Temperature measuring device and temperature measuring method

Abstract

[Problem] To provide a temperature measuring device capable of measuring a cell temperature in a living body. [Solution] This temperature measuring device consists of a quantum dot 1, a light emitting unit 2, a light detecting unit 3, a light intensity ratio calculating unit 4, a calibration curve storage unit 5, and a temperature calculating unit 6. The quantum dot 1 has a core-shell type structure. A core 10 of the quantum dot 1 has crystal defects. The light emitting unit 2 is a device for emitting exciting light onto the quantum dot 1. The light detecting unit 3 is a device for measuring a light intensity I1 at a peak wavelength of band edge emission, and a light intensity I2 at a peak wavelength of defect emission. The light intensity ratio calculating unit 4 is a device for calculating a light intensity ratio I2 / I1. The calibration curve storage unit 5 is a device for storing a calibration curve representing a correspondence between the light intensity ratio I2 / I1 and a temperature at the periphery of the quantum dot 1. The temperature calculating unit 6 is a device for calculating the temperature at the periphery of the quantum dot 1 from the light intensity ratio I2 / I1 and the calibration curve.

Description

[Technical Field]

[0001] This disclosure relates to a temperature measurement device and a temperature measurement method using core-shell type quantum dots. [Background technology]

[0002] In recent years, regenerative medicine technology has advanced remarkably, and it has become clear that the cell temperature of stem cells and regenerating cells greatly affects higher-level regenerative functions (such as regenerative factor production ability, differentiation ability, engraftment ability, and sensing ability). Therefore, there is a need for technology to accurately measure cell temperature.

[0003] Conventional methods for measuring cell temperature include the following:

[0004] Non-patent document 1 describes a method for measuring cell temperature by utilizing the fact that the fluorescence intensity of quantum dots changes with temperature.

[0005] Non-patent document 2 describes measuring the temperature of COS7 cells (monkey kidney-derived cells) by utilizing the temperature dependence of the fluorescence lifetime change of a polymer fluorescent probe.

[0006] Non-patent document 3 describes the development of tsGFP, a temperature sensor protein, and the measurement of temperature distribution in organelles by changes in tsGFP fluorescence.

[0007] Non-patent document 4 describes measuring the intracellular temperature of HepG2 cells (human liver cancer cell line) using a micro thermocouple.

[0008] Non-patent documents 5-7 describe measuring cell temperature using fluorescent nanodiamonds. [Prior art documents] [Patent Documents]

[0009] [Non-Patent Document 1] Scientific Reports, 6, 22071 (2016) [Non-Patent Document 2] Nature Communications, 3, 705 (2012) [Non-Patent Document 3] Nature Methods, 10, 1232 (2013) [Non-Patent Document 4] Scientific Reports, 7, 1721 (2017) [Non-Patent Document 5] Nature 500, 54 (2013) [Non-Patent Document 6] ACS Nano 11, 12077 (2017) [Non-Patent Document 7] Nanoscale Advances, 2, 1859 (2020) [Overview of the project] [Problems that the invention aims to solve]

[0010] However, the method described in Non-Patent Document 1 cannot be applied to measuring the temperature of cells in a living organism because the fluorescence intensity changes depending on the depth within the organism.

[0011] Furthermore, the methods described in Non-Patent Documents 2-4 have problems with fluorescence intensity and light resistance, as well as with biological permeability, and therefore, in vivo measurements have not been realized.

[0012] Furthermore, Non-Patent Documents 5-7 state that the fluorescence wavelength of fluorescent nanodiamonds is visible light, and, similar to Non-Patent Documents 2-4, there is a problem with biological permeability. In addition, it is necessary to irradiate the fluorescent nanodiamonds with electromagnetic waves, and it is extremely difficult to irradiate electromagnetic waves to a specific location deep within the body, so it cannot be used for measuring temperature inside the body at present.

[0013] Therefore, the purpose of this disclosure is to provide a temperature measuring device and a temperature measuring method capable of measuring the temperature of cells in a living organism. [Means for solving the problem]

[0014] The present disclosure relates to a core-shell type quantum dot disposed near a measurement object, having a core with crystal defects and a shell covering the core, a light irradiation unit that irradiates the quantum dot with excitation light having a wavelength of energy greater than the band gap energy of the core, a light detection unit that measures the light intensity at the peak wavelength of the band-edge emission of the quantum dot and the light intensity at the peak wavelength of the defect emission of the quantum dot, a light intensity ratio calculation unit that calculates the light intensity ratio of the two light intensities detected by the light detection unit, a calibration curve storage unit that stores a calibration curve showing the relationship between the light intensity ratio and the temperature around the quantum dot, and a temperature calculation unit that calculates the temperature of the measurement object from the light intensity ratio calculated by the light intensity ratio calculation unit and the calibration curve stored in the calibration curve storage unit. A thermometer characterized by having.

Advantages of the Invention

[0015] According to the present disclosure, the temperature of cells in a living body can be measured.

Brief Description of the Drawings

[0016] [Figure 1] A diagram showing the configuration of the thermometer of the first embodiment. [Figure 2] Band diagram of core 10 of quantum dot 1. [Figure 3] TEM image of quantum dot 1. [Figure 4] A graph showing the result of measuring the fluorescence spectrum of quantum dot 1. [Figure 5] A graph showing the spectrum of defect emission. [Figure 6] A graph showing the temperature dependence of the spectrum of defect emission of quantum dot 1. [Figure 7] A graph showing the temperature dependence of the light intensity I1 at the peak wavelength of the band-edge emission and the light intensity I2 at the peak wavelength of the defect emission. [Figure 8] A graph showing the temperature dependence of the light intensity ratio I2 / I1 for quantum dot 1 in an aqueous solution. [Figure 9]This graph shows the temperature dependence of the light intensity ratio I2 / I1 for quantum dot 1 within ASCs. [Figure 10] A graph showing the temperature dependence of the light intensity ratio I2 / I1. [Figure 11] A graph showing the temperature dependence of the light intensity ratio I2 / I1. [Figure 12] A graph plotting the light intensity ratio I2 / I1 under three conditions on a calibration curve. [Figure 13] A graph showing the results of measuring the fluorescence spectrum of quantum dot 1. [Modes for carrying out the invention]

[0017] (Principle of temperature measurement) First, the temperature measurement principle of this disclosure will be explained. The inventors investigated whether it was possible to measure the temperature inside a living organism using quantum dots. The inventors focused on the energy level structure of core-shell type quantum dots and discovered that the ratio of the light intensity of the band-edge emission peak to the defect emission peak changes linearly with the ambient temperature around the quantum dot. The temperature measurement device and temperature measurement method of this disclosure use this correspondence between light intensity ratio and temperature as a calibration curve and calculates the temperature by measuring the light intensity ratio.

[0018] (First Embodiment) Figure 1 shows the configuration of the temperature measuring device according to the first embodiment. As shown in Figure 1, the temperature measuring device according to the first embodiment consists of a quantum dot 1, a light irradiation unit 2, a light detection unit 3, a light intensity ratio calculation unit 4, a calibration curve storage unit 5, and a temperature calculation unit 6.

[0019] Quantum dot 1 is used as a probe for temperature measurement. By placing quantum dot 1 near the object to be measured, the temperature of the object is measured. Of course, quantum dot 1 and the object to be measured may be in contact. Quantum dot 1 is a semiconductor particle in which the quantum confinement effect is observed due to its small diameter. Quantum dot 1 uses a core-shell structure. The core-shell structure consists of a spherical core 10 and a shell 11 that covers the core 10. The shell 11 maintains the energy levels of the core 10 and protects it from deactivation.

[0020] The core 10 of quantum dot 1 has crystal defects. Figure 2 shows the band diagram of the core 10 of quantum dot 1. As shown in Figure 2, crystal defect levels are formed in the band gap due to the crystal defects. Therefore, some of the carriers generated by irradiation with excitation light (light with energy greater than the band gap energy) recombine and emit light at the band edge, while some are trapped in the crystal defect levels and then recombine to emit light at the defect level. Consequently, the fluorescence spectrum of the core 10 of quantum dot 1 has peaks for band edge emission and defect emission. Furthermore, the defect emission peak is at a longer wavelength than the band edge emission peak. The peak wavelength of defect emission may change depending on the surrounding environment of quantum dot 1.

[0021] The material for the core 10 of quantum dot 1 can be any semiconductor material that forms crystal defects, such as group II-VI semiconductors, group III-V semiconductors, group IV-VI semiconductors, group I-VI semiconductors, group I-III-V semiconductors, and group I-II-IV-VI semiconductors. For example, AgInS2, AgInSe2, AgInTe2, AgInGaS, AgInZnS2, AgInTe2, AgInZnTe2, AgInGaSe2, CuInS2, CuInSe2, InP, and GaP can be used. For biological temperature measurement, materials that do not contain highly toxic elements such as Cd and Pb are preferable.

[0022] The material of the shell 11 of quantum dot 1 can be any material that can protect the core 10, such as ZnS, GaS, ZnGaS, ZnO, In2S3, GaSx These can be used.

[0023] The bandgap energy of the core 10 of quantum dot 1 is determined by factors such as the type of material and the diameter of the core 10. Therefore, by changing these factors, the bandgap energy can be controlled, and thus the peak wavelength of band-edge emission and the peak wavelength of defect emission can be controlled. In the case of a multi-component material, the bandgap energy can be controlled by the composition ratio. For example, when using AgInGaS, the bandgap energy can be controlled by the composition ratio of Ag, In, and Ga.

[0024] The difference between the peak wavelength of band-edge emission and the peak wavelength of defect emission is preferably 100 nm or more. If the difference is 100 nm or more, the two peaks can be sufficiently separated and detected, making it possible to accurately measure the light intensity ratio I2 / I1.

[0025] The diameter of the core 10 of quantum dot 1 is arbitrary as long as the quantum confinement effect appears, for example, 100 nm or less. Here, the diameter is the diameter of the circumscribing sphere of quantum dot 1. Preferably, it is 50 nm or less, and more preferably 20 nm or less. There is no particular lower limit for the diameter, but for example, it is 1 nm or more. The thickness of the shell 11 of quantum dot 1 is arbitrary as long as it can protect the core 10. The shell 11 does not have to be single-layered and may be double-layered or more.

[0026] Various substances may be bound to the surface of quantum dot 1. For example, hydrophilic groups such as hydroxyl groups, amino groups, carboxyl groups, sulfo groups, and their salts may be bound. This makes quantum dot 1 water-soluble, improving the convenience of temperature measurement in living organisms. In addition, membrane-permeable peptides or cationic liposomes may be bound to the surface of quantum dot 1. This allows cells to take up quantum dot 1, making it possible to measure the temperature inside the cell. Examples of membrane-permeable peptides include octaarginine (R8) and TAT peptide.

[0027] The light irradiation unit 2 is a device that irradiates the quantum dot 1 with excitation light. The wavelength of the excitation light to be irradiated can be any wavelength as long as the energy is greater than the band gap energy of the core 10 of the quantum dot 1. For example, LEDs, LDs, xenon lamps, etc., can be used. When measuring the temperature of living organisms, it is preferable to use infrared light, which has high biotransparency, as the excitation light. In particular, the wavelength range of 700 to 1500 nm, which has high transmittance of both hemoglobin and water, is preferred. For example, the wavelength of the excitation light is set to 700 to 1500 nm, and the diameter of the quantum dot 1 and the material composition ratio are adjusted so that the peak wavelength of the band edge emission of the quantum dot 1 is longer than the wavelength of the excitation light. An example of a quantum dot 1 material that can use infrared light as excitation light is AgInGaSe2. Figure 13 is quoted from the paper (Tatsuya Kameyama, et al., ACS Appl. Nano Mater. 2020, 3, 3275-3287), and shows Ag x In y Ga (1-y) This graph shows the fluorescence spectrum of a quantum dot composed of Se2. Here, the molar ratio x of Ag is fixed at 0.67, and the molar ratio y of In to the sum of In and Ga is varied from 0.25 to 1. As shown in Figure 13, as y increases, the band-edge emission peak shifts to longer wavelengths, and it can be seen that when y is 0.6 or higher, the band-edge emission peak is above 740 nm. The defect emission peak is observed at longer wavelengths than the band-edge emission peak, and this peak is clearly visible when y is between 0.25 and 0.5. When y is 0.6 or higher, the defect emission peak is present but not clearly defined. Therefore, it can be seen that when y is 0.6 or higher, both band-edge emission and defect emission can be excited with near-infrared light. For example, when y = 0.6, the band-edge emission peak is at 740 nm and the defect emission peak is at 840 nm, indicating that excitation is possible with excitation light with wavelengths between 700 nm and 740 nm. In this way, by adjusting the material and composition ratio of quantum dot 1, infrared light (especially wavelengths of 700-1500 nm) can be used as excitation light.

[0028] The photodetector 3 is a device that detects band-edge emission and defect emission from the quantum dot 1 and measures the light intensity I1 at the peak wavelength of the band-edge emission and the light intensity I2 at the peak wavelength of the defect emission. For example, the fluorescence spectrum from the quantum dot 1 is measured, and the light intensities I1 and I2 are measured by extracting the band-edge emission peak and the defect emission peak. The fluorescence spectrum is obtained by scanning the fluorescence wavelength with a spectrometer and measuring the light intensity with a photomultiplier tube or photodiode. A fluorescence intensity meter can be used as the light irradiation unit 2 and the photodetector 3. Alternatively, a fluorescence image may be acquired using a fluorescence imaging device, and the light intensities I1 and I2 may be measured by analyzing the fluorescence image. If there are multiple defect emission peaks, any one of them may be used as I2, or the average of any two or more may be taken.

[0029] For accuracy, the light intensities I1 and I2 are preferably at the peak position, but slightly shifted light intensities are also acceptable. For example, a shift of within 20 nm from the peak is sufficient for accurate temperature measurement. Alternatively, the light intensities I1 and I2 may be the average of the light intensities within a predetermined wavelength range including the peak. The predetermined wavelength range is preferably 30 nm or less, more preferably 20 nm or less.

[0030] The light intensity ratio calculation unit 4 is a device that calculates the light intensity ratio I2 / I1 from the light intensity I1 at the peak wavelength of band-edge emission measured by the photodetector unit 3 and the light intensity I2 at the peak wavelength of defect emission. The light intensity ratio calculation unit 4 is implemented by a computer.

[0031] The calibration curve storage unit 5 is a device that stores calibration curves showing the correspondence between the light intensity ratio I2 / I1 and the temperature around the quantum dot 1. Multiple calibration curves are stored for each ambient environment of the quantum dot 1. The light intensity ratio I2 / I1 and temperature correspond one-to-one and are approximately linear, with a negative slope. That is, with temperature T (°C), the relationship is expressed as T = -a(I2 / I1) + b, where a and b are positive real numbers. a and b are determined by the ambient environment of the quantum dot 1. More specifically, they are determined by the materials in the path from the light irradiation unit 2 to the quantum dot 1 and the path from the quantum dot 1 to the photodetector unit 3. Therefore, a and b are experimentally determined according to the ambient environment of the quantum dot 1 and stored in the calibration curve storage unit 5. Note that the relationship between the light intensity ratio I2 / I1 and temperature may be stored as is, without approximating it with a linear relationship, or it may be approximated by other functions.

[0032] The temperature calculation unit 6 is a device that calculates the temperature around the quantum dot 1 from the light intensity ratio I2 / I1 calculated by the light intensity ratio calculation unit 4 and the calibration curve stored in the calibration curve storage unit 5. The temperature calculation unit 6 is implemented by a computer.

[0033] Next, we will describe the measurement of temperature using the temperature measuring device of the first embodiment.

[0034] First, the quantum dot 1 is placed near the object to be measured. The method of placement is arbitrary. When measuring the temperature of a specific part of a living organism, it is preferable to attach a hydrophilic group to the surface of the quantum dot 1 and dissolve the quantum dot 1 in water to make an aqueous solution. The quantum dot 1 can be easily placed in a specific part of the living organism by injection of the aqueous solution. When measuring the temperature inside a living organism, the excitation light wavelength should be infrared, which has high biopenetration, for example, a wavelength of 700 to 1500 nm. Therefore, the quantum dot 1 should have a band gap energy smaller than that. Furthermore, when measuring the temperature inside a cell, it is preferable to attach a membrane-permeable peptide to the surface of the quantum dot 1 and allow the quantum dot 1 to be taken up into the cell.

[0035] Next, the light irradiation unit 2 irradiates the quantum dot 1 with excitation light. Then, the photodetector 3 detects the light from the quantum dot 1 and measures the light intensity I1 at the peak wavelength of the band-edge emission of the quantum dot 1 and the light intensity I2 at the peak wavelength of the defect emission. If the excitation light is infrared, even if the quantum dot 1 is inside a living organism, the excitation light will penetrate the living organism and reach the quantum dot 1 with sufficient intensity. In addition, the fluorescence from the quantum dot 1 will also penetrate the living organism and reach the photodetector 3 with sufficient intensity.

[0036] Next, the light intensity ratio calculation unit 4 calculates the light intensity ratio I2 / I1.

[0037] Next, the temperature calculation unit 6 calculates the temperature around the quantum dot 1 from the light intensity ratio I2 / I1 calculated by the light intensity ratio calculation unit 4 and the calibration curve stored in the calibration curve storage unit 5. Since the quantum dot 1 is placed near the object to be measured, the temperature around the quantum dot 1 is the same as the temperature of the object to be measured. Here, the calibration curve is selected according to the environment surrounding the quantum dot 1. The selection of the calibration curve may be done manually or automatically.

[0038] As described above, the temperature measuring device of the first embodiment can measure the temperature of an object to be measured around the quantum dot 1. In particular, the temperature measuring device of the first embodiment can measure the temperature of a specific part inside a living organism, and by placing the quantum dot 1 inside or around a cell, it is possible to measure the temperature of a cell. For example, it is possible to measure the internal temperature of an organoid. Furthermore, the temperature measuring device of the first embodiment can measure temperature with high precision, and can measure with an accuracy of error of 0.1K or less.

[0039] In the first embodiment, the light intensity ratio I2 / I1 is calculated, but the light intensity ratio I1 / I2 may be calculated, and the temperature may be calculated from a calibration curve showing the correspondence between the light intensity ratio I1 / I2 and temperature.

[0040] Furthermore, quantum dot 1 can also function as a fluorescent probe for labeling biological samples. Therefore, the temperature measuring device of the first embodiment can measure the temperature of a specific part of a living organism while visualizing that specific part using the fluorescence of quantum dot 1.

[0041] The following describes specific embodiments of this disclosure with reference to the figures, but is not limited to these embodiments. [Examples]

[0042] A core-shell type quantum dot 1, with AgInGaS as the core and ZnGaS as the shell, was fabricated using the following method.

[0043] First, silver acetate (Ag(OAc)) (13 mg), indium acetylacetonate (In(acac)3) (31 mg), and gallium acetylacetonate (Ga(acac)3) (18 mg) as metal sources, and powdered sulfur (7.4 mg) as a sulfur source were dispersed in a mixture of oleylamine (OLA, dehydrated by vacuum drying at 100°C for 1 hour) (2.8 mL) and 1-dodecanethiol (DDT) (0.25 mL), and the mixture was heated at 300°C for 10 minutes under a nitrogen atmosphere. After cooling for 8 minutes, the supernatant solution obtained by centrifugation was collected and further passed through a membrane filter (pore size 0.20 μm) to remove aggregated particles. Methanol (3.0 mL) was added to this solution and centrifugation was performed to obtain a precipitate. Ethanol (3.0 mL) was added to the obtained precipitate to suspend it, and the precipitate was washed by centrifugation again. In this way, core AgInGaS quantum dots (average particle size: 4.3 nm) were obtained as a precipitate.

[0044] Next, the AgInGaS quantum dots described above were used as cores and shell coating was performed using the following method. The resulting AgInGaS quantum dots (1.0 × 10⁻¹⁶) -5 mmol (particles), as a metal source, Ga(acac)3 (59 mg), zinc stearate (Zn(C) 17 H 35(200 mg) of (COO)2 and 43 mg of thiourea as a sulfur source were dispersed in 3.0 mL of OLA and heated at 150 °C for 10 minutes under a nitrogen atmosphere, and then immediately heated at 250 °C for 30 minutes. After cooling for 45 minutes, the precipitate formed in the solution was recovered by centrifugation. Methanol (3.0 mL) was added to this precipitate to suspend it, and then the precipitate was washed by centrifugation.

[0045] The obtained precipitate contains the target quantum dots. In order to further increase the shell film thickness of each particle, the coating operation was performed again. The precipitate particles (1.0×10 -5 mmol (particles)) obtained in the first shell coating operation, together with Zn(C 17 H 35 100 mg of (COO)2 as a metal source and 12 mg of thiourea as a sulfur source were added to 3.0 mL of OLA and dispersed, and after heating at 150 °C for 10 minutes under a nitrogen atmosphere, immediately heated at 250 °C for 30 minutes. After cooling for 45 minutes, the precipitate formed in the solution was recovered by centrifugation. Methanol (3.0 mL) was added to this precipitate to suspend it, and then centrifuged to recover the precipitate. Ethanol (3.0 mL) was added to the obtained precipitate, suspended again, and then centrifuged to wash the precipitate. In this way, core-shell type quantum dot 1 (average particle size: 5.4 nm) with a core of AgInGaS and a shell of ZnGaS was obtained.

[0046] Next, the obtained quantum dot 1 was dissolved in 3.0 mL of chloroform to obtain a chloroform solution of quantum dot 1 whose surface was modified with OLA. Then, 0.10 mL of 3-mercaptopropionic acid (MPA), 0.73 mL of tetramethylammonium hydroxide, and 0.27 mL of ethanol were mixed into this solution (1.0 mL) and heated at 70 °C for 3 hours under a nitrogen atmosphere. As a result, the OLA on the surface of quantum dot 1 was replaced with MPA. Thus, quantum dot 1 whose surface was modified with MPA was obtained. Since MPA has a carboxyl group which is a hydrophilic group, by modifying the surface of quantum dot 1 with MPA, it became possible to dissolve quantum dot 1 in water.

[0047] Figure 3 shows TEM images of quantum dot 1. Figure 3(a) shows quantum dot 1 in chloroform solution (surface modified with OLA), and Figure 3(b) shows quantum dot 1 in aqueous solution (surface modified with MPA). As shown in Figure 3, it was found that quantum dot 1 with a particle size of 5.4 nm was obtained.

[0048] Figure 4 is a graph showing the results of measuring the fluorescence spectrum of quantum dot 1 (before it was covered with a shell). The excitation light was set to 365 nm. As shown in Figure 4, the fluorescence spectrum had two peaks, with a band-edge emission peak around 550 nm and a defect emission peak around 700 nm.

[0049] Figure 5 is a graph showing the spectrum of defect emission, comparing quantum dot 1 in chloroform solution and quantum dot 1 in aqueous solution. The excitation light was set to 365 nm. As shown in Figure 5, it was found that in the case of aqueous solution, the peak wavelength of defect emission shifts to longer wavelengths compared to the case of chloroform solution. From this, it was found that the calibration curve needs to be set according to the surrounding environment of quantum dot 1.

[0050] Figure 6 is a graph comparing the differences in the spectrum of defect emission from quantum dot 1 in an aqueous solution with respect to temperature. The excitation light was set to 365 nm. The temperature was varied in 10°C increments from 5°C to 45°C. The temperature was changed using a heater, and the temperature was measured by contacting a thermocouple with the aqueous solution. As shown in Figure 6, it was found that the light intensity of defect emission decreased as the temperature increased, and the peak wavelength shifted slightly to the shorter wavelength side.

[0051] Figure 7 shows the temperature dependence of the light intensity I1 at the peak wavelength of band-edge emission and the light intensity I2 at the peak wavelength of defect emission for quantum dot 1 in aqueous solution. It was found that both light intensities decreased linearly with temperature change, but there was a difference in the slope of the decrease.

[0052] Figure 8 is a graph showing the temperature dependence of the ratio I2 / I1, the ratio of light intensity I2 at the peak wavelength of defect emission to light intensity I1 at the peak wavelength of band-edge emission, for quantum dot 1 in aqueous solution. The excitation light wavelength and temperature measurement method are the same as in Figure 7. As shown in Figure 8, it was found that there is a one-to-one correspondence between the light intensity ratio I2 / I1 and temperature. Furthermore, it was found that this correspondence can be accurately approximated by a straight line. Therefore, it was found that by using the correspondence between the light intensity ratio I2 / I1 and temperature as a calibration curve, the temperature can be accurately measured from the light intensity ratio I2 / I1 in the range of at least 5 to 45°C. [Examples]

[0053] The quantum dot 1, whose surface was modified with MPA as prepared in Example 1, was dissolved in an aqueous solution. Octaarginine (R8) (2 mM) was mixed into the aqueous solution and allowed to stand at room temperature for 15 minutes. This prepared quantum dot 1 whose surface was modified with R8. R8 is a membrane-permeable peptide.

[0054] Next, quantum dots 1, whose surface was modified with R8, were dissolved, and the resulting aqueous solution was mixed with a culture medium of mouse adipose tissue-derived stem cells (ASCs) to allow the ASCs to incorporate the quantum dots 1. Then, the quantum dots 1 were irradiated with excitation light at a wavelength of 365 nm, and the fluorescence spectrum was measured. The fluorescence spectrum was measured multiple times by varying the temperature of the culture medium using a heater.

[0055] Figure 9 shows the temperature dependence of the ratio I2 / I1, the ratio of light intensity I1 at the peak wavelength of band-edge emission to light intensity I2 at the peak wavelength of defect emission, for quantum dot 1 within ASCs. As shown in Figure 9, it was found that there is a one-to-one correspondence between the light intensity ratio I2 / I1 and temperature. Furthermore, it was found that this correspondence can be accurately approximated by a straight line. Therefore, it was found that the temperature inside the cell can also be measured using quantum dot 1. [Examples]

[0056] Quantum dots 1, whose surfaces were modified with MPA according to Example 1, were dissolved in an aqueous solution. 50 μL of this aqueous solution was placed in a container and positioned on a heater, and fluorescence images of the container were acquired using a bioimaging device (PerkinElmer IVIS Lumina K Series III). The aqueous solution was heated by the heater, and fluorescence images were acquired at varying temperatures. The excitation light bandpass filter was set to 420-440 nm. The light intensity I1 at the peak wavelength of band-edge emission was measured from the fluorescence image of the container at wavelengths of 570-590 nm. The light intensity I2 at the peak wavelength of defect emission was acquired from the fluorescence image of the container at wavelengths of 690-710 nm.

[0057] Figure 10 is a graph showing the temperature dependence of the light intensity ratio I2 / I1. As shown in Figure 10, there is a one-to-one correspondence between the light intensity ratio I2 / I1 and temperature, and this correspondence can be accurately approximated by a straight line. Therefore, it was found that temperature measurement is possible using a bioimaging device. [Examples]

[0058] Quantum dots 1, whose surfaces were modified with MPA as prepared in Example 1, were dissolved in an aqueous solution, and 50 μL of this aqueous solution was subcutaneously injected into BALB / c nude mice. Then, as in Example 3, fluorescence images of the area of ​​the mouse where the aqueous solution was subcutaneously injected were acquired using a bioimaging device, and the light intensity ratio I2 / I1 was measured. The bandpass filter for the excitation light was set to 485-515 nm, and all other conditions were the same as in Example 3.

[0059] Figure 11 is a graph showing the temperature dependence of the light intensity ratio I2 / I1. As shown in Figure 11, there is a one-to-one correspondence between the light intensity ratio I2 / I1 and the temperature of the region in the mouse where the aqueous solution was subcutaneously injected, and this correspondence can be accurately approximated by a straight line. Therefore, it was found that it is possible to measure the temperature of specific parts of the living body using a bioimaging device. [Examples]

[0060] Quantum dots 1, whose surfaces were modified with MPA as prepared in Example 1, were dissolved in an aqueous solution, and 50 μL of this solution was subcutaneously injected into BALB / c nude mice. The mice were then subjected to three conditions: cooling, normal, and heating, and images were taken using an infrared thermography camera (FLIR C2, FLIR). As a result, the temperature of the area in the mice where the aqueous solution was subcutaneously injected was 21.3°C in the cooling state, 32.3°C in the normal state, and 36.7°C in the heating state.

[0061] Next, in the same manner as in Example 4, fluorescence images were acquired of the region in the mouse where the aqueous solution was subcutaneously injected using a bioimaging device. Fluorescence images were acquired for the mice in the three states described above: cooled, normal, and heated. The excitation light bandpass filter was set to 490-510 nm, and all other conditions were the same as in Example 4. The light intensity ratio I2 / I1 was then measured from the fluorescence images.

[0062] Next, the linear correspondence between the light intensity ratio I2 / I1 obtained in Example 4 and temperature (Figure 11) was used as a calibration curve, and the temperature was calculated from the light intensity ratio I2 / I1 in three states: cooled, normal, and heated. Figure 12 is a graph plotting the light intensity ratio I2 / I1 in the three states on the calibration curve. From Figure 12, the temperature of the area in the mouse where the aqueous solution was subcutaneously injected was calculated to be 22.0°C in the cooled state, 32.5°C in the normal state, and 37.4°C in the heated state. This result is in relatively good agreement with the measurement results from an infrared thermography camera, confirming that temperature can be measured using the correspondence between the light intensity ratio I2 / I1 and temperature as a calibration curve. [Industrial applicability]

[0063] The temperature measuring device disclosed herein is suitable for measuring the temperature of cells in living organisms. [Explanation of Symbols]

[0064] 1: Quantum dots 2: Light-irradiating section 3: Light detection unit 4: Light intensity ratio calculation section 5: Calibration curve memory unit 6: Temperature calculation part 10: Core 11: Shell

Claims

1. A core-shell type quantum dot is placed near the object to be measured and has a core with crystal defects and a shell covering the core, The quantum dot is irradiated with excitation light having a wavelength with an energy greater than the band gap energy of the core, and the light irradiation unit is provided for this purpose. A photodetector measures the light intensity at the peak wavelength of the band-edge emission of the quantum dot and the light intensity at the peak wavelength of the defect emission of the quantum dot. A light intensity ratio calculation unit calculates the light intensity ratio of two light intensities detected by the light detection unit, A calibration curve storage unit that stores a calibration curve showing the relationship between the light intensity ratio and the temperature around the quantum dot, A temperature calculation unit calculates the temperature of the object to be measured from the light intensity ratio calculated by the light intensity ratio calculation unit and the calibration curve stored in the calibration curve storage unit, A temperature measuring device characterized by having the following features.

2. The temperature measuring device according to claim 1, characterized in that the calibration curve is a straight line.

3. The temperature measuring device according to claim 1 or 2, characterized in that the calibration curve is set for each surrounding environment of the quantum dot.

4. The temperature measuring device according to any one of claims 1 to 3, characterized in that the temperature measuring device is for measuring temperature inside a living organism, the wavelength of the excitation light is 700 to 1500 nm, and hydrophilic groups are bonded to the surface of the quantum dot.

5. The temperature measuring device according to any one of claims 1 to 3, characterized in that the temperature measuring device is for measuring intracellular temperature, the wavelength of the excitation light is 700 to 1500 nm, and a membrane-permeable peptide or cationic liposome is bound to the surface of the quantum dot.

6. A core-shell type quantum dot having a core with crystal defects and a shell covering the core is placed near the object to be measured. The quantum dot is irradiated with excitation light, The light intensity at the peak wavelength of the band-edge emission of the quantum dot and the light intensity at the peak wavelength of the defect emission of the quantum dot are measured, and the ratio of these two light intensities is calculated. The temperature around the quantum dot is calculated from the aforementioned light intensity ratio and a calibration curve that shows the relationship between the aforementioned light intensity ratio and the temperature around the quantum dot, which has been determined in advance. A method for measuring temperature characterized by the following features.

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