Method for producing an antimicrobial polymer surface and material having an antimicrobial polymer surface

Abstract

The invention relates to a method for producing an antimicrobial polymer surface, in particular an antimicrobial biopolymer surface, wherein a surface containing at least one polymer, in particular a biopolymer, is provided and the provided surface is treated exclusively with high-energy electrons in the presence of an oxygen-containing atmosphere, preferably air, and in the absence of further substances, wherein a specified electron energy is applied to the surface at a specified total dose in sequences at specified process dose rates. The invention further relates to a material having such an antimicrobial polymer surface.

Description

[0001] Method for producing an antimicrobial polymer surface and material having an antimicrobial polymer surface

[0002] The invention relates to a method for producing an antimicrobial polymer surface and to a material having an antimicrobial polymer surface, in particular for use as packaging material in medicine or on objects that come into contact with human skin, in particular disposable medical products such as dressing material or surgical suture material.

[0003] Antimicrobial surfaces are playing an increasingly important role in biotechnology research, and especially in medicine, as they help reduce contamination and the spread of pathogens in clinical settings. Advancing research and development of materials with antimicrobial properties has the potential to improve hygiene practices in laboratories, hospitals, and other medical facilities, ultimately contributing to the safety of patients and medical staff. Biopolymers are becoming increasingly popular for medical products, particularly for packaging purposes, due to their sustainable properties and efforts to reduce the use of non-renewable resources. Some commonly used biopolymers include polylactide (PLA) and PHA polyhydroxyalkanoate (PHA).The bioplastic PLA is made from plant sources, such as corn starch or sugar beets, and is biodegradable. PHAs are biopolymers produced by microorganisms. Starch-based biopolymers are also known from corn starch, potato starch, or other starchy plant materials.

[0004] One option for preventing microbial contamination or inactivating microorganisms is treatment with ionizing radiation, such as gamma radiation, accelerated electron beams, or bremsstrahlung. Sterilization using ionizing radiation is regulated by numerous international standards and is based on a complex reaction chain of biological radiation effects, encompassing physical, chemical, biochemical, and biological / medical effects. Ionizing radiation is also used in this context to modify polymers, biopolymers, and related materials. Radiation-chemical grafting is often used to produce antimicrobial polymer surfaces. This is a process in which polymers or biopolymers are modified by irradiation with high-energy radiation.The effect of radiation energy cleaves polymer chains, creating so-called radicals. These radicals can then react with a second polymer chain or a grafting additive and attach to it, creating a long-chain branching or "grafting." The key process parameters for radiation-chemical grafting are dose, process dose rate, activation temperature and atmosphere, as well as the grafting additive used, solvent, and finally, the pH value. Grafting enables the binding of antimicrobial substances to the polymer surface, thus creating an antimicrobial coating. For medical applications, for example, silver coatings are used, although this requires the use of the precious metal silver in a comparatively complex chemical process.This is associated with high costs for the mass production of packaging materials from a corresponding polymer material. Another disadvantage of radiation-chemical grafting is the solvents or grafting additives commonly used. The use of solvents can lead to environmental pollution and often requires complex treatment steps to recover or dispose of the solvents. Grafting additives are introduced into the grafting process to facilitate the reaction between the polymer chains and improve the yield of grafted polymers. For example, they can serve as initiators for the grafting reaction or as agents to control the reaction kinetics. However, some of these grafting additives can be toxic or cause undesirable side reactions, which can compromise the quality and purity of the final product.

[0005] The invention is based on the object of being able to produce antimicrobial properties of a polymer surface, especially a biopolymer surface, cost-effectively and without the known disadvantages. Furthermore, it is the object of providing a corresponding material.

[0006] The problem is solved by a method having the features according to claim 1. Variants are specified in the dependent claims. The features according to claim 9 provide a solution for a corresponding material.

[0007] The invention is based on the surprising discovery that a durable antimicrobial polymer surface can be produced solely by irradiation with high-energy electrons in an oxygen-containing environment, without the need for the presence of additional substances, such as solvents or a grafting additive. The process for producing an antimicrobial polymer surface, specifically an antimicrobial biopolymer surface, is thus characterized by the exclusive use of high-energy electrons. In the process, a surface containing at least one polymer, specifically a biopolymer, is first provided. Alternatively, a surface can be provided which consists of exactly one polymer, specifically exactly one biopolymer. It is essential that the surface is provided as a polymer surface, so that an outer layer of the surface is a polymer layer.For simplicity, the surface can be referred to as a polymer surface. The polymer surface is prepared in a conventional manner, resulting in a solid material structure on the polymer surface that can be irradiated with high-energy electrons. The prepared surface is then treated exclusively with high-energy electrons in the presence of an oxygen-containing atmosphere, preferably air, and in the absence of other substances. A predetermined electron energy with a predetermined total dose is applied to the surface in sequences at predetermined process dose rates. The process dose rate corresponds to the dose per total treatment time of the surface.

[0008] It has been shown that the antimicrobial effect is achieved solely by the targeted modification of the polymer structure of the at least one polymer on the polymer surface using high-energy electrons. It is important that no additional solvent or grafting additive is used or added separately during the application of high-energy electrons to the polymer surface. Electron beam application takes place solely in the presence of an oxygen-containing atmosphere, with the term "oxygen-containing atmosphere" describing an atmosphere with an oxygen content of at least 1% (v / v). Ambient air is sufficient as an oxygen-containing atmosphere. The process is preferably carried out in an ambient air atmosphere. Thus, separate solvents or a grafting additive are not involved in the electron beam application according to the process of the invention.By eliminating the need for additional substances, the process according to the invention advantageously enables a particularly cost-effective and environmentally friendly production of antimicrobial polymer surfaces. Eliminating the need for additional substances also allows for a simplified design of the application system, since complex handling of liquid substances, for example, is no longer required. This allows for further cost savings, which reduces the cost of the manufactured products.

[0009] Antimicrobial properties of the treated surface were observed for aerobes and anaerobes, for example Rhodococcus ruber, Micrococcus luteus and Escherichia coli, whereby in the sense of the invention the term “antimicrobial” is understood to mean a bacteriostatic or bactericidal effect.

[0010] In this process, high-energy electrons are applied to the surface in the form of an electron beam. When the electron beam is applied, charged particles are released at a cathode, accelerated, and focused into a fine beam. For electron beam treatment, the electron beam is directed onto the surface provided, where the energy of the electron beam is absorbed. For the purposes of the invention, the term "electron beam treatment" describes the application of high-energy electrons to the surface provided, where the surface provided is irradiated with the high-energy electrons. The electron energy of the high-energy electrons is preferably in the range of 0.07 keV to 10 MeV.

[0011] The process dose rate is preferably in the range of 0.5 kGy / s to 150 kGy / s.

[0012] Preferably, a total dose in the range of 25 kGy to 1000 kGy, particularly preferably in the range of 25 kGy to 500 kGy, is applied to the surface. The total dose can be applied to the surface stepwise in sequences, each with a partial dose in the range of 2.5 kGy / sequence to 50 kGy / sequence. It can therefore be provided that the total dose is applied to the surface in sequences with partial doses in the range of 2.5 kGy / sequence to 50 kGy / sequence. The process parameters total dose, partial dose per sequence, process dose rate, atmosphere, and temperature can advantageously be adapted to generate antimicrobial properties for different polymer species, because different polymer species can require different process parameters to generate the desired antimicrobial properties on the surface.

[0013] The modification of the polymer surface is also influenced by the surface temperature during electron beam application. For this reason, the surface temperature should be carefully considered during electron beam treatment, in which the high-energy electrons are applied to the surface. Therefore, the electron energy and the process dose rate of the electron beam can be adjusted such that the surface temperature during electron beam treatment is in the range of 0 °C to 80 °C, preferably in the range of 15 °C to 35 °C.

[0014] In particular, it can be provided that the electron energy and the process dose rate are adjusted in such a way that the temperature at the surface remains below the glass transition temperature of the polymer / biopolymer. The term glass transition temperature (T g) is the temperature at which a polymer or a biopolymer changes from a hard, glassy state into a rubber-elastic, flexible or leather-like to viscous state.

[0015] Preferably, a surface is provided which predominantly contains PLA, preferably consists of PLA. PLA proves to be particularly suitable for producing the desired antimicrobial properties. Furthermore, it can be provided that the at least one polymer is selected from a group consisting of polylactide (PLA), polybutylene terephthalate (PBT), polycarbonate (PC), polyester carbonate (PEC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polyacrylates (PAR), polybutylene succinate (PBS), polycaprolactone (PCL), polyhydroxybutyric acid (PHB), and polyhydroxyalkanoates (PHA).Thus, a surface can be provided which contains or consists of at least one polymer from the group of polymers consisting of polylactide (PLA), polybutylene terephthalate (PBT), polycarbonate (PC), polyester carbonate (PEC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polyacrylates (PAR), polybutylene succinate (PBS), polycaprolactone (PCL), polyhydroxybutyric acid (PHB), and polyhydroxyalkanoates (PHA). Polyesters and polymers which have carbamic acid ester groups and / or amide structures have generally proven suitable. It is also conceivable to provide a surface which contains two or more of the polymers mentioned or consists of two or more of the polymers mentioned. Accordingly, the provided surface may contain PLA, PBT, PC, PEC, PET, PEN, PTT, PAR, PBS, PCL, PHB and / or PHA or may consist of PLA, PBT, PC, PEC, PET, PEN, PTT, PAR, PBS, PCL, PHB and / or PHA.The surface can be provided on a material, which can be formed from the polymer or biopolymer. The method according to the invention thus enables the production of antimicrobial polymer surfaces, including materials with such a polymer surface.

[0016] Furthermore, it can be provided that the surface is made of a material that is not made of the polymer or biopolymer of the surface. In this case, for example, a surface made of PLA is provided on the material. Material composites made of metal and polymer, such as those used for prostheses, are conceivable.

[0017] The method according to the invention is carried out using a system for producing antimicrobial surfaces. The system comprises a device for generating high-energy electrons in the form of an electron beam and a material receiving device for attaching and providing a polymer surface. The material receiving device and the electron beam are movable relative to one another so that the electron beam can be directed onto a polymer surface of the polymer material. Systems for generating an electron beam are well known to those skilled in the art and will therefore not be explained in further technical detail.

[0018] A further aspect of the invention is a material, specifically a polymer material, with a surface comprising at least one polymer, specifically a biopolymer. The surface can alternatively also consist of the polymer, specifically the biopolymer. The material is characterized in that the surface has been irradiated with high-energy electrons in the presence of an oxygen-containing atmosphere, preferably air, without the presence of further substances, with a predetermined electron energy in the range of 0.07 keV to 10 MeV with a predetermined total dose in the range of 25 kGy to 1000 kGy, preferably in the range of 25 kGy to 500 kGy, in sequences at predetermined process dose rates in the range of 0.5 kGy / s to 150 kGy / s. Consequently, the polymer surface of the material has a modification produced using the method according to the invention.

[0019] According to a preferred embodiment of the material, the surface may have been irradiated with a total dose in sequences with partial doses in the range of 2.5 kGy / sequence to 50 kGy / sequence.

[0020] The surface of the material preferably comprises the polymer PLA, wherein the material can be in the form of a film, a fiber, or a fabric. Alternatively, the surface of the material consists of PLA, wherein the material can be in the form of a film, a fiber, or a fabric. Furthermore, it can be provided that the surface contains at least one polymer selected from a group consisting of PBT, PC, PEC, PET, PEN, PTT, PAR, PBS, PCL, PHB, PHA, or consists of at least one polymer selected from a group consisting of PBT, PC, PEC, PET, PEN, PTT, PAR, PBS, PCL, PHB, PHA. The material can have a surface which contains several of the aforementioned polymers. Different combinations of the composition of the aforementioned polymers are possible, so that the surface of the material can consist of different combinations of the aforementioned polymers.A preferred composition is one in which PLA is the main component of the polymer surface. If the material is in the form of a film, treatment with the high-energy electrons can be carried out continuously according to the method according to the invention, with the film being moved from roll to roll.

[0021] In addition to PLA, PBT, PC, PEC, PET, PEN, PTT, PAR, PBS, PCL, PHB and / or PHA, the material may also contain other components such as fillers, processing aids, stabilizers or fibers.

[0022] The material produced by this process can be used as packaging material, especially for medical products. Furthermore, the material can be used as a component of medical dressings or as surgical suture material. It could also be used as a prosthetic material. The material with the antimicrobial surface can be used wherever the spread or adhesion of bacteria or fungi is undesirable.

[0023] Further details of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. The exemplary embodiments are intended to describe the invention without limiting it. They show:

[0024] Fig. 1: a diagram of a first embodiment illustrating bacterial growth on a glass surface and on an untreated polymer surface in comparison to a sample with a polymer surface which has been treated with high-energy electrons using the method according to the invention and

[0025] Fig. 2: a diagram of a second embodiment illustrating bacterial growth on a glass surface and on an untreated polymer surface in comparison to a sample with a polymer surface which has been treated with high-energy electrons using the method according to the invention.

[0026] Figure 1 shows a diagram 1 of a first exemplary embodiment illustrating bacterial growth on a glass surface and on an untreated polymer surface in comparison to a sample with a polymer surface that had been treated with high-energy electrons according to the method according to the invention. The procedure for the first exemplary embodiment was as follows: In a first step, PLA sheets were prepared by cutting the PLA sheets into samples measuring 2 cm by 2 cm. The PLA sheets have a thickness of 4 mm. To avoid contamination after the electron treatment, the sheets were first individually packaged and welded. The cut-to-size PLA sheets were then treated on one surface with an electron energy of the high-energy electrons of 0.150 MeV with a total dose of 250 kGy in the presence of ambient air.The application of the high-energy electrons in the form of an electron beam was carried out at a surface temperature of 35 °C in sequences with single doses of 12.5 kGy with a process dose rate of 0.87 kGy / s over a period of 289 s.

[0027] Electron beam treatment was followed by contamination and subsequent incubation. For this purpose, the samples to be tested were first contaminated with a glass material as a reference sample, as well as non-irradiated PLA and PLA irradiated with 250 kGy with a bacterial suspension containing Rhodococcus ruber. Samples were contaminated with 300 colony-forming units (CFU) / μl and 3000 CFU / μl, respectively. The contaminated samples were incubated at 30 °C for 24 h. Following incubation, the bacterial colonies were detached from the sample surfaces and smeared onto a nutrient medium, followed by further incubation at 30 °C for 96 h. Finally, the colony-forming units were counted. Figure 1 shows the results, which were determined in duplicate. The bars with the reference number 2 show the CFU results of Rhodococcus ruber on the glass sample after incubation.Bars 3 show the CFU on the untreated PLA polymer surface, while bar 4 shows the CFU of the PLA polymer surface treated according to the inventive method with the above parameters. Diagram 1 of Figure 1 shows the results for 300 CFU / μl and 3000 CFU / μl after incubation. While the sample with the glass surface and the sample with the untreated PLA polymer surface show significant growth of Rhodococcus ruber, the PLA polymer surface treated with 250 kGy shows no bacterial contamination with Rhodococcus ruber.

[0028] Figure 2 shows diagram 1 of a second exemplary embodiment illustrating bacterial growth on a glass surface and on an untreated PLA polymer surface in comparison to a sample with a PLA polymer surface that was treated with high-energy electrons using the inventive method. In contrast to the first exemplary embodiment, contamination with Micrococcus luteus occurred. Figure 2 shows the results, which were determined in duplicate. Bar 2 shows the bacterial growth in CFU on the glass surface. Bar 3 shows the bacterial growth in CFU on the sample with the untreated PLA polymer surface. Bar 4 shows the CFU on the PLA polymer surface that was treated with a total dose of 200 kGy.While the samples with the glass surface (results bar 2) and the untreated polymer surface (results bar 3) show a significant contamination with Micrococcus luteus after contamination with 3000 CFU / μl and subsequent incubation, almost no contamination with Micrococcus luteus is detectable on the treated PLA polymer surface (results bar 4) after contamination with 3000 CFU / μl and subsequent incubation. List of reference symbols.

[0029] 1 diagram

[0030] 2 CFU on glass surface

[0031] 3 CFU on untreated PLA polymer surface

[0032] 4 CFU on treated PLA polymer surface

Claims

Patent claims 1. A method for producing an antimicrobial polymer surface, especially an antimicrobial biopolymer surface, wherein a surface containing at least one polymer, especially at least one biopolymer, is provided and the provided surface is treated exclusively with high-energy electrons in the presence of an oxygen-containing atmosphere, preferably air, and in the absence of further substances, wherein a predetermined electron energy with a predetermined total dose is applied to the surface in sequences at predetermined process dose rates.

2. Method according to claim 1, characterized in that the electron energy of the high-energy electrons is in the range from 0.07 keV to 10 MeV.

3. Method according to one of claims 1 or 2, characterized in that the process dose rate is in the range from 0.5 kGy / s to 150 kGy / s.

4. Method according to one of claims 1 to 3, characterized in that a total dose in the range of 25 kGy to 1000 kGy, preferably in the range of 25 kGy to 500 kGy is applied to the surface.

5. Method according to one of claims 1 to 4, characterized in that the electron energy and the process dose rate are adjusted such that the temperature at the surface during the electron beam treatment is in the range from 0 °C to 80 °C, preferably in the range from 15 °C to 35 °C.

6. Method according to one of claims 1 to 5, characterized in that the electron energy and the process dose rate are adjusted such that the temperature at the surface remains below the glass transition temperature of the polymer / biopolymer.

7. Method according to one of claims 1 to 6, characterized in that the total dose is applied to the surface in sequences with partial doses in the range of 2.5 kGy / sequence to 50 kGy / sequence.

8. The method according to any one of claims 1 to 7, characterized in that the at least one polymer is selected from a group consisting of polylactide (PLA), polybutylene terephthalate (PBT), polycarbonate (PC), polyester carbonate (PEC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polyacrylates (PAR), polybutylene succinate (PBS), polycaprolactone (PCL), polyhydroxybutyric acid (PHB) and polyhydroxyalkanoates (PHA).

9. Material, especially polymer material, with a surface comprising at least one polymer, especially a biopolymer, characterized in that the surface has been irradiated with high-energy electrons in the presence of an oxygen-containing atmosphere, preferably air, without the presence of further substances with a predetermined electron energy in the range from 0.07 keV to 10 MeV with a predetermined total dose in the range from 25 kGy to 1000 kGy, preferably in the range from 25 kGy to 500 kGy, in sequences at predetermined process dose rates in the range from 0.5 kGy / s to 150 kGy / s.

10. Material, especially polymer material, according to claim 9, characterized in that the surface has been irradiated in sequences with partial doses in the range of 2.5 kGy / sequence to 50 kGy / sequence.

11. Material, especially polymer material, according to claim 9 or 10, characterized in that the surface contains at least one polymer selected from a group consisting of PLA, PBT, PC, PEC, PET, PEN, PTT, PAR, PBS, PCL, PHB, PHA, or consists of at least one polymer selected from a group consisting of PBT, PC, PEC, PET, PEN, PTT, PAR, PBS, PCL, PHB, PHA.

12. Material, especially polymer material, according to one of claims 9 to 11, wherein the material is in the form of a film, an adhesive film, a fiber or a fabric.

13. Use of the material, especially polymer material, according to one of claims 9 to 12, as packaging material, especially as packaging material for medical products.

14. Use of the material, especially polymer material, according to one of claims 9 to 12, as a component of a medical dressing material or as a surgical suture material.

15. Use of the material, especially polymer material, according to one of claims 9 to 12, for medical devices and for holding and gripping devices in public buildings and / or means of transport.

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