TWO-STAGE SINTERING METHOD FOR PREPARING POROUS BIPHASIC CALCIUM PHOSPHATE CERAMIC FROM CALCIUM-CONTAINING BIOLOGICAL WASTE

Abstract

The present invention relates to a two-stage sintering method for preparing a porous biphasic calcium phosphate ceramic from calcium-containing biological waste, wherein hydroxyapatite prepared from calcium-containing waste is mixed with a foaming agent to prepare a bone graft material having medicinal use through two-stage sintering.

Claims

1. A two-stage sintering method for preparing porous biphasic calcium phosphate ceramic from calcium-containing biological waste, comprising: a mixing and rotating step of mixing hydroxyapatite and a foaming agent into a mixture, and stirring the mixture at high speed into a foam shape; a drying step of drying the mixture the foam shape into a shaped mixture; a first-stage sintering step of heating the shaped mixture at 300 degrees to 900 degrees for 1 to 5 hours; and a second-stage sintering step of continually heating the shaped mixture after the first-stage sintering at 900 degrees to 1400 degrees for 0.1 to 30 hours to obtain a bone graft material containing the porous biphasic calcium phosphate ceramic.

2. The two-stage sintering method for preparing porous biphasic calcium phosphate ceramic from calcium-containing biological waste of claim 1, wherein the calcium-containing biological waste is egg shells, crustacean crab shells, shrimp shells, lobster shells, freshwater lobster shells and krill shells, bivalvia oyster shells, oyster shells, clam shells, gastropoda abalone shells.

3. The two-stage sintering method for preparing porous biphasic calcium phosphate ceramic from calcium-containing biological waste of claim 1, wherein the foaming agent of the mixing and rotating step is coconut oil foaming agent, glucose foaming agent, amino acid foaming agent, weak acid foaming agent, sodium lauroyl sarcosinate, fatty alcohol surfactant or a combination thereof.

4. The two-stage sintering method for preparing porous biphasic calcium phosphate ceramic from calcium-containing biological waste of claim 1, wherein the mixing ratio of the hydroxyapatite and the foaming agent of the mixing and rotating step is from 10% to 90% to 90% to 10%.

5. The two-stage sintering method for preparing porous biphasic calcium phosphate ceramic from calcium-containing biological waste of claim 1, wherein the high speed of the mixing and rotating step is from 250 to 3000 rpm.

6. The two-stage sintering method for preparing porous biphasic calcium phosphate ceramic from calcium-containing biological waste of claim 1, wherein the drying temperature of the drying step is from 50 to 200 degrees.

7. A porous biphasic calcium phosphate ceramic prepared by the method of claim 1, which comprises hydroxyapatite and beta-tricalcium phosphate, wherein the volume percentage of the hydroxyapatite is from 20% to 80%, and the volume percentage of the beta-tricalcium phosphate is from 20% to 80%.

8. A porous biphasic calcium phosphate ceramic prepared by the method of claim 2, which comprises hydroxyapatite and beta-tricalcium phosphate, wherein the volume percentage of the hydroxyapatite is from 20% to 80%, and the volume percentage of the beta-tricalcium phosphate is from 20% to 80%.

9. A porous biphasic calcium phosphate ceramic prepared by the method of claim 3, which comprises hydroxyapatite and beta-tricalcium phosphate, wherein the volume percentage of the hydroxyapatite is from 20% to 80%, and the volume percentage of the beta-tricalcium phosphate is from 20% to 80%.

10. A porous biphasic calcium phosphate ceramic prepared by the method of claim 4, which comprises hydroxyapatite and beta-tricalcium phosphate, wherein the volume percentage of the hydroxyapatite is from 20% to 80%, and the volume percentage of the beta-tricalcium phosphate is from 20% to 80%.

11. A porous biphasic calcium phosphate ceramic prepared by the method of claim 5, which comprises hydroxyapatite and beta-tricalcium phosphate, wherein the volume percentage of the hydroxyapatite is from 20% to 80%, and the volume percentage of the beta-tricalcium phosphate is from 20% to 80%.

12. A porous biphasic calcium phosphate ceramic prepared by the method of claim 6, which comprises hydroxyapatite and beta-tricalcium phosphate, wherein the volume percentage of the hydroxyapatite is from 20% to 80%, and the volume percentage of the beta-tricalcium phosphate is from 20% to 80%.

13. The porous biphasic calcium phosphate ceramic of claim 7, wherein the pore size of the porous biphasic calcium phosphate ceramic is between 50 micrometers and 700 micrometers.

14. The porous biphasic calcium phosphate ceramic of claim 8, wherein the pore size of the porous biphasic calcium phosphate ceramic is between 50 micrometers and 700 micrometers.

15. A porous biphasic calcium phosphate ceramic of claim 7, which can be used for bone graft and dental filling material.

16. A porous biphasic calcium phosphate ceramic of claim 8, which can be used for bone graft and dental filling material.

17. A porous biphasic calcium phosphate ceramic of claim 9, which can be used for bone graft and dental filling material.

18. A porous biphasic calcium phosphate ceramic of claim 10, which can be used for bone graft and dental filling material.

19. A porous biphasic calcium phosphate ceramic of claim 11, which can be used for bone graft and dental filling material.

20. A porous biphasic calcium phosphate ceramic of claim 12, which can be used for bone graft and dental filling material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is the X-ray diffractometer (XRD) diffraction patterns of porous biphasic calcium phosphate ceramics sintered at different holding temperatures and time.

[0015] FIG. 2 is the XRD diffraction patterns of porous biphasic calcium phosphate ceramics sintered at different holding temperatures and time.

[0016] FIG. 3 is the XRD diffraction patterns of the porous biphasic calcium phosphate ceramics sintered at different holding temperatures and time.

[0017] FIG. 4 is the Fourier-transform infrared spectroscopy (FTIR) analysis of the porous biphasic calcium phosphate ceramic.

[0018] FIG. 5 is the field emission scanning electron microscope (FESEM) images of the porous biphasic calcium phosphate ceramic.

[0019] FIG. 6 is the pore diameter distribution of the porous biphasic calcium phosphate ceramic.

[0020] FIG. 7 is the pH changes of the porous biphasic calcium phosphate ceramic immersed in simulated body fluid (SBF).

[0021] FIG. 8 is FESEM images of the porous biphasic calcium phosphate ceramics immersed in SBF for 7 days.

[0022] FIG. 9 is the MTT cell viability assay.

[0023] FIG. 10 is the WST-8 cell activity test of D1 mouse precursor stein cells on day 1, day 7 and day 14.

[0024] FIG. 11 is the ALP bone differentiation test of D1 mouse precursor stein cells on day 1, day 7 and day 14.

DETAILED DESCRIPTION OF THE INVENTION

[0025] As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are used Interchangeably.

[0026] The present invention uses waste oyster shells as raw materials to prepare hydroxyapatite. The preparation process changes the waste oyster shells into a bone graft material having biphasic hydroxyapatite/beta-tricalcium phosphate through changes in its phase. It can further enhance the added value of waste oyster shells, and mitigate the environmental pollution problems caused by them.

[0027] According to the purpose of the present invention, the composition of the hydroxyapatite crystal structure synthesized by using the biological calcium-containing raw material such as oyster shells, is much closer to human bone, as a result, the biocompatibility is higher.

[0028] According to the embodiment of the present invention, the following steps are included: a mixing and rotating step, a drying step, a first-stage sintering step and a second-stage sintering step.

[0029] In the mixing and rotating step, hydroxyapatite and a foaming agent are mixed into a mixture at a ratio from 10% to 90% to 90% to 10%, and the mixture is mixed at a high speed of 250 to 3000 rpm to form a foam shape, wherein a preferred mixing ratio is from 15% to 85% to 85% to 15%.

[0030] In the drying step, the foam-shaped mixture after the mixing and rotating step is dried at 50-200 degrees to form a shaped mixture.

[0031] In the first-stage sintering step, the shaped mixture is heated at a holding temperature of 300 degrees to 900 degrees for 1 to 5 hours, wherein a holding temperature condition for a better sintering effect is heating at a temperature of 500 degrees to 800 degrees for 2 to 4 hours.

[0032] The second-stage sintering step, the shaped mixture after the first-stage sintering continues to be heated at a holding temperature of 900 degrees to 1400 degrees for 0.1 to 30 hours to obtain a bone graft material containing porous biphasic calcium phosphate ceramic, wherein the holding temperature condition for a better sintering effect is heating at a temperature of 1000 degrees to 1200 degrees for 15 to 30 hours.

[0033] According to the embodiment of the present invention, the prepared biphasic calcium phosphate has physical characteristics including a porosity of 40-95% and a pore size of 50-700 μm.

[0034] According to the embodiment of the present invention, the prepared biphasic calcium phosphate contains hydroxyapatite and beta-tricalcium phosphate components, the content of the hydroxyapatite (volume percentage) is from 20% to 80%, and the content of beta-tricalcium phosphate (volume percent) is from 20% to 80%.

[0035] According to the embodiment of the present invention, the pores larger than 100 μm and smaller than 100 μm can be produced so as to satisfy the applicability of porous implants, and the pores larger than 100 μm can cause ingrowth of bone tissues. In addition, the hydroxyapatite powder, after being sintered, forms necking to be connected with each other, indicating that the powders are bonded to each other so that they can provide the strength required for surgical procedures.

[0036] According to the embodiment of the present invention, the hydroxyapatite crystal grain size is between 32 nm and 146 nm.

[0037] According to the embodiment of the present invention, the beta-tricalcium phosphate crystal grain size is between 37 nm and 49 nm.

[0038] According to the embodiment of the present invention, the crystallinity of the hydroxyapatite is higher than 62%.

[0039] The waste material of the present invention includes but is not limited to egg shells, crustacean crab shells, shrimp shells, lobster shells, freshwater lobster shells and krill shells, bivalvia oyster shells, oyster shells, clam shells, gastropoda abalone shells.

[0040] Another aspect of the present invention provides a biomedical material and a preparation method, including but not limited to bone materials and dental materials.

[0041] Another aspect of the present invention provides a calcium-phosphorus compound containing sodium, magnesium and strontium and a preparation method thereof.

EXAMPLE

[0042] The following examples are non-limited and are merely representative of various aspects and features of the present invention.

EXAMPLE 1: XRD Diffraction

[0043] After grinding the samples into powder, phase analysis was performed by an X-ray diffraction analyzer (XRD; D8, Bruker, Germany) with Cu K-alpha radiation of wavelength 0.15406 nm. The operating voltage is 30 kV, and the operating current is 30 mA. The scanning speed is set to 2°/min, and the diffraction angle is 20°-40°.

[0044] According to a preferred embodiment of the present invention, 1 gram of hydroxyapatite was mixed with 1.5 ml of a foaming agent, wherein the foaming agent included but was not limited to coconut oil foaming agent, glucose foaming agent (decyl glucosamine), amino acid foaming agent (TEA cocoyl glutamate), weak acid foaming agent (ammonium lauryl sulfate), sodium lauroyl sarcosinate, fatty alcohol surfactant (fatty alcohol ethoxylate).

[0045] As shown in FIG. 1, the XRD diffraction patterns of the porous biphasic calcium phosphate ceramic of the present invention sintered at different holding temperatures and time were shown. Through the diffraction patterns, the phase ratios between hydroxyapatite and beta-tricalcium phosphate, two-stage sintering temperatures and time were obtained and shown in Table 1 below.

[0046] Table 1 Phase ratios, crystal grain sizes and crystallinity of the porous biphasic calcium phosphate ceramic after being sintered at different holding temperatures and time.

TABLE-US-00001 S1 S2 S3 S4 first-stage sintering 700 700 700 700 temperature/time degrees/ degrees/ degrees/ degrees/ 2 hours 2 hours 2 hours 2 hours second-stage 900 900 900 900 sintering degrees/ degrees/ degrees/ degrees/ temperature/time 1 hour 4 hours 5 hours 6 hours ratio of 42:58 45:55 44:46 45:55 hydroxyapatite:beta- tricalcium phosphate hydroxyapatite 36 49 34 35 crystal grain size (nm) beta-tricalcium 49 43 49 49 phosphate crystal grain size (nm) hydroxyapatite 71 69 75 73 crystallinity (%)

[0047] According to a preferred embodiment of the present invention, 1 gram of hydroxyapatite was mixed with 1.5 ml of a foaming agent, wherein the foaming agent was the coconut oil.

[0048] As shown in FIG. 2, the XRD diffraction patterns of the porous biphasic calcium phosphate ceramic of the present invention sintered at different holding temperatures and time were shown. Through the diffraction patterns, the phase ratios between hydroxyapatite and beta-tricalcium phosphate, two-stage sintering temperatures and time were obtained and shown in Table 2 below.

[0049] Table 2 Phase ratios, crystal grain sizes and crystallinity of the biphasic porous calcium phosphate ceramic after being sintered at different holding temperatures.

TABLE-US-00002 H1 H2 H3 first-stage sintering 700 700 700 temperature/time degrees/ degrees/ degrees/ 2 hours 2 hours 2 hours second-stage sintering 700 1200 1400 temperature/time degrees/ degrees/ degrees/ 4 hours 4 hours 4 hours ratio of hydroxyapatite:beta- 51:49 47:53 HA + tricalcium phosphate alpha- TCP hydroxyapatite crystal grain 32 36 146 size (nm) beta-tricalcium phosphate 37 37 49 crystal grain size (nm) hydroxyapatite crystallinity 62 92 95 (%)

[0050] According to a preferred embodiment of the present invention, 1 gram of hydroxyapatite was mixed with 1.5 ml of a foaming agent, wherein the foaming agent was the coconut oil.

[0051] As shown in FIG. 3, the XRD diffraction patterns of the porous biphasic calcium phosphate ceramic of the present invention sintered at different holding temperatures and time were shown. Through the diffraction pattern, biphasic ratios between hydroxyapatite and beta-tricalcium phosphate, two-stage sintering temperatures and time were obtained and shown in Table 3 below.

[0052] Table 3 Phase ratios, crystal grain sizes and crystallinity of the porous biphasic calcium phosphate ceramic after being sintered at different holding time.

TABLE-US-00003 mp1 mp2 mp3 first-stage sintering 700 700 700 temperature/time degrees/ degrees/ degrees/ 2 hours 2 hours 2 hours second-stage sintering 1000 1000 1000 temperature/time degrees/ degrees/ degrees/ 20 hours 25 hours 30 hours ratio of hydroxyapatite:beta- 67:33 62:38 55:45 tricalcium phosphate hydroxyapatite crystal 49 50 38 grain size (nm) beta-tricalcium phosphate 49 38 38 crystal grain size (nm) hydroxyapatite 89 90 92 crystallinity (%)

[0053] According to one embodiment of the present invention, the content of hydroxyapatite (volume percentage) was from 20% to 80%, and the content of beta-tricalcium phosphate (volume percentage) was from 20% to 80%, wherein the preferred ones were 62% and 38%, respectively.

[0054] According to one embodiment of the present invention, the crystal grain sizes of the hydroxyapatite were all between 32 nm and 146 nm, preferably 38, 49, and 50 nm.

[0055] According to one embodiment of the present invention, the crystal grain sizes of beta-tricalcium phosphate were all between 37 nm and 49 nm, and preferably 37, 38, and 49 nm.

[0056] According to one embodiment of the present invention, the first-stage sintering temperature and time were 700 degrees and 2 hours, wherein the preferred second-stage sintering temperature was 1000 degrees, and the preferred sintering time was 25 hours. Subsequent analyses were conducted under this condition.

EXAMPLE 2: FTIR Analysis

[0057] The chemical compositions of the samples were analyzed using a Fourier transform infrared spectrometer (FTIR; Cary 630, Agilent, Santa Clara, USA) through a typical KBr pellet technique, and the infrared spectra were obtained with a wavenumber range of 600-4000 cm.sup.−1.

[0058] As shown in FIG. 4, graph of the FTIR analysis results of the porous biphasic calcium phosphate ceramic of the present invention was shown. Through comparison of the functional groups, the sintered products having biphasic calcium phosphate according to the present invention, including OH group and PO.sub.4.sup.3− groups.

EXAMPLE 3: FESEM Imaging

[0059] The surface of the sample was coated with platinum (current was 10 mA, sputtering time was 50 seconds), and the microscopic morphology of the sample under different magnifications was observed by scanning electron microscope (FE-SEM; S-4800, Hitachi, Japan).

[0060] As shown in FIG. 5, FESEM images of the porous biphasic calcium phosphate ceramic was shown of the present invention. It was found that the crystalline particles after the sintering of the present invention had porosity, and many pores were larger than 100 μm. In addition, it could be found from the images that the pores had connectivity, the pore on the side could be observed through the pore on the other site.

[0061] As shown in FIG. 6, the pore diameter distribution of the porous biphasic calcium phosphate ceramic was shown. Through an image analysis method, the average diameter was used to represent the pore diameter distribution of the porous ceramic particles prepared by the present invention, and more than 60% of the pores of the porous ceramic particles prepared by the present invention had an average pore diameter greater than 100 μm.

[0062] As shown in FIG. 7, it shows a graph of the pH changes of the porous biphasic calcium phosphate ceramic immersed in simulated body fluid, simulating the human body environment. The pH changes of the porous ceramic particles prepared by the present invention tended to be stabilized after 80 hours, indicating that the degradation and deposition reached equilibrium.

[0063] The ion concentrations of the simulated body fluid (SBF) were nearly equal to those of blood plasma. The SBF was prepared by dissolving reagent grade NaCl (8.035 g/L), NaHCO.sub.3 (0.355 g/L), KCl (0.225 g/L), K.sub.2HPO.sub.4.3H.sub.2O (0.231 g/L), MgCl.sub.2.6H.sub.2O (0.311 g/L), CaCl.sub.2 (0.292 g/L), and Na.sub.2SO.sub.4 (0.072 g/L) in distilled water. The solution was buffered at pH 7.4 with tris(hydroxylmethyl)aminomethane ((CH.sub.2OH).sub.3CNH.sub.2) and 1 M hydrochloric acid (HCl) at 36.Math.5±1 degrees.

[0064] As shown in FIG. 8, FESEM images of the porous biphasic calcium phosphate ceramic after being immersed in SBF for 7 days were shown. After the porous ceramic particles prepared by the present invention were immersed in simulated body fluid for 7 days, apatite was deposited on the surface, which could be used for bone tissues to form bonding, and the material prepared by the present invention had biological activity.

EXAMPLE 4: MTT Assay

[0065] The cytotoxicity assay was performed according to the regulation of ISO10993-5. The sample were extracted for cytotoxic evaluation. The samples (H, H/B, commercial bone graft) were soaked in the medium for 24 hours at the ratio of 0.2 g/mL The samples were further diluted at different ratios (100, 50, 25, 12.5%) and cultured with L929 fibroblasts at 37 degrees for 1 day.

[0066] As shown in FIG. 9, the graph of the cell viability assay (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT) was shown for evaluating cytotoxicity.

[0067] The samples in this experiment were H, H/B, and commercial bone graft, wherein the H sample was water-dissolved oyster shells, the hydroxyapatite was synthesized through the precipitation method for a reaction of 30 min, and after being foamed and sintered at 1300 degrees for 20 minutes, the single-phase porous HA particles were obtained; the H/B sample was acetic-dissolved oyster shells, hydroxyapatite was synthesized through the precipitation method for a reaction of 12 hours, and after being foamed and sintered at 1000 degrees for 25 hours, the porous biphasic apatite particles were obtained; the positive control group was phenol; and the negative control group was aluminum oxide.

[0068] The samples (H, H/B, commercial bone graft) at a ratio of 0.2 g/mL were immersed in a medium for 24 hours of extraction, and diluted the ratio to 100, 50, 25, 12.5%, and were co-cultured with L929 fibroblasts at 37 degrees for 1 day.

[0069] The results of the cytotoxicity test of the porous biphasic calcium phosphate ceramic prepared by the present invention showed that, except for the undiluted samples, no cytotoxicity was found in the remaining dilutions at ratios of 50, 25, and 12.5%.

EXAMPLE 5: Mouse Precursor Stein Cell Culturing

[0070] Osteocyte activity assessment was performed by using D1 mouse precursor stein cells. The samples were extracted at 25% for 24 hours in culture medium, and then D1 mouse precursor stein cells were cultured for 1, 7, and 14 days in the medium.

EXAMPLE 6: WST Assay

[0071] After culturing the D1 mouse precursor stein cell for 1, 7, and 14 days, the absorbance at 450 nm was measured with WST reagent co-culturing for 2 hours. The higher the absorbance, the higher the number of cells are active.

[0072] As shown in FIG. 10, the WST-8 cell viability assay of the mouse precursor stein cells on day 1, day 7, and day 14 were shown, respectively.

[0073] The materials of the experimental group were extracted with 25% medium for 24 hours, the concentration was equivalent to 50 mg/mL, co-cultured with D1 cells for 1, 7, and 14 days, incubated with the WST reagent for 2 hours and then the absorbance was measured at 450 nm.

[0074] For the cell viability of the mouse precursor stein cells, the porous biphasic calcium phosphate ceramic prepared by the present invention was better than the commercial kit on day 14.

EXAMPLE 7: ALP Phosphatase Assay

[0075] The differentiation ability of the osteoblasts was determined by the activity of the alkaline phosphatase. D1 mouse stein cells cultured for 1, 7, and 14 days were used to evaluate the primary bone differentiation ability of the sample extract.

[0076] As shown in FIG. 11, the bone differentiation test of the activity of alkaline phosphatase under fluorescence (Alkaline Phosphatase Assay Kit, ALP) of the D1 mouse precursor stein cells on day 1, day 7, and day 14 were shown, respectively.

[0077] For the bone differentiation activity of the mouse precursor stein cells, the porous biphasic calcium phosphate ceramic prepared by the present invention was better than the commercial kit on day 7.

[0078] While the invention has been described and exemplified in sufficient details for those skilled in this art to make and use it, various alternatives, modifications, and improvements should be apparent without departing from the spirit and scope of this invention.

[0079] One skilled in the art readily appreciates that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The processes and methods for producing them are representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention. Modifications therein and other uses will occur to those skilled in the art. These modifications are encompassed within the spirit of the invention and are defined by the scope of the claims.