Photoreactive glycopolymer, environmentally friendly fine particles and hollow material

Abstract

Provided are a capsule and hollow particles based on particles formed from a glycopolymer containing glucose units in which at least one hydroxyl group is esterified with cinnamic acid to form a cinnamic acid ester (-OCO-CH = CH-C6H5).

Description

Photoreactive glycan polymers, environmentally friendly microparticles, and hollow materials

[0001] The present invention relates to photoreactive glycan polymers and fine particles containing them, environmentally friendly fine particles containing glycan polymers that have undergone photoreaction, hollow particles, capsules, etc. More specifically, the present invention relates to photodegradable and hydrolyzable environmentally friendly fine particles, hollow materials (hollow particles and capsules), etc., containing glycan polymers in which cinnamic acid is ester-bonded to a hydroxyl group and fine particles containing them, glycan polymers that have undergone photoreaction, etc.

[0002] Hollow particles possess physical characteristics such as high light scattering properties and structural characteristics such as internal voids, making them industrially applicable as light scattering agents, fragrances, cosmetics, and heat insulating materials. Furthermore, by encapsulating functional substances within them, they can be used in sunscreens and inks. However, these hollow particles and capsules are typically discharged into rivers and the sea through drainage outlets after use. If the polymers constituting the hollow particles and capsules are non-biodegradable, they can accumulate in the sea and have adverse effects on ecosystems. Therefore, it is desirable that the polymers constituting the hollow particles and capsules decompose naturally when discharged into the environment, resulting in a low environmental impact.

[0003] The following methods are known for manufacturing hollow particles and capsules. Conventionally, hollow particles using polymers such as vinyl polymers synthesized by radical polymerization have been mainly reported. For example, Non-Patent Document 1 describes SiO ２ Furthermore, it is reported that hollow particles can be obtained by constructing a vinyl polymer shell layer on the surface of a sacrificial template such as gold nanoparticles and removing the internal sacrificial template. Non-patent document 2 reports that hollow particles can be obtained in a suspension polymerization system by a method in which a crosslinked polymer precipitates in vinyl monomer droplets and accumulates at the droplet interface.

[0004] Morinaga, T.; Ohkura, M.; Ohno, K.; Tsujii, Y.; Fukuda, T., Monodisperse silica particles grafted with concentrated oxetane-carrying polymer brushes: Their synthesis by surface-initiated atom transfer radical polymerization and use for fabrication of hollow spheres. Macromolecules 2007, 40 (4), 1159-1164.Phase separation in the formation of hollow particles by suspension polymerization for divinylbenzene / toluene droplets dissolving polystyrene, Y Konishi, M. Okubo, H. Minami, COLLOID AND POLYMER SCIENCE 281(2) 123-129 February 2003.

[0005] Non-patent documents 1 and 2 disclose the production of hollow particles and capsules using vinyl polymers. However, these hollow particles and capsules are not biodegradable in nature and therefore cannot necessarily be considered environmentally friendly materials.

[0006] Therefore, the present invention aims to provide hollow particles and capsules that are manufactured from materials that are biodegradable in nature, that is, substances with a low environmental impact.

[0007] As a result of diligent research, the inventors synthesized a photoreactive polysaccharide polymer entirely derived from natural products by introducing cinnamic acid, which has a double bond derived from cinnamon, to a biomass-derived polysaccharide polymer such as starch via a hydrolyzable ester bond. They discovered that hollow particles and capsules can be directly manufactured using light.

[0008] The inventors further found that the obtained hollow particles and capsules are decomposed into the starting polysaccharide and cinnamic acid by hydrolysis and photolysis because the main chain is a polysaccharide and cinnamic acid is introduced via a hydrolyzable ester bond in the side chain. Since polysaccharide and cinnamic acid are molecules that originally exist in nature, the inventors found that the obtained hollow particles and capsules have a low environmental impact, which is preferable, and thus completed the present invention.

[0009] The present invention includes the following embodiments. 1. A sugar chain polymer containing a glucose unit in which at least one hydroxyl group is esterified with cinnamic acid and the hydrogen of the hydroxyl group is replaced with cinnamoyl (—CO—CH═CH—C ６ H ５ )). 2. The sugar chain polymer according to 1 above, containing a glucose unit represented by the following formula (I-1) and / or formula (I-2). [In formula (I-1), R １ , R ２ and R ３ are selected from hydrogen, acetyl and cinnamoyl (—CO—CH═CH—C ６ H ５ ), and at least one of R １ , R ２ and R ３ is cinnamoyl. ] [In formula (I-2), R ４ , R ５ and R ６ are selected from hydrogen, acetyl and cinnamoyl (—CO—CH═CH—C ６ H ５ ), and R ４ , R ５ and R ６1. A carbohydrate polymer according to 1 or 2 above, comprising glucose units in which three hydroxyl groups are esterified with cinnamic acid and the hydrogens of the three hydroxyl groups are replaced by cinnamoyl. 2. A carbohydrate polymer according to any one of 1 to 3 above, comprising 10 to 10,000 glucose units in which at least one hydroxyl group is esterified with cinnamic acid and the hydrogens of the hydroxyl groups are replaced by cinnamoyl. 3. A photoreactive microparticle comprising a carbohydrate polymer according to any one of 1 to 4 above. 4. A hollow particle having a cross-linking structure on the outer wall of a photoreactive microparticle comprising a carbohydrate polymer according to any one of 1 to 4 above. 5. A hollow particle according to 6 above, having a biodegradability of 5 to 15% in 20 days. 6. A capsule containing a substance inside the hollow particle according to 6 above. 7. A method for producing hollow particles, comprising: a crosslinking step of forming a crosslinked structure on the outer wall of a photoreactive microparticle containing a sugar chain polymer as described in any one of items 1 to 4 above; and a removal step of removing an uncrosslinked portion inside the photoreactive microparticle. 10. A microparticle containing a structure formed by the bonding of double bonds of cinnamoyl in the sugar chain polymer contained in the photoreactive microparticle described in item 5 above. 11. The microparticle according to item 10 above, containing a structure formed by the bonding of double bonds of cinnamoyl, as shown by the following formula (II). 12. A hollow particle having an outer wall formed by the bonding of double bonds of cinnamoyl in a sugar chain polymer contained within the photoreactive microparticle described in 5 above. 13. The hollow particle described in 12 above, having a structure formed by the bonding of double bonds of cinnamoyl, as shown in the following formula (II). 14. A capsule containing a substance inside the hollow particle described in item 12 or 13 above.

[0010] This invention synthesizes a photoreactive polysaccharide polymer entirely derived from natural products, obtained by introducing cinnamic acid, which has a double bond derived from cinnamon, to a biomass-derived polysaccharide polymer such as starch, via a hydrolyzable ester bond. This allows for the direct production of hollow particles and capsules using light. The resulting hollow particles and capsules have a polysaccharide main chain and cinnamic acid introduced into the side chain via a hydrolyzable ester bond, so they are decomposed into the raw material polysaccharide and cinnamic acid by hydrolysis and photodegradation. Since polysaccharides and cinnamic acid are molecules that naturally exist in the environment, the resulting hollow particles and capsules have a low environmental impact and are therefore desirable.

[0011] Figure 1 schematically shows the method for producing photoreactive amylose particles. Figure 2 shows optical microscope images and particle size distributions of photoreactive amylose particles from Examples 2, 2-2, and 2-3, from left to right. Figure 3 shows optical microscope images and particle size distributions of photoreactive amylose particles from Example 2-4. Figure 4 schematically shows the method for producing hollow amylose particles. Figure 5 shows optical microscope images and particle size distributions of photoreactive amylose particles from Example 3 before light irradiation (left), after light irradiation (middle), and after dimethyl sulfoxide washing (right). Figure 6 shows optical microscope images and particle size distributions of hollow amylose particles from Examples 3(a), 3-5(b), and 3-6(c). Figure 7 shows the weather on the day (a), the experimental conditions (b), and an optical microscope image of hollow amylose particles from Example 4. Figure 8 shows the ultraviolet absorption spectra of quartz substrates coated with various amounts of hollow amylose particles from Example 3. Figure 9 shows optical microscope images, confocal laser microscope images, and line profiles of the particle cross-section of amylose hollow particles (amylose capsule particles) of Example 5 containing rhodamine B (fluorescent dye). Figure 10 shows the hydrolytic properties of the amylose hollow particles of Example 3. Figure 11 shows the photodegradability of the amylose hollow particles of Example 3.

[0012] In one aspect of the present invention, at least one hydroxyl group is esterified with cinnamic acid, and the hydrogen of at least one hydroxyl group is cinnamoyl (-CO-CH=CH-C) ６ H ５The present invention provides a glycan polymer containing glucose units replaced by cinnamoyl(-CO-CH=CH-C)). In this specification, a glycan is not particularly limited as long as it contains two or more glucose units and yields the polymer targeted by the present invention. Examples of glycans include amylose, dextran, starch, cellulose, and cellulose acetate, with amylose, dextran, starch, cellulose, and cellulose acetate being preferred. The glycan polymer of the embodiment of the present invention has at least one hydrogen atom of a hydroxyl group contained in its glucose unit replaced by cinnamoyl(-CO-CH=CH-C) ６ H ５ Includes glucose units that are replaced by ).

[0013] In the carbohydrate polymer of the embodiment of the present invention, it is preferable that it contains glucose units represented by the following formula (I-1) and / or formula (I-2). [In formula (I-1), R １ , R ２ and R ３ is hydrogen, acetyl (-CO-CH ３ ) and cinnamoyl (-CO-CH=CH-C) ６ H ５ ) is selected from, R １ , R ２ and R ３ At least one of them is cinnamoil. [In formula (I-2), R ４ , R ５ and R ６ It consists of hydrogen, acetyl and cinnamoyl (-CO-CH=CH-C ６ H ５ ) is selected from, R ４ , R ５ and R ６ At least one of them is cinnamoil.

[0014] These glucose units include structures linked by α-1,4-glycosidic bonds (structures formed by dehydration condensation between the hydroxyl groups (-OH) at positions 1 and 4) (e.g., represented by formula (I-1)) and / or structures linked by α-1,6-glycosidic bonds (structures formed by dehydration condensation between the hydroxyl groups (-OH) at positions 1 and 6) (e.g., represented by formula (I-2)).

[0015] The glucose unit can have two or more hydroxyl groups and generally can contain three hydroxyl groups, but at least one hydrogen of the hydroxyl group is replaced by cinnamoyl to form a cinnamic acid ester (C ６ H ５ -CH=CH-COO-). It is preferable that the hydrogen of two hydroxyl groups of the glucose unit is replaced by cinnamoyl to form a cinnamic acid ester, and it is more preferable that the hydrogen of the three hydroxyl groups is replaced by cinnamoyl to form a cinnamic acid ester. The hydrogen of the hydroxyl group that has not become a cinnamic acid ester may be replaced by acetyl to form an acetic acid ester. When the hydrogen of the three hydroxyl groups is replaced by cinnamoyl to form a cinnamic acid ester, the efficiency of the photocrosslinking reaction is better, and a polymer obtained by the photocrosslinking reaction in a shorter time can be obtained.

[0016] At least one hydrogen of the hydroxyl group is replaced by cinnamoyl to form a cinnamic acid ester (-OCO-CH=CH-C ６ H ５ ), and the glucose unit can contain, for example, 10 or more. It is preferable to contain such glucose units from 10 to 10,000, more preferable to contain from 25 to 5,000, and even more preferable to contain from 50 to 1,000.

[0017] The sugar chain polymer of the embodiment of the present invention can be produced by esterifying the hydroxyl group of the sugar chain with cinnamic acid, but the production method is not particularly limited as long as the sugar chain polymer aimed at by the present invention can be obtained. The sugar chain polymer of the embodiment of the present invention can be produced, for example, by mixing a sugar chain and cinnamic acid chloride (cinnamoyl chloride: C ６ H ５ -CH=CH-CO-Cl). At that time, a solvent may be used, and reaction conditions such as the mixing ratio and reaction temperature can be appropriately adjusted. By appropriately adjusting the reaction conditions, the number of hydroxyl groups contained in the glucose unit contained in the sugar chain polymer esterified with cinnamic acid can be adjusted.

[0018] As another embodiment, the present invention can provide photoreactive microparticles containing the sugar chain polymer of the above-described embodiment. Since the double bond of the cinnamic acid ester (or cinnamoyl) in the above-described sugar chain polymer can undergo a photoreaction to dimerize, it has photoreactivity. Furthermore, microparticles containing such a sugar chain polymer having photoreactivity can be provided. The particle diameter of the photoreactive microparticles can be appropriately selected according to their use and the like. The particle diameter may be, for example, 10 nm to 1 mm, 20 nm to 500 μm, 50 nm to 250 μm, 100 nm to 100 μm, 200 nm to 50 μm, or 400 nm to 250 μm. In this specification, the particle diameter refers to the average value obtained by measuring and averaging the major diameters of about 100 particles using an optical microscope at room temperature (about 25°C). The morphology of the photoreactive microparticles is preferably spherical.

[0019] The photoreactive microparticles of the embodiment of the present invention can be produced by micronizing the sugar chain polymer of the above-described embodiment. However, as long as the photoreactive microparticles aimed at by the present invention can be obtained, the production method is not particularly limited. The photoreactive microparticles of the embodiment of the present invention can be produced, for example, by stirring the above-described saccharide polymer using an appropriate organic solvent in an aqueous medium in the presence of an emulsifier, volatilizing the appropriately added organic solvent, and filtering the photoreactive particles. The production conditions of the photoreactive particles, such as the type and amount of the aqueous medium, emulsifier, and organic solvent, and the stirring conditions, can be appropriately adjusted.

[0020] The present invention can provide microparticles of a further embodiment containing a structure (also referred to as a crosslinked structure) formed based on the photoreactive groups contained in the photoreactive microparticles of the above-described embodiment. The present invention can provide microparticles of a further embodiment containing a structure formed by the bonding of the double bonds of the cinnamic acid esters of the sugar chain polymers contained in the photoreactive microparticles of the above-described embodiment.

[0021] The microparticles of the above-described embodiment can include microparticles containing a structure formed by the bonding of the double bonds of cinnamoyl represented by the following formula (II). The structure formed by the bonding of two cinnamoyl double bonds, as shown in formula (II), forms an ester bond at its carbonyl group by bonding with the oxygen atom of the glucose unit in the fine particles of the above embodiment. It is preferable that the two carbonyl groups in the structure formed by the bonding of two cinnamoyl double bonds each bond with the oxygen atom of a different glucose unit in the fine particles of the above embodiment, as this can improve the strength of the fine particles.

[0022] The particle size of the fine particles of a further embodiment of the present invention, which includes a structure formed by the bonding of double bonds of cinnamoyl in the above-mentioned sugar chain polymer, can be appropriately selected depending on its application. The particle size may be, for example, 10 nm to 1 mm, 20 nm to 500 μm, 50 nm to 250 μm, 100 nm to 100 μm, 200 nm to 50 μm, or 400 nm to 250 μm. The morphology of the fine particles is preferably spherical.

[0023] Further embodiments of the present invention can be produced, for example, by irradiating the photoreactive fine particles of the above-described embodiments with light, but are not particularly limited as long as fine particles of further embodiments of the present invention can be obtained. For example, light (e.g., 265 nm, 4 mW / cm²) ２ It can be manufactured by irradiating it with light for one hour. For example, it can also be manufactured by irradiating it with sunlight for six hours. The type of light used and the duration of irradiation can be adjusted as appropriate.

[0024] As a preferred embodiment of the present invention, hollow particles can be provided in which a shell (outer wall) contains a structure (also called a crosslinked structure) formed based on photoreactive groups contained in the above-mentioned photoreactive microparticles. As a preferred embodiment of the present invention, hollow particles can be provided in which a shell (outer wall) contains a structure formed by the bonding of double bonds of cinnamoyl in the above-mentioned sugar chain polymer.

[0025] The present invention can provide hollow particles of the above embodiments, which include a structure formed by bonding cinnamoyl double bonds together, as shown by the following formula (II). The structure formed by the bonding of two cinnamoyl double bonds, as shown in formula (II), forms an ester bond at its carbonyl group by bonding with the oxygen atom of the glucose unit in the hollow particle of the above embodiment. It is preferable that the two carbonyl groups in the structure formed by the bonding of two cinnamoyl double bonds each bond with the oxygen atom of a different glucose unit in the hollow particle of the above embodiment, as this can improve the strength of the hollow particle.

[0026] The particle size of the hollow particles in the preferred embodiment of the present invention, which includes a structure formed by the bonding of double bonds of cinnamoyl in the above-mentioned sugar chain polymer, can be appropriately selected depending on its application. The particle size of the hollow particles may be, for example, 10 nm to 1 mm, 20 nm to 500 μm, 50 nm to 250 μm, 100 nm to 100 μm, 200 nm to 50 μm, or 400 nm to 250 μm. The shape of the hollow particles is preferably spherical. The thickness of the outer wall of the hollow particles in the preferred embodiment of the present invention can be appropriately selected depending on its application.

[0027] The hollow particles of the preferred embodiment of the present invention can be produced, for example, by adding an organic solvent to the fine particles of the further embodiment described above to elute the polymer inside the particles, but are not particularly limited as long as the hollow particles of the preferred embodiment of the present invention can be obtained. For example, they can be produced by eluting the polymer inside the particles in an organic solvent (e.g., dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dioxane, tetrahydrofuran, etc.). Elution conditions such as elution temperature and elution time can be adjusted as appropriate.

[0028] The present invention provides a method for producing hollow particles according to the above-described preferred embodiment, the method comprising a crosslinking step of forming a crosslinked structure on the outer wall of photoreactive microparticles containing the above-described sugar chain polymer, and a removal step of removing the uncrosslinked portion inside the photoreactive microparticles.

[0029] In a further preferred embodiment, the present invention can provide a capsule containing a substance inside the hollow particles of the above-described embodiment. The substance contained in the capsule is not particularly limited, as long as a capsule of the further preferred embodiment of the present invention can be obtained. Examples include fluorescent agents such as rhodamine B, fluorescein, and sulforhodamine, dyes, pigments, fragrances such as limonene and hinokitiol, and fertilizers such as urea.

[0030] The capsule diameter and outer wall thickness of the capsule in the further preferred embodiments described above can be appropriately selected depending on the application. The capsule diameter may be, for example, 10 nm to 1 mm, 20 nm to 500 μm, 50 nm to 250 μm, 100 nm to 100 μm, 200 nm to 50 μm, or 400 nm to 250 μm. The capsule shape is preferably spherical. The outer wall thickness of the capsule in the further preferred embodiments of the present invention can be appropriately selected depending on the application.

[0031] The method for manufacturing capsules according to a more preferred embodiment of the present invention is not particularly limited as long as the capsules can be obtained. For example, capsules according to a more preferred embodiment of the present invention can be manufactured by having the hollow particles of the preferred embodiment described above coexist with the substance to be contained in the capsule and a solvent. The substance to be contained in the capsule, the solvent, the temperature at which they coexist, the duration of coexistence, and other conditions can be adjusted as appropriate.

[0032] The fine particles of the above-described further embodiments of the present invention, the hollow particles of the preferred embodiment, and the capsules of the even more preferred embodiment all have a main chain of sugar chains and can form a crosslinked structure based on photoreactive groups. More preferably, cinnamic acid is introduced to the side chain via a degradable ester bond, and the cinnamic acid ester is dimerized by light. Therefore, by decomposition and hydrolysis through longer exposure to light, the molecular weight decreases, and it can be broken down into lower molecular weight sugars and cinnamic acid. Since these are all compounds that can naturally exist in the environment, they are considered to have a lower environmental impact.

[0033] The fine particles of the further embodiments of the present invention, the hollow particles of the preferred embodiment, and the capsules of the even more preferred embodiment can all be used to replace fine particles, hollow particles, capsules, etc., in conventional applications. Examples of such applications (and materials) include light scattering materials, heat insulating materials, sunscreens, inks, cosmetics, catalysts, and drug delivery systems, and are not particularly limited as long as the fine particles of the further embodiments of the present invention, the hollow particles of the preferred embodiment, and the capsules of the even more preferred embodiment are available. The materials for various applications, including the fine particles of the further embodiments, the hollow particles of the preferred embodiment, and the capsules of the even more preferred embodiment, are considered to have a low environmental impact because, even if they are released into nature, they can be broken down into lower molecular weight sugar chains and cinnamic acid over a long period of time by photodegradation and hydrolysis in nature. The fine particles of the further embodiments, the hollow particles of the preferred embodiment, and the capsules of the even more preferred embodiment of the present invention may have a biodegradability of 1 to 20% or 5 to 15% in 20 days, and can be appropriately selected depending on the application.

[0034] The present invention will be described in detail below with reference to examples and comparative examples, but these examples represent only one aspect of the present invention, and the present invention is not limited in any way by these examples.

[0035] Example 1: Synthesis of Photoreactive Amylose Amylose (enzyme-synthesized amylose (BAR-5K-1) manufactured by PS Biotech) and cinnamic acid chloride were each dissolved in dimethylacetamide (DMA) (containing 50 mM LiCl) to obtain DMA solutions of amylose and cinnamic acid chloride. Under an argon atmosphere, the DMA solution of cinnamic acid chloride was added to the DMA solution of amylose in an amount of 6 equivalents relative to the OH groups of amylose. After the reaction, the mixture was purified by reprecipitation with methanol to obtain photoreactive amylose (1)a of Example 1. The fact that the OH groups of amylose react with cinnamic acid chloride to form cinnamic acid esters was confirmed after hydrolysis in heavy water containing NaOD. １ This was confirmed by 1H-NMR measurement. It was found that almost 100% of the OH groups of amylose had been converted to cinnamic acid esters.

[0036] Examples 1-2 to 1-4 showed that the rate of cinnamoyl group introduction could be changed by changing the amount of cinnamic acid chloride added to the OH groups of amylose. When 4 equivalents of cinnamic acid chloride were reacted with the OH groups of amylose, photoreactive amylose (1)b of Example 1-2 was obtained, in which approximately 100% of the OH groups of amylose were converted to cinnamic acid esters. When 2 equivalents of cinnamic acid chloride were reacted with the OH groups of amylose, photoreactive amylose (1)c of Example 1-3 was obtained, in which approximately 53% of the OH groups of amylose were converted to cinnamic acid esters. When 0.33 equivalents of cinnamic acid chloride were reacted with the OH groups of amylose, photoreactive amylose (1)d of Example 1-4 was obtained, in which approximately 35% of the OH groups of amylose were converted to cinnamic acid esters.

[0037] Photoreactivity Evaluation of Photoreactive Amylose A chloroform solution of photoreactive amylose obtained by dissolving photoreactive amylose (1)a from Example 1 in chloroform was used to form a photoreactive amylose film on a quartz substrate using the casting method. The photoreactivity of the photoreactive amylose film was evaluated by irradiating it with 265 nm light. The UV absorption at λ = approximately 280 nm, which originates from the cinnamoyl group, gradually decreased and then disappeared, suggesting that the [2+2] photodimerization reaction proceeded when the photoreactive amylose was irradiated with light. The photoreactivity of the photoreactive amyloses from Examples 1-2 to 1-4 was similarly evaluated. In all cases, it was confirmed that the UV absorption at λ = approximately 280 nm, which originates from the cinnamoyl group, gradually decreased and then disappeared.

[0038] Example 2: Production of Photoreactive Amylose Particles Figure 1 schematically shows the method for producing photoreactive amylose particles. Photoreactive amylose (1)a (50 mg) from Example 1 was dissolved in chloroform (1 mL). To this chloroform solution, 0.0067 wt% aqueous polyvinyl alcohol (PVA) (15 mL) was added and homogenized for 1 minute using a homogenizer (12,000 rpm) to emulsify and obtain an aqueous dispersion of photoreactive amylose-chloroform. Furthermore, the chloroform was evaporated while continuing to stir at room temperature to obtain an aqueous dispersion of photoreactive amylose particles. The dispersion was filtered to obtain spherical photoreactive amylose particles from Example 2. At room temperature (approximately 25°C), the length of the major axis of approximately 100 particles was measured using an optical microscope, and the average particle diameter was 10.1 μm.

[0039] Examples 2-2 to 2-3: Spherical photoreactive amylose particles were obtained in Example 2 and Example 2-3 using the same method as described in Example 2 for producing photoreactive amylose particles, except that the homogenizer stirring speed was changed from 12,000 rpm to 16,000 rpm or 20,000 rpm. The particle size of each was measured using the same method as in Example 2, and the average particle sizes were 4.8 μm and 4.1 μm, respectively. Figure 2 shows optical microscope images and particle size distributions of the photoreactive amylose particles of Examples 2, 2-2, and 2-3 from left to right. In all cases, the photoreactive amylose particles were also obtained as spherical particles.

[0040] In Example 2-4, spherical photoreactive amylose particles were obtained using the same method as described in Example 2 for producing photoreactive amylose particles, except that water-soluble xylan (polysaccharide) was used instead of polyvinyl alcohol (PVA) (dispersion stabilizer). The particle size of each particle was measured using the same method as in Example 2, and the average particle size was 10.1 μm. Figure 3 shows an optical microscope image and particle size distribution of the photoreactive amylose particles of Example 2-4. The photoreactive amylose particles of Example 2-4 were also obtained as spherical particles.

[0041] Example 3: Production of Amylose Hollow Particles Using an LED Light Source Figure 4 schematically shows the method for producing amylose hollow particles. The aqueous dispersion of photoreactive amylose particles from Example 2 is irradiated with light from an LED light source (265 nm, 4 mW / cm²). ２ The process was carried out for one hour. Afterwards, the particles were filtered and washed with dimethyl sulfoxide to remove the uncrosslinked polymer from the particles. The mixture was then replaced again with a 0.0067 wt% aqueous PVA solution to obtain an aqueous dispersion of amylose hollow particles of Example 3. Figure 5 shows optical microscope images and particle size distribution of the photoreactive amylose particles of Example 3 before (left), after (center), and after washing with dimethyl sulfoxide. All particles were spherical. There was no change in particle size before and after light irradiation. After washing with dimethyl sulfoxide, the average particle size increased to 16.8 μm, and it was confirmed that the particles had become hollow particles with a shell portion visible at the particle interface.

[0042] Examples 3-2 to 3-4 Spherical amylose hollow particles of Examples 3-2 to 3-4 were obtained using the same method as for producing amylose hollow particles described in Example 3, except that a light irradiation time of 0.5 hours, 1.5 hours, or 2.0 hours was used instead of 1.0 hour. The particle size of each was measured using the same method as in Example 3, and the average particle sizes were 16.9 μm, 15.5 μm, and 15.1 μm.

[0043] Furthermore, when the shell thicknesses of the amylose hollow particles in Examples 3-2, 3, 3-3, and 3-4 were measured with an optical microscope, they were found to be 0.46 μm, 0.54 μm, 0.52 μm, and 0.53 μm, respectively.

[0044] Examples 3-5 and 3-6: Spherical amylose hollow particles of Examples 3-5 to 3-6 were obtained using the same method as for producing amylose hollow particles described in Example 3, except that instead of a stirring speed of 12,000 rpm and a PVA concentration of 0.0067 wt%, a stirring speed of 20,000 rpm and a PVA concentration of 0.0067 wt%, or 20,000 rpm and a PVA concentration of 0.67 wt%, were used. The particle size of each was measured using the same method as in Example 3, and the average particle sizes were 9.0 μm and 3.3 μm. Figure 6 shows, from left to right, optical microscope images and particle size distributions of the amylose hollow particles of Examples 3, 3-5, and 3-6.

[0045] Example 4: Production of Amylose Hollow Particles Using Sunlight The aqueous dispersion of photoreactive amylose particles from Example 2 was placed outdoors on a clear day in mid-July and exposed to sunlight for 6 hours from 9:00 AM to 3:00 PM. During this time, it was confirmed that the sun was not obscured by clouds. The particles were then filtered and washed with dimethyl sulfoxide to remove the uncrosslinked polymer from the particles. The mixture was then replaced again with a 0.0067 wt% PVA aqueous solution to obtain the amylose hollow particles of Example 4. The particle size and shell thickness were observed and analyzed using an optical microscope. In addition, the aqueous dispersion of photoreactive amylose particles from Example 2 was covered with aluminum foil to block sunlight and exposed to sunlight in the same manner, but no hollow particles were obtained. Figure 7 shows the weather on the day (a), the experimental conditions (b), and an optical microscope image of the amylose hollow particles of Example 4.

[0046] Light-shielding effect of amylose hollow particles: 25, 50, 75, 100, and 150 μL each of aqueous dispersions of amylose hollow particles (6 mg / mL) from Example 3 were dropped onto a quartz substrate and allowed to dry completely. The light-shielding effect in the UVC, UVB, and UVA regions was then evaluated by measuring the ultraviolet-visible absorption spectra. As the amount of amylose hollow particles coated increased, the absorbance increased at all wavelengths of UVC, UVB, and UVA, demonstrating a light-shielding effect in the ultraviolet region. Figure 8 shows the ultraviolet absorption spectra of quartz substrates coated with various amounts of amylose hollow particles from Example 3.

[0047] Example 5: Evaluation of Amylose Hollow Particle Material Encapsulation Ability (Capsule Ability Evaluation) 1 mL of the aqueous dispersion of amylose hollow particles from Example 3 (2 mg / mL) was centrifuged to remove the solvent. Then, a dimethyl sulfoxide solution containing rhodamine B (10 mg / mL, 1 mL) was added and incubated for 30 minutes. After that, the amylose hollow particles were centrifuged, the supernatant was removed, and the mixture was washed multiple times with an aqueous PVA solution to obtain amylose capsule particles of Example 5, in which rhodamine B (fluorescent dye) was encapsulated within the hollow particles. Whether or not rhodamine B was encapsulated was evaluated using a confocal laser microscope. Figure 9 shows optical microscope images, confocal laser microscope images, and line profiles of the particle cross-section of the amylose hollow particles (amylose capsule particles) of Example 5 that encapsulated rhodamine B (fluorescent dye). In confocal laser microscope observation, fluorescence originating from rhodamine B was clearly observed from inside the particles. Furthermore, line profiles of the particle cross-sections revealed that the fluorescence intensity inside the particle was significantly higher than that outside, indicating that the fluorescent dye was encapsulated within the particle. It was also revealed that rhodamine B was adsorbed on the particle shell.

[0048] Hydrolysis Evaluation of Amylose Hollow Particles: The dispersion of amylose hollow particles (1 mg / mL, 12 mL) from Example 3 was centrifuged to obtain amylose hollow particles. These hollow particles were incubated in 2 mL of 50 mM NaOH aqueous solution at 60°C. Visual observation was performed at 0 h, 0.5 h, 1 h, 2 h, and 4 h, and samples were taken to measure the transmittance of light at 600 nm. The absorbance of light at 600 nm decreased (transmittance increased). This indicates that the amylose hollow particles of Example 3, which decrease light transmittance by scattering light, are undergoing hydrolysis. The increasing transmittance over time was also confirmed from photographs of the particle dispersion. Figure 10 shows the hydrolysis properties of the amylose hollow particles of Example 3.

[0049] Photodegradability Evaluation of Amylose Hollow Particles: In Example 3, an aqueous dispersion of amylose hollow particles (1 mg / mL, 12 mL) was centrifuged to obtain amylose hollow particles. These hollow particles were dispersed in 2 mL of dimethyl sulfoxide and exposed to light (λ = 254 nm, 2 mW / cm²) at room temperature. ２The particles were irradiated with light. Visual observations were made at 0h, 3h, 6h, and 12h, and samples were taken to measure the light transmittance at 600nm. The absorbance of 600nm light decreased (transmittance increased). This indicates that the amylose hollow particles of Example 3, which reduce light transmittance by scattering light, are being decomposed by light. Photographs of the particle dispersion also confirmed that the transmittance increased over time. Figure 11 shows the photodecomposition of the amylose hollow particles of Example 3.

[0050] Biodegradability Evaluation of Amylose Hollow Particles Example 3: An aqueous dispersion of amylose hollow particles (1 mg / mL, 12 mL) was centrifuged to obtain amylose hollow particles. These hollow particles were dispersed in a culture medium and activated sludge. After installing a carbon dioxide absorbent, a BOD test (biochemical oxygen consumption test) was performed using a closed-system oxygen consumption meter. This BOD test was commissioned to the Chemicals Evaluation and Research Institute (conducted in accordance with JIS K6950 (ISO 14851) (BOD measurement using activated sludge)). Approximately 7% biodegradability was observed after 20 days.

[0051] Example 6 Synthesis of Photoreactive Dextran Photoreactive dextran (1)e of Example 6 was obtained using the same method as in Example 1, except that dextran (Dextran (trade name) from Thermo Fisher) was used instead of amylose. The OH group of dextran reacts with cinnamic acid chloride to form a cinnamic acid ester, which was observed after hydrolysis in heavy water containing NaOD. １ This was confirmed by 1H-NMR measurement. It was found that approximately 91% of the OH groups of dextran were converted to cinnamic acid esters.

[0052] The photoreactivity of photoreactive dextran (1)e in Example 6 was evaluated using the same method as in Example 1, except that photoreactive dextran (1)e in Example 6 was used instead of photoreactive amylose (1)a in Example 1. The UV absorption at λ = approximately 284 nm derived from the cinnamoyl group gradually decreased and then disappeared, so it is considered that the [2+2] photodimerization reaction proceeded when photoreactive dextran (1)e was irradiated with light.

[0053] Example 7: Production of Photoreactive Dextran Particles Spherical photoreactive dextran particles of Example 7 were obtained using the same method as in Example 2, except that photoreactive dextran(1)e from Example 6 was used instead of photoreactive amylose(1)a from Example 1. At room temperature (approximately 25°C), the length of the major axis (substantially diameter) of approximately 100 particles was measured using an optical microscope, and the average particle diameter was found to be 8.3 μm.

[0054] Example 8: Production of Dextran Hollow Particles Using an LED Light Source An aqueous dispersion of dextran hollow particles of Example 8 was obtained using the same method as in Example 3, except that photoreactive dextran particles of Example 7 were used instead of photoreactive amylose particles of Example 2. The average particle size of the dextran hollow particles of Example 8 after washing with dimethyl sulfoxide was 19.0 μm, which was larger.

[0055] Example 9: Evaluation of the material encapsulation ability of dextran hollow particles (capsule ability evaluation) Dextran capsule particles of Example 9 were obtained using the same method as in Example 5, except that the aqueous dispersion of dextran hollow particles of Example 8 was used instead of the aqueous dispersion of amylose hollow particles of Example 3. Confocal laser microscopy observation clearly showed fluorescence originating from rhodamine B from inside the particles. Furthermore, line profiles of the particle cross-section showed that the fluorescence intensity inside the particles was clearly greater than that outside the particles, indicating that a fluorescent dye was encapsulated inside the particles.

[0056] Example 10: Synthesis of photoreactive cellulose acetate. Except for using cellulose acetate (product name: cellulose acetate from Fujifilm Wako Co., Ltd.) instead of amylose, the same method as in Example 1 was used to obtain photoreactive cellulose acetate (1)f of Example 10. The OH groups of cellulose acetate (approximately 80% of the OH groups remain unacetylated) react with cinnamic acid chloride to form cinnamic acid esters. This was confirmed after hydrolysis in heavy water containing NaOD. １ This was confirmed by 1H-NMR measurement. It was found that approximately 1.1 units of cinnamic acid ester structure are present within the 10-glucose structure of cellulose acetate.

[0057] The photoreactivity of photoreactive cellulose acetate (1)f in Example 10 was evaluated using the same method as in Example 1, except that photoreactive cellulose acetate (1)f in Example 10 was used instead of photoreactive amylose (1)a in Example 1. The UV absorption at λ = approximately 280 nm derived from the cinnamoyl group gradually decreased and then disappeared, suggesting that the [2+2] photodimerization reaction proceeded when photoreactive cellulose acetate (1)f was irradiated with light.

[0058] Example 11: Production of Photoreactive Cellulose Acetate Particles Spherical photoreactive cellulose acetate particles of Example 11 were obtained using the same method as in Example 2, except that photoreactive cellulose acetate (1)f from Example 10 was used instead of photoreactive amylose (1)a from Example 1. At room temperature (approximately 25°C), the length of the major axis (substantially diameter) of approximately 100 particles was measured using an optical microscope, and the average particle diameter was found to be between 1 μm and 20 μm.

[0059] Example 12: Production of hollow cellulose acetate particles using an LED light source. An aqueous dispersion of hollow cellulose acetate particles of Example 12 was obtained using the same method as described in Example 3, except that the photoreactive cellulose acetate particles of Example 11 were used instead of the photoreactive amylose particles of Example 2. The average particle size of the hollow cellulose acetate particles of Example 12 after washing with dimethyl sulfoxide was 1 μm to 20 μm.

[0060] Example 13: Evaluation of the material encapsulation ability of hollow cellulose acetate particles (capsule ability evaluation) Cellulose acetate capsule particles of Example 13 were obtained using the same method as in Example 5, except that the aqueous dispersion of hollow cellulose acetate particles of Example 12 was used instead of the aqueous dispersion of hollow amylose particles of Example 3. Confocal laser microscopy observation clearly showed fluorescence originating from rhodamine B from inside the particles. Furthermore, line profiles of the particle cross-section showed that the fluorescence intensity inside the particles was clearly greater than that outside the particles, indicating that a fluorescent dye was encapsulated inside the particles.

[0061] This invention synthesizes a photoreactive polysaccharide polymer entirely derived from natural products by introducing cinnamic acid, which has a double bond derived from cinnamon, to a biomass-derived polysaccharide polymer such as starch via a hydrolyzable ester bond. This allows for the direct provision of hollow particles and capsules using light. The resulting hollow particles and capsules have a polysaccharide main chain and cinnamic acid introduced into the side chain via a hydrolyzable ester bond, so they are decomposed into the raw material polysaccharide and cinnamic acid by hydrolysis and photodegradation. Since polysaccharides and cinnamic acid are molecules that naturally exist in the environment, the resulting hollow particles and capsules have a low environmental impact and are therefore desirable.

Claims

1. At least one hydroxyl group is esterified with cinnamic acid, and the hydrogen of the hydroxyl group is cinnamoyl (-CO-CH=CH-C) ６ H ５ A carbohydrate polymer containing glucose units replaced by ).

2. The sugar chain polymer according to claim 1, comprising a glucose unit represented by the following formula (I-1) and / or formula (I-2). [In formula (I-1), R １ , R ２ and R ３ are selected from hydrogen, acetyl, and cinnamoyl (—CO—CH═CH—C ６ H ５ ), and at least one of R １ , R ２ and R ３ is cinnamoyl.] [In formula (I-2), R ４ , R ５ and R ６ are selected from hydrogen, acetyl, and cinnamoyl (—CO—CH═CH—C ６ H ５ ), and at least one of R ４ , R ５ and R ６ is cinnamoyl.] 3. The glycan polymer according to claim 1 or 2, comprising a glucose unit in which three hydroxyl groups are esterified with cinnamic acid and the hydrogens of the three hydroxyl groups are replaced with cinnamoyl.

4. The glycan polymer according to claim 1 or 2, comprising 10 to 10,000 glucose units in which at least one hydroxyl group is esterified with cinnamic acid and the hydrogen of the hydroxyl group is replaced by cinnamoyl.

5. Photoreactive fine particles comprising the sugar chain polymer described in claim 1 or 2.

6. Hollow particles having a crosslinking structure on the outer wall of photoreactive fine particles containing the sugar chain polymer according to claim 1 or 2.

7. The hollow particles according to claim 6, wherein the degree of biodegradation is 5 to 15% in 20 days.

8. A capsule containing a substance inside a hollow particle as described in claim 6.

9. A method for producing hollow particles, comprising: a crosslinking step of forming a crosslinked structure on the outer wall of photoreactive fine particles containing the sugar chain polymer described in claim 1 or 2; and a removal step of removing an uncrosslinked portion inside the photoreactive fine particles.

10. A microparticle comprising a structure formed by the bonding of double bonds of cinnamoyl molecules of a sugar chain polymer contained within the photoreactive microparticle described in claim 5.

11. The fine particles according to claim 10, comprising a structure formed by the bonding of double bonds of cinnamoyl, as shown in formula (II) below.

12. A hollow particle having an outer wall in which the double bonds of cinnamoyl in a sugar chain polymer contained within the photoreactive fine particle described in claim 5 are bonded together.

13. The hollow particle according to claim 12, comprising a structure formed by bonding of cinnamoyl double bonds, as shown in formula (II) below.

14. A capsule containing a substance inside a hollow particle as described in claim 12.

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