Organ chip design method, system and organ chip based on similarity principle

Abstract

The present invention provides an organ chip design method, system and organ chip based on the similarity principle, which relates to the technical field of organ chip. The method includes determining a length scale to obtain the geometric size of the cell culture area of ​​the organ chip; selecting a dimensionless number based on which the organ chip parameters are calculated, and calculating the range of the corresponding dimensionless number in the body; according to the shear stress to which the cells are subjected in the organ, combined with the range of the calculated dimensionless number, obtaining the flow range of the fluid in the organ chip and the size range of the channel; according to the scale, calculating the channel characteristic length and determining the corresponding flow size; according to the oxygen permeability characteristics of the material used for the organ chip, determining the thickness of the external wall of the organ chip; simulating and verifying whether the various parameter indicators of the organ chip meet the design requirements, and completing the design of the organ chip. The present invention can make the organ chip closer to the real state in the human body.

Description

Technical Field

[0001] The present invention relates to the technical field of organ chips, and in particular to an organ chip design method, system and organ chip based on the similarity principle. Background Art

[0002] Organs-on-Chips (OoCs) provide a powerful in vitro platform for studying organ physiology, pathology, and pharmacology. For example, drug absorption can be studied using intestinal organ chips, the mechanism of action of alcoholic liver injury can be studied using liver organ chips, and the first-pass metabolism of drugs can be studied using intestinal-liver organ chips.

[0003] However, it is difficult for existing organ chips to simultaneously reproduce multiple physiological characteristics of human organs, such as geometry, fluid dynamics environment, oxygen gradient, etc., which affects the reliability of experimental results. Due to different focuses, the sizes and parameters of the designed organ chips are different. Taking the design of intestinal organ chips as an example, the viscosity of chyme in the intestine is a complex parameter, which varies according to many factors such as the composition of food, digestion stage, individual differences, etc. According to existing research on the viscosity of chyme under different conditions, the Reynolds number of the human intestine is calculated to range from 0.125 to 70. However, in some existing studies of intestinal organ chips, the height of the upper channel of the intestinal organ chip is set to 500μm. In order to establish an oxygen gradient in the intestinal organ chip similar to that in the body, the Reynolds number in the upper channel is only 0.0185; in other studies, the intestinal organ chip is designed to reproduce the intestinal cells being subjected to 0.02dyne / cm 2 Shear stress, but the Reynolds number in the channel is 0.0395. The Reynolds number in these intestinal organ chips is far from the actual situation in the human intestine.

[0004] It can be seen that although the existing technology has designed different research parameters based on different purposes, they are all far from the actual intestinal Reynolds number range, making it difficult to truly reproduce the fluid mechanics environment in the intestine. Other organ chips also have similar problems, making it difficult to simultaneously reproduce multiple physiological characteristics of organs in experiments. Summary of the invention

[0005] In order to address the deficiencies of the prior art, the purpose of the present invention is to provide an organ chip design method, system and organ chip based on the similarity principle, so that the organ chip is closer to the real state in the human body.

[0006] In order to achieve the above object, the first aspect of the present invention provides an organ chip design method based on the similarity principle, comprising:

[0007] Determine the scale between the organ chip and the human organ, and obtain the geometric dimensions of the cell culture area of ​​the organ chip;

[0008] Select the dimensionless number based on which the organ chip parameters are calculated, and calculate the range of the corresponding dimensionless number in the body organ;

[0009] According to the shear stress to which cells are subjected in human organs, combined with the range of dimensionless numbers calculated, the flow range of the fluid and the size range of the channel in the organ chip are obtained;

[0010] According to the scale, calculate the characteristic length of the channel and determine the corresponding flow rate;

[0011] Determine the thickness of the outer wall of the organ chip based on the oxygen permeability characteristics of the material used in the organ chip;

[0012] Computational fluid dynamics tools are used to simulate and verify whether the various parameter indicators of the organ chip meet the design requirements, and the design of the organ chip is completed.

[0013] A second aspect of the present invention provides an organ chip design system based on the similarity principle, comprising:

[0014] A geometric similarity module is configured to determine the scale between the organ chip and the human organ, and obtain the geometric size of the cell culture area of ​​the organ chip;

[0015] A dimensionless number selection module is configured to select a dimensionless number based on which the organ chip parameter is calculated, and calculate a range of the corresponding dimensionless number in the body organ;

[0016] A flow rate and channel size calculation module is configured to obtain a flow rate range of the fluid and a channel size range in the organ chip based on the shear stress to which the cells are subjected in the human organ and the range of the calculated dimensionless number;

[0017] A characteristic length calculation module is configured to calculate the characteristic length of the channel and determine the corresponding flow size according to the scale;

[0018] an external wall thickness calculation module, configured to determine the external wall thickness of the organ chip according to the oxygen permeability characteristics of the material used in the organ chip;

[0019] The verification module is configured to simulate and verify whether the parameter indicators of the organ chip meet the design requirements to complete the design of the organ chip.

[0020] A third aspect of the present invention provides an organ chip, wherein the organ chip is designed based on an organ chip design method based on the similarity principle provided in the first aspect.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides an organ chip design method, system and organ chip based on the principle of similarity. Based on the principle of similarity, various parameters of the organ chip are designed from the perspectives of geometric similarity and dynamic similarity, so that the designed organ chip is more similar to the geometric shape and fluid mechanics performance of the real in vivo organ, so as to be closer to the real state in the human body, which helps to improve the reliability of experimental results based on the organ chip. According to the actual flow characteristics of the organ chip, key dimensionless numbers are selected as design parameters, so that the dimensionless numbers of the organ chip and the in vivo organ are equal, so as to achieve similar fluid mechanics performance. Key indicator parameters in the organ, such as the shear stress on the cells, are used as the design verification object, so that the organ chip can simulate the functions and interactions of organs in the human body more realistically and accurately.

[0023] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 is a schematic diagram of the method in Embodiment 1 of the present invention;

[0026] Figure 2 is an overall flow chart of the method in Embodiment 1 of the present invention;

[0027] Figure 3 This is a schematic diagram of the overall structure of the intestinal organ chip in Example 3 of the present invention;

[0028] Figure 4 This is a schematic diagram of the channel structure of the intestinal organ chip in Example 3 of the present invention;

[0029] Figure 5 for Figure 4 Middle CC section;

[0030] Figure 6 for Figure 4 Middle EE section;

[0031] Figure 7 for Figure 5 Simulated shear stress distribution diagram of the D-D' section;

[0032] Figure 8 This is a schematic diagram of the oxygen gradient simulation results of the intestinal organ chip in Example 3 of the present invention;

[0033] Fig. 9 for Figure 8Oxygen concentration gradient diagram of the B-B' section;

[0034] Fig.10 This is a schematic diagram of the overall structure of the liver organ chip in Example 4 of the present invention;

[0035] Fig.11 Schematic diagram of the channel structure of the liver organ chip in the fourth embodiment of the present invention;

[0036] Fig.12 for Fig.11 Middle FF section;

[0037] Fig.13 This is a schematic diagram of the oxygen gradient simulation results of the liver organ chip in Example 4 of the present invention;

[0038] Fig.14 for Fig.13 Simulated shear stress distribution diagram of the A-A' section;

[0039] Fig.15 for Fig.13 Oxygen concentration gradient diagram along the A-A' section.

[0040] Among them, 1-1, inlet of the upper channel of the intestinal organ chip; 1-2, inlet of the lower channel of the intestinal organ chip; 1-3, lower channel of the intestinal organ chip; 1-4, porous membrane of the intestinal organ chip; 1-5, outlet of the upper channel of the intestinal organ chip; 1-6, outlet of the lower channel of the intestinal organ chip; 1-7, dual-channel vacuum stretching chamber of the intestinal organ chip; 1-8, upper channel of the intestinal organ chip; 2-1, inlet of the channel of the liver organ chip; 2-2, outlet of the channel of the liver organ chip; 2-3, cell culture layer of the liver organ chip; 2-4, porous membrane of the liver organ chip; 2-5, channel of the liver organ chip. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] Embodiment 1

[0043] Embodiment 1 of the present invention provides an organ chip design method based on the similarity principle, comprising:

[0044] S1. Determine the scale between the organ chip and the human organ, and obtain the geometric dimensions of the cell culture area of ​​the organ chip, such as the height of intestinal villi, the diameter of liver lobule, etc.

[0045] S2. Select the dimensionless number for calculating the organ chip parameters, and calculate the range of the corresponding dimensionless number in the body organ;

[0046] S3. According to the shear stress to which cells are subjected in human organs, combined with the range of the calculated dimensionless number, the flow range of the fluid and the size range of the channel in the organ chip are obtained;

[0047] S4. Calculate the characteristic length of the channel and determine the corresponding flow rate according to the scale;

[0048] S5. determining the thickness of the outer wall of the organ chip according to the oxygen permeability characteristics of the material used for the organ chip;

[0049] S6. Simulate and verify whether the parameter indicators of the organ chip meet the design requirements and complete the design of the organ chip.

[0050] In order to make the organ chip closer to the real state in the human body, this embodiment optimizes the design steps of the organ chip based on the principle of similarity. The principle of similarity is to derive the performance or behavior of the actual object from the experimental model (usually a physical model with a reduced or enlarged scale). If two objects satisfy the principle of similarity, the two objects need to satisfy geometric similarity, motion similarity and dynamic similarity. Among them, geometric similarity refers to the similarity of the geometric shapes of the two (prototype and model) flow fields, that is, the corresponding line segment lengths are proportional, the angles are the same, etc.; motion similarity refers to the geometric similarity of the streamlines of the two flows, the corresponding points have the same velocity direction, and the size is proportional; dynamic similarity refers to the particles at the corresponding points of the two flows being acted upon by the same force, and the direction of the force is the same and the size is proportional. Among them, geometric similarity is the premise of motion similarity and dynamic similarity, dynamic similarity is the main factor determining flow similarity, and motion similarity is the result of geometric similarity and dynamic similarity.

[0051] To achieve similarity between the prototype and the model, geometric similarity must be satisfied first, and dynamic similarity must be achieved secondly. If the dynamics of the two flow models are to be similar, the scale of each single force must conform to a certain constraint relationship. This constraint relationship is called the similarity criterion. The similarity criteria include the Reynolds criterion (inertia and viscosity), the Froude criterion (inertia and gravity), the Euler criterion (inertia and pressure), etc.

[0052] The core of realizing dynamic similarity in the similarity principle is to ensure that the experimental model and the actual object have similar physical phenomena by keeping the main dimensionless parameters equal. Dimensionless numbers are unitless quantities used to describe the relative relationship between various variables in physical phenomena. Common dimensionless numbers include the Strouhal number, Froude number, Euler number and Reynolds number in fluid mechanics. Among them, the Strouhal number (Sr) represents the ratio of non-motion inertial force to inertial force, and the equation is:

[0053] ;

[0054] Among them, u is the velocity vector of the fluid, that is, the flow rate (unit: cm / s), L is the characteristic length of the channel, and t is the time term.

[0055] The Froude number (Fr) is a dimensionless number used in fluid mechanics to describe the ratio of gravity to inertial force. The equation is:

[0056] ;

[0057] Here, g is the acceleration due to gravity.

[0058] The Euler number (Eu) is a dimensionless number in fluid mechanics that describes the ratio of pressure to inertial force. The equation is:

[0059] ;

[0060] in, is the fluid density (in g / cm³), and p is the pressure (in Pa).

[0061] The Reynolds number (Re) is defined by the magnitude of the viscous force and inertial force acting on the fluid in the microchannel:

[0062] ;

[0063] in, is the dynamic viscosity of the fluid (in g / cm·s).

[0064] In fluid mechanics, the basic equation describing fluid motion is the Navier-Stokes equation, which is expressed as:

[0065] ;

[0066] Where p is the pressure, is the fluid density, is the fluid dynamic viscosity, and F is the volume force term. i is a free index, which represents the physical quantity in a specific direction. For example, when i=1, i=2, and i=3, they correspond to the components in the x, y, and z directions, respectively. Therefore, v i represents the velocity vector in the i-th direction (x i direction). j is the summation index, which means the summation in all spatial directions. According to the Einstein summation convention, if repeated index j appears in the same expression, it means summing j from 1 to 3 (for three-dimensional problems). For example, It means that j sums all directions with values ​​1, 2, and 3, v j is the velocity component in the j direction, It represents the spatial rate of change of the component of velocity in the i direction relative to the j direction.

[0067] In order to transform the Navier-Stokes equation into an equation with dimension 1, the reference characteristic velocity is introduced , datum characteristic length , benchmark characteristic time , reference characteristic pressure . Define a quantity with dimension number 1:

[0068] ;

[0069] ;

[0070] ;

[0071] ;

[0072] in, represents the dimensionless velocity, represents the dimensionless position, represents dimensionless time, Represents dimensionless pressure.

[0073] The characteristic quantity (dimensionless velocity , dimensionless position , dimensionless time , dimensionless pressure ) is substituted into the Navier-Stokes equation to obtain an equation with dimension 1:

[0074] ;

[0075] in, is the Strouhal number, is the Froude number, is the Euler number, is the Reynolds number. Substituting the four dimensionless numbers, we get the relationship equation between the fluid motion parameters and the dimensionless numbers:

[0076] ;

[0077] However, it is very difficult to ensure that all dimensionless numbers are the same as those in human organs, so when solving the actual flow field, the key dimensionless numbers are determined to be the same by comparing the four dimensionless numbers in the equation. When the flow is constant, the Sr number can be different; if the gravity in the flow field has a smaller effect than other forces, the Fr number can be ignored; if the pressure in the flow field is constant, the Eu number can be ignored. Therefore, in the design of organ chips, the Reynolds criterion is the main focus, because the size of the Reynolds number has a direct impact on the calculation of the Navier-Stokes equations. When the Reynolds number is less than 1, the viscous force dominates and the impact on the flow field can be ignored.

[0078] Since the microchannels of organ chips are mostly rectangular structures, the characteristic length L can be calculated using the following formula:

[0079] ;

[0080] Where W is the channel width and H is the channel height.

[0081] In addition, the shear stress generated by the fluid in the channel has an important impact on the growth, differentiation and function of cells. In order to ensure that the shear stress in the chip is equivalent to that in human organs, more accurately simulate the physiological state of cells in the body, and thus improve the reliability of experimental data, the shear stress on the cells is solved according to the internal friction law of Newtonian fluid mechanics:

[0082] ;

[0083] in, is the fluid shear stress (unit: dyne / cm 2 ), Q is the volume flow rate (in cm³ / s).

[0084] Finally, when determining the external wall thickness of the organ chip, the oxygen permeability characteristics of the material used in the organ chip are determined by the oxygen flux of the material used. calculate:

[0085] ;

[0086] Where K0 is the overall mass transfer coefficient ( , P m is the oxygen permeability of the material, is the material thickness), is the oxygen partial pressure in the incubator atmosphere, is the Henry constant of oxygen 9.901×10 -6 mol / (m³·Pa), is the oxygen concentration. In this embodiment, the material used for the organ chip is polydimethylsiloxane (PDMS), and the corresponding oxygen permeability P m =5.1×10 -18 (mol·m) / m 2 ·s·Pa.

[0087] In step S1, the scale of the organ chip and the human organ is determined on the premise of facilitating the processing and manufacturing of the organ chip and cell culture. For the case where the geometric structure size of the organ is larger than the organ chip, such as the intestine, a reduced-size organ chip is designed, and for organs with microscopic structures, such as liver lobules, an enlarged-size organ chip is designed. The scale can be determined based on the proportional relationship between the organ chip designed in the prior art and the organ structure, and the organ structure is scaled proportionally according to the scale to obtain the geometric size of the cell culture area of ​​the organ chip.

[0088] In step S2, dimensionless numbers include Strouhal number, Froude number, Euler number, and Reynolds number. The dimensionless number that has the greatest impact on the fluid flow in the organ chip is selected as the basis for calculation. Considering the actual state of the fluid flow field in the organ, the Reynolds criterion is usually used as the basis for calculation, that is, the calculation is based on the consistency between the Reynolds number of the designed organ chip and the Reynolds number of the corresponding organ to ensure that the fluid mechanics properties of the organ chip and the in vivo organ are similar. Therefore, it is necessary to calculate the range of the in vivo Reynolds number corresponding to the organ based on the in vivo data of the organ in the human body.

[0089] In step S3, considering that shear stress has an important influence on cell growth, differentiation and function, in order to truly reproduce the flow characteristics of the fluid in the organ and accurately simulate the physiological state of cells in the body, the magnitude of the shear stress to which the cells are subjected in the organ and the range of the calculated dimensionless numbers are substituted into the relationship equation between the fluid motion parameters and the dimensionless numbers. Combined with the calculation formula of the characteristic length of the organ chip channel, the size range of the channel is solved jointly, and the flow velocity and flow rate of the fluid in the corresponding channel are calculated at the same time.

[0090] In step S4, the characteristic length of the channel of the organ chip is obtained according to the characteristic length of the organ under study and the scale determined in step S1, and then the design parameters such as the height, width, flow rate, volume flow rate, dimensionless number, etc. of the channel are calculated.

[0091] In step S5, when the cell culture area in the organ chip is in the initial state, a weak oxygen gradient will be formed in the organ chip due to the consumption of oxygen by the cells themselves. However, due to the good oxygen permeability of the PDMS material, the oxygen flux outside the organ chip exceeds the oxygen consumption rate of the cells, making it difficult to reproduce the oxygen gradient in the chip. In order to establish an oxygen gradient similar to that in the body in the organ chip, the oxygen permeability of the PDMS material is first combined to simulate the oxygen concentration range in the organ chip, control the thickness of the organ chip wall, and then use a high-airtightness material (such as polyvinylidene chloride (PVDC)) film to coat the chip surface, control the penetration of oxygen from the external environment, so that the oxygen concentration or oxygen gradient in the organ chip is close to the in vivo environment.

[0092] In step S6, the designed organ chip is simulated and verified, including shear stress and oxygen concentration. The shear stress magnitude, oxygen concentration range, and oxygen gradient in the channel of the organ chip are simulated to determine whether the organ chip meets the design requirements.

[0093] Embodiment 2

[0094] This embodiment provides an organ chip design system based on the similarity principle, including:

[0095] A geometric similarity module is configured to determine the scale between the organ chip and the human organ, and obtain the geometric size of the cell culture area of ​​the organ chip;

[0096] A dimensionless number selection module is configured to select a dimensionless number based on which the organ chip parameter is calculated, and calculate a range of the corresponding dimensionless number in the body organ;

[0097] A flow rate and channel size calculation module is configured to obtain a flow rate range of the fluid and a channel size range in the organ chip based on the shear stress to which the cells are subjected in the human organ and the range of the calculated dimensionless number;

[0098] A characteristic length calculation module is configured to calculate the characteristic length of the channel and determine the corresponding flow size according to the scale;

[0099] an external wall thickness calculation module, configured to determine the external wall thickness of the organ chip according to the oxygen permeability characteristics of the material used in the organ chip;

[0100] The verification module is configured to simulate and verify whether the parameter indicators of the organ chip meet the design requirements to complete the design of the organ chip.

[0101] It should be noted here that the various modules in this embodiment correspond one-to-one to the steps of the method in Example 1, and the specific implementation process is the same, which will not be repeated here.

[0102] Embodiment 3

[0103] In this embodiment, based on the organ chip design method based on the similarity principle provided in Embodiment 1, an intestinal organ chip was designed in combination with specific parameters.

[0104] The optimized design of intestinal organ chips is mainly based on the structure and function of the intestine, combined with microfluidic technology, aiming to simulate the complex physiological environment in the intestine. First, the geometric design should imitate the three-dimensional morphology of the intestine as much as possible, especially the intestinal villus structure, to maximize the absorption surface area of ​​nutrients and drugs. In addition, precise control of flow rate and shear stress is key to reproduce the flow characteristics of different parts of the intestine and promote the growth, differentiation and functional maintenance of epithelial cells.

[0105] The optimization goal of the design of this example is to subject the cells to a shear stress in the range of 0.0002-0.008Pa and to maintain the cells in an oxygen partial pressure range of 30-65mmHg.

[0106] The structure of the designed intestinal organ chip is as follows Figure 3-Figure 6As shown, it includes an inlet 1-1 on the upper channel of the intestinal organ chip, an inlet 1-2 on the lower channel of the intestinal organ chip, a lower channel 1-3 on the intestinal organ chip, a porous membrane 1-4 on the intestinal organ chip, an outlet 1-5 on the upper channel of the intestinal organ chip, an outlet 1-6 on the lower channel of the intestinal organ chip, a double-channel vacuum stretching chamber 1-7 on the intestinal organ chip, and an upper channel 1-8 on the intestinal organ chip. Among them, the upper channel 1-8 of the intestinal organ chip simulates the luminal environment of the intestine, in which intestinal epithelial cells are planted, and the culture medium is perfused to provide the nutrients and shear stress required for cell growth. The lower channel 1-3 of the intestinal organ chip is used to simulate the vascular environment of the intestine, and the metabolites of the intestinal epithelial cells are taken away by the perfusion of the culture medium. The upper channel 1-8 of the intestinal organ chip and the lower channel 1-3 of the intestinal organ chip are separated by a porous membrane 1-4 on the intestinal organ chip covered with an extracellular matrix (ECM), which allows the exchange of substances between cells and maintains the microenvironment similar to the inner wall of the intestine and the external blood vessels above and below. Intestinal organ chip dual-channel vacuum stretching chambers 1-7 are provided on both sides of the intestinal organ chip channel. By changing the air pressure in the stretching chambers on both sides, a stretching cycle is generated on the porous membrane of the cultured cells to simulate the peristaltic movement of the intestine.

[0107] The viscosity of chyme in the intestine is a complex parameter affected by many factors, including the composition of food, digestion stage, individual differences, etc. The viscosity of chyme under different conditions was measured and analyzed, and it was found that the viscosity of chyme is 0.01-1Pa·s, the density is 1000-1400kg / m³, and the flow rate is 0.005-0.02m / s. In addition, the average diameter of the small intestine is 0.025m.

[0108] The villus size in the intestinal organ chip experiment in the prior art was investigated. In some experiments, the villus height was found to be 40-50 μm on the third day of the experiment, and in other experiments, the villus height was measured to be 37.04±2.38 μm. The villus height in the human intestine is about 500 μm. Based on this, the scale determined in this embodiment is a reduction ratio of 12.5. According to the actual size of the intestinal villi and the determined scale, the height, diameter and spacing of the villi are scaled proportionally, keeping the villus density unchanged, and determining the scaled geometric dimensions, as shown in Table 1.

[0109] Table 1 Geometric dimensions of villus structures in intestinal organ chips

[0110]

[0111] Considering that the fluid flow in the intestinal organ chip is mainly affected by viscous force and inertial force, the Reynolds criterion is selected as the basis for flow similarity calculation, that is, the Reynolds number is selected as the dimensionless number used as the basis for parameter calculation.

[0112] Based on the in vivo data, the Reynolds number range of the in vivo small intestine was calculated. The lower limit of the Reynolds number is At minimum flow rate, minimum density and maximum viscosity:

[0113] ;

[0114] in, represents the minimum value of food density, represents the minimum value of the food flow rate, L represents the characteristic length, which is the average diameter of the small intestine 0.025m. Indicates the maximum value of food viscosity.

[0115] Upper limit of Reynolds number At maximum flow rate, maximum density and minimum viscosity:

[0116] ;

[0117] in, represents the maximum value of the food density, represents the maximum value of the food flow rate, Indicates the minimum value of food viscosity.

[0118] Studies have shown that intestinal cells are subjected to 0.02 dyne / cm 2 =0.002Pa=0.02g / (cm·s 2 ) shear stress, it can accelerate polarization and promote the spontaneous formation of wrinkles in the cell monolayer to form a villus-like structure. Assuming the density of the culture medium is 1000kg / m³=1g / cm 3 , the viscosity is 0.001Pa·s=0.01g / (cm·s), the channel width is twice the channel height, and after substituting the Reynolds number calculation formula, characteristic length calculation formula and shear stress calculation formula, we can get:

[0119] ;

[0120] ;

[0121] According to the range of Reynolds number, the size range of the channel can be calculated by substituting it into the above formula. When the Reynolds number takes the lower limit of 0.125, the channel height is calculated to be 0.053cm, the channel width is 0.106cm, the flow rate is 0.0177cm / s, and the volume flow rate is 0.053cm×0.106cm×0.0177cm / s=0.0000994386cm³ / s (0.3579μL / h).

[0122] When the Reynolds number takes the upper limit of 70, the corresponding calculation results show that the channel height is 1.255 cm, the channel width is 2.51 cm, the flow velocity is 0.41833 cm / s, and the volume flow rate is 1.31776 cm³ / s (4743937.649 μL / h).

[0123] In summary, the channel size range is: channel height 0.053cm-1.255cm, channel width 0.106cm-2.51cm; volume flow rate range is: 0.0000994386cm³ / s-1.31776cm³ / s (0.3579μL / h-4743937.649μL / h).

[0124] From the in vivo data, we know that the average diameter of the human small intestine is 25mm. Since we only study the distance from the villi on one side to the center of the intestine, this example takes the characteristic length of the small intestine as 12.5mm. Based on the reduction ratio of 12.5, the characteristic length of the organ chip is 1mm. Assuming that the channel width is twice the height, the corresponding channel height is calculated to be 0.75mm, the channel width is 1.5mm, the flow rate is 0.25mm / s, and the volume flow rate is 0.28125mm 3 / s=1012.5μL / h, Reynolds number is 0.25.

[0125] The material used for the organ chip is PDMS, and the permeability coefficient of oxygen in PDMS is 5.8×10-10cm 3 (STP)cm / cm 2 ·s·Pa, the permeability coefficient of the PVDC film coated on the chip surface is 1×10-16cm 3 (STP)cm / cm 2 ·s·Pa. The oxygen concentration range is simulated to make the oxygen concentration in the organ chip close to that in the body environment and determine the thickness of the external wall of the organ chip. According to the simulation results, the distance between the upper channel and the top of the chip is 3.5mm, and the distance between the lower channel and the bottom of the chip is 1mm.

[0126] The parameter indicators of the intestinal organ chip are shown in Table 2, where the oxygen partial pressure range is obtained according to the simulation results.

[0127] Table 2 Design parameters of intestinal organ chip

[0128]

[0129] According to the determined characteristic length of the organ chip of 1 mm, the corresponding channel height is 0.75 mm, the channel width is 1.5 mm, the flow rate is 0.25 mm / s, and the volume flow rate is 0.28125 mm 3 / s=1012.5μL / h, Reynolds number is 0.25. The above parameters are used to design the intestinal organ chip, and the shear stress and oxygen concentration range are simulated to verify whether they meet the design requirements.

[0130] The shear stress distribution results in the channel obtained by computational fluid dynamics simulation are as follows: Figure 7 As shown, the shear force on the cells at this time is 0.002Pa-0.003Pa, which is consistent with the in vivo data.

[0131] The oxygen concentration range in the intestinal organ chip is as follows Figure 8 , Fig. 9 As shown, an oxygen gradient of 22-35 mmHg was formed in the upper channel.

[0132] Embodiment 4

[0133] In this embodiment, based on the organ chip design method based on the similarity principle provided in Embodiment 1, a liver organ chip is designed in combination with specific parameters to simulate the structure and function of the liver so as to reproduce the physiological processes of the liver such as metabolism, detoxification and secretion in vitro.

[0134] The geometric design of the liver organ chip should mimic the microscopic hexagonal structure of the liver lobule as much as possible. Secondly, microchannels are constructed in the chip through microfluidics technology to ensure that the fluid dynamic conditions in the chip are similar to the blood flow characteristics in the liver. The control of fluid flow rate, shear stress and flow state is crucial, and the flow in the chip should be kept in a laminar state to maintain the normal function and metabolic activity of liver cells.

[0135] The optimization goal of this example is to ensure that the oxygen concentration gradient in the liver organ chip is the same as that in the liver sinusoidal structure in vivo, that is, from 65 mmHg at the periphery of the chip to 30 mmHg. -4 A shear stress of 0 Pa can reduce the expression of CYP1A2 in liver cells to 1 / 20, so the shear stress to which cells are subjected in the designed liver organ chip should be as small as possible (the closer to 0 Pa, the better).

[0136] The structure of the designed liver organ chip is as follows Figure 10-12As shown, the upper layer of the chip is designed with 6 evenly distributed liver organ chip channels 2-5, the inlets of the 6 liver organ chip channels are separated, and the outlets are converged. Each of the 6 channels has a liver organ chip channel inlet 2-1, and the 6 channels have a liver organ chip channel outlet 2-2 set in the center. The lower part of the 6 liver organ chip channels has a liver organ chip cell culture layer 2-3, the structure of the liver organ chip cell culture layer is close to the in vivo structure, and the liver organ chip cell culture layer and the liver organ chip channels are separated by a liver organ chip porous membrane 2-4. The six upper liver organ chip channels are perfused with culture medium to simulate the flow path from the portal vein to the central vein. The geometric structure of the lower liver organ chip cell culture layer is close to the hexagon of the in vivo liver lobule, and the culture medium seeps down from the upper channel through the liver organ chip porous membrane. This structure mimics the blood flow characteristics caused by the hepatic sinusoidal window osmotic effect.

[0137] There are about 500,000 to 1,000,000 hepatic lobules and 1 billion hepatic sinusoids in the adult liver. The hepatic lobules are polygonal prisms with a diameter of about 1 mm. There are about 1,000 to 2,000 hepatic sinusoids in one hepatic lobule. In addition, the diameter of the hepatic sinusoidal blood vessels is about 0.01 mm. Some studies have found that red blood cells in the hepatic sinusoids move 107.43 μm in 302 ms, and the blood flow velocity in the hepatic sinusoids can be calculated to be 354.4 μm / s. Other studies have provided blood density ranges of 1043-1060 kg / m³ and blood viscosity of 3×10 -3 -5×10 - 3 Pa·s.

[0138] The liver lobule is a polygonal prism with a diameter of about 1 mm. However, due to its small size, it is difficult to make a liver organ chip at a 1:1 ratio. To facilitate processing and manufacturing, this embodiment determines an enlargement ratio of 5, and the cell culture area in the organ chip is a hexagonal structure with a diameter of 5 mm.

[0139] Considering that the fluid flow in the liver organ chip is mainly affected by viscous force and inertial force, the Reynolds criterion is selected as the basis for flow similarity calculation, that is, the Reynolds number is selected as the dimensionless number used as the basis for parameter calculation.

[0140] According to the in vivo parameters, the cross-sectional area A of a single hepatic sinusoid is first calculated as:

[0141] ;

[0142] Where D is the diameter of the hepatic sinusoidal vessels.

[0143] Since the hepatic sinusoidal vessels in the hepatic lobule are interconnected, it is estimated that there are about 1500 hepatic sinusoidal vessels in one hepatic lobule. To facilitate the processing of organ chips, in this embodiment, 1500 channels are equivalent to 6 organ chip microchannels, that is, each organ chip channel is equal to the total flow area of ​​250 hepatic sinusoidal vessels, and the cross-sectional area of ​​each organ chip microchannel is: 250×7.85×10 -5 mm 2 =0.019625mm 2 .

[0144] Then, according to the circle area formula, the characteristic length of the in-body channel is calculated:

[0145] ;

[0146] The calculated characteristic length of the in-body channel is L = 0.158 mm = 1.58 × 10 -4 m.

[0147] According to the Reynolds number formula, the Reynolds number range in the six simplified channels was calculated. The lower limit of the Reynolds number was obtained when the blood density was the lowest and the viscosity was the highest, and the lower limit of the Reynolds number was calculated to be 0.0116; the upper limit of the Reynolds number was obtained when the blood density was the highest and the viscosity was the lowest, and the upper limit of the Reynolds number was calculated to be 0.0197.

[0148] Studies have shown that 4.7×10 -4 Pa shear stress will reduce the expression of cell CYP1A2 to 1 / 20, and when the shear stress reaches 0.1Pa, the survival rate of liver cells drops to 25%. In order to avoid this problem, liver cells are cultured in the lower layer of the organ chip, and the negative effects of shear stress are shielded by a porous membrane. Therefore, it is only necessary to solve the relationship between the model flow rate and the channel size ratio based on the relationship equation between the fluid motion parameters and the dimensionless number. Assume that the density of the culture medium is 1000kg / m³=1g / cm 3 , the viscosity is 0.001Pa·s=0.01g / (cm·s), and the channel width is twice the height. When the Reynolds number takes the lower limit of 0.0166, the numerical relationship between the flow velocity u and the channel height H is calculated to be uH=0.000087(cm); when the Reynolds number takes the upper limit of 0.0197, the numerical relationship between the flow velocity and the channel height is uH=0.00014775(cm).

[0149] According to the characteristic length of the in vivo channel and the length ratio, the characteristic length of the organ chip is 1.58×10 -4 m×5=7.9×10 -4 m=0.79mm, and then the channel height is calculated to be 0.5925mm and the channel width is 1.185mm.

[0150] Finally, it is calculated that when the Reynolds number takes the lower limit of 0.0166, the flow velocity is 0.01468mm / s, the channel cross-sectional area is 0.5925mm×1.185mm=0.7021125mm², and the volume flow rate is 0.014683mm / s×0.702112mm²=0.010309mm³ / s=0.010309μL / s=37.1128μL / h.

[0151] When the Reynolds number takes the upper limit of 0.0197, the flow velocity is 0.0249mm / s, and the volume flow rate is 0.0249mm / s×0.7021125mm²=0.01748mm 3 / s=0.0175μL / s=63.03μL / h.

[0152] In summary, the channel height is 0.5925 mm, the channel width is 1.185 mm, the flow rate range is 0.001468 mm / s-0.0249 mm / s, and the volume flow rate range is 37.1128 μL / h-63.03 μL / h.

[0153] The simulation simulates the oxygen concentration range to make the oxygen concentration in the organ chip close to that in the body and determine the thickness of the external wall of the organ chip. According to the simulation results, the distance between the upper channel and the top of the chip is 1.4mm, and the distance between the lower channel and the bottom of the chip is 1.5mm.

[0154] The designed liver organ chip was simulated, where the channel height of the liver organ chip was 0.5925 mm, the channel width was 1.185 mm, the flow rate was 0.0249 mm / s, the volume flow rate was 63.03 μL / h, and the Reynolds number was 0.0197. The shear stress simulation results are shown in Figure 2. Fig.13 As shown, the shear stress on the cells is 2.5×10 -10 Pa is close to 0, which is in line with the expected effect. The simulation results of oxygen concentration gradient are as follows Figure 14-15 As shown, 35.6-55 mmHg, consistent with in vivo data.

[0155] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An organ chip design method based on the similarity principle, characterized in that: include: Determine the scale between the organ chip and the human organ, and obtain the geometric dimensions of the cell culture area of ​​the organ chip; Select the dimensionless number based on which the organ chip parameters are calculated, and calculate the range of the corresponding dimensionless number in the body organ; According to the shear stress to which cells are subjected in human organs, combined with the range of dimensionless numbers calculated, the flow range of the fluid in the organ chip and the size range of the channel are obtained. The specific steps are as follows: based on the Navier-Stokes equation, the relationship equation between the fluid motion parameters and the dimensionless numbers is obtained; According to the relationship equation, the shear stress on the cells in the organ chip, and the range of dimensionless numbers in the volume data, the flow range of the fluid in the organ chip and the size range of the channel are calculated. The specific calculation method is: Substitute the shear stress on cells in the organ chip, the density and viscosity of the culture medium, and the multiple relationship between the channel width and the channel height into the Reynolds number calculation formula, the characteristic length calculation formula, and the shear stress calculation formula, and then substitute them into the combined formula according to the range of the Reynolds number to obtain the channel size range and the fluid flow range; According to the scale, calculate the characteristic length of the channel and determine the corresponding flow rate; Determine the thickness of the outer wall of the organ chip based on the oxygen permeability characteristics of the material used in the organ chip; The simulation verifies whether the various parameter indicators of the organ chip meet the design requirements and completes the design of the organ chip.

2. The organ chip design method based on the similarity principle as claimed in claim 1, characterized in that: The obtaining of the geometrical dimensions of the cell culture region of the organ chip includes scaling the organ structure in proportion according to a scale to obtain the geometrical dimensions of the cell culture region of the organ chip.

3. The organ chip design method based on the similarity principle as claimed in claim 1, characterized in that: The dimensionless numbers include Strouhal number, Froude number, Euler number and Reynolds number.

4. The organ chip design method based on the similarity principle as claimed in claim 3, characterized in that: Based on the actual state of the fluid flow field in the organ, the Reynolds number is selected as the basis for calculating the organ chip parameters.

5. The organ chip design method based on the similarity principle as claimed in claim 1, characterized in that: It also includes coating the surface of the organ chip with a PVDC film to control the penetration of oxygen from the external environment.

6. An organ chip design system based on the similarity principle, characterized in that: include: A geometric similarity module is configured to determine the scale between the organ chip and the human organ, and obtain the geometric size of the cell culture area of ​​the organ chip; A dimensionless number selection module is configured to select a dimensionless number based on which the organ chip parameter is calculated, and calculate a range of the corresponding dimensionless number in the body organ; The flow and channel size calculation module is configured to obtain the flow range of the fluid and the size range of the channel in the organ chip based on the shear stress to which the cells are subjected in the human organ and the range of the calculated dimensionless number. The specific steps are: obtaining the relationship equation between the fluid motion parameter and the dimensionless number based on the Navier-Stokes equation; According to the relationship equation, the shear stress on the cells in the organ chip, and the range of dimensionless numbers in the volume data, the flow range of the fluid in the organ chip and the size range of the channel are calculated. The specific calculation method is: Substitute the shear stress on cells in the organ chip, the density and viscosity of the culture medium, and the multiple relationship between the channel width and the channel height into the Reynolds number calculation formula, the characteristic length calculation formula, and the shear stress calculation formula, and then substitute them into the combined formula according to the range of the Reynolds number to obtain the channel size range and the fluid flow range; The characteristic length calculation module is configured to calculate the characteristic length of the channel and determine the corresponding flow rate according to the length ratio; an external wall thickness calculation module, configured to determine the external wall thickness of the organ chip according to the oxygen permeability characteristics of the material used in the organ chip; The verification module is configured to simulate and verify whether the parameter indicators of the organ chip meet the design requirements to complete the design of the organ chip.

7. An organ chip, characterized in that: The organ chip is designed based on the organ chip design method based on the similarity principle as described in any one of claims 1 to 6.

8. The organ chip according to claim 7, characterized in that: The organ chip is an intestinal organ chip, including an upper channel of the intestinal organ chip for simulating the inner cavity environment of the intestine, and a lower channel of the intestinal organ chip for simulating the vascular environment of the intestine, wherein the upper channel of the intestinal organ chip and the lower channel of the intestinal organ chip are separated by a porous membrane of the intestinal organ chip covered with an extracellular matrix; and also including a dual-channel vacuum stretching cavity of the intestinal organ chip located on both sides of the upper channel of the intestinal organ chip and the lower channel of the intestinal organ chip, which is used to simulate intestinal peristaltic movement by changing the air pressure.

9. The organ chip according to claim 7, characterized in that: The organ chip is a liver organ chip, comprising a plurality of evenly distributed liver organ chip channels, each of which has a liver organ chip channel inlet, and the liver organ chip channels collectively have a liver organ chip channel outlet; a liver organ chip cell culture layer is provided at the lower portion of the liver organ chip channel, and the liver organ chip cell culture layer and the liver organ chip channel are isolated by a liver organ chip porous membrane.

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