JP2020110955A - Antibacterial member - Google Patents

Abstract

To provide an antibacterial member achieving high antibacterial performance without an antibacterial coating.SOLUTION: An antibacterial member (10) has a substrate (11), a plurality of first protrusions (12) arranged so that one bottom surface thereof contacts the surface of the substrate (11), and a plurality of second protrusions (14) arranged on the other bottom surface (13) of the first protrusion (12). The first protrusion (12) has a diameter of 0.5 μm or more and 20 μm or less. The second protrusion (14) has a diameter of 1 nm or more and less than 500 nm. The first protrusion (12) and the second protrusion (14) have each a Young's modulus of more than 0.004 GPa and 5 GPa or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to an antibacterial member.

In recent years, nosocomial infections at medical sites and epidemics of infectious diseases in towns have become a problem. In addition, as the quality of life is improved, people's awareness of hygiene is increasing, and antibacterial needs for foods and home appliances are increasing.

The antibacterial members that have been proposed so far include components (antibacterial active components) such as antibacterial metallic elements (copper (Cu) and silver (Ag)) and ceramics (TiO ₂ ) on the surface of the base material. An antibacterial property is imparted by forming a film containing the same (hereinafter referred to as "antibacterial film"). For example, in Patent Document 1, stainless steel is used as a base, a Zn plating layer or a Zn alloy plating layer is formed thereon, and a thermosetting coating containing an antibacterial/antifungal agent is further applied, which is excellent in durability. Antibacterial and antifungal coated steel sheets are disclosed. As the antibacterial and antifungal agents, inorganic agents such as Ag, Cu and Zn, compound agents such as zinc phosphate and zinc oxide, and organic agents such as thiazole and imidazole are disclosed. It is disclosed that it is one kind or two or more kinds selected from drugs.

JP-A-8-156175

In the method of providing the antibacterial film described above, the antibacterial active ingredient is exposed to the surface of the base material in only a few percent at most, and the antibacterial performance may not be sufficient. The amount of the antibacterial active ingredient dispersed on the surface of the member can be increased in order to achieve sufficient performance, but the amount of the antibacterial component is limited due to the stability and strength of the antibacterial film. In the case of Ag, there is also a problem that the price is high, and if the amount of dispersion is excessively increased, the cost will increase. Further, when there is only one kind of antibacterial active ingredient, there is a high possibility that resistant bacteria will be produced and new bacteria may be produced.

In view of the above circumstances, an object of the present invention is to provide an antibacterial member that realizes high antibacterial properties without providing an antibacterial film.

One embodiment of the present invention for solving the above problems is to provide a base material, a plurality of first projections provided so that one bottom surface is in contact with the surface of the base material, and the other bottom surface of the first projection. A plurality of second protrusions provided, the diameter of the first protrusion is 0.5 μm or more and 20 μm or less, the diameter of the second protrusion is 1 nm or more and less than 500 nm, and The Young's modulus of the protrusion 2 is more than 0.004 GPa and 5 GPa or less, which is an antibacterial member.

More specific configurations of the present invention are described in the claims.

According to the present invention, it is possible to provide an antibacterial member that realizes high antibacterial properties and bactericidal properties without providing an antibacterial film.

Problems, configurations and effects other than those described above will be clarified by the following description of the embodiments.

The perspective view which shows typically an example of the antibacterial member of this invention. Flow chart explaining the mechanism of biofilm formation on the surface of the substrate The top view which shows the 1st example of arrangement|sequence of the 1st protrusion of the antibacterial member of this invention. The top view which shows the 2nd example of arrangement|sequence of the 1st protrusion of the antibacterial member of this invention. The top view which shows the 1st example of arrangement|sequence of the 2nd protrusion of the antibacterial member of this invention. The top view which shows the 2nd example of arrangement|sequence of the 2nd protrusion of the antibacterial member of this invention. Sectional drawing which shows the 1st example of the shape of the base material of the antibacterial member of this invention. The perspective view which shows the 2nd example of the shape of the base material of the antibacterial member of this invention. SEM observation photograph of the surface of the antibacterial member of Example 1 SEM observation photograph of the surface of the antibacterial member of Comparative Example 1 SEM observation photograph of the surface of the antibacterial member of Comparative Example 2 after water resistance evaluation

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In each drawing, common or similar components are designated by the same reference numerals, and redundant description thereof will be appropriately omitted.

FIG. 1 is a perspective view schematically showing an example of the antibacterial member of the present invention. As shown in FIG. 1, the antibacterial member 10 includes a base material 11, a plurality of first projections 12 provided so that the surface of the base material 11 and one bottom surface thereof are in contact with each other, and the other of the first projections 12 is provided. It has a plurality of second protrusions 14 provided on the bottom surface (top surface) 13. Such an aggregate of the first protrusions 12 and an aggregate of the second protrusions 14 are also referred to as a “pillar structure”. The first protrusion 12 and the second protrusion 14 form a fine uneven structure on the surface of the base material 11. In the present invention, the term "fungus" is a general term for all kinds of microorganisms such as bacteria, yeasts and molds.

As described above, conventionally, an antibacterial film is provided on the surface of the member to chemically kill the bacteria. The first protrusion 12 in the present invention has an effect of suppressing the growth of a biofilm (a three-dimensional structure composed of a fungus or an extracellular polysaccharide secreted by the fungus) due to the surface structure of the base material. The bacterium itself does not adversely affect the human body when it is used alone, and the biofilm often adversely affects the human body. Therefore, if the growth of the biofilm can be suppressed, it is very useful as an antibacterial member.

Further, the second protrusion 14 in the present invention has an effect of piercing the cells of the bacterium and physically killing the bacterium. Regarding this, it is described in the following references that black silicon having a structure in which pointed protrusions having a height of about 100 nm are densely packed has an effect of physically killing bacteria.

Reference 1:
Ivanova E. et al. , Bactericidal activity of black silicon, Nature Communications, Vol. 4, p. 2838 (2013)
Reference 2:
Hasan J. et al. , Selective bacterial activity of nanopatterned superhydrophobic cicada Psaltoda clarennis wing surfaces, Appl. Microbiol. Biotechnol. , Vol. 97, p. 9257 (2013)
The first projections 12 have an effect of suppressing the growth of biofilm, but do not have an effect of killing the bacteria themselves. However, even if the growth of the biofilm has progressed for some reason, the antibacterial member 10 has the second protrusions 14, so that the bacteria in the biofilm can be physically killed.

Further, although the second protrusion 14 has an effect of physically killing the bacteria, since the second protrusion 14 is extremely fine, if the bacteria accumulate to the extent that the second protrusion 14 is covered, after that, The second projection 14 does not reach the bacteria that have come in, and the effect of the second projection 14 cannot be exerted. However, even when the second protrusion 14 is covered with the bacteria, the growth of the biofilm can be suppressed by providing the first protrusion 12 on the antibacterial member 10. That is, by having both the first protrusion 12 and the second protrusion 14, a stronger antibacterial function can be obtained.

Hereinafter, a mechanism of forming a biofilm on the substrate will be described. FIG. 2 is a flow diagram illustrating the mechanism of forming a biofilm on the surface of a base material. As shown in Figure 2, biofilms occur in the following order:
S1: When a clean substrate comes into contact with water, bacteria (Pioneer's bacteria) adhere to the interface between water and the substrate S2: Extracellular polysaccharide (EPS) secreted on the surface of the bacteria S3: Pioneer bacteria start to grow and form primary colonies coated with polysaccharide (glycocalyx) S4: Glycocalyx incorporates other types of bacterial cells to form primary colonies Secondary colonies that metabolize the excretion of colonies (pioneer colonies) are formed in the upper layer of the primary colony. S5: Microorganisms that metabolize the excretion of secondary colonies are attached and a multi-layer colony structure is sequentially formed. As described above, the antibacterial member 10 of the present invention is provided with the first projection 12 on the surface of the base material 11 to form the concavo-convex structure, so that bacteria can form primary colonies. It is considered that the scaffold becomes structurally unstable during the formation process and has an effect of breaking due to the internal stress of the primary colony itself. Therefore, it is considered that the processes after S3 do not occur and the growth of the biofilm is suppressed.

The diameter of the first protrusion 12 is 0.5 μm or more and 20 μm or less. Within this range, it is preferable that the diameter of the first protrusion 12 is about the same as the diameter of the target microorganism whose growth is to be suppressed (hereinafter referred to as “target microorganism”). Even when the diameter of the first protrusion 12 is too larger than the target bacterium, or conversely when the diameter of the first protrusion 12 is too smaller than the target bacterium, the primary colony cannot be effectively broken. Note that the diameter of the first protrusion 12 is “about the same” as the size of the target bacterium, and the two do not necessarily have to be the same. The diameter of the first protrusion 12 may be within a range of values that can obtain the effect of breaking the primary colonies. The diameter of the first protrusion 12 can be determined by conducting an experiment for verifying the breaking effect for each target bacterium. The diameter of the target bacterium is, for example, bacteria: about 0.5 μm, yeast: about 5 μm, and mold: about 20 μm.

The shape of the first protrusion 12 is a cylindrical shape in FIG. 1, but is not limited to this. For example, it may be a polygonal prism such as a triangular prism or a square prism. In this case, the “diameter of the first protrusion 12” means the diameter of the circumscribing circle.

The diameter of the second protrusion 14 is 1 nm or more and less than 500 nm. If the diameter of the second protrusion 14 is less than 1 nm, it becomes difficult to manufacture. Further, considering the lower limit value (0.5 μm (=500 nm)) of the diameter of the first protrusion 12, the upper limit of the diameter of the second protrusion 14 is preferably less than 500 nm. Since the second protrusion 14 has such a size, the second protrusion 14 can be formed on the bottom surface (top surface) 13 of the first protrusion 12. Further, the protrusions having a diameter on the nanometer scale are sufficiently smaller than the cells of the bacterium, and the effect of piercing the cells of the bacterium and physically killing the bacterium can be sufficiently obtained.

Although the shape of the second protrusion 14 is a cylindrical shape in FIG. 1, the shape is not limited to this. For example, it may be a polygonal prism such as a triangular prism or a square prism. In this case, the “diameter of the second protrusion 14” means the diameter of the circumscribed circle.

The Young's modulus of the first protrusion 12 and the second protrusion 14 is preferably more than 0.004 GPa and 5 GPa or less. If the Young's modulus of the first protrusion 12 and the second protrusion 14 is less than 0.004 GPa, the structural stability (water resistance) of the protrusions 12 and 14 in water becomes insufficient. If the Young's modulus of the protrusions 12 is larger than 5 GPa, the effect of breaking the primary colonies becomes insufficient, and if the Young's modulus of the protrusions 14 is larger than 5 GPa, the effect of physically killing the bacteria becomes insufficient.

FIG. 3A is a top view showing a first example of the arrangement of the first protrusions of the antibacterial member of the present invention, and FIG. 3B is a top view showing a second example of the arrangement of the first protrusions of the antibacterial member of the present invention. It is a figure. The arrangement of the first protrusions 12 on the base material 11 of the antibacterial member 10 of the present invention is not particularly limited, but may be a square lattice as shown in FIG. 3A, for example. Further, as shown in FIG. 3B, it may be a three-sided grid.

The distance L (pitch interval) between the centers of the adjacent first protrusions 12 is preferably 1.5 times or more and less than 3 times the diameter of the first protrusions 12. If the distance L is less than 1.5 times the diameter of the first protrusion 12, a sufficient amount of uneven structure cannot be secured, and the effect of the uneven structure (the effect of biofilm suppression by breaking primary colonies) is sufficient. Can't get to. Further, when the distance L is three times or more the diameter of the first protrusion 12, the proportion of the recesses becomes too large and bacteria enter the recesses, and the effect of suppressing biofilm growth cannot be obtained sufficiently.

Further, the ratio h ₁ /r ₁ (aspect ratio) of the height h ₁ and the diameter r ₁ of the first projections 12 is preferably 1 or more and 5 or less, respectively. If the aspect ratio is less than 1, the effect of the uneven structure cannot be sufficiently obtained. If the aspect ratio is larger than 5, the structure may become unstable.

FIG. 4A is a top view showing a first example of the arrangement of the second protrusions of the antibacterial member of the present invention, and FIG. 4B is a top view showing the second example of the arrangement of the second protrusions of the antibacterial member of the present invention. It is a figure. In the antibacterial member 10 of the present invention, the arrangement of the second protrusions 14 provided on the upper surface 13 of the first protrusions 12 is not particularly limited, but may be a square lattice, for example, as shown in FIG. 4A. it can. Further, as shown in FIG. 4B, it may be in a three-sided lattice shape.

The distance L (pitch interval) between the centers of the adjacent second protrusions 14 is not particularly limited as long as the second protrusions 14 are formed.

The ratio between the height and the diameter of the second protrusion 14 (aspect ratio: height h ₂ /diameter r ₂ ) is preferably 1 or more and 5 or less. If the aspect ratio is less than 1, the effect of breaking through and killing the bacteria cannot be sufficiently obtained. If the aspect ratio is larger than 5, the structure may become unstable.

The material of the base material 11 is not particularly limited as long as it can form the first protrusions 12 and the second protrusions 14, and can be selected according to the member to be given antibacterial properties. For example, resins such as epoxy resin, acrylic resin, PDMS (polydimethylsiloxane) and COP (cycloolefin polymer) can be used. It may also be a metal such as stainless steel.

5A is a side view showing a first example of the shape of the base material of the antibacterial member of the present invention, and FIG. 5B is a perspective view showing a second example of the shape of the base material of the antibacterial member of the present invention. The shape of the base material 11 is not particularly limited as long as the first protrusion 12 and the second protrusion 14 can be formed, and can be selected according to the member to be given antibacterial properties. For example, as shown in FIGS. 1 and 5A, it may be in the form of a film. When the base material 11a is in the form of a film, advantages such as improved portability and easier construction at the site where the antibacterial member 10a is used can be obtained. If the adhesive 15 is provided on the surface opposite to the surface provided with the protrusions, it can be easily attached to a member to which antibacterial property is desired.

Further, as shown in FIG. 5B, the base material 11b may be tubular. In this case, the first protrusion 12 and the second protrusion 14 may be provided on the inner surface of the tubular base material 11b. The antibacterial member 10b having such a shape can be applied to a washing tub of a drum type washing machine.

Next, a method for manufacturing the above-mentioned antibacterial member will be described. As shown in FIG. 5A, when the base material 11 is a film-shaped resin, the first protrusions 12 and the second protrusions 14 can be produced by, for example, nanoimprinting. Specifically, the first protrusion 12 can be formed on the surface of the resin film base material by pressing a metal mold having the same uneven structure as the first protrusion 12 against the resin film and applying heat. Further, a metal die having the same uneven structure as the second protrusion 14 is pressed against the resin film on the base material on which the first protrusion 12 is formed, and heat is applied to the upper surface of the first protrusion 12. The second protrusion 14 can be formed.

When the base material 11 is made of metal, the first protrusion 12 and the second protrusion 14 can be formed on the surface of the metal base material by, for example, metal printing. Specifically, a metal mold having the same concavo-convex structure as the first protrusion is pressed against the metal base material, and heat and pressure are applied to form the first protrusion 12 on the surface of the metal base material. .. Further, a metal mold having the same uneven structure as the second projection is pressed against the base material on which the first projections 12 are formed, and heat and pressure are applied to the top surface of the first projections. The second protrusion 14 can be formed on the surface.

As shown in FIG. 5B, when the base material 11 is a metal tubular member and the first protrusion 12 and the second protrusion 14 are provided inside the tubular member, the antibacterial member 10b is formed by using, for example, a roll technique. Can be produced. Specifically, the first projection 12 is formed on the surface of the base material 11b by rotating the base material 11b while pressing the base material 11b against a cylindrical original plate having the same uneven structure as the first projection 12 on the outer surface. However, the substrate can be formed into a tubular shape. Furthermore, the base material 11b having the first projections 12 is pressed and rotated on a cylindrical original plate having the same projections and depressions structure as the second projections 14 on the outer surface of the first projections 12 to rotate. The base material can be formed into a tubular shape while forming the second protrusion 14 on the upper surface.

In the nanoimprinting process, the metal printing process, and the roll technique described above, the antibacterial members 10a and 10b are made of the base material 11a, because the first projection 12 and the second projection are formed on a part of the surface of the base material 11a, 11b. 11b and the first protrusion 12 and the second protrusion 14 are integrally molded. Of course, if sufficient adhesion between the base materials 11a and 11b and the first projections 12 and the second projections 14 is obtained, the base materials 11a and 11b and the first projections 12 and the second projections 14 can be separated. It may be prepared and adhered. Alternatively, the base materials 11a and 11b and the first protrusion 12 may be integrally formed, and only the second protrusion 14 may be separately prepared and adhered.

Hereinafter, the present invention will be described in more detail based on examples. In the following examples, it was verified that the first protrusion 12 has an effect of suppressing the growth of biofilm. In addition, it is described in the above-mentioned reference that the second protrusion 14 has an effect of physically killing bacteria.

(1) Confirmation of biofilm suppression effect Using a resin film as the base material 11, two antibacterial members (Example 1 and Comparative Example 1) having different diameters of the first protrusions 12 were produced. The resin film was made of COP (Young's modulus: 0.22 GPa). The size of the first protrusion 12 of the antibacterial member of Example 1 was 1 μm, and the size of the first protrusion 12 of Comparative Example 1 was 5 μm. The pitch interval L was 1.75 times the diameter of the first protrusion 12, and the aspect ratio of the first protrusion 12 was 1. The formation of the first protrusions 12 on the resin film was performed by nanoimprinting a nickel mold.

Bacteria were cultured on the above-mentioned antibacterial member 10 by the following procedure. Staphylococcus aureus (diameter: about 1 μm) was used as the test bacterium. A test bacterial solution was obtained by suspension culture in a trypcase soy broth medium until the test bacterial count reached 10 ⁷ to 10 ⁸ /mL. The glass petri dish and antibacterial member 10 were subjected to high-pressure steam sterilization (121° C., 15 minutes), the antibacterial member 10 of Example 1 and Comparative Example 1 was placed on the glass petri dish, and then the test bacterial solution was added. The SCD broth medium was exchanged once a day and cultured for 21 days.

FIG. 6 is a SEM observation photograph of the surface of the antibacterial member of Example 1, and FIG. 7 is a SEM observation photograph of the surface of the antibacterial member of Comparative Example 1. In both of the antibacterial members of Example 1 and Comparative Example 1, a region where the first protrusion 12 is provided (a region surrounded by a dotted line in FIGS. 6 and 7) and a region where the first protrusion 12 is not provided ( There is a region other than the region surrounded by the dotted line in FIGS. 6 and 7. As shown in FIGS. 6 and 7, in both of the antibacterial members of Example 1 and Comparative Example 1, bacteria 20 are growing in the area where the first protrusion 12 is not provided.

On the other hand, looking at the region where the first protrusions 12 are provided, in the antibacterial member of Example 1, almost no bacteria were proliferated, whereas in the antibacterial member of Comparative Example 1, the bacteria 20 were the first protrusions. It also proliferates in the area where 12 is provided. From this, it was found that the antibacterial member provided with the first protrusion 12 having the same diameter as S. aureus can suppress the growth of bacteria.

(2) Evaluation of Water Resistance of Antibacterial Member Next, by changing the resin material of the base material, an antibacterial member (Examples 2 to 4 and Comparative Example 2) having the first protrusions 12 having a diameter of 1 μm and a height of 5 μm was prepared by nanoimprinting. did. The pitch interval L was 1.75 times the diameter of the first protrusion 12, and the aspect ratio of the first protrusion 12 was 1. The materials of the antibacterial members of Examples 2 to 4 and Comparative Example 2 and their Young's moduli are shown in Table 1 described later. Young's modulus was measured using the nanoindentation method.

After immersing the produced antibacterial member in water, the surface structure was observed by SEM (Scanning Electron Microscope), and water resistance (structural stability in water) was evaluated. As a result of the observation, when the first projections 12 are not bonded to each other and the concavo-convex structure of the base material surface is not collapsed, “pass” is determined, the first projections 12 are bonded to each other and the concavo-convex structure of the base material surface is collapsed What was done was evaluated as "fail". The water resistance evaluation results are also shown in Table 1 described later.

As shown in Table 1, in Examples 2 to 4 in which the Young's modulus of the material of the antibacterial member satisfies the requirements of the present invention, as a result of SEM observation, the first protrusions 12 are not bonded to each other, and the water resistance evaluation All the results were “pass”. On the other hand, in Comparative Example 2 in which the Young's modulus of the material of the antibacterial member does not satisfy the regulations of the present invention, the result of water resistance evaluation was “fail”.

FIG. 8 is a SEM observation photograph of the surface of the antibacterial member of Comparative Example 2 after the water resistance test. As shown in FIG. 8, a phenomenon was observed in which the first protrusions 12 were bonded to each other and the concavo-convex structure collapsed. It is considered that this is because the material of the antibacterial member of Comparative Example 2 has low strength (Young's modulus: 0.002 to 0.004 GPa), and the first protrusions 12 are bonded to each other by a force such as surface tension or static electricity.

From this, it was demonstrated that the Young's modulus of the first protrusions 12 is preferably 0.005 GPa or more and 5 GPa or less in order to stably maintain the uneven structure on the surface of the base material 11.

As described above, according to the present invention, it is possible to provide an antibacterial member capable of suppressing biofilm growth on the surface of a member to be antibacterial and further physically killing bacteria without providing an antibacterial film. Was shown. In addition, it was shown that the uneven structure provided on the surface of the base material 11 can be stably maintained even when contacted with water, and the antibacterial effect can be maintained. The antibacterial member of the present invention can be used in various fields such as medical care, foods and electric appliances.

It should be noted that the present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Further, with respect to a part of the configuration of each embodiment, other configurations can be added/deleted/replaced.

10, 10a, 10b... Antibacterial member, 11, 11a, 11b... Base material, 12... First projection, 13... First projection bottom surface, 14... Second projection, 15... Adhesive agent, 20... Fungus, L: pitch interval.

Claims (8)

A base material; a plurality of first projections provided so that one bottom surface is in contact with the surface of the base material; and a plurality of second projections provided on the other bottom surface of the first projection. Then
The diameter of the first protrusion is 0.5 μm or more and 20 μm or less, the diameter of the second protrusion is 1 nm or more and less than 500 nm, and the Young's modulus of the first protrusion and the second protrusion is 0.004 GPa. The antibacterial member is characterized in that it is larger than and less than or equal to 5 GPa. The antibacterial member according to claim 1, wherein the distance between the centers of the adjacent first protrusions is 1.5 times or more and less than 3 times the diameter of the first protrusions. The antibacterial member according to claim _{1, wherein} a ratio h ₁ /r ₁ of the height h ₁ of the first protrusion and the diameter r ₁ is 1 or more and 5 or less. The antibacterial member according to claim 1, wherein a ratio h ₂ /r ₂ of the height h ₂ and the diameter r ₂ of the second protrusion is 1 or more and 5 or less. The substrate is made of a film-shaped member, the first protrusion and the second protrusion are provided on one surface of the film-shaped member, and the adhesive is provided on the other surface of the member. The antibacterial member according to any one of claims 1 to 4, wherein The antibacterial member according to any one of claims 1 to 4, wherein the base material is a metal. The said base material consists of a tubular member, The said 1st protrusion and the said 2nd protrusion are provided inside the said tubular member, The any one of Claim 1 to 4 characterized by the above-mentioned. The antibacterial member described. The antibacterial member according to any one of claims 1 to 4, wherein the base material, the first protrusion, and the second protrusion are integrally molded.

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