An in-situ ring-opening polymerization reinforcement method for osteo-dentin cultural relics

Abstract

The present invention discloses an in-situ ring-opening polymerization reinforcement method for bone and dentin cultural relics, which comprises the following steps: (1) After washing the bone and dentin cultural relics, they are soaked in an aqueous solution of 0.5% tetrabutylammonium hydroxide or tetramethylammonium hydroxide, with a solid-liquid ratio of 1:(4-10). After treatment, they are soaked in deionized water to wash away the unreacted reagents; (2) The pretreated bone and dentin cultural relics are soaked in a 3-7 wt% N-carboxy cyclic anhydride solution for 0.5-2 hours. After treatment, the reinforcement is completed after the solvent volatilizes. The present invention solves the disadvantages of high solution viscosity and poor permeability existing in the direct use of polymer materials. Moreover, polyamino acids have a chemical structure similar to collagen, are well compatible with bone and dentin cultural relics, effectively make up for the loss of collagen in bone and dentin cultural relics, and improve the mechanical strength of cultural relics.

Description

Technical Field

[0001] The present invention relates to the technical field of cultural relics protection, and more particularly, to an in-situ ring-opening polymerization reinforcement method for bone and dentin cultural relics. Background Art

[0002] Bone and dentin cultural relics are common types of cultural relics unearthed from archaeological sites, including bones, teeth and their artifacts of various animals. The chemical composition of such cultural relics mainly includes hydroxyapatite and collagen. However, during the long-term burial underground, a large amount of collagen degrades, and the composite structure is damaged, resulting in low strength of bone and dentin cultural relics, and being prone to diseases such as fracture and pulverization, endangering the safety of cultural relics. Therefore, unearthed bone and dentin cultural relics often need to be reinforced to ensure the safety of cultural relics.

[0003] Under the existing technical conditions, the reinforcement methods for bone and dentin cultural relics are mainly divided into two categories. One category uses inorganic reinforcement materials represented by hydroxyapatite for reinforcement. However, very little hydroxyapatite is lost in bone and dentin cultural relics, and the degradation and loss of collagen cause such cultural relics to be prone to brittle fracture and pulverization. Further supplementing inorganic materials cannot make up for the loss of collagen, and the characteristics of the organic-inorganic composite material of bone cultural relics cannot be restored after reinforcement. Another reinforcement method uses organic polymer reinforcement materials represented by various acrylic resins and collagen hydrolysates. However, the reinforcement liquids of such methods have high viscosity, poor permeability, and limited reinforcement depth.

[0004] Therefore, there is an urgent need for a new reinforcement method for bone and dentin cultural relics, which can effectively make up for the loss of collagen in bone and dentin cultural relics and improve the mechanical strength of cultural relics. Summary of the Invention

[0005] The purpose of the present invention is to provide an in-situ ring-opening polymerization reinforcement method for bone and dentin cultural relics. This method uses N-carboxy anhydride (NCA) as a small molecule monomer, which penetrates into the interior of bone and dentin cultural relics and then undergoes ring-opening polymerization to in-situ form a polyamino acid reinforcement material. This method solves the disadvantages of high solution viscosity and poor permeability existing in the direct use of high molecular materials, and polyamino acids have a chemical structure similar to collagen, are well compatible with bone and dentin cultural relics, effectively make up for the loss of collagen in bone and dentin cultural relics, and improve the mechanical strength of cultural relics.

[0006] An in-situ ring-opening polymerization reinforcement method for bone and dentin cultural relics includes the following steps:

[0007] (1) Pretreatment of bone and dentin cultural relics

[0008] After washing the bone and dentin cultural relics, immerse them in an aqueous solution of 0.5% tetrabutylammonium hydroxide or tetramethylammonium hydroxide, with a solid-liquid ratio of 1:(4 - 10) and completely submerge the cultural relics. After treatment for 1 hour, immerse them in deionized water to wash away the unreacted reagents.

[0009] The purpose of this step is to convert the carboxyl groups in the residual proteins of the osteodentin cultural relics into corresponding ammonium salts for subsequent initiation of the polymerization reaction.

[0010] (2) In-situ polymerization

[0011] Immerse the pretreated osteodentin cultural relics in an N-carboxy cyclic anhydride solution with a concentration of 3-7 wt%, for an immersion time of 0.5-2 hours. After treatment, wait for the solvent to volatilize to complete the reinforcement.

[0012] As a preferred embodiment, in step (1), the concentration of the aqueous solution of tetrabutylammonium hydroxide or tetramethylammonium hydroxide is 0.5 wt%.

[0013] As a preferred embodiment, the solid-liquid ratio in step (1) is 1:5.

[0014] As a preferred embodiment, in step (2), the N-carboxy cyclic anhydrides include L-alanine-N-carboxy cyclic anhydride, glycine-N-carboxy cyclic anhydride, and glutamate-5-benzyl ester-N-carboxy cyclic anhydride, preferably L-alanine-N-carboxy cyclic anhydride.

[0015] As a preferred embodiment, in step (2), the solvent is tetrahydrofuran (THF), N,N-dimethylformamide (DMF), dichloromethane (DCM), or ethyl acetate (EA), preferably N,N-dimethylformamide.

[0016] As a preferred embodiment, in step (2), the concentration of the N-carboxy cyclic anhydride solution is 5 wt%.

[0017] As a preferred embodiment, repeat the operation of step (2) until the reinforcement requirements are met.

[0018] The beneficial effects produced by the present invention are as follows:

[0019] (1) The present invention uses an organic polymer reinforcement material to in-situ synthesize polyamino acids similar to collagen in the osteodentin cultural relics, compensating for the degradation and loss of collagen in such cultural relics and improving their strength and hardness.

[0020] (2) The present invention adopts an in-situ polymerization reinforcement method, which is not adversely interfered by the high molecular weight on the viscosity and permeability of the polymer solution, has a deep reinforcement depth and good uniformity; the polymerized polyamino acid material similar to collagen has good compatibility with the osteodentin cultural relics. Description of the drawings

[0021] Figure 1 Schematic diagram of the weight gain rate curve of the bone cultural relic sample after polymerization with different monomers in Example 1;

[0022] Figure 2 Infrared spectrogram of the bone cultural relic sample after the polymerization treatment in Example 1;

[0023] Figure 3 Schematic diagram of the absorption characteristics at the amide I band of the infrared spectrum of the bone cultural relic sample after the polymerization treatment in Example 1;

[0024] Figure 4 Schematic diagram of the absorption characteristics at the amide III band of the infrared spectrum of the bone cultural relic sample after the polymerization treatment in Example 1;

[0025] Figure 5 Schematic diagram of the weight gain rate of the bone cultural relic sample after polymerization under different solvent conditions in Example 2;

[0026] Figure 6 Schematic diagram of the elastic modulus results of the samples in Example 3;

[0027] Figure 7 Schematic diagram of the microhardness results of the samples in Example 3. Detailed implementation manners

[0028] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0029] The features and performance of the present invention will be further described in detail below in conjunction with the embodiments.

[0030] Example 1

[0031] The reinforcement method of this example is as follows:

[0032] (1) Pretreatment of bone and dentin cultural relics

[0033] After washing the bone and dentin cultural relics, soak them in an aqueous solution of tetrabutylammonium hydroxide with a concentration of 0.5 wt%, the solid-liquid ratio is 1:5, and after treatment, soak them in deionized water to wash away the unreacted reagents.

[0034] (2) In-situ polymerization

[0035] Using DMF as the solvent, soak the pretreated bone and dentin cultural relics in different monomer solutions with a concentration of 5 wt% for 2 hours. After polymerization with different monomers, the weight gain rate curves of the bone cultural relic samples (cow bones) with degraded collagen are as Figure 1As shown, the processing results indicate that the weight gain rate tends to stabilize after 1 h of polymerization treatment. After 2 h of polymerization of the four monomers or monomer combinations (L-alanine-N-carboxyanhydride, glycine-N-carboxyanhydride, glutamate-5-benzyl ester-N-carboxyanhydride, and the mixed monomer of L-alanine-N-carboxyanhydride and glycine-N-carboxyanhydride in a 1:1 molar ratio), the weight gain rates are 3.5%, 3.4%, 2.7%, and 2.4%, respectively. Taking L-alanine-N-carboxyanhydride as an example of the monomer, after repeating the polymerization treatment step once, the weight gain rate is 4.1%, which can further increase the weight gain rate compared with the single treatment.

[0036] As Figure 2 shown, after the polymerization treatment, obvious amide absorption peaks are shown in the infrared spectrum of the bone cultural relics sample, including the amide I band at 1700 - 1600 cm -1 , the amide II band near 1550 cm -1 , and the amide III band at 1350 - 1200 cm -1 , indicating that the polymerization reaction occurs as scheduled and polyamino acids are generated. Among them, after polymerization of different monomers, the amide I band and the amide III band show different absorption characteristics, as specifically Figure 3 , Figure 4 shown. Figure 3 Among them, near 1684 cm -1 belongs to the β-turn structure, near 1654 cm -1 belongs to the α-helix structure, near 1649 cm -1 belongs to the random coil, and near 1635, 1627 cm -1 belongs to the β-sheet. Figure 4 Among them, near 1331, 1308 cm -1 belongs to the α-helix structure, near 1272 cm -1 belongs to the β-turn structure, near 1259 cm -1 belongs to the random coil, and near 1235 cm -1 belongs to the β-sheet structure. It can be seen from Figure 3 , Figure 4 that by using different monomers, the secondary structure of the generated polyamino acids can be adjusted. Among them, polyalanine is mainly α-helix, polyglycine and polyglycylalanine are mainly β-sheet, and poly-5-benzyl glutamate is mainly random coil and α-helix.

[0037] Example 2

[0038] The basic steps of this example are the same as those of Example 1, except that glycine-N-carboxyanhydride is used as the monomer and different solvents are used for the polymerization step. The weight gain rate results are as Figure 5The results showed that under the solvent conditions of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF), the samples had a higher weight gain rate, and were suitable treatment solvents.

[0039] Example 3

[0040] The basic steps of this implementation are the same as those of Example 1. Single reinforcement treatments were carried out on bone cultural relic samples using polyglycine, polyalanine, polyglycylalanine, and poly(γ-benzyl L-glutamate) as polymerization monomers respectively, and double reinforcement treatment was carried out on bone cultural relic samples using polyalanine as the polymerization monomer.

[0041] The reinforcement effect of the bone cultural relic samples was measured by a KLA G200 nanoindentation instrument. The test used a Berkovich tetrahedral indenter with a tip roundness of less than 20 nm, an indentation depth of 1.0 μm, a load resolution of 50 nN, and a displacement resolution of less than 0.01 nm. The continuous stiffness measurement method (CSM) was used to measure the hardness and elastic modulus that continuously changed with the indentation depth. The average value of three test results was taken under each treatment condition. As Figure 6 、 Figure 7 shown, compared with the un-reinforced bone cultural relics, the elastic modulus and microhardness of the reinforced bone cultural relic samples were significantly improved. Among them, during single treatment, the reinforcement effect of poly(γ-benzyl L-glutamate) (PBG) was the best, and the elastic modulus could be increased to about 6.76 GPa, and the microhardness could be increased to 0.137 GPa. After repeated reinforcement (twice) treatment, the reinforcement effect was significantly better than that of single treatment. After repeated reinforcement with polyalanine (PAla×2), the elastic modulus was increased to about 8.41 GPa, and the microhardness was increased to about 0.16 GPa, approaching the strength of fresh bovine bone.

[0042] The above embodiments are only examples of the preferred embodiments of the present invention, and do not cover all the implementation scopes of the invention. Those of ordinary skill in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention is subject to the scope defined by the claims.

Claims

1. An in-situ ring-opening polymerization reinforcement method for dentin artifacts, characterized in that, It includes the following steps: (1) Pretreatment of bone and dentin cultural relics After washing the bone and dentin cultural relics, immerse them in an aqueous solution of 0.5% tetrabutylammonium hydroxide or tetramethylammonium hydroxide, with a solid-liquid ratio of 1:(4 - 10) and completely submerge the cultural relics. After 1 hour of treatment, immerse them in deionized water to wash away the unreacted reagents; (2) In-situ polymerization Immerse the pretreated bone and dentin cultural relics in a 3 - 7wt% N-carboxy cyclic anhydride solution for 0.5 - 2 hours. After treatment, wait for the solvent to evaporate to complete the reinforcement.

2. A method for in-situ ring-opening polymerization reinforcement of dentin artifacts according to claim 1, characterized in that, In step (1), the concentration of the tetrabutylammonium hydroxide or tetramethylammonium hydroxide aqueous solution is 0.5wt%.

3. A method for in-situ ring-opening polymerization reinforcement of bone and dentin cultural relics according to claim 1, wherein The solid-liquid ratio in step (1) is 1:

5.

4. A method for in-situ ring-opening polymerization reinforcement of bone and dentin cultural relics according to claim 1, characterized in that, In step (2), the N-carboxy cyclic anhydride includes L-alanine-N-carboxy cyclic anhydride, glycine-N-carboxy cyclic anhydride, and glutamate-5-benzyl ester-N-carboxy cyclic anhydride.

5. A method for in-situ ring-opening polymerization reinforcement of bone and dentin cultural relics according to claim 4, characterized in that, In step (2), the N-carboxy cyclic anhydride is L-alanine-N-carboxy cyclic anhydride.

6. A method for in-situ ring-opening polymerization reinforcement of dentin bone cultural relics according to claim 1, characterized in that, In step (2), the solvent is tetrahydrofuran (THF), N,N-dimethylformamide (DMF), dichloromethane (DCM), or ethyl acetate (EA).

7. A method for in-situ ring-opening polymerization reinforcement of osteodentin cultural relics according to claim 6, characterized in that, In step (2), the solvent is N,N-dimethylformamide.

8. A method for in-situ ring-opening polymerization reinforcement of bone and dentin cultural relics according to claim 1, characterized in that In step (2), the concentration of the N-carboxy cyclic anhydride solution is 5wt%.

9. A method for in-situ ring-opening polymerization reinforcement of dentin artifacts according to claim 1, characterized in that, Repeat the operation steps of (2).

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