CN114832743A - Microfluidic preparation method of porous structure micron-sized polylactic acid microspheres - Google Patents

Abstract

The invention relates to a microfluidic preparation method of porous structure micron-sized polylactic acid microspheres, which combines a micro-reactor for generating liquid drops and phase separation at different temperatures. Injecting the emulsified polylactic acid emulsion into a microreactor to be used as a dispersed phase, taking a polyvinyl alcohol aqueous solution as a continuous phase, generating droplets containing emulsion raw materials under the shearing action, and controlling the phase separation process at different temperatures to finish the preparation of the porous structure micron-sized polylactic acid microspheres. The size and the dispersity of the particles and the pore channel structure can be adjusted by adjusting the flow rate, the concentration of the active agent, the components of the emulsion and different temperature treatments; the invention relates to a synthesis method for preparing polylactic acid microspheres with good dispersibility and porous structures. The preparation method disclosed by the invention is rapid in reaction, safe and easy to operate, the prepared polylactic acid microspheres are uniform in size, good in dispersity and porous in structure, the preparation effect is superior to that of the traditional emulsion industrial preparation, and the preparation method has important due value in the field of micro-nano material preparation.

Description

A kind of microfluidic preparation method of micron-scale polylactic acid microspheres with porous structure

technical field

The invention belongs to the field of preparation of polymer microspheres based on microfluidic technology, and particularly relates to a microfluidic preparation method of micro-level polylactic acid microspheres with porous structure.

Background technique

Polylactic acid has good plasticity and biocompatibility, and because of its biodegradable properties, it is widely used to prepare the matrix of functional materials, and has good applications in the fields of drug delivery, biodiagnosis, and living devices. Prospects (Fu Q, Saiz E, Rahaman M N, et al., Mater. Sci. Eng. C, 2011, 31(7): 1245-1256; Newman KD, McBurney M W, Biomaterials, 2004, 25: 5763-5771) , especially in the field of biomedicine, due to the non-toxicity, degradability and good biocompatibility of polylactic acid, it can be further applied such as cell delivery carrier, cell targeting, and tissue engineering scaffolds (Hong Y, Gong Y, Gao C, et al., J.Bio.Mater.Res.Part A, 2010, 85A(3):628-637; Duan X, Liao H X, Zou H Z, et al., Connect. tissue res., 2018, 59 (1):55-65). With the increasing application of polylactic acid in various industrial fields, there are more and more preparation methods or improvement methods for polylactic acid microspheres, a widely used material. Among the traditional preparation methods of polylactic acid microspheres, most of them are spray drying, electrospray and emulsion solvent evaporation. Generally, different preparation methods are selected according to different purposes. For example, in the process of cancer treatment, the microspheres of cancer drug carriers are required to have a small size and a suitable porous structure. Tianshi Feng et al. (Feng T, Tian H , Xu C, et al. Eur. J Pharm. Biopharm., 2014, 88(3): 1086-1093) reported that the inhalable drug-loaded microspheres prepared by electrospray method were used for the treatment of lung cancer. In addition, Yiquan Wu et al. (Wu Y, Clark R L., J.Colloid Interf.Sci., 2007, 310(2):529-535) reported the preparation of polycaprolactone with different microstructures based on electrospraying technology Ester (PCL) polymer particles, improved multiplexing reported by O'Donnell PB et al. Emulsification technology is used to prepare PLA microspheres that can encapsulate proteins and polypeptides. Electrospraying technology or electrospraying technology to prepare different microspheres, although they can achieve the required structure and size to a certain extent, but these technologies have high requirements on process equipment, and the ability to control the morphology of the microspheres is relatively weak. The uniformity of the prepared microspheres is not good. The preparation of microspheres by the emulsification method also faces the same dilemma. Although the improvement of the process can effectively improve the preparation efficiency of the product, the increase in the complexity of the process is not friendly to the daily process production, and the process complexity is increased. The improvement of the effect is also limited, which further reduces the preparation efficiency and increases the preparation cost. In the process of microsphere preparation, the control of size uniformity and the control of morphology construction are practical problems. Although many optimized processes have been developed, they have not fundamentally solved the problem of low control accuracy and stable preparation results. Bad question. It is of great practical significance to explore a preparation process that can precisely control the size, stably build the morphology, and meet the requirements of high efficiency and low cost for the preparation of porous micron-sized polylactic acid microspheres.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a microfluidic control preparation method of porous structure micron-level polylactic acid microspheres, polylactic acid, gelatin and Span80 are dissolved in methylene chloride as a dispersed phase, and polyvinyl alcohol is dissolved in water as a continuous phase , through a microreactor to generate dichloromethane emulsion droplets mixed with polylactic acid and gelatin, and the droplets are treated at different temperatures to gradually guide the volatilization of dichloromethane and the dissolution of gelatin to complete the porous structure of micron-scale polylactic acid microspheres. preparation. The polylactic acid microspheres prepared by the method have uniform particle size, good dispersibility and stable structure, and can effectively meet the application requirements of functional polylactic acid microspheres.

For achieving the above object, the present invention adopts the following scheme to realize:

A microfluidic preparation method of porous structure micron-scale polylactic acid microspheres, comprising the following steps:

1) select and contain 0.05～0.1wt% polyvinyl alcohol aqueous solution as continuous phase, polyvinyl alcohol is used as surfactant, and the flow rate of microreactor is set to 1.5～2.5mL/min; Lactic acid and Span80 are dissolved in methylene chloride, and the emulsion prepared after mixing and stirring the two is used as a dispersed phase, wherein the mass fractions of polyvinyl alcohol and gelatin soluble in water are 0.5-1.5 wt% and 3-8 wt% respectively, polylactic acid, The mass fractions of Span80 dissolved in dichloromethane are 1.5-2.5wt% and 2.5-3.5wt% respectively, the mass ratio of water to dichloromethane is 1:3; the flow rate of the dispersed phase in the microreactor is set to 30 ~50μL/min;

2) Collect the droplets and collect them in a large beaker in an ice-water bath, and process them in three stages. First, stand still for 1-2 minutes, absorb the aqueous solution in the upper layer, until the liquid level is 0.5-1cm higher than the droplets, and retain the micro-droplets in the bottom layer. Drop and submerge the upper layer of aqueous solution with a height of 0.5-1 cm in the droplets, keep the ice-water bath and let stand for 5-6 hours; then, take out the container for collecting the micro-droplets, and place them in a water bath at 30-35 °C for 1-2 hours; In a 40-45°C water bath, stir and continue the water bath for 1-2 hours; filter with a 200-300 mesh sieve to obtain microspheres, and rinse with 40-45°C water for 3-5 times, collect the microspheres, and freeze-dry to obtain the final porous structure micrometer grade polylactic acid microspheres.

A further improvement of the present invention is that, in step 1), the material of the microreactor is selected from PTFE or plexiglass; the included angle of the channel for adding raw materials is 90°, and the channel is selected from PTFE tube.

A further improvement of the present invention is that the microreactor is prepared by injection molding technology, the surface roughness of the microreactor channel is less than 10 μm, and the injection dimension error of the microreactor is less than 5%.

A further improvement of the present invention is that the cross-sectional openings of the microreactors are uniformly circular, with a diameter of 600 μm; the inner diameter of the PTFE tube is 600 μm; the microreactor and the PTFE tube are connected through a Luer joint to ensure tightness.

A further improvement of the present invention is that in step 1), the stirring speed of the generated emulsion is set to be 2000-3000 r/min, and the stirring time is set to be 25-30 min.

A further improvement of the present invention is that in step 1), the flow rate ratio of the continuous phase and the dispersed phase is 30:1 to 80:1.

A further improvement of the present invention is that, in step 1), 3% to 8% of gelatin is added as a pore-forming agent.

A further improvement of the present invention is that, in step 2), the large beaker for collecting the microspheres absorbs most of the water in the upper layer, directly places it in an ice-water bath for 5-6 hours, then directly takes it out, and places it at 30-35° C. Water bath for 1 to 2 hours; then take it out directly, place it in a water bath at 40 to 45°C, stir and continue the water bath for 1 to 2 hours.

A porous structure micron-level polylactic acid microsphere is prepared by using the preparation method.

The present invention at least has the following beneficial technical effects:

The invention provides a microfluidic control preparation method of porous structure micron-scale polylactic acid microspheres. The preparation method designs a microreactor including droplet generation, and converts polylactic acid emulsion containing pore-forming agent gelatin into liquid of uniform size. Drop, adjusting the concentration of gelatin can adjust the size of the pore size; in the present invention, a certain concentration of polyvinyl alcohol is introduced as the surfactant of the water phase, and Span80 is introduced as the surfactant of the oil phase, and the active agent reduces the continuous phase and dispersion. The surface tension of the phase surface, in which polyvinyl alcohol with a concentration of 0.05wt% to 0.1wt% and Span with a concentration of 3wt% to 8wt% can effectively adjust the uniformity of the generated droplets, thereby regulating the uniformity of the microspheres (Fig. 4); The invention introduces a three-stage temperature post-treatment method, absorbs the excess aqueous solution in the upper layer and uses low temperature in an ice-water bath to slowly volatilize the organic solvent dichloromethane to ensure the morphology of the microspheres is stable, and the treatment at 30-35°C can ensure the organic solvent. The volatilization of the solvent is complete and the shape of the microspheres is stable. Treatment at 40-45°C can effectively dissolve the pore-forming agent gelatin in the water phase to complete the preparation of the pore structure; changing the flow rate, pore-forming agent concentration, surfactant concentration and When the parameters such as different temperatures are processed in the subsequent process, the size, uniformity and pore structure of the microspheres can be effectively adjusted, and the size difference caused by the preparation of emulsion droplets by the traditional double emulsification method can be effectively avoided; the polylactic acid microspheres prepared by the present invention are uniform in size. , the size distribution is in the range of 200 μm to 250 μm, the uniformity is good, it has a multi-level pore structure, and the pore size is adjustable in the range of 20 μm to 150 μm (Figure 3, Figure 4, Figure 5), and the present invention is simple and efficient, and easy to implement Industrial production.

Description of drawings

Figure 1 is a schematic structural diagram of a microreactor designed in the present invention.

Fig. 2 is the SEM image, the particle size distribution statistics diagram and the pore size statistics diagram of the porous structure micron-level polylactic acid microspheres obtained in Design Example 1 of the present invention.

3 is a SEM image, a particle size distribution statistics diagram and a pore size statistics diagram of the porous structure micron-level polylactic acid microspheres obtained in Design Example 5 of the present invention.

FIG. 4 is a SEM image, a particle size distribution statistics diagram and a pore size statistics diagram of the porous structure micron-level polylactic acid microspheres prepared in Design Example 7 of the present invention.

5 is a SEM image, a particle size distribution statistics diagram and a pore size statistics diagram of the porous structure micron-scale polylactic acid microspheres prepared in Design Example 8 of the present invention.

Detailed ways

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be more thoroughly understood, and will fully convey the scope of the present disclosure to those skilled in the art. It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

Example 1

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 4g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerically controlled micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.1g of gelatin and dissolve in 2g of water, weigh 0.12g of polylactic acid and 0.18g of Span80 and dissolve in 6g of methylene chloride. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 2 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 40 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, first, let stand for 2 minutes, and then absorb a large amount of aqueous solution in the upper layer until the liquid level is 1 cm higher than the micro droplets, and retain the micro droplets at the bottom layer and the upper layer aqueous solution that submerges the micro droplets 1 cm high. liquid, keep an ice-water bath and let stand for 5-6 hours; then, take out the large beaker that collects the droplets, and place it in a 35°C water bath for 1-2 hours; finally, raise the temperature to 45°C, slowly stir and continue the water bath for 2 hours; use a 200-mesh sieve The microspheres are obtained by filtration, rinsed with 45° C. water for 3 to 5 times, the microspheres are collected, and freeze-dried to obtain the final porous structure micron-level polylactic acid microspheres.

Embodiment 2

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 4g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerically controlled micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.1g of gelatin and dissolve in 2g of water, weigh 0.12g of polylactic acid and 0.18g of Span80 and dissolve in 6g of methylene chloride. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 2 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 40 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, keep the ice-water bath and let it stand for 5-6 hours; take out the large beaker for collecting the micro-droplets and place it in a water bath at 35°C for 1-2 hours; raise the temperature to 45°C, stir slowly and continue the water bath for 2 hours; The microspheres are obtained by filtration with a 200-mesh sieve, and rinsed with 45° C. water for 3 to 5 times, the microspheres are collected, and freeze-dried to obtain the final porous structure micron-level polylactic acid microspheres.

Embodiment 3

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 4g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerically controlled micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.1g of gelatin and dissolve in 2g of water, weigh 0.12g of polylactic acid and 0.18g of Span80 and dissolve in 6g of methylene chloride. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 2 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 40 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, first, let stand for 2 minutes, and then absorb a large amount of aqueous solution in the upper layer until the liquid level is 1 cm higher than the micro droplets, and retain the micro droplets at the bottom layer and the upper layer aqueous solution that submerges the micro droplets 1 cm high. liquid, keep an ice-water bath and let stand for 5-6 hours; raise the temperature to 45°C, slowly stir and continue the water bath for 2 hours; filter through a 200-mesh sieve to obtain microspheres, rinse with 45°C water for 3-5 times, collect the microspheres, freeze-dried, The final porous structure micron-scale polylactic acid microspheres are obtained.

Embodiment 4

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 4g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerically controlled micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.1g of gelatin and dissolve in 2g of water, weigh 0.12g of polylactic acid and 0.18g of Span80 and dissolve in 6g of methylene chloride. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 2 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 40 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, keep the ice water bath and let stand for 5-6 hours; then, heat up to 45°C, slowly stir and continue the water bath for 2 hours; filter with a 200-mesh sieve to obtain microspheres, and rinse with 45°C water for 3-6 hours 5 times, the microspheres were collected and lyophilized to obtain the final porous structure micron-scale polylactic acid microspheres.

Embodiment 5

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 2g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerical control micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.1g of gelatin and dissolve in 2g of water, weigh 0.12g of polylactic acid and 0.18g of Span80 and dissolve in 6g of methylene chloride. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 2 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 40 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, first, let stand for 2 minutes, and then absorb a large amount of aqueous solution in the upper layer until the liquid level is 1 cm higher than the micro droplets, and retain the micro droplets at the bottom layer and the upper layer aqueous solution that submerges the micro droplets 1 cm high. liquid, keep an ice-water bath and let stand for 5-6 hours; then, take out the large beaker that collects the droplets, and place it in a 35°C water bath for 1-2 hours; finally, raise the temperature to 45°C, slowly stir and continue the water bath for 2 hours; use a 200-mesh sieve The microspheres are obtained by filtration, rinsed with 45° C. water for 3 to 5 times, the microspheres are collected, and freeze-dried to obtain the final porous structure micron-level polylactic acid microspheres.

Embodiment 6

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 4g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerically controlled micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.1g of gelatin and dissolve in 2g of water. Weigh 0.12g of polylactic acid and 0.48g of Span80 and dissolve in 6g of dichloromethane. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 2 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 40 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, first, let stand for 2 minutes, and then absorb a large amount of aqueous solution in the upper layer until the liquid level is 1 cm higher than the micro droplets, and retain the micro droplets at the bottom layer and the upper layer aqueous solution that submerges the micro droplets 1 cm high. liquid, keep an ice-water bath and let stand for 5-6 hours; then, take out the large beaker that collects the droplets, and place it in a 35°C water bath for 1-2 hours; finally, raise the temperature to 45°C, slowly stir and continue the water bath for 2 hours; use a 200-mesh sieve The microspheres are obtained by filtration, rinsed with 45° C. water for 3 to 5 times, the microspheres are collected, and freeze-dried to obtain the final porous structure micron-level polylactic acid microspheres.

Embodiment 7

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 4g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerically controlled micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.06g of gelatin and dissolve in 2g of water. Weigh 0.12g of polylactic acid and 0.18g of Span80 and dissolve in 6g of methylene chloride. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 2 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 40 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, first, let stand for 2 minutes, and then absorb a large amount of aqueous solution in the upper layer until the liquid level is 1 cm higher than the micro droplets, and retain the micro droplets at the bottom layer and the upper layer aqueous solution that submerges the micro droplets 1 cm high. liquid, keep an ice-water bath and let stand for 5-6 hours; then, take out the large beaker that collects the droplets, and place it in a 35°C water bath for 1-2 hours; finally, raise the temperature to 45°C, slowly stir and continue the water bath for 2 hours; use a 200-mesh sieve The microspheres are obtained by filtration, rinsed with 45° C. water for 3 to 5 times, the microspheres are collected, and freeze-dried to obtain the final porous structure micron-level polylactic acid microspheres.

Embodiment 8

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 4g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerically controlled micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.16g of gelatin and dissolve in 2g of water. Weigh 0.12g of polylactic acid and 0.18g of Span80 and dissolve in 6g of methylene chloride. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 2 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 40 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, first, let stand for 2 minutes, and then absorb a large amount of aqueous solution in the upper layer until the liquid level is 1 cm higher than the micro droplets, and retain the micro droplets at the bottom layer and the upper layer aqueous solution that submerges the micro droplets 1 cm high. liquid, keep an ice-water bath and let stand for 5-6 hours; then, take out the large beaker that collects the droplets, and place it in a 35°C water bath for 1-2 hours; finally, raise the temperature to 45°C, slowly stir and continue the water bath for 2 hours; use a 200-mesh sieve The microspheres are obtained by filtration, rinsed with 45° C. water for 3 to 5 times, the microspheres are collected, and freeze-dried to obtain the final porous structure micron-level polylactic acid microspheres.

Embodiment 9

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 4g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerically controlled micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.1g of gelatin and dissolve in 2g of water, weigh 0.12g of polylactic acid and 0.18g of Span80 and dissolve in 6g of methylene chloride. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 1.5 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 30 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, first, let stand for 2 minutes, and then absorb a large amount of aqueous solution in the upper layer until the liquid level is 1 cm higher than the micro droplets, and retain the micro droplets at the bottom layer and the upper layer aqueous solution that submerges the micro droplets 1 cm high. liquid, keep an ice-water bath and let stand for 5-6 hours; then, take out the large beaker that collects the droplets, and place it in a 35°C water bath for 1-2 hours; finally, raise the temperature to 45°C, slowly stir and continue the water bath for 2 hours; use a 200-mesh sieve The microspheres are obtained by filtration, rinsed with 45° C. water for 3 to 5 times, the microspheres are collected, and freeze-dried to obtain the final porous structure micron-level polylactic acid microspheres.

Embodiment ten

1) Preparation of microreactor: PTFE microreactor was prepared by injection molding technology. The cross-sectional opening of the microchannel was uniform and circular, and the diameter was 600 μm; the included angle of the channel for adding raw materials was 90°; The outer diameter is 1mm, the PTFE tube is connected with the microreactor through a Luer connector, and the other end is inserted into the conical flask of the ice-water bath;

2) Weigh 4g of polyvinyl alcohol and dissolve it in 400mL, take the polyvinyl alcohol aqueous solution as the continuous phase, suck it into a 50mL syringe, and fix the syringe on the numerically controlled micropump;

3) Weigh 0.02g of polyvinyl alcohol and 0.1g of gelatin and dissolve in 2g of water, weigh 0.12g of polylactic acid and 0.18g of Span80 and dissolve in 6g of methylene chloride. Set it to 3000r/min, set the stirring time to 30min, suck the emulsion into a 5mL syringe, and then fix it on the numerical control micropump;

4) The flow rate of the micropump of the polyvinyl alcohol aqueous solution as the continuous phase is set to 2.5 mL/min; the flow rate of the micropump of the emulsion as the dispersed phase is set to 50 μL/min;

5) Put 20mL polyvinyl alcohol aqueous solution in a large beaker, and place the large beaker in an ice-water bath. After the temperature is stable, first connect the outlet conduit to the beaker containing the polyvinyl alcohol aqueous solution, and open the continuous phase micropump. , firstly feed the polyvinyl alcohol aqueous solution for 1 min, then open the dispersed phase micropump, and feed the emulsion, and after the droplets are stabilized, connect the catheter to the large beaker of the ice-water bath;

5) After collecting the generated droplets, first, let stand for 2 minutes, and then absorb a large amount of aqueous solution in the upper layer until the liquid level is 1 cm higher than the micro droplets, and retain the micro droplets at the bottom layer and the upper layer aqueous solution that submerges the micro droplets 1 cm high. liquid, keep an ice-water bath and let stand for 5-6 hours; then, take out the large beaker that collects the droplets, and place it in a 35°C water bath for 1-2 hours; finally, raise the temperature to 45°C, slowly stir and continue the water bath for 2 hours; use a 200-mesh sieve The microspheres are obtained by filtration, rinsed with 45° C. water for 3 to 5 times, the microspheres are collected, and freeze-dried to obtain the final porous structure micron-level polylactic acid microspheres.

Although the present invention has been described in detail above with general description and specific embodiments, some modifications or improvements can be made on the basis of the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention fall within the scope of the claimed protection of the present invention.

Claims (9)

1. a microfluidic control preparation method of porous structure micron-level polylactic acid microspheres, is characterized in that, comprises the following steps: 1) select and contain 0.05～0.1wt% polyvinyl alcohol aqueous solution as continuous phase, polyvinyl alcohol is used as surfactant, and the flow rate of microreactor is set to 1.5～2.5mL/min; Lactic acid and Span80 are dissolved in methylene chloride, and the emulsion prepared after mixing and stirring the two is used as a dispersed phase, wherein the mass fractions of polyvinyl alcohol and gelatin soluble in water are 0.5-1.5 wt% and 3-8 wt% respectively, polylactic acid, The mass fractions of Span80 dissolved in dichloromethane are 1.5-2.5wt% and 2.5-3.5wt% respectively, the mass ratio of water to dichloromethane is 1:3; the flow rate of the dispersed phase in the microreactor is set to 30 ~50μL/min; 2) Collect the droplets and collect them in a large beaker in an ice-water bath, and process them in three stages. First, stand still for 1-2 minutes, absorb the aqueous solution in the upper layer, until the liquid level is 0.5-1cm higher than the droplets, and retain the micro-droplets in the bottom layer. Drop and submerge the upper layer of aqueous solution with a height of 0.5-1 cm in the droplets, keep the ice-water bath and let stand for 5-6 hours; then, take out the container for collecting the micro-droplets, and place them in a water bath at 30-35 °C for 1-2 hours; In a 40-45°C water bath, stir and continue the water bath for 1-2 hours; filter with a 200-300 mesh sieve to obtain microspheres, and rinse with 40-45°C water for 3-5 times, collect the microspheres, and freeze-dry to obtain the final porous structure micrometer grade polylactic acid microspheres. 2. the microfluidic control preparation method of a kind of porous structure micron-level polylactic acid microspheres according to claim 1, is characterized in that, in step 1), the material of microreactor selects PTFE or plexiglass; The included angle is 90°, and the channel is made of PTFE tube. 3. the microfluidic control preparation method of a kind of porous structure micron-level polylactic acid microspheres according to claim 2, is characterized in that, described microreactor adopts injection molding technology to prepare, and microreactor channel surface roughness is less than 10μm, the injection size error of the microreactor is less than 5%. 4. the microfluidic control preparation method of a kind of porous structure micron-level polylactic acid microspheres according to claim 2, is characterized in that, the microreactor cross-sectional openings are uniformly circular, and the diameter size is 600 μm; the inner diameter of the PTFE tube 600μm; the microreactor is connected with the PTFE tube through a luer joint to ensure tightness. 5. the microfluidic control preparation method of a kind of porous structure micron-level polylactic acid microspheres according to claim 1, is characterized in that, in step 1), the stirring setting stirring speed of the generated emulsion is 2000～3000r/ min, and the stirring time was set to 25-30 min. 6. the microfluidic control preparation method of a kind of porous structure micron-level polylactic acid microspheres according to claim 1, is characterized in that, in step 1), the flow rate ratio of continuous phase and dispersed phase is 30:1～80 :1. 7 . The microfluidic control preparation method of porous structure micron-level polylactic acid microspheres according to claim 1 , wherein, in step 1), the added 3% to 8% gelatin is used as a pore-forming agent. 8 . 8. the microfluidic control preparation method of a kind of porous structure micron-level polylactic acid microspheres according to claim 1, is characterized in that, in step 2), after the large beaker that collects microspheres will absorb the water of the uppermost part, Put it directly in an ice-water bath for 5-6 hours, then directly take it out, put it in a 30-35°C water bath for 1-2 hours; then take it out directly, place it in a 40-45°C water bath, stir and continue the water bath for 1-2 hours. 9. A porous structure micron-level polylactic acid microsphere, prepared by the preparation method according to any one of claims 1 to 8.

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