Myocardial tissue flexible force sensor integrated with magnetic drive and preparation method thereof

Abstract

The invention discloses an integrated magnetic drive myocardial tissue flexible force sensor and a preparation method thereof. The integrated magnetic drive myocardial tissue flexible force sensor structurally comprises a rigid substrate, a flexible force sensing element, a magnetic drive element and a cell culture bracket, the flexible force sensing element comprises a flexible thin film layer and a sensitive grid arranged in the flexible thin film layer; the two flexible force sensing elements are respectively connected to the lower surface of the rigid substrate and are inclined downwards to form cantilever structures, the free ends of cantilevers are oppositely arranged and are respectively connected with the magnetic driving elements, and the cell culture bracket is connected between the two magnetic driving elements. Cantilever bending deformation generated by contraction of the cardiac muscle tissue is converted into resistance change of the sensitive grid, so that contraction force sensing of the cardiac muscle tissue is achieved, and integration of mechanical excitation and contraction force sensing is achieved by stretching the cell scaffold through magnetic driving.

Description

Technical Field

[0001] The present invention belongs to the field of biomedical technology, and in particular relates to an integrated magnetically driven myocardial tissue flexible force sensor and a preparation method thereof. Background Art

[0002] In the study of in vitro culture of cardiomyocytes, the study of contractility detection and mechanical stimulation has become an important direction for exploring the mechanism of heart disease, drug screening and tissue engineering applications. The contractile function of cardiomyocytes is a key indicator of heart function, which can reflect the heart's pumping efficiency and muscle health. Therefore, how to accurately measure the contractility of cardiomyocytes and simulate the physiological environment in the body through mechanical stimulation is of great significance for studying the biological characteristics of heart cells and developing treatment strategies for heart disease.

[0003] At present, the research methods for detecting the contractile force of cardiomyocytes mainly include fiber optic sensing, force sensors, voltage changes and other means. Traditional force sensor methods such as microcantilever beams and piezoelectric sensors are widely used, which can measure the tiny force changes generated by cardiomyocyte contraction in real time. At the same time, mechanical excitation, as an important means of simulating the physiological environment, can induce the physiological response of cardiomyocytes by applying specific mechanical stimuli (such as tension, compression or shear stress). Studies have shown that mechanical excitation can effectively promote the growth, differentiation and contractile function of cardiomyocytes. Therefore, the development of an efficient mechanical excitation system is crucial to enhance the physiological response of cardiomyocytes. Existing mechanical excitation devices mostly use micro-mechanical platforms, electromagnetic drives and other technologies to simulate the working environment of the heart in the body by precisely controlling the distribution of stress and strain.

[0004] However, there is currently a lack of integrated systems that integrate flexible force sensing and mechanical excitation functions. Existing force sensors and mechanical excitation devices are often designed independently, making it difficult to achieve efficient mechanical stimulation and accurate contractile force monitoring on the same platform. This separate design limits the real-time feedback and regulation capabilities during the experiment, and also makes it difficult to obtain accurate mechanical data while the cells are receiving mechanical stimulation. Therefore, future research should focus on the development of a composite system that integrates flexible force sensing and mechanical excitation to achieve real-time monitoring of cardiomyocyte contractility and accurate physiological environment simulation, thereby improving the accuracy and effectiveness of the experiment. Summary of the invention

[0005] The purpose of the present invention is to provide a solution integrating mechanical excitation and flexible contractile force sensing to achieve real-time monitoring of the contractile force of myocardial cells and accurate physiological environment simulation.

[0006] One of the technical solutions adopted by the present invention to solve its technical problems is: a flexible force sensor for myocardial tissue integrated with magnetic drive, which includes a rigid substrate, a flexible force sensing element, a magnetic drive element, and a cell culture scaffold; the flexible force sensing element includes a flexible thin film layer and a sensitive grid built in the flexible thin film layer; two flexible force sensing elements are respectively connected to the lower surface of the rigid substrate and inclined downward to form a cantilever structure, the free ends of the cantilevers are oppositely arranged and are respectively connected to a magnetic drive element, and the cell culture scaffold is connected between the two magnetic drive elements; the cell culture scaffold is used for attaching myocardial tissue, the magnetic drive element is used to realize mechanical excitation of the myocardial tissue under the action of an external magnetic field, and the flexible force sensing element is used to detect the cell contraction force of the myocardial tissue.

[0007] Optionally, a patterned microchannel is provided in the flexible thin film layer, and the sensitive grid is laid in the patterned microchannel; the rigid substrate is provided with a conductive circuit, and the sensitive grid is electrically connected to the conductive circuit, so as to facilitate connection with an external detection device, analyze and process the change of the sensitive grid resistance in real time, and reflect the cell contraction force state after sensor calibration.

[0008] Optionally, the sensitive grid is formed of a sensitive material, and the sensitive material is PDMS doped with graphite or carbon nanotubes, conductive hydrogel or liquid metal.

[0009] Optionally, the rigid substrate is provided with a hollow groove, and the cell culture scaffold is located below the hollow groove. The setting of the hollow groove facilitates subsequent cell inoculation and observation of cell state using an inverted microscope.

[0010] Optionally, the flexible thin film layer is made of a stretchable flexible polymer, including at least one of polydimethylsiloxane, thermoplastic polyurethane, Ecoflex or silica gel.

[0011] Optionally, the cell culture scaffold is an ordered fiber structure, and the magnetic drive element drives the cantilever structure to bend and deform under the action of the external magnetic field to stretch the cell culture scaffold. The ordered fibers are formed of polymer materials such as polycaprolactone and thermoplastic polyurethane.

[0012] Optionally, the material of the magnetic drive element is a hybrid material of a magnetic material and a polymer material, wherein the magnetic material includes NdFeB and iron tetroxide, and the polymer material includes PDMS and Ecoflex.

[0013] Further preferably, the thickness of the flexible thin film layer is 0.02 - 0.5 mm; the thickness of the magnetic drive element is 0.5 - 1 mm; the area of the cell culture scaffold is 4 - 20 mm 2 。

[0014] The second technical solution adopted by the present invention to solve its technical problems is: providing a preparation method for a flexible force sensor for myocardial tissue integrated with magnetic drive, including the following steps:

[0015] 1) Fabricate a flexible thin film layer with patterned microchannels;

[0016] 2) Connect the flexible thin film layer to a rigid substrate, inject a sensitive material into the patterned microchannels to form a sensitive grid, and fabricate a flexible force sensing element with a cantilever structure;

[0017] 3) Connect a magnetic drive element and a cell culture scaffold between the free ends of the cantilevers of the two flexible force sensing elements.

[0018] Optionally, in step 3), a mixture of a magnetic material and a polymer material is used to fabricate a frame, ordered fibers are fabricated in the frame by electrospinning as the cell culture scaffold, and after removing the excess frame, two magnetic drive elements connected to both ends of the cell culture scaffold are formed, and the two magnetic drive elements are connected to the free ends of the two cantilevers in one-to-one correspondence.

[0019] Further preferably, the mixture is poured into a mold and cured at a constant temperature of 60 - 100 °C for 30 min - 1 h to form the frame.

[0020] Optionally, additive manufacturing methods such as direct writing printing can also be used to directly print the mixture on the surface of the flexible thin film layer and then cure it, and the magnetic drive element is fabricated in situ on the surface of the flexible thin film layer.

[0021] Optionally, a conductive circuit is provided on the rigid substrate. In step 2), when connecting the flexible thin film layer to the rigid substrate, the injection port of the patterned microchannel is made to correspond to the connection port of the conductive circuit, and it is poured into the patterned microchannel from the injection port by means of pressure injection.

[0022] Further preferably, a mold is prepared by using photocuring 3D printing or photolithography, a liquid polymer is poured, and it is cured at a constant temperature of 60 - 100 °C for 30 min - 1 h, and the flexible thin film layer is prepared by demolding after the polymer is cured.

[0023] The beneficial effects of the present invention are:

[0024] The present invention adopts a magnetic drive system to achieve non-contact excitation. Magnetic field drive can provide a more stable and efficient excitation means. At the same time, the flexible sensor design can adapt to the natural deformation of cardiomyocytes without affecting the normal activities of the cells and reducing the interference with the cell physiological environment. In addition, the use of biocompatible materials allows the sensor to be in long-term contact with cardiomyocytes without causing an immune response. By integrating magnetic drive and force sensing technologies, the structure of the system can be simplified, and the compactness and operability of the device can be improved. Compared with traditional force sensors, the mechanical components and electrical interfaces are reduced, making the device more suitable for high-throughput biological experiments or clinical research.

[0025] Other features and beneficial effects of the present invention will be described in the following specification, and will be partially obvious from the specification or understood by implementing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic perspective view of the flexible force sensor for myocardial tissue with integrated magnetic drive according to an embodiment, showing the position of the sensing grid on one side in the figure;

[0027] Figure 2 Exploded schematic view of the structure of the flexible force sensor for myocardial tissue with integrated magnetic drive according to an embodiment;

[0028] Figure 3 Front view of the flexible force sensor for myocardial tissue with integrated magnetic drive according to an embodiment;

[0029] Figure 4 Schematic principle diagram of the flexible force sensor for myocardial tissue with integrated magnetic drive according to an embodiment;

[0030] Figure 5 Schematic flow diagram of the preparation method of the flexible force sensor for myocardial tissue with integrated magnetic drive according to an embodiment;

[0031] Figure 6 Schematic diagram of the test results of the flexible force sensor for myocardial tissue with integrated magnetic drive according to an embodiment, where (a) is the beating and contraction signal of the myocardial tissue without mechanical stretching excitation, and (b) is the beating and contraction signal of the myocardial tissue after 7 days of mechanical stretching excitation culture.

[0032] Wherein, 1 - rigid substrate, 11 - hollow groove, 12 - conductive circuit, 12a - connection port, 2 - flexible force sensing element, 21 - flexible thin film layer, 211 - base layer, 212 - sealing layer, 22 - sensing grid, 21a - patterned microchannel, 3 - magnetic drive element, 4 - cell culture scaffold. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings and embodiments. It should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "inner", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention.

[0034] This embodiment is a myocardial tissue flexible force sensor with integrated magnetic drive, such as Figures 1 to 3 As shown, it includes a PCB rigid substrate 1, a flexible force sensing element 2, a magnetic drive element 3 and a cell culture support 4; the flexible force sensing element 2 includes a flexible film layer 21 and a sensitive grid 22 built into the flexible film layer. The two flexible force sensing elements 2 are respectively connected to the lower surface of the rigid substrate 1 and tilted downward to form a cantilever structure, the free ends of the cantilevers are arranged oppositely and are respectively connected to a magnetic drive element 3, and the cell culture support 4 is connected between the two magnetic drive elements 3, that is, the two sides of the cell culture support 4 are symmetrical structures. The cell culture support 4 is used to attach myocardial tissue; the magnetic drive element 3 is used to drive the cantilever to bend and deform under the action of an external magnetic field to stretch the cell culture support 4, thereby realizing mechanical excitation of the myocardial tissue; the flexible force sensing element 2 can be used as a cantilever when implementing mechanical excitation, and can be used to detect the cell contraction force of the myocardial tissue after the mechanical excitation is removed.

[0035] Among them, the rigid substrate 1 adopts a PCB substrate with an overall diameter of 34mm, a rectangular hollow groove 11 of 8×20mm in the middle, and a conductive circuit 12 is arranged outside the rectangular hollow groove 11. The conductive circuit 12 has a metal contact as a connection port 12a. The flexible film layer 21 has a thickness of 0.3mm, a width of 5mm, and a length of 8mm. It is formed by a base layer 211 and a sealing layer 212. The base layer 211 and the sealing layer 212 are both made of stretchable flexible polymers with thicknesses of 0.25mm and 0.05mm respectively. A patterned microchannel 21a is arranged on the base layer 211, and the sensitive gate 22 is laid in the patterned microchannel 21a, and the lead-out end is electrically connected to the connection port 12a, so as to facilitate connection with external detection equipment through the rigid substrate 1, and real-time analysis and processing of sensitive gate resistance changes. The sensitive grid 22 is injected into the patterned microchannel 21a of the flexible film layer 21 by pressure injection using a sensitive material, wherein the sensitive material is graphite or carbon nanotube-doped PDMS, conductive hydrogel or liquid metal. The sensitive grid pattern of a conventional strain sensor can be applied to this embodiment, and the length direction of the grid is the same as the expansion and contraction direction of the flexible film layer 21 when subjected to force.

[0036] The magnetic drive element 3 is formed of a hybrid material of magnetic materials such as NdFeB and magnetite mixed with polymer materials such as PDMS and Ecoflex. It has a thickness of 0.5 - 1 mm, a width preferably matching that of the flexible film layer 21, and a length of 1 - 5 mm. The cell culture scaffold 4 is a 5×5 mm square thin film with an ordered fiber structure formed of polymer materials such as polycaprolactone and thermoplastic polyurethane.

[0037] As Figure 4 shown, myocardial tissue is inoculated onto the cell culture scaffold 4. After the myocardial tissue adheres to the cell culture scaffold 4, by applying an external magnetic field, the two-sided flexible force sensing elements 2 are bent and deformed downward, thereby stretching the cell culture scaffold 4 to achieve mechanical excitation of cardiomyocytes. After removing the external magnetic field, when the cells contract and beat, they pull the two-sided flexible force sensing elements 2 to bend and deform, thereby causing strain in the sensitive grid 22 and generating a resistance change to achieve monitoring of cell contraction.

[0038] The following is an example of the preparation method of the above integrated magnetic drive myocardial tissue flexible force sensor. Refer to Figure 5 , which includes the following steps:

[0039] 1) After PDMS and the curing agent are fully mixed at a ratio of 10:1, they are poured into the base layer mold. The filled mold is placed in a vacuum drying oven to evacuate the residual gas in the mold. Finally, the mold is placed in an 80°C oven and heated for 30 min. After the PDMS is completely cured, it is demolded to obtain the base layer 211, whose surface has micro-grooves for forming the patterned microchannels 21a inside the flexible force sensing element 2. A similar method is used to form the sealing layer 212.

[0040] 2) The demolded base layer 211 and the sealing layer 212 are placed in a plasma cleaner and subjected to oxygen plasma cleaning at a power of 300 W for 90 s. After the base layer 211 and the sealing layer 212 are bonded together, they are placed at 60°C and hot-pressed for 4 h to firmly bond the two thin films to form the flexible film layer 21, with patterned microchannels 21a formed inside. The patterned microchannels 21a have injection ports communicating with the outside.

[0041] 3) A layer of PDMS is coated on the surface of the PCB serving as the rigid substrate 1, and then it is placed in an 80°C oven and heated for 30 min. After the PDMS is completely cured, it is placed in a plasma cleaner together with the flexible film layer 21 completed in step 2) and subjected to oxygen plasma cleaning at a power of 300 W for 90 s. Finally, one end of the two flexible film layers 21 is bonded to the PCB surface, and the other end (free end) is arranged opposite, and they are placed at 60°C and hot-pressed for 4 h to complete the bonding of the flexible film layer 21 to the PCB. During the bonding process, the injection ports of the patterned microchannels 21a in the flexible film layer 21 are aligned with the metal contacts serving as the connection ports 12a on the PCB.

[0042] 4) The sensitive material GaIn alloy is injected into the patterned microchannel 21a from the injection port by pressure injection to form a sensitive gate 22 of the corresponding pattern, and is connected to the connection port 12a to achieve electrical connection, so as to facilitate connection with external detection equipment through PCB lead-out. This step completes the production of the flexible force sensor element 2.

[0043] 5) PDMS and curing agent are fully mixed at a ratio of 10:1 to form a PDMS prepolymer, and the PDMS prepolymer and NdFeB particles are evenly mixed at a ratio of 3:7 to form a liquid magnetic mixed material, which is poured into the drive unit mold, and the mold after pouring is placed in a vacuum drying oven to vacuum remove the residual gas in the mold. Finally, the mold is heated at 80°C for 30 minutes, and after the mixed material is completely cured, it is demolded to obtain a frame 3' for forming the magnetic drive element 3.

[0044] 6) Attach the frame 3' to the surface of a rotating drum at a speed of 2000 r / min, prepare a 20wt% PCL-acetic acid solution in a syringe, connect the syringe needle to a voltage of 9kV, push the syringe at a rate of 380μl / h, and deposit electrospun fibers on the surface of the frame 3' to form a cell culture scaffold 4.

[0045] 7) Using hot cutting to remove the excess electrospun fibers on the surface of the frame 3 ′, and cutting off the excess frame, finally obtaining the magnetic drive element 3 connected to both ends of the cell culture support 4 , and the fibers of the cell culture support 4 are orderly arranged between the two magnetic drive elements 3 .

[0046] 8) Using PDMS prepolymer, the cell culture support 4 is bonded to the cantilever free ends of the flexible force sensing element 2 through the magnetic drive elements 3 on both sides. Finally, the bonded device is placed at 40° C. and heated for 6 hours. After the PDMS is cured, the above device is obtained.

[0047] The above-prepared integrated magnetically driven myocardial tissue flexible force sensor is used for detection. After the myocardial tissue adheres to the cell culture scaffold 4, an external periodically changing magnetic field of 10-30mT, 1Hz is applied to make the flexible force sensing elements 2 on both sides bend and deform downward, thereby stretching the cell culture scaffold 4 laterally to achieve a mechanical stretching excitation of 2%-10% for the myocardial cells. After continuous application for 3-7 days, the magnetic field is removed, and the flexible force sensing elements 2 on both sides return to the initial suspended state to detect the cell contraction force. When the cell contracts and beats, the flexible force sensing elements 2 on both sides are pulled to bend and deform, thereby causing the sensitive grid 22 to strain and produce a resistance change, thereby realizing the monitoring of cell contraction, such as Figure 6 As shown in (a) and (b), the contraction signals of cells were measured before and after stimulation, and it was observed that the amplitude and frequency of cell contraction were increased, proving that mechanical stretching stimulation promoted the maturation and development of cells.

[0048] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A myocardial tissue flexible force sensor with integrated magnetic drive, characterized in that: It includes a rigid substrate, a flexible force sensing element, a magnetic driving element and a cell culture support; the flexible force sensing element includes a flexible film layer and a sensitive grid built into the flexible film layer; two flexible force sensing elements are respectively connected to the lower surface of the rigid substrate and tilted downward to form a cantilever structure, the free ends of the cantilevers are arranged opposite to each other and are respectively connected to a magnetic driving element, and the cell culture support is connected between the two magnetic driving elements; the cell culture support is used to attach myocardial tissue, the magnetic driving element is used to achieve mechanical excitation of the myocardial tissue under the action of an external magnetic field, and the flexible force sensing element is used to detect the cell contraction force of the myocardial tissue.

2. The integrated magnetically driven myocardial tissue flexible force sensor according to claim 1, characterized in that: The flexible film layer is provided with a patterned microchannel, and the sensitive grid is laid in the patterned microchannel; the rigid substrate is provided with a conductive circuit, and the sensitive grid is electrically connected to the conductive circuit.

3. The integrated magnetically driven myocardial tissue flexible force sensor according to claim 1, characterized in that: The sensitive grid is formed of a sensitive material, and the sensitive material is graphite or carbon nanotube-doped PDMS, conductive hydrogel or liquid metal.

4. The integrated magnetically driven myocardial tissue flexible force sensor according to claim 1, characterized in that: The rigid substrate is provided with a hollow groove, and the cell culture support is located below the hollow groove.

5. The integrated magnetically driven myocardial tissue flexible force sensor according to claim 1, characterized in that: The material of the flexible film layer includes at least one of polydimethylsiloxane, thermoplastic polyurethane, Ecoflex or silicone.

6. The integrated magnetically driven myocardial tissue flexible force sensor according to claim 1, characterized in that: The cell culture support is an ordered fiber structure, and the magnetic drive element drives the cantilever structure to bend and deform under the action of the external magnetic field to stretch the cell culture support.

7. The integrated magnetically driven myocardial tissue flexible force sensor according to claim 1, characterized in that: The material of the magnetic drive element is a mixture of magnetic material and polymer material, wherein the magnetic material includes NdFeB and ferrosoferric oxide, and the polymer material includes PDMS and Ecoflex.

8. A method for preparing the integrated magnetically driven myocardial tissue flexible force sensor according to claim 1, characterized in that: include: 1) Fabricating a flexible film layer with patterned microchannels; 2) Connecting the flexible film layer to the rigid substrate, injecting sensitive materials into the patterned microchannel to form a sensitive gate, and making a flexible force sensing element with a cantilever structure; 3) Connecting a magnetic drive element and a cell culture support between the free ends of the cantilevers of the two flexible force sensing elements.

9. The method for preparing the integrated magnetically driven myocardial tissue flexible force sensor according to claim 8, characterized in that: In step 3), a mixture of magnetic material and polymer material is used to make a frame, and ordered fibers are made in the frame by electrospinning as a cell culture scaffold. After removing the excess frame, two magnetic drive elements connected to the two ends of the cell culture scaffold are formed, and the two magnetic drive elements are connected to the free ends of the two cantilevers one by one.

10. The method for preparing the integrated magnetically driven myocardial tissue flexible force sensor according to claim 8, characterized in that: The rigid substrate is provided with a conductive circuit. In step 2), when the flexible film layer is connected to the rigid substrate, the injection port of the patterned microchannel corresponds to the connection port of the conductive circuit.

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