PREPARATION METHOD FOR MULBERRY SILK THAT FLUORESCES UNDER NEAR-INFRARED LIGHT AND PRODUCT

Abstract

Disclosed is a method for constructing fluorescent Bombyx Mori silkworm silk irradiated by near-infrared light and its products, comprising: (1) preparing upconversion nanoparticles, and performing surface modification with concanavalin to obtain modified upconversion nanoparticles; (2) uniformly dispersing the modified upconversion nanoparticles in water to formulate an aqueous solution of the upconversion nanoparticles, (3) picking mature mulberry leaves, immersing the mulberry leaves in the aqueous solution system of the nanoparticles, leaching water, and naturally drying the mulberry leaves; (4) after silkworms have grown for a set time, feeding the treated mulberry leaves to the silkworms until the silkworms spin silk cocoons; and (5) collecting the silk, so as to obtain mulberry silk that fluoresces under near-infrared light. The present invention selects upconversion nanoparticles capable of emitting fluorescence under the irradiation of near-infrared light which has stronger penetration, thus has better application in deep tissue imaging.

Claims

1. A method for constructing fluorescent Bombyx mori silkworm silk irradiated by near-infrared light and its products, characterized by comprising the following steps: (1) preparing upconversion nanoparticles, and performing surface modification with concanavalin to obtain modified upconversion nanoparticles; (2) uniformly dispersing the modified upconversion nanoparticles in the step (1) into water to formulate an aqueous solution of the upconversion nanoparticles; (3) picking mature mulberry leaves, immersing the mulberry leaves in the aqueous solution system of the nanoparticles in the step (2), draining the water, and naturally drying the mulberry leaves; (4) after silkworms have grown for a set time, feeding the treated mulberry leaves in the step (3) to the silkworms until the silkworms spin silk cocoons; and (5) collecting the silk fiber to obtain Bombyx mori silkworm silk that fluoresces under near-infrared light.

2. The preparation method for Bombyx mori silkworm silk that fluoresces under near-infrared light according to claim 1, characterized in that upconversion nanoparticles have a core-shell structure.

3. The preparation method for fluorescent silk irradiated by near-infrared light according to claim 1, characterized in that the upconversion nanoparticles comprise one or more of β-NaYF.sub.4:Yb, Er@β-NaYF.sub.4 upconversion nanoparticles, NaGdF.sub.4:Yb/Er@NaGdF.sub.4:Yb/Nd, NaYF.sub.4:Yb/Er or upconversion nanoparticles emitting red fluorescence.

4. The preparation method for fluorescent silk irradiated by near-infrared light according to claim 1, characterized in that the upconversion nanoparticles are polyacrylic acid (PAA)-modified core-shell structure upconversion nanoparticles.

5. The preparation method for fluorescent silk irradiated by near-infrared light according to claim 1, characterized in that the preparation method of the upconversion nanoparticles is as follows: preparing the PPA-modified core-shell structure upconversion nanoparticles, and introducing concanavalin, then grafting the concanavalin on the surface of the upconversion nanoparticles by means of a cross-linking agent 1-ethyl-3-(3-dimethylaminopropyl)-carbonimide to form a composite co-polymer.

6. The preparation method for fluorescent silk irradiated by near-infrared light according to claim 1, characterized in that the method for surface modification with concanavalin is as follows: performing PAA grafting on the surface of the upconversion nanoparticles by an ligand exchange method, and performing centrifugation to obtain a precipitate; taking 10 mg PPA-modified nanoparticles and dispersing into 1 mL aqueous solution, and respectively adding 1 mg EDC and NHS and stirring for reaction for 3-6 h, then adding 30 μL concanavalin aqueous solution, wherein the concanavalin aqueous solution has a concentration of 3-10 mg/mL, then stirring the solution over night, and performing centrifugal washing to obtain the concanavalin-modified upconversion nanoparticles.

7. The preparation method for fluorescent silk irradiated by near-infrared light according to claim 1, characterized in that the aqueous solution of the upconversion nanoparticles has a concentration of 1-5 g/L.

8. The preparation method for fluorescent silk irradiated by near-infrared light according to claim 1, characterized in that silkworms are fed with the mulberry leaves in the step (3) after growing to the third day of fifth-instar stage.

9. The preparation method for fluorescent silk irradiated by near-infrared light according to claim 1, characterized in that the modified upconversion nanoparticles obtained in the step (1) have a mean diameter of 50-100 nm.

10. The preparation method for fluorescent silk irradiated by near-infrared light according to claim 1, characterized in that in the step (3), the immersion time of the mulberry leaves is 2-5 min.

11. The preparation method for fluorescent silk irradiated by near-infrared light according to claim 1, characterized in that in the step (5), silkworms are induced to spin on a flat board, thus collecting silk.

12. A Bombyx mori silkworm silk that fluoresces under near-infrared light, characterized in that the mulberry silk is obtained by a method comprising: (1) preparing upconversion nanoparticles, and performing surface modification with concanavalin to obtain modified upconversion nanoparticles; (2) uniformly dispersing the modified upconversion nanoparticles in the step (1) into water to formulate an aqueous solution of the upconversion nanoparticles; (3) picking mature mulberry leaves, immersing the mulberry leaves in the aqueous solution system of the nanoparticles in the step (2), draining the water, and naturally drying the mulberry leaves; (4) after silkworms have grown for a set time, feeding the treated mulberry leaves in the step (3) to the silkworms until the silkworms spin silk cocoons; and (5) collecting the silk fiber to obtain Bombyx mori silkworm silk that fluoresces under near-infrared light.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows fluorescent pictures of non-core-shell structure upconversion nanoparticles and core-shell structure upconversion nanoparticles under the excitation of a 980 nm laser. (The left shows non-core-shell structure upconversion nanoparticles and the right shows core-shell structure upconversion nanoparticles)

[0037] FIG. 2 shows a photofluorogram of flat board silk obtained in Example 1 under radiation of the 980 nm laser.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The present invention will be further described below in detail by the examples; the following examples are used to explain the present invention but not constructed as limiting the present invention.

[0039] Examples of the present invention are as follows:

Example 1

[0040] (1) Core-shell structure upconversion nanoparticles exciting green fluorescence (β-NaYF.sub.4:Yb,Er@β-NaYF.sub.4, diameter: about 50 nm) were prepared with a hydrothermal method, and subjected to surface PAA modification and grafted with concanavalin as a feeding material; and the synthetic method was as follows:

[0041] Core-shell structure upconversion nanoparticles (β-NaYF.sub.4:Yb,Er@β-NaYF.sub.4) were prepared with an existing method (J. Am. Chem. Soc. 128, 6426-6436.), and dispersed into a n-hexane solution. Polyacrylic acid (PAA) was grafted on the surface of nanoparticles by a ligand exchange method; 1 mL upconversion nanoparticle solution and 5 mL dimethyl formamide (DMF) were blended, and then 4 mL n-hexane was added for stirring for 3 h. 5-10 mL isopropanol was added for precipitation, and precipitates were washed by DMF for several times. The precipitates were resuspended in PAA/DMF solution (PAA concentration was 10 mg/mL, 5-10 mL), staying over the night, stirred, centrifuged and washed. 10 mg PAA-modified nanoparticles were taken and dispersed into 1 mL aqueous solution; 1 mg EDC and NHS were respectively added and stirred for reaction for 3-6 h, afterwards, 30 uL concanavalin aqueous solution (3-10 mg/mL) was added and stirred over the night, centrifuged and washed to obtain concanavalin-modified upconversion nanoparticles;

[0042] (2) the upconversion nanoparticles synthesized in the step (1) were dispersed uniformly with water to formulate a dispersion solution having a concentration of 2 g/L;

[0043] (3) mature mulberry leaves were picked and immersed into a nanoparticle aqueous solution in the step (2), 2 min later, fished out and dried naturally;

[0044] (4) silkworms were fed with the treated mulberry leaves in the step (3) after growing to the the third day of fifth-instar stage until spinning and silk cocooning;

[0045] (5) after growing to the spinning stage, silkworms were transferred to the smooth board surface and induced to spin on the flat board, then silk was collected;

[0046] (6) the obtained mulberry silk was irradiated by a 980 nm near-infrared laser, and the mulberry ilk on the flat board gives off bright green fluorescence (converted to a grey-scale map, and the green fluorescence portion was partially converted to a greyish white portion), as shown in FIG. 2, thus obtaining a mulberry silk that fluoresces under near-infrared light.

Example 2

[0047] (1) Upconversion nanoparticles exciting red fluorescence (NaYF.sub.4:1% Er, 1% Tm, a diameter: about 60 nm) were prepared with a hydrothermal method, and subjected to surface PAA modification and grafted with concanavalin as a feeding material; and the synthetic method was as follows:

[0048] Red fluorescent upconversion nanoparticles (NaYF.sub.4:1% Er, 1% Tm) were prepared with an existing method (J. Phys. Chem. C, Vol. 113, No. 44, 2009), and dispersed into a n-hexane solution. Polyacrylic acid (PAA) was grafted on the surface of nanoparticles by a ligand exchange method; 1 mL upconversion nanoparticle solution and 5 mL dimethyl formamide (DMF) were blended, and then 4 mL n-hexane was added for stirring for 3 h. 5-10 mL isopropanol was added for precipitation, and precipitates were washed by DMF for several times. The precipitates were resuspended in PAA/DMF solution (PAA concentration was 10 mg/mL (5-10 mL), staying over the night, stirred, centrifuged and washed. 10 mg PAA-modified nanoparticles were taken and dispersed into 1 mL aqueous solution; 1 mg EDC and NHS were respectively added and stirred for reaction for 3-6 h, afterwards, 30 uL concanavalin aqueous solution (3-10 mg/mL) was added and stirred over the night, centrifuged and washed to obtain concanavalin-modified upconversion nanoparticles;

[0049] (2) the upconversion nanoparticles synthesized in the step (1) were dispersed uniformly with water to formulate a dispersion solution having a concentration of 5 g/L;

[0050] (3) mature mulberry leaves were picked and immersed into a nanoparticle aqueous solution in the step (2), 2 min later, fished out and dried naturally;

[0051] (4) silkworms were fed with the treated mulberry leaves in the step (3) after growing to the fifth-instar stage+3 d until spinning and silk cocooning;

[0052] (5) after silkworms spined silk cocoons, the silkworm cocoons were taken and subjected to reeling treatment to obtain mulberry silk giving off red fluorescence under the excitation of near-infrared light.

Example 3

[0053] (1) Core-shell structure upconversion nanoparticles (NaGdF.sub.4:Yb/Er@NaGdF.sub.4:Yb/Nd, a diameter: about 50 nm) exciting green fluorescence were prepared by a hydrothermal method, and subjected to surface PAA modification and grafted with concanavalin as a feeding material;

[0054] (2) the upconversion nanoparticles synthesized in the step (1) were dispersed uniformly with water to formulate a dispersion solution having a concentration of 5 g/L;

[0055] (3) mature mulberry leaves were picked and immersed into a nanoparticle aqueous solution in the step (2), 5 min later, fished out and dried naturally;

[0056] (4) silkworms were fed with the treated mulberry leaves in the step (3) after growing to the fifth-instar stage+3 d until spinning and silk cocooning;

[0057] (5) after silkworms spined silk cocoons, the silkworm cocoons were taken and subjected to reeling treatment to obtain mulberry silk giving off green fluorescence under the excitation of near-infrared light with a higher fluorescence intensity.

[0058] The mulberry silk prepared in the Example 3 served as a sample 1. Based on the method the same as that in Example 3, and the difference was that the dispersion solution in the step (2) was diluted by two concentrations to obtain a sample 2; a sample 3 was mulberry silk obtained by feeding common mulberry leaves; ICP-MS was used for quantitative analysis on the content of rare earth elements in mulberry silk. In comparison to the content of upconversion nanoparticles in conventional mulberry silk and modified mulberry silk, analysis and comparison are shown in Table 1.

TABLE-US-00001 Table 1 is a comparison table of the content of rare earth elements between the common mulberry silk and modified mulberry silk measured by ICP-MS in Example 3. Element content Y (%) Er (%) Yb (%) Na (%) 1 Sample 1 2.0 × 10.sup.−4 6.5 × 10.sup.−4  5.0 × 10.sup.−4 6.37 2 Sample 2 5.1 × 10.sup.−4 3.0 × 10.sup.−4 1.49 × 10.sup.−3 9.0 3 Sample 3 3.3 × 10.sup.−6 7.3 × 10.sup.−6  6.7 × 10.sup.−6 6.8

[0059] Table 1 indicates that the nanoparticles added herein can be used for the content detection in the final silk, indicating a higher feeding efficiency.

[0060] Finally, it should be noted that the above examples are merely detailed embodiments of the present invention. Apparently, the present invention is not limited to the above examples, and there are lots of transformations. A person skilled in the art can directly derive or associate with all the transformations from the disclosure of the present invention, and these transformations should be regarded within the protection scope of the present invention.