Fluorescent cellulose, method for preparing the same, and fiber membrane and application thereof

Abstract

The application discloses fluorescent cellulose, a preparation method thereof, and a fiber membrane and application thereof, and has a structural formula shown in formula I: wherein n is 600-1000; R1 and R2 are independently selected from H or the fluorescent cellulose provided by the application, and the fluorescent cellulose shows AIE characteristics and reversible acid-base discoloration performance, has low cytotoxicity and high fluorescence stability. The fluorescent cellulose can be used not only for acid-base gas detection, but also has potential application value in biological cell imaging agents.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer, in particular to a fluorescent cellulose, a preparation method thereof, a fiber membrane and an application thereof. BACKGROUND

[0002] With the rapid development of industrialization, various toxic and harmful gases and polluting dust are discharged into the atmosphere, which has caused great harm to human beings and the environment. Among them, the harm of acid-base waste gas is particularly serious, which is produced in many industries. Severely volatile gases such as hydrochloric acid and ammonia have been a global environmental problem, so daily monitoring of acid-base gas is very important.

[0003] However, many such sensors are complex to operate and expensive, and have high cytotoxicity, which limits their effective implementation and development.

[0004] Therefore, it is urgent to develop a kind of gas sensing material with low cytotoxicity, high sensitivity and cycle stability. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the first aspect of the present application provides a fluorescent cellulose, which has acid-base gas response, high sensitivity and low cytotoxicity.

[0006] The second aspect of the present application also provides a preparation method of the fluorescent cellulose

[0007] The third aspect of the present application also provides a fiber membrane.

[0008] The fourth aspect of the present application also provides an application of the fluorescent cellulose or the fiber membrane.

[0009] The fluorescent cellulose provided by the first aspect of the present application has a structural formula shown in formula I:

[0010]

[0011] wherein n is 600-1000;

[0012] R1 and R2 are independently selected from H or

[0013] The fluorescent cellulose according to the embodiment of the present application has at least the following beneficial effects:

[0014] The fluorescent cellulose provided by this invention exhibits AIE properties and reversible acid-base color change; it also possesses low cytotoxicity, high fluorescence stability, and a low CMC value (the lower the CMC value, the more stable it is in highly diluted solutions). It can be used not only for the detection of acid and base gases but also has potential applications as a biological cell imaging agent.

[0015] The method for preparing fluorescent cellulose according to a second aspect embodiment of the present invention includes the following steps:

[0016] S1. The dried microcrystalline cellulose, 1-allyl-3-methylimidazolium chloride (AMIMCl) and tert-butyl acetoacetate are reacted to obtain intermediate 1.

[0017] S2. Intermediate 1, DMSO, magnesium chloride, acetic acid, 4-(1,2,2-triphenylvinyl)benzaldehyde and urea are reacted, and then post-treated to obtain fluorescent cellulose.

[0018] The structural formula of intermediate 1 is as follows:

[0019] R3 and R4 are independently selected from H,

[0020] According to some embodiments of the present invention, in step S1, the temperature of the reaction is 90–130°C.

[0021] According to some embodiments of the present invention, in step S1, the reaction time is 6 to 10 hours.

[0022] According to some embodiments of the present invention, in step S2, the temperature of the reaction is 70–100°C.

[0023] According to some embodiments of the present invention, in step S2, the reaction time is 6 to 10 hours.

[0024] According to some embodiments of the present invention, in step S2, the molar ratio of intermediate 1, magnesium chloride, 4-(1,2,2-triphenylvinyl)benzaldehyde and urea is 1:(0.2-0.4):(1.2-2):(1.5-2).

[0025] A third aspect of the present invention provides a fiber membrane, wherein the fluorescent cellulose described above is prepared into a fiber membrane using electrospinning technology.

[0026] According to some embodiments of the present invention, the electrospinning at least satisfies the following conditions:

[0027] i. Flow rate 0.5–1.5 mL / h;

[0028] ii. Spinning voltage 15~20kV;

[0029] iii Working distance: 10-20cm.

[0030] According to some embodiments of the present invention, the preparation steps of the fiber membrane are as follows:

[0031] S3. Mix the fluorescent cellulose, cellulose acetate and solvent described above to obtain an electrospinning solution;

[0032] S4. The electrospinning solution is used to prepare a fiber membrane by electrospinning.

[0033] According to some embodiments of the present invention, the concentration of the electrospinning solution is 10% to 15%.

[0034] According to some embodiments of the present invention, the solvent is a mixture of DMF and DCM, wherein the volume ratio of the two is 1:(1 to 3).

[0035] According to some embodiments of the present invention, the mass ratio of fluorescent cellulose to cellulose acetate is 1:(1.5-3).

[0036] The fourth aspect of the present invention provides the use of the fluorescent cellulose described above; or the fiber membrane described above in acid-base gas responsive sensors or biological cell imaging agents.

[0037] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0039] Figure 1 This is the 1H NMR spectrum of the fluorescent cellulose prepared in Example 1 of this invention;

[0040] Figure 2 This is the infrared spectrum of the fluorescent cellulose prepared according to Embodiment 1 of the present invention;

[0041] Figure 3 This is the absorption and emission spectrum of the fluorescent cellulose prepared in Embodiment 1 of the present invention in water / tetrahydrofuran mixed solutions with different water contents;

[0042] Figure 4 These are SEM and TEM images of FPNs formed from fluorescent cellulose in Example 1 of this invention;

[0043] Figure 5(A) is the PL spectrum of fluorescent cellulose FPNs at different concentrations in water, with an excitation wavelength of 365 nm; (B) is a graph showing the logarithmic relationship between PL intensity and TPE-CDHPM concentration.

[0044] Figure 6 This is a fluorescence stability graph of the fluorescent cellulose FPNs of Example 1 of the present invention under continuous irradiation with a 365nm ultraviolet lamp for 0-120 min.

[0045] Figure 7 CLSM images of MDA-MB-231 and L-02 cells stained with fluorescent cellulose FPNs and cell viability images after incubation with different concentrations of TPE-CDHPM FPNs, respectively. (A, E) 405nm excitation; (B) Overlay of images A and C; (C) Bright field; (D) MDA-MB-231 cell viability images after incubation with different concentrations of TPE-CDHPM FPNs; (F) Overlay of images E and G; (G) Bright field; (H) L-02 cell viability images after incubation with different concentrations of TPE-CDHPM FPNs.

[0046] Figure 8 (A) is the PL spectrum and fluorescence image of fluorescent cellulose powder under external stimulation; (B) is the SEM image of the fiber membrane prepared in Example 2; (C) is the PL spectrum and fluorescence image of the fiber membrane under external stimulation. Detailed Implementation

[0047] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0048] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0049] Example 1

[0050] Example 1 provides a fluorescent cellulose, the reaction equation and preparation method of which are as follows:

[0051]

[0052] S1. Before use, microcrystalline cellulose (MCC) was dried in a vacuum oven at 80°C for 12 hours. 2.0 g of microcrystalline cellulose and 38.0 g of AMIMCl were added to a 250 mL three-necked flask and reacted at 95°C with mechanical stirring for 1.5 hours to completely dissolve the MCC and prepare a 5 wt% cellulose solution. The temperature was raised to 110°C, and t-BAA (19.5 g, 123.4 mmol) was added dropwise under nitrogen protection. The reaction was carried out for 8 hours to obtain a homogeneous brown solution. The solution was cooled to room temperature, and the product was precipitated with methanol, washed with methanol, and then freeze-dried for 48 hours to obtain intermediate 1 (labeled as CAA).

[0053] S2. Intermediate 1 (1.0 g, DS = 0.84) and DMSO (20 mL) were added to a 250 mL three-necked flask. The mixture was mechanically stirred at 50 °C for 1 h to completely dissolve Intermediate 1, resulting in a 5 wt% homogeneous cellulose derivative solution. The reaction temperature was increased to 100 °C, and MgCl2 (0.2 times the molar amount of Intermediate 1) and 20% glacial acetic acid were added to the three-necked flask. After stirring for 10 min, 1.2 molar amounts of 4-(1,2,2-triphenylvinyl)benzaldehyde and 1.5 molar amounts of urea were added under mechanical stirring at 80 °C. After reacting for 8 h, a yellow homogeneous solution was obtained. Methanol was used as a precipitant, and the solution was thoroughly washed with methanol by Soxhlet extraction. The solution was then freeze-dried for 48 h to obtain fluorescent cellulose (labeled as TPE-CDHPM).

[0054] Structural confirmation: The product was subjected to proton NMR and infrared spectroscopy, and the data are shown in the table below. Figure 1 and Figure 2 . Figure 1 In the study, proton NMR spectra of intermediate 1 and fluorescent cellulose were obtained, and the results were analyzed by... 1 ¹H NMR confirmed the successful synthesis of TPE-CDHPM. The chemical shifts of 2.9–5.5 ppm corresponded to hydrogen atoms in the cellulose backbone, and the characteristic peak at 2.18 ppm was the hydrogen atom on the methyl group of the acetoacetic acid group. Through the Biginelli reaction, the integrated area at this point decreased, and new chemical shifts appeared: 6.5–7.7 ppm and 9.08 ppm were the characteristic peaks of hydrogen atoms on the secondary amines of tetraphenylethylene and dihydropyrimidine-2(H) ketones, respectively. This indicates that under these conditions, cellulose acetoacetate underwent a Biginelli reaction with bio-based aldehydes and amines to generate cellulose dihydropyrimidine-2(H) ketone compounds.

[0055] Figure 2 Infrared spectra of microcrystalline cellulose, intermediate 1, and fluorescent cellulose were obtained, and FT-IR spectroscopy also confirmed the successful synthesis of TPE-CDHPM. Comparing microcrystalline cellulose and cellulose acetoacetate, the infrared spectrum of TPE-CDHPM after the Biginelli reaction shows a range of 1714-1748 cm⁻¹.-1 The C=O stretching vibration peak shifted to 1640-1706 cm⁻¹ -1 The stretching vibration peak was significantly weakened, and the absorption wavelength of the C=O group of the ketone carbonyl group showed a red shift after derivatization. Furthermore, at 1000... -1 The following spectra show the C=H of the benzene ring, plus the CN of the secondary amine at 1442-1492 cm⁻¹. -1 The corresponding functional groups in the product structure can be matched one-to-one with those in the infrared spectrum, confirming that cellulose acetoacetate has undergone derivatization.

[0056] Example 2

[0057] Example 2 provides a fiber membrane, the steps of which are as follows:

[0058] S100, Weigh 0.5g of fluorescent cellulose prepared in Example 1 and 1g of cellulose acetate and dissolve them in 8.5g of DMF / DCM (v / v = 1 / 2) mixed solution to prepare electrospinning solution;

[0059] S200. The above electrospinning solution was loaded into a 10 mL syringe. The spinning voltage was 17 kV, the working distance was 13 cm, and a grounded collector was used with silicone paper. The solution flow rate was 1 mL / h. Fiber membranes were prepared at room temperature using an E-05 electrospinning machine (Foshan Light Industry Company).

[0060] Performance testing

[0061] AIE Test: A certain amount of the fluorescent cellulose dihydropyrimidine-2(H)one sample prepared in Example 1 was mixed with tetrahydrofuran to prepare a stock solution with a sample concentration of 0.25 mg / mL. Ten test tubes were numbered 0-9. Under ultrasonic vibration, 1 mL of the stock solution was added to each test tube, and then different amounts of ultrapure water were added according to the different numbers. Test tube 0 was prepared with 0 mL of water and 9 mL of tetrahydrofuran to prepare 10 mL of polymer dispersion, test tube 1 was prepared with 1 mL of water and 8 mL of tetrahydrofuran to prepare 10 mL of polymer dispersion, and so on, for a total of ten groups. Fluorescence spectroscopy and ultraviolet-visible spectroscopy were performed on the ten groups of polymer dispersions.

[0062] The results are as follows Figure 3As shown, 3A is the fluorescence emission spectrum; 3B is the UV-Vis absorption spectrum. The UV-Vis spectrum shows almost no change when the water content of the solution is below 80%. However, when the volume content of added water increases to 80%, the absorption intensity increases significantly across the entire wavelength range tested. Furthermore, the UV-Vis spectrum of the compound exhibits severe tailing in the long-wavelength direction. This is due to the Mie effect, caused by the scattering of incident UV light by fluorescent polymer nanoparticles (FPNs) formed in the solution. In other words, when the volume content of water increases to above 80%, the compound molecules form nano-aggregates in the solution. Meanwhile, the fluorescence spectrum shows that the fluorescent cellulose prepared in Example 1 hardly emits light in tetrahydrofuran solution, and its fluorescence intensity changes very little. However, when the added water content increases to 80%, the fluorescence intensity of the solution begins to increase; when the water content increases to 90%, it is 22 times stronger than in pure tetrahydrofuran. It can be seen that the abrupt change in fluorescence emission intensity is consistent with the abrupt change in UV-Vis absorption intensity. These results demonstrate that it possesses AIE performance.

[0063] Furthermore, the size and morphology of FPNs were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 4 The results showed that the average diameter of the fluorescent cellulose-formed FPNs in a 90% water / THF mixed solvent was between 40 and 200 nm, exhibiting a smooth, spherical nanoparticle structure. Figure 4 A). TEM images show that FPNs are hollow. Figure 4 (B) This is due to the hydrophobic AIE segments being in the inner layer and the hydrophilic cellulose segments in the outer layer. TEM samples were obtained by dropping a dispersed FPNs solution onto a copper mesh.

[0064] Furthermore, the CMC value of fluorescent cellulose was investigated, starting from 1.0 × 10⁻⁶. -5 mg mL -1 Up to 0.1 mg / mL -1 PL spectroscopy was performed on fluorescent cellulose FPNs at different concentrations. Figure 5 A). As the concentration of FPNs increased, the fluorescence intensity gradually increased. Based on the inflection point of the curve between fluorescence intensity and the logarithm of the fluorescent cellulose FPNs concentration, the CMC value of the fluorescent cellulose FPNs was quantitatively determined. The results showed that the CMC value of the fluorescent cellulose FPNs was as low as 0.006 mg / mL. -1 ( Figure 5 B). Low CMC values ​​of FPNs can improve their stability in highly diluted solutions and expand their application range.

[0065] Furthermore, the fluorescence stability of fluorescent cellulose FPNs in water was investigated. The long-term fluorescence stability (PL) of TPE-CDHPM FPNs was studied by irradiation with a 365 nm UV lamp for 10-120 min. The results showed that the PL intensity of the FPNs did not change significantly after prolonged UV irradiation. Figure 6 This indicates that TPE-CDHPM FPNs have good photostability, and this superior photostability can be used to further study the application of fluorescent cellulose in cell imaging.

[0066] Cytotoxicity evaluation:

[0067] The prepared fluorescent cellulose FPNs exhibited good photostability and excellent fluorescence emission, showing promising potential for bioimaging. Before applying them to cell imaging, the cytotoxicity of the fluorescent cellulose FPNs was evaluated using two cell lines: MDA-MB-231 (breast cancer cells) and L-02 (normal human hepatocytes). Different doses of fluorescent cellulose FPNs (2.5, 5, 10, 20, 40, 80, 160 μg / mL) were used. -1 The two cell types were treated separately, and the cytotoxicity of FPNs was determined using the CCK-8 assay. Figure 7 D, Figure 7 H), cytotoxicity assays confirmed that cells maintained high viability after 24 hours of incubation with different concentrations of fluorescent cellulose (FPNs), and increasing the concentration of FPNs had almost no effect on cell viability, even at 160 μg / mL. -1 At the same concentration, cell viability was observed in both MDA-MB-231 and L-02 cells at 0 μg / mL. -1 There was almost no change compared to the previous one.

[0068] This high cell viability further facilitated the use of fluorescent cellulose FPNs for cell imaging, exploring their applications in bioimaging. Therefore, MDA-MB-231 and L-02 cells incubated with TPE-CDHPM FPNs were observed using laser scanning confocal microscopy (CLSM) and imaged in fluorescence mode. After incubation with TPE-CDHPM FPNs, it was found that the FPNs penetrated the cell interior, exhibiting significant green fluorescence, particularly in the cytoplasm. Figure 7 AC, 7E-G). Therefore, the TPE-CDHPM FPNs prepared in this invention have potential application value in biological cell imaging agents.

[0069] Acid-base gas response performance experiment:

[0070] Acid-induced fluorescence color change performance: The fluorescent cellulose prepared in Example 1 was placed in a sealed container filled with HCl vapor and left for a period of time (more than 4 hours). The resulting sample was labeled TPE-CDHPM-OH. Half of the resulting sample was placed in a sealed container filled with NH3 and left for a period of time (more than 4 hours), and the resulting sample was labeled TPE-CDHPM-OHN. Photographs of the three states of the sample were taken under 365nm ultraviolet light irradiation, and then their fluorescence spectra were obtained by timely fluorescence spectroscopy.

[0071] like Figure 8 As shown in Figure A, (A) shows the photoluminescence (PL) spectrum and fluorescence photograph of fluorescent cellulose powder under external stimuli; (O is the initial TPE-CDHPM powder, O-HCl is the sample obtained after fumigating the fluorescent cellulose with HCl vapor for 1 hour, and O-HCl-NH3 is the sample obtained after fumigating O-HCl with NH3 vapor for 30 minutes). Fluorescent cellulose TPE-CDHPM(O) itself exhibits fluorescence. The fluorescence of TPE-CDHPM(O-HCl) was quenched after acid fumigation. However, placing O-HCl in a sealed container containing NH3 vapor for a second fumigation restored the fluorescence color of TPE-CDHPM(O-HCl-NH3) to yellow. These results demonstrate that it possesses reversible acid-base fluorescence color-changing properties. Figure 8 (B) proves that the prepared membrane is a nanofiber membrane.

[0072] Acid-induced fluorescence color change properties of fiber membranes: To verify whether the fiber membrane (m) with 0.1 wt% added still exhibits acid-base stimulation response characteristics, an acid-base induced color change experiment was conducted. Figure 8 C represents the PL spectrum and fluorescence image of the fiber membrane under external stimulation (m is the initial fiber membrane, m-HCl is the sample obtained after fumigating m with HCl vapor for 1 h, and m-HCl-NH3 is the sample obtained after fumigating m-HCl with NH3 vapor for 30 min). The fluorescence intensity of the acid-fumigated fiber membrane (m-HCl) decreased to 4.25 times its original value. Subsequently, m-HCl was placed in a sealed container containing NH3 vapor for a second fumigation, which increased the fluorescence intensity by 2 times and the fluorescence color returned to its original yellow-green. The experimental results show that the micro / nanofiber membrane TPE-CDHPM-m obtained by electrospinning the fluorescent cellulose sample synthesized in this invention and cellulose acetate mixture exhibits the same reversible acid-induced fluorescence color change properties as the synthesized compound sample itself. The prepared fiber membrane also has potential application value in acid detection sensors.

[0073] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A fluorescent cellulose, characterized in that, It has the structural formula shown in Equation I: ； Where n is 600~1000; R1 and R2 are independently selected from H or .

2. The method for preparing fluorescent cellulose according to claim 1, characterized in that, Includes the following steps: S1. The dried microcrystalline cellulose, 1-allyl-3-methylimidazolium chloride and tert-butyl acetoacetate are reacted to obtain intermediate 1. S2. Intermediate 1, DMSO, magnesium chloride, acetic acid, 4-(1,2,2-triphenylvinyl)benzaldehyde and urea are reacted, and then post-treated to obtain fluorescent cellulose. The molar ratio of intermediate 1, magnesium chloride, 4-(1,2,2-triphenylvinyl)benzaldehyde, and urea is 1:(0.2~0.4):(1.2~2):(1.5~2). The structural formula of intermediate 1 is as follows: R3 and R4 are independently selected from H, .

3. The preparation method according to claim 2, characterized in that, In step S1, the reaction temperature is 90~130℃.

4. The preparation method according to claim 2, characterized in that, In step S1, the reaction time is 6-10 hours.

5. The preparation method according to claim 2, characterized in that, In step S2, the reaction temperature is 70~100℃.

6. The preparation method according to claim 2, characterized in that, In step S2, the reaction time is 6-10 hours.

7. A fiber membrane, characterized in that, The fluorescent cellulose described in claim 1 is prepared into a fiber membrane using electrospinning technology.

8. The fiber membrane according to claim 7, characterized in that, The electrospinning shall at least satisfy the following conditions: i. Flow rate 0.5~1.5 mL / h; ii. Spinning voltage 15~20 kV; iii Working distance 10~20 cm.

9. The use of the fluorescent cellulose of claim 1; or the fiber membrane of any one of claims 7-8 in an acid-base gas responsive sensor or a biological cell imaging agent.

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