CN106498559B - A kind of method that nanofiber is self-assembled into using small-molecular-weight sodium alginate - Google Patents

Abstract

The invention discloses a method for self-assembling nanofibers by using sodium alginate with small molecular weight, which comprises the following steps: first degrade sodium alginate with large molecular weight into sodium alginate with small molecular weight; Add deionized water to dissolve; finally, let the sodium alginate solution stand still, and obtain sodium alginate nanofibers stored in the solution system through self-assembly. That is, self-assembly occurs through degradation, solubilization, and aggregation of small-molecular-weight sodium alginate molecular chains. After multi-stage self-assembly, seaweed that is uniformly dispersed and can be used to prepare high-strength, good thixotropic hydrogels is obtained. NaCl nanofibers. The invention can self-assemble into nanofibers by simply adjusting the molecular weight of sodium alginate without adding any cross-linking agent or electrolyte salt. The preparation method is simple, direct and efficient. In particular, the as-prepared sodium alginate nanofibers were "pure" sodium alginate components.

Description

A method of self-assembling nanofibers using small molecular weight sodium alginate

technical field

The invention relates to a method for preparing sodium alginate nanofibers, in particular to a method for self-assembling nanofibers using small molecular weight sodium alginate.

Background technique

Sodium alginate (Sodium Alginate, SA), also known as sodium alginate, is composed of β-D-mannuronic acid (M segment) and α-L-guluronic acid (G segment) through 1-4 glycosidic bonds Linked natural linear polymers.

Because sodium alginate has good biocompatibility, degradability, strong hygroscopicity and hemostatic properties, it has broad application prospects in drug release and tissue engineering. Among them, the nanofibers made of sodium alginate have high utilization value in the fields of tissue engineering and drug release due to their very high volume-to-surface area ratio.

In the prior art, sodium alginate nanofibers can only be prepared by electrospinning.

Because the molecular chain of sodium alginate is rigid and stretches in the solution, and lacks the necessary chain entanglement, in the preparation of its electrospinning solution, it is often necessary to add a cross-linking agent or a large amount of water-soluble flexible material to the sodium alginate solution system. Polymers can make the viscosity of the sodium alginate spinning solution meet the process requirements of electrospinning, thereby ensuring the smooth progress of electrospinning.

It is not difficult to see that the main problems or shortcomings of electrospinning are: First, the preparation process of the spinning solution is complicated and the control of the process parameters is difficult. Correspondingly, the product quality (performance indicators, fiber morphology, etc.) Second, the cost of electrospinning equipment is high and the operating cost is relatively high; third, the diameter of the prepared nanofibers is relatively large, generally above several hundred nanometers. Strictly speaking, it cannot be called "nano" fiber.

Contents of the invention

The purpose of the present invention is to provide a short process flow, simple and easy to control process, energy saving and environmental protection, simple instruments/equipment required, low preparation cost, good product quality, and easy long-term preservation using small molecular weight sodium alginate self-assembled nanofiber approach.

The technical scheme adopted by the present invention to achieve the above object is a method for self-assembling nanofibers using small molecular weight sodium alginate, which is characterized in that it comprises the following steps:

The first step, the preparation of the sodium alginate of small molecular weight:

In proportion, sodium alginate with a large molecular weight is added to deionized water, swelled and dissolved by stirring, and a sodium alginate solution A with a concentration of 1.5% by mass is obtained;

Then, hydrogen peroxide is added to obtain a mixed solution, and the mass fraction of hydrogen peroxide in the mixed solution is 1.5% to 2%;

Heat the mixed solution to 65°C in a water bath, and stir for 1h to 15h;

Then, according to the volume ratio of the mixed solution and absolute ethanol being 1:2, add absolute ethanol to the mixed solution, precipitate and centrifuge to obtain a solid with small molecular weight sodium alginate as the main component;

Dissolve the obtained solids in deionized water, and then sequentially undergo dialysis and freeze-drying to obtain relatively pure small molecular weight sodium alginate powder;

The second step, sodium alginate nanofiber self-assembly step:

Dissolving the obtained small molecular weight sodium alginate powder in deionized water while stirring to obtain a sodium alginate solution B with a concentration of 5% to 60% by mass;

In the third step, the obtained sodium alginate solution B is left to stand for 2h to 120h to self-assemble into sodium alginate nanofibers;

The above-mentioned sodium alginate with large molecular weight refers to sodium alginate with a weight average molecular weight of 313kDa～586kDa;

The above-mentioned sodium alginate with low molecular weight refers to sodium alginate with a weight average molecular weight of 23kDa-96kDa.

The technical effect directly brought by the above-mentioned technical solution is that the molecular weight of sodium alginate can be sensibly adjusted, without adding any cross-linking agent or electrolyte salt, and the nanofibers can be self-assembled by using small-molecular-weight sodium alginate. The preparation method is simple, direct and efficient. In particular, the prepared sodium alginate nanofibers are "pure" sodium alginate components, which retain the excellent properties of sodium alginate such as degradability and compatibility.

It is not difficult to see that the preparation method of the above technical solution has a short process flow, a simple and easy-to-control process, energy saving and environmental protection, simple instruments/equipment required, low preparation cost, good product quality, and is convenient for long-term storage.

In order to better understand the technical features of the present invention, a detailed explanation and description will be given below in principle.

Sodium alginate is easily soluble in water. However, due to the constraints of the high viscosity characteristic of sodium alginate polymer, its solubility is low. When it is in an aqueous solution system, when the concentration of (sodium alginate) reaches a certain level, gelation will occur. This is the root cause of the limited solubility of sodium alginate in water.

Based on the understanding of the above objective laws, we found in the research that when the molecular weight of sodium alginate is greatly reduced to a certain range through degradation, not only the solubility of sodium alginate in water will increase significantly; moreover, the molecular chain of sodium alginate After shortening, its rigidity is greatly enhanced; when the concentration of this sodium alginate in the aqueous solution reaches a certain critical value, the molecular chains of sodium alginate will undergo orientation aggregation, thereby self-assembling to form a new structure, that is, nanofibers .

It should be pointed out that the sodium alginate nanofibers prepared by the preparation method of the above technical solution can be uniformly dispersed/stored in the solution system for a long time and stably (no additional "separation" steps are required), so it is convenient for storage. the reason is:

The transformation process of sodium alginate from random coil structure to nanofiber structure in aqueous solution is a process from disorder to order, which is a process of entropy reduction.

In this process, because the molecular weight of sodium alginate decreases, the solubility increases greatly, and a large amount of sodium alginate gathers together, so the hydrophobic effect of sodium alginate increases, and the hydrophobic effect provides energy, making part of the molecular chain of sodium alginate It is tightly combined with the molecular chain of sodium alginate to form a new structure, that is, the nanofiber structure;

The nanofibrous structure is a stable structure. If the nanofibrous structure is to be changed back to the original random coil structure, energy must be provided to combine with hydrophobic interactions.

Assuming that the nanofibers are to be reassembled (to grow thicker and larger), it is still a process of entropy reduction, which also requires external energy.

Therefore, the structure of the sodium alginate nanofibers in the solution system prepared by the above technical scheme is stable, and its destruction process is non-spontaneous.

That is to say, the preparation method of the above technical solution, the prepared sodium alginate nanofibers can be uniformly dispersed/stored in the solution system for a long time and stably, which has a theoretical basis and is reliable.

Preferably, the above-mentioned method for self-assembling nanofibers using low-molecular-weight sodium alginate is characterized in that the prepared sodium alginate nanofibers have a diameter of 50nm-800nm and a length of 3000nm-20000nm.

The technical effect directly brought by this optimal technical solution is that the sodium alginate nanofibers have a diameter of 50nm to 800nm and a length of 3000nm to 20000nm, which are suitable for preparing hydrogels with high strength and good thixotropy, and have very broad market application prospects .

Based on the above analysis, it is not difficult to understand that the technical key points of the present invention include: rationally controlling the molecular weight, concentration and assembly time of sodium alginate.

In summary, compared with the prior art, the present invention has the beneficial effects of short process flow, simple process, easy control, energy saving and environmental protection, simple instruments/equipment required, low preparation cost, good product quality, and convenient long-term storage.

Description of drawings

Fig. 1 is a schematic diagram of the self-assembly principle of the present invention;

Fig. 2 is the transmission electron micrograph of the sodium alginate nanofiber that embodiment 2 makes.

Detailed ways

The present invention will be described in detail below in conjunction with the embodiments.

illustrate:

1. In the following examples, the sodium alginate raw materials used (that is, the "high molecular weight sodium alginate") are all commercially available products; both H ₂ O ₂ and absolute ethanol are commercially available products.

2. In the following examples, the molecular weights of "sodium alginate with large molecular weight" and "sodium alginate with small molecular weight" are all measured by gel permeation chromatography (GPC).

3. In the following examples, the morphology of sodium alginate nanofibers is the observation result under the polarizing microscope; the fiber diameter and fiber length are the observation results under the transmission electron microscope.

Example 1

The preparation method comprises three steps as shown in Figure 1:

The first step, the preparation of the sodium alginate of small molecular weight:

Proportionally, high molecular weight sodium alginate (weight average molecular weight is 313kDa) was added into deionized water, swelled and dissolved by stirring to obtain a sodium alginate solution A with a concentration of 1.5% by mass;

Then, add hydrogen peroxide to obtain a mixed solution, the mass fraction of hydrogen peroxide in the mixed solution is 1.5%;

Heat the mixed solution to 65°C in a water bath, and stir for 12 hours;

Then, according to the volume ratio of the mixed solution and absolute ethanol being 1:2, add absolute ethanol to the mixed solution, precipitate and centrifuge to obtain a solid with small molecular weight sodium alginate as the main component;

The resulting solid was dissolved in deionized water, followed by dialysis and freeze-drying to obtain a relatively pure small molecular weight sodium alginate powder (weight average molecular weight: 74kDa);

The second step, sodium alginate nanofiber self-assembly step:

Dissolving the obtained sodium alginate powder with a small molecular weight in deionized water while stirring to obtain a sodium alginate solution B with a concentration of 10% by mass;

In the third step, the obtained sodium alginate solution B was left to stand for 72 hours to self-assemble into sodium alginate nanofibers.

The obtained products were observed under a polarizing microscope and a transmission electron microscope respectively, and the results showed that the sodium alginate nanofibers were linear or branched; the diameter of the nanofibers was 140-150nm, and the length was 3500-3700nm.

Example 2

The preparation method comprises three steps as shown in Figure 1:

The first step, the preparation of the sodium alginate of small molecular weight:

In proportion, sodium alginate with a large molecular weight (weight-average molecular weight of 586kDa) was added to deionized water, swelled and dissolved by stirring, to obtain a sodium alginate solution A with a concentration of 1.5% by mass;

Then, add hydrogen peroxide to obtain a mixed solution, the mass fraction of hydrogen peroxide in the mixed solution is 1.5%;

Heat the mixed solution to 65°C in a water bath, and stir for 15 hours;

Then, according to the volume ratio of the mixed solution and absolute ethanol being 1:2, add absolute ethanol to the mixed solution, precipitate and centrifuge to obtain a solid with small molecular weight sodium alginate as the main component;

The resulting solid was dissolved in deionized water, followed by dialysis and freeze-drying to obtain relatively pure small molecular weight sodium alginate powder (weight average molecular weight: 95kDa);

The second step, sodium alginate nanofiber self-assembly step:

Dissolving the obtained sodium alginate powder with a small molecular weight in deionized water while stirring to obtain a sodium alginate solution B with a concentration of 10% by mass;

In the third step, the obtained sodium alginate solution B was left to stand for 120 hours to self-assemble into sodium alginate nanofibers.

The resulting product was observed under a polarizing microscope, and the results showed that the morphology of sodium alginate nanofibers was linear or branched;

Observing the obtained product under a transmission electron microscope shows that the diameter of the nanofiber is 50-65nm and the length is 3200-3500nm.

Figure 2 is a transmission electron micrograph of the prepared sodium alginate nanofibers. The obvious fiber structure can be seen from Figure 2, which indicates that the obtained product is a nanofiber.

Example 3

The preparation method comprises three steps as shown in Figure 1:

The first step, the preparation of the sodium alginate of small molecular weight:

In proportion, sodium alginate with a large molecular weight (weight-average molecular weight of 425kDa) was added to deionized water, swelled and dissolved by stirring to obtain a sodium alginate solution A with a concentration of 1.5% by mass;

Then, add hydrogen peroxide to obtain a mixed solution, the mass fraction of hydrogen peroxide in the mixed solution is 1.5%;

Heat the mixed solution to 65°C in a water bath, and stir for 5 hours;

Then, according to the volume ratio of the mixed solution and absolute ethanol being 1:2, add absolute ethanol to the mixed solution, precipitate and centrifuge to obtain a solid with small molecular weight sodium alginate as the main component;

The resulting solid was dissolved in deionized water, followed by dialysis and freeze-drying to obtain a relatively pure sodium alginate powder with a small molecular weight (weight-average molecular weight of 86kDa);

The second step, sodium alginate nanofiber self-assembly step:

Dissolving the obtained sodium alginate powder with a small molecular weight in deionized water while stirring to obtain a sodium alginate solution B with a concentration of 10% by mass;

In the third step, the obtained sodium alginate solution B was left to stand for 96 hours to self-assemble into sodium alginate nanofibers.

Observing the obtained product under a polarizing microscope and a transmission electron microscope respectively, it can be seen that the appearance of the sodium alginate nanofiber is linear or branched; the diameter of the nanofiber is 55-70nm, and the length is 4200-4500nm.

Example 4

The preparation method comprises three steps as shown in Figure 1:

The first step, the preparation of the sodium alginate of small molecular weight:

In proportion, sodium alginate with a large molecular weight (weight-average molecular weight of 505 kDa) was added to deionized water, swelled and dissolved by stirring to obtain a sodium alginate solution A with a concentration of 1.5% by mass;

Then, add hydrogen peroxide to obtain a mixed solution, the mass fraction of hydrogen peroxide in the mixed solution is 1.5%;

Heat the mixed solution to 65°C in a water bath, and stir for 8 hours;

Then, according to the volume ratio of the mixed solution and absolute ethanol being 1:2, add absolute ethanol to the mixed solution, precipitate and centrifuge to obtain a solid with small molecular weight sodium alginate as the main component;

The resulting solid was dissolved in deionized water, followed by dialysis and freeze-drying to obtain a relatively pure sodium alginate powder with a small molecular weight (weight-average molecular weight of 91kDa);

The second step, sodium alginate nanofiber self-assembly step:

Dissolving the obtained sodium alginate powder with a small molecular weight in deionized water while stirring to obtain a sodium alginate solution B with a concentration of 10% by mass;

In the third step, the obtained sodium alginate solution B was left to stand for 72 hours to self-assemble into sodium alginate nanofibers.

Observing the obtained product under a polarizing microscope and a transmission electron microscope respectively, it can be seen that the appearance of the sodium alginate nanofiber is linear or branched; the diameter of the nanofiber is 165-180nm, and the length is 4000-4500nm.

Example 5

The preparation method comprises three steps as shown in Figure 1:

The first step, the preparation of the sodium alginate of small molecular weight:

In proportion, sodium alginate with a large molecular weight (weight-average molecular weight of 313kDa) was added to deionized water, swelled and dissolved by stirring, and a sodium alginate solution A with a concentration of 2% by mass was obtained;

Then, add hydrogen peroxide to obtain a mixed solution, the mass fraction of hydrogen peroxide in the mixed solution is 1.5%;

Heat the mixed solution to 65°C in a water bath, and stir for 4 hours;

Then, according to the volume ratio of the mixed solution and absolute ethanol being 1:2, add absolute ethanol to the mixed solution, precipitate and centrifuge to obtain a solid with small molecular weight sodium alginate as the main component;

The resulting solid was dissolved in deionized water, followed by dialysis and freeze-drying to obtain relatively pure small molecular weight sodium alginate powder (weight average molecular weight: 23kDa);

The second step, sodium alginate nanofiber self-assembly step:

Dissolving the obtained sodium alginate powder with a small molecular weight in deionized water while stirring to obtain a sodium alginate solution B with a concentration of 10% by mass;

In the third step, the obtained sodium alginate solution B was left to stand for 72 hours to self-assemble into sodium alginate nanofibers.

Observing the obtained products under a polarizing microscope and a transmission electron microscope respectively, it can be seen that the sodium alginate nanofibers are linear or branched; the diameter of the nanofibers is 50-200nm, and the length is 3000-5500nm.

Claims (2)

1. A kind of 1. method that nanofiber is self-assembled into using small-molecular-weight sodium alginate, which is characterized in that include the following steps：

   The first step, the preparation of the sodium alginate of small-molecular-weight：

   In proportion, the sodium alginate of macromolecule is added in deionized water, agitated swelling, dissolving obtain quality percentage Specific concentration is 1.5% sodium alginate soln A；

   Then, hydrogen peroxide is added in, obtains mixed solution, the mass fraction of hydrogen peroxide is 1.5%~2% in mixed solution；

   By mixed solution heating water bath to 65 DEG C, it is stirred to react 1h~15h；

   Again in the ratio that the volume ratio of mixed solution and absolute ethyl alcohol is 1 ︰ 2, absolute ethyl alcohol is added in into mixed solution, precipitate, Centrifugation, obtains with small-molecular-weight sodium alginate solid content as main component；

   Gained solid content is added into deionized water dissolving, then successively after dialysing, being freeze-dried, obtains purer small-molecular-weight Sodium alginate powder；

   Second step, sodium alginate nano fiber self assembly step：

   The sodium alginate powder of gained small-molecular-weight is added into deionized water dissolving while stirring, obtaining mass percent concentration is 5%~60% sodium alginate soln B；

   Third walks, and gained sodium alginate soln B is stood 2h~120h, is self-assembled into sodium alginate nano fiber；

   The sodium alginate of above-mentioned macromolecule refers to sodium alginate of the weight average molecular weight in 313kDa~586kDa；

   The sodium alginate of above-mentioned small-molecular-weight refers to the sodium alginate that weight average molecular weight is 23kDa~96kDa.
2. 2. the method according to claim 1 that nanofiber is self-assembled into using small-molecular-weight sodium alginate, feature are existed In a diameter of 50nm~800nm of obtained sodium alginate nano fiber, length is 3000nm~20000nm.