Preparation method of 3D printing outer nail covering dressing

Abstract

The invention discloses a preparation method of a 3D printing outer covering nail dressing, which is used for preparing the outer covering nail dressing for nail bed trauma, and comprises the following specific steps: step 1, mixing a thermoplastic biological phase material and an antibacterial material, drying, and carrying out melt extrusion to prepare a composite wire; wherein the thermoplastic biological materials are any two of polylactic acid (PLA), thermoplastic polyurethane (TPU), polycaprolactone (PCL) or polyhydroxyalkanoate (PHA), and the mass ratio of any two thermoplastic biological materials is (3-7): (3-7); the antibacterial material is inorganic salt whiskers, and the mass of the antibacterial material accounts for 0.5 wt%-2wt% of the total mass of the thermoplastic biological material; 2, 3D printing forming is conducted through a fused deposition technology, and the nail covering dressing is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of wound dressings, and particularly to a preparation method of a 3D printed external nail covering dressing. Background Art

[0002] Nail bed trauma caused by nail shedding is common in external force impact, scald or infection. During the recovery process, the exposed nail bed is vulnerable to mechanical friction, bacterial infection and water penetration, resulting in delayed healing or even secondary injury.

[0003] Currently, for nail bed trauma, ordinary medical dressings for skin trauma are usually used for wrapping to provide a certain degree of protection to the nail bed. Since the nail bed is rich in nerve endings and capillaries and is the basic structure for supporting nail growth, any external pressure or friction may cause severe pain or secondary injury; moreover, the nail bears continuous mechanical loads during daily activities (such as grasping and touching), and the dressing needs to adapt to this dynamic pressure to a large extent to prevent dressing displacement or deformation caused by activities. However, the existing dressings for skin trauma are usually very soft. If the mechanical properties of the dressing are insufficient (such as too hard or too soft), it may compress or pull the nail matrix, resulting in new nail deformities (such as spoon nails and longitudinal ridges). Therefore, the traditional dressings in the prior art lack support, have insufficient mechanical properties, are functionally single and cannot meet the individualized treatment needs, and are difficult to fit the nail bed structure and provide effective protection. Summary of the Invention

[0004] Aiming at the above deficiencies existing in the prior art, the purpose of the present invention is to provide a preparation method of a 3D printed external nail covering dressing to solve the problems of lack of support, insufficient mechanical properties, single function and inability to meet the individualized treatment needs in the traditional dressings of the prior art.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A preparation method of a 3D printed external nail covering dressing for preparing an external nail covering dressing for nail bed trauma, the specific steps are as follows:

[0007] Step 1: Mix a thermoplastic biocompatible material and an antibacterial material, and prepare a composite wire through drying and melt extrusion; wherein, the thermoplastic biocompatible material is any two of polylactic acid (PLA), thermoplastic polyurethane (TPU), polycaprolactone (PCL) or polyhydroxyalkanoate (PHA), and the mass ratio of any two thermoplastic biocompatible materials is (3 - 7):(3 - 7); the antibacterial material is inorganic salt whiskers, and calculated by mass percentage, the mass percentage of the antibacterial material in the total mass of the thermoplastic biocompatible material is 0.5wt% - 2wt%;

[0008] Step 2: Use the fused deposition technology for 3D printing and molding to obtain the external nail covering dressing.

[0009] Preferably, in step 1, the thermoplastic biomaterial is PLA and TPU.

[0010] Preferably, the mass ratio of PLA to TPU is 1:1.

[0011] Preferably, the inorganic salt whisker is a magnesium salt whisker.

[0012] Preferably, in step 1, after the thermoplastic biocompatible material and the antibacterial material are mixed, they are extruded to obtain a composite wire under the condition of 120°C to 180°C.

[0013] Preferably, in step 2, the printing temperature is 150°C to 200°C, and the platform temperature is 50°C to 70°C.

[0014] Preferably, in step 2, a three-dimensional modeling of the outer covering nail dressing is designed, and the set parameters are imported into a 3D printer.

[0015] Preferably, in step 2, the molten deposition technology is used to print the dressing layer by layer.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention uses a thermoplastic biocompatible material and an antibacterial material as raw materials, and prepares an external covering nail dressing by 3D printing through a fused deposition modeling technology, so that the antibacterial material is evenly dispersed in the dressing, which can effectively inhibit common pathogenic bacteria such as Staphylococcus aureus and Escherichia coli, and reduce the risk of infection; at the same time, the prepared dressing has certain flexibility and tensile strength, so that the dressing can replace the nail to bear continuous mechanical loads during daily activities (such as grasping and touching), better adapt to this dynamic pressure, prevent the displacement or deformation of the dressing caused by activities, and effectively protect the fragile nail bed from external force impact.

[0018] 2. The present invention can reproduce the unique shape of the patient's nail bed through 3D printing technology, realize the seamless fit of the dressing and the wound surface, avoid the frictional damage caused by the edge warping of the traditional dressing due to the fixed shape, and make the patient more comfortable to use; at the same time, the dressing prepared by the present invention has good biocompatibility, the cell survival rate > 95%, avoiding foreign body rejection reactions; it also has a degradation ability, can be degraded into carbon dioxide and water under natural conditions, and reduces medical waste pollution. Description of the Drawings

[0019] Figure 1 It is a flow chart of the preparation method described in the present invention.

[0020] Figure 2 It is an element distribution diagram of the dressings prepared in Example 1 and Comparative Example 1; among them, a is Example 1, and b is Comparative Example 1.

[0021] Figure 3 Mechanical property diagrams of composite materials obtained by 3D printing of wires prepared in different TPU / PLA mixing ratios; a is a schematic diagram of tensile test, b is the change of tensile strength of composite materials obtained by 3D printing with different TPU / PLA mixing ratios, and c is the change of Shore hardness of composite materials obtained by 3D printing with different TPU / PLA mixing ratios.

[0022] Figure 4 Result diagrams of tensile tests for Example 1, Examples 5 - 7 and Comparative Examples 1 - 4; a is Young's modulus, b is tensile strength, c is elongation at break, d is the stress-strain diagram of Example 1, Examples 5 - 7, and e is the stress-strain diagram of Comparative Examples 1 - 4.

[0023] Figure 5 Result diagrams of fatigue tests for Example 1, Examples 5 - 7 and Comparative Examples 1 - 4.

[0024] Figure 6 Diagram of the degradation of Example 1, TPU and PLA.

[0025] Figure 7 Effect diagram of the release of magnesium salt whiskers from the dressing prepared in Example 1; among them, a is the standard absorbance curve of phosphate radicals, and b is the linear diagram of the change of the release mass of magnesium salt whiskers with time during the degradation of Example 1. Detailed implementation manners

[0026] The present invention will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the present invention belong to the scope of protection of the present invention.

[0027] Unless otherwise specified in specific circumstances in the present invention, the numerical ranges listed herein include the upper and lower limit values, as well as all integers and fractions within this range, rather than the specific values listed when defining the range.

[0028] I. A preparation method of a 3D printed external nail dressing

[0029] The method of the present invention is used to prepare an external nail dressing for nail bed trauma, and the specific steps are as follows:

[0030] Step 1: Mix the thermoplastic biocompatible material with the antibacterial material, and prepare a composite wire through drying and melt extrusion; wherein, the thermoplastic biocompatible material is any two of polylactic acid (PLA), thermoplastic polyurethane (TPU), polycaprolactone (PCL) or polyhydroxyalkanoate (PHA), and the mass ratio of any two thermoplastic biocompatible materials is (3-7):(3-7); the antibacterial material is inorganic salt whiskers, and calculated by mass percentage, the mass of the antibacterial material accounts for 0.5wt% - 2wt% of the total mass of the thermoplastic biocompatible materials;

[0031] Step 2: Use the fused deposition technology for 3D printing and molding to obtain the external nail dressing.

[0032] When studying the dressing for nail bed trauma in the present invention, it is found that since the nail bed is rich in nerve endings and capillaries and is the basic structure supporting the growth of nails, any external pressure or friction may cause severe pain or secondary injury; moreover, the nail bears continuous mechanical loads during daily activities (such as grasping and touching), and the dressing needs to adapt to this dynamic pressure to a large extent to prevent the displacement or deformation of the dressing caused by activities. The existing technology lacks a special dressing for nail bed trauma and often directly uses a medical dressing for skin trauma for wrapping. Although this skin trauma dressing has sufficient water absorption, it often lacks sufficient mechanical properties. If the mechanical properties of the dressing are insufficient (such as too hard or too soft), it may compress or pull the nail matrix, resulting in deformities of the new nail (such as spoon nails and longitudinal ridges). Therefore, the present invention conceives to use 3D printing technology to prepare the dressing. Although 3D printing technology can meet the requirements for the shape of the special dressing for nail bed trauma and make the printed dressing fit the patient's nail bed better, it was originally expected that the dressing prepared by 3D printing technology was likely to be inferior to the dressing prepared by the hot pressing method in terms of mechanical strength. Therefore, the present invention has conducted in-depth research on both methods and unexpectedly found that the dressing prepared by 3D printing technology is actually significantly superior to the dressing formed by hot pressing in terms of mechanical properties, which is completely beyond the expectation of the present invention. Therefore, the present invention further optimizes the 3D printing technology and finds that by controlling the types and ratios of thermoplastic biocompatible materials, the hardness of the external nail dressing prepared can be closest to that of the human nail, effectively achieving the balance of the hardness and tensile strength of the dressing material and avoiding the adverse effects on the nail bed trauma caused by the dressing being too hard or too soft.

[0033] In some embodiments of the present invention, the thermoplastic biomaterial is preferably PLA and TPU. In the combined experiments of four materials, namely polylactic acid (PLA), thermoplastic polyurethane (TPU), polycaprolactone (PCL), and polyhydroxyalkanoate (PHA), after any combination of these four materials, the mechanical strength of the dressings obtained by 3D printing is better than that of the dressings prepared by hot pressing. However, considering the hardness closest to that of human nails, the combination of PLA and TPU has a better effect. Therefore, the mass ratio of PLA to TPU can be 3:7, 4:6, 5:5, 6:4, or 7:3, or within the numerical range formed by any two of the above specific values as endpoints; it should be understood that in the implementation scheme, any of the above ranges can be combined with any other range.

[0034] In some embodiments of the present invention, the inorganic salt whisker is a magnesium salt whisker, specifically magnesium phosphate whisker. The present invention finds that in the dressings prepared by the hot pressing process, the magnesium salt whiskers show an aggregation phenomenon, which leads to a more concentrated and disordered distribution of the magnesium salt whiskers in the dressings, seriously affecting the overall performance of the dressings, especially in terms of mechanical properties and stability. For the two techniques of 3D printing technology and hot pressing technology, the effects brought about by the change in the amount of magnesium salt whiskers are also very different. For the hot pressing technology, the change in the amount of magnesium salt whiskers has little effect on the two properties of Young's modulus and tensile strength, while in terms of the property of elongation at break, the effect brought about by the change in the amount of magnesium salt whiskers is more obvious compared with 3D printing technology. For 3D printing technology, the change in the amount of magnesium salt whiskers has a more obvious effect on the properties of the dressings. Therefore, the amount of magnesium salt whiskers can be 0.5 wt%, 1 wt%, 1.5 wt%, or 2 wt%, or within the numerical range formed by any two of the above specific values as endpoints; it should be understood that in the implementation scheme, any of the above ranges can be combined with any other range.

[0035] In some embodiments of the present invention, in step 1, the thermoplastic biocompatible material and the antibacterial material are mixed and then extruded at 120°C to 180°C to obtain a composite wire. If the extrusion temperature is too high, it will be difficult for the material to form a wire; if the extrusion temperature is too low, the wire extrusion is limited, and the extruded material cannot be completely melted, resulting in poor wire quality and being unable to be used for 3D printing. Therefore, the extrusion temperature can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C, or within the numerical range formed by any two of the above specific values as endpoints; it should be understood that in the implementation scheme, any of the above ranges can be combined with any other range.

[0036] In some embodiments of the present invention, in step 2, the printing temperature is 150°C to 200°C, and the platform temperature is 50°C to 70°C. If the printing temperature is too low, the dressing cannot be formed; however, if the printing temperature is too high, the material will degrade and even carbonize. Therefore, the printing temperature can be 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, or a numerical range formed by any two of the above specific values as endpoints; the platform temperature can be 50°C, 60°C or 70°C, or a numerical range formed by any two of the above specific values as endpoints; it should be understood that in the implementation scheme, any of the above ranges can be combined with any other range.

[0037] In some embodiments of the present invention, in step 2, a three-dimensional modeling of the outer covering nail dressing is designed and the set parameters are imported into the 3D printer. The three-dimensional modeling can be carried out according to the scanned data of the patient's nail bed, so that the shape of the dressing fits the patient's nail bed more closely.

[0038] In some embodiments of the present invention, in step 2, the dressing is printed layer by layer using the fused deposition technology. Specifically, two forming methods, namely, staggered nozzles and layered stacking, can be used, and both of these two forming methods can realize layer-by-layer printing of the dressing.

[0039] II. Examples and Comparative Examples

[0040] Example 1

[0041] Step 1: Select polylactic acid (PLA) and thermoplastic polyurethane (TPU) as the base materials for the outer covering nail dressing. Before mixing the raw materials, first place the polylactic acid (PLA) and thermoplastic polyurethane (TPU) powders in a vacuum oven at 60°C for drying treatment for 12 hours to ensure sufficient removal of moisture. After drying, mix PLA, TPU and magnesium salt whiskers, and then use a stirrer to uniformly mix the components for 3 minutes to ensure uniform distribution of the materials. After mixing, sieve the mixture through a 100-mesh sieve to finally obtain a uniform mixed powder. Next, using a 3DPANY extruder, extrude and form the above mixed powder under the conditions of an extrusion temperature of 150°C and a screw rotation speed of 5 r / min to prepare a PLA / TPU / magnesium salt whisker composite filament for 3D printing. The mass ratio of TPU to PLA is 1:1. Calculated by mass percentage, the dosage of TPU is 50 wt%, the dosage of PLA is 50 wt%, and the dosage of magnesium salt whiskers is 1 wt%.

[0042] Step 2: 3D printing and forming: Using the fused deposition modeling technology (FDM), set the printing temperature at 150 °C and the platform temperature at 60 °C. Layer by layer, print the outer covering of the armor dressing with the composite wire in a 3D printer. Use 200-mesh sandpaper to polish the inner side of the outer covering of the armor dressing, and paste medical double-sided pressure-sensitive tape.

[0043] Example 2

[0044] Based on Example 1, make adjustments. The difference is that the mass ratio of TPU to PLA is 3:7. Calculated by mass percentage, the dosage of TPU is 30 wt%, and the dosage of PLA is 70 wt%. Other steps are exactly the same as those in Example 1.

[0045] Example 3

[0046] Based on Example 1, make adjustments. The difference is that the mass ratio of TPU to PLA is 4:6. Calculated by mass percentage, the dosage of TPU is 40 wt%, and the dosage of PLA is 60 wt%. Other steps are exactly the same as those in Example 1.

[0047] Example 4

[0048] Based on Example 1, make adjustments. The difference is that the mass ratio of TPU to PLA is 3:7. Calculated by mass percentage, the dosage of TPU is 70 wt%, and the dosage of PLA is 30 wt%. Other steps are exactly the same as those in Example 1.

[0049] Example 5

[0050] Based on Example 1, make adjustments. The difference is that the dosage of magnesium salt whiskers is 0.5 wt%. Other steps are exactly the same as those in Example 1.

[0051] Example 6

[0052] Based on Example 1, make adjustments. The difference is that the dosage of magnesium salt whiskers is 1.5 wt%. Other steps are exactly the same as those in Example 1.

[0053] Example 7

[0054] Based on Example 1, make adjustments. The difference is that the dosage of magnesium salt whiskers is 2 wt%. Other steps are exactly the same as those in Example 1.

[0055] Comparative Example 1

[0056] Adjusted on the basis of Example 1, the difference being: After obtaining uniform mixed powder through a mesh sieve, using a hot pressing mold with specifications of 20 cm × 20 cm × 1 mm, evenly spread the above-mentioned mixed powder on the surface of the mold. In a hot press, set the hot pressing temperature to 150 °C, the pressure to 1.0 MPa, and the hot pressing time to 10 min for hot pressing forming. Other steps are exactly the same as those in Example 1.

[0057] Comparative Example 2

[0058] Adjusted on the basis of Comparative Example 1, the difference being: The dosage of magnesium salt whiskers is 0.5 wt%. Other steps are exactly the same as those in Comparative Example 1.

[0059] Comparative Example 3

[0060] Adjusted on the basis of Comparative Example 1, the difference being: The dosage of magnesium salt whiskers is 1.5 wt%. Other steps are exactly the same as those in Comparative Example 1.

[0061] Comparative Example 4

[0062] Adjusted on the basis of Comparative Example 1, the difference being: The dosage of magnesium salt whiskers is 2 wt%. Other steps are exactly the same as those in Comparative Example 1.

[0063] III. Performance Analysis

[0064] 1. Energy Dispersive Spectrometer (EDS) Characterization

[0065] Perform elemental mapping tests on the dressings prepared in the examples and comparative examples to analyze the distribution of each element in the dressings. Calibrate and analyze the C and Mg elements of the outer covering A dressing, where the C element represents PLA and TPU, and the Mg element represents magnesium salt whiskers.

[0066] The results are as Figure 2As shown, the element distribution map clearly shows the differences between the examples and the comparative examples. Specifically, the element distribution in the 3D printed composite material is more uniform than that in the hot press formed material, which means that the dispersion of magnesium salt whiskers in the 3D printed material is better and more uniform. This phenomenon indicates that the composite material prepared by 3D printing has a more consistent composition distribution inside the material, which can effectively avoid the performance fluctuations that may be caused by uneven composition distribution. In contrast, the material of the comparative example prepared by hot press forming shows the aggregation of magnesium salt whiskers, resulting in a more concentrated and disordered distribution of magnesium salt whiskers in the material. This non-uniform distribution will affect the overall performance of the material, especially in terms of the mechanical properties and stability of the material. The main reason for this difference lies in the different preparation methods: before processing the hot press formed material, it needs to be mixed by a mixer and then formed by hot press treatment. This process often leads to an uneven distribution of magnesium salt whiskers in the material, forming relatively concentrated areas. While 3D printing can better control the uniformity and dispersion of the material by extruding the heated and mixed wire, thus improving the overall consistency and performance of the material.

[0067] 2. Influence of Different TPU / PLA Mixing Ratios on Mechanical Properties

[0068] Wires were made using different TPU / PLA mixing ratios (calculated based on PLA, with the PLA dosages being 30wt%, 40wt%, 50wt%, 60wt% and 70wt% respectively), and composite materials were made by 3D printing to adjust their mechanical properties. The size of the specimens was 50×10×1 mm (length×width×thickness), and uniaxial tensile tests were carried out as Figure 3 shown in Figure 3As shown in Figures 2b and 3c, the tensile strength of TPU is approximately 5.24 MPa, while that of PLA is approximately 13.31 MPa. The hardness values are 69 HD for TPU and 91 HD for PLA. As the proportion of PLA increases from 30% to 70%, the tensile strength of the TPU / PLA mixture steadily increases from 6.31 MPa to 10.52 MPa, while the Shore hardness increases from 74 HD to 86 HD. However, considering that the dressing of the present invention is a special dressing for nail bed trauma, the strength of the dressing should be close to that of the nail. Because if the strength of the dressing is lower than that of the nail, it may rupture under joint movement or external force, resulting in the exposure or infection of the wound surface; moreover, insufficient mechanical strength may cause the structure of the dressing to disintegrate after absorbing water and be unable to maintain a moist environment; for example, although calcium alginate dressings have strong water absorption, they rely on their gel strength to maintain integrity; however, the mechanical properties of the dressing need to be compatible with the regenerating tissue and cannot inhibit the dynamic repair process at the nail bed trauma site. A dressing with too high rigidity will limit the micro-movement requirements of the nail bed tissue, affecting cell migration and angiogenesis; it will also cause the dressing to adhere too tightly to the wound surface, causing secondary damage to the patient when removed. Therefore, the Shore hardness of the nail is around 80 HD, and the 50% PLA / TPU ratio closest to the nail hardness is selected to prepare the outer nail dressing.

[0069] 3. Tensile Tests of Examples and Comparative Examples

[0070] Tensile tests were respectively carried out on Examples 1, 5 - 7 and Comparative Examples 1 - 4, and the results are as Figure 4 shown. Generally speaking, the Young's modulus and tensile strength of the examples are far superior to those of the comparative examples. This result is beyond the prediction of the present invention and also shows that the 3D printing technology can make the internal structure of the dressing more stable, significantly improve the performance of the dressing in resisting external tensile forces, and thus effectively enhance the wall strength and durability of the dressing. Although the data of the examples in terms of elongation at break are not as good as those of the comparative examples, this is also an adjustment based on its use as a nail bed trauma dressing, because too high an elongation at break is usually accompanied by a decrease in the rigidity of the material (as Figure 4 shown in Figures 4a and 4b). The comparative examples are far inferior to the examples in terms of Young's modulus and tensile strength, which will make the dressing unable to provide stable support for nail bed regeneration, and such a high elongation at break of the comparative examples will cause excessive swelling after absorbing water, resulting in an increase in the volume of the dressing and curling at the edges, which will instead damage the wound microenvironment. The nail bed is located at the fingertip and needs to withstand frequent micro-movements (such as grasping). An ideal dressing should have both moderate ductility (to adapt to activities) and tear resistance (to prevent rupture). The elongation at break of the nail bed dressing should be moderate, and the dressing prepared by the examples can well meet this requirement.

[0071] Specifically, for 3D printing technology, with the increase in the amount of magnesium salt whiskers, the Young's modulus, tensile strength and elongation at break of the dressing all showed a downward trend. This shows that even in 3D printing technology, magnesium salt whiskers cannot be more evenly distributed in the amorphous continuous phase formed by PLA and TPU during the hot melt process. The increase in the amount of magnesium salt whiskers will destroy the cross-linked structure formed between PLA and TPU, thereby affecting the overall mechanical properties of the dressing.

[0072] For hot pressing molding technology, the increase in the amount of magnesium salt whiskers will only have a more obvious effect on the elongation at break of the dressing. This shows that no matter which molding technology is used, magnesium salt whiskers will have a certain destructive effect on the cross-linked structure formed between PLA and TPU.

[0073] 4. Fatigue Tests of Examples and Comparative Examples

[0074] The tensile tests were performed on Examples 1, 5 to 7 and Comparative Examples 1 to 4, and the results are as follows: Figure 5 As shown, the dressings prepared by the embodiment and the comparative example showed different degrees of stress fatigue in the fatigue test. In the initial stage of the test, the tensile stress of the two was almost the same, both maintained at about 6.8MPa, and the difference was not obvious, which shows that the dressings prepared by 3D printing and hot pressing molding in the early stage have similar tensile strength. However, with the increase of the test cycle, the embodiment and the comparative example showed very significant differences: after the 10th cycle, the tensile stress of the comparative example showed a very obvious decrease, while this decrease in the embodiment began to appear after the 20th cycle, and the decrease in the embodiment was significantly lower than that in the comparative example, which shows that the comparative example will experience stress relaxation faster than the embodiment. This situation shows that the internal structure degradation and stress concentration of the dressing prepared by hot pressing molding will progress faster and more obviously than the dressing prepared by 3D printing under repeated stress. Moreover, after the 500th cycle, the degradation of the comparative example continued, while that of the example tended to be stable, which indicates that the example can better maintain its mechanical strength and stability after long-term fatigue testing. This also confirms that the beneficial effect of 3D printing technology on the mechanical properties of the dressing is higher than that of hot pressing technology, especially in the face of long-term load and fatigue.

[0075] Throughout the entire fatigue test process, the tensile stresses of the examples and the comparative examples both showed a phenomenon of first increasing and then decreasing. This is because the initial increase in tensile stress is due to the disorder of the crystal structure inside the material. When the initial tensile force is applied to the material, the free chain segments in the material will change, causing the crystal regions to start arranging and optimizing, thus resulting in a temporary increase in stress. As the tensile force continues to increase, when a certain critical threshold is reached, the crystal structure begins to be damaged, leading to the breakdown of the internal ordered arrangement, and at this time the stress of the material begins to decrease. However, in terms of 3D printing technology and thermoforming technology, the tensile stress of the material prepared by thermoforming technology continued to decrease after the 10th cycle, and at the end of the test, this downward trend still existed; but the tensile stress of the material prepared by 3D printing technology began to show a slow downward trend at the 20th cycle, and after the 500th cycle, its tensile stress tended to be stable and there was almost no obvious change. This indicates that for materials with the same composition prepared by different forming processes, due to the differences in the forming processes, there will be obvious differences in the internal structures of the materials, and these differences will cause the materials to exhibit completely different change trends in long-term fatigue tests.

[0076] 5. Degradation performance test of the examples and release test of magnesium salt whiskers

[0077] Taking Example 1 as an example, the degradation performance tests were carried out with pure PLA and pure TPU. Example 1, PLA, and TPU were immersed in a 20 wt% hydrogen peroxide solution and treated in a constant temperature environment of 37 °C to simulate the oxidative degradation process in the living body, and the degradation conditions of the three materials at 1, 2, 5, 7, 10, and 15 days were recorded. As Figure 6As shown, after 15 days of oxidative degradation, the morphologies of PLA and TPU did not change significantly, showing strong oxidation resistance and indicating their stability in an oxidative environment. However, for Example 1, the degradation process was significantly different. Starting from the 5th day, degradation occurred in Example 1, and after 15 days, the complete disk sample had completely decomposed into powder, far less than the degradation time of the PLA alone material, which usually takes more than 30 days to initially degrade. This phenomenon indicates that the addition of magnesium salt whiskers significantly accelerated the degradation process of the dressing. The polymer chains of TPU are easily broken under high temperature and oxidative conditions; PLA undergoes dehydrogenation reactions in an oxidative environment, releasing hydrogen ions, which not only cause the PLA molecular chains to break but also further damage the TPU molecular chains; during the 3D printing process, the addition of magnesium salt whiskers interfered with the molecular folding and crystallization processes of the TPU and PLA polymers, thus changing the microstructure of the PLA / TPU composite material and accelerating the degradation process of the dressing, making it more suitable for short-term use scenarios. For nail bed trauma, the wound care period is approximately 1 to 3 months. On the premise of regularly changing the outer nail dressing, the degradation rate of Example 1 is suitable for the growth of nails.

[0078] The present invention uses phosphate ions as an indicator. Magnesium salt whiskers usually have Mg 2+ as the central ion and may combine with phosphate (PO4 3- ) to form a magnesium phosphate salt structure (such as calcium magnesium phosphate, etc.). Therefore, when the whiskers dissolve, the release amount of phosphate is positively correlated with the release amount of magnesium ions. Thus, by quantifying the concentration of phosphate ions, the release amount of magnesium salt whiskers can be reflected. As Figure 7 shown, it can be seen that the release of magnesium salt whiskers began to gradually increase on the 5th day and reached the peak of release on the 15th day, which is highly consistent with the degradation process of the dressing. Specifically, as the outer nail dressing degrades, the magnesium salt whiskers gradually release from the dressing, indicating that the release of magnesium salt whiskers is synchronized with the degradation of the composite material. Rapid degradation can not only meet the strict requirements of biomedical materials for environmental friendliness and degradability but also effectively promote the release of the antibacterial agent magnesium salt whiskers embedded in the composite material, thereby enhancing its antibacterial performance. This characteristic is crucial for materials applied in the biomedical field, especially in those cases where active ingredients need to be gradually released during use. This result provides a new idea for the development of more efficient biomedical materials, especially in application scenarios that require rapid release of antibacterial agents in the short term, such as wound dressings, antibacterial wrapping materials, etc. By further optimizing the degradation rate and antibacterial agent release characteristics of the composite material, more precise control can be achieved to meet different clinical needs.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Those of ordinary skill in the art should understand that any modifications or equivalent replacements made to the technical solutions of the present invention without departing from the purpose and scope of the present technical solutions shall be covered by the scope of the claims of the present invention.

Claims

1. A preparation method of a 3D printed external armor dressing, characterized in that, Prepare an outer nail dressing for nail bed trauma, and the specific steps are as follows: Step 1: Mix a thermoplastic biocompatible material with an antibacterial material, and prepare a composite wire through drying and melt extrusion; wherein, the thermoplastic biocompatible material is any two of polylactic acid (PLA), thermoplastic polyurethane (TPU), polycaprolactone (PCL), or polyhydroxyalkanoate (PHA), and the mass ratio of any two thermoplastic biocompatible materials is (3-7):(3-7); the antibacterial material is inorganic salt whiskers, and calculated by mass percentage, the mass percentage of the antibacterial material in the total mass of the thermoplastic biocompatible material is 0.5wt% - 2wt%; Step 2: Use the fused deposition technique for 3D printing and molding to obtain the outer nail dressing.

2. The preparation method according to claim 1, characterized in that, In Step 1, the thermoplastic biocompatible material is PLA and TPU.

3. The preparation method according to claim 2, wherein The mass ratio of PLA and TPU is 1:

1.

4. The preparation method according to claim 1, wherein The inorganic salt whiskers are magnesium salt whiskers.

5. According to the preparation method described in claim 1, characterized in that, In Step 1, after the thermoplastic biocompatible material and the antibacterial material are mixed, they are extruded at 120°C - 180°C to obtain a composite wire.

6. The preparation method according to claim 1, wherein In Step 2, the printing temperature is 150°C - 200°C, and the platform temperature is 50°C - 70°C.

7. According to the preparation method described in claim 1, characterized in that, In Step 2, design the three-dimensional modeling of the outer nail dressing and import the set parameters into the 3D printer.

8. According to the preparation method described in claim 1, wherein, In Step 2, use the fused deposition technique to print the dressing layer by layer.

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