Magnetic nanoparticle relaxation time detection method and environmental parameter detection method

Abstract

The invention belongs to the technical field related to nanometer material testing, and discloses a magnetic nanoparticle relaxation time detection method and an environmental parameter detection method, and the method comprises the following steps: applying an excitation magnetic field around a to-be-detected target mixed with magnetic nanoparticles; obtaining magnetization response generated by the magnetic nanoparticles in any direction of the magnetic field plane, and obtaining phase lag corresponding to any order harmonic term of the magnetization response; according to the function relationship between the phase lag corresponding to any harmonic term and the Brown relaxation time of the magnetic nanoparticles, solving and obtaining the Brown relaxation time of the magnetic nanoparticles; wherein the function relationship comprises a correction term introduced by magnetic dipole interaction of the magnetic nanoparticles. The magnetic dipole interaction among the magnetic nanoparticles is introduced, relaxation time detection of particle space distribution under an external magnetic field is corrected, the interference of the magnetic dipole interaction on the magnetic nanoparticle Brown relaxation time detection process can be effectively reduced, and accurate estimation of the magnetic nanoparticle Brown relaxation time is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanomaterial measurement, and more particularly relates to a magnetic nanoparticle relaxation time detection method and an environmental parameter detection method. BACKGROUND

[0002] As a new type of functional biological probe, magnetic nanoparticles have very important potential application value in the research of cell metabolic activity. For example, the local microenvironment around tumor cells often shows an increase in viscosity and an increase in temperature compared to normal cells. After surface modification, the magnetic nanoparticles can be enriched around the tumor cells under the action of systemic blood circulation after intravenous injection. Under the regulation of an external alternating magnetic field, the dynamic characteristics of the magnetic nanoparticles can be analyzed to evaluate the environmental parameters around the tumor cells.

[0003] However, the current method for detecting the relaxation time of magnetic nanoparticles generally uses an oscillating magnetic field, and then the environmental parameters such as temperature and viscosity are obtained based on the relaxation time. In order to facilitate calculation, the influence of magnetic dipole interaction on the relaxation time is generally ignored. However, when the concentration of magnetic nanoparticles has a spatial distribution, especially in the case of high concentration, the detection of relaxation time is easily affected by the magnetic dipole interaction between particles. The magnetic dipole interaction between magnetic nanoparticles can cause directional arrangement and radial clustering of particles, which often cannot be ignored, and ultimately leads to a decrease in the reliability of relaxation time detection. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the present application provides a magnetic nanoparticle relaxation time detection method and an environmental parameter detection method, which are used to solve the problem that the current method for detecting the relaxation time of magnetic nanoparticles uses an oscillating magnetic field, and the influence of magnetic dipole interaction on the relaxation time is generally ignored, resulting in a decrease in detection reliability.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present application, a magnetic nanoparticle relaxation time detection method is provided, comprising: S1, applying an excitation magnetic field around a target to be detected mixed with magnetic nanoparticles; S2, obtaining the magnetization response of the magnetic nanoparticles in any one direction of the magnetic field plane, and obtaining the phase lag corresponding to any harmonic term of the magnetization response through phase-sensitive detection or lock-in amplification method; S3, solving the Brownian relaxation time of the magnetic nanoparticles according to the functional relationship of the phase lag corresponding to any harmonic term with respect to the Brownian relaxation time of the magnetic nanoparticles; wherein the functional relationship includes a correction term introduced by the magnetic dipole interaction of the magnetic nanoparticles.

[0006] According to the magnetic nanoparticle relaxation time detection method provided by the present invention, the application of an excitation magnetic field in S1 specifically includes: A two-dimensional Helmholtz coil is used to form a circle around the target. xy A two-dimensional magnetic field in a plane, wherein the two-dimensional Helmholtz coils correspond to... x shaft and y Axial direction.

[0007] According to the magnetic nanoparticle relaxation time detection method provided by the present invention, the application of the excitation magnetic field in S1 further includes: By controlling the two-dimensional Helmholtz coil, the two-dimensional magnetic field can be made into a circular rotating magnetic field, an elliptical rotating magnetic field, or an oscillating magnetic field.

[0008] According to the magnetic nanoparticle relaxation time detection method provided by the present invention, the change of the two-dimensional magnetic field with time Specifically as follows: ; in, t Indicates time, They represent x shaft and y The amplitude of the axial magnetic field. Indicates the initial phase. Represents the angular frequency of the rotating magnetic field; and They represent shaft and Unit vector along the axis.

[0009] According to the magnetic nanoparticle relaxation time detection method provided by the present invention, S2 and x The included angle of the axis is Magnetization response generated by directional magnetic nanoparticles for: ; in, It is an odd number. for The amplitude of the first harmonic term, For magnetization response of Phase lag corresponding to the first harmonic term t Indicates time, Indicates the initial phase. This represents the angular frequency of the rotating magnetic field.

[0010] According to the magnetic nanoparticle relaxation time detection method provided by the present invention, the functional relationship in S3 specifically introduces a correction term by means of the concentration and saturation magnetic moment of the magnetic nanoparticles, so as to introduce magnetic dipole interaction by means of the concentration and saturation magnetic moment.

[0011] According to the magnetic nanoparticle relaxation time detection method provided by the application, the Brownian relaxation time of the magnetic nanoparticle is obtained according to the phase lag corresponding to the third-order harmonic term in S3. The phase lag corresponding to the third-order harmonic term is is expressed as: ; Wherein, represents the Brownian relaxation time of the particle, and the viscosity of the local environment of the particle , the temperature of the local environment of the particle T and the hydrodynamic diameter of the magnetic nanoparticle ; represents the Boltzmann constant, represents the concentration of the magnetic nanoparticle; represents the saturation magnetic moment of the magnetic nanoparticle.

[0012] According to the magnetic nanoparticle relaxation time detection method provided by the application, the Brownian relaxation time of the magnetic nanoparticle is obtained according to the phase lag corresponding to the third-order harmonic term in S3.

[0013] According to the magnetic nanoparticle relaxation time detection method provided by the application, the phase lag corresponding to the third-order harmonic term is Specifically, ; In the formula, ; ; ; ; ; ; Wherein, and respectively represent the corresponding Langevin factor and magnetic susceptibility of the magnetic nanoparticle, and the saturation magnetic moment of the particle and the concentration ; wherein, is the permeability in vacuum, represents the environmental temperature where the target to be measured is located, represents the Langevin function.

[0014] According to another aspect of the application, a magnetic nanoparticle environment parameter detection method is provided, which obtains the Brownian relaxation time of the magnetic nanoparticle by using the magnetic nanoparticle relaxation time detection method of any one of the above, and obtains the environmental parameters around the magnetic nanoparticle based on the Brownian relaxation time.

[0015] Overall, compared with the prior art, the magnetic nanoparticle relaxation time detection method and the environmental parameter detection method provided by the application have the following advantages: 1. The magnetic dipole interaction between the magnetic nanoparticles is introduced to correct the relaxation time detection of the spatial distribution of the particles under an applied magnetic field, the influence of the magnetic dipole interaction on the detection is improved through model correction, the interference of the magnetic dipole interaction on the Brownian relaxation time detection process of the magnetic nanoparticles can be effectively reduced by using the method, and then the accurate estimation of the Brownian relaxation time of the magnetic nanoparticles is realized; 2. A detection method for the phase lag of the magnetization response of the magnetic nanoparticles under a two-dimensional magnetic field is provided, which is beneficial to making the concentration spatial distribution of the magnetic nanoparticles more uniform under the driving action of the two-dimensional magnetic field, so as to reduce the interference caused by the uneven particle concentration distribution and improve the detection accuracy; the influence of the concentration spatial distribution on the detection is improved on the experimental device by using the two-dimensional Helmholtz coil to apply a magnetic field; the magnetic dipole interaction is introduced by using the concentration and the saturation magnetic moment, and the phase lag under the relaxation effect can be corrected; 3. The phase lag of the dynamic magnetization response harmonic expansion term is used to inverse the Brownian relaxation time of the magnetic nanoparticles, and the temperature and viscosity of the local environment can be detected. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a flow chart of the magnetic nanoparticle relaxation time detection method provided by the application.

[0017] Figure 2 is a two-dimensional magnetic field schematic diagram provided by the application.

[0018] Figure 3 is a schematic diagram of the rotation of the magnetic nanoparticles under the action of a magnetic field provided by the application.

[0019] Figure 4 is a phase lag schematic diagram of the 3rd harmonic term of the magnetic nanoparticles at different temperatures provided by the application.

[0020] Figure 5 is a phase lag schematic diagram of the 3rd harmonic term of the magnetic nanoparticles at different viscosities provided by the application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and do not limit the application. In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as they do not conflict with each other.

[0022] Please refer toFigure 1 This embodiment provides a method for detecting the relaxation time of magnetic nanoparticles, the method comprising: S1, apply an excitation magnetic field around the target object mixed with magnetic nanoparticles; S2, obtain the magnetization response generated by magnetic nanoparticles in any direction of the magnetic field plane, and obtain the phase hysteresis corresponding to any harmonic term of the magnetization response by phase-sensitive detection or lock-in amplification method; S3. Based on the functional relationship between the phase lag corresponding to any harmonic term and the Brownian relaxation time of the magnetic nanoparticle, solve to obtain the Brownian relaxation time of the magnetic nanoparticle; wherein the functional relationship includes a correction term introduced by the magnetic dipole interaction of the magnetic nanoparticle.

[0023] In some embodiments, applying the excitation magnetic field in S1 specifically includes: A two-dimensional Helmholtz coil is used to form a circle around the target. xy A two-dimensional magnetic field in a plane, wherein the two-dimensional Helmholtz coils correspond to... x shaft and y Axial direction.

[0024] Specifically, the specific steps of the magnetic nanoparticle relaxation time detection method provided in this embodiment are as follows: First, the target object mixed with magnetic nanoparticles is placed in the detection area; a two-dimensional Helmholtz coil is used to detect the relaxation time of magnetic nanoparticles in the detection area. and When a magnetic field is applied along the axis, a magnetic field can be formed in the area to be detected. Two-dimensional magnetic fields in a plane, such as Figure 2 As shown. The two-dimensional Helmholtz coil corresponds to... x direction and y In terms of direction, the target to be tested can be placed in the middle of the two-dimensional Helmholtz coil, and the internal area of ​​the two-dimensional Helmholtz coil is the area to be tested.

[0025] The change of the two-dimensional magnetic field over time Specifically as follows: ; in, t Indicates time, They represent x shaft and y The amplitude of the axial magnetic field. Indicates the initial phase. Represents the angular frequency of the rotating magnetic field; and They represent shaft and Unit vector along the axis.

[0026] Furthermore, applying the excitation magnetic field in S1 also includes: By controlling the two-dimensional Helmholtz coil, the two-dimensional magnetic field can be made into a circular rotating magnetic field, an elliptical rotating magnetic field, or an oscillating magnetic field. Specifically, when... and When they are equal, the rotating magnetic field is a circular rotating magnetic field; when... or At that time, the rotating magnetic field becomes an oscillating magnetic field.

[0027] In magnetic field Driven by the magnetic field, the target sample containing magnetic nanoparticles within the detection area aligns along the magnetic field direction under the influence of magnetic potential energy and rotates with the magnetic field. During the Brownian relaxation time... Under the influence of the external magnetic field, the magnetic moment direction of the magnetic nanoparticles exhibits a certain phase lag with the direction of the applied magnetic field. As shown in Figure 3.

[0028] In rotating magnetic field Under the influence of, take In a two-dimensional plane, with x The included angle of the axis is Magnetization response generated by directional magnetic nanoparticles for: ; in, It is an odd number. for The amplitude of the first harmonic term, For magnetization response of Phase lag corresponding to the first harmonic term t Indicates time, Indicates the initial phase. This represents the angular frequency of the rotating magnetic field.

[0029] Therefore, in In a two-dimensional plane and The included angle of the axis is A magnetic sensor is placed in an oriented position to measure the magnetization response generated by the magnetic nanoparticles. It can be measured by phase-sensitive detection or phase-locked amplification methods. Phase lag corresponding to the first harmonic term .

[0030] Specifically, the functional relationship described in S3 introduces a correction term using the concentration and saturation magnetic moment of the magnetic nanoparticles, thereby incorporating magnetic dipole interactions based on these factors. Considering the interaction between magnetic dipoles of the magnetic nanoparticles, in S3... Phase lag corresponding to the first harmonic term Represented as: ; wherein, represents the Brownian relaxation time of the particle, and the viscosity of the local environment of the particle , the temperature of the local environment of the particle T and the hydrodynamic diameter of the magnetic nanoparticle ; represents the Boltzmann constant, represents the concentration of the magnetic nanoparticle; represents the saturation magnetization of the magnetic nanoparticle. The properties of these particles can be calibrated in advance.

[0031] Further, the Brownian relaxation time can be obtained by inversion, i.e. the temperature and the viscosity information of the target sample can be obtained.

[0032] Example 1: In the actual measurement process, the Brownian relaxation time of the magnetic nanoparticle is solved and obtained according to the phase lag of the third harmonic term in S3 due to the first harmonic term susceptible to background interference of the excitation magnetic field. The dynamic magnetization response described by the Fokker-Plank equation can be further corrected using the alternating current magnetic field amplitude and the saturation magnetization of the magnetic nanoparticle, and the expression of the phase lag of the third harmonic term can be obtained according to the trigonometric function relationship between the real part and the imaginary part of the magnetization response. Under the external magnetic field, considering the magnetic dipole interaction between the magnetic nanoparticles, the phase lag of the third harmonic term Specifically, ; In the formula, ; ; ; ; ; ; wherein, and respectively represent the corresponding Langevin factor and magnetic susceptibility of the magnetic nanoparticle, and the saturation magnetization and the concentration of the particle, the concentration can be the concentration of the magnetic nanoparticle in the target to be measured, and the type of the target sample to be measured can be, for example, a homogeneous system such as a solution, a suspension, etc.; wherein, is the magnetic permeability in vacuum, represents the environmental temperature of the target to be measured, represents the Langevin function.

[0033] Furthermore, this embodiment also provides a method for detecting environmental parameters of magnetic nanoparticles. First, the Brownian relaxation time of the magnetic nanoparticles is obtained using any of the aforementioned magnetic nanoparticle relaxation time detection methods. Then, environmental parameters surrounding the magnetic nanoparticles are obtained based on the Brownian relaxation time. Environmental parameters, such as temperature or viscosity, can be obtained through multiple detections or fitting based on the formula for the Brownian relaxation time.

[0034] like Figure 4 As shown, the magnetic moments are 1~5×10⁻⁶ respectively. -17 A·m 2 Phase lag corresponding to the third harmonic term of magnetic nanoparticles With temperature changes. Figure 5 As shown, the magnetic moment is 1~5×10⁻⁶. -17 A·m 2 Phase hysteresis corresponding to the third harmonic term of magnetic nanoparticles Variation with temperature. Through phase hysteresis. By conducting the test, the temperature or viscosity of the magnetic nanoparticles can be determined.

[0035] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting the relaxation time of magnetic nanoparticles, characterized in that, The method comprises the following steps: S1, applying an excitation magnetic field around the target to be detected mixed with magnetic nanoparticles; S2, obtaining the magnetization response of the magnetic nanoparticles in any one direction of the magnetic field plane, and obtaining the phase lag corresponding to any harmonic term of the magnetization response through phase-sensitive detection or lock-in amplification method; S3, obtaining the Brownian relaxation time of the magnetic nanoparticles according to the function relationship of the phase lag corresponding to any harmonic term with respect to the Brownian relaxation time of the magnetic nanoparticles; wherein the function relationship includes a correction term introduced by the magnetic dipole interaction of the magnetic nanoparticles.

2. The magnetic nanoparticle relaxation time detection method of claim 1, wherein, The application of the excitation magnetic field in S1 specifically comprises: A two-dimensional Helmholtz coil is used to form a planar two-dimensional magnetic field around the target to be measured, wherein the two-dimensional Helmholtz coil corresponds to the xy axis and x axis direction, respectively. y axis direction, respectively.

3. The magnetic nanoparticle relaxation time detection method of claim 2, wherein, The application of the excitation magnetic field in S1 further comprises: By controlling the two-dimensional Helmholtz coil, the two-dimensional magnetic field is a circular rotating magnetic field, an elliptical rotating magnetic field or an oscillating magnetic field.

4. The method for detecting the relaxation time of magnetic nanoparticles as described in claim 2, characterized in that, The two-dimensional magnetic field changes over time In detail, as follows: ； wherein t denotes time, denote respectively x the axis and y the amplitude of the axial magnetic field, denotes the initial phase, denotes the angular frequency of the rotating magnetic field; and denote respectively the axis and the axial unit vector.

5. The method for detecting the relaxation time of magnetic nanoparticles as described in claim 2, characterized in that, In S2, with x The angle between the axis Magnetization response generated by magnetic nanoparticles in the direction Is: ； wherein is odd, is the amplitude of the mth harmonic term, is the magnetization response is the phase lag corresponding to the mth harmonic term, t denotes time, denotes the initial phase, denotes the angular frequency of the rotating magnetic field.

6. The magnetic nanoparticle relaxation time detection method of claim 4, wherein the magnetic nanoparticle relaxation time detection method is a method for detecting a magnetic nanoparticle relaxation time by using a magnetic nanoparticle having a core-shell structure in which a magnetic core is coated with a shell. In S3, the function relationship specifically introduces a correction term by the concentration and saturation magnetic moment of the magnetic nanoparticles to introduce the magnetic dipole interaction by using the concentration and saturation magnetic moment.

7. The magnetic nanoparticle relaxation time detection method of claim 6, wherein the magnetic nanoparticle relaxation time detection method is a method for detecting a magnetic nanoparticle relaxation time by using a magnetic field gradient generated by a magnetic field gradient generator. In S3 Phase lag corresponding to the third harmonic term is expressed as: ； wherein, represents the Brownian relaxation time of the particle, the viscosity of the local environment of the particle , the temperature of the local environment of the particle T and the hydrodynamic diameter of the magnetic nanoparticle ; represents the Boltzmann constant, represents the concentration of the magnetic nanoparticle; represents the saturation magnetization of the magnetic nanoparticle.

8. The magnetic nanoparticle relaxation time detection method of claim 7, wherein the magnetic nanoparticle relaxation time detection method is a method for detecting a magnetic nanoparticle relaxation time by using a magnetic field gradient generated by a magnetic field gradient generator. In S3, the Brownian relaxation time of the magnetic nanoparticles is obtained according to the phase lag corresponding to the third harmonic term.

9. The magnetic nanoparticle relaxation time detection method of claim 8, wherein, Phase lag corresponding to 3rd harmonic term Specifically: ； In the formula, ； ； ； ； ； ； wherein, and respectively represent the Langevin factor and the magnetic susceptibility corresponding to the magnetic nanoparticle, and the saturation magnetic moment and the concentration of the nanoparticle; wherein, is the magnetic permeability in vacuum, represents the ambient temperature in which the target to be measured is located, represents the Langevin function.

10. A method for detecting an environmental parameter of magnetic nanoparticles, characterized by, The Brownian relaxation time of the magnetic nanoparticles is obtained by using the magnetic nanoparticle relaxation time detection method according to any one of claims 1-9, and the environmental parameters around the magnetic nanoparticles are obtained based on the Brownian relaxation time.

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