Polyethylene material with copper nanoparticles having antimicrobial activity

Abstract

The present invention relates to a material having antimicrobial properties comprising polyethylene with copper nanoparticles. The invention further relates to a method for preparing the polyethylene material with copper nanoparticles having antimicrobial properties. The material provided can be mainly used in the food packaging industry as it is safe for packaging products for human consumption.

Description

[0001] POLYETHYLENE MATERIAL WITH COPPER NANOPARTICLES WITH ANTIMICROBIAL ACTIVITY

[0002] Scope

[0003] The present invention falls within the field of the industry of materials for making packaging for food or products for human consumption.

[0004] BACKGROUND

[0005] According to the 2019 report "The State of Food Security and Nutrition in the World" by the Food and Agriculture Organization of the United Nations, food security refers to sufficient access to food, both in terms of quality and quantity. Conversely, food insecurity can have significant health consequences, associated with malnutrition, causing both undernutrition and obesity, as well as developmental and growth problems. In this context, the poorest communities face physical and economic barriers to accessing nutritious and healthy food. To improve access, governments can design strategies for obtaining nutritious food through their public policies. One alternative, stemming from technological development, is food preservation.Currently, it is estimated that around 870 million people worldwide suffer from hunger, while 1.3 billion tons of food are lost through waste in stores, homes, and food services, primarily during handling and storage. Latin America and the Caribbean, in particular, contribute 6% of food loss, adding to the global cost, estimated at US$750 billion, excluding fish and seafood.

[0006] Furthermore, microbes, such as viruses, bacteria, and parasites, can enter the body through contaminated water or food, causing infectious or toxic illnesses. These pathogens are among the most serious threats to food safety worldwide. The World Health Organization (WHO) estimated that around 600 million people suffered from foodborne illnesses in 2015, and the number of reported deaths annually worldwide is 4.2 million.

[0007] Furthermore, due to insufficient processing, certain food products obtained from fresh crops, primarily fruits, are susceptible to these pathogens, posing a threat to food safety. The growth and survival rates of microorganisms and pathogens transmitted through the spoilage of packaged foods are determined by internal and external factors, as well as by packaging conditions. Microorganisms that affect food preservation pose a threat to a wide range of foods, including baked goods, meat, cheese, and poultry products. This spoilage is caused by microbial and fungal contamination, as well as the oxidation of lipids and proteins, affecting food quality and safety, particularly within the packaging, and can occur even when conventional preservation techniques are used.

[0008] Packaging has a profound influence on nutritional value due to the interaction between the packaging material and the food itself. Packaging for preservation is essential to extending food shelf life. It also plays a crucial role during the transport and distribution of food to consumers. Consumers' affinity for hygiene and food safety has increased significantly, leading to strong new preferences for innovative and intelligent packaging materials. Considering these factors, it is extremely important to advance the development of new packaging technologies to improve the quality, safety, freshness, and, above all, the antimicrobial properties of food, with the aim of significantly reducing foodborne illnesses and contributing to a better quality of life.In this context, the need arises to implement new strategies based on nanotechnology in the food sector, to provide improvements in the properties (mechanical resistance, diffusivity, optical properties and solubility) of materials, formulated through nanotechniques, which has led to their use in all stages of the food chain, including processing, production, packaging and transport.

[0009] The estimated role of nanotechnology in improving the shelf life of agri-food products is to address over 40% of estimated food losses worldwide. While several techniques exist to extend the shelf life of agri-food products, such as modifying atmospheric gas composition, heat treatments, combined gas atmosphere treatments, and cold storage, these treatments are less efficient and more expensive to operate. Therefore, nanoparticles (NPs), particularly metallic nanoparticles (MNPs), have become a valuable class of nanostructures due to their key role in preserving, protecting, and extending the stability of food packaging.

[0010] Furthermore, copper-based NPCu exhibits strong antibacterial activity against a wide variety of microorganisms. Since 2008, the U.S. Environmental Protection Agency (EPA) has certified copper's antimicrobial properties, demonstrating 99.9% inhibition of bacterial growth. Copper surfaces can kill 99.9% of pathogenic bacteria within two hours of contact. This antimicrobial activity increases at a rate of 7 to 8 logs per hour, and no microorganisms survive longer incubation periods.

[0011] State of the Art

[0012] In the state of the art, it is possible to find various publications related to the use of nanoparticles, polyethylene, or their application in food packaging.

[0013] The following are some publications related to the field of the present invention.

[0014] In the patent document in Chile N 9 Patent 68,809, belonging to one of the inventors of the present invention, pertains to a silicone material with copper nanoparticles possessing antibiofilm properties, designed for the manufacture of medical devices, particularly urinary catheters, to prevent catheter-associated urinary tract infections (CAUTIs). The material itself does not directly disclose the use of polyethylene for food packaging; furthermore, the molecular weight of PEG is higher than that used in the present invention, and the packaging materials are not similar because the processes related to both technologies are not comparable.

[0015] The document by Kshirod Kumar Dash et al. (Polymers, 2022 Feb; 14(3): 521, pp. 1-17) summarizes several studies that evaluated the potential of various matrices, such as polyethylene, agar, gelatin, chitosan, and cellulose, as food packaging materials, using different nanoparticles, including, for example, Ag, ZnO, TiO2, CuO, and Au. However, regarding the use of polyethylene as a polymer matrix, only studies with silver, ZnO, or TiO2 nanoparticles are discussed; there is no mention of the use of polyethylene functionalized with copper nanoparticles (CuNPs). Section 3.3 of this document mentions that copper oxide nanoparticles (CuO-NPs) are the most commonly used metal oxides in food packaging, without specifying the polymer matrix employed. In general, no material like the one used in the present invention, based on polyethylene functionalized with copper nanoparticles, is mentioned.

[0016] Furthermore, in the publication by Yukun Huang et al. (Nanomaterials. 2018; 8(10): 830. 2018), the properties of nanomaterials and their potential applications for ensuring food quality are discussed, along with the toxicological and safety issues associated with nanomaterials in contact with food. This scientific document also mentions copper nanoparticles, their synthesis, and their physical, chemical, and biological properties, although it focuses primarily on CuO nanoparticles, with little mention of copper nanoparticles (NPCu). This document does not mention polyethylene matrices with copper nanoparticles, nor the use of polyethylene glycol and / or H₂O₂ in the preparation of surfaces functionalized with metallic nanoparticles.

[0017] Finally, in the publication by Camila Arcos et al. (Polymers 2022, 14, 5220, pp. 1–13), the effect of adding copper particles and the recycling process on extruded high-density polyethylene (HDPE) was studied. Copper nanoparticles were added to the polymer matrix using a single-screw extruder at high temperatures between 190 and 220°C and 30 rpm, allowing the incorporation of copper particles of nanometric and micrometric sizes. The incorporated copper nanocubes (CuNCs) have an average size of 300 nm. The work described in this document does not involve oxidative degradation of polyethylene and focuses on producing functionalized high-density polyethylene; therefore, it does not consider products such as food packaging bags.

[0018] As can be seen, there are developments of materials with antimicrobial activity, although there is a niche for developments with additional advantages in terms of providing an effective and efficient material in terms of its components and method of manufacture, while also being safe for use in food packaging for human consumption.

[0019] BRIEF DESCRIPTION OF THE FIGURES

[0020] Figure 1. a) FTIR spectra of recycled polyethylene material subjected to treatment with 30% H2O2 at different modification times and b) schematic representation of the oxidative degradation of recycled polyethylene against H2O2.

[0021] Figure 2. SEM Morphography of the polyethylene material functionalized with NPCu and Schematic representation of the functionalization of the polyethylene material with NPCu.

[0022] Figure 3. Step-by-step scheme of the polyethylene modification process with NPCu including intermediates.

[0023] Figure 4. Growth of S. aureus represented in a graph of optical density (OD) vs. time. Standard S. aureus growth condition (without the addition of any plastic) in blue, condition with functionalized plastic in orange, and condition with non-functionalized plastic in gray. Measurements from the Tecan M200 plotted directly.

[0024] Figure 5. Comparison of the bacterial load of S. aureus and E. cali after 24 hours of exposure to the modified bags. No colonies are observed under the modified condition. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention provides an antimicrobial material made from copper nanoparticles and polyethylene, in which specific copper nanoparticles are generated for material modification. The material modification process (activation and functionalization) is also provided.

[0026] The material according to the present invention is made from surface-modified polyethylene with stabilized copper nanoparticles, embedded and anchored with polyethylene glycol (PEG).

[0027] Material according to the invention

[0028] The present invention provides a polyethylene-based material with antimicrobial activity comprising:

[0029] a) polyethylene with its surface degraded into its oxidized species and chemically activated; b) polyethylene glycol (PEG) of 500 to 3,000 g / mol anchored to the surface of the polyethylene, c) copper nanoparticles of size in a range of 200 to 500 nm, stabilized, embedded and anchored in the polyethylene.

[0030] In a preferred embodiment of the invention, the molecular weight of PEG is between 1,000 and 2,000 g / mol.

[0031] The copper nanoparticles are at a concentration of 0.5 and 22 pM.

[0032] The antimicrobial material according to the invention is used in the manufacture of packaging for the food industry or any product for human consumption.

[0033] Method of preparing the material according to the invention

[0034] The invention further provides a method for preparing the polyethylene-based material with antimicrobial activity comprising the steps of:

[0035] a) Activate the surface of a polyethylene support material by means of a hydrothermal treatment at a temperature between 150 and 200 gC in the presence of EbC solutions at concentrations between 0.5 to 30% by weight (thermo-oxidative treatment); and b) Functionalizing the polyethylene surface activated with polyethylene glycol (PEG) of 1,000 to 3,000 g / mol and copper nanoparticles (CuNPs) of size in a range of 200 to 500 nm, wherein the activated polyethylene surface is coated with an aqueous solution of copper nanoparticles (CuNPs) stabilized with polyethylene glycol (PEG) of 1,000 to 3,000 g / mol, wherein the stabilized copper nanoparticles, embedded and anchored with polyethylene glycol, are anchored to the polyethylene surface.

[0036] In a preferred embodiment of the invention, the treatment with E Chse is carried out at a temperature of 180 °C.

[0037] In another preferred embodiment of the invention, the concentration of H2O2 is between 0.5 and 3%. In a preferred embodiment of the invention, the molecular weight of PEG is between 1,000 and 2,000 g / mol.

[0038] In one embodiment of the invention, the activation of the polyethylene surface is carried out for a period of between 8 and 15 h and the functionalization of the activated polyethylene surface is carried out for a period of between 5 and 15 h.

[0039] In a preferred embodiment of the invention, after the functionalization of the activated polyethylene surface is completed, the material is dried and washed, where the drying is done with compressed air and the washing is done with distilled water.

[0040] The PEG-anchored copper nanoparticles used in the functionalization were made from copper sulfate (CuSO4*5H2O) mixed with PEG of 1,000-3,000 g / mol as a stabilizing agent, in a basic medium.

[0041] A series of solutions was prepared by mixing 0.01 M copper(II) sulfate with PEG at various concentrations. A 0.5 M PEG stock solution was prepared and then diluted to 0.25 M, 0.125 M, 0.063 M, and 0.031 M solutions, which were then added to the copper(II) solution. In separate containers, 0.005 M ascorbic acid and 0.15 M NaOH solutions were prepared. The ascorbic acid and hydroxide solutions were added to the copper(II) solution in three different ways (A, B, and C, respectively) using sonication. For procedure A, ascorbic acid was added to the solution first, and NaOH was added 1 minute later. The entire solution was sonicated for another 5 minutes and then allowed to stand for 30 minutes to allow the reaction to complete.In procedure B, ascorbic acid and sodium hydroxide were mixed before being added to the copper(II) solution, and all other conditions remained the same as in procedure A. For procedure C, NaOH was added 1 minute before adding ascorbic acid to the copper(II) solution, and all other conditions remained the same as in procedure A. All reactions were carried out at room temperature.

[0042] After sonication, the solutions are centrifuged at 5,000 to 10,000 rpm for 20 to 60 minutes, and the precipitates are collected and redispersed in water. The resulting CuNPs are centrifuged, ideally twice, to remove excess PEG and redispersed in water for sonication to obtain a PEG precipitate with immobilized CuNPs. It is very important to highlight that ultrasonic irradiation has the advantage of introducing a variety of physical and chemical effects derived from acoustic cavitation.

[0043] After the production process is completed, the material according to the invention is characterized physicochemically, mechanically and microbiologically to verify that it meets the expected properties.

[0044] Advantages

[0045] The material according to the present invention allows the production of a food preservation packaging that increases the shelf life of food because the material enhances the antibacterial properties of copper and the non-stick capacity of PEG, being able to reduce the adhesion and proliferation of bacteria, through a spherical repulsion exclusion mechanism.

[0046] The material according to the invention incorporates antimicrobial agents corresponding to NPCu into the polyethylene polymer matrix.

[0047] The material according to the invention is sustainable and antimicrobial, focused on the food industry.

[0048] The antimicrobial packaging of the present invention incorporates copper nanostructures (NPCu) and corresponds to a viable and intelligent active packaging innovation.

[0049] Active packaging is one of the innovative food packaging concepts introduced in response to the ever-changing demands of today's consumers and market trends. It has been defined as "a type of packaging that changes the condition of the packaging to extend shelf life or improve safety or sensory properties while maintaining food quality" (L. Vermeiren et al., 1999, doi:org / 10.1016 / S0924-2244(99)00032-1). These requirements are met by incorporating inorganic nanoparticles, specifically copper, into a polymer matrix. The application of nanotechnology to packaging films has led to the term nanocomposite.

[0050] The methodology according to the invention allows for the modification of recycled synthetic polymers with antimicrobial agents to provide food packaging with enhanced barrier properties. The methodology is based on the use of recycled polymers, an environmentally beneficial route, by reusing existing polymers and converting them into active packaging. The polymer modification methodology demonstrates an environmentally friendly approach due to the use of H₂O₂ as an activator, as it is an ideal oxidant that avoids waste products in the thermo-oxidative degradation reaction of polyethylene.

[0051] The material according to the invention offers a technological innovation for food preservation, providing solutions at different stages of the agri-food chains, allowing for the reduction of food loss and strengthening food security, contributing strategies to address food poverty and malnutrition through sustainable and intelligent packaging developments.

[0052] Uses

[0053] One of the applications of the invention corresponds to packaging for the preservation of food, such as fruits and vegetables, as well as the manufacture of bags for all kinds of products where preservation is relevant.

[0054] The end users of the technology are companies that produce packaging products, food production companies, among others.

[0055] EXAMPLES

[0056] Example 1: Preparation of the antimicrobial material according to the invention.

[0057] NPCu Synthesis:

[0058] The NPCu were obtained by means of a chemical synthesis, using copper sulfate (CuSO4*5H2O) as a precursor, ascorbic acid (AA - 0.01 M) as a reducing agent and PEG of different sizes (1000-2000 g / mol) as a stabilizing agent, in a basic medium.

[0059] A series of solutions was prepared by mixing 4.0 mL of 0.01 M copper(II) sulfate with 16.0 mL of PEG at various concentrations. A 0.5 M PEG stock solution was prepared, and then dilute solutions of 0.25 M, 0.125 M, 0.063 M, and 0.031 M were prepared. These dilute solutions were added to the copper(II) solution. In separate containers, solutions of 0.005 M ascorbic acid and 0.15 M NaOH were prepared. The ascorbic acid and sodium hydroxide solutions were then mixed and added to the copper(II) solution under stirring. The entire solution was stirred for an additional 30 minutes.

[0060] After shaking, the solutions were centrifuged at 6000 rpm for 30 minutes. The precipitates were collected and redispersed in water. The resulting CuNPs were centrifuged at the same speed for another 15 minutes, twice, to remove excess PEG (2). Finally, they were redispersed in 5 mL of water and sonicated for 10 minutes.

[0061] Surface activation:

[0062] A hydrothermal treatment of polyethylene (recycled bag) was carried out in solutions of E Ch at different concentrations (0.0; 0.5; 3.0; 30% by weight) and at a temperature of 180 g C for 8 to 15 hours, more preferably for 12 hours.

[0063] Functionalization of the polyethylene surface:

[0064] The previously activated polyethylene surface was functionalized and anchored with synthesized CuNPs for 12 h. A chemical interaction was obtained between the CuNPs and the surface. This interaction occurs through the OH groups of the active polyethylene surface (see Figure 2), which subsequently react with the terminal alcohol group of the PEG, generating a PEG film via a COC ether linkage on the polyethylene surface. Finally, the material is dried with compressed air and washed with distilled water.

[0065] Example 2: Characterization of Surface Activation.

[0066] The characterization of this study was performed using Fourier Transform Infrared (FTIR) spectroscopy, a technique used to identify the functional groups present and investigate interactions and changes in the chemical composition of the samples. Hydrogen peroxide (H₂O₂) was selected as an environmentally benign oxidant. A typical advantage of H₂O₂ is that it transforms into water without any toxic residue after releasing oxygen. Figure 1 shows the FTIR spectrum of the polyethylene material after exposure to 30% H₂O₂ for extended periods (8 and 14 h) at room temperature. Oxidative degradation of the polyethylene was observed, verified by the presence of a peak at 3300 cm⁻¹ in the spectrum, indicating the presence of OH⁻ groups on the material's surface.

[0067] Therefore, through the FTIR study of the polyethylene samples (recycled bag) treated with HjOzse, it was possible to verify the oxidative activation of the surface.

[0068] Example 3: Characterization of the Synthesis of NPCu and functionalization of the polyethylene surface.

[0069] A. Synthesis of NPCu:

[0070] The dispersion of copper nanoparticles (CuNPs) was characterized by scanning electron microscopy (SEM). Figure 2 shows the 300 ± 89.11 nm particle size distribution of CuNPs on the polyethylene surface, exhibiting good distribution and no agglomeration. Particle size is a crucial factor to consider, as it influences the potential antimicrobial mechanism of action of the functionalized material. The size of the copper nanoparticles (CuNPs) affects the antibacterial effect through the interaction between the copper particles and microorganisms. This antimicrobial effect occurs primarily through contact between the CuNPs and microorganisms, especially under humid conditions. Under these circumstances, the release of copper ions into the environment is minimal, rendering the material non-toxic. B. Functionalization of the polyethylene surface with CuNPs.

[0071] The functionalization of the polyethylene surface was achieved using the NPCu dispersion synthesized in the previous step. Figure 2 shows the SEM micrograph of the polyethylene surface functionalized with the NPCu. Successful incorporation and modification of the polyethylene surface is observed, with good distribution and no agglomeration of the NPCu on the surface.

[0072] In this context, it was concluded that it was possible to operate the polyethylene surface with NPCu detailed in Figure 3.

[0073] Example 4: Analysis of the antimicrobial activity of the material of the invention.

[0074] 4.1. Growth curve (OD / hr) in contact with the plastic material

[0075] Methods: Bacterial growth kinetics were performed over 24 hours using a Tecan M200 96-well microplate reader, which measures the optical density (OD) of the bacterial culture at 600 nm every hour. E. coli and S. aureus inocula were prepared in flasks and LB medium (50%) previously sterilized under a sterile hood and incubated overnight at 190 rpm and 37°C. Each well was loaded with the volume of bacterial inoculum grown, so that 200 lp of culture would begin growth at OD 0.1 (log phase, beginning of the exponential phase) in each well. Six replicates were set up for all treatments, and two independent trials were performed. The plastics used were cut into 7x7mm squares, which were subsequently sterilized under 15 min of UV light and added individually to each well of the microplate under a hood with sterile forceps.

[0076] The conditions evaluated are:

[0077] a) Whites

[0078] • LB: indicates the sterility of the medium (LB 50%)

[0079] • LB + Pe: indicates the interaction of the control plastic at 600 nm

[0080] • LB + Pf: indicates the interaction of the functionalized plastic at 600 nm

[0081] b) S. aureus growth curve

[0082] • LB + S. aureus: standard growth of S. aureus in the culture medium

[0083] • LB + Pc + S. aureus: growth of S. aureus in contact with the control plastic

[0084] • LB + Pf + S. aureus: growth of S. aureus in contact with functionalized plastic Results

[0085] Figure 4 shows that from hour 8 onwards there is a significant difference between the standard growth treatment on the plastic alone versus the treatment in contact with the functionalized plastic (t-test p<0.05). Therefore, the study of bacterial growth kinetics allows us to qualitatively conclude that the polyethylene material functionalized with NPCu exhibits antimicrobial activity, thus providing proof of concept for the new material.

[0086] Example 5. Certification to ISO 22196:2011 against Staphylococcus aureus and Escherichia coli bacteria.

[0087] Description and identification of the samples: Recycled plastic bags surface modified with copper nanoparticles. Procedure: evaluate antimicrobial activity against protocols stipulated in the ISO 22196:2011 standard.

[0088] Specimen preparation:

[0089] Square segments of 50*50mm plastic bags were cut and sterilized by exposure to ultraviolet light for 30 minutes per side.

[0090] Inoculum preparation:

[0091] The bacteria Escherichia californica and Staphylococcus aureus, which were grown for 18 hours, were transferred to 50 ml of nutrient broth diluted 1 / 500, achieving a bacterial concentration between 2.5 x 10 5 cells / ml and 10 x 10 5 cells / ml.

[0092] Inoculation

[0093] Each specimen was individually placed in a sterile Petri dish, ensuring the surface was as flat as possible. 0.4 mL of inoculum was applied to each specimen and covered with sterile plastic film. This step ensured the formation of a homogeneous inoculum layer between the specimen and the plastic film. Finally, the dish was sealed and incubated under controlled conditions.

[0094] Incubation of the inoculated specimens.

[0095] The plates containing the inoculated samples were incubated for 24 hours at 35°C and a relative humidity not less than 90% for 24 hours.

[0096] Recovery of bacteria from test samples.

[0097] After incubation, the specimens were washed with 10 mL of SCDLP broth, ensuring thorough homogenization. They were then plated onto count agar to quantify the colony-forming units per milliliter (CFU / mL). To determine the initial bacterial concentration (T0), this process was performed immediately after inoculation.

[0098] Determination of viable bacterial count

[0099] 0.1 mL of each serial 10-fold dilution of the SCDLP broth recovered from the test sample was placed on Petri dishes containing nutrient agar. The plates were incubated at 35°C for 48 hours. After incubation, the colony count was determined. The following formula was used to determine the antimicrobial activity on the tested specimens:

[0100] N = (100 x C x D x V) / A

[0101] Where:

[0102] N is the number of viable bacteria recovered per cm 2 per test specimen;

[0103] C is the average colony count on duplicate plates;

[0104] D is the dilution factor for counted plaques;

[0105] V is the volume, in ml, of SCDLP added to the specimen;

[0106] A is the surface area, in mm² 2 , from the cover film.

[0107] Determination of antimicrobial activity

[0108] To determine antimicrobial activity, the following formula was used:

[0109] R = (Ut - Uo) - (At - Uo) = Ut- A t

[0110] Where:

[0111] R is the antibacterial activity;

[0112] Uo is the average of the common logarithm of the number of viable bacteria, in cells / cm 2 , recovered from untreated test specimens immediately after inoculation; U t It is the average of the common logarithm of the number of viable bacteria, in cells / cm 2 , recovered from the untreated test specimens after 24 hours;

[0113] TO t It is the average of the common logarithm of the number of viable bacteria, in cells / cm 2 , recovered from the treated test specimens after 24 hours.

[0114] Results

[0115] The antimicrobial activity of surface-modified bags coated with copper nanoparticles was evaluated. The results showed that the modified material reduced the bacterial load by 99.94% for both S. aureus and E. calici. Additionally, the antimicrobial activity was determined, with values ​​of 3.21 for S. aureus (Table 1) and 3.18 for E. calici (Table 2). Figure 5 shows representative images of the plates analyzed for colony counting. Table 1. Antimicrobial activity assay of polyethylene with copper nanoparticles against Staphylococcus aureus

[0116]

[0117] Table 2. Antimicrobial activity assay of polyethylene with copper nanoparticles against Escherichia cali.

[0118]

[0119] According to the analyses performed, the bags modified with copper nanoparticles exhibit antimicrobial activity against both Staphylococcus aureus and Escherichia coli, with an R value equal to or greater than 2. This indicates that the materials can be certified under the ISO 22196:2011 standard.

Claims

CLAIMS 1. A polyethylene-based material with antimicrobial activity CHARACTERIZED in that it comprises: a) polyethylene with its surface degraded into its oxidized species and chemically activated; b) polyethylene glycol (PEG) of 500 to 3,000 g / mol anchored to the surface of the polyethylene, c) copper nanoparticles of size in a range of 200 to 500 nm, stabilized, embedded and anchored in the polyethylene.

2. The material according to claim 1, CHARACTERIZED in that the molecular weight of the PEG is between 1,000 and 2,000 g / mol.

3. The material according to claim 1, CHARACTERIZED in that the copper nanoparticles are at a concentration of 0.5 and 22 pM.

4. Use of the antimicrobial material according to any of claims 1 to 3, CHARACTERIZED in that it is used in the manufacture of packaging for the food industry or any product for human consumption.

5. A method for preparing a polyethylene-based material with antimicrobial activity according to claim 1, CHARACTERIZED in that it comprises the steps of: a) Activate the surface of a polyethylene support material by means of a hydrothermal treatment at a temperature between 150 and 200 g C in the presence of E Ojen solutions at concentrations between 0.5 and 30% by weight (thermo-oxidative treatment); and b) Functionalizing the polyethylene surface activated with polyethylene glycol (PEG) of 1,000 to 3,000 g / mol and copper nanoparticles (NPCu) of size in a range of 200 to 500 nm, wherein the activated polyethylene surface is coated with an aqueous solution of copper nanoparticles (NPCu) stabilized with polyethylene glycol (PEG) of 1,000 to 3,000 g / mol, wherein the stabilized copper nanoparticles, embedded and anchored with polyethylene glycol, are anchored to the polyethylene surface.

6. The method according to claim 5, CHARACTERIZED in that the activation of the polyethylene surface in step a) is carried out by treatment with H2O2 at a temperature of 180 °C.

7. The method according to claim 5, CHARACTERIZED in that in step a) the concentration of H2O2 is between 0.5 and 3%.

8. The method according to claim 5, CHARACTERIZED in that in step b) the molecular weight of the PEG is between 1,000 and 2,000 g / mol.

9. The method according to claim 5, CHARACTERIZED in that the activation of the polyethylene surface is carried out for a period of between 8 and 15 h.

10. The method according to claim 5, CHARACTERIZED in that the functionalization of the activated polyethylene surface is carried out for a period of between 5 and 15 h.

11. The method according to claim 5, CHARACTERIZED in that the PEG-anchored copper nanoparticles used in the functionalization are made from copper sulfate (CUSO4*5H2O) mixed with PEG of 1,000-3,000 g / mol as a stabilizing agent, in a basic medium, kept under stirring for 10 to 60 minutes, followed by centrifugation at 5,000 to 10,000 rpm for 20 to 60 minutes, to obtain a PEG precipitate with immobilized CuNPs.

12. The method according to claim 11, CHARACTERIZED in that the precipitate obtained is further dispersed in distilled water and centrifuged at 2,000 to 10,000 rpm for 5 to 30 minutes to remove excess PEG, the newly collected precipitate is dispersed in distilled water and subjected to sonication, obtaining PEG-stabilized copper nanoparticles.

13. The method according to any of claims 5 to 12, CHARACTERIZED in that after completion of the functionalization of the activated polyethylene surface, the material is dried and washed.

14. The method according to claim 13, CHARACTERIZED in that the drying is done with compressed air and the washing is done with distilled water.

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