Laser selective preparation of shape-controlled hydrogel knee implant prosthesis

Abstract

The present invention provides a laser-selectively prepared, shape-controlled hydrogel knee implant prosthesis, comprising a hydrogel knee implant prosthesis body, the outer contour, thickness, and surface curvature of which are obtained by removing a universal hydrogel block by ultraviolet laser etching; the upper surface of the prosthesis body is provided with microgrooves and microprotrusions formed by laser etching; the lower surface is provided with a micropit structure on the order of 10 microns, the micropit structure comprising a plurality of periodically arranged circular micropits or polygonal micropits; the surfaces formed by laser etching of the microgrooves, microprotrusions, and micropits on the upper surface and the micropits on the lower surface have different porosities. The present invention utilizes short-wavelength laser etching to form different microstructures on the surface of the hydrogel, achieving different adhesion friction properties on different surfaces and regulating the friction coefficient of different areas on the same surface; at the same time, it has the characteristics of anti-fouling, promoting cell attachment, and increasing service life, greatly improving the tribological properties of cartilage and its adaptability to use in complex environments.

Description

Technical Field

[0001] The present invention belongs to the field of hydrogel plastic surgery, and in particular relates to a hydrogel knee joint implant prosthesis selectively prepared by laser with shaped properties controlled. Technical Background

[0002] Hydrogels are three-dimensional polymer networks formed by chemical or physical crosslinking of hydrophilic polymers. Hydrophilic groups on the polymer chains within the hydrogel interact with water molecules through hydrogen bonds, connecting them within the network. Hydrophobic groups swell when exposed to water, making hydrogels similar to natural cartilage in terms of porosity, hydrophilicity, and tribological properties, making them a perfect replacement for articular cartilage. Furthermore, hydrogels possess physical and chemical properties similar to the three-dimensional microenvironment of the extracellular matrix, demonstrating excellent biocompatibility and enabling the regulation of cell behavior and tissue function. Due to their similar tribological properties to natural cartilage, they have become a perfect replacement for articular cartilage.

[0003] Before cross-linking, hydrogels are in a fluid state, and their macromorphology and surface micromorphology are often formed through molds. Once formed, due to their soft material and low phase transition temperature characteristics, traditional mechanical processing methods are difficult to perform secondary processing. In addition, the cost of mold manufacturing is very high. Due to the inherent differences in the shapes of human bones and cartilage, molds have to be customized individually, which greatly increases manufacturing costs. In addition, due to the requirements of the working environment of articular cartilage, the same hydrogel often faces different material friction substrates and gradual contact stresses, which makes hydrogels difficult to use in complex working environments. In tribological research, whether it is hard or soft materials, the surface topology plays an important role in regulating friction and adhesion. However, the hydrogel precursor has poor fluidity, and the surface micromorphology formed by molds is less regular and reproducible, making it difficult to achieve the expected friction stress regulation effect. In addition, materials transplanted into the human body will inevitably come into contact with the body's internal fluid environment. Proteins, biological factors and cells in the body fluid will attach to and aggregate on the surface of the material and secrete other metabolites on the surface of the material, causing further contamination and producing adverse reactions such as bacterial inflammation, immune rejection and abnormal regulation of prosthetic friction properties. Summary of the Invention

[0004] The purpose of the present invention is to provide a hydrogel knee joint implant prosthesis with laser selective preparation and shape control. The hydrogel knee joint implant prosthesis is prepared by macromorphology modification and microstructure regionalization based on short-wavelength laser etching, which can solve the problems of high customization cost of existing hydrogel molds and single application scenarios of hydrogel prostheses.

[0005] The technical solutions of the present invention are as follows:

[0006] A laser selectively prepared shape-controlled hydrogel knee joint implant prosthesis comprises a hydrogel knee joint implant prosthesis body, wherein the outer contour, thickness and surface curvature of the hydrogel knee joint implant prosthesis body are obtained by ultraviolet laser etching and removing a universal hydrogel block;

[0007] The universal hydrogel block is obtained by pouring a hydrogel precursor solution into a universal mold and then undergoing a cross-linking reaction;

[0008] The upper surface of the hydrogel knee joint implant body is provided with a microstructure formed by laser etching; the upper surface refers to the surface facing the joint cavity; the microstructure includes microgrooves and microprotrusions, the microgrooves are 1-5 microns wide and connected to the outside world, and the microprotrusions are in the shape of quadrangular pyramids with a side length of 80-120 microns, a height of 1-5 microns, and a microstructure period of 81-125 microns.

[0009] The lower surface of the hydrogel knee joint implant body is provided with a micro-pit structure of the order of 10 microns formed by laser etching. The micro-pit structure includes a plurality of periodically arranged circular or polygonal micro-pits. The micro-pit size in the area of ​​contact and friction with the meniscus is larger than the micro-pit size in the area of ​​contact and friction with the patella. The lower surface refers to the surface facing away from the joint cavity. Micro-pits of different shapes have different friction coefficients, and the friction coefficient is adjusted by a combination of the shape and size parameters of the micro-pit structure.

[0010] The surfaces formed by laser etching of microgrooves and microprotrusions on the upper surface and micropits on the lower surface of the hydrogel knee joint implant prosthesis body have different porosities.

[0011] Compared with existing knee joint prostheses, the present invention has the following advantages:

[0012] (1) Based on the laser selective preparation of hydrogel implant prostheses with shape-controlled microstructures, the high energy of short-wavelength laser single photons can be used to directly break the chemical bonds of the surface material during the processing of the hydrogel, so that the atoms and atomic clusters in the material are separated from the material body, achieving the purpose of directional removal; and the heat generated during the entire processing process is relatively small, and the hydrogel will not undergo phase change. The hydrogel is formed in a universal mold, and then the macroscopic morphology of the hydrogel is trimmed to adapt to the individual size and shape of the cartilage through multiple high-power scans, effectively avoiding the cost increase caused by customized molds.

[0013] (2) The present invention utilizes short-wavelength laser to etch the hydrogel surface to form different microstructures, thereby achieving different adhesion friction properties on different surfaces and regulating the friction coefficient in different areas of the same surface; at the same time, it has the characteristics of anti-fouling, promoting cell attachment and increasing service life; it greatly improves the tribological properties of cartilage and its adaptability to use in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the micro-pit structure of the hydrogel knee implant for selective laser fabrication of shape-controlled prosthesis;

[0015] Figure 2 Structural diagram of a hydrogel knee implant with shape-controlled selective laser fabrication. DETAILED DESCRIPTION

[0016] The present invention provides a laser selectively prepared shape-controlled hydrogel knee joint implant prosthesis, comprising a hydrogel knee joint implant prosthesis body, wherein the outer contour, thickness and surface curvature of the hydrogel knee joint implant prosthesis body are obtained by ultraviolet laser etching and removing a universal hydrogel block;

[0017] The universal hydrogel block is obtained by pouring a hydrogel precursor into a universal mold and then undergoing a cross-linking reaction; the universal mold can be of any shape, such as a rectangular groove.

[0018] The upper surface of the hydrogel knee implant prosthesis body (the surface facing the joint cavity) is provided with a microstructure formed by laser etching; the microstructure includes microgrooves and microprotrusions, the microgrooves are 1-5 microns wide, the microgrooves are connected to the outside world, and the microprotrusions are in the shape of a quadrangular pyramid with a side length of 80-120 microns, a pyramid height of 1-5 microns, and a microstructure period of 81-125 microns.

[0019] The lower surface of the hydrogel knee implant (the surface facing away from the joint cavity) is laser-etched with a 10-micron micro-pit structure. This structure comprises a periodic arrangement of circular or polygonal pits. The pits in the area of ​​contact with the meniscus are larger than those in the area of ​​contact with the patella. Different pit shapes have different friction coefficients, which are adjusted primarily by combining the shape and size parameters of the pit structure.

[0020] Figure 1 The figure shows a schematic diagram of the micro-pit structure. The radius of the circular micro-pit in the area of ​​contact and friction with the meniscus is 74.2 microns, the radius of the circular micro-pit in the area of ​​contact and friction with the patella is 49 microns, and the micro-pit spacing is 200 microns. The above micro-pit structure is formed by ultraviolet laser at an energy density of 510J / cm 2 It is formed by scanning back and forth line by line under the laser parameters of 84.1% spot overlap and 5 micron scanning spacing.

[0021] According to measurements, the friction shear stress on the smooth hydrogel surface is about 200Pa, the friction shear stress on the surface of micro-circular pits with a radius of 49 microns is about 150Pa, and the friction shear stress on the surface of micro-circular pits with a radius of 74.2 microns is about 60Pa.

[0022] The knee cartilage is in contact and friction with the meniscus and patella at the same time. The difference in micro-pit structure can change the lubrication performance of the fluid in the micro-pit on the friction interface, reducing the friction force in the contact area with severe wear, thereby increasing the service life of the artificial cartilage friction interface.

[0023] By controlling different laser parameters (energy density, spot overlap, and scanning spacing), the hydrogel microgrooves, microbumps, and micropits produced by laser-irradiated hydrogel regions have different porosities. Therefore, the rate of aqueous solution seepage from the hydrogel microstructure under compressive friction conditions can be controlled by laser parameters, thereby further fine-tuning its lubrication properties.

[0024] In addition, the size of the micropits is on the order of 10 microns, which is the size of chondrocytes, which is conducive to the attachment of chondrocytes to the micropits and provides good conditions for the hydrogel regeneration of articular cartilage.

[0025] Figure 2 The figure shows the main structure of the hydrogel knee joint implant prosthesis. Its upper surface (the surface facing the joint cavity) contacts human bones or implanted titanium alloy prostheses, which requires strong adhesion. The micro-grooves and micro-protrusion structures formed by laser etching provided in the present invention can provide good adhesion, which can effectively increase the friction with human / titanium alloy bones, and the micro-grooves between the protrusions can prevent cells from adhering to other pollutants, playing a long-term anti-slip role. The lower surface (the surface facing away from the joint cavity) contacts cartilage or artificial cartilage, which requires a low friction coefficient and good conditions for chondrocyte attachment and regeneration. The present invention is provided with a micro-pit structure of the order of 10 microns formed by laser etching, which can accurately regulate the friction of the hydrogel surface, and the micro-pits are conducive to the attachment of chondrocytes, promote the regeneration of chondrocytes on the hydrogel surface, and can be used to customize the friction performance of hydrogels in complex working environments.

[0026] The method for preparing the above-mentioned laser selectively prepared shape-controlled hydrogel knee joint implant prosthesis is as follows:

[0027] Step (1): preparing the macroscopic morphology of the hydrogel;

[0028] (1.1) Preparation of preliminary macroscopic morphology of hydrogel blocks:

[0029] First, a 12% mass fraction of polyvinyl alcohol (PVA) particles and water were weighed using an electronic scale to form an aqueous solution. The aqueous solution was then heated and stirred at 90°C for one hour using a magnetic stirrer to dissolve the PVA particles in the water. The PVA solution was then injected into a universal cartilage mold (rectangular recess: 25×20×2 cm) using a syringe. The mold containing the PVA solution was then placed in a -40°C refrigerator for 16 hours for crosslinking, followed by thawing and thawing in a constant temperature chamber at 21°C for eight hours, and three freeze-thaw cycles were repeated. Finally, the formed hydrogel blocks were placed in distilled water and allowed to swell for seven days until the hydrogel absorbed water and the stretching force between the crosslinked segments was equal to the elastic retraction force of the network.

[0030] (1.2) Preparing the contour curve of the hydrogel prosthesis and adjusting the thickness and surface curvature of the hydrogel prosthesis:

[0031] The contours of the hydrogel prosthesis are etched by laser according to the designed route. The short wavelength and high single-photon energy of a 355-nanometer ultraviolet laser directly break the chemical bonds of the surface material during the hydrogel processing, separating atoms and atomic clusters from the bulk of the material and achieving targeted removal.

[0032] The hydrogel block is placed on the XYZ processing platform, and the laser spot is focused on the hydrogel surface by continuously adjusting the Z axis of the processing platform to rise and fall; then, the hydrogel block is moved to the area to be processed by adjusting the XY axis; finally, the processing program is started, and the laser focus is scanned on the hydrogel block according to the pre-designed trajectory according to the required requirements. The laser energy density is 605J / cm 2 The spot overlap area is 94.1%. After each scan, the processing platform is raised by 50 microns so that the focus is on the bottom of the etched micro-grooves for the next etching, until the entire hydrogel is cut through, thus completing the etching and cutting of the contour curve of the hydrogel prosthesis. The side profile of the hydrogel prosthesis is similar to the contour of the knee cartilage, and the side is arc-shaped (arc radius: 5-20cm). Figure 2 As shown, this shape can wrap the human bone / titanium alloy bone well, preventing the bone from directly and violently wearing against the meniscus or patella.

[0033] The thickness and surface curvature of the hydrogel prosthesis are regulated by etching and removing the local area layer by layer using a grid as a scanning track. The grid spacing is smaller than the spot diameter to achieve uniform surface removal. The thickness of the prosthesis can also be regulated by changing the laser energy density and the spot overlap rate. In areas where the prosthesis is designed to be thinner (2-3mm), a large amount of hydrogel prosthesis is removed through high energy density, spot overlap rate and multiple scans. The laser parameter for removing a layer thickness of 0.5 microns in a single scan is 210J / cm 2Energy density, 50% spot overlap and 5 micron scanning distance. The laser parameters for removing a layer thickness of 60 microns in a single scan are 605 J / cm 2 Energy density, 80% spot overlap and 2 micron scanning pitch.

[0034] The curvature of the surface is achieved by multi-layer laser scanning, and the depth of each layer can be accurately measured to the order of 0.1 microns, which can be viewed as a continuously changing curve on a macro scale. Therefore, it can fit well with human bones / titanium alloy bones, achieving excellent adhesion between the prosthesis and the bones.

[0035] Step (2): preparing a microstructure on the upper surface of the hydrogel prosthesis;

[0036] The microstructure includes microgrooves and microprotrusions. When the microgrooves are formed by laser etching, the unremoved material forms microprotrusions. The microprotrusions present a quadrangular pyramid-shaped protrusion microstructure with a prism side length of 100 microns and a microstructure period of 102 microns. The laser spot diameter is 5 microns, and the etched groove width can be reduced by reducing the energy density to 100 J / cm 2 , making it impossible for the area with weak external energy of the Gaussian beam to reach the hydrogel etching threshold, and the width of the etched groove is reduced to about 2 microns (i.e., the height of the prism). The microgrooves are connected to the outside world, the fluid between the prosthesis and the bone cannot share the positive pressure, and the rough surface makes the threshold of interface shear sliding higher; the friction shear stress between the prosthesis and the titanium alloy friction interface is also significantly improved: after measurement, the friction shear stress is increased from 158Pa on the smooth surface to 1344Pa on the micro-convex surface. In addition, the texture formed by the surface microgrooves can achieve physical microstructure antibacterial and anti-fouling by weakening the adhesion of cells and impurities in the environment, so as to ensure the stable adhesion of the micro-convex structure to the bone.

[0037] Step (3): preparing a hydrogel surface micro-pit structure on the lower surface of the hydrogel prosthesis;

[0038] Using the hydrogel prosthesis as the friction substrate, micropits of different shapes (triangle, square, hexagon and circle), sizes and distributions can regulate the surface friction coefficient.

[0039] On the surface of micro-pit patterns of the same area, the more polygonal sides there are, the smaller the friction stress is: triangle (about 200Pa) > quadrilateral (about 140Pa) > hexagon (about 100Pa) > circle (about 60Pa).

[0040] Therefore, the present invention adopts micro-circular pits (radius: 74.2 and 49 microns, depth: about 22 microns) on the lower surface of the prosthesis with a spacing of 200 microns. 2The laser parameters used were a spot overlap of 84.1% and a scanning pitch of 5 microns, with line-by-line scanning. Micro-circular pits with a radius of 74.2 microns were etched in the area of ​​contact with the meniscus, and micro-circular pits with a radius of 49 microns were etched in the area of ​​contact with the patella. Furthermore, the micro-pit size was on the order of 10 microns, the size of chondrocytes, which facilitated chondrocyte attachment and provided favorable conditions for articular cartilage regeneration in the hydrogel.

[0041] The laser-selective fabrication of shape-controlled hydrogel knee implants described in this invention facilitates the intelligent design and fabrication of complex prostheses. For example, the prosthesis's outer contour, thickness, and surface curvature can be designed and fabricated based on the patient's actual cartilage contour or bone, using a hydrogel block formed using a universal mold. A friction coefficient library, derived from changes in microstructure shape, distribution, and size, is intelligently and selectively designed and controlled, corresponding to the actual friction coefficients of various regions of the articular cartilage. This allows for distorted friction control: depending on the hydrogel's contact surface and friction requirements, micro-protrusions with a higher friction coefficient can be etched onto the hydrogel's upper surface to contact the bone, preventing slippage. Micro-pits with a lower friction coefficient can be etched onto the hydrogel's lower surface, aligning with the smooth hydrogel cartilage base to reduce friction. Friction control can also be achieved across different regions of the same surface: microstructures with a lower friction coefficient are etched in areas of the cartilage with the most intense friction. The distribution of these microstructures gradually changes as the friction intensity decreases, ensuring consistent friction properties across the entire cartilage contact surface.

Claims

1. A laser selectively prepared shape-controlled hydrogel knee joint implant prosthesis, characterized in that: It includes a hydrogel knee joint implant prosthesis body, wherein the outer contour, thickness and surface curvature of the hydrogel knee joint implant prosthesis body are obtained by removing a universal hydrogel block by ultraviolet laser etching; The universal hydrogel block is obtained by pouring a hydrogel precursor solution into a universal mold and then undergoing a cross-linking reaction; The upper surface of the hydrogel knee joint implant body is provided with a microstructure formed by laser etching; the upper surface refers to the surface facing the joint cavity; the microstructure includes microgrooves and microprotrusions, the microgrooves are 1-5 microns wide and connected to the outside world, and the microprotrusions are in the shape of quadrangular pyramids with a side length of 80-120 microns, a height of 1-5 microns, and a microstructure period of 81-125 microns. The lower surface of the hydrogel knee joint implant body is provided with a micro-pit structure of the order of 10 microns formed by laser etching. The micro-pit structure includes a plurality of periodically arranged circular or polygonal micro-pits. The micro-pit size in the area of ​​contact and friction with the meniscus is larger than the micro-pit size in the area of ​​contact and friction with the patella. The lower surface refers to the surface facing away from the joint cavity. Micro-pits of different shapes have different friction coefficients, and the friction coefficient is adjusted by a combination of the shape and size parameters of the micro-pit structure. The surfaces formed by laser etching of microgrooves and microprotrusions on the upper surface and micropits on the lower surface of the hydrogel knee joint implant prosthesis body have different porosities.

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