JP2019072475A - Antibacterial material, and antibacterial component including the same - Google Patents

Abstract

To provide an antibacterial material capable of killing bacteria effectively.SOLUTION: In an antibacterial material 1 including a plurality of columnar projections 3...3, each columnar projection 3 has a shape expressed by following relational expression: Asp≥1.80exp(-0.00083p), where, Asp...aspect ratio of a vertical sectional form passing the center of each columnar projection 3, p...center distance between adjacent two columnar projections 3, 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an antibacterial material and an antibacterial member provided with the same, which can kill or reduce bacteria by a microstructure that is a physical structure.

  It has been reported that semi-ankles have antibacterial properties (Non-patent Document 1). In Non-Patent Document 1, there is a microstructure composed of a large number of nano-sized pillars in a semi-anther, and when it exhibits antibacterial properties by destroying a bacterial cell membrane by capillary force caused by this microstructure. It is stated. Furthermore, it has been reported that microstructures (nano-pillars, which are nano-sized pillars) formed of artificial materials (specifically, black silicon) have antibacterial properties like semi-scissors (Non-Patent Document 2) .

Elena P. Ivanova et al., “Natural Bacterial Surfaces: Mechanical Rupture of Pseudomonas aeruginosa Cells by Cicada Wings”, small, 2012, Volume 8, Issue 16, p.2489-2494. Elena P. Ivanova et al., "Bactericidal activity of black silicon", Nature Communications, 26 November 2013

  However, in Non-Patent Document 2, the shape and density of an artificially formed microstructure were not examined.

  Therefore, an object of the present invention is to provide an antibacterial material capable of effectively killing bacteria.

The present invention is an antibacterial material provided with a plurality of columnar protrusions, and each of the columnar protrusions has a shape represented by the following relational expression.

Asp 1.8 1.80 exp (-0.00083 p)

Asp: Aspect ratio of the longitudinal sectional shape passing through the center of each columnar projection
p ... Center-to-center distance between two adjacent columnar projections

  According to this configuration, the bacteria can be killed by attracting the bacteria to the surface of each of the columnar projections formed with the predetermined dimensions specified by the relational expression and destroying the cell membrane.

  Furthermore, the shape of each of the columnar protrusions can be cylindrical.

  According to this configuration, the plurality of columnar protrusions can be easily formed by, for example, a metal assist etching method, a nanoimprint technique, an electron beam lithography, or the like.

  Further, each of the columnar protrusions may be made of silicon or resin.

  According to this configuration, the antibacterial material provided with the plurality of columnar protrusions can be easily obtained by silicon or resin which is a general material.

  Furthermore, at least the surface around the tip of each of the columnar protrusions may be hydrophobic.

  According to this configuration, the antibacterial power can be improved as compared to those in which at least the surface around the tip of each columnar protrusion has hydrophilicity.

  Further, each of the columnar protrusions may be made of silicon, and the hydrophobic surface may be a surface from which a silicon oxide film is removed.

  According to this configuration, by removing the silicon oxide film, it is possible to easily realize a hydrophobic surface with an improved antibacterial power on each columnar protrusion.

  Furthermore, the plurality of columnar projections can include columnar projections in which molecules having a hydrophobic group are present on the surface.

  According to this configuration, it is possible to easily realize the hydrophobicity on the surface of the columnar protrusion by positioning the molecule having the hydrophobic group on the surface.

  Furthermore, the plurality of columnar protrusions may be configured by mixing a columnar protrusion having a molecule having a hydrophobic group on the surface and a columnar protrusion having a molecule having a hydrophilic group on the surface.

  According to this configuration, among the plurality of columnar protrusions, by adjusting the mixture ratio of one having a molecule having a hydrophobic group on the surface and one having a molecule having a hydrophilic group on the surface, the plurality of columns Desired wettability can be achieved over the entire protrusion.

  And, according to the present invention, the antibacterial target bacterium is a gram-negative bacterium having an elongated shape and flagellum, and the gap between the side surfaces of the two adjacent columnar projections is greater than the maximum length excluding the flagella of the target bacterium. Can also be small.

  According to this configuration, it is possible to provide an antibacterial material that exerts an optimum antibacterial action on target bacteria of different sizes.

  And this invention is an antibacterial member used for the part which contact | connects a liquid, Comprising: It is an antibacterial member which provided the antibacterial material in any one of the said so that these columnar protrusion may protrude with respect to the said liquid.

  According to this configuration, bacteria in the liquid can be effectively killed.

  According to the present invention, bacteria in liquid can be attracted to columnar projections to provide an antimicrobial material that can be effectively killed.

It is a schematic perspective view which expanded and showed a part of antibacterial material concerning a 1st-a 3rd embodiment of the present invention. (A)-(f) is a schematic perspective view which showed the procedure in the case of producing the said antibacterial material by a metal assist etching method to process order. It is a graph which shows the result of having evaluated the antimicrobial property of the said antimicrobial material. It is a graph which shows the relationship between a contact angle and the density of the cell to which it attached in the test piece which equipped the surface with the columnar protrusion, and the test piece with flat surfaces. (A) shows a columnar protrusion having a molecule having a hydrophilic group (hydroxyl group) at its tip on the surface, and (b) shows a columnar protrusion having a molecule having a hydrophobic group (methyl group) at its tip on its surface c) shows a flat surface where molecules having a hydrophilic group (hydroxyl group) at the tip are present on the surface, and (d) shows a flat surface where a molecule having a hydrophobic group (methyl group) at the tip is present on the surface Perspective view. It is a microscope image which shows the difference in the adhesion number of colon_bacillus | E._coli with the area | region with and without a columnar protrusion (nano structure) on the surface. It is a graph which shows the time change of the dead / dead cell number of E. coli regarding the relationship between a surface property and an antimicrobial property. It is a graph which shows the time change of the survival rate of E. coli in the surface of a different contact angle. It is a schematic longitudinal cross-sectional view for demonstrating the dimension for evaluating the shape of the said antibacterial material. It is a graph which shows the relationship between the clearance (Gap) between the side surfaces of two adjacent columnar protrusions and the survival rate (viable rate of E. coli) in a case where the distance between the centers of two adjacent columnar protrusions is three patterns. It is a graph which shows the relationship between the height of pillar-shaped projections and the survival rate (viable rate of E. coli) in a case where the distance between centers of two adjacent pillar-shaped projections is three patterns. It is a graph which shows the relationship between the aspect-ratio (Aspect ratio) of columnar protrusion, and the survival rate (viable rate of E. coli) in the center-to-center distance of adjacent two columnar protrusions in three patterns. This is a graph showing the relationship between the aspect ratio (Aspect ratio) of columnar protrusions and the survival rate (Living bacteria ratio) of E. coli in a pattern in which the center distance between two adjacent columnar protrusions is 4 patterns, a) is the center-to-center distance (Pitch) 200 nm, (b) is the center-to-center distance (Pitch) 500 nm, (c) is the center-to-center distance (Pitch) 1000 nm, (d) is the center-to-center distance (Pitch) The case of 2000 nm is shown. It is a graph for analyzing the conditions which exhibit an antimicrobial, Comprising: When the center distance (Pitch) distance between two adjacent columnar projections (Pitch) is 1000 nm, the aspect ratio of columnar projections and the survival rate of E. coli (viable ratio) Show the relationship with logarithm. When the survival rate (viable rate) of E. coli is 1% or 0.1%, the distance between the centers of two adjacent pillars (Pitch) and the aspect ratio of the pillars (Aspect ratio) It is a graph which shows a relation. It is a graph which shows the time change of the resonance resistance (Resistance shift) in QCM method, (a) shows the influence of the presence or absence of a nanostructure, (b) shows the influence of a contact angle, (c) shows the flagella of a fungus. Indicates the influence of the presence or absence. It is a microscope image which shows the state of the quartz oscillator surface after the measurement in QCM method. (A)-(c) are schematic which shows the antimicrobial mechanism estimated. It is the schematic which shows the relationship of the magnitude | size of the antibacterial material which concerns on 1st Embodiment of this invention, and the object bacteria of an antibacterial.

First Embodiment
The present invention will be described by taking the first embodiment. Here, the term "antibacterial" described in the present specification corresponds to "a state in which the growth of bacteria on the surface of the product is suppressed" as defined in JIS Z 2801. Specifically, "antibacterial" means a state in which the number of microorganisms (especially bacteria) present around the antibacterial material is not reduced or increased due to death.

  First, an outline of the present embodiment will be described. The inventor of the present application formed a self-assembled film to form a microstructure (also referred to as “nanostructure”) whose dimensions (distance, height, cross-sectional dimensions, etc.) and density are arbitrarily set. Then, the wettability of the surface was adjusted to obtain a microstructure having a hydrophilic and / or hydrophobic (water repellent) surface. It has been confirmed that microorganisms (bacteria) adhere to the hydrophobic surface of the microstructure thus obtained more positively than the hydrophilic surface and die.

  FIG. 1 shows an antibacterial material 1 according to the present embodiment provided with columnar protrusions (nanopillars) 3 as a plurality of fine structures on a substrate 2. FIG. 1 is a schematic view and does not exactly show the antibacterial material 1 of the present embodiment. The substrate 2 and each columnar protrusion 3 are made of silicon. The shape of each columnar protrusion 3 is cylindrical in this embodiment. However, the shape of each columnar protrusion 3 is not particularly limited, and may be polygonal columnar shape, conical shape, polygonal pyramid shape. However, it is preferable to make the shape into a cylindrical shape, for example, since a plurality of columnar protrusions 3 can be easily formed since a self-assembled film can be formed by, for example, a metal assist etching method described later.

  The surface of at least the tip of each columnar protrusion 3 is hydrophobic. This is to positively attach bacteria. However, in the present invention, the hydrophobicity of the surface is not an essential requirement, and may be hydrophilic. Also, in general, “hydrophobic” corresponds to the case where the contact angle of water (specifically, the static contact angle) exceeds 90 °, but is not necessarily limited thereto, for example, relative It is also possible to determine whether it is hydrophobic or hydrophilic. The above-mentioned "periphery of tip" is a surface on the end face side among the end face and the side face. In order to attach the bacteria effectively, it is sufficient if the surface around the tip of each columnar protrusion 3 has hydrophobicity. Details on adhesion of bacteria will be described later.

  With regard to the arrangement of the plurality of columnar protrusions 3... 3 and the dimensions of the respective columnar protrusions 3, the distance between the centers of two adjacent columnar protrusions 3 (see FIG. 9) is 500 nm or less . The lower limit value of the center-to-center distance is determined in relation to the setting of the following gap. Furthermore, the gap (see FIG. 9) between the side surfaces of the two adjacent columnar projections 3 is 20 nm or more and 200 nm or less, or the aspect ratio of the longitudinal sectional shape passing through the centers of the respective columnar projections 3 is 1 It is above. By setting the dimensions in this manner, bacteria can be attracted to the surface of each of the hydrophobic columnar projections 3 to destroy the cell membrane, thereby killing the bacteria.

  The antimicrobial material 1 of the present embodiment is manufactured by a metal assist etching method which is an example of a method according to a wet etching technique. The production procedure is shown in order of steps in FIG. 2 (a) to FIG. 2 (f). 2 (a) to 2 (f) are schematic views, and the dimensional relationships shown are not accurate.

  First, a plurality of polystyrene beads (hereinafter simply referred to as "beads") B of a predetermined size are spread on the surface of a flat silicon plate 2a so as to be in the closest packed state without overlapping, and the state shown in FIG. I assume. Thereby, a self-assembled film composed of a plurality of beads B... B is formed on the silicon plate 2a. In the close-packed state, the diameter of each bead B is, in other words, the center-to-center distance S (see FIG. 9) between two adjacent columnar protrusions 3 after formation. For this reason, a plurality of columnar protrusions 3... 3 having a desired center-to-center distance S can be obtained by this processing.

  Next, each bead B is irradiated with plasma (in the present embodiment, oxygen plasma) to carbonize the beads B so that the diameter of each bead B is reduced at the same position on the silicon plate 2a, as shown in FIG. Let it be in the state shown. That is, the diameter of the reduced bead B becomes the diameter D (see FIG. 9) of the columnar protrusion 3 after formation. For this reason, the columnar projections 3 having a desired diameter can be obtained by this process.

  Next, using a variety of film forming methods, a noble metal is deposited from above on the silicon plate 2a to form a thin film F, whereby the state shown in FIG. 2C is obtained. In the present embodiment, a gold thin film F is formed on a silicon plate by sputtering. Here, since a plurality of beads B are present on the silicon plate 2a, each bead B is shaded, and a noble metal is added to the circular area R of the diameter of each bead B immediately below each bead B. The thin film F is not formed.

  Next, the one shown in FIG. 2C is dipped in an etching solution. The etching solution of the present embodiment is a mixed aqueous solution of hydrogen peroxide and hydrofluoric acid. By this immersion, silicon in a portion in contact with the thin film F of the noble metal in the silicon plate 2a is selectively scraped off. Along with this, the thin film F descends, and as shown in FIG. 2D, a plurality of fine columnar pillars 3 are formed below the plurality of beads B, and a substrate 2 is formed. Ru.

  Next, the thin film F of the noble metal is removed to obtain the state shown in FIG. For removal, aqua regia is used in this embodiment. In addition, it can carry out also with the solution which mixed iodine and potassium iodide. Then, by removing the beads B, the antibacterial material 1 is completed as shown in FIG. 2 (f). However, in the state shown in FIG. 2F, the surface of the columnar protrusion 3 is still covered with the silicon oxide film formed by the influence of the metal assist etching.

  Thus, the metal-assisted etching method using the plurality of beads B can easily provide the antibacterial material 1 including the plurality of columnar projections 3 having a desired size and density. By using a self-assembled film, it is possible to reduce the cost and the time required for production. The antibacterial material 1 can be used directly as an object provided with a plurality of columnar protrusions 3... 3 obtained by the above-mentioned metal-assisted etching method, or this object is transferred to a resin (for example, silicone rubber) It is also possible to use a molded article such as a resin (for example, silicone rubber) produced by first forming a mold / transfer mold in which the object is shaped, and using the mold / transfer mold. By molding and transferring, it is possible to mass-produce the antibacterial material. Nanoimprint technology, electron beam lithography, etc. can be used as molding / transfer technology. In this manner, the antimicrobial material 1 having a plurality of columnar protrusions can be easily obtained from silicon or resin which is a common material. With regard to the resin material, the inventor of the present application has actually produced the antibacterial material 1 by PDMS, which is a silicone rubber, and confirmed that the antibacterial property is exhibited.

  The surface of each columnar protrusion 3 formed by the metal assist etching method is hydrophilic because it is covered with a silicon oxide film (film of silicon dioxide). By removing the silicon oxide film, the surface of each columnar protrusion 3 can be made hydrophobic. That is, the hydrophobic surface is the surface from which the silicon oxide film is removed. In the present embodiment, the oxide film is removed by immersion in a mixed solution of hydrofluoric acid and ammonium fluoride. By removing the silicon oxide film in this manner, the hydrophobicity can be easily realized on the surface of each columnar protrusion 3. Further, since the portion not to be immersed can be made hydrophilic while the portion to be immersed can be made hydrophobic, for example, only the surface around the tip of each columnar protrusion 3 should be made hydrophobic. For example, hydrophobicity and hydrophilicity can be achieved with respect to desired regions.

  Adjustment of the wettability (contact angle) of the surface of the columnar projections 3 can be realized by appropriately providing a molecule having a hydrophobic group or a molecule having a hydrophilic group on the surface of each columnar projection 3. For example, first, a gold thin film is formed on the surface of each columnar protrusion 3. Then, as shown in FIGS. 5 (a) and 5 (b), a thiol group that easily bonds to gold is held at the base end, and a molecule having a hydroxyl group (hydrophilic group) or a methyl group (hydrophobic group) is bonded to the tip. . By doing so, in the present embodiment, the contact angle (water) can be arbitrarily adjusted in the range of 10 ° to 140 ° on the surface of each columnar protrusion 3.

  As described above, the plurality of columnar projections 3... 3 are configured to be a mixture of the columnar projections 3 on the surface of which the molecules having hydrophobic groups are present and the columnar projections 3 on the surfaces of which the molecules having hydrophilic groups are present. it can. By positioning the molecule having a hydrophobic group on the surface, it is possible to easily realize the hydrophobicity on the surface of the columnar protrusion 3. Further, among the plurality of columnar protrusions 3... 3, the plurality of columnar protrusions is adjusted by adjusting the mixture ratio of one having molecules having a hydrophobic group on the surface and one having molecules having a hydrophilic group on the surface. Desired wettability can be realized in the whole of 3. In addition, in one columnar projection 3, it is also possible to make a molecule having a hydrophobic group and a molecule having a hydrophilic group coexist on the surface.

  The antimicrobial material 1 formed in this manner can be, for example, in the form of a block or sheet. The antibacterial material 1 is an antibacterial member used in a portion in contact with a liquid, and can be used by being incorporated in the antibacterial member provided with a plurality of columnar protrusions 3 ... 3 provided in the antibacterial material 1 so as to protrude to the liquid . By using this antibacterial member, bacteria in the liquid can be effectively killed. This antibacterial member can be used as a piping member for water and sewage, piping member in a home, a member touching liquid in facilities requiring hygiene management such as a food factory, and a member constituting a medical instrument or a medical analysis device.

  Next, since the inventor of the present application performed various tests on the antibacterial material 1 of the present embodiment, it will be described. All the tests described below were conducted in accordance with JIS Z 2801. Also, the strain of E. coli used for the test is NBR3972.

FIG. 3 shows the product of the diameter D and height H (see FIG. 9) of the columnar projections 3, that is, the 24-hour passage survival rate of E. coli with respect to the longitudinal sectional area. For flat test pieces, the longitudinal cross-sectional area is zero. The lower end (10 ^-5 %) of the graph vertical axis also includes the case where it is below the detection limit. In the test piece having the columnar projections (nanopillars) 3, the center-to-center distance S (see FIG. 9) between two adjacent columnar projections 3 is set to 200 nm.

  The square points in FIG. 3 relate to the test piece (having a water contact angle of 23 ° and relative hydrophilicity with a water contact angle of 23 °), and the round points represent silicon on the surface. Is for a test specimen with exposed pillars 3 (water contact angle is 77 ° and relatively hydrophobic), the X-shaped point is for a flat test specimen whose surface is covered with silicon dioxide, The diamond points are for flat specimens with exposed silicon on the surface.

  In general, if the survival rate is 1% or less, it can be evaluated that there is antibacterial activity (JIS Z 2801). As shown in FIG. 3, among the test pieces having the columnar projections 3, the one having a hydrophilic surface had a high survival rate in the region where the longitudinal cross-sectional area is small, but the survival rate decreased as the longitudinal cross-sectional area increased. . On the other hand, it was confirmed that among the test pieces having the columnar projections 3, the one having a hydrophobic surface had a low survival rate regardless of the longitudinal cross-sectional area, and exhibited excellent antibacterial properties.

  Next, the relationship between surface wettability and bacterial adhesion is shown in FIG. A hydrophobic group and a hydrophilic group are provided on the surface of each of the test piece provided with the columnar projection 3 and the flat test piece to prepare a plurality of types in which the contact angle (water) is changed. A culture solution containing the same number of E. coli was dropped onto these test pieces and covered with a lid, and the number of E. coli adhered to the test pieces was observed with a microscope and counted.

  The round points in FIG. 4 refer to test pieces with a plurality of columnar projections 3... 3 (see FIGS. 5 a and 5 b), and the square points refer to flat test pieces (see FIG. 5 (c) and FIG. 5 (d)). The horizontal axis in FIG. 4 indicates the contact angle, and the vertical axis indicates the E. coli density of 1 mm square. From the curve connecting the points, it is shown that the larger the contact angle (hydrophobic), the higher the adhesion and the higher the presence of the columnar projections 3 the higher the adhesion. In addition, as shown in FIG. 4, in the test piece provided with the columnar projections 3, when the contact angle exceeds 100 °, the increase in the attachment number of E. coli slows but this is because most of the E. coli added is attached. It is guessed that it has fallen.

  Moreover, FIG. 6 is a microscope image, It turned out that there exists a clear difference in the number of adhesion of E. coli in the area | region with and without the area | region 3 of columnar protrusion ("nano structure" in FIG. 6).

  From these results, it has become clear that at least in E. coli, the adhesion is higher as the contact angle is larger, and the adhesion is higher when the columnar projections 3 are present. It can be inferred that this is at least the same for microorganisms with flagella.

In addition, for the life and death of bacteria, a fluorescent dye that stains live cells because it can penetrate cell membranes, and a fluorescent dye that stains dead cells (cells whose cell membranes are broken) because it can not permeate cell membranes By observing under a microscope, the number of living bacteria and dead bacteria were counted from the difference in fluorescence color. A test piece provided with a plurality of columnar protrusions 3 ... 3 and having a contact angle (water) adjusted to 100 ° was used. The results are shown in FIG. The horizontal axis in FIG. 7 indicates the elapsed time, and the vertical axis indicates the number of cells counted in the field of view of the microscope. As shown in FIG. 7, it can be seen that the more hydrophobic the surface of the test strip is, the more cells are killed than the more hydrophilic surface.

  Further, FIG. 8 shows the relationship between the wettability of the surface of the test piece and the killing speed of E. coli. The triangle points in FIG. 8 are for specimens with a contact angle (water) of 100 °, the square points are for specimens with a contact angle (water) of 70 °, and the round points are for the contact angle (water ) For very low ultrahydrophilic test strips. The results are shown in FIG. The horizontal axis in FIG. 8 is the elapsed time, and the vertical axis is the survival rate of E. coli. As shown in FIG. 8, the larger the contact angle, that is, the more hydrophobic, the greater the decrease in the survival rate, and hence the higher the killing speed.

  10 to 12 show the relationship between the dimensions of the columnar projections 3 and the survival rate of E. coli after 24 hours. The relationship of the dimension made into evaluation object in FIG. 9 is shown. The distance between the centers of two adjacent columnar protrusions 3 was set to three patterns (200 nm, 500 nm, 1000 nm).

As shown in FIGS. 2 (a) to 2 (f), when the distance between the centers is changed, the height and the diameter of the pillars 3 are also changed. It has become. The relationship between each is as follows.
Center distance S: 200 nm, height H: about 250 nm, diameter D: about 120 nm
Center distance S: 500 nm, height H: about 500 nm, diameter D: about 270 nm
Center distance S: 1000 nm, height H: about 300 nm, diameter D: about 510 nm

  The test piece was made of silicon. In addition, since the surface of the test piece is covered with an oxide film, it is a hydrophilic condition. For this reason, the test was conducted under hydrophilic conditions, which is the more severe condition (one in which the bacteria is less likely to be killed than the hydrophobic condition) from the results described above. The criterion for the antimicrobial property was less than 1%, which is the general standard, the survival rate (viable rate).

  FIG. 10 shows the relationship between the gap (Gap) G between the side surfaces of two adjacent columnar protrusions 3 and 3 and the survival rate (viable rate of E. coli) in each pattern. As a result, it can be seen that in each pattern, the antibacterial power is rapidly increased when the gap G is 200 nm or less. Although the lower limit value of the gap G is not specified in the test, 20 nm is a lower limit value in relation to the size of the flagella of the microorganism which enters the gap between two adjacent columnar protrusions 3 as described above. Conceivable.

  FIG. 11 shows the relationship between the height H of the columnar projections 3 and the survival rate (viable cell rate) of E. coli in each pattern. As a result, it can be seen that the center-to-center distance around 500 nm is the threshold.

  FIG. 12 shows the relationship between the aspect ratio (Aspect ratio) of columnar projections 3 and the survival rate (viable rate) of E. coli in each pattern. As a result, it is understood that when the center-to-center distance is 500 nm or less and the aspect ratio exceeds 1, the antibacterial power is rapidly increased.

  From these results, in the antibacterial material 1 of the present embodiment, it is a basic condition that the distance between the centers of two adjacent columnar projections 3 and 3 is 500 nm or less, and further, two adjacent columnar projections The condition for exhibiting the antibacterial property is that the gap between the side surfaces of 3 and 3 is 20 nm or more and 200 nm or less, or the aspect ratio of the longitudinal sectional shape passing through the center of each columnar protrusion 3 is 1 or more. I found that.

  As mentioned above, from the test result shown in FIGS. 10-12, it has confirmed that antimicrobial property was exhibited on hydrophilic condition. Therefore, it can be inferred that the antibacterial property is exhibited more strongly under hydrophobic conditions.

As mentioned above, the antimicrobial material 1 of this embodiment exhibits the antimicrobial property with respect to the microorganisms (especially bacteria) contained in a liquid. The antibacterial material 1 is characterized by exerting the antibacterial property not by a chemical action but by an action caused by the columnar protrusion 3 which is a physical structure. For this reason, since the antibacterial property does not decrease with the lapse of time unless the action is reduced by the abrasion or defect of the columnar projections 3, the very excellent antibacterial material 1 having a sustained effect is obtained. be able to.

Second Embodiment
Next, as a result of continuing the research after the inventor of the present application obtained the knowledge according to the first embodiment, new (expansive) knowledge was obtained, and therefore, the second embodiment will be described below. In addition, about the matter which overlaps with 1st Embodiment, except for a thing required for explanation, it does not repeat below.

  The data accumulated with the continuation of the research are summarized in FIGS. 13 (a) to 13 (d) for each distance between centers (200 nm, 500 nm, 1000 nm, 2000 nm) of two adjacent columnar protrusions 3 and 3. FIG. As a result, the center-to-center distance exceeding 500 nm, specifically 1000 nm or 2000 nm, which is outside the knowledge of the center-to-center distance according to the first embodiment (500 nm or less is a condition for exhibiting antimicrobial properties) Was found to be exerted.

The inventor has analyzed the conditions for exhibiting the antimicrobial property by focusing on the aspect ratio of the columnar projections 3. The analysis method is, for example, focusing on the portion where the viable cell rate is largely changed in FIG. 13 (d), and as shown in FIG.
Log [y] = Ax + B (y: viable rate (%), x: aspect ratio)
It approximated by the linear line (log [y] =-3.9917x + 2.4968) represented by the approximation formula of. Then, in FIG. 14, x was derived at which the first-order straight line intersects with the horizontal line of 1% of the viable cell rate (log [y] = log (1) = 0). As a result,
x =-(B / A)
I got Further, in FIG. 14, x at which the first-order straight line intersects a horizontal line of a viable rate of 0.1% (log [y] = log (0.1) =-1) having a higher antibacterial rate was similarly calculated. As a result,
x =-((1 + B) / A)
I got Thus, the aspect ratio (x) which exhibits antimicrobial can be calculated by the center-to-center distance between the two columnar protrusions 3 and 3.

Next, the condition showing the antibacterial is fitted. In FIG. 15, the exponential function
y = Cexp (Dx)
In the line with a viable cell rate of 1% (approximate expression of round point in the figure / curved portion of thick line), C = 1.80 and D = −8.3 × 10 ⁻⁴ . Further, in the line with a viable cell rate of 0.1% (approximate expression of square point in the figure / line of thin dashed-dotted line), C = 2.29 and D = -8.2 × 10 ^-4 . For a line with a viable cell rate of 1%, for example, the aspect ratio is 1.66 at a center-to-center distance of 100 nm, and 1.52 at a center-to-center distance of 200 nm.

As described above, each columnar protrusion 3 in the antibacterial material of the present embodiment has a shape represented by the following relational expression, assuming that the viable cell rate is 1%.

Asp 1.8 1.80 exp (-0.00083 p)

Asp: Aspect ratio of vertical cross section passing through the center of each columnar projection 3
p ... Center-to-center distance between two adjacent columnar projections 3

Third Embodiment
Furthermore, in addition to the second embodiment, new findings obtained by continuation of the research by the inventor of the present application will be described below as a third embodiment. In addition, about the matter which overlaps with 1st Embodiment and 2nd Embodiment, except for a thing required for explanation, it does not repeat below.

  The adhesion of E. coli to nanostructures was studied using a quartz oscillator (QCM method). Nanostructures were fabricated on the electrode surface of the quartz oscillator. The columnar projections 3 were cylindrical, had a diameter of 280 nm, a height of 400 nm, and the distance between the centers of two adjacent columnar projections 3 was 500 nm. In addition, the contact angle of water is 80.5 ° (no surface treatment), 128.6 ° (hydrophobic surface treatment with methyl group), 26.0 ° (hydrophilic surface treatment with hydroxyl group) by surface treatment. Columnar projections 3 were formed. In addition, as bacteria used for the experiment, E. coli with flagellum (wild type / motility) and E. coli without flagellum (non-motility) prepared by genetic recombination were prepared. Then, the structure of the surface to be attached with respect to the electrode of the quartz oscillator, or the contact angle, and the ease of attachment due to the characteristics of the attaching side bacteria were evaluated.

  The result of the said experiment is shown to Fig.16 (a)-(c). The fact that the resonance shift (Resistance shift) gradually increases with time in each graph means that the change in viscoelasticity becomes large, which indicates that bacteria may be attached. As shown in the graph of FIG. 16 (a), the presence of nanostructures results in more bacterial adhesion. In addition, as shown in the graph of FIG. 16 (b), the larger the contact angle (hydrophobic), the more the bacteria adheres. Further, as shown in the graph of FIG. 16C, regarding the bacteria, the bacteria attach in a short time when there are flagella. As for those without flagella, it is presumed that bacteria were attached by sedimentation due to gravity. The difference in the state of the electrode surface of the quartz oscillator depending on whether the surface is hydrophobic or hydrophilic is summarized in FIG. 17 together with a photomicrograph. The photomicrographs show that the contact angle and the number of attached bacteria are correlated.

  As described above, it has been found that the antibacterial action (bactericidal action) depends on the nature of bacteria and the surface state of the antibacterial material 1.

  Here, to the antibacterial material 1 in which the columnar projections 3 having an aspect ratio of 2 and a contact angle of 80 ° are formed, E. coli with flagellum (wild type / motile) and E. coli without flagella (no motile) When supplied and evaluated according to JIS Z 2801, the viable cell rate of E. coli with flagella was 0.038%, while the viable cell rate of E. coli without flagella was 116% (grown) The This result indicates that the bacteria can not be killed unless the bacteria are positively adsorbed on the surface of the columnar projections 3 that are nanostructures. And, it is considered that the flagellum possessed by bacteria plays a role in aggressive bacterial adsorption.

  The presumed antimicrobial (sterilization) mechanism is shown to FIG.18 (a)-(c). First, as shown in FIG. 18A, a surface to which bacteria easily adhere is found and attached. Next, as shown in FIG. 18 (b), the flagella causes rotational movement of bacteria after adhesion. As a result, the bacteria collide with the columnar projections 3 and a small scratch is formed in the cell wall. Eventually, as shown in FIG. 18 (c), the wound is enlarged, and the intracellular fluid is considered to leak and lead to death. In particular, when the surface of the columnar projections 3 is hydrophobic, air is in a state of being introduced between two adjacent columnar projections 3 and 3 and capillary force is generated with the leakage of the intracellular fluid. Therefore, it may have produced a strong bactericidal action.

  Thus, in the present embodiment, in addition to the conditions of the shape surface of the columnar projections 3 represented by the above-mentioned relational expression obtained in the second embodiment, the antibacterial bacteria are gram-negative having an elongated shape and flagella. A condition of a relationship with bacteria is a condition for exerting the antibacterial action that the clearance between the side faces of two adjacent columnar protrusions is smaller than the maximum length excluding the flagella of the target bacteria. Findings were obtained (Figure 19). By the condition of the relationship with the bacteria, it is possible to provide the antibacterial material 1 that exerts the optimum antibacterial effect on target bacteria of different sizes.

  Gram-negative bacteria are bacteria in which the peptidoglycan layer in the cell wall is relatively thin, and examples thereof include E. coli, Pseudomonas aeruginosa, mycoplasma, bacilli and cholera.

  Here, when the gap between the columnar projections 3 and 3 is large, bacteria do not collide unless the height of each columnar projection 3 is large to a certain extent. Conversely, when the gap between the columnar projections 3 and 3 is small, bacteria easily collide with each other. However, if the gap is too small, the flat shape is obtained. For this reason, a certain degree of unevenness is required, which corresponds to the above-mentioned conditions.

As described above, when the second and third embodiments are summarized, the antibacterial property is exhibited by the nano structure in which the gap between the columnar projections 3 is smaller than the size of the bacteria. In addition, when the condition of the shape surface of the columnar projections 3 is a viable cell rate of 1%, the height of the columnar projections 3 divided by the width dimension is taken as an aspect ratio (Asp), and two adjacent columnar projections 3 and 3 Let p be the center distance of each other,

Asp 1.8 1.80 exp (-0.00083 p)

Is a condition represented by In addition, it is important for the antibacterial action that bacteria first adhere to nanostructures positively. The conditions for that are as follows: (1) the surface of the columnar projections 3 is hydrophobic, (2) there are flagella in bacteria, (3) there is mobility in flagella.

  The present invention is not limited to the first to third embodiments, and various modifications can be made without departing from the scope of the present invention.

  For example, although the raw material of the antibacterial material 1 of the said embodiment was silicon, it is not limited to this, Various inorganic materials and organic materials, such as a metal and resin, can be made a raw material. Thus, the antibacterial material 1 can be formed by using various materials as materials.

  Moreover, although it was a metal assist etching method in the said embodiment also about the manufacturing method, it is not limited to this. Also in the case of the metal assist etching method, various objects can be used in addition to the polystyrene beads as in the above embodiment. In addition, it is desirable to use an object capable of forming a self-assembled film. In addition, although the formation of the noble metal thin film is performed by sputtering in the above embodiment, it can be performed by various methods such as evaporation (for example, vacuum evaporation), plating, and the like.

  In addition, although the target microorganism having antibacterial properties is a gram-negative bacterium including E. coli in the above embodiment, the present invention is not limited to this and various microorganisms are targeted.

1 antibacterial material 2 substrate 3 columnar protrusion 2a silicon plate B polystyrene bead F thin film

Claims (9)

Equipped with multiple columnar projections,
Each of the columnar projections is an antibacterial material having a shape represented by the following relational expression.

Asp 1.8 1.80 exp (-0.00083 p)

Asp: Aspect ratio of the longitudinal sectional shape passing through the center of each columnar projection
p ... Center-to-center distance between two adjacent columnar projections   The antibacterial material according to claim 1, wherein the shape of each columnar protrusion is cylindrical.   The antimicrobial material according to claim 1, wherein each columnar protrusion is made of silicon or resin.   The antibacterial material according to any one of claims 1 to 3, wherein at least the surface around the tip of each columnar protrusion has hydrophobicity. Each of the columnar protrusions is made of silicon,
The antimicrobial material according to claim 4, wherein the hydrophobic surface is a removed surface of a silicon oxide film. The plurality of columnar projections include columnar projections on the surface of which molecules having a hydrophobic group are present,
The antimicrobial material according to any one of claims 1 to 5.   The antimicrobial material according to claim 6, wherein the plurality of columnar projections are configured by mixing a columnar projection having a molecule having a hydrophobic group on the surface and a columnar projection having a molecule having a hydrophilic group on the surface. The antibacterial target bacteria are gram-negative bacteria having elongated shapes and flagella,
The antibacterial material according to any one of claims 1 to 7, wherein a gap between side surfaces of two adjacent columnar protrusions is smaller than a maximum length excluding flagella of the target bacteria. It is an antibacterial member used for a portion in contact with liquid,
The antimicrobial member which provided the antimicrobial material in any one of Claims 1-8 so that these columnar protrusions might protrude with respect to the said liquid.