An iron-containing diatom shell material, its preparation method, its application, and a method for preparing a tannic acid-diatom shell composite material containing this material.
By preparing iron-containing diatom shell materials, tannic acid was loaded using iron ion coordination and nanoporous structure, which solved the problems of low stability and low bioavailability of tannic acid and achieved efficient loading and long-term drug delivery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YANTAI INST OF COASTAL ZONE RES CHINESE ACAD OF SCI
- Filing Date
- 2025-12-29
- Publication Date
- 2026-05-26
AI Technical Summary
In the existing technology, tannic acid has high water solubility, poor chemical stability, and is easily oxidized and degraded, resulting in low bioavailability. In addition, the existing carrier preparation process is complicated and costly, and may introduce biotoxicity. There is a lack of simple, economical and biocompatible loading methods.
Iron-containing diatom shell materials were prepared by optimizing culture conditions. Tannins were loaded onto the materials using their iron ion coordination and nanoporous structure to form stable complexes, thereby improving the stability and bioavailability of tannins.
This technology enables efficient loading of tannic acid, improving its chemical stability and bioavailability, making it suitable for long-acting drug delivery systems and expanding its application potential in the pharmaceutical and sterilization fields.
Smart Images
Figure CN122074498A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of biomaterials, specifically relating to an iron-containing diatom shell material, its preparation method, its application, and a method for preparing a tannic acid-diatom shell composite material containing the material. Background Technology
[0002] Diatom shells are natural porous silica materials biosynthesized from diatoms. They possess a highly ordered nanoscale pore structure, high specific surface area, thermal stability, and good biocompatibility, showing broad application potential in drug delivery, adsorption, catalysis, and biosensing. These unique nanostructures enable diatom shells to serve as micro-carriers for loading and controlled release of various active substances.
[0003] Tannic acid is a polyphenolic compound with potent antioxidant, antibacterial, anti-inflammatory, anticancer, and hemostatic activities, making it valuable in pharmaceuticals, sterilization, and tissue engineering. For example, tannic acid can be used as an anti-infective agent for wound healing and to promote tissue regeneration; its anticancer properties can inhibit tumor growth by inducing apoptosis, and it functions as a stabilizer or adhesive in drug delivery systems. However, tannic acid is highly water-soluble and chemically unstable, easily oxidized and degraded in air or rapidly released due to pH fluctuations, resulting in low bioavailability and difficulty in maintaining long-term activity in practical applications. These challenges limit the widespread use of tannic acid in pharmaceuticals and sterilization. For instance, in controlled-release drug systems, tannic acid often needs to be bound to a carrier to achieve sustained release, but existing methods have not effectively addressed its degradation problem.
[0004] Currently, supports for loading tannic acid mainly include organic polymers (such as polyethylene glycol or chitosan), inorganic nanoparticles (such as gold nanoparticles or metal-organic frameworks (MOFs), and hybrid materials. However, the preparation of these supports typically involves multi-step synthesis, complex chemical reactions, and high energy consumption, resulting in high costs and potential biotoxicity or immunogenicity issues. Biocompatibility needs further improvement. For example, while organic polymer supports offer good adhesion, their synthesis is complex, and their degradation products may impact the environment. Inorganic nanoparticles, although highly efficient in loading, are difficult to modify on the surface and may accumulate in vivo, leading to toxicity. Existing technologies lack a simple, economical, environmentally friendly, and biocompatible method to prepare iron-containing diatom shells and utilize their iron ion coordination and nanoporous structure to achieve efficient loading of tannic acid, thereby significantly improving the stability and durability of tannic acid and filling a gap in the field of sustainable biomaterials. Summary of the Invention
[0005] The purpose of this invention is to overcome the deficiencies of existing technologies and provide an iron-containing diatom shell material, its preparation method, its application, and a method for preparing a tannic acid-diatom shell composite material containing this material. This invention prepares iron-containing diatom shells by optimizing culture conditions and utilizes their iron ion coordination and specific pore size to achieve efficient loading of tannic acid, thereby improving the stability and bioavailability of tannic acid.
[0006] To achieve the above objectives, the present invention discloses an iron-containing diatom shell material, wherein the diatom shell material is tested by an energy dispersive spectroscopy instrument and the weight percentage of iron is not less than 0.4% and the silicon content is not less than 88%.
[0007] This invention also discloses a method for preparing iron-containing diatom shell materials, which are obtained through the following steps: (1) Cultivation of iron-containing diatoms: Add 100-150 mg / L sodium silicate nonahydrate and 5-10 mg / L ferrous sulfate heptahydrate to G11 medium, maintain a carbon dioxide concentration of 1% or open air flow, light intensity of 2000-3000 lx, light-dark cycle of 12h:12h, and culture at room temperature for 10-14 days; (2) Extraction of pure iron-containing diatom shells: The cultured diatoms were soaked in 20-30% hydrogen peroxide for 48-72 hours, then washed with 0.1-0.2M hydrochloric acid 2-4 times, and finally calcined at 700-900℃ for 1-3 hours in air atmosphere to obtain pure iron-containing diatom shells.
[0008] Furthermore, the initial inoculation density of the diatoms is 10. 4 -10 6 cells / mL.
[0009] In addition, the present invention also discloses the application of the iron-containing diatom shell material in loading tannic acid.
[0010] Specifically, a method for preparing a tannic acid-diatom shell composite material is disclosed. The above-mentioned iron-containing diatom shell material is prepared by the following steps: weighing tannic acid and dissolving it in bicine buffer solution with pH=7.0-8.0; adding diatom shell powder and stirring for 5-15 min; centrifuging to remove the supernatant, washing 2-4 times, and drying to obtain the loaded product tannic acid-diatom shell composite material.
[0011] Furthermore, the mass ratio of tannic acid to diatom shell is 1:10-1:30.
[0012] Furthermore, the centrifugation conditions are 4000-6000 rpm, 4-10℃, 3-10 min; washing is done with deionized water, and ultrasonication is performed for 0.5-2 min; drying temperature is 50-70℃, and time is 8-24 h.
[0013] The beneficial effects of this invention are: This invention creatively introduces iron ions into the culture medium, preparing diatom shells that not only retain the highly ordered nanoscale pore structure and high specific surface area of natural diatom shells, but also embed iron ion coordination sites. These sites can form stable complexes with the polyphenolic groups of tannic acid, thereby achieving efficient loading of tannic acid and forming polytannic acid complexes. This chemical coordination combined with physical adsorption loading mechanism significantly improves the chemical stability of tannic acid, preventing its rapid oxidative degradation in air or physiological environments, and improving the durability and bioavailability of tannic acid, making it suitable for long-acting drug delivery systems.
[0014] This invention utilizes natural diatom biosynthesis, avoiding complex chemical synthesis processes. It is simple to operate, low in cost, and the entire process is environmentally friendly, requiring no organic solvents or high-energy-consuming reactions, thus reducing environmental pollution. Furthermore, the biodegradability and high thermal stability of diatom shells ensure the safety of the product.
[0015] In terms of applications, this invention significantly expands the potential of tannic acid in the pharmaceutical and antibacterial fields. The loaded composite material enhances the antioxidant, antibacterial, and anti-inflammatory activities of tannic acid. The material can be used to develop novel anti-infective materials or care products. Attached Figure Description
[0016] Figure 1 Image 1: Scanning electron microscope (SEM) image of a pure diatom shell, showing the surface morphology and pore structure of the diatom shell.
[0017] Figure 2 Image 2: Scanning electron microscope (SEM) image of a pure diatom shell, showing the surface morphology and pore structure of the diatom shell.
[0018] Figure 3 SEM images of diatom shells after tannic acid loading, showing the surface changes after loading.
[0019] Figure 4 Transmission electron microscopy (TEM) image of a pure diatom shell, showing its internal structure.
[0020] Figure 5 TEM image 1 of diatom shells loaded with tannins, showing the distribution of the loaded material.
[0021] Figure 6 TEM image 2 of diatom shell after tannic acid loading, showing the distribution of the loaded material.
[0022] Figure 7 Energy dispersive spectroscopy (EDS) images of diatom shells confirm the presence of iron ions.
[0023] Figure 8The Fourier Transform Infrared (FTIR) spectrum shows a free carboxyl group at 3439 cm⁻¹ and a carbonyl group at 1091 cm⁻¹, confirming the loading of tannic acid, and a Si-O peak at 1090 cm⁻¹, confirming that the diatom shell structure is intact. Detailed Implementation
[0024] To better understand the present invention, specific embodiments are described in further detail below. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.
[0025] Example: Preparation of iron-containing diatom shells: Diatoms were selected as the starting strain, and the inoculation density was 1×10⁻⁶. 5 cells / mL. Use G11 medium with an additional 100 mg / L sodium silicate nonahydrate and 5 mg / L ferrous sulfate heptahydrate.
[0026] The culture conditions were set as follows: mixed air containing 1% carbon dioxide was introduced, light intensity was 2000 lx, light-dark cycle was 12h:12h, and culture was carried out at room temperature (25℃) for 14 days.
[0027] Extraction of pure iron-containing diatom shells: The cultured algal solution was collected and centrifuged to remove the supernatant. The algal sludge was soaked in 20% hydrogen peroxide for 48 hours to oxidize the organic matter, followed by centrifugation. The precipitate was washed three times with 0.1M hydrochloric acid to remove surface impurities and unbound metal ions. Finally, the precipitate was placed in a tube furnace and calcined at 800°C for 2 hours in air. After cooling, a white, pure iron-containing diatomaceous earth shell powder was obtained.
[0028] Preparation of tannic acid-diatom shell composite material: Accurately weigh 10 mg of tannic acid and dissolve it in 10 mL of Bicine (dihydroxyethylglycine) buffer (pH 7.4) to prepare a tannic acid solution. Weigh 200 mg of the iron-containing diatomaceous earth shell solid powder prepared above and add 5 mL of the above-mentioned tannic acid-containing Bicine buffer (tannic acid to diatomaceous earth shell mass ratio 1:20). Stir magnetically for 10 min at room temperature. The color of the mixture rapidly changes from light color to blue-purple, indicating that tannic acid has undergone a coordination reaction with iron ions. Then, centrifuge at 5000 rpm for 5 min at 4 °C and remove the supernatant. Add deionized water to the precipitate, sonicate for 1 min, and centrifuge again. Repeat the washing three times to remove tannic acid that is not physically adsorbed. Finally, dry the product in a 60 °C oven for 12 h to obtain the tannic acid-diatomaceous earth shell composite material.
[0029] Testing and data: SEM analysis: Figure 1 and Figure 2The results show that the iron-containing diatom shells prepared in Example 1 maintained a complete feather-like morphology, with clearly visible surface pores and no obvious collapse, indicating that high-temperature calcination and iron ion doping did not damage the skeletal structure of the diatom shells.
[0030] Figure 3 The results showed that after loading tannic acid, the surface of the diatom shell became relatively rough, some nanopores were filled, but the overall morphology did not agglomerate.
[0031] TEM analysis: Figure 4 The orderly array of nanopores inside the pure diatom shell is clearly displayed.
[0032] Figure 5 and Figure 6 The results show that in the composite material, the polymer layer formed by tannic acid uniformly coats the surface of the diatom shell and the inner wall of the pores, forming a thin film structure, which confirms the effective loading of tannic acid.
[0033] Composition analysis: EDS energy dispersive spectroscopy analysis: Figure 7 The energy dispersive spectroscopy (EDS) spectrum showed that, in addition to the characteristic elements Si (silicon) and O (oxygen), a significant Fe (iron) signal was also detected in the diatom shells prepared in Example 1. Quantitative analysis revealed that the weight percentage of iron was approximately 0.438%, and the silicon content was 88.9%, which meets the specifications set by this invention. FTIR infrared spectroscopy analysis: Figure 8 The infrared spectrum of the composite material showed a broad peak at 3439 cm⁻¹, attributed to the stretching vibration of the phenolic hydroxyl groups. At 1091 cm⁻¹, the characteristic strong carbonyl peak of tannic acid was not observed; instead, it shifted or broadened, attributed to the coordination of the phenolic hydroxyl groups of tannic acid with iron ions on the diatom shell surface. Simultaneously, the Si-O-Si antisymmetric stretching vibration peak at 1090 cm⁻¹ remained, indicating the integrity of the diatom shell substrate structure.
[0034] The above embodiments are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. An iron-containing diatomaceous earth shell material, characterized in that, The diatom shell material was tested by an energy dispersive spectroscopy (EDS) instrument, and the iron weight percentage was not less than 0.4%, and the silicon content was not less than 88%.
2. A method for preparing the iron-containing diatomaceous earth shell material as described in claim 1, characterized in that, It is prepared by the following steps: (1) Cultivation of iron-containing diatoms: Add 100-150 mg / L sodium silicate nonahydrate and 5-10 mg / L ferrous sulfate heptahydrate to G11 medium, maintain a carbon dioxide concentration of 1% or open air flow, light intensity of 2000-3000 lx, light-dark cycle of 12h:12h, and culture at room temperature for 10-14 days; (2) Extraction of pure iron-containing diatom shells: The cultured diatoms were soaked in 20-30% hydrogen peroxide for 48-72 hours, then washed with 0.1-0.2M hydrochloric acid 2-4 times, and finally calcined at 700-900℃ for 1-3 hours in air atmosphere to obtain pure iron-containing diatom shells.
3. The method for preparing iron-containing diatomaceous earth shell material according to claim 2, characterized in that, The initial inoculation density of the diatoms was 10. 4 -10 6 cells / mL.
4. The application of the iron-containing diatomaceous earth material as described in claim 1 on loaded tannic acid.
5. A method for preparing a tannic acid-diatom shell composite material, characterized in that... The iron-containing diatomaceous earth shell material as described in claim 1 is prepared by the following steps: weigh tannic acid and dissolve it in bicine buffer solution with pH=7.0-8.0; add diatomaceous earth shell powder and stir for 5-15 min; Centrifuge to remove the supernatant, wash 2-4 times, and dry to obtain the loaded product tannic acid-diatom shell composite material.
6. The method for preparing a tannic acid-diatom shell composite material according to claim 5, characterized in that: The mass ratio of tannic acid to diatom shell is 1:10-1:
30.
7. The method for preparing a tannic acid-diatom shell composite material according to claim 5, characterized in that: Centrifugation conditions: 4000-6000 rpm, 4-10℃, 3-10 min; washing with deionized water, ultrasonic time 0.5-2 min; drying temperature 50-70℃, time 8-24 h.