A method, system and apparatus for characterizing electrical activity of a neural cell

Abstract

The present application belongs to the technical field of neural electrical activity detection and biomedical optical detection, and particularly relates to a neural cell electrical activity characterization method, system and device; the present application combines two-photon microscopic positioning with terahertz photoacoustic detection, determines a local target region related to sodium ion transmembrane transport by using two-photon imaging, and makes the terahertz excitation region correspond to the two-photon positioning region by means of coaxial light paths or spatial registration; meanwhile, by using the sensitivity of terahertz waves to the hydration environment of sodium ions, the change of sodium ion concentration in the target region is converted into collectable photoacoustic signals without the need of electrode insertion or cell membrane damage, so that non-invasive and high-sensitivity detection of local sodium ion change in neural cells is realized.

Description

Technical Field

[0001] This invention belongs to the field of neural electrical activity detection and biomedical optical detection technology, and particularly relates to a method, system and device for characterizing the electrical activity of nerve cells. Background Technology

[0002] Neural electrical activity is the manifestation of information transmission, functional regulation, and brain function expression in the nervous system. When neurons are stimulated, the distribution of ions across the cell membrane changes rapidly, resulting in changes in membrane potential and action potential. Accurate detection of neural electrical activity is of great significance for neuroscience research, brain function analysis, exploration of the mechanisms of neurological diseases, drug screening, and brain-computer interfaces.

[0003] During the generation of an action potential, voltage-gated sodium ion channels open first, allowing sodium ions to rapidly flow across the membrane and trigger membrane depolarization, which is a crucial step in the formation of the neural potential. Compared to the changes in calcium ion signals that occur after the action potential, the dynamic changes in sodium ions are closer in time to the initiation of neural electrical activity. Therefore, if sodium ion-related changes can be detected within local nerve cell regions, it is hoped that a novel detection pathway that more directly reflects neural electrical activity can be established.

[0004] Currently, methods for detecting neural electrical activity mainly include patch-clamp, microelectrode recording, calcium imaging, and voltage-fluorescent probes. Patch-clamp and microelectrode recording can directly acquire electrical signals, but they are usually highly invasive, complex to operate, and prone to disturbing cell membranes and local microenvironments, making it difficult to achieve long-term, low-damage, and simultaneous multi-cell detection. Calcium imaging technology is widely used, but calcium ion signals are secondary responses after action potentials, resulting in time lags and making it difficult to accurately reflect rapid depolarization processes. Although voltage-fluorescent probes can reflect membrane potential changes, they are often limited by weak signals, low signal-to-noise ratios, photobleaching, phototoxicity, and insufficient labeling stability.

[0005] Two-photon microscopy has good tissue penetration, low defocus light damage, and high three-dimensional spatial resolution, making it suitable for locating local structures such as neuronal cell bodies, dendrites, and axons. However, two-photon imaging mainly serves the functions of structural identification and spatial region selection, making it difficult to directly achieve label-free detection of dynamic changes in sodium ions. Terahertz waves are sensitive to ion hydration environments and low-frequency vibration modes. When combined with photoacoustic effects, local terahertz absorption changes can be converted into collectable ultrasonic signals, providing a new technical basis for the detection of sodium ion-related changes.

[0006] However, terahertz photoacoustic detection alone has problems such as insufficient spatial localization ability, strong water background absorption, and unclear source of target cells. In summary, existing methods are still difficult to meet the requirements of low invasiveness, high spatial selectivity, real-time detection, and sodium ion-related functional readout for neural electrical activity detection. Therefore, there is an urgent need for a neural cell electrical activity characterization system and method that combines two-photon high-resolution localization with terahertz photoacoustic sodium ion detection. Summary of the Invention

[0007] Based on the above background, the main objective of this invention is to overcome the shortcomings and deficiencies of existing neural electrical activity detection technologies and provide a method, system, and device for characterizing neural cell electrical activity based on two-photon localization and terahertz photoacoustic detection.

[0008] This invention proposes a system for characterizing the electrical activity of nerve cells, the system comprising: The two-photon excitation module generates femtosecond pulsed lasers using a near-infrared femtosecond laser. The scanning module directs the femtosecond pulsed laser onto a two-dimensional scanning galvanometer. The angle of the two-dimensional scanning galvanometer is adjusted, and the femtosecond pulsed laser is focused onto the nerve cell to be scanned through a high numerical aperture objective lens to complete the scan. The data acquisition and processing module uses a high numerical aperture objective lens to collect fluorescence signals generated by the nerve cells under test, which are then introduced into a fluorescence detector via a dichroic mirror and converted into electrical signals. After data processing, a three-dimensional structural image of the nerve cells under test is reconstructed. The target region identification and spatial localization module uses three-dimensional structural images to identify and spatially locate the nerve cells under test, thereby obtaining local target regions related to sodium ion transmembrane transport. The terahertz excitation module generates terahertz pulses and focuses them to irradiate the local target area of ​​the nerve cell to be tested, thereby causing the local target area to generate photoacoustic signals. The photoacoustic receiving module uses an ultrasonic transducer to receive photoacoustic signals and convert them into electrical signals. The signal processing module processes the electrical signal to obtain the sodium ion concentration or the change in sodium ion concentration in the local target area.

[0009] The present invention also proposes a method for characterizing electrical activity using the above-mentioned neural cell electrical activity characterization system, the method comprising the following steps: Step 1: After beam modulation, the femtosecond pulsed laser is used to scan and image the nerve cells to be tested; Step 2: Collect the fluorescence signal generated by the nerve cell to be tested, convert it into an electrical signal, and then reconstruct the three-dimensional structural image of the nerve cell to be tested through data processing; Step 3: Use three-dimensional structural images to perform target recognition and spatial localization of the nerve cells under test to obtain local target regions related to sodium ion transmembrane transport; Step 4: Based on target recognition and spatial positioning information, adjust the coaxial optical path to achieve spatial overlap between the terahertz excitation region and the two-photon positioning region; Step 5: Terahertz pulses are used to irradiate the local target area of ​​the nerve cell to be tested, causing the local target area to generate photoacoustic signals; Step 6: Acquire photoacoustic signals and convert them into electrical signals. Process the electrical signals to obtain the sodium ion concentration or the change in sodium ion concentration in the local target area.

[0010] The present invention also proposes a device for characterizing the electrical activity of nerve cells, the device comprising: Two-photon excitation equipment generates femtosecond pulsed lasers using a near-infrared femtosecond laser; The scanning device incident a femtosecond pulsed laser onto a two-dimensional scanning galvanometer. The angle of the two-dimensional scanning galvanometer is adjusted, and the femtosecond pulsed laser is focused onto the nerve cells to be tested in the sample cell through a high numerical aperture objective lens to complete the scanning. The data acquisition and processing equipment uses a high numerical aperture objective lens to collect the fluorescence signal generated by the nerve cell under test, which is then introduced into a fluorescence detector through a dichroic mirror and converted into an electrical signal. After data processing, a three-dimensional structural image of the nerve cell under test is reconstructed. Computer equipment uses three-dimensional structural images to perform target recognition and spatial localization of the nerve cells under test, and obtains local target regions related to sodium ion transmembrane transport. The terahertz excitation device generates terahertz pulses, which are then focused by a parabolic mirror and used to irradiate the local target area of ​​the nerve cell to be tested, thereby causing the local target area to generate photoacoustic signals. The photoacoustic receiving device uses an ultrasonic transducer to receive photoacoustic signals and uses a data acquisition card to convert the photoacoustic signals into electrical signals. Computer equipment processes electrical signals to obtain the sodium ion concentration or change in sodium ion concentration in a local target area.

[0011] Compared with the prior art, the present invention has the following advantages: 1. Achieve non-invasive monitoring of local sodium ion changes in nerve cells. This invention fully utilizes the biophysical characteristics of sodium ion transmembrane influx during neuronal action potential generation, which causes changes in local ion concentration and hydration environment. It introduces a technical approach combining two-photon microscopic localization and terahertz photoacoustic detection. Two-photon microscopy acquires three-dimensional spatial information of the target nerve cell and its local structures, identifying target regions closely related to sodium ion transmembrane transport, including cell body membrane regions, axonal proximal segments, dendritic regions, or ion channel enrichment areas. This provides a precise spatial target area for subsequent terahertz photoacoustic detection. After obtaining the precise spatial target area, coaxial optical path and spatial registration design ensure that the two-photon localization optical path and the terahertz excitation optical path spatially overlap in the target region, ensuring that the terahertz pulse can precisely target the sodium ion-related target region identified by the two-photon microscopy. This invention converts changes in sodium ion concentration within the target region into a collectable photoacoustic signal without the need for electrode insertion or cell membrane disruption, thereby achieving non-invasive and highly sensitive detection of local sodium ion changes in nerve cells.

[0012] 2. Enables continuous real-time monitoring By leveraging the high signal-to-noise ratio of photoacoustic signals and a high-speed data acquisition and processing module, the method of this invention is suitable for continuous and real-time monitoring of the dynamic changes of sodium ions, providing new technical means for analyzing neuronal excitation states, elucidating neural circuit functions, and exploring the mechanisms of neurological diseases.

[0013] 3. High safety and suitable for long-term use. This invention uses terahertz non-ionizing radiation as the excitation source, which poses no risk of ionizing damage to the human body. It is suitable for long-term and repeated testing and is expected to be widely used in wearable or bedside monitoring devices.

[0014] In summary, the neural cell electrical activity characterization system proposed in this invention based on two-photon localization and terahertz photoacoustic detection has significant advantages in terms of sensitivity, anti-interference ability, safety and real-time performance, providing new technical means for neural activity analysis, neural circuit analysis and disease mechanism research. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the framework of the neural cell electrical activity characterization system proposed in this invention; Figure 2 This is a flowchart of the neural cell electrical activity characterization method proposed in this invention; Figure 3 This is a schematic diagram of the neural cell electrical activity characterization device proposed in this invention; 1-Femtosecond laser; 2-Collimating lens; 3-Nonlinear crystal SLN; 4-Terahertz metamaterial filter; 5-Parabolic mirror; 6-Focusing lens; 7-Sample cell; 8-Three-dimensional moving stage; 9-Ultrasonic transducer; 10-High numerical aperture objective lens; 11-Two-dimensional scanning galvanometer; 12-Beam expander and collimating lens group; 13-Near-infrared femtosecond laser; 14-Fluorescence detector; 15-Diehroscope; 16-Computer equipment; 17-Data acquisition card. Detailed Implementation

[0017] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0018] This invention proposes a system for characterizing the electrical activity of nerve cells, such as... Figure 1 As shown, the system includes: The two-photon excitation module generates femtosecond pulsed lasers using a near-infrared femtosecond laser. The scanning module directs the femtosecond pulsed laser onto a two-dimensional scanning galvanometer. The angle of the two-dimensional scanning galvanometer is adjusted, and the femtosecond pulsed laser is focused onto the nerve cell to be scanned through a high numerical aperture objective lens to complete the scan. The data acquisition and processing module uses a high numerical aperture objective lens to collect fluorescence signals generated by the nerve cells under test, which are then introduced into a fluorescence detector via a dichroic mirror and converted into electrical signals. After data processing, a three-dimensional structural image of the nerve cells under test is reconstructed. The target region identification and spatial localization module uses three-dimensional structural images to identify and spatially locate the nerve cells under test, thereby obtaining local target regions related to sodium ion transmembrane transport. The terahertz excitation device generates terahertz pulses, which are then focused by a parabolic mirror and used to irradiate the local target area of ​​the nerve cell to be tested, thereby causing the local target area to generate photoacoustic signals. The photoacoustic receiving module uses an ultrasonic transducer to receive photoacoustic signals and convert them into electrical signals. The signal processing module processes the electrical signal to obtain the sodium ion concentration or the change in sodium ion concentration in the local target area.

[0019] Specifically, in the two-photon excitation module, a near-infrared femtosecond laser is used to generate the femtosecond pulsed laser required for two-photon excitation. The excitation wavelength can be selected according to the requirements of fluorescent markers, autofluorescence signals, or imaging of the nerve cells to be tested; in a specific implementation, the excitation wavelength is 800nm / 920nm.

[0020] In one specific embodiment, the two-photon excitation module further includes an optical isolator, a power regulator, and a beam expander and collimating lens group; after passing through the optical isolator, the femtosecond pulsed laser passes through the power regulator and the beam expander and collimating lens group in sequence to adjust the output power, beam diameter, collimation state, and pulse width of the femtosecond pulsed laser so as to meet the requirements of two-photon excitation and imaging of the nerve cells under test.

[0021] Specifically, in the scanning module, the femtosecond pulsed laser after beam shaping is incident on the two-dimensional scanning galvanometer. The two-dimensional scanning galvanometer controls the propagation direction of the laser beam by changing the reflection angle, and the high numerical aperture objective lens focuses it into the nerve cell to be tested, forming a high energy density spot at the focal point of the objective lens that meets the two-photon excitation conditions, thereby inducing two-photon absorption in the focal region.

[0022] In one specific embodiment, the scanning module further includes a three-dimensional moving displacement stage for carrying the nerve cells to be tested. By adjusting the position of the three-dimensional moving displacement stage in the X, Y, and Z directions, scanning imaging of different lateral regions and different axial depth planes can be achieved.

[0023] In one specific embodiment, the data acquisition and processing module further includes a preamplifier, a filter, a data acquisition card, a scan synchronization controller, and a computer device, used to receive fluorescence signals and complete image reconstruction; the fluorescence detector converts the fluorescence signal into an electrical signal, which is then preamplified and filtered before being input into the data acquisition card; the data acquisition card synchronously acquires fluorescence intensity signals, scan synchronization signals, and Z-axis position signals; the computer device reconstructs the fluorescence intensity signal into a two-dimensional two-photon image based on the scan coordinates, and obtains a three-dimensional structural image of the nerve cell under test by superimposing images from different depth planes.

[0024] Specifically, in the target region identification and spatial localization module, the computer device determines the local target region related to sodium ion transmembrane transport based on the morphological structure, fluorescent label distribution, or functional response characteristics of the nerve cell to be tested. This includes the cell body membrane region, the initial segment of the axon, the local dendritic region, the synaptic adjacency region, or the relatively rich region of ion channels. The system records the three-dimensional spatial coordinates of this local target region and uses them as the target region coordinates for subsequent terahertz photoacoustic detection to guide the acquisition of terahertz excitation and sodium ion-related photoacoustic signals.

[0025] In one specific embodiment, the terahertz excitation module further includes a nonlinear crystal SLN (Stoichiometric Lithium Niobate), a collimating lens, and a parabolic mirror. After collimation and shaping, the femtosecond pulsed laser is guided to the nonlinear crystal SLN to generate a broadband strong-field terahertz pulse under phase-matching conditions. The excitation source generates a terahertz pulse with a frequency of 0.2–1.5 THz and a single-pulse energy of 4 uJ. The parabolic mirror 5 is used to focus the terahertz light spot diameter to 1.5 mm and irradiate the nerve cell to be tested, thereby exciting a photoacoustic effect in a local target area.

[0026] In one specific embodiment, the system proposed in this invention further includes a terahertz metamaterial filter located between the nonlinear crystal SLN and the parabolic mirror. The broadband strong-field terahertz pulse is filtered by the terahertz metamaterial filter with adjustable transmission center frequency to obtain narrowband terahertz pulses.

[0027] Specifically, the photoacoustic signal receiving module includes a piezoelectric ultrasonic transducer with an intermediate frequency of 1MHz, a preamplifier, and an acoustic impedance matching layer; this module is used to receive the photoacoustic signal generated by the local thermal expansion caused by terahertz excitation, and to obtain information on the absorption characteristics of the nerve cells under test.

[0028] Specifically, in the signal processing module, the acquisition card in the computer device first converts the photoacoustic signal into an electrical signal, and then performs denoising, deconvolution, and feature extraction on the electrical signal to obtain photoacoustic features related to sodium ions. Based on a pre-stored standard sample calibration database, the computer device establishes a quantitative calibration model between the terahertz photoacoustic signal and the sodium ion concentration, and inputs the measured electrical signal into the model to calculate and output the sodium ion concentration value or concentration change in the target area, providing a basis for the characterization of nerve cell electrical activity.

[0029] This invention also proposes a method for characterizing electrical activity using the aforementioned neural cell electrical activity characterization system, such as... Figure 2 As shown, the method includes the following steps: Step 1: After beam modulation, the femtosecond pulsed laser is used to scan and image the nerve cells to be tested; Step 2: Collect the fluorescence signal generated by the nerve cell to be tested, convert it into an electrical signal, and then reconstruct the three-dimensional structural image of the nerve cell to be tested through data processing; Step 3: Use three-dimensional structural images to perform target recognition and spatial localization of the nerve cells under test to obtain local target regions related to sodium ion transmembrane transport; Step 4: Based on target recognition and spatial positioning information, adjust the coaxial optical path to achieve spatial overlap between the terahertz excitation region and the two-photon positioning region; Step 5: Terahertz pulses are used to irradiate the local target area of ​​the nerve cell to be tested, causing the local target area to generate photoacoustic signals; Step 6: Acquire photoacoustic signals and convert them into electrical signals. Process the electrical signals to obtain the sodium ion concentration or the change in sodium ion concentration in the local target area.

[0030] This invention also proposes a device for characterizing the electrical activity of nerve cells, such as... Figure 3 As shown, the device includes: The two-photon excitation device generates femtosecond pulsed lasers through a near-infrared femtosecond laser 13; The scanning device incident a femtosecond pulsed laser onto a two-dimensional scanning galvanometer 11. The angle of the two-dimensional scanning galvanometer 11 is adjusted, and the femtosecond pulsed laser is focused onto the nerve cells to be tested in the sample cell 7 through a high numerical aperture objective lens 10 to complete the scanning. The data acquisition and processing equipment uses a high numerical aperture objective lens 10 to collect the fluorescence signal generated by the nerve cell under test, which is then introduced into a fluorescence detector 14 via a dichroic mirror 15 and converted into an electrical signal. The data is then processed to reconstruct a three-dimensional structural image of the nerve cell under test. Computer device 16 uses three-dimensional structural images to perform target recognition and spatial localization of the nerve cells to be tested in sample cell 7, and obtains local target regions related to sodium ion transmembrane transport. The terahertz excitation device generates terahertz pulses, which are then focused by the parabolic mirror 5 and irradiated into the local target area of ​​the nerve cell to be tested, causing the local target area to generate photoacoustic signals. The photoacoustic receiving device uses an ultrasonic transducer 9 to receive photoacoustic signals and uses a data acquisition card 17 to convert the photoacoustic signals into electrical signals. Computer device 16 processes electrical signals to obtain the sodium ion concentration or change in sodium ion concentration in a local target area.

[0031] Specifically, the ultrasonic transducer 9 is a piezoelectric ultrasonic transducer.

[0032] Specifically, in the two-photon excitation device, a near-infrared femtosecond laser 13 is used to generate the femtosecond pulsed laser required for two-photon excitation, and the excitation wavelength can be selected according to the requirements of fluorescent markers, autofluorescence signals or imaging of the nerve cells to be tested.

[0033] In one specific embodiment, the two-photon excitation device further includes an optical isolator, a power regulator, and a beam expander and collimator lens group 12; after passing through the optical isolator, the femtosecond pulsed laser passes through the power regulator and the beam expander and collimator lens group 12 in sequence to adjust the output power, beam diameter, collimation state, and pulse width of the femtosecond pulsed laser so as to meet the requirements of two-photon excitation and imaging of the nerve cells under test.

[0034] In one specific embodiment, the terahertz excitation device generates a terahertz pulse, which is then focused by the parabolic mirror 5 and irradiated by the focusing lens 6 onto the local target area of ​​the nerve cell to be tested.

[0035] Specifically, in the scanning device, the femtosecond pulsed laser after beam shaping is incident on the two-dimensional scanning galvanometer 11. The two-dimensional scanning galvanometer 11 controls the propagation direction of the laser beam by changing the reflection angle, and the high numerical aperture objective lens 10 focuses it into the interior of the nerve cell to be tested in the sample cell 7, forming a high energy density spot at the focal point of the objective lens that meets the two-photon excitation conditions, thereby inducing two-photon absorption in the focal region.

[0036] In one specific embodiment, the scanning device further includes a three-dimensional moving displacement stage 8, which adjusts the position of the sample cell 7 in the X, Y, and Z directions to achieve scanning imaging of different lateral regions and different axial depth planes.

[0037] In one specific embodiment, the neural cell electrical activity characterization device further includes a preamplifier, a filter, a data acquisition card 17, a scan synchronization controller, and a computer device 16, used to receive fluorescence signals and complete image reconstruction; the fluorescence detector 14 converts the fluorescence signal into an electrical signal, which is then preamplified and filtered before being input into the data acquisition card 17. The data acquisition card 17 synchronously acquires fluorescence intensity signals, scan synchronization signals, and Z-axis position signals. The computer device 16 reconstructs the fluorescence intensity signal into a two-dimensional two-photon image based on the scan coordinates, and obtains a three-dimensional structural image of the neural cell under test by superimposing images from different depth planes.

[0038] Specifically, the computer device 16 determines the local target region related to sodium ion transmembrane transport based on the morphological structure, fluorescent label distribution, or functional response characteristics of the nerve cell to be tested. This includes the cell body membrane region, the initial segment of the axon, the local dendritic region, the synaptic adjacency region, or the relatively rich region of ion channels. The three-dimensional spatial coordinates of this local target region are recorded and used as the target region coordinates for subsequent terahertz photoacoustic detection to guide the acquisition of terahertz excitation and sodium ion-related photoacoustic signals.

[0039] In one specific embodiment, the terahertz excitation device further includes a nonlinear crystal SLN 3, a collimating lens 2, and a parabolic mirror 5. After collimation and shaping, the femtosecond pulsed laser is guided to the nonlinear crystal SLN 3 to generate a broadband strong-field terahertz pulse under phase-matching conditions. The excitation source generates a terahertz pulse with a frequency of 0.2–1.5 THz and a single pulse energy of 4 μJ. The terahertz light spot diameter is focused to 1.5 mm using the parabolic mirror and irradiated to the nerve cell under test, thereby exciting a photoacoustic effect in a local target area.

[0040] In one specific embodiment, the device proposed in this invention may further include a terahertz metamaterial filter located between the nonlinear crystal SLN 3 and the parabolic mirror 5. The terahertz metamaterial filter with adjustable transmission center frequency is used to filter the broadband strong field terahertz pulse to obtain a narrowband terahertz pulse.

[0041] This invention fully utilizes the biophysical characteristics of sodium ion transmembrane influx during neuronal action potential generation, which causes changes in local ion concentration and hydration environment. It introduces a technical approach combining two-photon microscopic localization and terahertz photoacoustic detection. On one hand, two-photon microscopy acquires three-dimensional spatial information of the target nerve cell and its local structures, identifying target regions closely related to sodium ion transmembrane transport, including cell body membrane regions, axonal proximal segments, dendritic regions, or ion channel enrichment regions, providing a precise spatial target area for subsequent terahertz photoacoustic detection. On the other hand, through coaxial optical path and spatial registration design, the two-photon localization optical path and the terahertz excitation optical path achieve spatial overlap in the target region, ensuring that the terahertz pulse can precisely target the sodium ion-related target region determined by the two-photon microscopy.

[0042] Furthermore, this invention establishes a standard sample calibration database and a correspondence model between terahertz photoacoustic signals and sodium ion concentrations to quantitatively fit and optimize the relationship between terahertz photoacoustic signals collected in the target area and changes in sodium ion concentration. During actual detection, the system inputs the terahertz photoacoustic signals obtained from the two-photon localization area into the pre-stored quantitative calibration model, calculates and outputs the sodium ion concentration value or the change in sodium ion concentration in the target area. Through the synergistic effect of two-photon spatial localization, coaxial terahertz excitation, and photoacoustic signal inversion, this invention can improve the selective extraction capability of sodium ion-related signals in complex neural tissues, providing a novel detection scheme for characterizing the electrical activity of nerve cells.

[0043] In the embodiments provided by this invention, it should be understood that the disclosed apparatus / terminal devices and methods can be implemented in other ways. For example, the apparatus / terminal device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0044] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A system for characterizing the electrical activity of nerve cells, characterized in that, The system includes: The two-photon excitation module generates femtosecond pulsed lasers using a near-infrared femtosecond laser. The scanning module directs the femtosecond pulsed laser onto a two-dimensional scanning galvanometer. The angle of the two-dimensional scanning galvanometer is adjusted, and the femtosecond pulsed laser is focused onto the nerve cell to be scanned through a high numerical aperture objective lens to complete the scan. The data acquisition and processing module uses a high numerical aperture objective lens to collect fluorescence signals generated by the nerve cells under test. These signals are then introduced into a fluorescence detector via a dichroic mirror and converted into electrical signals. Data processing is then used to reconstruct a three-dimensional structural image of the nerve cells under test. The data acquisition and processing module also includes a preamplifier, filter, data acquisition card, scan synchronization controller, and computer equipment, used to receive fluorescence signals and complete image reconstruction. The fluorescence detector converts the fluorescence signals into electrical signals, which are then preamplified and filtered before being input into the data acquisition card. The data acquisition card simultaneously acquires fluorescence intensity signals, scan synchronization signals, and Z-axis position signals. The computer equipment reconstructs a two-dimensional two-photon image from the fluorescence intensity signals based on the scan coordinates and obtains a three-dimensional structural image of the nerve cells under test by superimposing images from different depth planes. The target region identification and spatial localization module uses three-dimensional structural images to identify and spatially locate the nerve cells under test, thereby obtaining local target regions related to sodium ion transmembrane transport. In the target region identification and spatial localization module, the computer device determines the local target regions related to sodium ion transmembrane transport based on the morphological structure, fluorescent label distribution, or functional response characteristics of the nerve cells under test. The terahertz excitation module generates terahertz pulses and focuses them to irradiate the local target area of ​​the nerve cell to be tested, thereby causing the local target area to generate photoacoustic signals. The photoacoustic receiving module uses an ultrasonic transducer to receive photoacoustic signals and convert them into electrical signals. The signal processing module processes the electrical signal to obtain the sodium ion concentration or the change in sodium ion concentration in the local target area.

2. The neural cell electrical activity characterization system according to claim 1, characterized in that, The two-photon excitation module also includes an optical isolator, a power regulator, and a beam expander and collimating lens group; after passing through the optical isolator, the femtosecond pulsed laser passes through the power regulator and the beam expander and collimating lens group in sequence to adjust the output power, beam diameter, collimation state, and pulse width of the femtosecond pulsed laser.

3. The neural cell electrical activity characterization system according to claim 1, characterized in that, The scanning module also includes a three-dimensional moving stage for carrying the nerve cells to be tested. By adjusting the position of the three-dimensional moving stage in the X, Y, and Z directions, scanning imaging of different lateral regions and different axial depth planes can be achieved.

4. The neural cell electrical activity characterization system according to claim 1, characterized in that, In the target area identification and spatial positioning module, the system records the three-dimensional spatial coordinates of the local target area and uses them as the target area coordinates for subsequent terahertz photoacoustic detection, which is used to guide the acquisition of terahertz excitation and sodium ion-related photoacoustic signals.

5. The neural cell electrical activity characterization system according to claim 1, characterized in that, The terahertz excitation module also includes a nonlinear crystal SLN (Stoichiometric Lithium Niobate), a collimating lens, and a parabolic mirror; after collimation and shaping, the femtosecond pulsed laser is guided to the nonlinear crystal SLN to generate a broadband strong-field terahertz pulse under phase-matching conditions.

6. The neural cell electrical activity characterization system according to claim 1, characterized in that, The system also includes a terahertz metamaterial filter, which is located between the nonlinear crystal SLN and the parabolic mirror. The terahertz metamaterial filter with adjustable transmission center frequency is used to filter broadband strong field terahertz pulses to obtain narrowband terahertz pulses.

7. A method for characterizing the electrical activity of neural cells, implemented using the neural cell electrical activity characterization system according to any one of claims 1-6, characterized in that, The method includes the following steps: Step 1: After beam modulation, the femtosecond pulsed laser is used to scan and image the nerve cells to be tested; Step 2: Collect the fluorescence signal generated by the nerve cell to be tested, convert it into an electrical signal, and then reconstruct the three-dimensional structural image of the nerve cell to be tested through data processing; Step 3: Use three-dimensional structural images to perform target recognition and spatial localization of the nerve cells under test to obtain local target regions related to sodium ion transmembrane transport; Step 4: Based on target recognition and spatial positioning information, adjust the coaxial optical path to achieve spatial overlap between the terahertz excitation region and the two-photon positioning region; Step 5: Terahertz pulses are used to irradiate the local target area of ​​the nerve cells to be tested, causing the local target area to generate photoacoustic signals; Step 6: Acquire photoacoustic signals and convert them into electrical signals. Process the electrical signals to obtain the sodium ion concentration or the change in sodium ion concentration in the local target area.

8. A device for characterizing the electrical activity of nerve cells, characterized in that, The device includes: The two-photon excitation device generates femtosecond pulsed lasers through a near-infrared femtosecond laser (13); The scanning device incident a femtosecond pulsed laser onto a two-dimensional scanning galvanometer (11), and through the angle adjustment of the two-dimensional scanning galvanometer (11), the femtosecond pulsed laser is focused onto the nerve cells to be tested in the sample cell (7) by a high numerical aperture objective lens (10) to complete the scanning. The data acquisition and processing equipment uses a high numerical aperture objective lens (10) to collect the fluorescence signal generated by the nerve cell to be tested, which is then introduced into a fluorescence detector (14) via a dichroic mirror (15) and converted into an electrical signal. The data is then processed to reconstruct a three-dimensional structural image of the nerve cell to be tested. The computer device (16) uses a three-dimensional structural image to perform target recognition and spatial localization of the nerve cell under test, and obtains the local target region related to sodium ion transmembrane transport; the computer device (16) determines the local target region related to sodium ion transmembrane transport based on the morphological structure, fluorescent label distribution or functional response characteristics of the nerve cell under test. The terahertz excitation device generates terahertz pulses and focuses them through a parabolic mirror (5) to irradiate the local target area of ​​the nerve cell to be tested, thereby causing the local target area to generate photoacoustic signals. The photoacoustic receiving device uses an ultrasonic transducer (9) to receive photoacoustic signals and uses a data acquisition card (17) to convert the photoacoustic signals into electrical signals. The data acquisition and processing equipment also includes a preamplifier, a filter, a data acquisition card (17), and a scanning synchronization controller, used to receive fluorescence signals and complete image reconstruction; the fluorescence detector converts the fluorescence signal into an electrical signal, which is then preamplified and filtered before being input into the data acquisition card, and the data acquisition card synchronously acquires the fluorescence intensity signal, the scanning synchronization signal, and the Z-axis position signal; the computer device (16) reconstructs the fluorescence intensity signal into a two-dimensional two-photon image based on the scanning coordinates, and obtains a three-dimensional structural image of the nerve cell to be tested by superimposing images of different depth planes; the computer device (16) processes the electrical signal to obtain the sodium ion concentration or the change in sodium ion concentration in the local target area.

9. The neural cell electrical activity characterization device according to claim 8, characterized in that, The two-photon excitation device also includes an optical isolator, a power regulator, and a beam expander collimating lens group (12); after passing through the optical isolator, the femtosecond pulse laser passes through the power regulator and the beam expander collimating lens group (12) in sequence to adjust the output power, beam diameter, collimation state, and pulse width of the femtosecond pulse laser.

Images