JP5846528B2 - Composite thin film and method for producing the same - Google Patents

Description

  The present invention relates to a bioactive hydroxyapatite (HAP: hereinafter simply referred to as “HAP” if necessary) nanocrystal and nanocomposite thin film comprising titanium oxide having excellent biocompatibility and production thereof Regarding the method.

  Titanium metal and titanium alloys are widely used as prosthetic devices for tooth / joint replacement, dentistry or orthopedic illness or reconstruction of damaged teeth and bones. This is because titanium alloys have excellent mechanical properties at sites where good biocompatibility and high strength are required (see Non-Patent Document 1).

  However, when the titanium alloy is introduced into the bone, there is a problem that the implant material is separated from the bone by fibrous tissue or other reaction (see Non-Patent Document 2). In order to solve the problems related to the bonding with bone in such an implant material, surface modification for obtaining a bioactive surface has been studied (see Non-Patent Document 3).

The most commonly used solution to obtain better osseointegration is like hydroxyapatite (HAP; Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , P _{63 / m} ), such as by plasma spraying It is to coat bioactive ceramics. This is because HAP is an inorganic main component of human bones and has a crystal structure similar to that of natural bones and minerals of teeth (see Non-Patent Document 4).
Although HAP is biologically advantageous, the HAP coating obtained by plasma spray has poor adhesion to a titanium metal substrate, non-uniformity of the film, and a fairly thick film of 50 μm to completely cover the implant surface. There is also a problem that it is necessary (see Non-Patent Document 5).

The coated HAP layer is brittle and easily peels away from the implant, causing degradation in vivo. In the HAP-coated metal implant, the main destruction is caused by the inside of the coating (see Non-Patent Document 6).
In order to overcome these facts, the preparation of HAP layers has been investigated by various methods. Sputtering method (refer to Patent Document 1), coating method using electrostatic interaction (refer to Patent Document 2), powder mixing with substrate components (refer to Patent Document 3), applying raw material slurry and forming thin film by hydrothermal reaction A obtaining method (see Patent Document 4) is disclosed.

  In addition, thin film formation by electrodeposition (see Patent Document 5), a method of forming a precursor film by a thermal spray method and converting it into HAP (see Patent Document 6), and by applying and baking a colloidal dispersion solution for precursor generation A film forming method (see Patent Document 7), a method of forming a biocompatible film in which chitosan is introduced into the film by electrodeposition (see Patent Document 8), a film forming method by a sol-gel method (see Patent Document 9), A multilayer coating manufacturing method using CVD or PVD (see Patent Document 10) is disclosed.

Furthermore, apatite-like calcium phosphate complex synthesis method using biomimetic method (see Patent Document 11), HAP coating method by coating HAP after coating titanium (see Patent Document 12), raw material supersaturation A method of obtaining a HAP thin film by immersion in an aqueous solution (see Patent Document 13) is disclosed.
However, these studies are all about how well the HAP film is produced and the adhesion of the substrate is improved, and there are hardly any examples other than those trying to introduce chitosan to introduce new ideas into the film itself.

Uchida, M, et al., Advanced Materials, 16 (13) (2004) 1071-1074. Ratner BD, et al., Biomaterials science.San Diego, CA: Academic Press; (1996). Gomez-Vega JM, et al., Adv. Mater., 12 (12) (2000) 894-898, Lee B-H, et al. J. Biomed. Mater. Res. 69A (2004) 279-285. Jack JJMD, et al., Adv. Mater. 5 (3) (2003) 313-316, Wang H, et al., Biomaterials 27 (23) (2006) 4192-4203. Linhart W, et al., UNFALLCHIRURG; 107 (2) (2004) 154-157, Klein Cpat, et al., Biomaterials 15 (2) (1994) 146-150. Lee B-H, et al., J. Biomed. Mater. Res. 61A (2002) 466-473, Gross KA, et al., J. Am. Ceram. Soc. 81 (1) (1998) 106-112.

JP-A-2-1286 JP 2005-279219 A Japanese Patent No. 2975290 JP-A-4-144984 Japanese Patent Laid-Open No. 10-0102288 JP-A-63-93851 Japanese Patent No. 2692216 USA2006 / 0099456 USA2005 / 0255239 USA2002 / 0016635 USA2003 / 0170379 USA2003 / 0108658 EP0389713

As described above, the HAP film has major problems in the strength of the thin film itself and the adhesion between the thin film and the substrate, and various studies have been made on this improvement. In the present invention, in order to overcome these problems, a nanocomposite thin film composed of nanocrystals of HAP having excellent bioactivity and titanium oxide having excellent biocompatibility on a pure titanium substrate or a titanium alloy substrate. The technology to create is provided.
As a result, the biocompatibility of HAP and the biocompatibility of titanium oxide are compatible, and titanium oxide can be used well with titanium-based substrates, so that it is possible to form a film with excellent substrate adhesion. It is.

In order to create a nanocomposite thin film composed of bioactive HAP nanocrystals and titanium oxide with excellent biocompatibility, a technique called co-sputtering (a thin film formed by simultaneously sputtering titanium oxide and HAP components) To achieve chemical uniformity and microstructural uniformity.
The composition, morphology, and surface state of the HAP / TiO ₂ composite are controlled by examining the effects of various preparation conditions.

  In the present invention, titanium oxide and hydroxyapatite are co-sputtered in an argon atmosphere of 1 to 100 mTorr to form a precursor thin film for a composite material in which hydroxyapatite is dispersed in a titanium oxide matrix. The body thin film is annealed at 400 to 1000 ° C. to produce a composite material thin film in which hydroxyapatite is dispersed in a titanium oxide matrix that forms crystalline hydroxyapatite in the titanium oxide matrix.

If the annealing temperature is less than 400 ° C, the production efficiency is low, and if the annealing temperature is higher than 1000 ° C, the dispersion state is likely to be non-uniform and another phase is likely to be formed. This is a desirable condition. However, it can also be manufactured outside of these conditions. The present invention includes these.
In particular, a thin film in which crystalline hydroxyapatite and calcium oxide coexist in a titanium oxide matrix in a pressure region of 4 to 50 mTorr is a more effective range for achieving the present invention.

  Experimental results show that the argon pressure during sputtering is important. This is presumably because HAP has a hydroxyl group and a phosphate group, and these functional groups cannot be incorporated into the thin film unless optimum conditions are selected. In addition, by using the simultaneous sputtering method, the two components can be mixed uniformly, so that structural uniformity can be obtained and cracks and the like are hardly generated.

  In order to obtain crystalline HAP, heat treatment is required, but this generates a structure in which HAP is firmly incorporated in the titanium oxide matrix. The titanium oxide phase provides adhesion to the titanium-based alloy of the substrate, and the dispersed HAP contributes to ensuring biocompatibility, promotes bone cell growth from this point, and makes it easier for the implant to be taken into the living body. It has.

The atomic ratio of Ca to P (Ca / P) in the composite thin film in which hydroxyapatite is dispersed in a titanium oxide matrix varies depending on the argon atmosphere pressure of 1 to 100 mTorr during simultaneous sputtering. By adjusting the pressure, the atomic ratio Ca / P of Ca and P can be adjusted to 1.37 to 1.97. The optimal condition is sputtering at 20 mTorr argon pressure.

By the heat treatment, a composite material in which crystalline hydroxyapatite having an average particle diameter of 10 nm to 1000 nm is dispersed can be obtained. Usually, a composite material in which crystalline hydroxyapatite having an average particle diameter of 30 nm to 100 nm is dispersed is obtained.
This hydroxyapatite average particle diameter is a particle diameter obtained under the heat treatment conditions of the present invention, and this is a suitable particle diameter for ensuring the biocompatibility of dispersed HAP. However, it is to be understood that this particle size value is not an absolute requirement.
Further, in the simultaneous sputtering, by changing the sputtering amount of titanium oxide and hydroxyapatite, a film is formed so that the amount of crystalline hydroxyapatite in titanium oxide has a composition (ratio) inclined in the thickness direction of the thin film. It is possible.

In order to join titanium or titanium alloy, which is lightweight, high in strength and high in biocompatibility, and bones in the living body, it is considered that surface coating of a substance having high biocompatibility such as HAP is important. The surface adhesion is very weak and easily peeled off due to reaction or cracks.
In the present invention, by using the HAP / titanium oxide composite (composite) thin film, the mechanical strength of the surface coating layer can be improved without sacrificing biocompatibility and biocompatibility. It is an effective method that makes it possible to create thin films that can be adapted to a wide range of applications such as transplantation and tooth replacement.

It is a scanning electron micrograph of the titanium oxide / HAP precursor nanocomposite material produced by the co-sputtering method, and is the result of examining the sputtering pressure dependency. (A) shows a photograph of sputtering at 4 mTorr, (b) at 10 mTorr, and (c) at 20 mTorr. FIG. 2 is a scanning electron micrograph of a titanium oxide / HAP nanocomposite obtained by heat-treating the sample of FIG. 1 at 600 ° C. for 1 hour in nitrogen, where (a) is 4 mTorr, (b) is 10 mTorr, and (c) 20. A photograph sputtered with mTorr is shown. It is a figure which shows the pressure dependence of surface Ca / P atomic ratio measured by the X ray photoelectron spectroscopy of the obtained thin film. It is a figure which shows the chemical state change of the surface oxygen measured by the X ray photoelectron spectroscopy, (a) of the upper stage shows before heat processing, (b) of the lower stage shows after heat processing. (A) is an X-ray diffraction pattern of a titanium substrate. (B) is an X-ray diffraction pattern of a titanium oxide / HAP nanocomposite obtained by heat-treating a film obtained by sputtering at 4 mTorr and (c) 20 mTorr in nitrogen at 600 ° C. for 1 hour. It is a scanning electron microscope image after culturing MC3T3-E1 cells on the sample surface for 2 hours, (a) a titanium substrate before film deposition, (b) sputter deposition at 4 mTorr, and (c) at 20 mTorr. The cells attached on the substrate after heat treatment are shown. (D) shows the number density of attached MC3T3-E1 cells.

The features of the present invention will be specifically described below with reference to the drawings. In addition, the following description is for making an understanding of this invention easy, and is not restrict | limited to this. That is, modifications, embodiments, and other examples based on the technical idea of the present invention are included in the present invention.
Preparation of precursor thin film by optimizing argon gas pressure using co-sputtering method and heat treatment in nitrogen at 600 ° C to produce nanocomposite dispersed in titanium oxide with HAP dispersed I was able to. The HAP phase was about Ca / P = 1.67.

(Example)
A pure titanium plate (CP-Ti; ASTM F136, manufactured by Daido Steel) was cut out from a pure titanium rod (10 mmΦ) to a thickness of 2 mm. As a pretreatment, this was polished with # 240, # 600, # 800 and # 1200 paper files, then ultrasonically cleaned in acetone for 30 minutes, further washed in pure water and dried to be used as a substrate.
A HAP / TiO ₂ nanocomposite thin film was obtained on the substrate by a simultaneous sputtering method using a magnetron sputtering apparatus. Hydroxyapatite (CELLYARD ^™, manufactured by PENTAX, 13 mmφ, thickness 2 mm, 13 pieces arranged in a ring) pellets were placed on a 100 mm diameter titanium oxide target and sputtered simultaneously to obtain a thin film.

(Observation of sputtered film: precursor composite material)
Sputtering was performed at 50 W in argon for 60 minutes without substrate heating. FIG. 1 shows a scanning electron micrograph of a titanium oxide / HAP precursor nanocomposite prepared by a co-sputtering method with the sputtering pressure varied in the range of 4 to 20 mTorr. That is, the influence (sputter pressure dependence) on the form of the composite material composed of titanium oxide / HAP precursor was investigated.
The photo (a) in FIG. 1 is 4 mTorr, the photo (b) is 10 mTorr, and the photo (c) is 20 mTorr. In all the samples, a linear trace was observed, which was a processing trace when a titanium plate as a substrate was cut out. No significant tissue changes were observed in the thin film itself.

(Precursor annealing)
FIG. 2 shows the surface morphology after annealing the thin film obtained in FIG. 1 at 600 ° C. for 60 minutes in nitrogen. 1 is a scanning electron micrograph of a titanium oxide / HAP nanocomposite obtained by heat-treating the sample of FIG. 1 at 600 ° C. for 1 hour in nitrogen, and FIG. 2A is a case where sputtering is performed at an argon pressure of 4 mTorr. (B) shows the case where sputtering is performed at an argon pressure of 10 mTorr, and (c) shows the case where sputtering is performed at an argon pressure of 20 mTorr.
In the film prepared at 4 mTorr, small square particles having an average of about 30 nm and large particles slightly larger than that were observed. The former was presumed to be calcium oxide microcrystals. The latter is presumed to be a component containing crystalline HAP.

Furthermore, the film produced at 20 mTorr with increased pressure was found to have a structure in which larger grains of about 100 nm were found and crystalline HAP (average grain size 120 nm) was precipitated in the titanium oxide matrix.
FIG. 3 shows the atomic ratio of Ca / P in the obtained film. The higher the argon pressure, the closer to HAP 1.67, and the Ca / P atomic ratio at 20 mTorr was about 1.67. Value.
At low pressures, such as less than 1 mTorr, phosphate ions and hydroxide ions were released into the atmosphere by sputtering and could not be collected in the film, which was considered to indicate a large compositional deviation.

(Chemical state of oxygen in thin film)
FIG. 4 shows the result of measuring the chemical state of oxygen in the thin film by X-ray photoelectron spectroscopy. A peak was observed at a peak position closer to hydroxyapatite as the film was obtained at a higher pressure such as 20 mTorr. This indicates that a pressure of around 20 mTorr is optimal for producing a crystalline hydroxyapatite-dispersed titanium oxide composite film that hardly contains calcium oxide microcrystals.

  When the argon pressure during sputtering is lower than 10 mTorr, the amount of crystalline hydroxyapatite present after annealing tends to decrease and calcium oxide increases. However, if crystalline hydroxyapatite remains, the effect of biocompatibility can exist, and therefore, simultaneous sputtering in an argon atmosphere of 1 to 100 mTorr is also possible.

A thin film in which crystalline hydroxyapatite and calcium oxide coexist in a titanium oxide matrix and dispersed in a pressure range of 4 mTorr to 50 mTorr is a more effective range for achieving the present invention.
The present invention clarifies this meaning, and it should be understood that the present invention includes these. Sputtering at a pressure higher than 20 mTorr is also possible, but it can be said that the optimum pressure condition is preferably 50 mTorr or less because the thin film formation rate is reduced.

(X-ray diffraction of substrate and film)
This result is supported by the result of X-ray diffraction shown in FIG. (A) of FIG. 5 is an X-ray diffraction of a titanium substrate, (b) is 4 mTorr, (c) is a film obtained by sputtering at 20 mTorr at 600 ° C. for 1 hour in nitrogen. 2 is an X-ray diffraction pattern of a heat-treated titanium oxide / HAP nanocomposite.
T, A, R, and C in the figure correspond to peaks of titanium, apatite, rutile phase titanium oxide, and calcium oxide, respectively.

In FIG. 5A, which is an X-ray diffraction of a titanium substrate, a signal only from titanium was obtained. In (b), which is an X-ray diffraction from a thin film obtained at 4 mTorr, peaks from rutile phase titanium oxide and calcium oxide are observed, and the amount of crystalline hydroxyapatite is considered to be small.
On the other hand, (c), which is an X-ray diffraction from a thin film obtained at 20 mTorr, shows that rutile-phase titanium oxide and crystalline hydroxyapatite are observed, and crystalline hydroxyapatite is certainly produced in the thin film by this production method. I was able to confirm.

(Scanning electron micrograph of attached cells by cell culture)
Further, FIG. 6 shows the results of cell culture (2 hours MC3T3-E1 cells) on such a substrate, and the attached cells were observed with a scanning electron microscope.
A cell with a round or spindle shape attached. What looks like a streak is a polishing mark when the titanium substrate is polished. (A) shows a titanium substrate before film deposition, (b) shows 4 mTorr, and (c) shows cells adhering to the substrate heat-treated after sputter deposition at 20 mTorr.

(Number density of cultured cells)
FIG. 6 (d) shows the number density of attached MC3T3-E1 cells. As is clear from FIG. 6, an increase from about 1 mTorr is recognized on the thin film substrate obtained by this method, particularly on the film obtained under the conditions where apatite is generated, compared with the case where no film is present, At about 4 mTorr, a considerable amount of cell attachment is observed. In particular, at 20 mTorr, it can be seen that more than twice as many cells are attached as compared to the case without a membrane, and clearly shows high biocompatibility when implanted in a living body.
This trend confirms an increase in cell attachment even at 100 mTorr. However, about 50 mTorr is considered good from the viewpoint of thin film formation efficiency.

As described above, the present invention provides a technique for producing a nanocomposite thin film comprising a nanocrystal of HAP having excellent bioactivity and titanium oxide having excellent biocompatibility on a pure titanium substrate or a titanium alloy substrate. Is.
As a result, the biocompatibility of HAP and the biocompatibility of titanium oxide are compatible, and titanium oxide can be used well with titanium-based substrates, so that it is possible to form a film with excellent substrate adhesion. It is. It is extremely useful as a prosthetic tool for the replacement of teeth and joints, and the reconstruction of damaged or damaged teeth and bones in dentistry or orthopedics.

Claims (6)

Titanium oxide and hydroxyapatite are sputtered simultaneously in an argon atmosphere of 1 to 100 mTorr. During sputtering, the sputtering amount of titanium oxide and hydroxyapatite is changed, and the crystalline hydroxyapatite in titanium oxide is inclined in the thickness direction of the thin film. A method for producing a composite material thin film that is a precursor of a composite material in which hydroxyapatite is dispersed in a titanium oxide matrix having the composition described above. A composite material in which hydroxyapatite is dispersed in a titanium oxide matrix in which titanium oxide and hydroxyapatite are simultaneously sputtered in an argon atmosphere of 1 to 100 mTorr, and the crystalline hydroxyapatite in titanium oxide is inclined in the thickness direction of the thin film The precursor thin film was formed, and the precursor thin film was annealed at 400 to 1000 ° C. to form crystalline hydroxyapatite in the titanium oxide matrix. Hydroxyapatite was dispersed in the titanium oxide matrix. A method for producing a composite thin film. The method for producing a composite thin film according to claim 2, wherein the atomic ratio (Ca / P) of Ca and P in the film is 1.37 to 1.97. The method for producing a composite material thin film according to claim 2 or 3, wherein the composite material is a composite material in which crystalline hydroxyapatite having an average particle size of 10 nm to 1000 nm is dispersed. 4. The method for producing a composite material thin film according to claim 2, wherein the composite material is a composite material in which crystalline hydroxyapatite having an average particle size of 30 nm to 100 nm is dispersed. 6. A composite precursor thin film in which hydroxyapatite is dispersed in a titanium oxide matrix is formed by co-sputtering titanium oxide and hydroxyapatite in an argon atmosphere of 4 to 50 mTorr. A method for producing a composite thin film according to claim 1.