of disinfectants. These objectives will be achieved, using a multi-functional approach combining prevention of adhesion with killing of microorganisms, by means of essential oil emulsions embedded in a micro and nanopatterned polypropylene matrix.
In the first year of the project, importatnt key-achievements were already completed. This involves the selection and encapsulation of essential oils, as well as the creation of hierarchical microstructures on Silicon-wafers. Validation tests with four bacterial strains, yielded good antimicrobial efficiancies for the designed approach and were taken as a basis for the decision on the further product-development. For the use of the product after the duration of the project, first studies were conducted which yielded two main applications, suitable for the implementation of the FLEXPOL film in the hospital environment.

Once defined, the targeted structures and chemicals were investigated in detail and a suitable approach for the upscaling was developed during the second year of the project. On the supply-chain of the chemical side, the encapsulated essential oils were successfully introduced into the targeted PP-matrices. The amount of introduced essential oils was varied between 0.25% and 2.5% in weight, where the lowest concentration was found to yield the best release to the environment by means of diffusion through the three layered film. By blow-extrusion of the three-layered film with encapsulated materials, the final raw-material of the project could be successfully produced by the end of the second year.
In the structuring approach, it was realized to transfer the hierarchical microstructures from the wafer-level to larger scales by step-and-repeat hot embossing. The derived large-area masters were successfully produced and implemented into a roll-to-roll hot embossing system. Finally, the validation of the targeted production approach could be achieved by the end of the second project-year.
The solution provided by FLEXPOL will combine superhydrophobic hierarchical patterns with pyramidal shapes spikes obtained from black silicon and inspired by the wings of a cicada. These structures will generate a mechanical bactericidal effect, independent of chemical composition. Both kind of surfaces have been already fabricated and tested at lab by FLEXPOL partners, characterizing its hydrophobic and bactericidal behaviour respectively. The superhydrophobic surfaces will take advantage of bacteria and fungi have difficulties to adhere on them, minimizing the microorganism colonization. At the same time, the presence of high aspect ratio nanofeatures with pyramidal shapes spikes will drive the bacteria to respond to the physical interaction forces, leading to bacteria deformation and death due to bacteria’s membrane breakdown. Moreover, the
superhydrophobic polypropylene surfaces will provide a low surface energy that prevents the permeation of water into the surface. The lack of moisture will create a surface environment in which the fungi will hardly survive. Thus, the FLEXPOL film will be comprised of topographies minimizing microorganisms (bacteria and fungi) adhesion by hierarchical micro and nanotopograhies and killing those bacteria able to bind by high aspect ratio nanospikes while a superhydrophobic behaviour is created avoiding fungi survival. FLEXPOL will combine for the first time hierarchical micro and nanostructures providing both, a non-bactericidal surface in which bacteria and fungi have difficulties to bind and a bactericidal surface providing killing of those bacteria and avoiding its proliferation through the film area.

A high percentage of nosocomial infections (hospital acquired infections) are caused by bacteria and other microorganisms resistant to antibiotics, making the treatment difficult, increasing mortality and suffering of patients and also increasing the cost of the hospital budget. In fact, new antibiotic resistance mechanisms were first described in hospital-acquired micro-organisms. The latest regional data show that each year, approximately 125,000 deaths in the EU are caused by drug-resistant bacteria, and furthermore, infections related to their presence result in extra annual healthcare costs. In addition, the percentage of micro-organisms exhibiting antimicrobial resistance, especially resistance to multiple antibiotics, is continuously increasing in Europe. A significant trend of combined resistance to multiple antibiotics in both E. coli and Klebsiella pneumoniae has
been reported in more than one third of the EU/EEA countries. The FLEXPOL films will provide a complete solution combining a bactericidal behavior provided by blends of oil emulsions and nanofeatures capable of killing bacteria in a few minutes with hierarchical structures, thus minimizing the microorganisms adhesion to surfaces. The films is designed to have a 7 - 9 months lifetime controlling the leaching of oils and making it compatible with functional micro and nanotopography over this timeframe. The film will be made compatible with cleaning protocols followed in Hospitals, even though the minimum use of disinfectants is targeted. FLEXPOL is focused on long lasting antimicrobial and antifungical behaviour using natural ingredients such as oil emulsions and the own film topography to fight off microorganisms. This strategy will provide an active surface 7 days a week and 24 hours a day while it will avoid the use of zinc, silver ions and chemical released to environment in very sensible areas.
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