Cytoplasmic viscosity detection method based on magnetic particle Brownian relaxation and its application

Abstract

The present invention provides a method for detecting cytoplasmic viscosity based on Brownian relaxation of magnetic particles, comprising: obtaining the relaxation time of paramagnetic particles through the response of paramagnetic particles enriched in the cells to be tested to the magnetic field; obtaining the viscosity value of the cytoplasm of the cells to be tested through the relationship curve between the relaxation time and the cytoplasmic viscosity of the cells to be tested. The cytoplasmic viscosity detection technology based on Brownian relaxation of magnetic particles provided by the present invention uses magnetic particles to mark cells, realizes viscosity measurement by detecting the Brownian relaxation time of magnetic particles in the cytoplasm, and displays the cell state through the cytoplasmic viscosity of the sample. For example, for cells of the same type, an increase in cytoplasmic viscosity indicates that the cells are apoptotic, so the cytoplasmic viscosity distribution of the sample indicates the proportion of apoptotic cells and the vitality of the overall cell sample, realizing the cytoplasmic viscosity detection of in vitro cultured cells in an in vitro environment and after being re-infused into a living environment.

Description

Technical Field

[0001] The invention relates to the field of biological analysis and detection, and in particular to a cytoplasmic viscosity detection method based on magnetic particle Brownian relaxation and an application thereof. Background Art

[0002] Cytoplasm refers to the components of a cell that are surrounded by a cell membrane, except for the nucleus and organelles. It is a colloid substance rich in protein, with a certain viscosity and fluidity. The cytoplasm not only provides a place for various metabolic reactions, energy exchange and material exchange in the cell, but also provides the necessary ion environment to maintain the integrity of various organelles and the cell as a whole.

[0003] As a fluid substance, the viscosity of cytoplasm is an important biomechanical characteristic that can be used to evaluate the physiological state of cells, determine cell viability, and distinguish different cell types. At the same time, cytoplasmic viscosity will in turn affect the behavior and function of cells. However, current technology cannot non-invasively evaluate the cytoplasmic viscosity of target cells at the living level. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a cytoplasmic viscosity detection technology based on magnetic particle Brownian relaxation, which realizes the cytoplasmic viscosity detection and application of in vitro cultured cells in an in vitro environment and after being re-injected into a living environment.

[0005] The present invention provides a method for detecting cytoplasmic viscosity based on magnetic particle Brownian relaxation, comprising:

[0006] Obtaining the relaxation time of the paramagnetic particles through the response of the paramagnetic particles enriched in the cells to be tested to the magnetic field;

[0007] The viscosity value of the cytoplasm of the cell to be tested is obtained through the relationship curve between the relaxation time and the cytoplasm viscosity of the cell to be tested.

[0008] Furthermore, the step of obtaining the relaxation time of the paramagnetic particles by measuring the response of the paramagnetic particles enriched in the cells to be tested to the magnetic field comprises:

[0009] Enriching the paramagnetic particles into the cells to be tested to obtain magnetically labeled cell samples;

[0010] Using a square waveform alternating magnetic field to excite the paramagnetic particles in the magnetically labeled cell sample to obtain a magnetization response signal generated by the paramagnetic particles under the alternating magnetic field;

[0011] Integrating the magnetization response signal during a constant magnetic field time period of the alternating magnetic field to obtain a magnetization variation curve of the paramagnetic particles;

[0012] The magnetization variation curve of the paramagnetic particles is subjected to inverse Laplace transformation to obtain the relaxation time in the sample.

[0013] Furthermore, obtaining the viscosity value of the cytoplasm of the cell to be tested through the relationship curve between the relaxation time and the cytoplasm viscosity of the cell to be tested comprises:

[0014] The relaxation time is introduced into the Brownian relaxation time-viscosity standard curve of the paramagnetic particles to obtain the viscosity value of the cytoplasm of the cells to be tested.

[0015] Furthermore, the Brownian relaxation time-viscosity standard curve is obtained by dispersing the paramagnetic particles in glycerol-physiological saline standard samples of different viscosities and measuring their standard Brownian relaxation times respectively;

[0016] The standard Brownian relaxation time is fitted with the viscosity of the standard sample to obtain the Brownian relaxation time-viscosity standard curve.

[0017] Further, wherein the paramagnetic particles include:

[0018] A type of superparamagnetic material particle whose surface is modified by polyethylene glycol, ferritin, transmembrane peptide, or fusion peptide.

[0019] Furthermore, the paramagnetic particles include one of ferroferric oxide, manganese-doped ferroferric oxide, and iron oxide.

[0020] Furthermore, the field strength |H| of the alternating magnetic field is 1-10 mT, and the excitation frequency is 1-5 kHz.

[0021] Furthermore, the proportion of the rising / falling segments in the square wave of the alternating magnetic field is set to 5-10% of the cycle.

[0022] Another aspect of the present invention provides a method for detecting cytoplasmic viscosity for use in in vitro cultured cell viability identification, drug cytotoxicity detection, and in vivo transfusion cell viability detection.

[0023] A method for in vivo detection using a cytoplasm viscosity detection method, comprising:

[0024] washing the cells to be tested enriched with the paramagnetic particles;

[0025] Transmitting the cells to be tested into a living body;

[0026] The cytoplasm viscosity detection method is used to perform detection to obtain the viscosity value of the cytoplasm of the cells to be detected in the organism.

[0027] It can be seen from the above technical solutions that the cytoplasmic viscosity detection method based on magnetic particle Brownian relaxation and its application provided by the present invention have the following beneficial effects:

[0028] (1) The cytoplasmic viscosity detection technology based on magnetic particle Brownian relaxation provided by the present invention realizes the cytoplasmic viscosity detection of in vitro cultured cells in an in vitro environment and after being reinfused into a living environment.

[0029] (2) The cytoplasmic viscosity detection technology based on magnetic particle Brownian relaxation provided by the present invention uses magnetic particles to mark cells, and realizes viscosity measurement by detecting the Brownian relaxation time of magnetic particles in the cytoplasm, and displays the cell state through the sample cytoplasmic viscosity. For example, for the same type of cells, increased cytoplasmic viscosity indicates cell apoptosis, so the cytoplasmic viscosity distribution of the sample indicates the proportion of apoptotic cells and the vitality of the overall cell sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0031] Figure 1 It is a waveform diagram of the square waveform alternating magnetic field of the present invention;

[0032] Figure 2 It is the magnetization response signal generated by the paramagnetic particles of the present invention under an alternating magnetic field;

[0033] Figure 3 is the magnetization variation curve of the paramagnetic particles of the present invention;

[0034] Figure 4 is the Brownian relaxation time-viscosity standard curve of the paramagnetic particles of the present invention;

[0035] Figure 5 The relaxation time component and distribution diagram are generated by performing an inverse Laplace transformation on the magnetization variation curve of the paramagnetic particles in the present invention;

[0036] Figure 6 It is a flow chart of the cytoplasmic viscosity detection based on magnetic particle Brownian relaxation according to the present invention;

[0037] Figure 7 It is an example of the relaxation detection system described in the present invention. DETAILED DESCRIPTION

[0038] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0039] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0040] At present, the mainstream methods for measuring cytoplasmic viscosity include the use of fluorescence polarization, fluorescence lifetime and viscosity-sensitive fluorescent probes. However, these methods all rely on optical imaging technology. Since photons are easily disturbed by medium absorption and scattering, optical detection methods are only applicable to the detection of transparent media and in vitro cultured cells. Usually, these cytoplasmic viscosity measurement techniques are only suitable for sampling detection, and cells stained with fluorescent agents can no longer be cultured or used normally.

[0041] In addition, for biomedical applications involving cell injection and transplantation in vivo, such as CAR-T cell therapy, stem cell therapy, NK cell therapy, etc., if the cytoplasmic viscosity of target cells can be evaluated at the in vivo level, it will help researchers understand the state and activity of cells after entering the body, which is of great significance for optimizing cell dosage and experimental conditions. However, current technology cannot non-invasively evaluate the cytoplasmic viscosity of target cells at the in vivo level.

[0042] Based on the above background, the present invention proposes a novel cytoplasm viscosity detection principle and method, which can be used for the cytoplasm viscosity detection of cells cultured in vitro and cells transfused in vivo.

[0043] According to the general inventive concept of one aspect of the present invention, a method for detecting cytoplasmic viscosity based on magnetic particle Brownian relaxation is provided, comprising:

[0044] Step 1: Obtain the relaxation time of the paramagnetic particles through the response of the paramagnetic particles enriched in the cells to be tested to the magnetic field;

[0045] Step 2: Obtain the viscosity value of the cytoplasm of the cell to be tested through the relationship curve between the relaxation time and the cytoplasm viscosity of the cell to be tested.

[0046] The cytoplasm viscosity detection technology based on magnetic particle Brownian relaxation provided by the present invention realizes the cytoplasm viscosity detection of in vitro cultured cells in an ex vivo environment and after being reinfused into a living environment.

[0047] The cytoplasmic viscosity detection technology based on magnetic particle Brownian relaxation provided by the present invention uses magnetic particles to mark cells, and realizes viscosity measurement by detecting the Brownian relaxation time of magnetic particles in the cytoplasm, and displays the cell state through the sample cytoplasmic viscosity. For example, for the same type of cells, increased cytoplasmic viscosity indicates cell apoptosis, so the cytoplasmic viscosity distribution of the sample indicates the proportion of apoptotic cells and the vitality of the overall cell sample.

[0048] Figure 1 It is a waveform diagram of the waveform alternating magnetic field of the present invention.

[0049] Figure 2 It is the magnetization response signal generated by the paramagnetic particles of the present invention under an alternating magnetic field.

[0050] Figure 3 It is the magnetization variation curve of the paramagnetic particles of the present invention.

[0051] Figure 5 The relaxation time component and distribution diagram are generated by performing an inverse Laplace transformation on the magnetization variation curve of the paramagnetic particles in the present invention.

[0052] Furthermore, in step 1, obtaining the relaxation time of the paramagnetic particles by the response of the paramagnetic particles enriched in the cells to be tested to the magnetic field comprises:

[0053] S1: Enriching paramagnetic particles into cells to be tested to obtain magnetically labeled cell samples;

[0054] S2: Figure 1 and Figure 2 As shown, a square waveform alternating magnetic field is used to excite the paramagnetic particles in the magnetically labeled cell sample to obtain the magnetization response signal generated by the paramagnetic particles under the alternating magnetic field;

[0055] S3: Figure 3 As shown, the magnetization response signal is integrated during the constant magnetic field time period of the alternating magnetic field to obtain the magnetization variation curve of the paramagnetic particles;

[0056] S4: Figure 5 As shown, the magnetization change curve of the paramagnetic particles is subjected to an inverse Laplace transform to obtain the relaxation time in the sample.

[0057] Furthermore, S1 specifically includes magnetically labeling cells in a culture dish or culture bottle, then washing and collecting the cells, and suspending them in physiological saline or cell culture medium for detection.

[0058] Furthermore, in S1, the paramagnetic particles include a type of superparamagnetic material particles whose surface is modified by polyethylene glycol, ferritin, transmembrane peptide, or fusion peptide.

[0059] Furthermore, in S1, the paramagnetic particles include one of ferroferric oxide, manganese-doped ferroferric oxide, and iron oxide.

[0060] Preferably, in S1, the paramagnetic particles are superparamagnetic iron oxide nanoparticles with a particle size of less than 100 nm.

[0061] Furthermore, in S1, the cells to be tested may be various animal cells such as tumor cells, T cells, stem cells, etc.

[0062] Furthermore, in S1, paramagnetic particles are enriched in the cells to be tested. Generally, magnetic particles and cells are co-incubated for modification. Physical conditions such as external magnetic field, external ultrasound, microfluidic device, etc. can also be used to increase the enrichment of magnetic particles in cells.

[0063] Further, S2 is specifically that the magnetization response of the magnetic particles under the excitation of the square waveform alternating magnetic field is detected by electromagnetic induction, the magnetization of the magnetic particles changes with the excitation field, and a voltage signal u(t) is induced in the electromagnetic coil. The magnetization of the magnetic particles M(t) and the voltage signal in the electromagnetic coil are shown in formula (1):

[0064]

[0065] Furthermore, in S2, the field strength |H| of the alternating magnetic field is 1-10 mT, and the excitation frequency is 1-5 kHz.

[0066] Further, in S2, the proportion of the rising / falling segments in the square wave of the alternating magnetic field is set to 5-10% of the cycle.

[0067] Furthermore, S3 is specifically to select a time period (t 0 to 1 ) integrates the signal u(t) to obtain the change curve of the magnetization of the magnetic particles, as shown in formula (2):

[0068]

[0069] The change of magnetization of magnetic particles is affected by the relaxation mechanism of magnetic particles, including Brownian relaxation and Neel relaxation. The double exponential model is used to fit the M(t) change curve. The result is shown in formula (3):

[0070]

[0071] Where M(t) is the magnetization at time t, M max is the maximum magnetization of the sample detected under the square wave excitation field, a N is the Neil relaxation component, τ N is the Neil relaxation time, a B is the Brownian relaxation component, τ B is the Brownian relaxation time, t 0 It is the starting time of the constant magnetic field segment in square wave excitation.

[0072] Furthermore, in S3, since the cytoplasmic viscosity of the sample to be tested has a certain distribution, the change in the magnetization of the sample satisfies the following model, as shown in formula (4):

[0073]

[0074] Where M(t) is the magnetization of the sample at time t, M max is the maximum magnetization of the sample detected under square wave magnetic field excitation, a N is the Neil relaxation component, τ N is the Neil relaxation time, a Bj are different Brownian relaxation components, τ Bj is the Brownian relaxation time, t 0 It is the starting time of the constant magnetic field segment in square wave excitation.

[0075] Further, S4 specifically comprises: using inverse Laplace transform to analyze the magnetization variation curve of the sample to obtain different relaxation time components and their distribution in the sample;

[0076] τ Bj The Brownian relaxation time-viscosity (τ B -η) standard curve to obtain the cytoplasmic viscosity η in the sample j and the proportion of cells with different viscosities

[0077] Furthermore, step 2 is specifically to obtain the viscosity value of the cytoplasm of the cell to be tested through the relationship curve between the relaxation time and the cytoplasm viscosity of the cell to be tested, including:

[0078] The relaxation time is introduced into the Brownian relaxation time-viscosity standard curve of paramagnetic particles to obtain the viscosity value of the cytoplasm of the cells to be tested.

[0079] Figure 4 This is the Brownian relaxation time-viscosity standard curve of the paramagnetic particles of the present invention.

[0080] Further, such as Figure 4 As shown, in step 2, the Brownian relaxation time-viscosity standard curve is obtained by dispersing paramagnetic particles in glycerol-normal saline standard samples of different viscosities, and measuring their standard Brownian relaxation times respectively;

[0081] The standard Brownian relaxation time is fitted with the viscosity of the standard sample to obtain a Brownian relaxation time-viscosity standard curve.

[0082] Furthermore, in step 2, the values ​​of the parameters in the model are obtained by fitting, and the Brownian relaxation time τ is obtained. B There is a linear relationship with the viscosity of the magnetic particle environment, as shown in formula (5):

[0083]

[0084] Where V H is the hydrated particle size of the magnetic particles, η is the ambient viscosity of the magnetic particles, and T is the ambient temperature.

[0085] For the same type of magnetic particles at the same physiological temperature, the factor that affects the Brownian relaxation time is mainly the viscosity of the environment in which the magnetic particles are located.

[0086] A cytoplasmic viscosity detection method is used in the identification of in vitro cultured cell viability, drug cytotoxicity detection, and in vivo transfusion cell viability detection.

[0087] A method for in vivo detection using a cytoplasm viscosity detection method, comprising:

[0088] Washing the cells to be tested enriched with paramagnetic particles;

[0089] The cells to be tested are introduced into the organism;

[0090] The cytoplasm viscosity detection method is used to perform detection to obtain the viscosity value of the cytoplasm of the cells to be detected in the organism.

[0091] The cytoplasm viscosity detection technology based on magnetic particle Brownian relaxation provided by the present invention realizes the cytoplasm viscosity detection of in vitro cultured cells in an ex vivo environment and after being reinfused into a living environment.

[0092] The cytoplasmic viscosity detection technology based on magnetic particle Brownian relaxation provided by the present invention uses magnetic particles to mark cells, and realizes viscosity measurement by detecting the Brownian relaxation time of magnetic particles in the cytoplasm, and displays the cell state through the sample cytoplasmic viscosity. For example, for the same type of cells, increased cytoplasmic viscosity indicates cell apoptosis, so the cytoplasmic viscosity distribution of the sample indicates the proportion of apoptotic cells and the vitality of the overall cell sample.

[0093] Figure 6 This is a flow chart of the cytoplasmic viscosity detection based on magnetic particle Brownian relaxation described in the present invention.

[0094] like Figure 6 As shown, the cytoplasmic viscosity detection method based on magnetic particle Brownian relaxation provided by the present invention specifically includes:

[0095] Prepare paramagnetic particle standard solutions of different viscosities;

[0096] Acquire the signal of the standard solution under square wave excitation;

[0097] Analyze and obtain the Brownian relaxation time of the standard solution;

[0098] Establish Brownian relaxation time-viscosity standard curve;

[0099] Paramagnetic particles are used to label the cell samples to be tested;

[0100] Square wave excitation to obtain cell sample signals;

[0101] Obtain the Brownian relaxation time component of the cell sample;

[0102] Obtain the cytoplasmic viscosity of cell samples and the proportion of cells with different viscosities.

[0103] Figure 7 This is an example of the relaxation detection system described in the present invention.

[0104] like Figure 7 As shown, the method for detecting cytoplasmic viscosity based on magnetic particle Brownian relaxation provided by the present invention adopts a monitoring system connected to an acquisition card or a computer;

[0105] The detection system includes an excitation circuit system having an electric coil and a receiving circuit system for signal acquisition.

[0106] The technical solution of the present invention is described in detail below through preferred embodiments. It should be noted that the specific embodiments below are only used for illustration and are not used to limit the present invention.

[0107] Example 1: Establishment of Brownian relaxation time-viscosity (τ_B-η) standard curve of paramagnetic particles

[0108] Glycerol and physiological saline were mixed in different proportions to prepare standard solutions with different viscosities in the range of 0.80-10 cP, and the magnetic particles were evenly dispersed therein.

[0109] Transfer the different standard solutions containing magnetic particles into 500 μl Eppendorf tubes and place Figure 7 The magnetic particle relaxation detection system shown.

[0110] The magnetic particle standard solution was excited by a square wave alternating magnetic field with a field strength of 5 mT, a frequency of 2 kHz, and a rise ratio of 5%, and the response signals generated by standard solutions of different viscosities were obtained.

[0111] The signal of the magnetic field constant time period in the square wave excitation magnetic field is integrated to obtain the change curve M(t) of the magnetization of the standard solution.

[0112] Perform an inverse Laplace transform on the M(t) curve to obtain the Neel and Brown relaxation times τ of the standard solution N , τ B .

[0113] According to the Brownian relaxation time of magnetic particles in different viscosity standard solutions, the Brownian relaxation-viscosity (τ B -η) standard curve.

[0114] Example 2: Magnetic particle labeling of cells

[0115] In this method, poly-lysine-modified iron oxide nanoparticles (Fe 3 O 4Take breast cancer 4T1 cells labeled with PLL as an example, the operation process is as follows:

[0116] Breast cancer 4T1 cells were cultured in a culture dish. When the cells were passaged to the third generation, Fe 3 O 4 -PLL, until the iron concentration in the culture medium reaches 25 μg / ml, incubate at 37°C, 5% CO 2 Incubate in the incubator for 24 hours.

[0117] The culture medium was removed and the cells were repeatedly rinsed with phosphate-buffered saline.

[0118] The cells were digested with trypsin, collected by centrifugation and resuspended in phosphate buffered saline.

[0119] Example 3: Detection of nonlinear magnetic response signals of magnetically labeled cells

[0120] Transfer the magnetically labeled cell suspension into a 500 μl Eppendorf tube and place Figure 7 In the magnetic particle imaging system shown.

[0121] The magnetically labeled cells were stimulated by a square wave alternating magnetic field with a field strength of 7.5 mT, a frequency of 2 kHz, and a rise ratio of 10%, and the response signals generated by the magnetically labeled cells were obtained.

[0122] Example 4: Analysis of Cytoplasmic Viscosity of Magnetic Labeled Cells

[0123] The signal of the constant magnetic field time period in the square wave excitation magnetic field is integrated to obtain the change curve M(t) of the magnetization amount of the magnetically labeled cells.

[0124] Perform an inverse Laplace transform on the M(t) curve to obtain the Neel and Brown relaxation times τ of the magnetically labeled cell samples. N , τ B .

[0125] The Brownian relaxation time τ B Substitute Fe 3 O 4 - Brownian relaxation time of PLL particles - viscosity (τ B -η) standard curve to obtain the viscosity value of the cytoplasm of the cell sample.

[0126] The terms "first", "second", etc. are used to distinguish similar objects rather than to describe or indicate a particular order or sequence.

[0127] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or also includes elements inherent to such process, method, article, or apparatus / device.

[0128] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for detecting cytoplasmic viscosity based on magnetic particle Brownian relaxation, characterized in that: include: The relaxation time of the paramagnetic particles is obtained by the response of the paramagnetic particles enriched in the cells to be tested to the magnetic field: Enriching the paramagnetic particles into the cells to be tested to obtain magnetically labeled cell samples; Using a square waveform alternating magnetic field to excite the paramagnetic particles in the magnetically labeled cell sample to obtain a magnetization response signal generated by the paramagnetic particles under the alternating magnetic field; The magnetization response signal is integrated during the constant magnetic field time period of the alternating magnetic field to obtain the magnetization variation curve of the paramagnetic particles: Select the time period when the magnetic field is constant during square wave excitation to calculate the magnetization response signal Integrate to obtain the magnetization of magnetic particles The change curve: ； in, to is a constant time period; The double exponential model was used to Perform the fit: ； in for The magnetization at the moment, is the maximum magnetization of the sample detected under the square wave excitation field, is the Neil relaxation component, Relaxation time for Neil, is the Brownian relaxation component, is the Brownian relaxation time, is the starting time of the constant magnetic field segment in square wave excitation; Performing an inverse Laplace transformation on the magnetization variation curve of the paramagnetic particles to obtain the relaxation time in the sample; The viscosity value of the cytoplasm of the cell to be tested is obtained through the relationship curve between the relaxation time and the cytoplasm viscosity of the cell to be tested.

2. The method for detecting cytoplasmic viscosity according to claim 1, characterized in that: Obtaining the viscosity value of the cytoplasm of the cell to be tested by using the relationship curve between the relaxation time and the cytoplasm viscosity of the cell to be tested comprises: The relaxation time is introduced into the Brownian relaxation time-viscosity standard curve of the paramagnetic particles to obtain the viscosity value of the cytoplasm of the cells to be tested.

3. The method for detecting cytoplasmic viscosity according to claim 2, characterized in that: The Brownian relaxation time-viscosity standard curve is prepared by dispersing the paramagnetic particles in glycerol-physiological saline standard samples of different viscosities and measuring their standard Brownian relaxation times respectively; The standard Brownian relaxation time is fitted with the viscosity of the standard sample to obtain the Brownian relaxation time-viscosity standard curve.

4. The method for detecting cytoplasmic viscosity according to claim 1, characterized in that: The paramagnetic particles include: A type of superparamagnetic material particle whose surface is modified by polyethylene glycol, ferritin, transmembrane peptide, or fusion peptide.

5. The method for detecting cytoplasmic viscosity according to claim 1, characterized in that: The paramagnetic particles include one of ferroferric oxide, manganese-doped ferroferric oxide, and iron oxide.

6. The method for detecting cytoplasmic viscosity according to claim 1, characterized in that: The field strength of the alternating magnetic field is 1-10 mT, and the excitation frequency is 1-5 kHz.

7. The method for detecting cytoplasmic viscosity according to claim 1, characterized in that: The proportion of the rising / falling sections in the square wave of the alternating magnetic field is set to 5-10% of the cycle.

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