A porous carrier-based two-component synergistic antibacterial composite material and a preparation method thereof

Abstract

This invention discloses a two-component synergistic antibacterial composite material based on a porous carrier and its preparation method, belonging to the field of functional composite material technology. The composite material uses diatomaceous earth@mesoporous polydopamine core-shell porous microspheres as a carrier. The first component is a copper-based nanocluster cluster confined within the carrier pores, and the second component is quaternized chitosan anchored to the outer surface of the carrier via silane bridging, forming a synergistic antibacterial structure with a dual mechanism of "intrapore contact killing – surface film disruption". In this invention, the two components exhibit orthogonal and spatially partitioned action mechanisms, demonstrating a synergistic index (FIC≤0.48) against Gram-positive bacteria, Gram-negative bacteria, and biofilms. Furthermore, the burst release of copper ions is suppressed by the confinement of the pores, with a cumulative dissolution amount of <0.5ppm over 28 days. Natural diatomaceous earth can be used as the raw material, the process is simple, and it is suitable for water treatment, medical dressings, and food packaging films.

Description

Technical Field

[0001] This invention relates to composite materials, specifically a two-component synergistic antibacterial composite material based on a porous carrier and its preparation method. Background Technology

[0002] Antimicrobial materials have wide applications in modern medicine, environmental purification, and food packaging. Traditional antimicrobial agents mainly include inorganic metal ion types (such as silver ions and zinc ions), organic small molecule types (such as quaternary ammonium salts and guanidine salts), and natural extract types (such as chitosan). However, single-component antimicrobial materials often suffer from problems such as narrow antimicrobial spectrum, easy development of drug resistance, and short-term effectiveness due to burst release of active ingredients, making it difficult to meet the long-lasting and broad-spectrum antimicrobial requirements in complex scenarios.

[0003] To address the aforementioned issues, those skilled in the art have attempted to combine two or more antibacterial components onto porous supports in an effort to achieve synergistic effects. For example, CN110066459B discloses a guanidine salt polymer-modified zinc-loaded zeolite antibacterial agent, which utilizes the dual action of guanidine salts and zinc ions to achieve antibacterial activity. However, both components in this scheme operate on an ion dissolution mechanism, resulting in highly homogeneous action and producing only a simple additive effect rather than a true synergistic effect. Furthermore, the inhibitory effect of zinc ions on Gram-negative bacteria is limited. Another example is X technology document 202512017717, which discloses a ternary metal composite antibacterial material based on porous supports such as mesoporous silica / activated carbon / zeolite, loading Ag, TiO2, and ZnO onto the support. However, in this scheme, all three components are uniformly metal / metal oxides, and the mechanism remains a simple superposition of dissolution and photocatalysis. The use of the precious metal silver significantly increases costs, and the burst release effect of Ag⁺ also poses a biosafety risk. For example, CN117621553B discloses a silicate-based antibacterial material with a double-layer coating structure, the inner layer being Y2O3 and TiO2 and the outer layer being Ag. Although it adopts a spatial layered design, both the inner and outer layers are inorganic metal oxides, the mechanism is simple, and the high-temperature calcination process during preparation consumes a lot of energy, which is not conducive to large-scale production.

[0004] In addition, existing porous carrier antibacterial composite materials generally have the following common defects: (1) The carriers are mostly zeolite, mesoporous silica, activated carbon or metal-organic framework (MOF) materials. The lack of functional groups on the surface of zeolite and silica leads to poor loading strength. MOF materials are prone to the breakage of coordination bonds and degradation to release metal ions in humid or physiological environments. Activated carbon is difficult to achieve the directional spatial distribution of functional components. (2) The loading method of two components is mostly one-step impregnation and blending. The two components are randomly distributed on the carrier and cannot achieve spatial partitioning, which leads to mutual interference of action sites and greatly reduces the synergistic effect. (3) The burst release problem of metal antibacterial components has not been effectively suppressed. The rapid release of a large number of metal ions in the initial stage not only causes waste, but may also be toxic to human cells.

[0005] Therefore, there is an urgent need in this field to develop a novel two-component synergistic antibacterial composite material, which requires that the two components have truly complementary mechanisms of action, reasonable and controllable spatial distribution, strong bonding between the carrier and functional components, and simple and controllable preparation process, so as to ensure both high efficiency and broad-spectrum antibacterial effect while taking into account long-term effectiveness and safety. Summary of the Invention

[0006] The purpose of this invention is to provide a solution to the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A two-component synergistic antibacterial composite material based on a porous carrier includes a core-shell porous carrier, a first component copper-based nanoclusters confined within the pores of the carrier, and a second component quaternized chitosan anchored to the outer surface of the carrier. The core-shell porous carrier uses diatomaceous earth as the core and mesoporous polydopamine as the shell, with a shell pore size of 2-20 nm and a specific surface area of ​​≥350 m² / g. The first component, copper-based nanoclusters, are The core-shell structure exists within the pores of the carrier, with a particle size of 3-8 nm; The second component, quaternized chitosan, is bridged to the outer surface of the carrier by a silane coupling agent γ-APS, with a degree of substitution ≥85%. The mass ratio of the first component to the second component is 1:1-4.

[0008] As a preferred embodiment of the present invention: Cu in the copper-based nanoclusters 0 The molar ratio with Cu⁺ is 1:1.5-3, and the inner wall of the carrier pores... Functional group and copper cluster coordination confinement region.

[0009] As a preferred embodiment of the present invention, the quaternized chitosan has a degree of quaternization substitution of 85-95% and a molecular weight of 50-200 kDa.

[0010] As a preferred embodiment of the present invention: a method for preparing a two-component synergistic antibacterial composite material based on a porous carrier, characterized by comprising the following steps in sequence: (1) Preparation of core-shell porous carrier: Disperse diatomaceous earth in Tris buffer, add dopamine hydrochloride to a concentration of 2-4 g / L, stir at room temperature for 12-24 h, filter, wash with deionized water, dry at 60 °C, and then treat in 1 M KOH methanol solution at 60 °C for 2-4 h to form pores, and obtain diatomaceous earth@mesoporous polydopamine core-shell porous microspheres; (2) Pore-confined copper cluster loading: Core-shell porous microspheres were immersed in 0.05-0.2 mm pores. Aqueous solution, sonicated for 20-40 min, ascorbic acid solution (Cu²⁺:AA=1:2-4, molar ratio) was added dropwise, reduced at 35-50℃ for 1-3 h under nitrogen protection, filtered, washed with deionized water, and dried under vacuum at 50℃ to obtain Cu / Cu₂O@carrier; (3) Surface quaternized chitosan anchoring: Disperse Cu / Cu2O@carrier in anhydrous ethanol, add γ-APS to a concentration of 1-3wt%, reflux at 75℃ for 2-4h to obtain aminated carrier; separately dissolve chitosan in 1wt% acetic acid, add GTMAC to GTMAC: chitosan repeating unit = 3:1-6:1, react at 60-70℃ for 6-10h to obtain quaternized chitosan solution; immerse the aminated carrier in the quaternized chitosan solution, shake at 40-50℃ for 4-8h, filter, wash with deionized water, freeze dry to obtain the final product.

[0011] As a preferred embodiment of the present invention: in step (1), the diatomaceous earth is first acid-washed with 0.5-1M HCl at 60℃ for 2-4 hours to remove impurities, and then alkaline-washed with 0.5-1M NaOH at 80℃ for 2-4 hours to activate the surface silanol groups.

[0012] As a preferred embodiment of the present invention: the pH of the reduction reaction in step (2) is maintained at 7.5-8.5 throughout, and is adjusted by ammonia.

[0013] Compared with the prior art, the beneficial effects of the present invention are: This invention selects copper-based nanoclusters as the first component, whose mechanism of action is primarily contact killing, supplemented by trace copper ion dissolution, which can disrupt bacterial cell membrane integrity and interfere with intracellular enzyme activity. Quaternized chitosan is selected as the second component; its positively charged quaternary ammonium groups can electrostatically adsorb onto the negatively charged bacterial cell membrane, disrupting membrane permeability and causing intracellular leakage. The two components act on different targets of bacteria, forming a positive synergistic effect rather than a simple additive one. Experimental measurements showed that the fractional inhibitory concentration index (FIC) of both components was ≤ 0.48, far less than the synergistic threshold of 0.5, confirming a genuine synergistic antibacterial effect, rather than the "pseudo-synergistic" effect commonly seen in the field.

[0014] This invention employs a gradient loading process of "pore-confined reduction + surface silane bridging" to confine the first component, copper-based nanoclusters, within the mesoporous channels of a carrier, while anchoring the second component, quaternized chitosan, to the outer surface of the carrier, thus achieving physical spatial partitioning of the two components. The pore-confining effect physically encapsulates the copper-based nanoclusters within the carrier shell, significantly reducing the contact area with the external medium and extending the diffusion path of copper ions, thereby effectively suppressing the burst release of metal ions. Tests show that the cumulative copper ion leaching of the composite material under simulated use conditions for 28 days is less than 0.5 ppm, far lower than the physically blended control group (approximately 0.9 ppm), significantly improving the material's safety and long-term effectiveness.

[0015] This invention utilizes diatomaceous earth@mesoporous polydopamine core-shell porous microspheres as a carrier. Natural diatomaceous earth provides structural support and a low-cost foundation through a rigid core, while polydopamine provides abundant catechols and amino functional groups through a shell. The polydopamine shell can strongly coordinate with copper ions through complexation, firmly anchoring copper clusters within the pores during subsequent reduction and preventing migration and aggregation. Furthermore, the residual active groups on its surface can react with silane coupling agents, providing covalent grafting sites for the second component, quaternized chitosan. Compared to traditional zeolite or silica carriers that rely solely on van der Waals forces or weak electrostatic adsorption to load functional components, the carrier of this invention exhibits significantly enhanced binding force with the two components, making it less prone to loss or detachment of functional components during use or washing.

[0016] Because the synergistic effect of the two components covers different bacterial targets and physiological processes, the composite material of this invention exhibits excellent killing effects against Gram-positive bacteria (such as Staphylococcus aureus), Gram-negative bacteria (such as Escherichia coli), and multidrug-resistant strains (such as MRSA). Particularly noteworthy is that the contact killing effect of copper-based nanoclusters can disrupt extracellular polymeric substances (EPS) in the biofilm matrix, creating channels for quaternized chitosan to penetrate deep into the biofilm. The combination of these two components enables the present invention to achieve a clearance rate of over 90% against mature bacterial biofilms, far superior to single-component or simple blending solutions, and has significant application value in medical dressings and catheter coatings.

[0017] This invention utilizes a liquid-phase reaction throughout, eliminating the need for high-temperature calcination or high-pressure equipment. Dopamine spontaneously oxidizes and polymerizes on the surface of diatomaceous earth under mild conditions to form a shell, which can then be pore-created through alkaline treatment. The confined deposition of copper clusters can be achieved through room-temperature reduction with ascorbic acid. The grafting reaction of quaternized chitosan can be carried out under ambient pressure and heating conditions. The entire process is simple to operate, operates under mild conditions, and consumes little energy. The raw materials used are diatomaceous earth, a natural mineral, and chitosan, a natural polysaccharide extracted from crustacean waste, which are widely available and environmentally friendly, demonstrating promising prospects for industrial-scale production. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In this embodiment of the invention, a two-component synergistic antibacterial composite material based on a porous carrier includes a core-shell porous carrier, a first component copper-based nanoclusters confined within the pores of the carrier, and a second component quaternized chitosan anchored to the outer surface of the carrier. The core-shell porous carrier uses diatomaceous earth as the core and mesoporous polydopamine as the shell, with a shell pore size of 2-20 nm and a specific surface area of ​​≥350 m² / g. The first component, copper-based nanoclusters, are The core-shell structure exists within the pores of the carrier, with a particle size of 3-8 nm; The second component, quaternized chitosan, is bridged to the outer surface of the carrier by a silane coupling agent γ-APS, with a degree of substitution ≥85%. The mass ratio of the first component to the second component is 1:1-4.

[0020] As a preferred embodiment of the present invention: Cu in the copper-based nanoclusters 0 The molar ratio with Cu⁺ is 1:1.5-3, and the inner wall of the carrier pores... Functional group and copper cluster coordination confinement.

[0021] As a preferred embodiment of the present invention, the quaternized chitosan has a quaternization degree of 85-95% and a molecular weight of 50-200 kDa.

[0022] As a preferred embodiment of the present invention: a method for preparing a two-component synergistic antibacterial composite material based on a porous carrier, characterized by comprising the following steps in sequence: (1) Preparation of core-shell porous carrier: Disperse diatomaceous earth in Tris buffer, add dopamine hydrochloride to a concentration of 2-4 g / L, stir at room temperature for 12-24 h, filter, wash with deionized water, dry at 60 °C, and then treat in 1 M KOH methanol solution at 60 °C for 2-4 h to form pores, and obtain diatomaceous earth@mesoporous polydopamine core-shell porous microspheres; (2) Pore-confined copper cluster loading: Core-shell porous microspheres were immersed in 0.05-0.2 mm pores. Aqueous solution, sonicated for 20-40 min, ascorbic acid solution (Cu²⁺:AA=1:2-4, molar ratio) was added dropwise, reduced at 35-50℃ for 1-3 h under nitrogen protection, filtered, washed with deionized water, and dried under vacuum at 50℃ to obtain Cu / Cu₂O@carrier; (3) Surface quaternized chitosan anchoring: Disperse Cu / Cu2O@carrier in anhydrous ethanol, add γ-APS to a concentration of 1-3wt%, reflux at 75℃ for 2-4h to obtain aminated carrier; separately dissolve chitosan in 1wt% acetic acid, add GTMAC to GTMAC: chitosan repeating unit = 3:1-6:1, react at 60-70℃ for 6-10h to obtain quaternized chitosan solution; immerse the aminated carrier in the quaternized chitosan solution, shake at 40-50℃ for 4-8h, filter, wash with deionized water, freeze dry to obtain the final product.

[0023] As a preferred embodiment of the present invention: in step (1), the diatomaceous earth is first acid-washed with 0.5-1M HCl at 60℃ for 2-4 hours to remove impurities, and then alkaline-washed with 0.5-1M NaOH at 80℃ for 2-4 hours to activate the surface silanol groups.

[0024] As a preferred embodiment of the present invention: the pH of the reduction reaction in step (2) is maintained at 7.5-8.5 throughout, and is adjusted by ammonia.

[0025] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0026] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A two-component synergistic antibacterial composite material based on a porous carrier, characterized in that, It includes a core-shell porous carrier, a first component of copper-based nanoclusters confined within the carrier pores, and a second component of quaternized chitosan anchored to the outer surface of the carrier. The core-shell porous carrier uses diatomaceous earth as the core and mesoporous polydopamine as the shell, with a shell pore size of 2-20 nm and a specific surface area of ​​≥350 m² / g. The first component, copper-based nanoclusters, are The core-shell structure exists within the pores of the carrier, with a particle size of 3-8 nm; The second component, quaternized chitosan, is bridged to the outer surface of the carrier by a silane coupling agent γ-APS, with a degree of substitution ≥85%. The mass ratio of the first component to the second component is 1:1-4.

2. The composite material according to claim 1, characterized in that, Cu in copper-based nanoclusters 0 The molar ratio with Cu⁺ is 1:1.5-3, and the inner wall of the carrier pores... Functional group and copper cluster coordination confinement.

3. The composite material according to claim 1, characterized in that, The quaternized chitosan has a degree of quaternization substitution of 85-95% and a molecular weight of 50-200 kDa.

4. A method for preparing the composite material according to any one of claims 1-3, characterized in that, The steps are as follows: (1) Preparation of core-shell porous carrier: Disperse diatomaceous earth in Tris buffer, add dopamine hydrochloride to a concentration of 2-4 g / L, stir at room temperature for 12-24 h, filter, wash with deionized water, dry at 60 °C, and then treat in 1 M KOH methanol solution at 60 °C for 2-4 h to form pores, and obtain diatomaceous earth@mesoporous polydopamine core-shell porous microspheres; (2) Pore-confined copper cluster loading: Core-shell porous microspheres were immersed in 0.05-0.2 mm pores. Aqueous solution, sonicated for 20-40 min, ascorbic acid solution (Cu²⁺:AA=1:2-4, molar ratio) was added dropwise, reduced at 35-50℃ for 1-3 h under nitrogen protection, filtered, washed with deionized water, and dried under vacuum at 50℃ to obtain Cu / Cu₂O@carrier; (3) Surface quaternized chitosan anchoring: Disperse Cu / Cu2O@carrier in anhydrous ethanol, add γ-APS to a concentration of 1-3wt%, reflux at 75℃ for 2-4h to obtain aminated carrier; separately dissolve chitosan in 1wt% acetic acid, add GTMAC to GTMAC: chitosan repeating unit = 3:1-6:1, react at 60-70℃ for 6-10h to obtain quaternized chitosan solution; immerse the aminated carrier in the quaternized chitosan solution, shake at 40-50℃ for 4-8h, filter, wash with deionized water, freeze dry to obtain the final product.

5. The preparation method according to claim 4, characterized in that, In step (1), the diatomaceous earth is first acid-washed with 0.5-1M HCl at 60℃ for 2-4 hours to remove impurities, and then alkaline-washed with 0.5-1M NaOH at 80℃ for 2-4 hours to activate the surface silanol groups.

6. The preparation method according to claim 4, characterized in that, Step (2) The reduction reaction is maintained at pH 7.5-8.5 throughout, adjusted by ammonia.