Fluorescence recognition method of mangiferin on Zn and Cu

Abstract

The invention provides a fluorescence recognition method of mangiferin on Zn and Cu, and belongs to the technical field of fluorescence recognition, the method comprises the following steps: probe MF spectrum performance test, probe MF selective recognition experiment on metal ions, fluorescence titration experiment, interference experiment, and equal substance amount continuous change experiment. The invention discloses the excellent fluorescence characteristic of the mangiferin, the fluorescence intensity of the mangiferin (MF) can be obviously enhanced by adding Zn < 2 + > in a neutral aqueous solution, and the fluorescence of the MF is obviously weakened by adding Cu < 2 + >. The concentrations of the two metal ions and the fluorescence intensity of the system have a good linear relationship, and the detection limits of the two metal ions respectively reach 0.449 mu mol / L and 2.27 mu mol / L, which are lower than the detection limits reported in many literatures, so that the two metal ions are highly sensitive. An interference experiment result further shows that coexistence of other metal ions has no obvious interference on identification of Zn < 2 + > and Cu < 2 + > by MF.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescence recognition, and particularly to a fluorescence recognition method of mangiferin for Zn and Cu. Background Art

[0002] Metal ions play important roles in humans and ecosystems. For example, they play key roles in osmotic regulation, metabolic processes, regulation of bioenzyme activity, and biological signal transduction in organisms. Zinc and copper are both essential trace elements in the human body. Zinc ions participate in cell signal transduction, affect the synthesis and release of neurotransmitters, and play an important role in maintaining the normal functions of the nervous system. The lack of zinc element may cause symptoms such as listlessness in humans. The lack of zinc ions will lead to problems such as retarded growth and development and decreased immune function. In addition, long-term lack of zinc element is also correlated with the occurrence of early-onset Alzheimer's disease in the middle-aged and elderly population. Excessive zinc ions can cause poisoning, especially for newborns, which may cause abnormal brain development and spinal fissures.

[0003] Copper is the third most abundant transition metal in the human body. Cu 2+ affects the formation of red blood cells in the human body, and various physiological processes such as the normal growth and maintenance of various organs in the human body also require the influence of Cu 2+ . However, the content of Cu 2+ in the human body should also have a limit. Excessive or too low content of Cu 2+ will cause intracellular homeostasis disorders and damage the central nervous system. Diseases such as Alzheimer's disease, Parkinson's disease, Menkes disease, and Wilson's disease are all caused by the abnormal accumulation of Cu 2+ . Gastrointestinal diseases and abnormal bone growth are due to the lack of Cu 2+ in the human body. The development of industry has led to serious pollution of the ecological environment, and Cu 2+ has also polluted the environment. When the soil or surface water is polluted by Cu 2+ , excessive copper will be enriched in plants and fish and enter the human body through the food chain directly or indirectly, affecting human health. According to the relevant regulations of the US Environmental Protection Agency (EPA), the safety threshold limit of copper ions in drinking water is set at 1.3 ppm (20 μM).

[0004] Zinc and copper metals are important chemical raw materials and are widely used in industrial fields such as electroplating, coating, batteries, medicine, and alloy materials, bringing serious pollution problems to the environment. Therefore, accurate and highly selective qualitative and quantitative analysis of Cu 2+ , Zn 2+ is of crucial significance in environmental monitoring and human health maintenance.

[0005] In the detection of Zn 2+and Cu 2+ In the fluorescence analysis of, the organic small molecule probe shows good sensitivity. Deng Jia et al. obtained a new fluorescent probe molecule through a one-step reaction using salicylic acid and salicylamide as raw materials. The binding ratio between this probe and Zn 2+ is 2:1, and the detection limit of Zn 2+ is 3.2×10 -6 mol / L. Zhan Junyan et al. coupled the fluorescent group 8-hydroxyquinoline to the estradiol structure to prepare an estradiol molecular probe conjugated with quinoline, and achieved a highly selective response to Zn 2+ through a fluorescence enhancement mechanism. The detection limit for the recognition of Zn 2+ is 2.18×10 -6 mol / L. In the detection of Cu 2+ , Ren Zehua et al. synthesized a B-Ce-GMP fluorescent probe by self-assembly using rhodamine B, Ce(NO3)3·6H2O and GMP reagents. This fluorescent probe has good selectivity and anti-interference ability, and the lowest detection limit for copper ions in HEPES buffer is 2.74 μmol·L -1 . Chen Shuoran et al. used palladium octaethylporphyrin (PdOEP) as a photosensitizer and b-HTPA as a quencher to test and study the sensitivity and detection limit of the b-HTPA / PdOEP / Cu 2+ system using upconversion fluorescence spectroscopy. The results show that the upconversion fluorescence intensity of this probe decreases with the increase of the Cu 2+ concentration, and it has good responsiveness. Through fitting calculation, the detection limit of b-HTPA for Cu 2+ is 3.78×10 -6 mol·L -1 .

[0006] Mangiferin (MF), a diphenylpyrrolidone flavonoid, is mainly derived from the leaves, fruits and barks of plants such as Mangifera indica and Amygdalus communis in the Anacardiaceae family, and can also be isolated from the leaves of Anemarrhena asphodeloides in the Liliaceae family and plants such as Gentiana scabra and Swertia mussotii in the Gentianaceae family. MF has certain medicinal values. It has certain medicinal value for the human brain nerves, has a central nervous inhibitory effect, and also has a certain effect on the human respiratory system and can be used to treat chronic bronchitis. MF can also reduce radiation, resist diabetes, anti-inflammatory, antiviral, anti-hepatotoxic, treat hepatitis, promote bile secretion, reduce fever, and has an immunosuppressive effect. At the same time, MF also has obvious toxic effects on liver cancer cell lines and can induce apoptosis of liver cancer cells; it has antioxidant activity and anti-aging effects. Mango Cough Capsules, Mangiferin Tablets, and Mangiferin Pills can all be used to treat respiratory diseases. According to the literature research, scholars have focused on the biological activity research of mangiferin and paid less attention to other properties of mangiferin. Therefore, it is necessary to design a fluorescence recognition method for mangiferin to Zn and Cu. Summary of the Invention

[0007] The purpose of the present invention is to provide a fluorescence recognition method for mangiferin to Zn and Cu, so as to solve the technical problem that existing mangiferin has not been used for the fluorescence recognition of Zn and Cu.

[0008] Mangiferin (MF) exhibits good fluorescence properties. In neutral aqueous solution, the probe MF can specifically recognize Zn through fluorescence enhancement 2+ , and recognize Cu through fluorescence quenching 2+ , and is a good probe for detecting and recognizing Zn 2+ and Cu 2+ .

[0009] The active ingredient of xanthone in mango leaves - mangiferin (MF) has good fluorescence properties. MF shows an obvious fluorescence enhancement specific selective response to Zn in a neutral solution system, and the concentration of Zn 2+ has a good linear relationship with the fluorescence value of MF, and its detection limit is 0.494 μmol / L; under the same conditions, MF shows a significant fluorescence quenching selective response to Cu 2+ , and Cu 2+ also has a linear relationship with the fluorescence value of MF in the range of 0 - 16 μmol / L, and the detection limit is 2.27 μmol / L. In comparison, MF shows a lower detection limit for the detection of Zn 2+ and Cu 2+ . The equimolar continuous variation method experiment shows that MF combines with Zn 2+ and Cu 2+ to form a new compound with a stoichiometric ratio of 1:1, causing changes in the fluorescence of MF. It can be seen that the MF fluorescence probe has a good linear relationship with Zn 2+ in the range of 0 - 16 μmol / L, and the detection limit is 2.27 μmol / L. In comparison, MF shows a lower detection limit for the detection of Zn 2+and Cu 2+ It has potential application value in detection.

[0010] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0011] A fluorescence recognition method of mangiferin for Zn and Cu, the method comprising the following steps:

[0012] Step 1: Probe MF spectral performance test;

[0013] Step 2: Probe MF selective recognition experiment for metal ions;

[0014] Step 3: Perform fluorescence titration experiment;

[0015] Step 4: Perform interference experiment;

[0016] Step 5: Perform equimolar continuous variation experiment;

[0017] Further, the specific process of Step 1 is as follows:

[0018] Weigh the probe MF, dissolve it with DMSO-water, and prepare a stock solution with a concentration of 2×10 -3 mol / L for standby. Adjust the pH of the solution system with hydrochloric acid and sodium hydroxide, and detect the fluorescence intensity of the probe MF in solutions with different pH values.

[0019] Further, the V DMSO :V H2O in DMSO-water is 2:8. The conditions for testing the probe MF are that the fluorescence excitation wavelength is set at 389 nm, the excitation and emission slits are set at 10 nm, the voltage is set at 580 V, the fluorescence spectrum scanning range is 400 nm to 650 nm, and the wavelength scanning range of the ultraviolet spectrum is 210 to 600 nm.

[0020] Further, the specific process of Step 2 is as follows: Select nitrates or hydrochlorides of metal ions such as K + , Na + , Mg 2+ , Ca 2+ , Ba 2+ , Co 2+ , Ni 2+ , Zn 2+ , Mn 2+ , Cu 2+ , Cr 3+ , Hg + , Ag + , and prepare a stock solution with a concentration of 1.0×10 -2 mol / L for standby;

[0021] Take 100 μL of the MF mother liquor and add it to a fluorescence cuvette. Then add 2900 μL of ultrapure water, and further add 10 μL of the stock solution of all metal ions with a concentration of 10 μL. Among them, the volume of Zn 2+ is 5 μL. After reacting for 5 min, measure the change in the fluorescence spectrum. In the solution system, the concentrations of the probe MF and each metal ion are: 6.67×10 -5 mol / L and 3.33×10 -5 mol / L, and the probe MF is twice the amount of the metal ion.

[0022] Furthermore, the specific process of step 3 is as follows: According to the experimental results of the recognition of metal ions by the probe MF, select Zn 2+ and Cu 2+ to further carry out a fluorescence titration experiment. Add an appropriate amount of the MF mother liquor to a 10 mm cuvette, add ultrapure water to make up 3000 μL of the test solution. Using the titration method, gradually increase the concentrations of Zn 2+ and Cu 2+ ions respectively. For the binding of MF and Zn 2+ , after 6 minutes, measure the change in the fluorescence spectrum of the reaction system again.

[0023] Furthermore, the specific process of step 4 is as follows: Detect the interference effect of the presence of other metal ions on the detection when the probe MF recognizes Zn 2+ and Cu 2+ . In a 10 mm fluorescence cuvette, add 3000 μL of the probe MF test solution, first measure its fluorescence intensity, and then successively add 10 μL of the solution of other metal ions with a concentration of 1.0×10 -2 mol / L. React for 5 min and measure the fluorescence of the system. Then add 5 μL of the solution of Zn -2 or Cu 2+ with a concentration of 1.0×10 2+ mol / L. For the binding of MF and Cu 2+ , react for 5 min and measure the fluorescence spectrum of the system. For the binding of MF and Zn 2+ , after 6 minutes, measure the fluorescence spectrum of the system, and investigate the interference of other ions on the recognition of Zn 2+ and Cu 2+ .

[0024] Furthermore, in step 5: Keep the volume of the solution system in the fluorescence cuvette at 3.0 mL, and set the total concentration of the mixed system of MF and Zn 2+ or Cu 2 + constant. By continuously adjusting the ratio X = [M n+ / ([M n++[MF]), with an excitation wavelength of 389 nm, both slits being 10 nm, and a voltage of 580 V, measure the fluorescence intensities at different ratios, and based on the concentration ratio of the added substance corresponding to the maximum fluorescence intensity, infer the coordination ratio between the ligand and the ion to be measured.

[0025] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0026] The present invention reveals the excellent fluorescence properties of mangiferin. In a neutral aqueous solution, adding Zn 2+ can significantly enhance the fluorescence intensity of mangiferin (MF), while the addition of Cu 2+ results in an obvious decrease in the fluorescence of MF. A good linear relationship is presented between the concentrations of the two metal ions and the fluorescence intensity of the system, and their detection limits reach 0.449 μmol / L and 2.27 μmol / L respectively, which are lower than those reported in many literatures, indicating a high sensitivity to these two metal ions. The results of the interference experiment further show that the coexistence of other metal ions has no significant interference on the recognition of Zn 2+ and Cu 2+ by MF. The MF fluorescence probe shows potential application prospects in the detection of Zn 2+ and Cu 2+ , provides new ideas and methods for the detection research in related fields, and also opens up a new path for the comprehensive utilization of mango resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the fluorescence intensity diagram of MF of the present invention in solutions with different pH values;

[0028] Figure 2 is the influence diagram of different metal ions on the fluorescence spectrum of MF of the present invention;

[0029] Figure 3 is the time response measurement diagram of MF of the present invention to Zn 2+ and Cu 2+ ;

[0030] Figure 4 is the influence diagram of different Zn 2+ concentrations on the fluorescence spectrum of MF of the present invention;

[0031] Figure 5 is the influence diagram of different Cu 2+ concentrations on the fluorescence spectrum of MF of the present invention;

[0032] Figure 6 is the interference diagram of other ions on the MF-Zn system (a) and the MF-Cu system (b) of the present invention;

[0033] Figure 7It is the method for measuring MF-Zn by the equimolar continuous variation method of the present invention 2+ (a) and MF-Cu 2+ (b) combination ratio diagram. Specific embodiments

[0034] To make the objectives, technical solutions and advantages of the present invention clearer, the following provides preferred embodiments with reference to the attached drawings for further detailed description of the present invention. However, it should be noted that many details listed in the specification are only for readers to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0035] 1.1 Instruments and reagents

[0036] F-7000 fluorescence spectrophotometer (Hitachi, Japan); UV-2700 ultraviolet-visible spectrophotometer (Shimadzu, Japan).

[0037] Mangiferin (abbreviated as MF), >98%, purchased from Shanghai Aladdin. All metal salts used are of analytical grade. The reagents were not further purified and were used directly.

[0038] 1.2 Test on the spectral properties of the probe MF

[0039] Accurately weigh 0.0564 g of the probe MF, dissolve it with DMSO-water (V DMSO / V H2O = 2:8) to prepare a stock solution with a concentration of 2×10 - 3 mol / L for standby. Adjust the pH of the solution system with hydrochloric acid and sodium hydroxide, and detect the fluorescence intensity of the probe MF in solutions with different pH values.

[0040] Test conditions: The fluorescence excitation wavelength is set to 389 nm, the excitation and emission slits are set to 10 nm, the voltage is set to 580 V, and the fluorescence spectrum scanning range is 400 nm - 650 nm; the wavelength scanning range of the ultraviolet spectrum is 210 - 600 nm.

[0041] 1.3 Experiment on the selective recognition of metal ions by the probe MF

[0042] Select (K + , Na + , Mg 2+ , Ca 2+ , Ba 2+ , Co 2+ , Ni 2+ , Zn 2+ , Mn 2+ , Cu 2+ , Cr 3+ , Hg + , Ag+ ) Nitrates or hydrochlorides of metal ions such as are prepared into a 1.0×10 -2 mol / L stock solution with deionized water for standby.

[0043] Take 100 μL of the MF mother liquor (2×10 -3 mol / L) and add it to a fluorescence cuvette. Then add 2900 μL of ultrapure water, and then add 10 μL of various metal ion stock solutions with a concentration of 10 μL each (Zn 2+ is 5 μL). After reacting for 5 min, measure the change in its fluorescence spectrum. In the solution system, the concentrations of the probe MF and each metal ion are: 6.67×10 -5 mol / L and 3.33×10 -5 mol / L, and the probe MF is 2 times the equivalent of the metal ion.

[0044] 1.4 Fluorescence titration experiment

[0045] According to the experimental results of the recognition of metal ions by the probe MF, select Zn 2+ and Cu 2+ to further carry out the fluorescence titration experiment. Add an appropriate amount of the MF mother liquor to a 10 mm cuvette, add ultrapure water to make up 3000 μL of the test solution. Using the titration method, gradually increase the concentrations of Zn 2+ and Cu 2+ ions respectively. For the binding of MF and Zn 2+ , after about 6 minutes, measure the change in the fluorescence spectrum of the reaction system.

[0046] 1.5 Interference experiment

[0047] Detect the interference effect of other metal ions on the detection when the probe MF recognizes Zn 2+ and Cu 2+ . In a 10 mm fluorescence cuvette, add 3000 μL of the probe MF test solution. First measure its fluorescence intensity, and then sequentially add 10 μL of other metal ion solutions with a concentration of 1.0×10 -2 mol / L respectively. React for 5 min and measure the fluorescence of the system; then add 5 μL of Zn - 2 or Cu 2+ solution with a concentration of 1.0×10 2+ mol / L. For the binding of MF and Cu 2+ , react for 5 min and measure the fluorescence spectrum of the system. For the binding of MF and Zn 2+ , after about 6 minutes, measure the fluorescence spectrum of the system to investigate the interference of other ions on the recognition of Zn 2+ and Cu 2+ .

[0048] 1.6 Job Curve Experiment

[0049] In the equimolar continuous variation experiment (Job curve experiment), the volume of the solution system in the fluorescence cuvette was kept at 3.0 mL. The total concentration of the mixed system of MF and Zn 2+ or Cu 2+ was kept constant. By continuously adjusting the ratio X = [M n+ / ([M n+ +[MF]) of the added MF and the analyte ion, with an excitation wavelength of 389 nm, slit widths of 10 nm, and a voltage of 580 V, the fluorescence intensities at different ratios were measured. According to the concentration ratio of the added substances corresponding to the maximum fluorescence intensity, the coordination ratio between the ligand and the analyte ion was deduced.

[0050] 2 Results and Discussion

[0051] 2.1 Spectral Properties of the Probe MF

[0052] Figure 1 are the UV absorption spectrum and fluorescence spectrum of MF. As shown in Figure 1 (a), MF has a strong absorption peak at approximately 389 nm, which can be attributed to the characteristic absorption peak of band I of flavonoid compounds. The strong absorption peak at 240 nm can be attributed to the characteristic absorption peak of band II of flavonoid compounds. Both are absorptions caused by the π→π* electronic transition of the flavonoid parent ring.

[0053] As shown in Figure 1 (b), when the fluorescence excitation wavelength of MF, λ ex = 389 nm and the emission wavelength, λ em = 537 nm, there is a large Stokes shift (Δλ = 1148 nm), which helps to reduce the interference of excitation luminescence on emission luminescence, and thus improves the fluorescence recognition performance of MF, providing a feasible reference for further studying the recognition of MF for metal ions.

[0054] Figure 1 (c) shows the change in the fluorescence intensity of the fluorescent probe MF at different pH values. The fluorescence intensity of MF is affected by pH. It is below 100 in an acidic environment (pH < 5), while it is stable at 1600 - 1700 at pH 6 - 7. When the pH value increases to 8 or above, the fluorescence intensity increases significantly, reaching 2236 at pH 8 and as high as 5786 at pH 11. This may be because the hydroxyl groups in the MF molecule are deprotonated under alkaline conditions, changing the electron cloud distribution. Considering that metal ions may form hydroxide precipitates under high pH conditions, to ensure the consistency of experimental conditions and the reliability of results, subsequent experiments were carried out in neutral solutions.

[0055] 2.2 Recognition and Selection of the Probe MF for Various Metal Ions

[0056] This study aims to explore the selective recognition ability of metallofluorescein (MF) for various metal ions. In the experiment, 3 mL of MF test solution was taken, and 20 μL of different metal ion solutions (the metal ion concentration in the system must be greater than 66.7 μmol / L here) were added to it, including Co 2+ 、Na + 、K + 、Ni 2+ 、Ca 2+ 、Ba 2+ 、Cu 2+ 、Cr 3+ 、Ag + 、Mg 2+ 、Mn 2+ ), and fluorescence spectral analysis was carried out. The results are as Figure 2 shown. The introduction of ions such as K + 、Na + 、Mg 2+ 、Ca 2+ 、Ba 2+ 、Co 2+ 、Ni 2+ 、Mn 2+ 、Ag + only caused a slight change in the fluorescence intensity of MF, indicating that these ions had no significant effect on the fluorescence of MF. However, the addition of Zn 2+ significantly increased the fluorescence intensity of MF, and its fluorescence value jumped from I = 2127 to 8244, with a fluorescence enhancement amplitude of 288%; while the introduction of Cu 2+ and Cr 3+ led to a significant quenching phenomenon of MF fluorescence, and the fluorescence values decreased to 146.6 and 472.8 respectively, a decrease of 93.1% and 77.7% respectively. This indicates that MF has good recognition ability for Zn 2+ 、Cu 2+ 、Cr 3+ , especially the enhancement effect of Zn 2+ on the fluorescence of MF is particularly significant. In the experiment, the metal salts selected included ZnCl2, CuCl2, NaCl, Cr(NO3)3, AgNO3, so the interference of Cl- and NO3- ions can be excluded.

[0057] 2.3 Time response determination of MF for Zn 2+ and Cu 2+

[0058] For ion probes, the response time is a particularly crucial step in the detection method. We added the same concentration of Zn 2+ and Cu 2+ to the pure aqueous solution system of MF respectively., the change in the fluorescence intensity of the system within 0 - 10 minutes was measured, as Figure 3 . It can be seen that the binding of MF and Zn 2+ , after about 6 minutes, the reaction reached equilibrium, and the fluorescence intensity of the system hardly changed anymore; while the binding of MF and Cu 2+ was very fast. After mixing the two, the fluorescence of the system reached equilibrium within a very short time, and the fluorescence intensity hardly changed anymore. The reaction time of the subsequent fluorescence experiments was based on this experiment.

[0059] 2.4 Fluorescence titration of MF with Zn 2+ and Cu 2+ and calculation of the detection limit

[0060] To further study the influence of different concentrations of Zn 2+ and Cu 2+ on the fluorescence of the probe MF, fluorescence titration experiments were carried out, and the results are shown in Figure 4 and Figure 5 .

[0061] As can be seen from Figure 4 (a), when Zn 2+ was gradually added dropwise to the probe MF solution, the fluorescence intensity of the system MF - Zn 2+ also gradually increased. When the concentration of Zn 2+ was in the range of 0 - 66.7 μmol / L, there was a good linear relationship between the fluorescence enhancement of MF. The linear regression equation obtained by fitting was: y = 1370.3 + 555.0x, R 2 = 0.98979; the detection limit LOD was calculated according to the formula LOD = 3σ / k [17-18] , where σ represents the standard deviation of the fluorescence values of the probe MF samples for ten times, and k represents the slope of the linear curve of the fluorescence intensity versus the concentration of Zn 2+ . The detection limit of the recognition method of the probe MF for Zn 2+ was calculated to be 0.494 μmol / L. Compared with the literature listed in Table 1, the probe MF can detect Zn 2+ well, and its detection limit is much lower. This indicates that the probe MF has high sensitivity for the detection of Zn 2+ .

[0062] Figure 5 is the fluorescence spectrogram of a 66.67 μmol / L aqueous solution of the probe MF with the increase of the concentration of Cu 2+ (0 - 32 μmol / L). With the increase of the concentration of Cu 2+ , the fluorescence intensity of MF at 537 nm gradually decreased. When the concentration reached 26.67 μmol / L, the decreasing trend of the fluorescence intensity slowed down. As can be seen from the inset of Figure b, the fluorescence intensity of MF and Cu2+ It shows a good linear relationship within the concentration range of 0 - 16 μmol / L. By performing linear fitting on the fluorescence intensity and concentration, the regression equation is: y = 2545.87 - 120.95x, R 2 = 0.98372. Calculated according to the detection limit formula LOD = 3σ / k, the results show that the MF recognition and detection of Cu 2+ has a detection limit of 2.27 μmol / L. Compared with the literature listed in Table 1, the probe MF also has good performance in the detection of Cu 2+ . It can be seen that MF has the potential for quantitative detection of Cu 2+ , and the detection method has high sensitivity.

[0063] According to the data in Table 1, the fluorescence probe reported in this paper shows lower detection limits (LOD) in the detection of Zn 2+ and Cu 2+ compared with the results reported in the literature. The detection limit of MF for Zn 2+ (0.494 μM) is significantly lower than most of the results reported in the literature, and the detection limit of this paper is also slightly lower, indicating that the MF probe has higher sensitivity in the detection of zinc ions. In terms of copper ion detection, the detection results of MF for Cu 2+ are within the same order of magnitude as the existing reports, but the detection limit of MF is slightly lower, showing higher sensitivity.

[0064] Table 1 Comparison of Zn 2+ / Cu 2+ Detection Probes

[0065]

[0066]

[0067] 2.5 Interference Experiments of Common Ions

[0068] To test the practical application ability of the probe MF in the detection of Zn 2+ and Cu 2+ , the interference of common ions (Co 2+ , Na + , K + , Ni 2+ , Ca 2+ , Ba 2+ , Ag + , Cd 2+ , Mg 2+ , Mn 2+ ) on the detection of Zn 2+ and Cu 2+ by MF was studied. As Figure 6As shown, after adding other ions to the probe MF in a pure aqueous solution system, the fluorescence intensity of the system did not change significantly. Subsequently, an equivalent amount of Zn was added to each detection 2+ , and the fluorescence of the system increased significantly; an equivalent amount of Cu was added to each detection system 2+ , and the fluorescence of the system decreased rapidly. The research results show that the fluorescence detection of MF for Zn 2+ and Cu 2+ is not affected by common metal ions. It can be seen that when the above tested ions coexist with Zn 2+ , Cu 2+ in MF, Zn 2+ , Cu 2+ have an advantage over most other competing ions in binding to the probe MF.

[0069] However, since Zn 2+ enhances the fluorescence of the MF probe, while Cu 2+ and Cr 3+ can cause quenching of the fluorescence intensity of the MF probe, when detecting Zn by MF 2+ , the coexistence of Cu 2+ and Cr 3+ must be avoided, and measures to shield or remove these two ions are necessary if necessary. Correspondingly, during the detection of Cr by MF 3+ , the interference of Zn 2+ and Cu 2+ needs to be shielded.

[0070] 2.6 Binding study of MF with Zn 2+ , Cu 2+

[0071] The Job's Plot experiment (method of continuous variation of equal amounts of substances) was used to explore the stoichiometric binding ratio of MF with Zn 2+ and Cu 2+ . First, keep the total concentration of MF and Zn 2+ (or Cu 2+ ) at 66 μmol, and by continuously adjusting the concentration ratio of [M n+ / ([M n+ +[MF]), measure the fluorescence intensity of the system at the maximum emission wavelength at different concentration ratios, and draw a Job’plot curve. The fluorescence intensity at the maximum fluorescence absorption of the system changes with the proportion of Zn 2+ and Cu 2+ as Figure 7 shown. The inflection point of the fluorescence value in the figure appears at the mole fraction of Zn 2+ and Cu 2+ approximately at 0.5, indicating that MF binds to Zn 2+ and Cu2+ The binding ratio is 1:1.

[0072] Mangiferin not only exhibits a wide range of pharmacological activities, but this study also unexpectedly reveals its excellent fluorescence properties. In neutral aqueous solution, the addition of Zn 2+ can significantly enhance the fluorescence intensity of mangiferin (MF), while the addition of Cu 2+ results in an obvious decrease in the fluorescence of MF. A good linear relationship is presented between the concentrations of the two metal ions and the fluorescence intensity of the system, and their detection limits reach 0.449 μmol / L and 2.27 μmol / L respectively, which are lower than those reported in many literatures, indicating a high sensitivity to these two metal ions. The results of the interference experiment further show that the coexistence of other metal ions has no significant interference on the recognition of Zn 2+ and Cu 2+ . Based on the above research results, the MF fluorescent probe shows potential application prospects in the detection of Zn 2+ and Cu 2+ , providing new ideas and methods for the detection research in related fields, and also opening up a new path for the comprehensive utilization of mango resources.

[0073] Matters not covered by this invention are well-known technologies.

[0074] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. Fluorescent recognition method of mangiferin for Zn and Cu, characterized in that: The method includes the following steps: Step 1: Testing the spectral performance of the probe MF; Step 2: Experiment on the selective recognition of metal ions by the probe MF; Step 3: Conducting a fluorescence titration experiment; Step 4: Conducting an interference experiment; Step 5: Conducting an equimolar continuous variation experiment.

2. The fluorescence recognition method of mangiferin for Zn and Cu according to claim 1, characterized in that: The specific process of Step 1 is as follows: Weigh the probe MF, dissolve it with DMSO-water, and prepare a stock solution with a concentration of 2×10 -3 mol / L for standby. Adjust the pH of the solution system with hydrochloric acid and sodium hydroxide, and detect the fluorescence intensity of the probe MF in solutions with different pH values.

3. The fluorescence recognition method of mangiferin for Zn and Cu according to claim 2, characterized in that: V in DMSO-water DMSO : V H2O is 2:

8. The conditions for testing the detection probe MF are that the fluorescence excitation wavelength is set to 389 nm, the excitation and emission slits are set to 10 nm, the voltage is set to 580 V, the fluorescence spectrum scanning range is 400 nm to 650 nm, and the wavelength scanning range of the ultraviolet spectrum is 210 to 600 nm.

4. The fluorescence recognition method of mangiferin for Zn and Cu according to claim 1, characterized in that: The specific process of Step 2 is as follows: Select K + , Na + , Mg 2+ , Ca 2+ , Ba 2+ , Co 2+ , Ni 2+ , Zn 2+ , Mn 2+ , Cu 2+ , Cr 3+ , Hg + , Ag + nitrate or hydrochloride of metal ions, and prepare a stock solution of 1.0×10 -2 mol / L with deionized water for standby; Take 100 μL of the MF stock solution and add it to a fluorescence cuvette. Then add 2900 μL of ultrapure water. Next, add 10 μL of the stock solution of all metal ions with a concentration of 1.0×10 -2 mol / L, where Zn 2+ is 5 μL. After reacting for 5 min, measure the change in the fluorescence spectrum. In the solution system, the concentrations of the probe MF and each metal ion are: 6.67×10 -5 mol / L and 3.33×10 -5 mol / L, and the probe MF is twice the amount of the metal ion.

5. The fluorescence recognition method of mangiferin for Zn and Cu according to claim 1, characterized in that: The specific process of Step 3 is as follows: Based on the experimental results of the recognition of metal ions by the probe MF, Zn 2+ and Cu 2+ were further used to conduct fluorescence titration experiments. An appropriate amount of MF stock solution was added to a 10 mm cuvette, and ultrapure water was added to make up 3000 μL of the test solution. By titration method, the concentrations of Zn 2+ and Cu 2+ ions were gradually increased respectively. For the binding of MF to Zn 2+ , after 6 minutes, the fluorescence spectrum change of the reaction system was measured again.

6. The fluorescence recognition method of mangiferin for Zn and Cu according to claim 1, characterized in that: The specific process of Step 4 is as follows: Detect the interference of the presence of other metal ions on the detection when the probe MF recognizes Zn 2+ and Cu 2+ . In a 10 mm fluorescence cuvette, add 3000 μL of the probe MF test solution, first measure its fluorescence intensity, and then successively add 10 μL of other metal ion solutions with a concentration of 1.0×10 -2 mol / L, react for 5 min, measure the fluorescence of the system, then add 5 μL of a Zn -2 or Cu 2+ solution with a concentration of 1.0×10 2+ mol / L. For the binding of MF to Cu 2+ , react for 5 min and measure the fluorescence spectrum of the system. For the binding of MF to Zn 2+ , measure the fluorescence spectrum of the system after 6 minutes, and investigate the interference of other ions on the recognition of Zn 2+ and Cu 2+ .

7. The fluorescence recognition method of mangiferin for Zn and Cu according to claim 1, characterized in that: In step 5: Keep the volume of the solution system in the fluorescence cuvette at 3.0 mL, and set the total concentration of the mixed system of MF and Zn 2+ or Cu 2+ constant. By continuously adjusting the ratio X = [M n+ / ([M n+ +[MF]) of the added MF and the ion to be measured, using 389 nm as the excitation wavelength, both slits being 10 nm, and the voltage being 580 V, measure the fluorescence intensities at different ratios, and infer the coordination ratio of the ligand to the ion to be measured according to the concentration ratio of the added substances corresponding to the maximum fluorescence intensity.

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