CN113117157A

CN113117157A - Medical bone screw with biological functionalized surface, preparation method and application thereof

Info

Publication number: CN113117157A
Application number: CN202110375246.7A
Authority: CN
Inventors: 丁建东; 王秀丽; 付烨
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 2021-04-08
Filing date: 2021-04-08
Publication date: 2021-07-16

Abstract

The invention relates to a medical bone screw with a biofunctionalized surface, a preparation method and application thereof, and mainly solves the problems of poor histocompatibility and poor biological sealing performance of the conventional bone fixing screw. Animal experiment results show that compared with unmodified screws, the bone screw subjected to biological functionalization modification has remarkable advantages in weakening tissue inflammatory reaction, promoting neovascularization, enhancing osseointegration and improving biological sealing performance, and is expected to be widely applied to operations such as implanted artificial limbs, bone transplantation, joint fusion, joint fixation, orthopedic surgery and the like as a new generation of implanted medical apparatus.

Description

Medical bone screw with biological functionalized surface, preparation method and application thereof

Technical Field

The invention relates to the technical field of biomedical treatment, in particular to a medical bone screw with a biological functionalized surface, a preparation method and an application thereof.

Background

In the clinical practice of surgery, operations such as bone grafting, joint fusion, joint fixation, and orthopedic surgery are often used for the treatment of diseases such as bone fracture and bone repair, and a fixation method is generally used in the operation. At present, metal fixing screws (stainless steel materials, titanium alloy materials and the like) are mostly adopted for clinical internal fixation of fracture, and the metal fixing screws have high mechanical property and relatively good biocompatibility. However, bone screws, as a transcutaneous device, i.e. a device that connects the external environment to the internal structure of the body by penetrating the skin barrier, suffer from problems with transcutaneous sealing. When a foreign object enters a living body, the living body can adapt to its presence in various ways. Cellular mechanisms are activated and in many cases eventually result in the implant being encapsulated by fibrous tissue. Such fibrous capsule wraps can facilitate permanent retention of a variety of materials, such as tattoo paint, non-absorbable sutures, and artificial orthopedic implants. For percutaneous implants, where the percutaneous portion forms a permanent wound in the skin, disrupting the continuity of the skin, and the encapsulation of the implant penetrating portion by the epidermis eventually results in its extrusion, both of these repair mechanisms are disadvantageous for obtaining a stable percutaneous implant.

For bone fixation screws, their attachment to the skin and the underlying soft tissue is critical and most difficult to achieve. The most common failure modes of the percutaneous implant-skin junction are capsular sac, gross migration, infection, and laceration. Combinations of single or multiple pathological factors may be responsible for these failure modes. These factors may be skin imperfections surgically created around the penetrated foreign implant, epidermal healing properties that prevent the implant-skin interface from forming a proper seal, and mechanical forces that may disrupt the skin sealing interface. Eventually, the percutaneous interface becomes infected and the implant is expelled or forcibly removed.

Capsular sac, gross migration, infection and laceration are as follows:

1) capsular encapsulation (marsupillation): following implantation of the bone fixation screw, basement membrane cells at the edge of the epidermal incision proliferate immediately and migrate toward the implant, whereas a layer of connective tissue at the surface prevents them from migrating over the eschar to contact the implant material. Thus, the basal cells penetrate the tissue, leaving behind a well perfused connective tissue with the predominant inflammatory cell type below it or a less important component of granulation tissue above it. Thus, they never reach the implant surface, but migrate down to the dermis and subcutaneous tissue in a direction parallel to the implant, always leaving less viable tissue above and healthy, viable tissue below. This action continues until the leading edge of the epidermis meets at the bottom of the implant, with the end result that the implant is surrounded by the epidermis, i.e. a pocket is formed.

2) Global migration (migration): to avoid capsular sac formation, many researchers have proposed the use of implants with porous surfaces. The assumption is that a porous surface will allow epidermal cells and dermal components to migrate into the pores of the surface, forming a seal against bacteria and liquids, thus forming a secure fixation of the implant. In order to determine the optimum pore size, researchers have conducted many studies. Winter et al found that connective tissue infiltration only occurred in pores larger than 40 μm, and that only single cells (mainly fibroblasts) migrated into the pores and deposited collagen when the pore size was between 10-40 μm. Daly's study showed that fibroblasts were unable to survive after migrating deep into the pores, apparently due to a lack of nutrients, and the pores eventually filled with cellular debris. When the pore size is larger than 40 μm, connective tissue will soon fill the pores.

von Recum found that epidermal basal cells migrated into dacron velvet implants in rabbits and dogs, penetrating 2mm deep within 10-20d, and similar results were reported in Winter et al. This phenomenon of growth of epidermal basal cells into the pores along with connective tissue is called global migration, and the maturation and further proliferation of epidermal cells within the pores of the implant leads to global migration of the epithelium, which eventually leads to failure of the implant.

3) Infection (Infection): the histological response of smooth or porous implant surfaces is similar when infection occurs. The dermis and underlying tissue in contact with the infected implant forms a thick granular tissue encapsulation which is infiltrated by a large number of acute inflammatory cells, primarily polymorphonuclear granulocytes. Epidermal cells at the wound margin are no longer proliferating and will not grow and adhere to the implant surface. In this case, epidermal sealing never occurs, nor can the inflammatory cells within the capsule effectively cope with the infection, which will eventually lead to extrusion of the implant.

4) Tear (Avulsion): due to the percutaneous penetration, bone fixation screws are subject to mechanical stimuli that are transmitted directly or indirectly through the skin, and in particular when used as a weight bearing site (e.g., artificial lower prosthesis), to mechanical stimuli that are not negligible. It is generally believed that such irritation can produce mechanical interface stresses that result in tissue damage at the bone fixation screw-skin interface, ultimately resulting in failure of the implant.

5) The integration of the above modes: for most cases, failure of a bone fixation screw is often a combination of the above modes. Either capsular sac or bodily migration prevents a permanent percutaneous seal from being formed between the skin and the implant, eventually resulting in extrusion of the implant. If the implant material used is not biocompatible enough, the maturation of connective tissue at the interface is inhibited and a strong mechanical connection is never established. In addition, the mechanical stresses that are always present can break the weak interface tissue connections, making percutaneous sealing impractical. Disruption of the implant-skin interface further provides an opportunity for infection and results in rapid, complete destruction of the tissue at the interface junction, all of which ultimately leads to failure of the implant.

Patent CN104887305B discloses a bone screw, its structure includes nail pole and nut, the nail pole includes polished rod section and screw rod section, compound degradable material layer on the peripheral periphery of polished rod section. The nail rod and the nut are made of metal materials; the degradable material layer is made of single material of polylactic acid, polyglycolic acid, polytrimethylene carbonate, polydioxanone or poly epsilon-caprolactone or copolymer of the material. However, such degradable coatings may generate acidic metabolites during the degradation process, and when the acidic metabolites are concentrated in vivo and cannot be completely metabolized in a short time, the peracid environment easily causes aseptic inflammation, thereby finally affecting the biological sealing property of the implant material and human tissues and causing implant failure.

Patent CN102000658A discloses a biological functional modification method based on polydopamine. Soaking a clean inorganic/metal material in a dopamine alkaline aqueous solution with the pH value of 7.2-10, introducing oxygen to fully oxidize the clean inorganic/metal material to obtain a single-layer polydopamine modification layer, drying the single-layer polydopamine modification layer, and then placing the material in an air atmosphere to carry out thermal oxidation treatment at 50-200 ℃ to obtain a plurality of firmly-combined polydopamine layers with high reactivity. The treated material is immersed in a solution of biological functional molecules containing amino or sulfhydryl groups, and a biological function bionic modification layer which is firmly combined is obtained on the surface of the material. Although the concept of surface modification is similar to that of the present invention, the invention does not specifically relate to the specific application of the device, the thickness of the polydopamine coating in the process is well controlled, and the choice of chemically bonded biomacromolecules does not emphasize the tissue compatibility and biological sealing, nor provides biological verification results related to percutaneous implantable medical devices such as bone screws.

Disclosure of Invention

The invention aims to solve the problems of poor histocompatibility and poor biological sealing performance of the conventional bone fixing screw, and provides a surface biological functionalized bone fixing screw. The novel surface biological functional medical bone screw is relatively simple in preparation method, and the coating is very stable in modification, so that long-term in-vivo implantation can be realized.

The purpose of the invention is realized by the following technical scheme:

a medical bone screw with a biofunctionalized surface comprises a metal screw body, wherein the metal surface of the screw body is used as a substrate, a polydopamine coating is deposited on the surface of the substrate and used as an intermediate layer, and bioactive molecules are connected to the surface of the polydopamine coating through chemical bonds and used as a functional modification layer.

Preferably, the bioactive molecules comprise one or more of collagen, fibronectin, laminin, cell growth factors, fibrin or fibrinogen, and the protein structure of the bioactive molecules selected by the invention contains polypeptide sequences such as RGD (arginine-aspartic acid), which are beneficial to cell adhesion, and can promote adhesion and proliferation of epidermal cells and fibroblasts on the surface of the bioactive molecules, so that tissue repair and wound healing can be realized in a short time after the percutaneous bone screw implantation, and the biological sealing effect of the bone screw is improved.

Preferably, the thickness of the polydopamine coating is 1-20nm, and the modification range of the coating is 70-100% of the area from the bottom to the top of the screw body. When the polydopamine coating is too thin, the modification on the surface of the substrate is insufficient, so that the combination density of bioactive molecules subjected to subsequent chemical modification on the surface of the bone screw is influenced, and the tissue cells are not induced to be rapidly adhered and proliferated on the surface of the screw; when the polydopamine coating is too thick, the intermolecular interaction formed by molecular accumulation between polydopamine and polydopamine is weak, so that the polydopamine on the surface layer of the chemically modified bioactive molecules is easy to peel off from the polydopamine accumulation layer, the bonding strength of the bioactive molecules is affected, and a stable biological sealing interface is not favorably formed finally.

Preferably, the screw body comprises a screw rod and a lower thread structure, a chamfer is arranged at the tail end of the screw rod, and the screw body is made of medical metal alloy.

Preferably, the medical metal alloy material comprises one or more of titanium and titanium alloy, magnesium alloy, nickel titanium alloy, stainless steel, cobalt-based alloy, noble metal, tantalum, niobium and zirconium.

Preferably, the titanium and the titanium alloy are composed of one or more of pure titanium, Ti-Al-V series alloy, Ti-Nb-Zr series alloy, Ti-Al-Fe series alloy, Ti-Al-Nb series alloy, Ti-Zr-Nb-Ta-Pd series alloy and Ti-Al-Mo-Zr series alloy.

Preferably, the magnesium alloy is composed of one or more of a Mg-Ca-based alloy, a Mg-Sn-Mn-based alloy, or a Mg-Sn-Mn-Zn-based alloy.

Preferably, the diameter of the surface biofunctionalized medical bone fixation screw is in the range of 0.5-3mm, the length of the screw is in the range of 10-50mm, and the length of the thread is in the range of 1-10 mm.

A preparation method of a medical bone screw with a bio-functionalized surface comprises the following steps:

1) performing grinding and polishing pretreatment and surface cleaning on the processed screw body;

2) soaking the obtained screw body in dopamine aqueous solution for reaction, then taking out, cleaning and drying the surface to form a polydopamine coating on the surface of the metal bone screw;

3) soaking the obtained bone screw with the surface modified with the polydopamine coating in a bioactive molecule solution, fixing the bioactive molecule to be modified on the surface of the polydopamine coating by using Schiff base reaction and/or Michael addition reaction, and incubating at low temperature;

4) and after the incubation is finished, respectively cleaning the surface of the material by using phosphate buffer solution or normal saline and ultrapure water to remove the unstable bioactive molecules, and finally obtaining the stable bioactive molecule coating.

The medical bone screw with the bio-functionalized surface is applied to treatment and operation of fracture and/or bone repair diseases, including implantation type artificial limbs, bone grafting, joint fusion, joint fixation and orthopaedics.

The surface biological functional medical bone fixing screw provided by the invention can be used for bone grafting, joint fusion, joint fixation, orthopedic surgery and other surgeries of human or animals.

The surface biological functional bone screw provided by the invention carries out surface modification on the traditional medical bone fixing screw by utilizing bioactive molecules for the first time, so that the inflammation reaction and the fibrous capsular sac formation of soft tissues are obviously weakened, and the number of new blood vessel tissues is obviously increased, therefore, compared with the traditional metal instrument, the surface biological functional medical bone fixing screw after modification has great improvement on the aspects of promoting bone tissue fusion and realizing biological sealing performance.

On the other hand, the preparation method of the surface biological functional bone screw designed by the invention is not complicated, only the surface biological functional modification is carried out on the basis of the traditional bare metal bone screw, the scale of the modification is only concentrated on the molecular level, the whole thickness of the coating is also several nanometers, and the mechanical property of the instrument is not influenced, so that the application scene is not changed.

In addition, the modification process is very simple, convenient and quick, the reliability and the necessity of the steps are emphasized in the existing surface modification method, the modification process can be completed only by soaking the polydopamine aqueous solution and the biomolecule solution, the modification time is greatly shortened, and the stability of the bioactive molecule coating obtained by the bionic and chemical bonding mode of the mussel is relatively high, so that the biomolecule is not easy to peel off from the surface of an instrument in the long-term use process. The whole preparation process does not involve complex instruments and equipment, does not need to use toxic organic solvents, and has the advantages of simple process, mild conditions and environmental protection.

The surface modification method disclosed by the invention adopts a stable polydopamine modified coating, is more suitable for a long-term implantable bone screw, closely combines the polydopamine surface modification technology with the specific application field of percutaneous sealing of implantable medical devices, finds the optimal surface modification process suitable for the percutaneous implantable bone screw, and has obvious innovation as shown by experimental results. The novel surface biological functional medical bone fixing screw designed by the invention is expected to replace the traditional bare metal bone fixing screw in the field of long-term implantable medical devices.

Drawings

FIG. 1 is a schematic view of a surface biofunctionalized medical bone fixation screw designed in accordance with the present invention;

wherein, 1 is a screw, 2 is a screw, and 3 is a surface biological functional coating;

figure 2. percutaneous implantation of metal screws and bioremediation through soft tissue in SD rats, wherein:

FIG. 2(A) is an overall view of a surface modified and unmodified screw, and a typical SEM image of a threaded part;

FIG. 2(B) is a schematic view of an X-ray image, slice orientation and slice after surgery;

fig. 2(C) is a histological image of H & E stained tissue sections of Ti and Ti-PDA-Fg at 5 months, and the distance of epidermal downward growth (n-4) to quantify the biological healing efficacy of the soft tissue after percutaneous implantation;

fig. 3(a) is a photograph of implants and wounds of SD rats at the indicated time points at the time of implantation experiment for a duration of 5 months;

fig. 3(B) shows the amount of implant retention versus time of implantation.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

The invention discloses a preparation technical route of a surface biological functional medical bone fixing screw, which takes the surface of a bone screw made of medical metal and alloy materials thereof as a substrate, a polydopamine coating is deposited on the surface of the substrate to be used as an intermediate layer, and biomolecules are chemically bonded on the surface of the polydopamine coating by Schiff base reaction and Michael addition reaction to be used as a functional modification layer, so that the bone screw with the surface biological functional modification is formed together.

The specific operation process is as follows:

1) firstly, processing a bar made of medical metal and alloy thereof into a specific shape as shown in figure 1 according to the size requirement of a required bone screw in a traditional metal processing mode;

2) grinding and polishing the metal screw by using a grinding and polishing machine to carry out grinding and polishing pretreatment and surface cleaning;

3) soaking the metal screw in the step (2) in a dopamine aqueous solution for reaction, then taking out, cleaning and drying the surface to form a polydopamine coating on the surface of the metal bone screw;

4) then, the bone screw with the surface modified with the polydopamine coating obtained in the step (3) is soaked in a bioactive molecule solution, bioactive molecules to be modified are fixed on the surface of the polydopamine coating through Schiff base reaction and/or Michael addition reaction, and low-temperature incubation is carried out;

5) and after the incubation is finished, respectively washing the surface of the material by using Phosphate Buffer Solution (PBS) and ultrapure water to remove the unstable connected bioactive molecules, and finally obtaining the stable bioactive molecule coating.

In a preferred embodiment, the matrix material of the surface biofunctionalized medical bone fixing screw is one or more of common medical metals and alloys thereof, including titanium and titanium alloys, magnesium alloys, nickel-titanium alloys, stainless steel, cobalt-based alloys, noble metals and pure metals (tantalum, niobium and zirconium).

As a preferred embodiment, the shape characteristic of the surface biological functionalized medical bone fixing screw consists of a screw rod, a thread and a surface modified coating.

As a preferred embodiment, the surface coating thickness of the surface biofunctionalized medical bone fixation screw is in the range of 1-20nm, and the coating modification is in the range of 70-100% of the area from the bottom to the top of the thread.

As a preferred embodiment, the diameter of the surface biofunctionalized medical bone fixation screw is in the range of 0.5-3mm, the length of the screw is in the range of 10-50mm, and the length of the thread is in the range of 1-10 mm.

As a preferred embodiment, the bioactive molecule comprises one or more of collagen, fibronectin, laminin, a cell growth factor, fibrin, or fibrinogen.

As a preferable embodiment, the polishing pretreatment in the step (2) comprises coarse grinding, fine grinding, coarse polishing and fine polishing, wherein the coarse grinding is carried out on 300-400-mesh silicon carbide abrasive paper, the fine grinding is carried out on 800-1200-mesh silicon carbide abrasive paper, the coarse polishing is carried out on a TexMet P polishing cloth by using a MetaDi diamond polishing solution with the particle size of 3-4 mu m, and the fine polishing is carried out on a Microcloth by using a MasterMet silica suspension polishing solution with the particle size of 0.5-1 mu m.

In a preferred embodiment, the concentration of the dopamine aqueous solution in the step (3) is 1-5 mg/mL, the pH is 8.0-9.0, 5-10 mM Tris-HCl buffer solution is additionally added, the bone screw is immersed in the dopamine aqueous solution, and the magnetic stirring is carried out at room temperature for 6-24 hours.

In a preferred embodiment, the biomolecule solution in step (4) is allowed to stand at 0 to 10 ℃ for 24 to 48 hours at a concentration of 0.1 to 1 mg/mL.

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the surface biofunctionalized medical bone fixing screw of the invention is specifically described below with reference to the specific embodiments. In the following examples, all chemical reagents used, unless otherwise noted, were analytically pure and did not require any treatment; the reaction temperature is given in units of ℃.

Example 1

Example 1 the process for preparing a bone fixation screw with a biologically functionalized modified surface in example 1 comprises the following steps:

step one

The titanium-aluminum-vanadium alloy bar is prepared into a bone fixing screw with the diameter of 1.6mm, the length of a screw rod of 16mm, the length of a thread of 4mm, the depth of the thread of 0.2mm and a 45-degree chamfer angle at the tail end by using a precise numerical control lathe.

Step two

And (3) putting the bone fixing screw obtained in the step one on a metallographic polishing machine, polishing for 1 minute by using 320-mesh silicon carbide abrasive paper, and then polishing for 1 minute on 1000-mesh silicon carbide abrasive paper. The rotating speed of the polishing machine during polishing is 300 revolutions per minute. The material was then polished on a TexMet P polishing cloth for 8 minutes using a 3.5 μm particle size MetaDi diamond slurry, and then polished on a Microcloth polishing cloth for 8 minutes using a 0.5 μm particle size MasterMet silica suspension slurry. The rotation speed of the polishing machine during polishing is 600 revolutions per minute. The material was then ultrasonically cleaned 2 times each for 5 minutes in sequence with acetone, ethanol and ultrapure water.

Step three

And D, immersing the bone fixing screw obtained in the step two in a dopamine solution with the concentration of 2mg/ml, wherein the concentration of a hydrochloric acid-Tris (hydroxymethyl) aminomethane (Tris-HCl) buffer solution in the solution is 10mM, the pH value is 8.5, and standing for 12 hours at room temperature under magnetic stirring. And (3) after the reaction is finished, taking out the sample, cleaning the sample for 3 times by using ultrapure water, and drying the surface by using a nitrogen gun to obtain the titanium with the polydopamine coating deposited on the surface.

Step four

And (3) soaking the bone screw with the surface modified with the polydopamine coating obtained in the third step in a modified fibrinogen solution with the concentration of 0.1mg/mL, fixing the bioactive molecule to be modified on the surface of the polydopamine coating by using Schiff base reaction and Michael addition reaction, and standing for 24h at 4 ℃ for incubation. And (3) taking out the sample after the incubation is finished, washing the sample for 5 minutes for 3 times by using ultrapure water, drying the surface by using a nitrogen gun to obtain the bone fixing screw with the surface biological functionalization, and sealing and storing the bone fixing screw in a refrigerator at 4 ℃.

Example 2

In example 2, the same portions as those in example 1 in the process of preparing the surface biofunctionalized bone fixation screw are omitted, and only the differences will be described.

The bone screw material selected for this embodiment is pure titanium.

In the third step of this example, the concentration of the dopamine solution is 5mg/mL, and the pH value of the solution is 8.4.

In step four of this example, the fibrinogen solution concentration was 0.5 mg/mL.

Example 3

In example 3, the same portions as those in example 1 in the titanium production process for the surface biofunctionalization modification were omitted, and only the differences will be described.

The bone screw material of this embodiment is nickel titanium alloy.

In step three of this example, the concentration of the dopamine solution is 1mg/mL, the pH of the solution is 8.6, and the time for which the material is left standing in the dopamine solution is 24 hours.

In the fourth step of this example, the biomolecule used is a fibroblast growth factor solution of 0.1mg/mL, and the standing time is 48 hours.

Example 4

The same portions as those in example 1 in the surface biofunctionalized titanium-based metal production process in example 4 are omitted, and only the differences will be described.

The bone screw material that this embodiment chose is stainless steel.

In the second step of this example, the polishing time with 320 mesh silicon carbide abrasive paper was 1.5 minutes, the polishing time with 1000 mesh silicon carbide abrasive paper was 1.5 minutes, the polishing time on TexMet P polishing cloth was 7.5 minutes, and the polishing time on Microcloth was 7.5 minutes.

In the third step of this example, the concentration of the dopamine solution is 3mg/mL, the pH value is 8.8, and the standing time is 8 hours.

In step four of this example, the biomolecule used was 0.2mg/mL fibrin solution and the standing time was 36 hours.

Example 5

The same portions as those in example 1 in the surface biofunctionalized titanium-based metal production process in example 5 are omitted, and only the differences will be described.

The bone screw material selected in this embodiment is cobalt-based alloy.

In the first step of this example, the polishing time with 320 mesh silicon carbide abrasive paper was 2 minutes, and the polishing time with 1000 mesh silicon carbide abrasive paper was 2 minutes. The polishing time on the TexMet P polishing cloth was 7.5 minutes, and the polishing time on the Microcloth was 7.5 minutes.

In the second step of this example, the sodium hydroxide concentration was 30g/L, the hydrogen peroxide concentration was 40g/L, and the alkali heat treatment time was 10 minutes.

In the third step of this example, the concentration of the dopamine solution is 2.5mg/mL, the pH value is 8.2, and the standing time is 24 hours.

In step four of this example, the biomolecule solution used was a 0.1mg/mL laminin solution.

Example 6

In example 6, the same portions as those in example 1 in the process for producing a titanium-based metal having a biologically functionalized and modified surface are omitted, and only the differences will be described.

The bone screw used in the present embodiment is made of magnesium alloy.

In the first step of this example, the polishing time with 320 mesh silicon carbide abrasive paper was 2 minutes, and the polishing time with 1000 mesh silicon carbide abrasive paper was 2 minutes.

In the third step of this example, the concentration of the dopamine solution is 2.5mg/mL, the pH value is 8.6, and the standing time is 18 hours.

In step four of this example, the biomolecule solution used was 0.2mg/mL fibronectin solution.

Example 7

In example 7, the same portions as those in example 1 in the process for producing a titanium-based metal having a biologically functionalized and modified surface are omitted, and only the differences will be described.

The bone screw used in this embodiment is made of a zirconium-titanium alloy.

In step three of this example, the concentration of the dopamine solution was 1.5mg/mL, and the standing time was 18 hours.

In step four of this example, the biomolecule solution used was a collagen solution of 0.1 mg/mL.

Effects and effects of examples 1 to 7

According to the surface biological functional medical bone fixing screw designed by the invention, the surface of the traditional medical bone fixing screw is modified by utilizing bioactive molecules for the first time, so that the inflammation reaction and the fibrous capsular sac formation of soft tissues are obviously weakened, and the number of new blood vessel tissues is obviously increased, therefore, compared with the traditional metal instrument, the modified surface biological functional medical bone fixing screw has obvious improvement on the aspects of promoting bone tissue fusion and realizing biological sealing performance. To verify the above conclusions, the inventors designed the following animal experiments to verify the designed surface biofunctionalized medical bone fixation screws.

Experiment one:

the bone fixing screw made of titanium-aluminum-vanadium alloy material in the embodiment 1 is selected for animal implantation experiments, the length of the bone fixing screw is 20mm, the diameter of the bone fixing screw is 1.6mm, the length of the thread part is 4mm, the experimental group is a biological functional coating with fibrinogen modification on the surface, the control group is an unmodified pure metal bone fixing screw, and the real object is shown in fig. 2 (A);

in the experiment, the selected animal experiment model animal is male SD rat of eight to twelve weeks old, and the weight is 300 to 330 g. Before surgery, animals were housed for 2 weeks to acclimate. Surgery was performed with 45mg/kg 2% (w/v) sodium pentobarbital under standard sterile conditions for general anesthesia. The shin area was shaved and disinfected with 10% povidone iodine. The skin of the tibial metaphysis was pierced with a scalpel down to the bone surface, followed by drilling a hole 8mm from the knee joint with a drill bit 1.4mm in diameter, perpendicular to the bone surface and penetrating the contralateral cortical bone. Finally, the implant is screwed into the bore and secured to the bilateral cortex of the tibia. For each experimental rat, a titanium peg was attached to each of the left and right tibia, with the tail end protruding from the skin surface, as shown in fig. 2 (B).

After surgery, all wounds and implants were sterilized. Rats were placed on a heat-insulating pad until awakening. Then the animals are raised in cages, and water and food can be freely enjoyed. Penicillin (100mg/kg) was intraperitoneally injected once a day after surgery for 7 consecutive days. In order to observe the new bone generation after implantation, a fluorescent double-label staining technology is applied. Calcein (5mg/kg) and alizarin red S (75mg/kg) were injected intramuscularly, respectively, on days 4 and 14 before the sacrifice of the rats.

The experimental result shows that the soft tissue reaction of the polydopamine-fibrinogen modified titanium alloy bone fixing screw is obviously weakened compared with that of an unmodified bone screw. Moreover, with the modification of fibrinogen, the number of new blood vessels also increases significantly. Therefore, the covalent modification of fibrinogen greatly improves the tissue compatibility of the titanium alloy bone screw. Compared with an unmodified control group, the degree of epithelium descending of the poly-dopamine-fibrinogen-modified titanium alloy bone fixing screw group is obviously reduced. Thus, a fibrinogen-functionalized titanium implant mediated by a polydopamine coating can effectively reduce epithelial downgoing and play an important role in promoting biologic sealing, as shown in fig. 2 (C). Mineral deposition rates of the poly-dopamine-fibrinogen-modified titanium alloy bone fixing screw group are remarkably higher than those of an unmodified group in 1 month and 5 months, and the results show that bone regeneration is greatly promoted after covalent modification of fibrinogen. Successful integration of the implant portion within the bone can provide strong support for the transcutaneous assembly and reduce stress at the skin-implant interface, thereby improving stability of the transcutaneous implant and wound healing at the implantation site, as shown in fig. 3 (a). In addition, bone screws modified with biofunctionalized coatings were found to have optimal implant retention by counting implant retention, as shown in fig. 3 (B).

Experiment two:

the same parts in the experimental verification of the surface biofunctionalized bone fixation screw in the animal experiment as in the first experiment are omitted, and only the differences will be described.

In this experiment, the bone screw material selected was pure titanium.

In the experiment, the animal model animal is guinea pig.

In this experiment, the bioactive molecule selected was fibrin.

The experimental result shows that compared with the unmodified bare titanium metal screw, the modified surface biological functional medical bone fixing screw has excellent performance in the aspects of promoting the fusion of the bone tissues of guinea pigs and reducing the inflammatory reaction of the implantation part.

Experiment three:

In this experiment, the bone screw material selected was nitinol.

In the experiment, the selected animal experiment model animal is rabbit.

In this experiment, the bioactive molecule selected was fibronectin.

In this experiment, the bone screw diameter was 2mm and the screw length was 30 mm.

The experimental result shows that compared with the unmodified naked titanium-nickel-titanium alloy bone screw, the modified surface biological functional medical bone fixing screw has excellent performance in the aspects of promoting the fusion of bone tissues of rabbits and realizing the biological sealing performance.

Experiment four:

In this experiment, the bone screw material selected was magnesium alloy.

In the experiment, the animal experimental model animal is Wistar rat.

In this experiment, the bioactive molecule selected was fibronectin.

The experimental result shows that compared with the unmodified magnesium alloy bone screw, the modified surface biological functional medical bone fixing screw has excellent performance in the aspects of promoting the bone tissue fusion of Wistar rats and improving the implantation stability of the screw.

Experiment five:

In this experiment, the bone screw material selected was stainless steel.

In the experiment, the selected animal experiment model animal is a faggots dog.

In this experiment, the bioactive molecule selected was a cell growth factor.

In this experiment, the bone screw was designed to have a diameter of 2.5mm and a screw length of 40 mm.

The experimental result shows that compared with the unmodified stainless steel bone screw, the modified surface biological functional medical bone fixing screw has obviously excellent performance in the aspects of promoting the bone tissue fusion of the chai dog and realizing the biological sealing performance of the implanted part.

Experiment six:

In this experiment, the bone screw material selected was a cobalt-based alloy.

In the experiment, the selected animal experiment model animal is BALB/c mouse.

In this experiment, the bioactive molecule selected was laminin.

The experimental result shows that compared with the unmodified cobalt-based alloy bone screw, the modified surface biological functional medical bone fixing screw has excellent performance in the aspects of promoting BALB/c mouse bone tissue fusion and effectively weakening epithelial downgoing.

Experiment seven:

In this experiment, the bone screw material selected was a zirconium titanium alloy.

In the experiment, the selected animal experiment model animal is a Chinese garden cat.

In the experiment, the selected bioactive molecules are fibrin and fibrinogen with the mole number of 1: 1 a mixture of two biologically active molecules.

In this experiment, the bone screw was designed to have a diameter of 2mm and a length of 35 mm.

The experimental result shows that compared with the unmodified zirconium-titanium alloy bone screw, the modified surface biological functional medical bone fixing screw has excellent performance in the aspects of promoting the bone tissue fusion of the Chinese rural cats and accelerating the formation of new bones.

In conclusion, the surface biofunctionalized bone fixation screw designed by the invention does not relate to complex instruments and equipment in the whole biofunctionalized modification process, does not need to use toxic organic solvents and crosslinking agents, and has the advantages of simple process, mild conditions and environmental protection. In addition, the bone fixing screw with the surface biologically functionalized and modified can be widely applied to operations such as implanted artificial limbs, bone transplantation, joint fusion, joint fixation, orthopedics and the like, and the prepared biologically functionalized and modified layer can promote biological sealing of the bone screw and soft tissues and endothelialization of tissues around materials, so that the bone fixing screw has a good application prospect.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A medical bone screw with a biofunctionalized surface comprises a metal screw body and is characterized in that the metal surface of the screw body is used as a substrate, a polydopamine coating is deposited on the surface of the substrate to serve as an intermediate layer, and bioactive molecules are connected to the surface of the polydopamine coating through chemical bonds to serve as a functional modification layer;

the bioactive molecule comprises one or more of collagen, fibronectin, laminin, cell growth factor, fibrin or fibrinogen.

2. The medical bone screw with the bio-functionalized surface as claimed in claim 1, wherein the thickness of the polydopamine coating is 1-20nm, and the modification of the coating ranges from 70-100% of the area from the bottom to the top of the screw body.

3. The medical bone screw with the bio-functionalized surface as claimed in claim 1, wherein the screw body comprises a screw rod and a lower thread structure, the end of the screw rod is chamfered, and the screw body is made of medical metal alloy.

4. The superficial biofunctionalized medical bone screw according to claim 3, wherein the medical metal alloy material comprises one or more of titanium and titanium alloy, magnesium alloy, nickel titanium alloy, stainless steel, cobalt-based alloy, noble metal, tantalum, niobium and zirconium.

5. The medical bone screw with bio-functionalized surface as claimed in claim 1, wherein the diameter of the medical bone fixing screw with bio-functionalized surface is in the range of 0.5-3mm, the length of the screw rod is in the range of 10-50mm, and the length of the thread is in the range of 1-10 mm.

6. The method for preparing the medical bone screw with the bio-functionalized surface as claimed in claim 1, comprising the following steps:

7. The method for preparing a medical bone screw with bio-functionalized surface as claimed in claim 6, wherein the concentration of the dopamine aqueous solution is 1-5 mg/mL, the pH is 8.0-9.0, 5-10 mM Tris-HCl buffer solution is additionally added, the screw body is immersed in the dopamine aqueous solution, and magnetic stirring is carried out at room temperature for 6-24 hours.

8. The method for preparing the medical bone screw with the bio-functionalized surface as claimed in claim 7, wherein the bioactive molecule solution has a concentration of 0.1-1 mg/mL and is allowed to stand at 0-10 ℃ for 24-48 hours.

9. The use of the medical bone screw with bio-functionalized surface according to claim 1, wherein the medical bone screw with bio-functionalized surface is used for treating and operating bone fracture and/or bone repair diseases, including implantable prosthesis, bone graft, joint fusion, joint fixation and orthopaedics.