Preparation method of high-precision developing antibacterial intelligent film developed based on alizarin

Abstract

The invention discloses a preparation method of a high-precision developing antibacterial intelligent film developed based on alizarin. The preparation method of the intelligent film comprises the following steps: dissolving alizarin in an ethanol solution to obtain an alizarin ethanol solution; adding polyvinylpyrrolidone and ethyl cellulose, and uniformly mixing to obtain a shell spinning solution; mixing cinnamyl aldehyde and polyoxyethylene with water and ethanol to obtain a core layer spinning solution; and preparing the film by using a coaxial electrostatic spinning technology. According to the invention, the shell layer is a film with moderate hydrophobicity obtained by mixing a hydrophilic material and a hydrophobic material, and alizarin is added as a color developing substance, so that an obvious color developing effect is realized. Cinnamyl aldehyde is added into a core layer solution, so that the film has antibacterial and antioxidant functions; the fibers with the core-shell structure are prepared through the coaxial electrostatic spinning technology, cinnamyl aldehyde can be wrapped, release of cinnamyl aldehyde is slowed down, and the antibacterial effect of the intelligent film is enhanced.

Description

Technical Field

[0001] This invention relates to the field of meat preservation technology, specifically to a method for preparing a high-precision colorimetric antibacterial smart film based on alizarin. Background Technology

[0002] As a mainstream meat product, chilled pork is susceptible to contamination by microorganisms such as E. coli and Staphylococcus aureus during processing, storage, and transportation at 0-4℃. This contamination leads to meat spoilage, shortened shelf life, and threatens food safety. Traditional preservation technologies have limitations, including limited antibacterial effects and the inability to provide direct feedback on quality. The emergence of smart packaging has effectively alleviated these issues. Smart color-changing packaging can visually indicate food freshness through color changes. However, current smart color-changing technologies still suffer from insensitive color development and the easy oxidation of color-developing substances. Therefore, a stable, color-sensitive, highly accurate smart film with antibacterial properties is crucial for extending the shelf life of pork and enabling consumers to easily assess its freshness. Summary of the Invention

[0003] To address the problems existing in the background art, the present invention provides a method for preparing a high-precision colorimetric antibacterial smart film based on alizarin.

[0004] The technical solution adopted in this invention includes the following steps:

[0005] (1) At room temperature, alizarin (Az) was dissolved in an ethanol solution and mixed on a magnetic stirrer for 24 hours to obtain an alizarin ethanol solution.

[0006] (2) At room temperature, use a 0.45um needle filter to remove insoluble impurities;

[0007] (3) At room temperature, polyvinylpyrrolidone (PVP) and ethyl cellulose (EC) were added to the alizarin ethanol solution obtained in (2) in a ratio of 3:2, and stirred in a magnetic stirrer for 24 hours to obtain an 8 wt% shell spinning solution.

[0008] (4) At room temperature, polyethylene oxide (PEO) was added to an 80 v / v% ethanol solution, and cinnamaldehyde was added as an antibacterial substance. The solution was then placed on a magnetic stirrer and stirred for 24 h to obtain an 8 wt% core spinning solution.

[0009] (5) Prepare a thin film using coaxial electrospinning technology and collect the film on a metal plate covered with silicone paper.

[0010] The ethanol used in step (1) is pure ethanol.

[0011] The amount of Az added in step (1) is 3 wt% of the solute in step (3).

[0012] The amount of CIN added in step (4) is 0-10wt%.

[0013] In step (5), the technical conditions for coaxial electrospinning are: spinning voltage 10kV, spinning distance 15cm, spinning speed of both shell and core solutions 0.8ml / h, and spinning time 4h.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] (1) Green and safe materials: All materials used in this invention are harmless substances and no toxic or harmful reagents are used for dissolution.

[0016] (2) Excellent pH color development performance: The present invention exhibits obvious color changes between pH 6 and 10, and can achieve high-precision color development to one decimal place in the pH 6-7 range.

[0017] (3) Excellent color development performance of ammonia vapor: The present invention can rapidly change color in the ammonia vapor environment, changing from the original light brown to purple. When it leaves the ammonia vapor environment, it can quickly return to the original state, which has the value of repeated use.

[0018] In this invention, coaxial electrospinning technology is used to prepare a film with a core-shell fiber structure. CIN, as an antibacterial substance, is wrapped in the core fiber to achieve antibacterial and preservation effects. Alizarin, as a colorant, is added to the shell solution to obtain a smart film with dual antibacterial and color-developing effects. Attached Figure Description

[0019] Figure 1 The effect of films with different CIN concentrations on fiber morphology and the characterization of coaxial core-shell structure.

[0020] Figure 2 XDR images of films with different CIN concentrations.

[0021] Figure 3 Thermogravimetric analysis (TGA) curves (A) and derivative thermogravimetric analysis (DTG) curves (B) for films with different CIN concentrations.

[0022] Figure 4 The effect of films with different CIN concentrations on water vapor permeability.

[0023] Figure 5 The effect of films with different CIN concentrations on the water contact angle.

[0024] Figure 6 The scavenging rates of DPPH radicals (A) and ABTS radicals (B) of films with different CIN concentrations are shown.

[0025] Figure 7 The color change of the thin film after adding buffer solutions of different pH values.

[0026] Figure 8 The color change of the thin film in an ammonia vapor environment.

[0027] Figure 9 The antibacterial effects (A) and inhibition rate (B) of films with different CIN concentrations against Escherichia coli and Staphylococcus aureus were evaluated. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to specific embodiments.

[0029] Example 1

[0030] Weigh alizarin and mix it with an ethanol solution, then filter the mixture. Add PVP and EC to the Az ethanol solution in a 3:2 ratio and mix thoroughly to obtain a shell solution with a concentration of 8 wt% that has a colorimetric effect.

[0031] PEO was dissolved in an 80% ethanol solution to obtain a spinning solution with a concentration of 8 wt%, which was used as the core layer solution.

[0032] Coaxial electrospinning was carried out under conditions of ambient humidity of about 45%, with the spinning voltage set at 10kV, the spinning distance at 15cm, the core and shell solution feed ratio at 1:1, and the spinning process set at 4 hours.

[0033] Example 2

[0034] Weigh Az and mix it with the ethanol solution, then filter it. Add PVP and EC to the alizarin ethanol solution in a 3:2 ratio and mix well to obtain a shell solution with a concentration of 8wt% that has a colorimetric effect.

[0035] PEO was dissolved in 80% ethanol solution to obtain a spinning solution with a concentration of 8wt%, and 2wt% CIN was added as a core layer solution with antibacterial effect.

[0036] Coaxial electrospinning was carried out under conditions of ambient humidity of about 45%, with the spinning voltage set at 10kV, the spinning distance at 15cm, the core and shell solution propulsion speeds at a ratio of 1:1, and the spinning process set to 4 hours.

[0037] Example 3

[0038] Weigh Az and mix it with the ethanol solution, then filter it. Add PVP and EC to the alizarin ethanol solution in a 3:2 ratio and mix well to obtain a shell solution with a concentration of 8wt% that has a colorimetric effect.

[0039] PEO was dissolved in 80% ethanol solution to obtain a spinning solution with a concentration of 8wt%, and 4wt% CIN was added as a core layer solution with antibacterial effect.

[0040] Coaxial electrospinning was carried out under conditions of ambient humidity of about 45%, with the spinning voltage set at 10kV, the spinning distance at 15cm, the core and shell solution feed ratio at 1:1, and the spinning process set at 4 hours.

[0041] Example 4

[0042] Weigh Az and mix it with the ethanol solution, then filter it. Add PVP and EC to the alizarin ethanol solution in a 3:2 ratio and mix well to obtain a shell solution with a concentration of 8 wt% that has a colorimetric effect.

[0043] PEO was dissolved in 80% ethanol solution to obtain a spinning solution with a concentration of 8wt%, and 6wt% CIN was added as a core layer solution with antibacterial effect.

[0044] Coaxial electrospinning was carried out under conditions of ambient humidity of about 45%, with the spinning voltage set at 10kV, the spinning distance at 15cm, the core and shell solution feed ratio at 1:1, and the spinning process set at 4 hours.

[0045] Example 5

[0046] Weigh Az and mix it with the ethanol solution, then filter it. Add PVP and EC to the alizarin ethanol solution in a 3:2 ratio and mix well to obtain a shell solution with a concentration of 8 wt% that has a colorimetric effect.

[0047] PEO was dissolved in 80% ethanol solution to obtain a spinning solution with a concentration of 8wt%, and 8wt% CIN was added as a core layer solution with antibacterial effect.

[0048] Coaxial electrospinning was carried out under conditions of ambient humidity of about 45%, with the spinning voltage set at 10kV, the spinning distance at 15cm, the core and shell solution feed ratio at 1:1, and the spinning process set at 4 hours.

[0049] Example 6

[0050] Weigh Az and mix it with the ethanol solution, then filter it. Add PVP and EC to the alizarin ethanol solution in a 3:2 ratio and mix well to obtain a shell solution with a concentration of 8 wt% that has a colorimetric effect.

[0051] PEO was dissolved in 80% ethanol solution to obtain a spinning solution with a concentration of 8wt%, and 10wt% CIN was added as a core layer solution with antibacterial effect.

[0052] Coaxial electrospinning was carried out under conditions of ambient humidity of about 45%, with the spinning voltage set at 10kV, the spinning distance at 15cm, the core and shell solution feed ratio at 1:1, and the spinning process set at 4 hours.

[0053] Example 1: The smart thin film samples prepared in Examples 1-6 were characterized.

[0054] 1. Microstructure characterization of film fibers: The microstructure of the intelligent antibacterial colorimetric film was observed by SEM. Fiber morphology and size analysis are shown in [link to relevant documentation]. Figure 1 (af). The images show that the fibers exhibit a uniform, smooth cylindrical structure. As the CIN content increases, the fiber diameter continuously decreases. This is likely because the polar groups in CIN increase the conductivity of the solution, causing the fibers to be drawn thinner by the electric field during spinning. Simultaneously, as the CIN content increases, the surface depressions of the fibers decrease, possibly due to differences in the spinning material. When the CIN content increases to 10%, a large number of disordered, web-like filaments begin to appear. The core reason for this phenomenon is that excessive CIN addition excessively reduces the viscosity of the solution, making the solution unstable and causing breakage during spinning, ultimately forming an irregular web-like filament structure. Figure 1 A distinct core-shell structure was observed in -g and 1-h, with the antibacterial substance containing CIN being uniformly encapsulated in the shell color development solution. This not only provided an antibacterial and sustained-release effect but also enhanced the functionality of the smart membrane.

[0055] 2. XRD analysis was performed using an X-ray polycrystalline diffractometer (Bruker D8 ADVANCE, Germany). The instrument operated at 40 kV and 39 mA. The scan rate was set to 5° / min, and the 2θ range was from 5° to 90°.

[0056] Figure 2 XRD images of smart colorimetric films with PEO and CIN additions ranging from 0-10% are shown. The images reveal a distinct semi-crystalline structure in PEO, characterized by strong characteristic diffraction peaks at 2θ = 19.24 and 2θ = 23.34. These characteristic peaks are also present in films containing different concentrations of CIN, indicating the presence of a partially semi-crystalline structure within the PEO fibers. The weakening of these characteristic peaks with increasing CIN content is likely due to the disruption of some PEO crystals by CIN-like active substances in the solution, reducing its semi-crystalline nature. Simultaneously, weak, broad peaks appear at 2θ = 26.02, 26.84, 35.26, 36.28, and 39.66, suggesting the presence of amorphous structures within PEO, which are not characteristically present in the films.

[0057] 3. Thermal stability analysis was performed using a TG 209 F3 thermogravimetric analyzer. The sample (10 mg) was heated from 30 °C to 600 °C at a rate of 10 °C / min under a nitrogen atmosphere (50 mL / min).

[0058] Thermogravimetric analysis (TGA) and derivative thermogravimetric measurement (DTG) curves of smart colorimetric films with different CIN contents are shown below. Figure 3 As shown, the thermal degradation process of all smart films exhibits two distinct stages. The first stage is from 0 to 300℃, during which the film's weight loss rate is approximately 5%-10%, mainly due to the evaporation of adsorbed water and residual solvents, as well as the loss of volatile substances such as CIN. The second stage is the rapid weight loss stage, generally occurring in the range of 300-400℃. This stage is the core of the weight loss process, during which the film's mass rapidly decreases. This is primarily caused by the thermal decomposition of polyethylene oxide and polyvinylpyrrolidone, as well as the thermal degradation of ethyl cellulose. The thermal degradation of alizarin also falls within this stage. The highest degradation temperature (Tm) of films with different CIN contents can be observed from the DTG graph. With increasing CIN content, the highest degradation temperature of the film shows an increasing trend, which may be because the addition of CIN improves the film's thermal properties, thereby enhancing its thermal stability.

[0059] 4. The tensile strength (TS) and elongation at break (EAB) of the film were determined using a texture analyzer (TA-XT, StableMicro Systems UK). The film was cut to 10 mm × 70 mm before testing. The selected probe was A / SPR. The effective tensile length and test speed were adjusted to 50 mm and 5 mm / s, respectively. The formulas for calculating TS (MPa) and EAB (%) are as follows:

[0060]

[0061] Where Fmax(N) is the maximum force at fracture, W is the width of the film, and L is the thickness of the film. The thickness of the film was measured using a high-precision digital micrometer (Mitutoyo 211-101, Japan; resolution: 1 μm).

[0062]

[0063] Where ΔL (mm) is the elongation of the film at fracture, and L (mm) is the initial length of the film. All films were measured three times.

[0064] The variations in thickness, tensile strength, and elongation at break of the intelligent colorimetric film are shown in Table 1. Films with different CIN contents showed almost no difference in thickness because the spinning time and other factors were strictly controlled during the spinning process to minimize the influence of objective factors on the film's mechanical properties. With increasing CIN content, the tensile strength of the film decreased slightly, possibly due to the thinning of the fibers and the presence of impurities, which reduced the film's tensile strength. Unlike tensile strength, the addition of CIN had a positive effect on the film's elongation at break; increasing the CIN content effectively improved the film's flexibility.

[0065] Table 1

[0066] sample Tensile strength (MPa) Elongation at break (%) Thickness (mm) CIN0 <![CDATA[1.76±0.07 a ]]> <![CDATA[33.66±0.99 f ]]> <![CDATA[0.030±0.002 a ]]> CIN2 <![CDATA[1.73±0.10 b ]]> <![CDATA[42.86±0.21 e ]]> <![CDATA[0.031±0.003 a ]]> CIN4 <![CDATA[1.77±0.06 b ]]> <![CDATA[52.08±2.05 d ]]> <![CDATA[0.032±0.002 a ]]> CIN6 <![CDATA[1.82±0.10 a ]]> <![CDATA[60.06±1.08 c ]]> <![CDATA[0.030±0.003 a ]]> CIN8 <![CDATA[1.79±0.11 a ]]> <![CDATA[65.69±1.34 b ]]> <![CDATA[0.031±0.003 a ]]> CIN10 <![CDATA[1.77±0.11 a ]]> <![CDATA[75.55±2.02 a ]]> <![CDATA[0.030±0.003 a ]]>

[0067] 5. Water Vapor Transmission Rate (WVTR) Measurement: Weigh approximately 2g of CaCl2 and place it in a bottle. Cut a fiber film into a circle matching the bottle opening diameter and fix it at the bottle opening. Place the bottle with the immobilized film in a desiccator, with a supersaturated sodium chloride solution at the bottom. Record the weight change every 24 hours. The results are calculated using the following formula:

[0068]

[0069] In the formula, WVTR is the water vapor transmission rate (g∙m). −2 ∙h −1 Δm is the weight increase of the bottle, A is the area of ​​the thin film disc, and Δt is time.

[0070] WVTR is one of the important indicators for evaluating the performance of packaging barriers. Figure 4 As shown in the figure, the amount of CIN added has little effect on the WVTR of the film, but overall it decreases with increasing CIN content. On the one hand, because electrospun films have high porosity and good air permeability, the addition of a small amount of hydrophobic active material has a negligible impact on the WVTR. On the other hand, the added CIN interacts with the core layer material PEO through hydrogen bonds, making the film structure more compact, reducing its affinity for water, and ultimately enhancing the barrier properties of the film.

[0071] 6. The surface hydrophilicity of the nanofiber film was characterized by measuring the water contact angle (WCA) at room temperature using the sitting drop method. The film was fixed on a glass slide for titration, with the droplet size controlled at 5 μL. The droplet was allowed to equilibrate for 3 minutes before measurement. Each sample was tested three times to ensure authenticity.

[0072] WCA is a key indicator for evaluating the hydrophobicity of thin films. When the WCA of a thin film is less than 90°, it is generally considered to be hydrophilic, and vice versa. Figure 5The WCA of films with different CIN contents is described in detail. Overall, all films are slightly hydrophilic, but as the CIN content increases, the WCA of the films gradually increases, eventually approaching hydrophobicity. CIN, as an aldehyde organic compound, is inherently hydrophobic. Adding this substance to the film can, to some extent, prevent the diffusion of water, thereby increasing the hydrophobicity of the film.

[0073] 7. Antioxidant Activity Test: A certain mass of nanofiber film was immersed in 10 mL of methanol solution, and measurements were taken every 24 hours. To evaluate the DPPH free radical scavenging activity, 100 μL of the immersion solution was collected and mixed with 3.9 mL of DPPH methanol solution. The resulting mixture was incubated in the dark for 2 hours, and its absorbance was measured at 517 nm.

[0074] The radical scavenging activity of ABTS was evaluated by mixing equal volumes of 7.4 mM ABTS stock solution and 2.6 mM potassium persulfate solution. The mixture was allowed to react in the dark at room temperature for 16 hours. The stock solution was then diluted until its absorbance reached the target value of 0.70 ± 0.05 at 734 nm. Next, 100 μL of the soaking solution was mixed with 3.9 mL of the diluted ABTS reaction solution. After reacting at room temperature for 6 min, the absorbance of the final solution was measured at 734 nm. The radical scavenging rate was calculated using the following formula:

[0075]

[0076] CIN has strong antioxidant properties. Figure 6 The DPPH and ABTS radical scavenging rates of the smart colorimetric membrane are shown in the figure. As can be seen from the figure, the DPPH and ABTS radical scavenging rates of the membrane significantly increase with increasing CIN content. Specifically, the DPPH radical scavenging rate increases from 35.64 to 52.20, while the ABTS radical scavenging rate increases from 14.97 to 51.08. This is because CIN contains a large number of unpaired electrons, which can provide electrons and hydrogen to free radicals, ultimately achieving the effect of removing reactive oxygen species.

[0077] 8. Measurement of pH color response of the membrane: Prepare buffer solutions with pH 3-10, and pH 6.2, 6.4, 6.6, and 6.8 respectively. Cut the membrane to a fixed size, take a certain amount of pH buffer solution and drop it onto the membrane. After the buffer solution has fully reacted with the membrane and dried, use a colorimeter to measure the L, a, and b values ​​of the membrane at different pH values ​​and calculate the color difference.

[0078] Figure 7The results demonstrate that the intelligent membrane exhibits excellent color development performance in buffer solutions with different pH values, especially demonstrating high-precision color development in the pH 6-7 range. Table 2 shows that at pH 6, the membrane's L value is 68.44±0.23b, a value is 5.57±0.18f, b value is 62.80±0.65d, and the total color difference ∆E is 68.62±0.51c. In the pH 6.2-6.8 range, the color parameters show regular changes with small fluctuations. L steadily decreases from 60.73±0.03d to 54.55±0.18e, a remains within the 4.37-7.94 range, and b decreases gradually. The total color difference ∆E accurately distinguishes different pH values. The intelligent membrane exhibits strong color parameter stability and good repeatability; high color development accuracy in the pH 6-7 range, accurately responding to minute pH changes; and excellent total color difference discrimination, intuitively reflecting pH differences. In addition, it exhibits a clear colorimetric response across the entire pH range (3-10), with discernible color change patterns, combining wide adaptability with high precision, making it highly valuable for precise pH detection.

[0079] Table 2

[0080] pH L* a* b* ∆E 3 <![CDATA[79.14±0.59 a ]]> <![CDATA[6.25±0.59 e ]]> <![CDATA[82.53±0.36 a ]]> <![CDATA[84.07±0.50 a ]]> 4 <![CDATA[78.57±0.79 a ]]> <![CDATA[5.05±0.08 gh ]]> <![CDATA[75.76±0.99 b ]]> <![CDATA[77.58±0.88 b ]]> 5 <![CDATA[78.25±0.64 a ]]> <![CDATA[1.99±0.02 j ]]> <![CDATA[64.54±0.74 c ]]> <![CDATA[66.66±0.55 d ]]> 6 <![CDATA[68.44±0.23 b ]]> <![CDATA[5.57±0.18 f ]]> <![CDATA[62.80±0.65 d ]]> <![CDATA[68.62±0.51 c ]]> 6.2 <![CDATA[60.73±0.03 d ]]> <![CDATA[7.94±0.06 d ]]> <![CDATA[57.17±0.84 e ]]> <![CDATA[67.56±0.69 cd ]]> 6.4 <![CDATA[62.31±0.76 c ]]> <![CDATA[4.37±0.41 i ]]> <![CDATA[49.45±0.67 f ]]> <![CDATA[59.93±0.83 e ]]> 6.6 <![CDATA[59.71±0.93 d ]]> <![CDATA[4.80±0.51 hi ]]> <![CDATA[42.30±0.13 g ]]> <![CDATA[55.97±0.75 f ]]> 6.8 <![CDATA[54.55±0.18 e ]]> <![CDATA[5.48±0.19 fg ]]> <![CDATA[22.80±0.17 h ]]> <![CDATA[47.92±0.08 h ]]> 7 <![CDATA[47.59±0.83 f ]]> <![CDATA[5.61±0.10 f ]]> <![CDATA[23.47±0.28 h ]]> <![CDATA[54.42±0.63 g ]]> 8 <![CDATA[41.05±1.33 h ]]> <![CDATA[11.32±0.09 c ]]> <![CDATA[-14.85±0.32 j ]]> <![CDATA[58.74±1.32 e ]]> 9 <![CDATA[42.59±0.86 g ]]> <![CDATA[12.44±0.30 b ]]> <![CDATA[-10.56±0.61 i ]]> <![CDATA[56.55±0.98 f ]]> 10 <![CDATA[36.08±0.57 i ]]> <![CDATA[13.0±0.14 a ]]> <![CDATA[-24.84±0.26 k ]]> <![CDATA[66.91±0.63 d ]]>

[0081] 9. Measurement of the color response of the membrane to ammonia vapor: Prepare 1 mol / L ammonia solution, measure 5 ml and place it in a petri dish. Fix the membrane inside the lid of the petri dish and photograph the color change of the membrane before and after the reaction. Repeat the measurement three times to verify the reusability of the membrane and the authenticity of the color development.

[0082] This smart thin film exhibits highly efficient and reversible color response characteristics to ammonia vapor, such as Figure 8 As shown, in an ammonia vapor environment, its color changes rapidly, demonstrating its core advantage of fast response. It can quickly detect the presence of ammonia vapor and the resulting color change, from light brown to purple. After leaving the ammonia vapor environment, the membrane can return to its initial color, indicating good reversibility and allowing it to be reused for ammonia vapor detection. This combination of rapid response and reversible recovery ensures the timeliness of ammonia vapor detection and enhances the reusability of the colorimetric membrane, avoiding resource waste from single use.

[0083] 10. Measurement of antibacterial activity of the membrane: The inhibitory effect of the intelligent antibacterial chromogenic membrane on *Escherichia coli* and *Staphylococcus aureus* was determined using the plate count method (Ling et al., 2024). Two generations of the two strains were pre-cultured, and the second-generation culture was diluted 10-fold. 10 mg of the porous composite pad sample was incubated with the diluted *E. coli* and *Staphylococcus aureus* solutions at 37°C for 24 h. 200 μL of the mixture was added to liquid culture medium and maintained at 37°C for 24 h. Bacterial counts were then recorded to calculate the inhibition rate of the two bacteria.

[0084] from Figure 9 It is clearly evident that the amount of CIN added is significantly positively correlated with the antibacterial rate of the intelligent colorimetric antibacterial membrane, and the membrane's overall inhibitory effect on Staphylococcus aureus is better than that on Escherichia coli. In the CIN2 group, the membrane's inhibition rate against Staphylococcus aureus is approximately 50%, while that against Escherichia coli is only about 5%, showing a significant difference in antibacterial effect. As the amount of CIN added increases to CIN4, CIN6, and CIN8, the inhibition rates of both bacteria gradually increase, with the inhibition rate against Staphylococcus aureus approaching 95%~100%, and the inhibition rate against Escherichia coli increasing from approximately 13% to 80%. In the CIN10 group, the inhibition rate against Staphylococcus aureus reaches 100%, and the inhibition rate against Escherichia coli is also close to 100%. This indicates that low concentrations of CIN can produce good inhibition against Staphylococcus aureus, while Escherichia coli has relatively low sensitivity to CIN, requiring higher addition amounts to achieve efficient antibacterial activity. This also confirms that CIN, as an antibacterial additive, can effectively improve the antibacterial performance of polymer membranes, and that the antibacterial effect is species-specific.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-precision colorimetric antibacterial smart film based on alizarin, characterized in that... Follow these steps: (1) At room temperature, alizarin (Az) was dissolved in an ethanol solution and mixed on a magnetic stirrer for 24 hours to obtain an alizarin ethanol solution; (2) At room temperature, use a 0.45um needle filter to remove insoluble impurities; (3) At room temperature, polyvinylpyrrolidone (PVP) and ethyl cellulose (EC) were added to the alizarin ethanol solution obtained in (2) in a ratio of 3:2, and stirred in a magnetic stirrer for 24 hours to obtain an 8 wt% shell spinning solution. (4) At room temperature, polyethylene oxide (PEO) was added to an 80 v / v ethanol solution, and cinnamaldehyde was added as an antibacterial substance. The solution was then stirred on a magnetic stirrer for 24 h to obtain an 8 wt% core spinning solution. (5) Prepare a thin film using coaxial electrospinning technology and collect the film on a metal plate covered with silicone paper.

2. The high-precision colorimetric antibacterial intelligent film based on alizarin according to claim 1, characterized in that, In step (1), the content of alizarin is 3% of the total mass of polyvinylpyrrolidone and ethyl cellulose. After the alizarin is dissolved, a 0.45 μm needle filter is used to remove insoluble impurities.

3. The method for preparing a high-precision colorimetric antibacterial smart film based on alizarin according to claim 1, characterized in that, In step (3), the content of polyethylene oxide in the core layer solution is 8 wt%, and the amount of cinnamaldehyde added is 0-10 wt%.

4. The method for preparing a high-precision colorimetric antibacterial smart film based on alizarin according to claim 1, characterized in that, The coaxial electrospinning conditions in step (3) are as follows: spinning voltage is 10kV, shell solution flow rate is 0.8mL / h, core solution flow rate is 0.8mL / h, and time is 4h.

5. The preparation method according to any one of claims 1-4 produces a high-precision colorimetric antibacterial smart film based on alizarin.

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