AU2021102400A4 - Method for preparing a strontium-doped calcium-phosphorus compound film with a nano-ordered structure - Google Patents

Abstract

The present disclosure relates to a preparation method of a strontium-doped calcium phosphorus compound film with a nano-ordered structure, and relates to the field of medical metals. Pretreating a medical implant material to be processed and subjecting a substrate to cathodic electrochemical deposition, to obtain a strontium-doped calcium-phosphorus compound film with a nano-ordered structure on the surface of the substrate. A nano-ordered calcium phosphorus compound/strontium composite coating similar to a natural bone structure is constructed on the surface of medical metal through electrochemical directional deposition so that the biocompatibility and the biological activity of the material can be greatly improved, and clinical application can be realized; the preparation method of the micro-nano-ordered structure of octacalcium phosphate/strontium composite coating is established; surface construction of calcium phosphorus compound/strontium composite film is realized by using an electrochemical deposition method; and the preparation method is an important method for manufacturing a high-bioactive nano ordered composite of artificial bone material.

Description

METHOD FOR PREPARING A STRONTIUM-DOPED CALCIUM PHOSPHORUS COMPOUND FILM WITH A NANO-ORDERED STRUCTURE

TECHNICAL FIELD The invention relates to the field of medical metals, in particular to a method for preparing a strontium-doped calcium-phosphorus compound film with a nano-ordered structure controlled by electrochemical deposition on the surface of medical metals. BACKGROUND As an important component of the human body's hard tissue, bone is constructed from calcium phosphate salts, collagen and some trace elements (Mn, Sr, Mg, Zn, Si...) and other components, especially the calcium phosphate salts in natural bones are usually a micro-nano ordered hierarchical structure. In the treatment of bone function loss caused by bone defect or trauma caused by bone defect, autologous bone transplantation is usually the gold standard. However, the source of autologous bone is limited, and artificially prepared calcium phosphate salt materials are usually used as substitutes. From the perspective of bionics, it is necessary to prepare bone tissue substitutes that are as close as possible to the natural bone structure and composition of the human body. Calcium phosphate salt has high biological activity and is transformed into bone-like apatite under physiological conditions, which is beneficial to the adhesion, proliferation and differentiation of bone cells. With the advent of an aging society, osteoporosis has become a global health problem. Osteoporosis leads to increased bone fragility and increased fracture risk. The root cause is the loss of balance between bone resorption and bone formation. In the past few decades, due to the development of anti-osteoporosis drug strontium ranelate, the effect of strontium on bone has attracted the attention of many researchers. However, there are reports that the effect of strontium mainly depends on the dose. Low concentration of strontium can increase the rate of bone formation, and high doses of strontium will cause abnormal bone mineralization and metabolism. Therefore, the amount of strontium ions doped into calcium phosphate salt during preparation needs to be strictly controlled. Because strontium ions and calcium phosphate salts play an important role in bone metabolism, the combination of the two has extremely excellent performance, and researchers are very interested in the combination of the two. Some researchers have used electrochemical deposition, micro-arc oxidation, electrophoretic deposition, and air plasma spraying to prepare a composite coating of HA (DCPD) and strontium ions -]. In many related studies, the calcium phosphate salt biomaterials with micro-nano-ordered hierarchical structure cannot be effectively prepared. Electrochemical deposition is a promising method for preparing bone substitute materials. Its preparation conditions are mild, and by adjusting the parameters of the electrochemical deposition method, the controllable preparation of calcium phosphate salt biomaterials with micro-nano-ordered hierarchical structure can be achieved, so that its biocompatibility and biological activity are significantly improved. By incorporating strontium ions in the electrolyte and controlling certain deposition modes, deposition temperature and other conditions, an ordered structure of strontium ions/calcium phosphate composite materials can be co-deposited on the surface of medical metals. The addition of strontium ions can directly participate in the deposition process, or affect the growth of the deposited layer, and can control the morphology of the resulting film. The strontium/calcium phosphate salt prepared by electrochemical method has excellent biological activity, which can be expected to accelerate bone growth and fixation of implant materials in the body, shorten the treatment cycle of patients, and is especially suitable for patients with osteoporosis.

SUMMARY Preferred embodiments of the present invention may provide a method for preparing a strontium doped calcium-phosphorus compound film with a nano-ordered structure that can be controlled to prepare a bone-like structure and uniform chemical properties under mild conditions. According to the present invention there is provided a method comprising the following steps: 1) pretreating a medical implant material to be processed; 2) performing cathodic electrochemical deposition on the substrate to obtain a strontium doped calcium-phosphorus compound film with a nano-ordered structure on the substrate surface. Preferably, in step 1), the substrate is a medical implant material, etc., the medical implant material may be a medical implant metal, etc.; the medical implant metal can be selected from one of titanium, titanium alloy, stainless steel, etc. The specific method of the substrate pretreatment can be: immersing the medical implant materials in acetone, ethanol and deionized water successively for ultrasonic cleaning, then treating and cleaning in HNO3 and HF solution; the concentration of HN03 is 8%-10%, and the concentration of HF is 0.8%-1.2 %. In step 2), the deposition solution for performing cathodic electrochemical deposition on the substrate can be a [Sr2+] solution containing 0.01-0.14mol/L of [Ca2 +], 0.04-0.4 mol/L of phosphate species and a certain ratio of [Sr2+]/ ([Sr2+] +[Ca2+])= 0.1- 2 0%; the deposition solution can be Ca(N03)2, NaH2PO4 or Sr(N03)2, etc.; the pH value of the deposition solution may be 2-6; the current density of the electrochemical deposition may be 0.1-1.5mA/cm 2 ; the deposition temperature of the electrochemical deposition may be 25-90°C, and the deposition time may be 3 min. Preferred embodiments of the invention can construct a nano-ordered calcium-phosphorus compound/strontium composite coating similar to the natural bone structure by electrochemical directional deposition on the medical metal surface, thereby greatly improving the biocompatibility and biological activity of the material and realizing clinical application. By systematically investigating the influence of a series of electrochemical deposition parameters on the deposition behavior of calcium-phosphorus compounds and strontium composite coatings, a method for preparing a micro-nano-ordered structure of octacalcium phosphate/strontium composite coating is established. The electrochemical deposition method is used to realize the surface construction of the calcium-phosphorus compound/strontium composite film. It provides an important method for manufacturing high-bioactive nano-ordered composite artificial bone materials.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows SEM images of electrochemically deposited coatings with different magnifications. In Figure 1, Figures a, b, and c are the surface morphologies of the octocalcium phosphate (OCP) coating obtained without adding strontium ions in the electrolyte (Figure a is magnification of 1000 times, Figure b is magnification of 5000 times, and Figure c is magnification of 20000 times); Figures d, e ,f are the surface morphologies of the OCP/Sr composite coating obtained by adding 1% strontium ion to the electrolyte (Figure d is magnification of 1000 times, Figure e is magnification of 5000 times, and Figure f is magnification of 20000 times); Figures g, h, i are the surface morphologies of the OCP/Sr composite coating obtained by adding 5% strontium ions in the electrolyte (Figure d is magnification of 1000 times, Figure e is magnification of 5000 times, and Figure f is magnification of 20000 times); Through the comparison of the three, it can be observed that with the increase of the doping amount of strontium ions, there is no obvious change in the grains of the film, and the grains of the film gradually change from a lodging shape to an upright shape. Figure 2 is the Strontium EDS-Mapping diagram of the electrochemically deposited coating with 1% strontium ion doping. Figure 3 is the Strontium EDS-Mapping diagram of the electrochemically deposited coating with 5% strontium ion doping. Figure 4 is the XRD pattern of electrochemically deposited coating. In Figure 4, a represents the XRD pattern of a calcium phosphate salt coating prepared without adding strontium ions in the electrolyte, d is a partial enlarged view of a (20=25.5-26.5), and b represents the XRD pattern prepared by adding 1% strontium ions to the electrolyte, e is a partial enlarged view of b (20=25.5 26.5), c represents the XRD pattern prepared by adding 5% strontium ion to the electrolyte, and f is a partial enlarged view of c (20=25.5-26.5), the abscissa is 2 Theta(deg).

Figure 5 is the alkaline phosphatase (ALP) activity of MC3T3-El cells cultured on the surface of electrochemical deposition film for different time. In Figure 5, */** represents a significant difference between 5%Sr/CaP and CaP or 1%CaP, * represents p <0.05, ** represents

p <0.001. DESCRIPTION OF THE EMBODIMENTS The following embodiments will further illustrate the present invention in conjunction with the drawings. Example 1 A calcium phosphate salt film was prepared by electrochemical co-deposition method. The pure titanium foil was cut into a size of lcmxlcm, washed in acetone, ethanol, and deionized water successively by ultrasonic cleaning for 15 minutes, and then dried. The solution of HF and HNO3 with a volume ratio of 1:10 was prepared. The pretreated titanium foil was immersed in the solution for 2 minutes, rinsed with deionized water and dried. After being taken out, the deposition solution contains 0.03M of Ca(N03)2 and 0.12M of NaH2PO4, the treated titanium foil was used as the anode, the graphite rod was used as the cathode, and the Sr/calcium phosphate salt (OCP) composite film was electrodeposited on the surface of the titanium foil using the constant current mode (0.5mA/cm 2 ), and the deposition time was 10 min. See Figures a-c in Figure 1, Figure 2, Figure 3 and Table 3, from Figure 2 and Figure 3, it can be clearly observed that strontium ions are uniformly distributed on the coating surface and increased with the increase of the amount of strontium ions doped in the electrolyte. Comparing the OCP/strontium composite coating (b, c) in Figure 4a with the OCP standard card shows that after adding strontium ions in the electrolyte, the main component of the coating is still OCP, but the diffraction peak of crystal plane (010) gradually disappears. Comparing d, e and f in Figure 4 shows that when strontium ions are added to the electrolyte, the diffraction peak of the crystal plane (002) obviously shifts to the left. According to the Bragg equation 2dsinO=n, the diffraction angle of the crystal plane decreases and the surface crystal spacing increases, indicating that the doping of strontium ions causes the crystal lattice in the OCP film to become larger. Both the OCP coating (curve a) and the OCP/strontium composite coating (curves b and c) on the electrode have a certain preferred orientation on the (002) crystal plane, and moreover, the preferred strength of OCP/ strontium composite coating on the (002) crystal plane is more obvious. Table 1 and Table 2 are the EDS spectrum element analysis table of the calcium phosphate salt/strontium composite coating. Table 1 shows that the doping amount of strontium ion is 1%, that is, Sr/ (Sr +Ca) =1%; Table 2 shows that the doping amount of strontium ion is 5%, that is, Sr/ (Sr +Ca) =5%. According to the EDS spectrum element analysis result of the electrochemically deposited coating, it can be seen that the composite film is mainly composed of calcium phosphate salt (OCP), and the ratio of calcium to phosphorus is about 1.0-1.1, which is lower than the theoretical value of the ratio of calcium to phosphorus of octacalcium phosphate (1.33). The amount of strontium ions in the film increases with the increase of the strontium ion concentration in the electrolyte.

Table 1

element mass (%) atom( %)

OK 39.95 61.93 PK 17.45 13.98

Ca K 22.97 14.22

Ti K 18.39 9.52

Sr L 1.24 0.35

Total 100.00

Table 2 element mass (%) atom( %)

OK 44.55 64.87

PK 22.56 16.97

Ca K 29.85 17.35 Sr L 3.04 0.81 total 100.00

Example 2 The 1% Sr/calcium phosphate salt composite film was prepared by electrochemical co deposition method. In the deposition solution of Example 1, 1% of Sr was added to keep the total concentration of Sr and Ca unchanged. Other conditions are the same as in Example 1. See d-f in Figure 1 and Table 3. Example 3 The 5% Sr/calcium phosphate salt composite film was prepared by electrochemical co deposition method. In the deposition solution of Example 1, 5% of Sr was added to keep the total concentration of Sr and Ca unchanged. Other conditions are the same as in Example 1. See g, h, i in Figure 1 and Table 3.

Table 3 electrodeposition Temperature Time example substrate electrlytemoe(C(int mode (°C) (min) 1 titanium 0-03 M Ca(NO3)IO. 12M constant current 65+5 10

NaH 2PO4(pH=3.60) density (O,5mA/cm 2

) 0,0003M Sr(NO 3)/0.0297 M Ca(NO3)/0A12M constant current 2 titanium NaH2PO4 density 65±5 10 (Sr/(Ca+Sr)=O,p1=3-6 (05mA/cm 2

) 0) 0.00 iSM Sr(N03)2/0.0285 M Ca(N0 3)70.12M constant current 3 titanium NaH2PO4 density 65±5 10 2 (Sr/(Ca+Sr)--O5,pH=3.6 (0.5mA/cm

) 0)

The films in Examples 1 to 3 were prepared by the electrochemical co-deposition method, and the ALP kit was used to test the ability of the films to induce differentiation of pre-osteoblast MC3T3 El. Cell density is 0.5x10 4 cells/cm 2, the incubation time is 1, 4, 7 days, the test result is shown in Figure 5. It can be seen from the alkaline phosphatase (ALP) activity that as the content of strontium ions in the film increases from 0% to 5%, the alkaline phosphatase activity of MC3T3 El cells firstly increases and then decreases. It shows that doping a certain amount of strontium ions into the calcium phosphate salt film is beneficial to improve the ability of the calcium phosphate salt film to induce the differentiation of MC3T3-E1 cells.

Claims (5)

Claims WHAT IS CLAIMED IS:

1. A method for preparing a strontium-doped calcium-phosphorus compound film with a

nano-ordered structure, comprising the following steps:

1) pretreating a substrate to be processed; 2) performing cathodic electrochemical deposition to obtain a strontium-doped calcium phosphorus compound film with a nano-ordered structure on the substrate surface.

2. The method for preparing a strontium-doped calcium-phosphorus compound film with a nano-ordered structure according to claim 1, wherein in step 1), the substrate is a medical implant material; wherein the medical implant material is a medical implant metal; wherein the medical implant metal is selected from one of titanium, titanium alloy, and stainless steel.

3. The method for preparing a strontium-doped calcium-phosphorus compound film with a nano-ordered structure according to claim 1, wherein in step 1), the specific method for pretreatment of the substrate is: immersing the medical implant materials in acetone, ethanol and deionized water successively for ultrasonic cleaning, then performing treating and cleaning in HNO3 and HF solution; the concentration of HNO3 is 8%-10%, and the concentration of HF is 0.8%-1.20%.

4. The method for preparing a strontium-doped calcium-phosphorus compound film with a nano-ordered structure according to claim 1, wherein in step 2), the deposition solution for performing cathodic electrochemical deposition on the substrate is [Sr2+] solution containing 0.01 0.l4mol/L of [Ca2+], 0.04-0.4 mol/L of phosphate species and a certain ratio of

[Sr2+]/ ([Sr2+]+[Ca2+])= 0.1-20%; wherein the deposition solution is Ca (N03)2, NaH2PO4 or Sr(N03)2; wherein the pH value of the deposition solution is 2-6.

5. The method for preparing a strontium-doped calcium-phosphorus compound film with a nano-ordered structure according to claim 1, wherein in step 2), the current density of the electrochemical deposition is 0.1-1.5 mA/cm 2; wherein in step 2), the deposition temperature of the electrochemical deposition is 25-90°C, the deposition time is 3-60min.