Reversible background-free hydrogel nanosensor and intelligent sensing platform for acetone detection

Abstract

The invention discloses a reversible background-free hydrogel nanosensor for acetone detection and an intelligent sensing platform, and relates to the technical field of biosensors. The hydrogel nanosensor consists of a hydrogel matrix and an upconversion nanoprobe, and the upconversion nanoprobe comprises upconversion nanoparticles (UCNPs), hydroxylamine sulfate and thymol blue (TB). The invention adopts hydroxylamine sulfate as a specific recognition unit of acetone to construct a reversible luminescent hydrogel probe for acetone detection, and the probe can be reused in multiple detections, thereby reducing the cost of a single detection. In addition, by adopting near-infrared light as an excitation light source, the autofluorescence interference of the hydrogel matrix is ​​effectively avoided, thereby improving the detection accuracy.

Description

Technical Field

[0001] The present invention relates to the field of biosensor technology, and in particular to a reversible background-free hydrogel nanosensor and an intelligent sensing platform for acetone detection. Background Art

[0002] Acetone, as an important volatile organic compound (VOC) in exhaled breath, has attracted considerable attention in the medical field in recent years. The potential of acetone as a disease biomarker provides new possibilities for early disease diagnosis and prevention. Therefore, detecting the concentration of acetone in exhaled breath has become a promising method for assessing individual health status, monitoring disease progression, and evaluating treatment efficacy.

[0003] Traditional acetone detection methods, such as gas chromatography, gas chromatography-mass spectrometry, and spectrophotometry, although they perform well in terms of accuracy, are limited in practical applications due to cumbersome operations and expensive instrument requirements. In contrast, fluorescent probes have attracted widespread attention due to their simple operation, high sensitivity, and visualization, and have broad application prospects in the fields of biomedicine and environmental monitoring. In addition, fixing fluorescent probes on paper substrates to construct fluorescent test strips and combining them with smart sensing platforms can provide a portable, sensitive, and low-cost method for acetone detection, avoiding the use of complex laboratory instruments and time-consuming sample pretreatment processes, and achieving real-time, in situ, and visual detection. However, the attachment of fluorescent probes to paper substrates often leads to uneven probe distribution and an increase in non-radiative transitions, which in turn can lead to changes in fluorescence signals and fluorescence quenching, ultimately reducing the sensitivity of detection.

[0004] In contrast, hydrogels are ideal carriers of fluorescent probes due to their unique semi-wet structure, excellent transparency, and mechanical strength. During the preparation of hydrogels, fluorescent probes can be uniformly incorporated into their networks. In addition, hydrogels provide a porous semi-wet structure that maintains high selectivity and sensitivity in detection comparable to that in a liquid environment. However, current fluorescent hydrogel nanosensors still have the following technical challenges: (1) The hydrogel matrix will undergo autofluorescence under short-wavelength excitation, thus affecting the fluorescent detection signal; (2) Recyclability is a key criterion for creating an ideal sensor, and most fluorescent sensors rely on irreversible chemical reactions. Therefore, this irreversibility of the chemical reaction hinders the recyclability of the fluorescent probe, thereby increasing the cost of hydrogel-based fluorescent sensors.

[0005] Recently, nanoprobes based on upconversion nanoparticles (UCNPs) have attracted extensive attention due to their unique optical properties. Specifically, upconversion nanoprobes convert long-wave near-infrared light into visible or near-infrared light, thereby achieving highly sensitive optical detection while minimizing background interference. In addition, upconversion nanoprobes also exhibit excellent optical and chemical stability, maintaining stable luminescence properties under various experimental conditions. These advantages make upconversion nanoprobes promising for a wide range of applications in biomedical imaging, biosensing, and therapy. Therefore, the use of UCNPs to construct a luminescent hydrogel sensor for the detection of acetone is an effective way to alleviate the problem of autofluorescence caused by the hydrogel matrix. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a reversible background-free hydrogel nanosensor for acetone detection. By embedding an upconversion nanoprobe that specifically recognizes acetone into a hydrogel network, high-sensitivity, reversible and dual-modal (colorimetric and luminescent) detection of acetone is achieved. The upconversion nanoprobe is composed of hydroxylamine sulfate as a recognition unit, thymol blue sodium salt (TB) as an energy acceptor and UCNPs as an energy donor. Its unique sensing mechanism can trigger color change and luminescence quenching in the presence of acetone. In addition, the present invention also uses 3D printing technology to construct a portable intelligent sensing platform, which integrates a laser, a cuvette and a smart phone for rapid on-site detection. The platform not only overcomes the limitations of traditional sensors in sensitivity and reversibility, but also demonstrates the ability to accurately monitor acetone exhaled by the human body, and has broad application prospects in the early diagnosis and health management of diseases such as diabetes.

[0007] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0008] The first object of the present invention is to provide a reversible background-free hydrogel nanosensor, which is composed of a hydrogel matrix and an upconversion nanoprobe, wherein the hydrogel matrix is ​​a polyacrylamide (PAM) hydrogel, and the upconversion nanoprobe includes UCNPs, hydroxylamine sulfate and TB.

[0009] In the present invention, long-wavelength excitation of UCNPs is used to avoid the autofluorescence interference of the hydrogel matrix, hydroxylamine sulfate is used as the specific recognition unit of acetone, TB is used as the energy acceptor, and the reversible reaction of TB protonation and deprotonation is utilized to achieve reversible, background-free and dual-modal (colorimetric and luminescent) detection of acetone.

[0010] The second object of the present invention is to provide an intelligent sensing platform, comprising the reversible background-free hydrogel nanosensor.

[0011] The third object of the present invention is to provide the application of the reversible background-free hydrogel nanosensor or the intelligent sensing platform in acetone detection.

[0012] The beneficial effects of the present invention are:

[0013] 1. The present invention uses hydroxylamine sulfate as a specific recognition unit for acetone to construct a reversible luminescent hydrogel probe for acetone detection. This means that the probe can be reused in multiple tests, thereby reducing the cost of a single test. Compared with some detection methods that require consumable materials or can only be used once, reversible detection luminescent probes provide a more economical and efficient option, especially in applications that require large-scale sample testing or long-term monitoring. This advantage is particularly obvious.

[0014] 2. The present invention effectively avoids the autofluorescence interference of the hydrogel matrix by using near-infrared light as the excitation light source, thereby improving the detection accuracy.

[0015] 3. The present invention utilizes the three-dimensional network structure and semi-wet characteristics of the hydrogel to alleviate the problem of poor sensitivity of the fluorescent probe caused by uneven distribution and low loading.

[0016] 4. The intelligent sensing platform constructed by the present invention can perform on-site detection of acetone sensitively and quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 (A) is a schematic diagram of the mechanism of the upconversion nanoprobe of the present invention for detecting acetone; Figure 1 (B) is a schematic diagram of the preparation process of the hydrogel nanosensor of the present invention and a schematic diagram of its mechanism for detecting acetone;

[0018] Figure 2 (A) is NaYF synthesized in Example 1 4 : Low-resolution TEM image of Yb, Er upconversion nanoparticles; Figure 2 (B) Figure 2 (C) Figure 2 (D) are respectively NaYF synthesized in Example 1 4 :Yb,Er@NaYF 4 Low-resolution TEM images, high-resolution images, and XRD patterns of upconversion nanoparticles;

[0019] Figure 3 (A) is the upconversion luminescence (UCL) spectrum of the upconversion nanoprobe prepared in Example 1 after adding acetone solutions of different concentrations (0-220 μM), and the inset shows the change of UCL color with increasing acetone concentration; Figure 3 (B) Reason Figure 3 (A) Calculated I540 / I 650 The linear fitting curve between the concentration of acetone and the Figure 3 (C) is the UV-visible absorption spectrum of the upconversion nanoprobe prepared in Example 1 after adding acetone solutions of different concentrations (0-220 μM), and the inset shows the change in the color of the probe solution with increasing acetone concentration; Figure 3 (D) is a linear fitting curve between the absorbance of the upconversion nanoprobe prepared in Example 1 at 548 nm and the acetone concentration; Figure 3 (E) is the upconversion luminescence spectrum of the upconversion nanoprobe prepared in Example 1 after adding acetone solution (220 μM) under different pH conditions (pH=1~3); Figure 3 (F) shows the upconversion nanoprobe prepared in Example 1 during the cycle of adding acetone solution and adjusting pH value. 540 / I 650 Change diagram, the illustration shows the cyclic change of UCL color;

[0020] Figure 4 The selectivity (red) and anti-interference (blue) test results of the upconversion nanoprobe prepared in Example 1 in the luminescence mode (A) and the colorimetric mode (B); wherein 1-blank, 2-acetone, 3-carbonate, 4-ethanol, 5-ammonia, 6-ether, 7-propanol, 8-isopropanol, 9-S 2- , 10-SO 4 2- , 11-Ca 2+ , 12-Na + ;

[0021] Figure 5 (A) Optical images of the hydrogel nanosensor prepared in Example 1 under ambient conditions, ultraviolet light (365 nm) excitation, and near-infrared light (980 nm) excitation; Figure 5 (B) is the SEM image of the hydrogel nanosensor prepared in Example 1; Figure 5 (C) is the colorimetric response of the hydrogel nanosensor prepared in Example 1 after adding acetone solutions of different concentrations (0-220 μM); Figure 5 (D) is the color and UCL image of the hydrogel nanosensor prepared in Example 1 after adding acetone solution and adjusting the pH value; Figure 5 (E) The hydrogel nanosensor prepared in Example 1 during the cycle of adding acetone solution and adjusting pH value 540 / I 650 Change graph.

[0022] Figure 6 (A) is a model scheme for detecting acetone using the intelligent sensing platform constructed in Example 2; Figure 6(B) is a UCL image taken by a smartphone after the hydrogel nanosensor prepared in Example 1 was placed in acetone gas for 30 min; Figure 6 (C) is the relationship between G / R and acetone concentration; the inset is the chromaticity evolution of UCL in the dual-modal hydrogel sensor shown in the CIE 1931 (x, y) chromaticity diagram;

[0023] Figure 7 (A) The hydrogel nanosensor prepared in Example 1 and the GC-MS method were used to monitor the acetone concentration in the exhaled gas of healthy volunteers; Figure 7 (B) The hydrogel nanosensor prepared in Example 1 and the GC-MS method were used to monitor the acetone concentration in the exhaled gas of diabetic volunteers. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments and diagrams.

[0025] The invention provides a reversible background-free hydrogel nanosensor, which consists of a hydrogel matrix and an upconversion nanoprobe. The hydrogel matrix is ​​a PAM hydrogel, and the upconversion nanoprobe comprises UCNPs, hydroxylamine sulfate and TB.

[0026] In the present invention, the concentration of UCNPs in the upconversion nanoprobe is 0.8-1.2 mg / mL, the concentration of hydroxylamine sulfate is 30-50 mmol / L (mM), and the concentration of TB is 200-300 μmol / L (μM), based on 2 mL of the upconversion nanoprobe solution.

[0027] In the present invention, the upconversion nanoprobe is encapsulated into the 3D network structure of PAM, and the high optical transparency and stable 3D network structure of PAM hydrogel provide a good detection environment for UCNPs, while achieving high loading capacity and rapid molecular diffusion. Specifically, the PAM hydrogel is synthesized from N,N'-methylenebisacrylamide and acrylamide through free radical induced polymerization.

[0028] In the present invention, the UCNPs have a core-shell structure, with β-NaYF 4 :Yb, Er as core, NaYF 4 For the shell.

[0029] Furthermore, the UCNPs are prepared from rare earth chloride, oleic acid (OA), 1-octadecene (ODE), ammonium fluoride (NH 4F) and sodium hydroxide (NaOH) as raw materials through a solvothermal method. Wherein, rare earth chloride is used as a precursor, OA is used as a ligand, and OA and ODE are used as a mixed solvent. The rare earth chloride includes but is not limited to chlorides of yttrium, ytterbium, and erbium. The reaction temperature of the solvothermal method is 100-300°C, and the reaction time is 30-60min.

[0030] As a specific embodiment, the preparation method of UCNPs comprises the following steps:

[0031] (1) Yttrium chloride hexahydrate (YCl 3 6H 2 O), ytterbium chloride hexahydrate (YbCl 3 6H 2 O), erbium chloride hexahydrate (ErCl 3 6H 2 O), OA, ODE, NH 4 Preparation of NaYF by reaction of F and NaOH 4 :Yb, Er upconversion nanoparticles;

[0032] (2) By NaYF 4 :Yb, Er upconversion nanoparticles, YCl 3 6H 2 O, OA, ODE, NH 4 Preparation of core-shell NaYF by reaction of F and NaOH 4 :Yb,Er@NaYF 4 Upconversion nanoparticles.

[0033] Furthermore, in order to avoid the influence of oxidation reaction on nanoparticles, the preparation process of UCNPs is in a protective atmosphere (such as argon).

[0034] Furthermore, in order to improve the water solubility and biocompatibility of UCNPs, the present invention uses acid treatment and surface modification of polyacrylic acid to transform the synthesized hydrophobic UCNPs into hydrophilic UCNPs.

[0035] The present invention provides an intelligent sensing platform, comprising the reversible background-free hydrogel nanosensor.

[0036] Furthermore, the intelligent sensing platform also includes a 980 nm laser, a cuvette, a smartphone and 3D printed accessories. Through the smartphone's camera and its built-in color analysis software, the light signal emitted by the hydrogel can be accurately captured and analyzed, achieving rapid and accurate determination of the acetone concentration in the sample.

[0037] The present invention provides an application of the reversible background-free hydrogel nanosensor or the intelligent sensing platform in acetone detection, including acetone detection in solution and acetone detection in exhaled breath, and is particularly used for monitoring changes in acetone concentrations that are closely related to health conditions such as diabetes and cancer.

[0038] The TB solution in the present invention is a TB aqueous solution; the hydroxylamine sulfate solution is a hydroxylamine sulfate aqueous solution; the acetone solution is an acetone aqueous solution; and the interferor solution is an interferor aqueous solution.

[0039] Example 1

[0040] Preparation of hydrogel nanosensors:

[0041] (1)NaYF 4 Preparation of Yb, Er upconversion nanoparticles

[0042] Weigh 3.9 mmol YCl 3 6H 2 O, 1 mmol YbCl 3 6H 2 O, 0.1 mmol ErCl 3 6H 2 O was mixed with 30 mL OA and 75 mL ODE, heated to 160 °C and stirred for 1 h, and cooled to room temperature; then 50 mL of 20 mmol NH 4 A methanol solution of F and 12.5 mmol NaOH was heated to 50 °C and stirred for 30 min, then heated to 110 °C in a vacuum and kept warm for 20 min, and then heated to 300 °C in an argon atmosphere and kept warm for 1 h. After the reaction was completed, the solution was cooled to room temperature and washed three times with ethanol and cyclohexane to obtain NaYF 4 :Yb, Er upconversion nanoparticles.

[0043] (2) Core-shell structure NaYF 4 :Yb,Er@NaYF 4 Preparation of upconversion nanoparticles

[0044] 1 mmol YCl 3 6H 2 O was mixed with 6 mL OA and 15 mL ODE, heated to 160°C in an argon-filled environment and stirred until the solution became transparent, then cooled to room temperature; NaYF prepared in step (1) was added under stirring. 4 :Yb, Er upconversion nanoparticles, and add 10 mL of 4 mmol NH 4F and 2.5 mmol NaOH in methanol solution, heated to 50 °C and stirred for 30 min, then heated to 110 °C in vacuum and kept warm for 20 min, and then heated to 300 °C in argon atmosphere and kept warm for 1 h. After the reaction, the product was washed three times with ethanol, and the obtained UCNPs were dispersed in 50 mL cyclohexene.

[0045] (3) Preparation of hydrophilic UCNPs

[0046] In order to change the hydrophobicity of UCNPs caused by OA ligands, an acidic treatment strategy was adopted to promote the protonation of OA ligands and their shedding from the surface of UCNPs. Subsequently, the surface of UCNPs was modified with polyacrylic acid (PAA) to achieve the hydrophilic conversion of UCNPs. The specific steps are as follows:

[0047] 200 mg of UCNPs prepared in step (2) were separated from cyclohexane by ethanol precipitation, and then the UCNPs were placed in 60 mL of hydrochloric acid solution with a pH of 1, ultrasonically treated for 1 h to strip off the OA ligand, centrifuged, washed twice with ultrapure water, and then dispersed in 20 mL of ultrapure water to obtain a UCNPs solution.

[0048] 300 mg PAA was dissolved in 30 mL diethylene glycol, heated to 110 °C for 1 h, then the UCNPs solution was added and vigorously stirred for 30 min, then the temperature was raised to 240 °C for 2 h, cooled, and the UCNPs-PAA composite material was collected by centrifugation, washed three times with deionized water, and finally dispersed in 20 mL ultrapure water to obtain a hydrophilic UCNPs solution with a concentration of 10 mg / mL, which was stored at 4 °C for later use.

[0049] (4) Preparation of upconversion nanoprobes

[0050] 100 μL of the hydrophilic UCNPs solution prepared in step (3), 50 μL of TB solution (10 mmol / L) and 200 μL of hydroxylamine sulfate solution (400 mmol / L) were mixed evenly, and the solution volume was diluted to 2 mL with deionized water to obtain an upconversion nanoprobe solution.

[0051] (5) Preparation of hydrogel nanosensors

[0052] 3 g acrylamide, 0.05 g N,N'-methylenebisacrylamide, 0.3 g calcium chloride dihydrate and 45 mg ammonium persulfate were dissolved in 24.75 mL deionized water, and 1.5 mL of the hydrophilic UCNPs solution prepared in step (3) and 0.75 mL of TB solution (10 mmol / L) and 3 mL of hydroxylamine sulfate solution (400 mmol / L) were added. After mixing evenly, the mixture was injected into the mold, and then 50 μL of 10 wt% tetramethylethylenediamine was added to promote gelation. The mixture was cured at room temperature to obtain a hydrogel nanosensor.

[0053] from Figure 2 It can be observed that the UCNPs synthesized in Example 1 exhibit a spherical morphology with uniform particle size distribution; 4 After shell encapsulation, the average diameter of UCNPs increased from 26.03 nm ( Figure 2 A) increases to 28.06 nm ( Figure 2 B); NaYF 4 :Yb,Er@NaYF 4 Upconversion nanoparticles have uniformly distributed lattice fringes ( Figure 2 C); NaYF 4 :Yb, Er upconversion nanoparticles and NaYF 4 :Yb,Er@NaYF 4 The XRD characteristic peaks of the upconversion nanoparticles match well with the standard PDF card (powder diffraction file, JCPDS16-0334) ( Figure 2 D), this hexagonal crystal structure facilitates energy transfer between rare earth ions, thereby significantly improving the UCL efficiency.

[0054] Figure 5 (A) Optical images of the hydrogel nanosensor prepared in Example 1 under ambient conditions, ultraviolet light (365 nm) excitation, and near-infrared light (980 nm) excitation; Figure 5 (B) is the SEM image of the hydrogel nanosensor prepared in Example 1.

[0055] from Figure 5 (A) It can be seen that the hydrogel nanosensor prepared in Example 1 is colorless and transparent under ambient light, emits fluorescence under ultraviolet light, and has no obvious luminescence under 980 nm laser, which is conducive to the propagation of UCL signals in the hydrogel without affecting the UCL intensity.

[0056] from Figure 5 (B) It can be seen that the dual-modal sensor prepared in Example 1 has a porous network structure, which is conducive to the high loading of upconversion nanoprobes and the diffusion of acetone molecules.

[0057] Example 2

[0058] Preparation of hydrogel nanosensors:

[0059] The preparation method of the hydrogel nanosensor in Example 2 is the same as that in Example 1, except that: 4 :Yb,Er@NaYF 4 The solvothermal reaction conditions for the upconversion nanoparticles were to first heat to 100 °C in a vacuum for 30 min and then heat to 250 °C in an argon atmosphere for 1.5 h.

[0060] Example 3

[0061] Preparation of hydrogel nanosensors:

[0062] The preparation method of the hydrogel nanosensor in Example 3 is the same as that in Example 1, except that: 4 YCl:Yb,Er upconversion nanoparticles 3 6H 2 O, YbCl 3 6H 2 O、ErCl 3 6H 2 The molar amounts of O were 3.85 mmol, 1 mmol, and 0.15 mmol, respectively.

[0063] Example 4

[0064] Preparation of hydrogel nanosensors:

[0065] The preparation method of the hydrogel nanosensor in Example 4 is the same as that in Example 1, except that a TB solution with a concentration of 8 mmol / L is added during the preparation of the hydrogel nanosensor.

[0066] Example 5

[0067] Preparation of hydrogel nanosensors:

[0068] The preparation method of the hydrogel nanosensor in Example 5 is the same as that in Example 1, except that a hydroxylamine sulfate solution with a concentration of 500 mmol / L is added during the preparation of the hydrogel nanosensor.

[0069] Example 6

[0070] Luminescence and colorimetric responsiveness test of upconversion nanoprobe to acetone solution:

[0071] Acetone solutions of different concentrations (0, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220 μM) were added to the upconversion nanoprobe solution prepared in Example 1, mixed evenly and incubated for 20 min, and the UCL spectrum of the probe solution in the wavelength range of 500-700 nm under 980 nm laser excitation was recorded using a smartphone to complete the luminescence detection of acetone ( Figure 3 A and 3B). At the same time, the absorbance of the probe solution was measured in the range of 500-700 nm to achieve colorimetric detection of acetone ( Figure 3 C and 3D).

[0072] from Figure 3 As can be seen from Figure A, as the acetone concentration increases from 0 to 220 μM, the green UCL signal gradually weakens, while the red UCL signal remains stable, realizing the transition of UCL color from green to red.

[0073] from Figure 3 B can be seen that Figure 3 The UCL intensity in A is higher than that in I 540 / I 655 As a detection indicator, this indicator is linearly correlated with the acetone concentration in the acetone concentration range of 0 to 220 μM. LOD was calculated according to the formula LOD=3*δ / S, where δ represents the standard deviation based on 10 blank experiments and S is the slope of the linear regression equation. The results showed that in the luminescence mode, LOD reached an extremely low level of 7.6 nM.

[0074] from Figure 3 C shows that the probe solution exhibits a colorimetric response to acetone. Hydroxylamine sulfate reacts with acetone to generate a red addition product (H + ) caused TB to be protonated, and the absorbance at 540 nm increased with the increase of acetone concentration. Figure 3 The inset in C shows the color of the probe solution changing from yellow to red, visually indicating the presence and concentration change of acetone.

[0075] from Figure 3 D It can be seen that in the acetone concentration range of 0 to 220 μM, the absorbance at 540 nm showed a good linear relationship with the acetone concentration, and the LOD was as low as 7.6nM (R²=0.989).

[0076] Example 7

[0077] Reversibility test of upconversion nanoprobe on acetone solution:

[0078] Acetone solution (220 μM) was added to the upconversion nanoprobe solution prepared in Example 1, mixed evenly and incubated for 20 min, the pH value of the solution was adjusted (pH = 1-3), and the UCL spectrum of the probe solution in the wavelength range of 500-700 nm under 980 nm laser excitation was recorded using a smartphone ( Figure 3 E).

[0079] from Figure 3 E It can be seen that when the pH value of the probe solution is adjusted from 1 to 3, its UCL intensity at 540 nm increases.

[0080] Acetone solution (220 μM) was added to the upconversion nanoprobe solution prepared in Example 1, mixed evenly and incubated for 20 min, the pH value of the solution was adjusted to 3, and acetone solution (220 μM) was added after the solution changed color, and then the pH value of the solution was adjusted to 3 again. Acetone addition and pH adjustment were performed multiple times, and the UCL spectrum of the probe solution in the wavelength range of 500-700 nm under 980 nm laser excitation was recorded using a smartphone, and I was calculated. 540 / I 655 ( Figure 3 F).

[0081] from Figure 3 F It can be seen that even after multiple additions of acetone and adjustment of pH, the probe solution still maintains a sensitive and accurate response to acetone, thereby verifying the reversibility of the upconversion nanoprobe.

[0082] Example 8

[0083] Selectivity and anti-interference test of upconversion nanoprobe for acetone solution:

[0084] A 220 μM acetone solution or an interfering substance solution (interfering substances include carbonate, ethanol, ammonia, ether, propanol, isopropanol, S 2- 、SO 4 2- , Ca 2+ 、Na + ) were added to the upconversion nanoprobe solution prepared in Example 1, mixed evenly and incubated for 20 min, and the UCL spectrum of the probe solution in the range of 500-700 nm was recorded by a smartphone using a 980 nm laser, and analyzed by the built-in color recognition software to complete the luminescence detection of acetone ( Figure 4 A). At the same time, the absorbance of the probe solution was measured in the range of 500-700 nm to achieve colorimetric detection of acetone ( Figure 4 B).

[0085] In order to verify the accuracy and practicality of the upconversion nanoprobe, the present invention tested its selectivity and anti-interference by adding different types of potential interferents to the probe solution. Figure 4 It can be seen that no matter which interfering substance is added, the I 540 / I 655 However, when 220 μM acetone solution was added to the probe solution, I 540 / I 655 The intensity of the UCL is significantly reduced, and the UCL color is obviously shifted to red. This result shows that the upconversion nanoprobe designed in the present invention has excellent selectivity and anti-interference ability in acetone detection and can adapt to complex detection environments.

[0086] Example 9

[0087] Colorimetric responsiveness test of hydrogel nanosensor to acetone solution:

[0088] Acetone solutions of different concentrations (0, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220 μM) were added to the hydrogel nanosensor prepared in Example 1, mixed well, incubated for 20 min, and then the color change of the hydrogel was recorded using a smartphone.

[0089] from Figure 5 C It can be seen that with the increase of acetone concentration, the hydrogel sensor gradually changes from yellow to red, which indicates that the hydrogel nanosensor designed in the present invention can perform visual detection of the concentration of acetone solution.

[0090] Example 10

[0091] Reversibility test of hydrogel nanosensor to acetone solution:

[0092] Acetone solution (220 μM) was added to the hydrogel nanosensor prepared in Example 1, mixed evenly and incubated for 20 min, the pH value of the solution was adjusted to 3, and acetone solution (220 μM) was added after the solution changed color, and then the pH value of the solution was adjusted to 3 again. Acetone addition and pH adjustment were performed multiple times, and the UCL spectrum of the probe solution in the wavelength range of 500-700 nm under 980 nm laser excitation was recorded using a smartphone, and I 540 / I 655 ( Figure 5 E).

[0093] from Figure 5(D) It can be seen that under 980 nm near-infrared laser excitation, the hydrogel nanosensor appears yellow and emits green UCL. After adding acetone, the hydrogel nanosensor appears red and displays red UCL. After adjusting the pH, the deprotonation reaction of TB causes the color of the hydrogel to change from red to yellow again, and the green UCL returns to its initial state. In addition, the pH adjustment process is completed by simply immersing the hydrogel nanosensor in water with a pH of 3, ensuring that there is no volume effect that destroys the luminescence detection signal compared to the upconversion nanoprobe. Therefore, the hydrogel nanosensor achieves a satisfactory reversible response based on the protonation and deprotonation of acetone.

[0094] from Figure 5 (E) It can be seen that after more than ten reversible detection cycles, the UCL intensity of the hydrogel nanosensor changes very little, so the hydrogel nanosensor designed in the present invention achieves a reversible response to acetone.

[0095] Embodiment 11

[0096] Intelligent sensing platform luminescence responsiveness test to acetone gas:

[0097] An intelligent sensing platform including a smartphone, a 980 nm laser, a 3D printing platform, a dark box, and a cuvette holder was constructed. A quartz tube containing the hydrogel nanosensor prepared in Example 1 was placed on the sensing platform and placed in an acetone gas environment of different concentrations (1-10 ppm) for 30 min. The UCL spectrum emitted by the hydrogel was recorded using the smartphone camera under 980 nm light excitation, and the RGB values ​​were analyzed and recorded using the built-in color recognition software of the smartphone ( Figure 6 A).

[0098] from Figure 6 B shows that as the acetone concentration in the gas increases from 0 ppm to 10 ppm, the UCL gradually changes from green to red. This finding is of great significance for the detection of acetone gas because it provides an intuitive, rapid and easy-to-operate method to monitor changes in acetone concentration.

[0099] from Figure 6 C It can be seen that the green-red emission ratio (G / R) has a good linear relationship with the acetone concentration in the gas (R 2 =0.997, y=-0.0828x+1.0964)( Figure 6C). According to the linear regression equation, the LOD of the sensing platform based on the hydrogel nanosensor is calculated to be 34 ppb, which indicates that it has a high detection sensitivity for gaseous acetone. Therefore, the upconversion hydrogel sensor developed by the present invention has a good response to the acetone content in the gas phase. In addition, the intelligent sensing platform designed by the present invention solves the problems of high cost and complex detection process associated with traditional detection methods.

[0100] Example 12

[0101] Detection of acetone in actual samples:

[0102] Samples were collected from the exhaled gas of diabetic patients and healthy volunteers in one day, and the samples were placed in sample bags. The hydrogel nanosensor prepared in Example 1 was exposed to these gas samples, and then the intelligent sensing platform constructed based on the hydrogel nanosensor of the present invention was tested, and the optical sensing signal was recorded. The acetone concentration in the human respiratory gas was further analyzed by the linear regression equation between the acetone concentration and G / R obtained. In addition, the acetone concentration in the breath sample was quantitatively analyzed by gas chromatography-mass spectrometry (GC-MS) to verify the accuracy of the intelligent sensing platform.

[0103] Figure 7 (A) The hydrogel nanosensor prepared in Example 1 and the GC-MS method were used to monitor the acetone concentration in the exhaled gas of healthy volunteers; Figure 7 (B) The hydrogel nanosensor prepared in Example 1 and the GC-MS method were used to monitor the acetone concentration in the exhaled gas of diabetic volunteers.

[0104] from Figure 7 It can be seen that the hydrogel nanosensor designed in the present invention performs well in monitoring the changes in acetone levels in the exhaled gas of healthy volunteers and diabetic patients in the fasting and postprandial states, and its analysis results are highly consistent with GC-MS, confirming the reliability and practicality of the hydrogel nanosensor designed in the present invention for acetone health monitoring in exhaled gas.

[0105] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. Application of a reversible background-free hydrogel nanosensor in acetone detection, wherein the hydrogel nanosensor is composed of a hydrogel matrix and an upconversion nanoprobe, wherein the hydrogel matrix is ​​a PAM hydrogel, and the upconversion nanoprobe includes UCNPs, hydroxylamine sulfate and thymol blue sodium salt (TB); The UCNPs are prepared by a solvothermal method; The reaction temperature of the solvothermal method is 100-300°C, and the reaction time is 30-60 min; The UCNPs have a core-shell structure, with β-NaYF4:Yb,Er as the core and NaYF4 as the shell; The preparation method of the UCNPs comprises the following steps: (1) NaYF4:Yb,Er upconversion nanoparticles were prepared by reacting YCl3·6H2O, YbCl3·6H2O, ErCl3·6H2O, OA, ODE, NH4F and NaOH; (2) The core-shell structured NaYF4:Yb,Er@NaYF4 upconversion nanoparticles were prepared by reacting NaYF4:Yb,Er upconversion nanoparticles, YCl3·6H2O, OA, ODE, NH4F and NaOH.

2. The use according to claim 1, characterized in that: The PAM hydrogel is synthesized from N,N'-methylenebisacrylamide and acrylamide through free radical induced polymerization.

3. The use according to claim 1, characterized in that: The preparation process of the UCNPs is carried out in a protective atmosphere.

4. The use according to claim 1, characterized in that: The UCNPs are transformed from hydrophobic to hydrophilic by acid treatment and surface modification with polyacrylic acid.

5. Application of an intelligent sensing platform in acetone detection, comprising the reversible background-free hydrogel nanosensor described in any one of claims 1 to 4.

6. The use according to claim 5, characterized in that: The smart sensing platform also includes a 980 nm laser, a cuvette, a smartphone, and 3D-printed accessories.

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