CN109964931B - Method for preparing chitosan antibacterial nano-microspheres by jet self-excitation pulse cavitation enhancement - Google Patents
Method for preparing chitosan antibacterial nano-microspheres by jet self-excitation pulse cavitation enhancement Download PDFInfo
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Abstract
The invention relates to a method for preparing chitosan antibacterial nano microspheres by jet self-excitation pulse cavitation reinforcement, which comprises the following steps: (1) preparing a chitosan solution, (2) preparing an anionic cross-linking agent solution, (3) preparing a bacteriostatic agent solution, (4) mixing a bacteriostatic agent and the anionic cross-linking agent solution, and (5) preparing the chitosan bacteriostatic nano-microspheres by jet self-excited pulse cavitation enhancement: the mixed solution of chitosan, bacteriostatic agent and anionic crosslinking agent is added into a jet self-excited pulse cavitation strengthening device, and the jet self-excited pulse cavitation strengthening device can generate self-excited oscillation and strong jet pulse cavitation. The invention makes the cavitation effect generated by jet self-excited pulse act on the electrostatic adsorption crosslinking process between the chitosan solution and the anion crosslinking agent, thus achieving the purpose of strengthening the preparation process of the chitosan nano-microsphere; the method has the advantages of simple operation, low energy consumption, good repeatability and easy process control.
Description
Technical Field
The invention relates to a method for preparing chitosan antibacterial nano microspheres by jet self-excitation pulse cavitation enhancement.
Background
The chitosan is a natural high molecular polymer, and is a chain polyamino alkalescent polysaccharide with positive charges, which is obtained by deacetylation reaction of chitin. Because the chitosan/chitosan. Therefore, the preparation of chitosan microspheres or nano-microspheres thereof has been receiving much attention in the industry.
At present, the preparation methods of chitosan microspheres or nano-microspheres thereof mainly include an emulsion crosslinking method, an ionic gel method, a coagulation-precipitation method, an emulsion droplet agglomeration method, a spray drying method, a solvent evaporation method and the like. In the preparation process of the emulsification crosslinking method, the spray drying method and the solvent evaporation method, a dilute chitosan acid solution and an oil phase are usually required to be mixed to form a W/O type inverse emulsion, and then subsequent ammonia-aldehyde condensation reaction, atomization drying and vacuum evaporation operations are carried out, so that the prepared microspheres are usually large in particle size (> 1.0 μm), uneven in particle size distribution and difficult to control in particle size morphology, and meanwhile, the phenomenon of mutual adhesion between the microspheres or overhigh energy consumption is easily caused due to the use of the oil phase with high viscosity or the adoption of high-temperature operation. The ion gel method, the coacervation-precipitation method and the emulsion droplet coalescence method can be used for preparing the chitosan nano microsphere, and the particle size of the obtained microsphere can be usually less than 1.0 μm. Wherein, no organic solvent is used in the preparation process of the coacervation-precipitation method, thereby avoiding the toxic and side effects possibly caused by the organic solvent, but the prepared microspheres have low encapsulation efficiency on the medicament and high medicament release rate; an aldehyde cross-linking agent is not used in the preparation process of the emulsion droplet coalescence method, so that the toxic and side effects caused by aldehyde substances are avoided, but the preparation process has complicated operation steps and overlong emulsification time.
The ionic gel method is the most common method for preparing chitosan nano microspheres, and the process is to dissolve chitosan in dilute acid solution to form polycation, and then to promote the polycation and anionic compounds with negative charges to generate electrostatic adsorption crosslinking by adopting a mechanical stirring mode, belonging to a physical crosslinking process. However, the mechanical stirring operation adopted by the method belongs to the macro realization of contact, dissolution and mixing of different liquids, the mixing process has low efficiency, easy occurrence of dead angles, poor micro mass transfer effect and high process energy consumption, so that the prepared microspheres have the defects of low mechanical strength, low drug loading rate, uneven particle size distribution, difficult control of the morphology, the particle size and the dispersibility of the microspheres and the like.
Therefore, how to strengthen the preparation process of the chitosan microspheres/nano microspheres and solve the problems are the key points of attention of people at present and the key point of producing the chitosan microspheres/nano microspheres in an efficient, energy-saving and green manner.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method for preparing the chitosan antibacterial nano-microspheres by jet self-excited pulse cavitation enhancement is provided, namely, the cavitation effect generated by the jet self-excited pulse acts on the electrostatic adsorption crosslinking process between the chitosan solution and the anion crosslinking agent, so as to achieve the purpose of enhancing the preparation process of the chitosan nano-microspheres; the method has the advantages of simple operation, low energy consumption, good repeatability and easy process control, and solves the problems in the prior art.
The technical scheme for solving the technical problems is as follows: a method for preparing chitosan bacteriostatic nano-microspheres by jet self-excitation pulse cavitation enhancement comprises the following steps:
(1) preparing a chitosan solution: weighing chitosan and pouring the chitosan into an acidic medium to prepare a chitosan solution with the mass concentration of 0.5-12.0 g/L; the acidic medium is an organic acid aqueous solution or an acidic buffer solution, the organic acid is formic acid, acetic acid, citric acid, tartaric acid, monochloroacetic acid, amino acid or oxalic acid, the acidic buffer solution is acetic acid-sodium acetate and citric acid-sodium citrate, the mass concentration of the organic acid aqueous solution is 1-15%, and the pH value of the acidic buffer solution is 1.0-4.6;
(2) preparing an anionic cross-linking agent solution: weighing an anionic cross-linking agent, dissolving the anionic cross-linking agent in deionized water, and preparing a solution with the mass concentration of 1.0-10.0 g/L; the anion cross-linking agent is sodium tripolyphosphate, polyglutamic acid and sodium dodecyl sulfate;
(3) preparing a bacteriostatic agent solution: weighing bacteriostatic agent, dissolving in deionized water, and preparing into solution with molar concentration of 0.1-1.5 mmol/L; the bacteriostatic agent is methylisothiazolinone;
(4) mixing of bacteriostatic agent and anionic cross-linking agent solution: adding the bacteriostatic agent solution obtained in the step (3) into the anion exchanger solution obtained in the step (2), and fully and uniformly mixing to obtain a bacteriostatic agent-containing anion cross-linking agent mixed solution; the volume ratio of the anion exchanger solution to the bacteriostatic agent solution is 4: 4.8-5.2;
(5) the jet self-excited pulse cavitation strengthening preparation of the chitosan antibacterial nano-microspheres comprises the following steps: the device used in the step is a jet self-excited pulse cavitation strengthening device, the jet self-excited pulse cavitation strengthening device comprises a feed liquid storage tank, a constant temperature circulating water tank, a driving pump, a pipeline flowmeter, a jet self-excited pulse cavitation strengthening element, a feed liquid conveying pipeline, a valve for regulating and controlling feed liquid conveying flow, a pressure gauge I and a pressure gauge II for monitoring inlet pressure and outlet pressure of the jet self-excited pulse cavitation strengthening element, the driving pump is respectively communicated with the feed liquid storage tank and the inlet of the jet self-excited pulse cavitation strengthening element through the feed liquid conveying pipeline, the outlet of the jet self-excited pulse cavitation strengthening element is communicated with the inlet of the pipeline flowmeter through the feed liquid conveying pipeline, and the outlet of the pipeline flowmeter is communicated with the feed liquid storage tank through the feed liquid conveying pipeline;
the specific process flow of the step is as follows: pouring the chitosan solution obtained in the step (1) into a material liquid storage tank of a jet self-excited pulse cavitation strengthening device, starting a driving pump, regulating and controlling the inlet pressure and the outlet pressure in a jet self-excited pulse cavitation strengthening element through a valve, respectively monitoring the inlet pressure and the outlet pressure of the jet self-excited pulse cavitation strengthening element through a pressure gauge, simultaneously starting a constant-temperature circulating water tank to control the crosslinking temperature, adding the anion cross-linking agent mixed solution containing the bacteriostatic agent obtained in the step (4) into the material liquid storage tank when the device reaches the required inlet pressure, outlet pressure and crosslinking temperature, controlling the mass ratio of the anion cross-linking agent to chitosan to be 0.10-0.40, refluxing the material liquid subjected to jet self-excited pulse cavitation strengthening treatment into the storage tank, and performing continuous circulating crosslinking for 10-30 min to obtain chitosan bacteriostatic nano microspheres; the inlet pressure of the jet self-excited pulse cavitation strengthening element is controlled to be 0.15-1.2 MPa, the outlet pressure is ambient pressure, and the crosslinking temperature is controlled to be 25-60 ℃.
The further technical scheme of the invention is as follows: the jet self-excited pulse cavitation strengthening element is a throttling device with a resonant cavity in the middle, and sequentially comprises an inlet section, a contraction section, an upper nozzle jet section, a resonant cavity section, a lower nozzle jet section, an expansion section and an outlet section along the flowing direction of a material liquid; the inlet cone angle alpha of the inlet section of the jet self-excited pulse cavitation strengthening element is 30-45 degrees, the outlet cone angle beta of the outlet section is 25-90 degrees, and the diameter d of the upper nozzle1Diameter d of lower nozzle2The ratio of (a) to (b) is 0.20 to 0.86, the length of the resonant cavity (l) and the diameter (d) of the upper nozzle1The ratio of (A) to (B) is 4.5-30.0.
The resonant cavity of the jet self-excited pulse cavitation strengthening element is provided with an outlet impact section, and the cone angle gamma of the outlet impact section is 90-180 degrees.
The molecular weight of the chitosan is 10-100 kDa, and the deacetylation degree is 60-98%.
The post-treatment comprises centrifugation, washing and vacuum drying.
The principle of the invention is as follows: the jet self-excited pulse cavitation is that cavitation bubbles are generated due to sudden reduction of pressure when stable fluid passes through a throttling nozzle, and the stable fluid collides with a cross section through an outlet in a resonant cavity chamber to trigger cavitation jet beams to form self-excited pressure oscillation, and the pressure oscillation is fed back to the resonant cavity to form feedback pressure oscillation; when the pressure oscillation frequency fed back by the self-oscillation is equal to the natural frequency of the resonant cavity, acoustic harmonic resonance is generated in the resonant cavity chamber, so that the fluid is promoted to form a large-structure annular vortex ring in the resonant cavity, a low-pressure area is further formed in the center of the vortex ring structure, cavitation bubbles can fully grow in the low-pressure area, and high-speed pulse jet flow with instantaneous jet flow energy higher than continuous jet flow energy is formed; the energy released when a sufficiently long cavitation bubble collapses upon an increase in ambient pressure is higher, thereby producing a stronger cavitation effect than conventional hydrodynamic cavitation (venturi tube). The invention uses jet self-excited pulse cavitation technology for preparing antibacterial nano microspheres by an intensified ion crosslinking method, and the main technical principle comprises the following steps: (1) and (4) degradation effect. In the jet self-excited pulse cavitation strengthening device, when the mixed solution of chitosan, bacteriostatic agent and anion cross-linking agent passes through the jet self-excited pulse cavitation strengthening element, chitosan molecules are degraded to generate chitosan oligosaccharide molecules with lower molecular weight under the action of strong cavitation generated by self-excited oscillation pulses in a resonant cavity, so that on one hand, the chance of contacting the chitosan/chitosan oligosaccharide molecules with the anion cross-linking agent is increased, and the electrostatic adsorption cross-linking rate of the chitosan/chitosan oligosaccharide molecules and the anion cross-linking agent is accelerated; on the other hand, the degraded chitosan oligosaccharide molecules are more beneficial to preparing chitosan nano microspheres with smaller granularity and finer particles to a great extent. (2) Micro-mixing effect. Under the action of the resonant cavity, the peak pressure of the pulse cavitation jet is higher than that of the continuous pulse jet, so that stronger mechanical effects such as impact force, shearing force and the like can be generated in a limited impact area; in addition, the nozzle in the jet self-excited pulse cavitation strengthening element causes cavitation bubbles due to pressure drop generated by throttling, and the cavitation bubbles can generate local high temperature (1000-5000 ℃), instantaneous high pressure (1-50 MPa) and strong cavitation effects such as shock waves, micro-jet and violent turbulence in a very small space range around the cavitation bubbles at the moment of collapse when the environmental pressure is increased. Under the synergistic action of cavitation and impact, the micro-mixing degree among chitosan, the bacteriostatic agent and the anionic cross-linking agent is enhanced, and a more uniformly distributed concentration field is generated, so that the phenomena of macro-mixing and easy generation of dead angles among liquids under the traditional mechanical stirring operation are avoided, meanwhile, heat transfer and mass transfer among fluids are also intensified, the electrostatic adsorption efficiency between chitosan molecules and anionic cross-linking agent molecules is greatly promoted, the cross-linking effect between the chitosan molecules and the anionic cross-linking agent molecules is improved, and the embedding effect of nano microspheres generated by cross-linking on the bacteriostatic agent molecules is promoted to a certain extent.
The invention has the beneficial effects that: (1) compared with the traditional mechanical stirring operation preparation process, the average particle size of the chitosan nano-microsphere prepared by the invention is reduced by at least more than 30%, and the encapsulation rate of the microsphere on methylisothiazolinone and other medicaments is improved by at least more than 20%; and is superior to the preparation effect of the common hydrodynamic cavitation (Venturi tube); (2) the phenomenon that the particle size is too large due to high local concentration of chitosan molecules and an anionic cross-linking agent in a traditional mechanical stirring and mixing field and the cross-linking is generated is avoided, and the particle size distribution is narrower; meanwhile, the prepared nano microspheres have good dispersibility, good balling property and round shape; the shape of the nano-microsphere is easier to be regulated and controlled; (3) the enhanced preparation method provided by the invention is simple and convenient to operate, low in energy consumption, good in repeatability and easy to control the process.
Drawings
FIG. 1: the structure of the jet self-excited pulse cavitation enhancing device is schematically shown.
FIG. 2: the structure of the jet self-excited pulse cavitation strengthening element of the present invention is schematically illustrated.
In the figure: 1-a material liquid storage tank, 2-a constant temperature circulating water tank, 3-a valve I, 4-a driving pump, 5-a valve II, 6-a pressure gauge I, 7-a jet self-excitation pulse cavitation strengthening element, 71-an inlet section, 72-a contraction section, 73-an upper nozzle jet section, 74-a resonant chamber section, 75-a lower nozzle jet section, 76-an expansion section, 77-an outlet section, 8-a valve III, 9-a pressure gauge II, 10-a valve IV, 11-a flow meter.
In the figure: s represents the outlet impact section of the jet self-excitation pulse cavitation strengthening element, and an arrow represents the flowing direction of the feed liquid.
Detailed Description
Example 1:
a method for preparing chitosan bacteriostatic nano-microspheres by jet self-excitation pulse cavitation enhancement comprises the following steps:
(1) preparing a chitosan solution: weighing 1.5 g of chitosan sample (molecular weight is 50 kDa, degree of deacetylation is 85%) and pouring into 1.0L of formic acid solution (pH value is 2.16) with mass concentration of 1%, stirring until most of solid is dissolved, standing for 2.0 h to fully dissolve chitosan, removing undissolved chitosan colloid and other impurities by using double-layer filter cloth, and preparing into chitosan solution with mass concentration of 1.5 g/L;
(2) preparing an anionic cross-linking agent solution: weighing 1.5 g of sodium tripolyphosphate and dissolving in 1.0L of deionized water to prepare a sodium tripolyphosphate solution with the mass concentration of 1.5 g/L;
(3) preparing a bacteriostatic agent solution: weighing 0.58 g of methylisothiazolinone with the mass fraction of 10 percent, and dissolving in 1.0L of deionized water to prepare methylisothiazolinone solution with the molar concentration of 0.5 mmol/L;
(4) mixing of bacteriostatic agent and anionic cross-linking agent solution: adding 0.5L of the methylisothiazolinone solution obtained in the step (3) into 0.4L of the sodium tripolyphosphate solution obtained in the step (2), and fully and uniformly mixing to obtain a mixed solution of sodium tripolyphosphate containing methylisothiazolinone;
(5) jet self-excited pulse cavitation strengthening preparation of the microspheres: the device used in the step is a jet self-excited pulse cavitation strengthening device which can generate self-excited oscillation and strong jet pulse cavitation. The jet self-excited pulse cavitation strengthening device (as shown in figure 1) comprises a feed liquid storage tank 1, a constant-temperature circulating water tank 2, a driving pump 4, a pipeline flowmeter 11, a jet self-excited pulse cavitation strengthening element 7, a feed liquid conveying pipeline, a valve I3, a valve II 5, a valve III 8, a valve IV 10 for regulating and controlling feed liquid conveying flow, a pressure gauge I6 for monitoring inlet pressure of the jet self-excited pulse cavitation strengthening element and a pressure gauge II 9 for monitoring outlet pressure of the jet self-excited pulse cavitation strengthening element, wherein the driving pump 4 is respectively communicated with the feed liquid storage tank 1 and an inlet of the jet self-excited pulse cavitation strengthening element 7 through pipelines, an outlet of the driving pump is communicated with the feed liquid storage tank through another pipeline, an outlet of the jet self-excited pulse cavitation strengthening element 7 is communicated with an inlet of the pipeline flowmeter 11 through a pipeline. The valve I3 is arranged on a pipeline for communicating the feed liquid storage tank 1 with the inlet of the driving pump 4, the valve II 5 is arranged on a pipeline for communicating the outlet of the driving pump 4 with the inlet of the jet self-excited pulse cavitation strengthening element 7, the valve III 8 is arranged on a pipeline for communicating the outlet of the driving pump 4 with the feed liquid storage tank 1, and the valve IV 10 is arranged on a pipeline for communicating the outlet of the jet self-excited pulse cavitation strengthening element 7 with the inlet of the flow meter 11. The pressure gauge I6 is arranged on a pipeline which is communicated with the outlet of the valve II 5 and the inlet of the jet self-excited pulse cavitation strengthening element 7, and the pressure gauge II 9 is arranged on a pipeline which is communicated with the inlet of the valve IV 10 and the outlet of the jet self-excited pulse cavitation strengthening element 7.
The specific process flow of the step is as follows: pouring 1.0L of the chitosan solution obtained in the step (1) into a feed liquid storage tank 1 of a jet self-excited pulse cavitation strengthening device (shown in figure 1), starting a driving pump 4, adjusting and controlling the inlet pressure and the outlet pressure of a jet self-excited pulse cavitation strengthening element 7 through a valve I3, a valve II 5, a valve III 8 and a valve IV 10, respectively monitoring the inlet pressure and the outlet pressure through a pressure gauge I6 and a pressure gauge II 9, simultaneously starting a constant-temperature circulating water tank 2 to control the crosslinking temperature, adding the mixed solution containing the sodium tripolyphosphate of the methylisothiazolinone obtained in the step (4) into the feed liquid storage tank 1 when the inlet pressure is 0.5 MPa and the outlet pressure is 0 (namely the actual outlet pressure of the jet self-excited pulse cavitation strengthening element 7 is close to atmospheric pressure) and the crosslinking temperature is 35 ℃, and refluxing the feed liquid subjected to self-excited pulse cavitation treatment into the feed liquid storage tank 1, and after continuous cyclic crosslinking is carried out for 20 min, centrifuging the obtained microemulsion at the rotating speed of 10000 r/min, removing supernatant, alternately and fully washing precipitate by using petroleum ether and deionized water, and finally, drying in vacuum at 50 ℃ to prepare the chitosan antibacterial nano microsphere.
In this embodiment, the jet self-excited pulse cavitation enhancing element (as shown in fig. 2) is a throttling device with a resonant cavity in the middle, along the flowing direction of the material liquid, the jet self-excited pulse cavitation enhancing element sequentially comprises an inlet section 71, a contraction section 72, an upper nozzle jet section 73, a resonant cavity section 74, a lower nozzle jet section 75, an expansion section 76 and an outlet section 77, and an inlet cone of the inlet section of the jet self-excited pulse cavitation enhancing elementAngle alpha is 30 deg., outlet cone angle beta of outlet section is 45 deg., diameter d of upper nozzle14.3 mm, lower nozzle diameter d211.0 mm and the resonant cavity length l 35.0 mm.
In this embodiment, the resonant cavity of the jet self-excited pulse cavitation enhancing element (as shown in fig. 2) is provided with an outlet impact section S, and the cone angle γ of the outlet impact section is 120 °.
The chitosan nano-microsphere prepared by the embodiment has good dispersibility, good balling property, round shape, narrow particle size distribution, average particle size of 120.7 nm, encapsulation efficiency of 56.3%, PDI value of 0.18 and Zeta potential of 49.76 mV; under the same material proportion, compared with the cavitation of a common Venturi tube, the average particle size is reduced by 12.1%, the encapsulation efficiency is improved by 9.5%, and compared with the traditional mechanical stirring, the average particle size is reduced by 40.2%, and the encapsulation efficiency is improved by 29.8%.
Example 2:
a method for preparing chitosan bacteriostatic nano-microspheres by jet self-excitation pulse cavitation enhancement comprises the following steps:
(1) preparing a chitosan solution: weighing 5.0 g of chitosan sample (molecular weight 90 kDa, degree of deacetylation 95%) and pouring into 1.0L of citric acid solution (pH value 2.21) with mass concentration of 1%, stirring until most of solid is dissolved, standing for 2.0 h to fully dissolve chitosan, removing undissolved chitosan colloid and other impurities by using double-layer filter cloth, and preparing into chitosan solution with mass concentration of 5.0 g/L;
(2) preparing an anionic cross-linking agent solution: weighing 3.5g of sodium dodecyl sulfate, dissolving in 1.0L of deionized water, and preparing into a sodium dodecyl sulfate solution with the mass concentration of 3.5 g/L;
(3) preparing a bacteriostatic agent solution: weighing 1.15 g of methylisothiazolinone with the mass fraction of 10 percent, and dissolving in 1.0L of deionized water to prepare methylisothiazolinone solution with the molar concentration of 1.0 mmol/L;
(4) mixing of bacteriostatic agent and anionic cross-linking agent solution: adding 0.5L of methylisothiazolinone solution obtained in the step (3) into 0.4L of sodium dodecyl sulfate solution obtained in the step (2), and fully and uniformly mixing to obtain a mixed solution of sodium dodecyl sulfate containing methylisothiazolinone;
(5) jet self-excited pulse cavitation strengthening preparation of the microspheres: pouring 1.0L of the chitosan solution obtained in the step (1) into a feed liquid storage tank 1 of a jet self-excited pulse cavitation strengthening device (shown in figure 1), starting a driving pump 4, adjusting and controlling the inlet pressure and the outlet pressure of a jet self-excited pulse cavitation strengthening element 7 through a valve I3, a valve II 5, a valve III 8 and a valve IV 10, respectively monitoring the inlet pressure and the outlet pressure through a pressure gauge I6 and a pressure gauge II 9, simultaneously starting a constant-temperature circulating water tank 2 to control the crosslinking temperature, adding the mixed solution containing the methylisothiazolinone sodium dodecyl sulfate obtained in the step (4) into the feed liquid storage tank 1 when the inlet pressure is 0.5 MPa and the outlet pressure is 0 (namely the actual outlet pressure of the jet self-excited pulse cavitation strengthening element 7 is close to atmospheric pressure) displayed by a pressure gauge I6 and the crosslinking temperature is 30 ℃, and refluxing the feed liquid subjected to self-excited pulse cavitation treatment into the feed liquid storage tank 1, and after continuous circulating crosslinking is carried out for 25 min, the obtained microemulsion is treated by the same method as the embodiment 1, and the chitosan antibacterial nano-microsphere can be prepared.
In this embodiment, the structure of the jet self-excited pulse cavitation enhancing device (as shown in fig. 1) is the same as that of embodiment 1.
In this embodiment, the jet self-excited pulse cavitation enhancing element (as shown in fig. 2) is a throttling device with a resonant chamber in the middle, and the jet self-excited pulse cavitation enhancing element sequentially comprises an inlet section 71, a contraction section 72, an upper nozzle jet section 73, a resonant chamber section 74, a lower nozzle jet section 75, an expansion section 76 and an outlet section 77 along the flowing direction of the material liquid, wherein the inlet cone angle α of the inlet section of the jet self-excited pulse cavitation enhancing element is 35 °, the outlet cone angle β of the outlet section is 60 °, and the diameter d of the upper nozzle is 60 °15.3 mm, lower nozzle diameter d210.0 mm and the resonant cavity length l is 50.0 mm.
In this embodiment, in the resonant cavity of the jet self-excited pulse cavitation enhancing element (as shown in fig. 2), an outlet impact section S is provided, and the outlet impact section taper angle γ is 90 °.
The chitosan nano-microsphere prepared by the embodiment has good dispersibility, good balling property, round shape, narrow particle size distribution, average particle size of 168.3 nm, encapsulation efficiency of 46.7%, PDI value of 0.23 and Zeta potential of 46.78 mV; under the same material proportion, compared with the cavitation of a common Venturi tube, the average particle size is reduced by 14.3%, the encapsulation efficiency is improved by 10.1%, and compared with the traditional mechanical stirring, the average particle size is reduced by 37.9%, and the encapsulation efficiency is improved by 25.8%.
Example 3:
a method for preparing chitosan bacteriostatic nano-microspheres by jet self-excitation pulse cavitation enhancement comprises the following steps:
(1) preparing a chitosan solution: weighing 8.0 g of chitosan sample (molecular weight 80 kDa, deacetylation degree 90%) and pouring into 1.0L of acetic acid-sodium acetate buffer solution with pH value of 3.6, stirring until most of solid is dissolved, standing for 2.0 h to fully dissolve chitosan, removing undissolved chitosan colloid and other impurities by using double-layer filter cloth, and preparing into chitosan solution with mass concentration of 8.0 g/L;
(2) preparing an anionic cross-linking agent solution: weighing 3.0 g of polyglutamic acid, and dissolving in 1.0L of deionized water to prepare a polyglutamic acid solution with the mass concentration of 3.0 g/L;
(3) preparing a bacteriostatic agent solution: weighing 0.34 g of methylisothiazolinone with the mass fraction of 10 percent, dissolving in 1.0L of deionized water to prepare methylisothiazolinone solution with the molar concentration of 0.3 mmol/L;
(4) mixing of bacteriostatic agent and anionic cross-linking agent solution: adding 0.5L of methylisothiazolinone solution obtained in the step (3) into 0.4L of polyglutamic acid solution obtained in the step (2), and fully and uniformly mixing to obtain a mixed solution of polyglutamic acid containing methylisothiazolinone;
(5) jet self-excited pulse cavitation strengthening preparation of the microspheres: pouring 1.0L of the chitosan solution obtained in the step (1) into a feed liquid storage tank 1 of a jet self-excited pulse cavitation strengthening device (shown in figure 1), starting a driving pump 4, adjusting and controlling the inlet pressure and the outlet pressure of a jet self-excited pulse cavitation strengthening element 7 through a valve I3, a valve II 5, a valve III 8 and a valve IV 10, respectively monitoring the inlet pressure and the outlet pressure through a pressure gauge I6 and a pressure gauge II 9, simultaneously starting a constant-temperature circulating water tank 2 to control the crosslinking temperature, adding the mixed solution containing the methyl isothiazolinone polyglutamic acid obtained in the step (4) into the feed liquid storage tank 1 when the inlet pressure is 0.5 MPa and the outlet pressure is 0 (namely the actual outlet pressure of the jet self-excited pulse cavitation strengthening element 7 is close to atmospheric pressure) and the crosslinking temperature reaches 30 ℃, and refluxing the feed liquid subjected to self-excited pulse cavitation treatment into the feed liquid storage tank 1, and after continuous circulating crosslinking is carried out for 25 min, the obtained microemulsion is treated by the same method as the embodiment 1, and the chitosan antibacterial nano-microsphere can be prepared.
In this embodiment, the structure of the jet self-excited pulse cavitation enhancing device (as shown in fig. 1) is the same as that of embodiment 1.
In this embodiment, the jet self-excited pulse cavitation enhancing element (as shown in fig. 2) is a throttling device with a resonant chamber in the middle, and the jet self-excited pulse cavitation enhancing element sequentially comprises an inlet section 71, a contraction section 72, an upper nozzle jet section 73, a resonant chamber section 74, a lower nozzle jet section 75, an expansion section 76 and an outlet section 77 along the flowing direction of the material liquid, wherein the inlet cone angle α of the inlet section of the jet self-excited pulse cavitation enhancing element is 45 degrees, the outlet cone angle β of the outlet section is 75 degrees, and the diameter d of the upper nozzle is 75 degrees1Is 6.1 mm, the lower nozzle diameter d213.0 mm and the resonant cavity length l is 80.0 mm.
In this embodiment, in the resonant cavity of the jet self-excited pulse cavitation enhancing element (as shown in fig. 2), an outlet impact section S is provided, and the outlet impact section taper angle γ is 180 °.
The chitosan nano-microsphere prepared by the embodiment has good dispersibility, good balling property, round shape, narrow particle size distribution, average particle size of 183.2 nm, encapsulation efficiency of 52.7%, PDI value of 0.25 and Zeta potential of 45.75 mV; under the same material proportion, compared with the cavitation of a common Venturi tube, the average particle size is reduced by 12.8%, the encapsulation efficiency is improved by 11.5%, and compared with the traditional mechanical stirring, the average particle size is reduced by 45.3%, and the encapsulation efficiency is improved by 27.1%.
As a variation of the embodiments of the present invention, a jet self-excited pulse cavitation enhancing device with other structural forms may also be adopted as long as the resonant cavity of the jet self-excited pulse cavitation enhancing element can generate self-excited pulse cavitation.
Claims (3)
1. A method for preparing chitosan antibacterial nano-microspheres by jet self-excitation pulse cavitation enhancement is characterized by comprising the following steps: the method comprises the following steps:
(1) preparing a chitosan solution: weighing chitosan and pouring the chitosan into an acidic medium to prepare a chitosan solution with the mass concentration of 0.5-12.0 g/L; the acidic medium is an organic acid aqueous solution or an acidic buffer solution, the organic acid is formic acid, acetic acid, citric acid, tartaric acid, monochloroacetic acid, amino acid or oxalic acid, the acidic buffer solution is acetic acid-sodium acetate and citric acid-sodium citrate, the mass concentration of the organic acid aqueous solution is 1-15%, and the pH value of the acidic buffer solution is 1.0-4.6;
(2) preparing an anionic cross-linking agent solution: weighing an anionic cross-linking agent, dissolving the anionic cross-linking agent in deionized water, and preparing a solution with the mass concentration of 1.0-10.0 g/L; the anion cross-linking agent is sodium tripolyphosphate, polyglutamic acid and sodium dodecyl sulfate;
(3) preparing a bacteriostatic agent solution: weighing bacteriostatic agent, dissolving in deionized water, and preparing into solution with molar concentration of 0.1-1.5 mmol/L; the bacteriostatic agent is methylisothiazolinone;
(4) mixing of bacteriostatic agent and anionic cross-linking agent solution: adding the bacteriostatic agent solution obtained in the step (3) into the anion exchanger solution obtained in the step (2), and fully and uniformly mixing to obtain a bacteriostatic agent-containing anion cross-linking agent mixed solution; the volume ratio of the anion exchanger solution to the bacteriostatic agent solution is 4: 4.8-5.2;
(5) the jet self-excited pulse cavitation strengthening preparation of the chitosan antibacterial nano-microspheres comprises the following steps: the device used in the step is a jet self-excited pulse cavitation strengthening device, the jet self-excited pulse cavitation strengthening device comprises a feed liquid storage tank, a constant temperature circulating water tank, a driving pump, a pipeline flowmeter, a jet self-excited pulse cavitation strengthening element, a feed liquid conveying pipeline, a valve for regulating and controlling feed liquid conveying flow, a pressure gauge I and a pressure gauge II for monitoring inlet pressure and outlet pressure of the jet self-excited pulse cavitation strengthening element, the driving pump is respectively communicated with the feed liquid storage tank and the inlet of the jet self-excited pulse cavitation strengthening element through the feed liquid conveying pipeline, the outlet of the jet self-excited pulse cavitation strengthening element is communicated with the inlet of the pipeline flowmeter through the feed liquid conveying pipeline, and the outlet of the pipeline flowmeter is communicated with the feed liquid storage tank through the feed liquid conveying pipeline;
the specific process flow of the step is as follows: pouring the chitosan solution obtained in the step (1) into a material liquid storage tank of a jet self-excited pulse cavitation strengthening device, starting a driving pump, regulating and controlling the inlet pressure and the outlet pressure in a jet self-excited pulse cavitation strengthening element through a valve, respectively monitoring the inlet pressure and the outlet pressure of the jet self-excited pulse cavitation strengthening element through a pressure gauge, simultaneously starting a constant-temperature circulating water tank to control the crosslinking temperature, adding the anion cross-linking agent mixed solution containing the bacteriostatic agent obtained in the step (4) into the material liquid storage tank when the device reaches the required inlet pressure, outlet pressure and crosslinking temperature, controlling the mass ratio of the anion cross-linking agent to chitosan to be 0.10-0.40, refluxing the material liquid subjected to jet self-excited pulse cavitation strengthening treatment into the storage tank, and performing continuous circulating crosslinking for 10-30 min to obtain chitosan bacteriostatic nano microspheres; the inlet pressure of the jet self-excited pulse cavitation strengthening element is controlled to be 0.15-1.2 MPa, the outlet pressure is ambient pressure, and the crosslinking temperature is controlled to be 25-60 ℃;
the jet self-excited pulse cavitation strengthening element is a throttling device with a resonant cavity in the middle, and sequentially comprises an inlet section, a contraction section, an upper nozzle jet section, a resonant cavity section, a lower nozzle jet section, an expansion section and an outlet section along the flowing direction of a material liquid; the inlet cone angle alpha of the inlet section of the jet self-excited pulse cavitation strengthening element is 30-45 degrees, the outlet cone angle beta of the outlet section is 25-90 degrees, and the diameter d of the upper nozzle1Diameter d of lower nozzle2The ratio of (a) to (b) is 0.20 to 0.86, the length of the resonant cavity (l) and the diameter (d) of the upper nozzle1The ratio of (A) to (B) is 4.5-30.0;
the resonant cavity of the jet self-excited pulse cavitation strengthening element is provided with an outlet impact section, and the cone angle gamma of the outlet impact section is 90-180 degrees.
2. The method for preparing the chitosan bacteriostatic nano-microspheres according to claim 1, which is characterized by comprising the following steps of: the molecular weight of the chitosan is 10-100 kDa, and the deacetylation degree is 60-98%.
3. The method for preparing the chitosan bacteriostatic nano-microspheres according to claim 1 or 2, which is characterized by comprising the following steps of: the post-treatment comprises centrifugation, washing and vacuum drying.
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