KR20120010867A

KR20120010867A - PVA Nano Fibrous Mats comprising Ag Nanoparticles and Preparation Method of the Same

Info

Publication number: KR20120010867A
Application number: KR1020100072501A
Authority: KR
Inventors: 이병택; 티 히엡 응우엔; 홍현진
Original assignee: 순천향대학교 산학협력단
Priority date: 2010-07-27
Filing date: 2010-07-27
Publication date: 2012-02-06

Abstract

Method for producing a fibrous mat according to the invention, the step of irradiating microwaves to a PVA (polyvinyl alcohol) and silver nitrate (AgNO ₃ ) suspension; Manufacturing a fibrous mat through electrospinning; And it comprises a process of heat-treating the manufactured fibrous mat, the fibrous mat is excellent in biocompatibility and mechanical properties, antimicrobial efficacy is recognized, it can be used in various ways as a biomaterial for tissue engineering.

Description

PVA Nano Fibrous Mats comprising Ag Nanoparticles and Preparation Method of the Same

The present invention relates to a PVA nanofibrous mat to which silver nano is added and a method of manufacturing the same.

Tissue engineering is developing across a number of fields, including biology, pharmacy, and engineering, and these fields are being improved and advanced by the reconstruction, maintenance, or enhancement of tissue. The foundation of tissue engineering in diagnostics is based on the use of living cells in a variety of ways. Tissue engineering research includes: biomaterials, cells, molecular biology, engineering design perspectives, tissue engineering informatics, stem cell research, etc. Current new biomaterials are designed from the functional tissue stage, which responds to both biological growth and physical and chemical signals, to the differentiation of cells. Cell association in the field of tissue engineering involves the development of all methods for cell proliferation and differentiation. Biomechanical perspectives in tissue engineering design include natural tissue, minimal identity to required properties, mechanical cues and efficacy to control tissue engineering, effects and safety of tissue engineering.

Electrospinning is one of the simplest methods for the preparation of fibrous mats, such as extracellular supports. Electrospinning has provided a new direction for biopolymers since it has allowed for the reduction of pore diameter from micrometers to nanometers, thereby increasing the surface area to volume or mass ratio and significantly increasing the mechanical properties of the polymer. The advantages of electrospinning have been attempted in various tissue engineering fields due to their ability to produce very thin fibers from nanometer to micrometer stages, due to their large surface area, applicability to various fields, excellent mechanical properties and ease of manufacture. In the case of an electrospinning support, the growth of cells is facilitated if they have sufficient mechanical properties. In general, the mechanical properties of the fiber increase as the inner diameter of the fiber decreases. Electrospinning supports are currently being applied to arteries, but their mechanical durability and biocompatibility have not been optimized. The structure and properties of electrospun biopolymer scaffolds are an important part of tissue engineering. Electrospun mats should be biocompatible and require mechanical properties consistent with the tissue at the implant site and biodegradable or absorbable.

In addition, wound healing is a complex process of redefining and rebuilding the skin, but bacterial overgrowth and infection interfere with this wound healing process. Therefore, artificial bases should be prepared to prevent microbial infection during wound healing.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art and the technical problems required from the past.

Specifically, it is an object of the present invention to provide a fibrous mat and a method of manufacturing the same as a biomaterial for tissue engineering.

Method for producing a fibrous mat according to the present invention for achieving this object, the step of irradiating microwaves to a suspension of polyvinyl alcohol (PVA) and silver nitrate (AgNO ₃ ); Manufacturing a fibrous mat through electrospinning; And a step of heat-treating the manufactured fibrous mat.

Polyvinyl alcohol (PVA) electrospun fibers to which silver nanoparticles (Ag NPs) according to the present invention are added may be prepared by, for example, a mixing method of microwaves and electrospinning. In addition, it is possible to increase and surface the number of silver nanoparticles present on the surface of the PVA fiber through the heat treatment process. For example, up to 50-100 nm of silver nanoparticles surfaced on PVA nanofibers when microwave treated for 60 seconds and heat treated at 150 ° C. Nanomats show bacterial inhibition and high mechanical stability (> 45 MPa).

In one embodiment, the fibrous mat includes silver nano particles having a diameter of 5 to 100 nm. The diameter of the silver nanoparticles may vary depending on the irradiation time or heat treatment temperature of the microwave, and specifically, the diameter of the silver nanoparticles may be 5 to 10 nm.

In one embodiment, the step of irradiating the microwave, characterized in that for 60-90 seconds, specifically 60-70 seconds, more specifically 60 seconds or 90 seconds. For example, when the microwave irradiation time is 60 seconds, the size of the silver nanoparticles may be 5 ~ 10 nm, in the case of 90 seconds the size of the silver nanoparticles may be 10 ~ 20 nm.

In another embodiment, the step of heat-treating the fibrous mat, characterized in that the heat treatment at a temperature of 80 ~ 150 ℃, specifically 120 ~ 150 ℃, more specifically 150 ℃. The heat treatment temperature affects the mechanical strength of the fibrous mat and the shape of the fiber.

For example, the method for producing a PVA nanofibrous mat according to the present invention may be prepared by irradiating microwaves to a PVA (polyvinyl alcohol) and silver nitrate (AgNO ₃ ) suspension for 60 seconds, followed by electrospinning, and heat treatment at 150 ° C. have.

In the present invention, an electrospun PVA mat (PVA-Ag mat) to which silver nanoparticles with electrospinning and heat treatment were added was prepared. Silver nanoparticles were surfaced on the PVA fiber surface by the heat treatment process. This mat has several advantages for skin application: First, silver (Ag) particles and their compounds are known to have specific bacterial inhibition and bactericidal properties. Silver ions exhibit bactericidal activity in the broad spectrum antimicrobial spectrum against bacteria, fungi and viruses and are known to be active in silver based antibacterial agents. Silver (Ag), on the other hand, has been widely studied as a coating material partially in medical devices such as indwelling urinary catheter and wound healing. In addition, silver nano is important for increasing the antimicrobial effect.

Secondly, PVA is a very good medium for metals with good thermal stability and chemical resistance. PVA is also non-dynamic and has high mechanical stability and degradability in the body environment. PVA, on the other hand, contains an alcohol group that can be reduced from Ag ⁺ to Ag ⁰ without a reducing material. In addition, the use of PVA as a reducing agent is a cost effective method.

Thirdly, electrospinning is the simplest method to produce continuous small diameter (nanofiber) fibers, high surface area, small pore size and mechanical properties. Due to the advantages described above, PVA-silver mats have been investigated for use in wound healing and antibacterial applications.

Fourthly, microwave irradiation is a very interesting method for producing nanometals. Microwave, an environmentally friendly method, is faster, simpler and more environmentally friendly than conventional methods such as NABH ₄ chemical reduction.

Finally, heat treatment was performed to surface the silver nanoparticles on the PVA nanofibers. For example, some nanoparticles have been shown to be evenly distributed on the surface when the heat treatment is performed at 150 ° C. The presence of silver nano was confirmed by UV-Vis, XRD, SEM and TEM. The interaction between PVA and silver nano was examined by FT-IR. The heat-crystal properties of the mat were examined by DSC. The mechanical properties also show that the mat has very high mechanical stresses that are important in wound healing. Antimicrobial experiments show that the mat has antimicrobial activity on both Gram-positive and Gram-negative, which are important for reducing infection during the wound healing process. These analyzes confirmed that PVA-Mat not only showed good mechanical properties, but also antimicrobial properties, which could reduce the risk of infection.

The present invention also provides a PVA nanofibrous mat containing silver nanoparticles. PVA nanofibrous mat according to the present invention can be produced through the method described above. In addition, it can be utilized as a biomaterial for tissue engineering, for example, the fibrous mat can be used as a biomaterial to replace skin tissue.

The fibrous mat containing the PLGA and PCL composite according to the present invention is excellent in biocompatibility and mechanical properties, antibacterial effect is recognized, and can be used in various ways as a biomaterial for tissue engineering.

1 is SEM images of PVA electrospinning mats made with different PVA solutions (weight / concentration), voltage (kV), plastic tip (mm) and solution ejection rate (mm / h).
FIG. 2 is SEM images of the PVA electrospinning mat with the addition of silver nanoparticles irradiated for a pure PVA electrospinning mat (a), microwave (b) 60 seconds and (c) 90 seconds.
FIG. 3 shows SEM images of silver-spun electrospun PVA mats with microwaves irradiated for (a) 60 seconds, (b) 90 seconds, and EDS analysis results measured in large areas in each case.
4 is a graph measuring the UV-Vis absorbance of the PVA / Ag solution according to the microwave irradiation time.
5 is an XRD analysis result of the electrospinning PVA mat to which AgNO ₃ is added and the electrospinning PVA mat to which silver nano is added.
6 is heat-treated at 80 ° C. (a), 120 ° C. (c) and 150 ° C. (e) after irradiation with microwaves for 60 seconds; SEM images of silver nano-added PVA mats heat treated at 150 ° C. (g) after microwave irradiation for 90 seconds; And magnified images, respectively.
FIG. 7 is a TEM and HRTEM image of a PVA electrospinning mat of 12 wt% PVA solution containing 2 wt% AgNO ₃ irradiated with microwave for 60 seconds (a, b) and 90 seconds (c, d).
FIG. 8 is a TEM and HRTEM image of electrospun PVA nanofibers with silver nano-irradiated with microwaves for 60 seconds and heat-treated at 150 ° C. FIG.
9 is an FT-IR analysis result of PVA powder and electrospun PVA mat to which silver nanoparticles were added before and after heat treatment.
10 is a DSC analysis result of electrospinning PVA to which silver nanoparticles of PVA powder (a), electrospinning PVA (b), before heat treatment (c) and after heat treatment (d) are added.
11 is a, e) pure PVA mat; b, f) PVA-silver mat; c, g) PVA-silver nanoparticle-2 (120 ° C.); And d, h) PVA-Ag silver nanoparticle-2 (150 ℃) is the result of analyzing the inhibition region.
12 is a result of measuring the tensile strength of the electrospinning PVA, PVA added with silver nano before and after heat treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples and the like are for illustrating the present invention, and the scope of the present invention is not limited thereto.

The present invention provides a new manufacturing method for producing a skin filler. In one embodiment, the electrospun fibrous mat is added to the silver nano according to the present invention, is produced through a process such as microwave irradiation, electrospinning and heat treatment. PVA (polyvinyl alcohol) and AgNO ₃ (99.998%) were used as initial starting materials.

Example 1 Preparation of Fibrous Mats

PVA-silver nano mats that can be applied to wound healing were prepared from PVA and silver nano suspensions after microwave irradiation for 60 seconds. The PVA-Ag mat was subjected to a heat treatment at 150 ° C. to surface the silver nano on the surface of the PVA fibers to increase the antimicrobial properties of the mat. The presence of silver nano was confirmed by SEM, TEM, XRD, EDS, FT-IR and DSC that the mat was successfully prepared by this approach. The production by electrospinning has been designed such that the mat has a high tensile force which is advantageous for skin application. Silver nano-added electrospinning PVA showed antimicrobial activity against gram positive E. coli and gram negative S. aureus . In the present invention, the method for producing an electrospun PVA mat to which silver nano is added includes three simple methods; Combination of electrospinning, microwave irradiation and low temperature process not only has high tensile strength but also shows antibacterial activity.

Experimental Example 1 Setting of Electrospinning Conditions

In order to obtain the uniformity of the PVA nanofibers and the mat of the smooth PVA surface, the effects of electrospinning conditions such as solution concentration, viscosity, voltage, collection distance, solution feed rate, and needle diameter were investigated. As a result, it was classified into four groups as shown in Table 1 below. For example, the supply rate of the PVA solution was controlled by the type of syringe pump while fixing other conditions.

[Table 1]

FIG. 1 shows SEM pictures of a fibrous mat manufactured by varying the conditions of Table 1 above.

Referring to Figure 1 in more detail, Figure 1 a) and b) is a case of varying the flow rate of the PVA solution. In comparison, the flow rate of a suitable PVA solution is 0.5 ml / hr. Under these conditions, the surface shape of the PVA mat was better, smooth and single fiber surface was observed, and there were less polymer residues. In the same way, different conditions were examined to examine the effects of other factors. When comparing b) and c) of FIG. 1, it was confirmed that the case containing 12 weight% of PVA aqueous solution is superior to the case containing 15 weight%. In addition, when comparing c) and d) of FIG. 1, the appropriate voltage was measured to be 22 kV. The diameter of the needle of the syringe pump was found to be superior to e) (0.5 mm) in FIG. 1 d (0.25 mm). As a result, the optimum electrospinning condition is that the supply rate of the voltage of 22 kV, the capillary and the electrode 12 cm, and the PVA solution through the syringe pump is 0.5 ml / hr. Confirmed.

Experimental Example 2

Based on the conditions selected in Experimental Example 1, the effect of the irradiation of microwaves in the manufacture of fibrous mat was analyzed. Specifically, (a) a PVA mat prepared by electrospinning was used as a control, 12 wt% of silver nanoparticles were added, and (b) microwave irradiation for 60 seconds and (c) microwave irradiation for 90 seconds were observed. It was. Observation results are shown in FIG. 2.

Referring to Figure 2, not only in the case of (a) without the addition of the silver nano component, but also in the case of (b) and (c) in which the nano-nano fiber is added and irradiated with microwaves, the PVA fibers showed a more uniform and smooth shape. This shows that the electrospinning conditions selected in Experimental Example 1 are appropriate conditions for both the addition and the absence of the silver nanoparticles.

[Experimental Example 3]

FIG. 3 shows the SEM shape of the electrospun PVA mat to which silver nanoparticles are added. In FIG. . Sample A exhibits a uniform nanofibrous mat consisting of 100-200 nm diameter fibers. However, Sample B shows a non-uniform nanofibrous mat composed of fibers of 100-500 nm diameter. This increases the irradiation time of the microwave, it can be seen that the diameter of the fiber is increased. That is, as the irradiation time of microwaves increases, the concentration of the polymer solution is increased due to the evaporation of water, and the diameter of the fibers is increased.

3 c and d) show the EDS profiles of Sample A and Sample B. O and C components were detected with Ag. The content of Ag was measured relative to C, H, O and Ag. The Ag content in Sample A was 9.93%, which is higher than that of Sample B which is 5.73%.

[Experimental Example 4]

In order to confirm that Ag nanoparticles are present in the PVA solution after microwave irradiation, UV absorbance of the PVA / Ag solution at different microwave irradiation times was measured. Referring to FIG. 4, the maximum absorbance appeared at 416 nm, which is a characteristic peak by Ag nanoparticles. It was confirmed that the peak appeared stronger when the microwave was irradiated for 90 seconds than when the microwave was irradiated for 60 seconds.

[Experimental Example 5]

After the microwave, experiments were conducted to confirm that Ag nanoparticles were successfully formed. For the electrospun PVA to which AgNO ₃ was added, the XRD profile was compared with and without microwave irradiation. Referring to FIG. 5, the XRD pattern of the PVA nanofibrous mat containing Ag nanoparticles showed a diffraction peak at 2θ of 38.2 °. The crystalline structure of the electrospun PVA had strong peaks at 2θ = 20.9 ° and peaks at 2θ = 19.4 °, 20.9 ° and 23.6 ° in the XRD profiles of both electrospun mats. In the XRD profile of the electrospun mat not irradiated with microwaves, the 2θ = 9.2 ° peak of crystalline PVA-Ag ⁺ was high, but the 2θ = 38.2 ° peak characteristic of Ag nanoparticles was not observed. On the other hand, in the XRD profile of the electrospun mat irradiated with microwaves, a 2θ = 38.2 ° peak was observed. These results indicate that Ag and Ag ⁺ added to PVA change the crystalline structure of electrospun PVA. In addition, it can be seen that Ag nanoparticles were successfully dispersed in PVA nanofibers through microwave and electrospinning.

Experimental Example 6

Microwave-irradiated, electrospun PVA fibers containing Ag nanoparticles were subjected to heat treatment in an oven. Heat treatment in the oven was carried out at 80 ° C, 120 ° C and 150 ° C for 24 hours.

(A), (c) and (e) of FIG. 6 are SEM shapes when PVA containing Ag nanoparticles is irradiated with microwaves for 60 seconds and then heat treated at temperatures of 80 ° C., 120 ° C. and 150 ° C., respectively. 6 (g) is the SEM shape when heat-processing at 150 degreeC after irradiating a microwave for 90 second. (B), (d), (f) and (g) of FIG. 6 are enlarged screens of (a), (c), (e) and (g) of FIG. 6, respectively.

The heat treatment process has been shown to affect the shape of the fibers. For example, when comparing (a) and (c) of FIG. 6, both were irradiated with microwave for 60 seconds and heat-treated for 24 hours, but when the temperature was changed from 80 ° C. to 120 ° C. during the heat treatment, Ag nanoparticles were used. Appeared on the fiber surface. In addition, at 150 ° C. (FIG. 6E), Ag nanoparticles appeared on the PVA fiber surface at a larger size than at 120 ° C. FIG. Figure 6 (g) is for further confirming the effect of the microwave irradiation. The number of Ag nanoparticles observed in FIG. 6 (g) was found to be less than that in FIG. 6 (e) with the same conditions but different microwave irradiation time. Through the combination of these experimental results, the optimal condition for the surface area of the Ag nanoparticles is irradiated with microwave for 60 seconds and then heat treated at 150 ℃. The results of the various surface treatment processes can be confirmed in more detail through the enlarged image.

Experimental Example 7

The effect of microwaves on PVA-Ag nanoparticles was confirmed by TEM images. 7 is TEM and HRTEM images of electrospun PVA with Ag nanoparticles. Samples were synthesized using 12 wt% PVA aqueous solution and 2 wt% AgNO ₃ , and microwave irradiation time was set differently. 7 a) and b) show the microwave irradiation for 60 seconds, and FIGS. 7 c and d) show the TEM and HRTEM images of the microwave irradiation for 90 seconds. 7 a) and b) show that the size of the Ag nanoparticles is 5 to 10 nanometers, whereas FIGS. 7 c and d) show that the size of the nanoparticles is 10 to 20 nanometers. The change from small size Ag nanoparticles to larger size Ag nanoparticles was found to be dependent on microwave irradiation time. The longer the irradiation time of the microwave, the more the electromagnetic energy is continuously converted to thermal energy, which results in an increase in heat and direct bond between the PVA and the OH group of Ag. On the other hand, by using a microwave irradiation method, Ag ⁺ is induced to be reduced to Ag ^o completely. 7 c) shows that for 90 seconds the microwave is irradiated, continuous dispersion of Ag nanoparticles is achieved. 7 b) and d) show that the size of the Ag nanoparticles increased with microwave irradiation time. It can be seen that the size of the Ag nanoparticles is larger than 5 nm (60) in microwave irradiation for 60 seconds and larger than 10 nm (90) in microwave irradiation for 90 seconds. From this, it can be seen that the Ag nanoparticles were successfully synthesized by microwave irradiation.

Experimental Example 8

FIG. 8 shows TEM and HRTEM images of Ag nanoparticle-containing PVA electrospun fibers irradiated with microwaves for 60 seconds and then heat treated at 150 ° C. FIG. TEM images show that Ag nanoparticle-containing electrospun PVA nanofibers combine from small size (5-15 nm) to larger size (about 100 nm). Ag nanoparticles are dispersed on the surface of the fibers in the form of spheres. 8 a) shows the resurfacing and aggregation of Ag nanoparticles on PVA fibers. Aggregation of Ag nanoparticles can be more clearly confirmed by HRTEM image (b) of FIG. 8). The large spherical structure is due to the aggregation of smaller Ag nanoparticles (5-10 nm).

Experimental Example 9

To test the interaction between PVA and Ag, FT-IR spectra were measured for PVA powder, PVA-Ag nanoparticle-1, and PVA-Ag nanoparticle-2 (see FIG. 9). Referring to Fig. 9, 1420 cm according to the presence of Ag nanoparticles, ^- the reduction of the peak ratio in the ^first, means for separating between the vibration that is caused by the interaction between the Ag nanoparticles and the PVA chains of -OH groups correspond. This action also applies equally to the reduction of the peak at 1141 cm ⁻¹ and is caused by steric CC stretching, corresponding to the crystalline region in the PVA. The peak at 1255 cm ⁻¹ is known to be associated with COC vibration and refers to the crosslinking of some PVA radicals.

Experimental Example 10

Thermal characteristics analysis of the PVA powder (a), the PVA electrospinning (b), the non-heat treatment (c) and the heat treatment of the PVA-Ag mat (d) were carried out at a temperature of 5 ° C./min in a nitrogen atmosphere at 0 ° C. It was carried out in the ~ 450 ℃ range. Referring to the thermogram of FIG. 10, the glass transition temperature T _g (measured by ASTM midpoint thechnique using STARe software) was observed at 75.20 ° C. and 73.39 ° C. for PVA powder and electrospun PVA mat. . The melting point, T _m , of PVA and electrospun PVA mats was observed at 226.84 ° C and 225.02 ° C, respectively. Before (c) and after (d) heat treatment of the electrospun mat containing Ag nanoparticles, T _g was not observed, but T _m was observed at 211.84 ° C and 197.54 ° C, respectively.

Experimental Example 11

Experiments to test antibacterial activity (disc diffusion method) were performed on Gram-positive E. coli and Gram-negative S. aureus . The experimental results for the inhibitory region are shown in Table 2. Each experiment was repeated four times. Figure 11 shows the degree of inhibition of microbial activity of pure PVA, PVA-Ag, NPs-1, PVA-Ag NPs-2 (120 ℃) and PVA-Ag NPs-2 (150 ℃). In pure PVA, no inhibitory region was observed, and (b, f), (c, g), and (d, h) of FIG. 11 showed high antibacterial activity against E. coli and S. aureus . The heat treatment at 120 ° C. showed a slight increase in the inhibition zone than the heat treatment at 150 ° C. PVA-Ag NPs-2 mat had the strongest antibacterial activity and Gram-positive S. aureus was Gram-negative E. coli It appeared to be more sensitive. Table 2 shows that PVA-Ag NPs-2 (150 ° C.) has the largest inhibition area. However, Gram-positive bacteria ( S. aureus ) were found to be more sensitive than those of Gram-negative bacteria ( E. coli ), showing a larger inhibition area on all electrospun PVA mats containing Ag nanoparticles.

TABLE 2

Experimental Example 12

Mechanical properties are also important for application to the skin. Therefore, the tensile strength was measured for the electrospun PVA mat, PVA-Ag NPs-1 before heat treatment and PVA-Ag NPs-2 heat treated at 150 ° C. (FIG. 12). The tensile strength curve of the PVA nanofiber mats changed after the introduction of Ag nanoparticles. Compared with the pure PVA fibrous mat, the strength was increased after the introduction of Ag nanoparticles, and the nanofibrous fibrous mat was found to be stronger and more brittle than the pure PVA fibrous mat. In the absence of heat treatment, the stress is increased from 9 MPa to 35 MPa, but in the case of heat treatment, the stress is increased to 47 MPa. However, the strains were both reduced from 23% to 15%.

Claims

Irradiating microwaves to a suspension of polyvinyl alcohol (PVA) and silver nitrate (AgNO ₃ );
Manufacturing a fibrous mat through electrospinning; And
Method for producing a PVA nanofibrous mat comprising the step of heat-treating the prepared fibrous mat.

The method of claim 1,
The fibrous mat is a method for producing a PVA nanofibrous mat containing silver nanoparticles of 5 ~ 100 nm diameter.

The method of claim 1,
The process of irradiating a microwave irradiates a microwave for 60 to 90 second, The manufacturing method of the PVA nanofiber mat.

The method of claim 1,
The step of heat-treating the fibrous mat is a method of producing a PVA nanofibrous mat, characterized in that the heat treatment at a temperature of 80 ~ 150 ℃.

The method of claim 1,
The process of irradiating microwaves irradiates microwaves for 60 seconds,
The process of heat-treating a fibrous mat is heat-processing at 150 degreeC, The manufacturing method of the PVA nanofibrous mat.

PVA nanofibrous mat prepared by the method according to any one of claims 1 to 5.

The method according to claim 6,
The fibrous mat is a PVA nano-fiber mat is a biomaterial for replacing skin tissue.