A degradable sampling swab based on natural polymer and a preparation method thereof

Abstract

The application provides a sampling swab based on a natural polymer and a preparation method thereof, wherein chitosan and citric acid are mixed in water at high temperature to obtain a hot solution, the high-temperature environment is 70-90 DEG C; carboxymethyl cellulose is stirred in the hot solution to obtain a transparent paste; bubbles in the transparent paste are discharged, and the transparent paste is extruded into a citric acid solution to soak to obtain a strip-shaped gel; the strip-shaped gel is washed with water and then freeze-dried to obtain a rod-shaped material, and the rod-shaped material is cut to obtain the sampling swab; the sampling swab is prepared by using a biodegradable polymer, has good water absorption performance, and has mechanical strength meeting sampling requirements; after sampling is completed, the sampling swab can be degraded by means of alkali treatment or acid treatment, so that solid waste is avoided, and pollution to the environment is reduced.

Description

Technical Field

[0001] This invention relates to the field of swab preparation, and in particular to a biodegradable sampling swab based on natural polymers and its preparation method. Background Technology

[0002] The primary purpose of swabs is for collecting clinical laboratory specimens. Depending on the intended clinical sample, they can be categorized as nasal swabs, throat swabs, and swabs for vaginal, cervical, anal, and urethral collection. Swabs mainly consist of two parts: the swab swab and the swab head. The swab swab is primarily made of three materials: polypropylene (PP), polystyrene (PS), and acrylonitrile-butadiene-styrene copolymer (ABS). Currently, flocked swabs (made of nylon fibers) are widely used for swab heads, while some countries use lower-cost cotton swabs.

[0003] After collecting samples, swabs become medical waste. Currently, high-temperature incineration or alternative technologies such as high-temperature pyrolysis and medium-temperature microwave technology are commonly used to process the swabs. While these three methods can completely kill pathogens and decompose most organic matter, they produce toxic substances such as furans and dioxins, causing environmental pollution. Furthermore, the cost of such incinerators is prohibitively high; it is estimated that building an incinerator capable of processing 1 million tons of waste annually would cost between $190 million and $1.2 billion. Compared to other waste disposal methods, waste incineration has the highest capital and operating expenses, and incinerators require continuous equipment upgrades to comply with emission regulations. Landfilling is another option, but it not only occupies land but also incurs significant economic costs. Moreover, landfilling does not degrade plastics.

[0004] This invention aims to develop a biodegradable sampling swab based on natural polymers. This sampling swab, composed of natural polymers, can be completely degraded after sampling and testing through methods such as heating, acid treatment, or alkali treatment, effectively avoiding the generation of solid medical waste. This strategy aligns with the concept of low-carbon and green development and expands the application of natural polymers in the biomedical field. Summary of the Invention

[0005] This invention provides a biodegradable sampling swab based on natural polymers and its preparation method. The sampling swab is prepared using biodegradable polymers and has good water absorption and mechanical strength that meets the sampling requirements. After sampling, the sampling swab can be degraded by alkali treatment or acid treatment, avoiding the generation of solid medical waste and reducing environmental pollution.

[0006] To achieve the above objectives, the present invention provides a method for preparing a sampling swab based on a natural polymer, comprising:

[0007] Chitosan and citric acid are mixed in water at high temperature to obtain a hot solution, wherein the high temperature environment is 70-90℃.

[0008] Carboxymethyl cellulose was placed in the hot solution and stirred to obtain a transparent paste;

[0009] Remove air bubbles from the transparent paste and soak it in citric acid solution to obtain a strip-shaped gel;

[0010] The strip-shaped gel was washed with water and soaked in water. The strip-shaped gel was freeze-dried and plasticized to obtain a rod-shaped material. The rod-shaped material was then cut to obtain a sampling swab.

[0011] This invention uses carboxymethyl cellulose as the main material to prepare biodegradable sampling swabs, and adds chitosan to enhance the mechanical properties of the swabs. Carboxymethyl cellulose is synthesized from natural cellulose and chloroacetic acid through an alkaline catalytic reaction, while chitosan is derived from chitin in the exoskeleton of crustaceans through deacetylation. Both polymers are biodegradable and have good biocompatibility, and can be converted into biomass, carbon dioxide, and water through a thermochemical process within a certain time and under specific conditions.

[0012] The sampling swabs of this invention can be biodegraded by Agrobacterium tumefaciens or treated with alkali or acid to become wastewater for discharge. Compared to traditional methods that require incineration or landfilling of sampling swabs, wastewater treatment has irreplaceable advantages. Chemically treated wastewater containing organic matter is a special water resource. Specifically, nutrients such as nitrogen, phosphorus, and potassium in the wastewater can be used for plant fertilization. Furthermore, aeration and microbial fuel cell technology can convert the organic matter in the wastewater into electrical energy, and the degradation rate is far greater than that of landfilling. Due to the involvement of microorganisms, the pH value of the wastewater does not need to be strictly limited during discharge; only activated carbon adsorption is needed after microbial treatment to remove non-degradable organic matter present in the wastewater or generated as oxidation byproducts. The wastewater has the potential to become a net energy producer. Even without the above technologies, the degraded liquid, after neutralization, can be treated as typical domestic sewage, consuming only 0.6 kWh / m³ of energy. 3 .

[0013] In addition, the sampling swab provided by this invention has both excellent water absorption and good mechanical properties, and can replace the cotton head, flocked head and rod of traditional sampling swabs. Only a single rod material is needed to meet the sampling requirements, which greatly simplifies the production process compared with commercial swabs of the prior art.

[0014] In some embodiments, the mass ratio of chitosan to citric acid in preparing the hot solution is 1:1-3:1. In some preferred embodiments, the mass ratio of chitosan to citric acid is 2:1. The advantage of this design is that chitosan can form a paste or be completely dissolved under acidic conditions, resulting in a more uniform mixing of the materials used in the subsequent sampling swab preparation. However, more citric acid is not necessarily better. When the mass ratio of chitosan to citric acid is less than 1:1, the transparent paste extruded at this ratio will disperse directly when squeezed into the citric acid solution. Therefore, this design ensures that the mass ratio of chitosan to citric acid is between 1:1 and 3:1, which guarantees uniform distribution of chitosan and maintains structural integrity during the soaking of the strip gel. Preferably, the mass ratio of chitosan to citric acid is controlled at 2:1. In addition, a certain mass ratio of chitosan and citric acid are placed in pure water and subjected to high-temperature treatment at 70-90°C for 15 minutes. The preferred high-temperature environment is: high-temperature treatment at 85°C for 15 minutes. This facilitates the uniform mixing of carboxymethyl cellulose and chitosan.

[0015] In some embodiments, the mass ratio of carboxymethyl cellulose to chitosan is 10:1 to 10:4. Such a ratio can be used to regulate the mechanical strength of carboxymethyl cellulose using chitosan.

[0016] Specifically, the addition of chitosan makes it possible to fabricate sampling swabs from carboxymethyl cellulose. This invention fully utilizes the property that chitosan is soluble in acidic solutions but insoluble in pure water. During the process of washing and soaking the strip-shaped gel with water, excess citric acid is washed away, causing the pH value of the acidic solution in which the strip-shaped gel is located to rise slowly. The water-insoluble chitosan precipitates from the strip-shaped gel, and the carboxymethyl cellulose on the strip-shaped gel is deposited onto the precipitated chitosan to obtain rod-shaped materials. The dense structure formed by the deposition can be used to control the mechanical properties of the sampling swab. The addition of a small amount of chitosan can improve the mechanical properties of the swab by 6-7 times.

[0017] In some embodiments, when the mass of carboxymethyl cellulose is 10%, the mass ratio of chitosan is 1-4%, preferably 2%. As mentioned earlier, during the process of washing and soaking the strip gel with water, the pH value of the acidic solution rises, and chitosan precipitates out to form a supporting "skeleton". The peak value is reached when the mass ratio of chitosan is 2%, at which point the chitosan support structure formed is the most regular and dense, and the chitosan is saturated. When the mass ratio of chitosan is further increased, the excess chitosan will affect this regular structure, but the degree of influence is limited. Therefore, in order to achieve the mechanical strength of the sampling swab, the proportion of chitosan provided in this scheme cannot be too high or too low.

[0018] Of course, the mass ratio of carboxymethyl cellulose can be 5%-15%, preferably 10%. Experiments have shown that when the mass ratio of carboxymethyl cellulose is 5%, the sample expands the most after soaking in pure water, resulting in a brittle, freeze-dried rod-shaped material. Conversely, a mass ratio of 15% makes it difficult to extrude the transparent paste. Experiments have shown that a mass ratio of 10% of carboxymethyl cellulose results in rods with the desired thickness and mechanical strength that meet the design requirements of this scheme. In some embodiments, a certain mass ratio of carboxymethyl cellulose is placed in the aforementioned hot solution and stirred for 3-7 minutes to obtain a transparent paste; preferably, the stirring time is controlled to be 5 minutes.

[0019] It should be noted that the increased mechanical strength of the sampling swab provided by this invention is not only due to the supporting "skeleton" formed by the low proportion of chitosan, but also because, during the process of extruding the transparent paste into a citric acid solution of a certain concentration to obtain a strip-shaped gel, the carboxyl groups on carboxymethyl cellulose and the amino groups in chitosan form ionic bonds (-COO). - +NH3 + This further increases the mechanical strength of the sampling swabs.

[0020] In some embodiments, the tensile strength of the sampling swab is 1.5-5 MPa.

[0021] In some embodiments, air bubbles in the transparent paste are removed by inserting it into one syringe and then squeezing it into another syringe to prevent large air bubbles in the transparent paste from causing the strip gel to break during subsequent manufacturing. This step can be repeated until there are no air bubbles in the transparent paste.

[0022] In some embodiments, the transparent paste after removing air bubbles is extruded into a 3-5 mol / L citric acid solution and soaked for 1-3 days to form a strip-shaped gel. When the concentration of citric acid is greater than 5 mol / L, the rod-shaped material will shrink strongly due to osmotic pressure. When the concentration of citric acid is less than 3 mol / L, the degree of cross-linking of the rod-shaped material is low, resulting in insufficient mechanical properties. Therefore, this method controls the concentration of citric acid to 3-5 mol / L to obtain a material with satisfactory mechanical properties.

[0023] In some embodiments, a transparent paste is extruded into a 4 mol / L citric acid solution and soaked for 2 days to form a strip-shaped gel. It should be noted that the soaking method used in this scheme not only allows carboxymethyl cellulose molecules to form hydrogen bonds, but also causes the molecules to aggregate and form a cross-linked network during the penetration of the high-concentration acid solution. If a large amount of citric acid is directly added to the gel, although hydrogen bonds will also form, there will be no molecular aggregation effect. This would cause the strip-shaped gel to disintegrate directly when subsequently soaked in water, preventing the formation of a rod-shaped structure.

[0024] In some embodiments, after washing the strip gel with water, the strip gel is soaked in pure water for 2-4 days with the water changed regularly to leach out uncrosslinked citric acid. At this time, chitosan will precipitate from the gel to improve the mechanical properties of the sampling swab. In a preferred embodiment, after washing the strip gel with water, the gel is soaked in pure water for 3 days with the water changed twice a day.

[0025] In some embodiments, the washed and soaked strip of gel is stretched, laid on aluminum foil, freeze-dried for 10-15 hours, and then plasticized. In some embodiments, the freeze-drying conditions are 12 hours.

[0026] It should be noted that the sampling swabs in this scheme not only have sufficient mechanical strength, but also strong water absorption. The cationic nature and high charge density of chitosan give the sampling swabs adhesive properties, and the abundant carboxyl groups on the carboxymethyl cellulose backbone endow the material with excellent water absorption, which is significantly greater than that of cotton swabs that absorb water by hydroxyl groups and flocked swabs that absorb water by amide bonds. This increases the water absorption strength of the sampling swabs.

[0027] Furthermore, the sampling swab provided in this solution features an integrated structure for both the swab stick and the swab head, with a relatively flexible overall material. Unlike traditional swabs where the tip of the swab is much thinner than the tip, the sampling swab of this invention lacks the brush-like texture of flocked swabs, resulting in less damage to nasal cells. The sampling swab of this invention is expected to be applied to various platforms, including bacteriological and virological culture, rapid antigen sampling, molecular-based sampling, direct fluorescent antibody (DFA) sampling, enzyme immunoassay (EIA), and cytological sampling. The sampling swab provided in this solution can be biodegraded by Agrobacterium and can also be treated with alkali or acid to become wastewater for discharge.

[0028] Secondly, this solution provides a sampling swab prepared according to the above preparation method. The rod and swab head are an integrated structure with a tensile strength of 1.5-5 MPa and are biodegradable.

[0029] In some embodiments, carboxymethyl cellulose within the sampling swab is deposited onto chitosan, which forms a large porous network structure, to create a dense structure. The sampling swab is completely soluble in acidic and alkaline solutions.

[0030] Compared with existing technologies, this solution has the following beneficial effects and features:

[0031] This method uses carboxymethyl cellulose, citric acid, and chitosan as raw materials. It utilizes the cross-linking effect of these three components to prepare a biodegradable gel, controlling the mass ratio of chitosan to be less than that of carboxymethyl cellulose. Based on the characteristic that chitosan is soluble in acidic solutions but insoluble in pure water, during the process of removing excess citric acid by soaking in water, chitosan precipitates out of the gel, allowing carboxymethyl cellulose to deposit onto the precipitated chitosan, thus increasing the mechanical strength of the resulting rod-shaped material to meet the strength requirements of the sampling swab. Furthermore, the sampling swab prepared by this method utilizes the properties of carboxymethyl cellulose and chitosan to achieve high water absorption, meeting the practical requirements of sampling. Attached Figure Description

[0032] Figure 1 This is a picture of the actual product of the prepared sampling swabs;

[0033] Figure 2 These are SEM images of cross-sections of swabs prepared using 10% carboxymethyl cellulose and chitosan of different concentrations;

[0034] Figure 3 This is a comparison chart of the water absorption rates of swabs prepared using 10% carboxymethyl cellulose and chitosan of different concentrations, cotton swabs, and flocked swabs.

[0035] Figure 4 The stress-strain curves of swabs prepared using 10% carboxymethyl cellulose and chitosan of different concentrations are shown.

[0036] Figure 5 This is a schematic diagram showing the tensile strength of swabs prepared using 10% carboxymethyl cellulose and chitosan of different concentrations;

[0037] Figure 6 This is a schematic diagram of the degradation of swabs prepared using 10% carboxymethyl cellulose and chitosan of different concentrations. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0039] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0040] Example 1 (OCS Chitosan):

[0041] Step 1: Take a certain volume of pure water, add 10wt% carboxymethyl cellulose to the water and stir rapidly and continuously for about 5 minutes until it becomes a transparent paste;

[0042] Step 2: Place the paste into a syringe and squeeze it into another syringe chamber to ensure a uniform gel composition and remove large air bubbles to prevent gel breakage during preparation. Repeat this process several times.

[0043] Step 3: Prepare a 4 mol / L citric acid solution. Squeeze the paste into the above citric acid solution and soak for 2 days to form a strip-shaped gel. Step 4: Remove the gel, wash it with water, and soak it in pure water for 3 days to leach out the uncrosslinked citric acid. Change the water twice a day during this period.

[0044] Step 5: Straighten the strip of gel, lay it on aluminum foil, freeze-dry for 12 hours, remove and shape it, and cut it into the required length.

[0045] Example 2 (1CS Chitosan):

[0046] Step 1: Take a certain volume of pure water, add 1 wt% chitosan and 0.5 wt% citric acid to the water, and place it in an 85℃ oven for 15 minutes. This process will facilitate the uniform mixing of carboxymethyl cellulose and chitosan in the subsequent process.

[0047] Step 2: Place 10 wt% carboxymethyl cellulose into the above hot solution and stir rapidly and continuously for about 5 minutes until it becomes a transparent paste;

[0048] Step 3: Place the paste into one syringe and squeeze it into another syringe to ensure the gel composition is uniform and to remove large air bubbles to prevent gel breakage during preparation. Repeat this process several times.

[0049] Step 4: Prepare a 4 mol / L citric acid solution. Squeeze the paste into the citric acid solution and soak for 2 days to form a strip-shaped gel.

[0050] Step 5: Remove the gel, wash it with water, and soak it in pure water for 3 days to leach out the uncrosslinked citric acid. Change the water twice a day during this period.

[0051] Step 6: Straighten the strip of gel, lay it on aluminum foil, freeze-dry for 12 hours, remove and shape, and cut into the required length.

[0052] Example 3 (2CS Chitosan)

[0053] Step 1: Take a certain volume of pure water, add 2wt% chitosan and 1wt% citric acid to the water, and place it in an 85℃ oven for 15 minutes. This process will facilitate the uniform mixing of carboxymethyl cellulose and chitosan in the subsequent process.

[0054] Step 2: Place 10 wt% carboxymethyl cellulose into the above hot solution and stir rapidly and continuously for about 5 minutes until it becomes a transparent paste;

[0055] Step 3: Place the paste into one syringe and squeeze it into another syringe to ensure the gel composition is uniform and to remove large air bubbles to prevent gel breakage during preparation. Repeat this process several times.

[0056] Step 4: Prepare a 4 mol / L citric acid solution. Squeeze the paste into the citric acid solution and soak for 2 days to form a strip-shaped gel.

[0057] Step 5: Remove the gel, wash it with water, and soak it in pure water for 3 days to leach out the uncrosslinked citric acid. Change the water twice a day during this period.

[0058] Step 6: Straighten the strip of gel, lay it on aluminum foil, freeze-dry for 12 hours, remove and shape, and cut into the required length.

[0059] The prepared sampling swabs are as follows Figure 1 As shown, the swab head and swab stick of the sampling swab obtained by this method are an integrated structure.

[0060] Example 4 (3CS Chitosan)

[0061] Step 1: Take a certain volume of pure water, add 3wt% chitosan and 1.5wt% citric acid to the water, and place it in an 85℃ oven for 15 minutes. This process will facilitate the uniform mixing of carboxymethyl cellulose and chitosan in the subsequent process.

[0062] Step 2: Place 10 wt% carboxymethyl cellulose into the above hot solution and stir rapidly and continuously for about 5 minutes until it becomes a transparent paste;

[0063] Step 3: Place the paste into one syringe and squeeze it into another syringe to ensure the gel composition is uniform and to remove large air bubbles to prevent gel breakage during preparation. Repeat this process several times.

[0064] Step 4: Prepare a 4 mol / L citric acid solution. Squeeze the paste into the citric acid solution and soak for 2 days to form a strip-shaped gel.

[0065] Step 5: Remove the gel, wash it with water, and soak it in pure water for 3 days to leach out the uncrosslinked citric acid. Change the water twice a day during this period.

[0066] Step 6: Straighten the strip of gel, lay it on aluminum foil, freeze-dry for 12 hours, remove and shape, and cut into the required length.

[0067] Example 5 (4CS Chitosan)

[0068] Step 1: Take a certain volume of pure water, add 4 wt% chitosan and 2 wt% citric acid to the water, and place it in an 85℃ oven for 15 minutes. This process will facilitate the uniform mixing of carboxymethyl cellulose and chitosan in the subsequent process.

[0069] Step 2: Place 10 wt% carboxymethyl cellulose into the above hot solution and stir rapidly and continuously for about 5 minutes until it becomes a transparent paste;

[0070] Step 3: Place the paste into one syringe and squeeze it into another syringe to ensure the gel composition is uniform and to remove large air bubbles to prevent gel breakage during preparation. Repeat this process several times.

[0071] Step 4: Prepare a 4 mol / L citric acid solution. Squeeze the paste into the citric acid solution and soak for 2 days to form a strip-shaped gel.

[0072] Step 5: Remove the gel, wash it with water, and soak it in pure water for 3 days to leach out the uncrosslinked citric acid. Change the water twice a day during this period.

[0073] Step 6: Straighten the strip of gel, lay it on aluminum foil, freeze-dry for 12 hours, remove and shape, and cut into the required length.

[0074] Based on Examples 1 to 5 above, sampling swabs corresponding to 0CS chitosan, 1CS chitosan, 2CS chitosan, 3CS chitosan, and 4CS chitosan can be obtained. The following tests were performed on the obtained sampling swabs:

[0075] Water absorption rate test:

[0076] The water absorption rate of the sampling swabs, cotton swabs, and flocked swabs from Examples 1-5 was tested: First, the mass of each swab was measured. For cotton swabs and flocked swabs, the swab sticks were cut off before measurement, and this mass was recorded as M1. The swabs were then completely immersed in water for 30 seconds, and the mass was measured again as M2. The water absorption rate of the swabs was calculated according to Formula 1. The results are as follows. Figure 3 As shown. Figure 3 Sampling swabs containing 0 wt%, 1 wt%, 2 wt%, 3 wt%, and 4 wt% chitosan and 10 wt% carboxymethyl cellulose, respectively, are labeled 0 wt%, 1 wt%, 2 wt%, 3 wt%, and 4 wt% chitosan.

[0077]

[0078] Mechanical strength test:

[0079] The mechanical properties of Examples 1-5, as well as the cotton and flocked swabs, were tested using a universal testing machine equipped with a 20N load cell. A 7cm swab sample was taken and loaded onto the machine's clamps. For each test, all samples were stretched at a rate of 20mm / min until fracture, with at least four replicates tested per group of swabs. The cross-sectional area of ​​each sample was calculated using the formula for the area of ​​a circle by measuring the radius with a micrometer. Tensile stress and strain were calculated based on the original cross-sectional area and length, respectively. The fracture strength was determined by the stress at fracture and plotted against changes in cross-sectional area and length. The mechanical property characterization results are shown in Table 1 and... Figure 4 as well as Figure 5 As shown.

[0080] Porosity test:

[0081] The swabs obtained in Examples 1-5 were immersed in liquid nitrogen for 30 seconds, then broken into cylindrical shapes of approximately 0.5 mm using tweezers. A 3 nm layer of platinum was then sputtered onto each swab, and images were taken using a Zeiss high-resolution analytical field emission scanning electron microscope (SEM). The area of ​​all pores in the obtained SEM images was then plotted using ImageJ software, and the area was calculated. This area was then divided by the cross-sectional area of ​​the material to obtain the porosity. The SEM images are shown below. Figure 2 As shown in Table 1, the test results for porosity are as follows:

[0082] Table 1: Main performance parameters of the sampling swabs prepared in this invention

[0083]

[0084]

[0085] As shown in Table 1, the water absorption rate of the sampling swabs synthesized using this method is approximately 3 times that of cotton swabs and 6 times that of flocked swabs, far exceeding the requirements for use. The addition of 1% and 2% chitosan significantly increased the tensile strength by 2-6 times, demonstrating that the carboxymethyl cellulose network adhered tightly to the previously precipitated chitosan during soaking in pure water and freeze-drying, resulting in a more compact polymer distribution and the formation of -COO- + NH3 -Ion pairings promoted this effect, and the 2-3 fold increase in porosity further corroborated this phenomenon. The aggregation of polymer chains increased phase separation, forming a polymer chain phase rich in CSC / CS and an aqueous phase within the system. During freeze-drying, the aqueous phase sublimated, leaving large pores. Soaking in water raised the pH, causing chitosan to precipitate and form a supporting "skeleton." When 1% chitosan was added, the swab's tensile strength more than doubled, and its toughness increased 3.6 times, demonstrating the initial formation of the chitosan support structure. At 2%, the chitosan support structure reached its peak, exhibiting the most regular and dense structure. As the chitosan concentration increased to 3% and 4%, this aggregation behavior saturated. The dispersed distribution of polymers without aggregation sites affected this regular structure, but to a limited extent; the porosity decreased again, and the mechanical properties did not improve further. Therefore, the sampling swabs produced when the mass ratio of carboxymethyl cellulose was 10% and the mass ratio of chitosan was 2% exhibited the optimal mechanical strength.

[0086] In addition, it can be seen that the water absorption and mechanical properties of the sampling swabs show opposite trends, showing a trend of first decreasing and then increasing. This is because when carboxymethyl cellulose is deposited on the chitosan support framework, the pore size increases to form a dense structure, but the surface area decreases, which leads to a decrease in water absorption. After the aggregation behavior is saturated, the dispersion of the polymer causes the surface area to increase again and the water absorption rate to rise again.

[0087] Combination Figure 2 The provided SEM images show that before the addition of chitosan, the pores of the freeze-dried gel were mostly elliptical. After adding a small amount of chitosan, the pores became angular, and the pore size first increased and then decreased with increasing concentration. Larger pore sizes result in a thicker and stronger scaffold forming the porous structure. This further demonstrates that the support structure formed by chitosan has a saturation concentration. After reaching this saturation concentration, the remaining chitosan is randomly distributed in various pore sizes, diverting carboxymethyl cellulose that could have been deposited on the framework structure. This result also explains the significant decrease in tensile strength at chitosan concentrations of 3% and 4%.

[0088] Wastewater treatment test:

[0089] Wastewater treatment characterization tests were conducted on the sampling swabs prepared in Examples 1 to 5. A 3cm swab strip was placed in a reagent bottle, and a 100g / L sodium carbonate solution was added. After 12 hours, the liquid in the bottle was poured out, and waste acid used to soak the swabs was added. The swab strip was then subjected to a treatment process from initial degradation to complete dissolution. Figure 6 As shown, the alkali can react with the cross-linked citric acid and carboxyl groups in carboxymethyl cellulose in the swab, destroying their network structure and leaving only the chitosan network. Due to the presence of amino groups, chitosan is a strong alkali. When waste acid from the previously synthesized materials is added, the amino groups on the polymer chains are protonated, forming polyelectrolytes, thus destroying and dissolving the chitosan network.

[0090] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for preparing a sampling swab based on a natural polymer, characterized in that, include: Chitosan and citric acid are mixed in water at high temperature to obtain a hot solution, wherein the high temperature environment is 70-90℃, and the mass ratio of chitosan to citric acid is 1:1-3:

1. 5-15 wt% carboxymethyl cellulose was placed in the hot solution and stirred to obtain a transparent paste. The mass ratio of carboxymethyl cellulose to chitosan was 10:1-10:

4. Remove air bubbles from the transparent paste, and then extrude the air-bubbled transparent paste into a 3 mol / L - 5 mol / L citric acid solution to soak for 1-3 days to form a strip gel. The strip-shaped gel was washed with water and soaked in water. The strip-shaped gel was freeze-dried and plasticized to obtain a rod-shaped material. The rod-shaped material was then cut to obtain a sampling swab.

2. The method for preparing a sampling swab based on a natural polymer according to claim 1, characterized in that, During the process of washing the strip gel with water, excess citric acid is washed away, causing the pH value of the acidic solution in which the strip gel is located to rise slowly. Chitosan, which is insoluble in water, precipitates from the strip gel, and carboxymethyl cellulose on the strip gel is deposited onto the precipitated chitosan to obtain rod-shaped materials. During the process of extruding the transparent paste into the citric acid solution to obtain the strip gel, the carboxyl groups on the carboxymethyl cellulose and the amino groups in the chitosan form ionic bonds.

3. A sampling swab based on a natural polymer, characterized in that, The swab is prepared according to any one of claims 1 to 2, wherein the swab stick and the swab head are an integrated structure.

4. The sampling swab based on natural polymers according to claim 3, characterized in that, It has a fracture strength of 1.5-5 MPa.

5. The sampling swab based on natural polymers according to claim 3, characterized in that, Carboxymethyl cellulose in the sampling swab is deposited onto chitosan, which forms a large porous network structure, to create a dense structure. The sampling swab is completely soluble in both acidic and alkaline solutions.

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