Microneedle type all-solid-state magnesium ion selective sensor as well as preparation method and application thereof

Abstract

The invention discloses a microneedle type all-solid-state magnesium ion selective sensor as well as a preparation method and application thereof. The all-solid-state magnesium ion selective sensor comprises a micro-needle and a polyimide tube arranged outside the micro-needle in a sleeving mode, and the tip end of the micro-needle extends out of the polyimide tube by 1-2 mm; a graphene water-based coating layer, a poly (3, 4-ethylenedioxythiophene) / poly (4-styrenesulfonic acid) sodium salt) layer and a Mg < 2 + > sensitive film are sequentially coated at the tip end of the micro needle. The magnesium ion selective sensor disclosed by the invention converts a Mg < 2 + > concentration signal into a potential signal based on a double electric layer theory, has the advantages of high response speed, low detection threshold, stable potential response, long service life, low manufacturing cost, large-scale production potential and the like, and has wide market application potential.

Description

Technical Field

[0001] The invention relates to a microneedle type all-solid-state magnesium ion selective sensor and a preparation method and application thereof, belonging to the field of electrochemical sensors. Background Art

[0002] Magnesium is a key element for crop photosynthesis and an important nutrient element required for protein synthesis and carbohydrate metabolism. Magnesium deficiency will seriously affect the growth and development of crops. Crops absorb magnesium in the form of ions from the roots and transport it to various tissues and organs of the crop through the xylem.

[0003] Early methods for detecting ions in crops include ion chromatography, titration, colorimetry, etc. These methods are not only complicated in operation steps but also cannot achieve in vivo measurement. With the development of detection technology, many methods for monitoring ions in crops in vivo have emerged, such as fluorescence spectroscopy, isotope labeling, glass microelectrode method, organic electrochemical transistor method, etc. Although these methods can be used for in vivo ion detection of crops, they have problems such as complex experimental steps, expensive experimental equipment, short sensor life, easy damage or low detection limit, and even possible significant damage to crops.

[0004] All-solid-state ion-selective electrodes have developed rapidly in recent years and have been widely used in biomedicine, agriculture, environment and industrial analysis. Due to their advantages of portability, fast response, low cost, easy miniaturization, simple production and in vivo measurement, their application in in vivo crop detection has great development potential. 2+ There are few studies on selective sensors, and there is no microneedle-type Mg 2+ A method is reported for directly penetrating selective sensors into the interior of crop stems to achieve in situ detection of living organisms. Summary of the invention

[0005] The purpose of the present invention is to provide a micro-needle all-solid Mg 2+ Selective sensor, which is a potentiometric sensor with fast response, stability, small structure and low detection limit (up to 1.0×10 -7 M), can be used for crop stems Mg 2+ In situ live detection.

[0006] The microneedle all-solid-state magnesium ion selective sensor provided by the present invention comprises a microneedle and a polyimide tube sleeved outside the microneedle, wherein the tip of the microneedle extends 1-2 mm outside the polyimide tube; The tip of the microneedle is coated with a graphene water-based coating layer, a poly(3,4-ethylenedioxythiophene) / poly(sodium 4-styrenesulfonate) layer and a Mg 2+ Sensitive membrane; Among them, the CAS number of 3,4-ethylenedioxythiophene is 126213-50-1; the CAS number of (4-styrenesulfonic acid) sodium salt is 2695-37-6.

[0007] Preferably, the microneedle is a stainless steel silver-plated acupuncture needle, a stainless steel gold-plated acupuncture needle or a stainless steel acupuncture needle; The polyimide tube has a diameter of 0.2-0.3mm and a thickness of 0.02-0.04mm; The assembly process of the micro needle and the polyimide tube is as follows: The microneedle is cleaned in anhydrous ethanol using an ultrasonic cleaner; then the polyimide tube is sleeved on the tip of the microneedle so that the tip is exposed about 1-2 mm from the polyimide tube; the tube opening of the polyimide tube close to the tip of the microneedle is sealed by an oily original rubber; The length of the polyimide tube may be 0.8-1.3 cm.

[0008] In the microneedle-type all-solid-state magnesium ion selective sensor of the present invention, the Mg 2+ The sensitive film is made of Mg 2+ The sensitive membrane solution contains ion exchanger, Mg 2+ Ionophores, plasticizers and polymer matrix materials.

[0009] Wherein, the ion exchanger is one or more of sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate, tetrakis(dodecyl)-tetrakis(4-chlorophenyl)ammonium borate, potassium tetraphenylborate and potassium tetrakis(4-chlorophenyl)borate; The Mg 2+ Ion carrier is Mg 2+ Ionophore II and Mg 2+ One of the ionophores IV; Among them, the Mg 2+ The CAS number of ionophore II is 119110-37-1, and its alias is ETH5214 or (N,N''-octylenebis(N'-heptyl-N'-methyl-methylmalonamide)); The Mg 2+The CAS number of ionophore IV is 135734-39-3, and its aliases are ETH7025 or N,N',N''-tris[3-(heptylmethylamino)-3-oxopropionyl]-8,8'-iminodioctylamine or N-heptyl-N',N'-di[8-({3-[heptyl(methyl)amino]-3-oxopropionyl}amino)octyl]-N-methylmalonamide; The plasticizer is one of o-nitrophenyl octyl ether, dioctyl phthalate, dibutyl phthalate, tricresyl phosphate or bis(2-ethylhexyl) sebacate; The polymer matrix material is polyvinyl chloride; The ion exchanger, the Mg 2+ The mass ratio of the ion carrier, the plasticizer and the polymer matrix material is 1.0-1.5: 0.8-1.2: 64.5-65: 32-32.5.

[0010] The present invention also provides a method for preparing the magnesium ion selective sensor, comprising the following steps: S1, applying graphene water-based coating to the tip of the microneedle to obtain the graphene water-based coating layer; the coating method can be dip coating, drip coating or automatic or semi-automatic coating device; S2. Using a three-electrode system, electroplating (3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) on the surface of the graphene water-based coating layer to obtain the poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) sodium salt) layer (Poly(3,4-ethylenedioxythiophene)) / Poly(sodium 4-styrenesulfonate); S3, using Mg 2+ The sensitive film solution is coated on the tip of the microneedle to obtain the Mg 2+ Sensitive film; coating method can also be dip coating, drip coating or automatic or semi-automatic coating device; S4, activating the microneedles in a MgCl2 solution.

[0011] In step S1, the steps of preparing the graphene water-based coating layer are as follows: The tip surface of the microneedle is coated with graphene by dip coating, and then dried in a constant temperature drying oven for 12-24 hours at a drying temperature of 30-40°C.

[0012] In step S2, pure nitrogen gas was introduced into the mixed solution of 3,4-ethylenedioxythiophene (EDOT) and poly(sodium 4-styrenesulfonate) (NaPSS) for 10 min to remove the air that may be present in the mixed solution; The molar ratio of the (3,4-ethylenedioxythiophene) to the poly(4-styrenesulfonic acid sodium salt) is 1:10; The electroplating conditions are as follows: the reference electrode is an Ag|AgCl|KCl (3 M) electrode, the counter electrode is a platinum sheet electrode, and the graphene-coated microneedle is a working electrode; Cyclic voltammetry was used for electroplating at a rate of 0.08-0.12 V / s, with 8-16 cycles and a voltage range of -0.2-1.5 V; After the electroplating is completed, the mixture is placed in a constant temperature drying oven and dried for 12-24 hours at a drying temperature of 30-40°C.

[0013] In step S3, the Mg 2+ The sensitive membrane solution is prepared with tetrahydrofuran, and the amount of tetrahydrofuran used is 0.8~1.2mL; Prepare the Mg 2+ The process of preparing the sensitive membrane solution is as follows: 2+ Add all the reagents of the sensitive membrane solution into a small beaker, seal the mouth of the small beaker with tin foil of appropriate size, and stir with a magnetic stirrer in a fume hood; The sensitive film is coated by dipping, and after dipping, it is placed in a constant temperature drying oven for drying for 12-24 hours at a drying temperature of 30-40°C.

[0014] In step S4, the cells were first activated in a 0.1 M MgCl2 solution for 24 h and then in a 1.0 × 10 -9 Activated in M ​​MgCl2 solution for 12 h.

[0015] The magnesium ion selective sensor of the present invention can be used for crop stem Mg 2+ In situ live detection, the steps are as follows: The crop root is placed in a KCl agar solution (KCl, 5 mmol / L; agar, 0.5 wt.%) or a KCl solution (KCl, 5 mmol / L), and a reference electrode Ag|AgCl|KCl (3 M) is inserted, the tip of the microneedle of the magnesium ion selective sensor is inserted into the incision of the crop stem, and the position of the stem and the magnesium ion selective sensor is kept fixed, and a pure agar solution (0.5 wt.% agar) at room temperature is used to cover the small incision to reduce the evaporation of the wheat seedling stem juice, the other end of the reference electrode is connected to the ground port of the hardware system for detecting the potential signal, and the other end of the sensor is connected to the high input impedance preamplifier input port of the hardware system for detecting the potential signal through a wire; that is, Mg in the crop stem is realized. 2+ In situ live detection.

[0016] The magnesium ion selective sensor of the present invention is based on the double electric layer theory. 2+The concentration signal is converted into a potential signal.

[0017] The present invention has the following beneficial technical effects: Fast response speed and low detection threshold: the all-solid-state Mg 2+ The selective electrode has a rapid and stable potential response characteristic to magnesium ions and can maintain a linear response relationship to magnesium ions in a wide concentration range. The detection limit of the electrode of the present invention is significantly reduced to 1.0×10 -7 M, thus significantly enhancing the sensitivity of the detection process and the accuracy of the measurement results; Stable potential response and long life: the all-solid-state Mg 2+ Select electrodes with good potential response stability and significantly extended service life, which means that even under long-term continuous working conditions, the potential signal output can be kept as consistent as possible to meet the application requirements of long-term crop detection; Low production cost and large-scale production potential: the all-solid Mg 2+ The electrodes made of acupuncture needles and graphene composite water-based conductive coatings are inexpensive and have a simple process flow, which reduces the cost of electrode production, facilitates large-scale industrial production, and has broad market application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure is a schematic diagram of the manufacturing process of the magnesium ion selective sensor of the present invention.

[0019] Figure 2 These are some performance parameters of the magnesium ion selective sensor of the present invention.

[0020] Figure 3 This is a schematic diagram of the application of the magnesium ion selective sensor of the present invention. DETAILED DESCRIPTION

[0021] The various terms or phrases used in the present invention have the general meanings known to those of ordinary skill in the art. Even so, the present invention still hopes to provide a more detailed description and explanation of these terms or phrases. If the terms and phrases involved in this article are inconsistent with the commonly known meanings, the meanings expressed in the present invention shall prevail; and if not defined in this application, they have the meanings commonly understood by those of ordinary skill in the art.

[0022] Combine the following Figure 1 The preparation method of the microneedle-type all-solid-state magnesium ion selective electrode for in vivo crop detection of the present invention is described as follows: 101. Pre-treat stainless steel acupuncture needles, including cleaning the acupuncture needles and installing polyimide tubes.

[0023] Furthermore, the stainless steel needle was first cleaned in anhydrous ethanol for 180 s using an ultrasonic cleaner, and then a polyimide tube with an appropriate diameter of about 1.2 cm was placed on the tip of the stainless steel needle so that the tip of the stainless steel needle was exposed about 1-2 mm from the polyimide tube, and the end of the polyimide tube close to the tip of the stainless steel needle was sealed with oily original glue.

[0024] Furthermore, stainless steel silver-plated acupuncture needles and stainless steel gold-plated acupuncture needles can be used to replace stainless steel acupuncture needles.

[0025] 102. Apply graphene water-based paint on the surface of the stainless steel needle and dry it.

[0026] Furthermore, graphene was coated on the surface of the stainless steel needle by dip coating so that the graphene completely covered the tip of the stainless steel needle. The stainless steel needle was then dried in a constant temperature drying oven at 40 °C for 12 h.

[0027] 103. Using a three-electrode system, PEDOT is electroplated on the surface of the graphene layer and dried.

[0028] Furthermore, before electroplating, pure nitrogen was introduced into the solution for 10 min to remove the air that may exist in the mixed solution of 3,4-ethylenedioxythiophene (EDOT) and poly (sodium 4-styrene sulfonate) (NaPSS). The molar ratio of EDOT and NaPSS in the mixed solution was 1:10. During electroplating, the reference electrode was Ag|AgCl|KCl (3 M) electrode, the counter electrode was a platinum sheet electrode, and the stainless steel microneedle coated with graphene was the working electrode. Cyclic voltammetry was used to electroplate PEDOT on the graphene surface at a rate of 0.1 V / s, and the cycle scan was 10 times, with a voltage range of -0.2~1.5 V. After the electroplating was completed, the microneedle was dried again in a constant temperature drying oven for 12 h at a drying temperature of 40°C.

[0029] 104. Preparation of Mg 2+ The sensitive film solution is coated on the stainless steel needle tip by dip coating and then dried.

[0030] Further, a film is coated on the stainless steel needle tip by dip coating and dried, wherein the ion exchanger contained in the sensitive membrane solution is one or more of tetrakis(3,5-bis(trifluoromethyl)phenyl)sodium borate, tetrakis(dodecyl)-tetrakis(4-chlorophenyl)ammonium borate, potassium tetraphenylborate and potassium tetrakis(4-chlorophenyl)borate. In this embodiment, sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate and tetrakis(dodecyl)-tetrakis(4-chlorophenyl)ammonium borate are selected, and the mass ratio of the two is 1:2; Mg 2+ Ion carrier is Mg 2+ One of ion carrier II and magnesium ion carrier IV, in this embodiment, Mg 2+Ion carrier II (ETH5214); plasticizer is one of o-nitrophenyl octyl ether, dioctyl phthalate, dibutyl phthalate, tricresyl phosphate or bis (2-ethylhexyl) sebacate. In this embodiment, o-nitrophenyl octyl ether is selected; polymer matrix material is polyvinyl chloride. Ion exchanger, Mg 2+ The mass ratio of ion carrier, plasticizer and polymer matrix material is 1.5:1:65:32.5. The four types of reagents are dissolved in 0.8 mL of tetrahydrofuran solution and mixed to form a sensitive membrane solution.

[0031] Furthermore, all reagents for preparing the sensitive membrane solution were added into a small beaker, the mouth of the small beaker was sealed with tin foil of appropriate size, and a magnetic stirrer was used to stir for 30 minutes in a fume hood, and the preparation of the sensitive membrane solution was completed.

[0032] Furthermore, the coating method can be dip coating, drop coating or automatic or semi-automatic coating device. The sensitive film solution is coated on the tip of the microneedle by dip coating, and then the microneedle is dried again in a constant temperature drying oven for 12 hours at a drying temperature of 40°C.

[0033] 105. Activate the dried sensor in a MgCl2 solution. After activation, the sensor is manufactured and the sensor performance is tested.

[0034] Furthermore, the sensor was activated in 0.1 M MgCl2 solution for 24 h and then in 1.0 × 10 -9 The sensor was activated in M ​​MgCl2 solution for 12 h; then the sensor response potential, detection limit and other performance were tested based on the electrochemical workstation.

[0035] 106. Sensors used in crop stems Mg 2+ In situ live detection.

[0036] Furthermore, the sensor is based on the double-layer theory and converts Mg 2+ The concentration signal is converted into a potential signal. When monitoring the potential, a fixing device is used to fix the crop. Taking wheat seedlings as an example, a sterile blade is used to cut a small incision of appropriate length in the stem longitudinally, and the tip of the sensor is inserted into the small incision to keep the stem and the sensor fixed; finally, the pure agar solution (0.5 wt.% agar) at room temperature is used to cover the small incision to reduce the evaporation of the juice in the wheat seedling stem.

[0037] Furthermore, an Ag|AgCl|KCl (3 M) reference electrode was placed at the root of the wheat seedlings, and then an appropriate amount of room temperature KCl agar solution (KCl, 5 mmol / L; agar, 0.5 wt.%) was poured between the two. The other end of the reference electrode was connected to the ground port of the hardware system for detecting the potential signal, and the other end of the sensor was connected to the high input impedance preamplifier input port of the hardware system for detecting the potential signal through a wire.

[0038] Furthermore, the sensor can be applied to crop tissue juice Mg 2+ Concentrations are measured in situ or ex vivo.

[0039] Combine the following Figure 2 Describe some performance parameters of the microneedle-type all-solid-state magnesium ion selective sensor. There are many performance parameters that can be tested, and only the response potential, detection limit and Nernst slope are shown here.

[0040] Figure 2 These are some performance parameters of the microneedle-type all-solid-state magnesium ion selective sensor for in vivo detection of crops of the present invention (only the response potential, detection limit and Nernst slope are shown).

[0041] Respectively in 10 -1 M~10 -10 The sensor was calibrated in a MgCl2 solution of 100 M. According to the Nernst equation, the ideal Nernst slope of the all-solid-state ion selective electrode based on divalent ions is 29.6 mV / dec. The detection limit of the sensor is 1.0×10 -7 M, the Nernst slope is 28.95 mV / dec, and the sensor performance is excellent.

[0042] Among them, the classic Nernst formula is as follows:

[0043] In the formula, is the electrode potential, i.e., the sensor potential obtained based on the open circuit potential of the electrochemical workstation; for =1, standard electrode potential; is the metal ion, z is the charge number, For metal ions Activity in solution; R is the gas constant, T is the absolute temperature; F is the Faraday constant. In the concentration range, and It is a linear relationship, and its slope is the Nernst slope.

[0044] Literature shows that Mg in plant stem xylem 2+ The concentration is mM level, and the sensor of the present invention is 10 -1 ~10 -5 The response in M ​​MgCl2 solution is stable and meets the test requirements.

[0045] Figure 3 This is the application scenario of the microneedle all-solid-state magnesium ion selective sensor for in vivo detection of crops of the present invention. The present invention uses wheat seedlings as an example to illustrate the application method of the sensor.

[0046] like Figure 3 As shown, in this embodiment, 1 is a Ag|AgCl|KCl (3 M) reference electrode; 2 is wheat seedlings hydroponically cultured with Hoagland nutrient solution for about 6 weeks; 3 is a sensor, and 4 is an appropriate amount of room temperature KCl agar solution (KCl, 5 mmol / L; agar, 0.5wt.%).

[0047] During the test, a sterile blade is used to cut a small incision of appropriate length in the stem longitudinally, and the tip of the sensor is inserted into the small incision while keeping the stem and the sensor fixed. Finally, a pure agar solution (0.5wt.% agar) at room temperature is used to cover the small incision to reduce the evaporation of the juice in the wheat seedling stem.

[0048] During the test, the A port connected to the reference electrode is connected to the ground port of the hardware system for detecting the potential signal, and the B port connected to the sensor is connected to the high input impedance preamplifier input port of the hardware system for detecting the potential signal through a wire.

[0049] The entire wheat seedling testing process was carried out in a Faraday cage.

[0050] Through the description of the above implementation modes, those skilled in the art can clearly understand that each implementation mode can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., including a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A microneedle type all-solid-state magnesium ion selective sensor, comprising a microneedle and a polyimide tube sleeved outside the microneedle, wherein the tip of the microneedle extends 1-2 mm outside the polyimide tube; The tip of the microneedle is coated with a graphene water-based coating layer, a poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonic acid) sodium salt) layer and a Mg 2+ Sensitive membrane.

2. The microneedle type all-solid-state magnesium ion selective sensor according to claim 1, characterized in that: The micro needle is a stainless steel silver-plated acupuncture needle, a stainless steel gold-plated acupuncture needle, or a stainless steel acupuncture needle; The polyimide tube has a diameter of 0.2-0.3 mm and a thickness of 0.02-0.04 mm; The tube opening of the polyimide tube close to the tip of the micro needle is sealed by oily original glue.

3. The microneedle type all-solid-state magnesium ion selective sensor according to claim 1 or 2, characterized in that: The Mg 2+ The sensitive film is made of Mg 2+ The sensitive membrane solution contains ion exchanger, Mg 2+ Ionophores, plasticizers and polymer matrix materials.

4. The microneedle type all-solid-state magnesium ion selective sensor according to claim 3, characterized in that: The ion exchanger is one or more of sodium tetrakis(3,5-di(trifluoromethyl)phenyl)borate, tetrakis(dodecyl)-tetrakis(4-chlorophenyl)ammonium borate, potassium tetraphenylborate and potassium tetrakis(4-chlorophenyl)borate; The Mg 2+ Ion carrier is Mg 2+ Ionophore II and Mg 2+ One of the ionophores IV; The plasticizer is one of o-nitrophenyl octyl ether, dioctyl phthalate, dibutyl phthalate, tricresyl phosphate or bis(2-ethylhexyl) sebacate; The polymer matrix material is polyvinyl chloride; The ion exchanger, the Mg 2+ The mass ratio of the ion carrier, the plasticizer and the polymer matrix material is 1.0-1.5: 0.8-1.2: 64.5-65: 32-32.

5. In addition, the ion exchanger and Mg 2+ The molar ratio of the ion carrier is 0.30~1.55:

1.

5. A method for preparing the magnesium ion selective sensor according to any one of claims 1 to 4, comprising the following steps: S1, applying a graphene water-based coating on the tip of the microneedle to obtain the graphene water-based coating layer; S2, using a three-electrode system, electroplating (3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) on the surface of the graphene water-based coating layer to obtain the poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonic acid) sodium salt) layer; S3, using the dip coating method, using Mg 2+ The sensitive film solution is coated on the tip of the microneedle to obtain the Mg 2+ Sensitive membrane; S4, activating the microneedles in a MgCl2 solution.

6. The preparation method according to claim 5, characterized in that: In step S1, the steps of preparing the graphene water-based coating layer are as follows: After the graphene water-based coating layer is dip-coated, the microneedle is dried in a constant temperature drying oven for 12-24 h at a drying temperature of 30-40°C.

7. The preparation method according to claim 5 or 6, characterized in that: In step S2, the molar ratio of the 3,4-ethylenedioxythiophene to the poly(4-styrenesulfonic acid sodium salt) is 1:10; The electroplating conditions are as follows: electroplating at a rate of 0.08-0.12 V / s using cyclic voltammetry, 8-16 cycles of scanning, and a voltage range of -0.2-1.5 V; After the electroplating is completed, the mixture is placed in a constant temperature drying oven and dried for 12-24 hours at a drying temperature of 30-40°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that: In step S3, the Mg 2+ The sensitive membrane solution is prepared from tetrahydrofuran; The Mg 2+ After dip coating, the sensitive film is placed in a constant temperature drying oven for 12-24 hours at a drying temperature of 30-40°C.

9. The magnesium ion selective sensor according to any one of claims 1 to 4 is used for crop stem Mg 2+ Application in in situ live detection.

10. Mg from a crop stem 2+ The in situ liveness detection method comprises the following steps: The root of the crop is placed in a KCl agar solution or a KCl solution; and an Ag|AgCl|KCl reference electrode is inserted into the solution, and the tip of the microneedle of the magnesium ion selective sensor according to any one of claims 1 to 4 is inserted into the incision of the crop stem, and the position of the stem and the magnesium ion selective sensor is kept fixed, so as to achieve Mg in the crop stem. 2+ In situ live detection.

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