A magnetic nanoparticle relaxation time detection method and an environmental parameter detection method

Abstract

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

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial measurement technology, and more specifically, relates to a method for detecting the relaxation time of magnetic nanoparticles and a method for detecting environmental parameters. Background Technology

[0002] Magnetic nanoparticles, as a novel type of functional biological probe, have significant potential applications in the study of cellular metabolic activities. For example, the local microenvironment surrounding tumor cells often exhibits increased viscosity and temperature compared to normal cells. Surface-modified magnetic nanoparticles, after intravenous injection, can accumulate around tumor cells through systemic blood circulation. Analyzing the dynamic properties of magnetic nanoparticles under the control of an applied alternating magnetic field can be used to assess parameters of the environment surrounding tumor cells.

[0003] However, current methods typically employ oscillating magnetic fields to detect the relaxation time of magnetic nanoparticles, then use this relaxation time to obtain environmental parameters such as temperature and viscosity. For ease of calculation, the influence of magnetic dipole interactions on the relaxation time is usually ignored. However, when the concentration of magnetic nanoparticles is spatially uneven, especially at high concentrations, the detection of relaxation time is easily affected by the magnetic dipole interactions between particles. These interactions cause directional alignment and radial clustering of the particles, a phenomenon that cannot be ignored and ultimately reduces the reliability of relaxation time detection. Summary of the Invention

[0004] To address the above-mentioned deficiencies or improvement needs of existing technologies, this invention provides a method for detecting the relaxation time of magnetic nanoparticles and a method for detecting environmental parameters. This method solves the problem that existing methods for detecting the relaxation time of magnetic nanoparticles using oscillating magnetic fields often neglect the influence of magnetic dipole interactions on the relaxation time, leading to reduced detection reliability.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for detecting the relaxation time of magnetic nanoparticles is provided, 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.

[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 present invention, in S3 Phase lag corresponding to the first harmonic term Represented as: ; in, This represents the Brownian relaxation time of a particle, in relation to the viscosity of the particle's local environment. Temperature of the local environment of the particle T and the hydrodynamic particle size of magnetic nanoparticles related; Represents the Boltzmann constant. Indicates the concentration of magnetic nanoparticles; This represents the saturation magnetic moment of the magnetic nanoparticles.

[0012] According to the magnetic nanoparticle relaxation time detection method provided by the present invention, in step S3, the Brownian relaxation time of the magnetic nanoparticle is obtained by solving the phase lag corresponding to the third harmonic term.

[0013] According to the magnetic nanoparticle relaxation time detection method provided by the present invention, the phase lag corresponding to the third harmonic term Specifically: ; In the formula, ; ; ; ; ; ; in, and Represent the Langevin factor and magnetic susceptibility of the magnetic nanoparticles, respectively, and the saturation magnetic moment of the particles. and concentration Relevant; among them, Permeability in vacuum This indicates the ambient temperature of the target being measured. This represents the Lang-Zhi-Wan function.

[0014] According to another aspect of the present invention, a method for detecting environmental parameters of magnetic nanoparticles is provided, wherein the Brownian relaxation time of magnetic nanoparticles is obtained by using the magnetic nanoparticle relaxation time detection method described in any of the above claims, and environmental parameters around the magnetic nanoparticles are obtained based on the Brownian relaxation time.

[0015] In summary, compared with the prior art, the magnetic nanoparticle relaxation time detection method and environmental parameter detection method provided by this invention offer the following advantages: 1. Magnetic dipole interaction between magnetic nanoparticles is introduced to correct the relaxation time detection of particle spatial distribution under an applied magnetic field. The influence of magnetic dipole interaction on the detection is improved through model correction. This method can effectively reduce the interference of magnetic dipole interaction on the Brownian relaxation time detection process of magnetic nanoparticles, thereby achieving accurate estimation of the Brownian relaxation time of magnetic nanoparticles. 2. A method for detecting phase lag in the magnetization response of magnetic nanoparticles under a two-dimensional magnetic field is proposed. The two-dimensional magnetic field promotes a more uniform spatial distribution of magnetic nanoparticle concentration, thereby reducing the interference caused by uneven particle concentration distribution and improving detection accuracy. The influence of spatial concentration distribution on detection is improved by using a two-dimensional Helmholtz coil to apply a magnetic field on the experimental setup. The phase lag under relaxation is corrected by introducing magnetic dipole interaction using concentration and saturation magnetic moment. 3. By utilizing the phase lag of the harmonic expansion term of the dynamic magnetization response, the Brownian relaxation time of magnetic nanoparticles can be inverted, and the temperature and viscosity of the local environment can be detected. Attached Figure Description

[0016] Figure 1 This is a flowchart of the magnetic nanoparticle relaxation time detection method provided by the present invention.

[0017] Figure 2 This is a schematic diagram of a two-dimensional magnetic field provided by the present invention.

[0018] Figure 3 This is a schematic diagram of the rotation of magnetic nanoparticles under the influence of a magnetic field provided by the present invention.

[0019] Figure 4 This is a schematic diagram of the phase lag of the third harmonic term of magnetic nanoparticles at different temperatures provided by the present invention.

[0020] Figure 5 This is a schematic diagram of the phase lag of the third harmonic term of magnetic nanoparticles under different viscosities provided by the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0022] Please see Figure 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 to be tested, 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: ; in, This represents the Brownian relaxation time of a particle, in relation to the viscosity of the particle's local environment. Temperature of the local environment of the particle T and the hydrodynamic particle size of magnetic nanoparticles related; Represents the Boltzmann constant. Indicates the concentration of magnetic nanoparticles; This represents the saturation magnetic moment of the magnetic nanoparticles. The properties of these particles can be obtained by pre-calibration.

[0031] Furthermore, the Brownian relaxation time can be obtained through inversion. The temperature of the target sample can then be obtained. and viscosity information.

[0032] Example 1: In actual measurements, since the first-order harmonic term is susceptible to background crosstalk from the excitation magnetic field, the Brownian relaxation time of the magnetic nanoparticles is obtained in S3 by solving for the phase lag corresponding to the third-order harmonic term. The dynamic magnetization response described by the Fokker-Plank equation can be further modified using the AC magnetic field amplitude and the saturation magnetic moment of the magnetic nanoparticles. Based on the trigonometric function relationship between the real and imaginary parts of the magnetization response, the expression for the phase lag of the third-order harmonic term is obtained. Under an applied magnetic field, considering the magnetic dipole interaction between the magnetic nanoparticles, the phase lag corresponding to the third-order harmonic term is... Specifically: ; In the formula, ; ; ; ; ; ; in, and Represent the Langevin factor and magnetic susceptibility of the magnetic nanoparticles, respectively, and the saturation magnetic moment of the particles. and concentration The concentration can refer to the concentration of magnetic nanoparticles in the target sample, and the type of the target sample can be a homogeneous system such as a solution or suspension; among which... Permeability in vacuum This indicates the ambient temperature of the target being measured. This 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, include: 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 the third 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 the third harmonic term and the Brownian relaxation time of the magnetic nanoparticle, the Brownian relaxation time of the magnetic nanoparticle is obtained by solving the problem; wherein the functional relationship includes a correction term introduced by the magnetic dipole interaction of the magnetic nanoparticle. The functional relationship described in S3 specifically introduces a correction term through the concentration and saturation magnetic moment of the magnetic nanoparticles, so as to introduce magnetic dipole interactions using the concentration and saturation magnetic moment; S3 Phase lag corresponding to the first harmonic term Represented as: ； in, This represents the Brownian relaxation time of a particle, in relation to the viscosity of the particle's local environment. Temperature of the local environment of the particle T and the hydrodynamic particle size of magnetic nanoparticles related; Represents Boltzmann's constant. Indicates the concentration of magnetic nanoparticles; This represents the saturation magnetic moment of the magnetic nanoparticles. They represent x shaft and y The amplitude of the axial magnetic field. Represents the angular frequency of the rotating magnetic field; Phase lag corresponding to the third harmonic term Specifically: ； In the formula, ； ； ； ； ； ； in, and Represent the Langevin factor and magnetic susceptibility of the magnetic nanoparticles, respectively, and the saturation magnetic moment of the particles. and concentration Relevant; among them, Permeability in vacuum This indicates the ambient temperature of the target being measured. This represents the Lang-Zhi-Wan function.

2. The method for detecting the relaxation time of magnetic nanoparticles as described in claim 1, characterized in that, The application of 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.

3. The method for detecting the relaxation time of magnetic nanoparticles as described in claim 2, characterized in that, The application of 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.

4. The method for detecting the relaxation time of magnetic nanoparticles as described in claim 2, characterized in that, 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.

5. The method for detecting the relaxation time of magnetic nanoparticles as described in claim 2, characterized in that, S2 in 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.

6. A method for detecting environmental parameters of magnetic nanoparticles, characterized in that, The Brownian relaxation time of magnetic nanoparticles is obtained using the relaxation time detection method of any one of claims 1-5, and environmental parameters around the magnetic nanoparticles are obtained based on the Brownian relaxation time.

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