Method for regulating molecular movement of polyrotaxane ring

Abstract

The invention discloses a method for regulating and controlling movement of polyrotaxane ring molecules, which is characterized in that a part of coaxially adjacent ring molecules are connected through chemical bonds to realize regulation of the activity degree of the ring molecules. According to the invention, a bridging agent is added into a polyrotaxane system, and hydroxyl groups of coaxially adjacent ring molecules are bridged by using the bridging agent so as to regulate and control the ring locking degree of the polyrotaxane ring molecules, so that the ring-locked polyrotaxane is obtained. By adjusting the concentration of the bridging agent, the ring locking degree of coaxially adjacent ring molecules in the polyrotaxane material can be accurately regulated and controlled, the structural characteristics of the molecular level are converted into the macroscopic performance of the material, and accurate adjustment of the molecular movement of the polyrotaxane ring molecules and the performance of the material is realized. The ring-locked polyrotaxane prepared by the method regulates molecular movement by locking ring molecules through covalent bonds, is more controllable and repeatable compared with an environment regulation mode, has remarkable advantages in the biomedical fields such as drug delivery, controlled release or preparation of tissue and cell scaffolds, and greatly improves the application potential of polyrotaxane in biomedicine.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyrotaxane materials, and in particular, relates to a method for regulating the motion of polyrotaxane ring molecules. Background Art

[0002] Molecular machines can controllably change their relative positions in space through mechanical motion to achieve specific design goals. They have precise control performance, high selectivity and flexibility, and provide new tools and methods for the biomedical field. The emergence of artificial molecular machines such as catenanes, rotaxanes and molecular motors has made it possible to precisely control molecular motion. These breakthroughs have enabled synthetic materials to simulate the molecular motion mechanisms of natural organisms at the molecular level, opening up new ways to design more flexible and functional materials. Molecular motion is the core link between material structure and performance. By regulating molecular motion, the structural characteristics at the molecular level can be converted into the macroscopic properties of the material, thereby achieving precise regulation of the material properties. Polyrotaxane is another typical representative of molecular machines. It is assembled from a chain molecule (axis) and multiple ring molecules through host-guest interactions, and the large molecules (capping agents) at both ends of the axis prevent the ring from falling. Unlike traditional polymers, the ring units in polyrotaxanes are connected to the axis units through mechanical bonds rather than traditional covalent bonds, allowing the ring molecules to slide and rotate relatively freely on the axis, thus possessing molecular dynamics. The unique structural complexity and higher degree of freedom of polyrotaxane molecules make them closer to functional biomacromolecules with complex structures in nature, and the dynamics and mobility of the ring molecules can effectively enhance the interaction between the active structure modified on the ring molecules and the target molecules. Therefore, regulating the dynamics of polyrotaxane ring molecules is of great significance for optimizing their performance and improving their effects in biomedical applications.

[0003] The existing methods for regulating the molecular motion of polyrotaxane ring molecules mainly include temperature, pH and solvent, etc. These external conditions regulate the molecular motion of polyrotaxane ring molecules by affecting the interaction between ring molecules. Changes in temperature have a direct impact on the molecular motion of polyrotaxane ring molecules, which is mainly regulated by changing the kinetic energy of the molecules and the interaction forces between the molecules. As the temperature rises, the kinetic energy of the molecules increases, and the thermal motion of the molecules becomes more intense. For polyrotaxanes, the mobility of the ring molecules may be enhanced, allowing the ring molecules to slide or rotate more easily on the axis molecules. Changes in pH change the interaction between polyrotaxane ring molecules, such as changes in the acid-base environment, which may cause the hydrogen bonds on the ring molecules to break or reorganize, thereby affecting the relative motion of the ring molecules. Similarly, the properties of the solvent also have an important influence on the molecular motion of polyrotaxane rings, especially the polarity of the solvent, the solvation effect and the interaction with the polyrotaxane ring molecules. Polar solvents may interact with the polar groups on the polyrotaxane ring molecules, thereby affecting the interaction between the ring molecules themselves. These methods of regulating the movement of polyrotaxane ring molecules by changing the external environment all change the non-covalent forces between the ring molecules, and have poor controllability. In addition, due to the particularity and complexity of the in vivo environment, it is difficult to be perfectly compatible with the internal environment of the organism. Over-reliance on these external environmental factors may bring about biosafety issues, limiting the widespread application of polyrotaxane materials in the biomedical field.

[0004] Therefore, it is of great significance to provide a method to finely control the motion of ring molecules in polyrotaxanes to optimize the performance of polyrotaxanes and improve their applications in biomedicine. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects and deficiencies in the prior art and provide a method for regulating the motion of polyrotaxane ring molecules. The present invention can flexibly control the degree of ring locking of coaxially adjacent ring molecules in the polyrotaxane material by selecting a suitable bridging agent and adjusting the concentration of the bridging agent, thereby achieving precise regulation of the molecular motion of the polyrotaxane ring molecules and material properties.

[0006] The second object of the present invention is to provide a ring-locked polyrotaxane.

[0007] The third object of the present invention is to provide the use of the above-mentioned ring-locked polyrotaxane in the preparation of biomedical materials.

[0008] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a method for regulating the movement of polyrotaxane ring molecules, which connects some coaxially adjacent ring molecules through chemical bonds to achieve regulation of the activity degree of the ring molecules.

[0010] At present, the method of regulating the movement of polyrotaxane ring molecules by relying on external stimuli is often not perfectly compatible with the internal environment of the organism, which limits the wide application of polyrotaxane materials in the biomedical field. The present invention proposes a method for finely regulating the movement of polyrotaxane ring molecules by locking the ring. By selecting a suitable bridging agent and adjusting the concentration of the bridging agent, the degree of locking the coaxially adjacent ring molecules in the polyrotaxane material can be flexibly controlled, thereby achieving precise regulation of molecular motion and material properties. This method not only makes the motion behavior of polyrotaxane ring molecules more controllable, but more importantly, a series of polyrotaxane materials prepared by this method can achieve different ring molecule motion characteristics without changing the internal environment of the organism, greatly enhancing the biomedical application potential of polyrotaxane materials.

[0011] The present invention provides a ring-locked polyrotaxane, which comprises an axis molecule, a ring molecule, an end-capping structure, and a connection structure formed by chemical reaction between coaxially adjacent ring molecules and hydroxyl groups on adjacent ring molecules; the axis molecule is polyethylene glycol or a polyethylene glycol block copolymer; and the ring molecule is cyclodextrin.

[0012] Furthermore, the axle molecule is polyethylene glycol or a polyethylene glycol block copolymer with a molecular weight of 4000 to 35000 Da.

[0013] Preferably, the polyethylene glycol block copolymer is Pluronic L64 (poloxamer L64), Pluronic F127 (poloxamer F127) or Pluronic F68 (poloxamer F68).

[0014] Furthermore, the cyclic molecule is one of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin.

[0015] Furthermore, the end-capping structure is formed by the reaction of adamantane amine or 2,4-dinitrofluorobenzene with the terminal carboxyl group of the axle molecule.

[0016] Furthermore, the connection structure is formed by bridging the hydroxyl groups of coaxially adjacent ring molecules with a bridging agent; the bridging agent is one of epichlorohydrin or diisocyanate compounds.

[0017] Furthermore, the epichlorohydrin is used at a concentration of 0 to 0.508 mol / L (excluding the case where the concentration is 0, 0<C≤0.508 mol / L). Different concentrations of bridging agents can regulate the degree of ring locking of polyrotaxanes. Within a given range of bridging agent concentrations, bridging occurs only between coaxial ring molecules, while bridging bonds do not form between non-coaxial ring molecules. This is because the distance between coaxial ring molecules is the shortest and these ring molecules are threaded on the same axis, and their diffusion direction in the solution is relatively fixed, mainly manifested as axial sliding, so coaxial cyclodextrin molecules are more likely to be bridged. Only the bridging between coaxial ring molecules can effectively regulate the degree of ring locking of ring molecules on a single polyrotaxane molecule. When the concentration of the bridging agent exceeds this range, non-coaxial bridging will occur between cyclodextrin molecules, resulting in cross-linking between polyrotaxane molecules, and even cross-linking between three or more polyrotaxane molecules, thereby failing to effectively control the movement of ring molecules on the polyrotaxane axis. Gel permeation chromatography (GPC) analysis showed that within the bridging agent concentration range, the GPC spectrum showed a single peak, that is, there was no cross-linking between polyrotaxane molecules.

[0018] Preferably, when the concentration of the bridging agent epichlorohydrin used is ≤0.127 mol / L, after the bridging reaction is completed, the reaction solution is cooled to room temperature, dialyzed, and the polyrotaxane after the ring locking is separated; when the concentration of the bridging agent epichlorohydrin used is between 0.127 mol / L and 0.508 mol / L, after the bridging reaction is completed, the reaction solution is cooled to room temperature, dialyzed, and freeze-dried to obtain a crude product, which is then washed and filtered to obtain the polyrotaxane after the ring locking.

[0019] Furthermore, the method for using epichlorohydrin is to dissolve the polyrotaxane in any solution of sodium hydroxide, potassium hydroxide or potassium tert-butoxide, and then add epichlorohydrin. The role of sodium hydroxide is to deprotonate the hydroxyl groups on the polyrotaxane ring molecules and improve nucleophilicity. Because the polyrotaxane can be dissolved in a 1 mol / L sodium hydroxide solution, and acid will be generated during the reaction to neutralize part of the sodium hydroxide, the more bridging agent is added, the more sodium hydroxide is consumed. Therefore, in order to ensure that the sodium hydroxide concentration of the reaction system is 1 mol / L after the reaction is completed, the amount of sodium hydroxide used will vary according to the amount of the bridging agent used to avoid precipitation.

[0020] Furthermore, the diisocyanate compound is terephthalate diisocyanate or o-phthalate diisocyanate.

[0021] Preferably, the method for adding the terephthalate is to dissolve the polyrotaxane in DMSO and then add the terephthalate.

[0022] Furthermore, the average number of connection structures (bridge bonds) on each polyrotaxane ring molecule in the ring-locked polyrotaxane is 1 to 6.

[0023] As a preferred embodiment, the present invention provides a specific method for preparing a ring-locked polyrotaxane, comprising the following steps:

[0024] S1. Polyrotaxanes were synthesized by heterogeneous reaction using polyethylene glycol (molecular weight ranging from 4000 to 35000 Da) as the axis molecule, α-cyclodextrin as the ring molecule, and adamantane amine as the end-capping agent;

[0025] S2. Dissolve the polyrotaxane in a sodium hydroxide solution, slowly add a bridging agent, epichlorohydrin, and lock the ring molecules through the hydroxyl groups on the bridging ring molecules to control the molecular motion of the polyrotaxane ring molecules, thereby obtaining a locked-ring polyrotaxane.

[0026] Furthermore, the step S1 is to firstly carboxylate the terminal of polyethylene glycol, then react with α-cyclodextrin to obtain a pseudopolyrotaxane intermediate, and finally react the pseudopolyrotaxane intermediate with adamantane amine to obtain the final product polyrotaxane.

[0027] Specifically, when the concentration of the bridging agent epichlorohydrin is ≤0.127 mol / L, after the reaction in step S2 is completed, the reaction solution is cooled to room temperature, dialyzed, and the polyrotaxane after the ring lock is separated; when the concentration of the bridging agent epichlorohydrin is between 0.127 mol / L and 0.508 mol / L, after the reaction in step S2 is completed, the reaction solution is cooled to room temperature, dialyzed, and freeze-dried to obtain a crude product, which is then washed and filtered to obtain the polyrotaxane after the ring lock. According to the above steps, polyrotaxanes with different degrees of ring lock can be obtained, and the molecular motion speed of the ring molecules is characterized by variable temperature nuclear magnetic resonance, and the polyrotaxane material prepared by the regulation method can be used in vivo.

[0028] The application of polyrotaxane in the biomedical field is of great significance. For example, polyrotaxane materials can be used as drug sustained-release carriers. By utilizing their molecular motion characteristics, polyrotaxanes can slowly deliver drugs to where the body needs them. Especially for patients with chronic diseases who need long-term medication, this carrier can significantly reduce the number of medications patients take and improve the treatment effect. Secondly, polyrotaxanes also have important applications in tissue engineering. It can be used as a scaffold material to help cell growth and tissue repair. The molecular motion characteristics of polyrotaxanes enable it to construct a scaffold with a suitable microenvironment, providing a good growth platform for cells. In addition, polyrotaxane materials can also be used to prepare high-performance biomedical composite materials. By mixing with other materials, polyrotaxanes can significantly improve the performance of composite materials, such as toughness and corrosion resistance, thereby meeting the high requirements for material performance in the biomedical field. The molecular motion of the ring molecules on the polyrotaxane is precisely controlled by the locking ring method, so that the polyrotaxane materials with different molecular motion properties can be used in vivo. Moreover, the locking ring polyrotaxane can maintain the stability of the molecular structure under a wider range of environmental conditions by linking the ring molecules on the coaxial polyrotaxane through covalent bonds. By bridging ring molecules, the degree of ring locking of polyrotaxanes can be precisely controlled, thereby adjusting the physical and chemical properties of polyrotaxanes. This precise control is more controllable and repeatable than environmental control methods (such as temperature and pH). For some specific biological environments, changes in environmental factors may cause instability in the movement of polyrotaxanes, and the regulation of the molecular movement of its ring molecules by ring-locked polyrotaxanes provides a solution that is relatively independent of external conditions, which makes it more advantageous in biomedical applications such as drug delivery.

[0029] Therefore, the present invention provides the use of the above-mentioned ring-locked polyrotaxane in the preparation of biomedical materials.

[0030] Furthermore, the biomedical material is a material used for drug delivery, controlled release or preparation of tissues and cell scaffolds.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a method for regulating the motion of polyrotaxane ring molecules, the method comprising connecting some coaxially adjacent ring molecules by chemical bonds to achieve the regulation of the activity degree of the ring molecules. The present invention adds a bridging agent to the polyrotaxane system, and uses the bridging agent to bridge the hydroxyl groups of the coaxially adjacent ring molecules to regulate the degree of ring locking of the polyrotaxane ring molecules, thereby obtaining a ring-locked polyrotaxane, the polyrotaxane comprising an axis molecule, a ring molecule, an end-capping structure, and a connection structure formed by chemical reaction between coaxially adjacent ring molecules and hydroxyl groups on adjacent ring molecules; the axis molecule is polyethylene glycol or a polyethylene glycol block copolymer; and the ring molecule is cyclodextrin. By adjusting the concentration of the bridging agent, the degree of ring locking of coaxially adjacent ring molecules in the polyrotaxane material can be precisely regulated, and the structural characteristics at the molecular level can be converted into the macroscopic properties of the material, thereby achieving the precise regulation of the molecular motion of the polyrotaxane ring molecules and the material properties. The ring-locked polyrotaxane prepared by this method uses covalent bonds to lock the ring molecules to regulate molecular motion. Compared with environmental regulation methods, it is more controllable and repeatable. It has significant advantages in biomedical fields such as drug delivery, controlled release, or preparation of tissues and cell scaffolds, greatly enhancing the application potential of polyrotaxanes in biomedicine. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the synthesis of ring-locked polyrotaxane.

[0034] Figure 2 is the H NMR spectrum of polyrotaxane PR ( 1 H NMR, DMSO-d6, 298K).

[0035] Figure 3 is the hydrogen nuclear magnetic resonance spectrum of the ring-locked polyrotaxane PR (1.1) prepared according to Example 1 ( 1 H NMR, DMSO-d6, 298K).

[0036] Figure 4 is the hydrogen nuclear magnetic resonance spectrum of the ring-locked polyrotaxane PR (2.1) prepared according to Example 2 ( 1 H NMR, DMSO-d6, 298K).

[0037] Figure 5 is the hydrogen nuclear magnetic resonance spectrum of the ring-locked polyrotaxane PR (3.8) prepared according to Example 3 ( 1 H NMR, DMSO-d6, 298K).

[0038] Figure 6 The nuclear magnetic resonance hydrogen spectrum of the ring-locked polyrotaxane PR (5.9) prepared according to Example 4 ( 1 H NMR, DMSO-d6, 298K).

[0039] Figure 7The variable temperature NMR spectrum (VT 1 H NMR, DMSO-d6).

[0040] Figure 8 The variable temperature NMR spectrum (VT 1 H NMR, DMSO-d6).

[0041] Fig. 9 The variable temperature NMR spectrum (VT 1 H NMR, DMSO-d6).

[0042] Fig.10 The variable temperature NMR spectrum (VT 1 H NMR, DMSO-d6).

[0043] Fig.11 The variable temperature NMR spectrum (VT 1 H NMR, DMSO-d6).

[0044] Fig.12 The gel permeation chromatograms of the ring-locked polyrotaxanes prepared according to Examples 1 to 4 are shown in FIG. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0046] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0047] Example 1 Synthesis of polyrotaxane and polyrotaxane ring-locking reaction

[0048] 1. Synthesis method

[0049] (1) Synthesis of terminal carboxyl polyethylene glycol

[0050] Weigh 30g of polyethylene glycol (35k-PEG, 30.0g, 0.86mmol, -OH 1.7mmol) in a reaction bottle, add 300mL of pure water, stir until PEG is completely dissolved, add 2,2,6,6-tetramethylpiperidinoxide (TEMPO, 300mg, 1.92mmol) to the above solution and stir until completely dissolved. Then add sodium bromide (NaBr, 3.0g, 30mmol)) and sodium hypochlorite (NaClO, 15mL, effective chlorine>5.0%) solution in sequence, stir and react at room temperature for 15 minutes. After the reaction is completed, add 10mL of ethanol to quench the reaction, and then adjust the pH to <2 with hydrochloric acid solution. The reaction solution is extracted with dichloromethane, the lower organic phase is taken, and after rotary evaporation and concentration, the concentrate is slowly poured into ether for precipitation, the precipitate is collected by suction filtration, and the terminal carboxyl polyethylene glycol 35k-PEG-(COOH)2 is obtained after vacuum drying.

[0051] (2) Polyrotaxane synthesis

[0052] Dissolve terminal carboxyl polyethylene glycol (35k-PEG-(COOH)2, 12.0 g, 0.34 mmol) and α-cyclodextrin (α-CD, 48.0 g, 49.4 mmol) in deionized water, respectively, wherein 35k-PEG-(COOH)2 is dissolved in 60 mL of pure water, and α-CD is dissolved in 300 mL of pure water (heated in a 60°C water bath to promote dissolution). Subsequently, the 35k-PEG-(COOH)2 aqueous solution is slowly added dropwise to the α-CD aqueous solution, and the system is stirred evenly during the addition. After the addition is completed, the reaction system is stirred continuously at 60°C for 6 hours to allow the hydrophobic segments of 35k-PEG-(COOH)2 and the cavities of α-CD to self-assemble to form a pseudopolyrotaxane structure through host-guest interactions. After the reaction is completed, the generated white paste is freeze-dried, and the solvent is removed to obtain a pseudopolyrotaxane (PPR) intermediate product.

[0053] Next, weigh pseudopolyrotaxane (PPR, 15.0 g, 0.09 mmol), 1-adamantanamine (Ad-NH2, 1.3 g, 8.6 mmol) and Carter condensation agent (BOP, 0.38 g, 0.86 mmol) in a reaction vessel and mix them thoroughly by solid shaking or mechanical stirring. Subsequently, about 5 mL of anhydrous N,N-dimethylformamide (DMF) was slowly added to the mixture to wet the reaction system, and then N,N-diisopropylethylamine (DIPEA, 0.15 mL, 0.86 mmol) solution dispersed with 1 mL of anhydrous DMF was added dropwise, and anhydrous DMF was continued to be added dropwise until the system formed a thick mud. During the process, the amount of DMF was strictly controlled and the drop volume was recorded to ensure that the reaction system was in a heterogeneous state. The reaction mixture was continuously stirred overnight at 4 ° C to allow 1-adamantanamine and the terminal carboxyl groups of the pseudopolyrotaxane to undergo amidation reaction under the catalysis of BOP and DIPEA. After the reaction was completed, the mixture was washed twice with a DMF / methanol (1:1, v / v) mixed solution and twice with methanol, and stirred for 30 minutes each time. The washed product was dissolved in an appropriate amount of DMSO and added to water for reprecipitation. The product precipitate was collected by centrifugation (10000 rpm, 10 minutes), and then washed with excess water to remove excess solvent and impurities. The resulting off-white solid was freeze-dried to obtain a polyrotaxane (PR) capped with adamantaneamine.

[0054] (3) Polyrotaxane ring-locking reaction

[0055] The blocked polyrotaxane was dissolved in a sodium hydroxide aqueous solution (1.01 mol / L, 3 mL). After complete dissolution, the reaction solution was heated to 60°C and epichlorohydrin (EPI, bridging agent, 15 μL) was slowly added dropwise. The final concentration of epichlorohydrin was 0.0635 mol / L. The system was reacted at 60°C for 24 hours. After the reaction, the reaction solution was cooled to room temperature and dialyzed to remove small molecule impurities. The dialyzate was centrifuged to separate the white precipitate product, which was freeze-dried to obtain the ring-locked polyrotaxane, which was recorded as PR (1.1).

[0056] 2. Result Verification

[0057] The synthesis diagram of the ring-locked polyrotaxane is shown in Figure 1 As shown, the axis molecules pass through the cavity of the ring molecules through host-guest interactions, and the ends of the axis molecules are capped with large steric groups to prevent the ring molecules from sliding out. The ring molecules on the axis of the polyrotaxane can slide and rotate along the axis.

[0058] The H NMR spectrum of polyrotaxane PR ( 1 H NMR, DMSO-d6, 298K) Figure 2As shown, the diffusion rate of free cyclodextrin molecules is high, which allows them to move freely and quickly in the solution, so the signal is relatively single and evenly distributed, resulting in the characteristic peaks of cyclodextrin molecules usually showing high and sharp peaks in the nuclear magnetic resonance spectrum. When cyclodextrin is threaded on the polyethylene glycol axis to form a polyrotaxane structure, the diffusion rate of cyclodextrin is affected by the PEG chain. Due to the large molecular weight of the PEG chain, its hydrodynamic volume in the solution is large, and the forces it is subjected to in the solution are more complex. The forces in all directions may offset each other, making it difficult to form a combined force to drive the movement of molecules, so the diffusion rate is low. The cyclodextrin molecules are fixed on the PEG chain. The restrictive effect of this structure reduces the diffusion rate of cyclodextrin, causing the characteristic peaks of cyclodextrin to become shorter and wider. The short and wide characteristic peaks of cyclodextrin can be seen from the nuclear magnetic resonance hydrogen spectrum of the polyrotaxane, which indicates that the cyclodextrin molecules have been effectively restricted on the PEG axis, proving the successful synthesis of the polyrotaxane molecules. Further analysis of the NMR data revealed that the average number of rings per axis in the polyrotaxane molecule was 105, with a ring penetration rate of 26.5%.

[0059] In order to achieve precise control of the motion of the ring molecules on the polyrotaxane axis, epichlorohydrin was used as a bridging agent to further control the molecular motion of the ring molecules by forming a bridging bond between the ring molecules. The key to this bridging strategy is to use epichlorohydrin molecules to react with the hydroxyl groups on the cyclodextrin molecules to form a stable covalent bridging bond, thereby limiting the free rotation of the ring molecules on the polyethylene glycol axis. When the concentration of epichlorohydrin used was 0.0635 mol / L, the H NMR spectrum of the prepared locked-ring polyrotaxane PR (1.1) was ( 1 H NMR, DMSO-d6, 298K) Figure 3 As shown, through integral calculation, it is found that the average number of rings per axis of the locked-ring polyrotaxane PR (1.1) is 105, the ring penetration rate is 26.5%, and the average number of bridging bonds per ring is 1.1.

[0060] Example 2 Polyrotaxane Ring Locking Reaction

[0061] 1. Synthesis method

[0062] The method for synthesizing polyrotaxane is the same as (1) and (2) in Example 1, except that:

[0063] (3) The blocked polyrotaxane was dissolved in a NaOH aqueous solution (1.03 mol / L, 3 mL). After complete dissolution, the reaction solution was heated to 60°C and epichlorohydrin (EPI, 30 μL) was slowly added dropwise. The final concentration of epichlorohydrin was 0.127 mol / L. The system was reacted at 60°C for 24 hours. After the reaction, the reaction solution was cooled to room temperature and dialyzed to remove small molecule impurities. The dialyzate was centrifuged to separate the white precipitate product, which was freeze-dried to obtain the polyrotaxane after ring locking, which was recorded as PR (2.1).

[0064] 2. Result Verification

[0065] When the concentration of epichlorohydrin used is 0.127 mol / L, the H NMR spectrum of the prepared ring-locked polyrotaxane PR (2.1) is ( 1 H NMR, DMSO-d6, 298K) Figure 4 As shown, through integral calculation, it is found that the average number of rings per axis of the locked-ring polyrotaxane PR (2.1) is 105, the ring penetration rate is 26.5%, and the average number of bridging bonds per ring is 2.1.

[0066] Example 3 Polyrotaxane Ring Locking Reaction

[0067] 1. Synthesis method

[0068] The method for synthesizing polyrotaxane is the same as (1) and (2) in Example 1, except that:

[0069] (3) The blocked polyrotaxane was dissolved in a NaOH aqueous solution (1.05 mol / L, 3 mL). After complete dissolution, the reaction solution was heated to 60°C and epichlorohydrin (EPI, 60 μL) was slowly added dropwise. The final concentration of epichlorohydrin was 0.254 mol / L. The system was reacted at 60°C for 24 hours. After the reaction was completed, the reaction solution was cooled to room temperature and dialyzed to remove small molecule impurities. Then, the crude product was freeze-dried to obtain a crude product. The freeze-dried crude product was washed with an appropriate amount of anhydrous dichloromethane, stirred at room temperature for 24 hours, and separated by suction filtration to obtain a white solid product. The product was vacuum dried at room temperature for 24 hours to obtain a ring-locked polyrotaxane, which was recorded as PR (3.8).

[0070] 2. Result Verification

[0071] When the concentration of epichlorohydrin used is 0.254 mol / L, the H NMR spectrum of the prepared ring-locked polyrotaxane PR (3.8) is ( 1 H NMR, DMSO-d6, 298K) Figure 5 As shown, through integral calculation, it is found that the average number of rings per axis of the locked-ring polyrotaxane PR (3.8) is 105, the ring penetration rate is 26.5%, and the average number of bridging bonds per ring is 3.8.

[0072] Example 4 Polyrotaxane Ring Locking Reaction

[0073] 1. Synthesis method

[0074] The method for synthesizing polyrotaxane is the same as (1) and (2) in Example 1, except that:

[0075] (3) The blocked polyrotaxane was dissolved in a NaOH aqueous solution (1.1 mol / L, 3 mL). After complete dissolution, the reaction solution was heated to 60°C and epichlorohydrin (EPI, 120 μL) was slowly added dropwise. The final concentration of epichlorohydrin was 0.508 mol / L. The system was reacted at 60°C for 24 hours. After the reaction was completed, the reaction solution was cooled to room temperature and dialyzed to remove small molecule impurities. The crude product was then freeze-dried to obtain a crude product. The freeze-dried crude product was washed with an appropriate amount of anhydrous dichloromethane, stirred at room temperature for 24 hours, and separated by suction to obtain a white solid product. The product was vacuum dried at room temperature for 24 hours to obtain a ring-locked polyrotaxane, which was recorded as PR (5.9).

[0076] 2. Result Verification

[0077] When the concentration of epichlorohydrin used is 0.508 mol / L, the H NMR spectrum of the prepared ring-locked polyrotaxane PR (5.9) is ( 1 H NMR, DMSO-d6, 298K) Figure 6 As shown, through integral calculation, it is found that the average number of rings per axis of the locked-ring polyrotaxane PR(5.9) is 105, the ring penetration rate is 26.5%, and the average number of bridging bonds per ring is 5.9.

[0078] By adjusting the amount of the bridging agent and the reaction conditions, the synthesis of polyrotaxanes with different degrees of ring locking can be achieved. Figures 3 to 6 The H NMR spectra of the ring-locked polyrotaxanes PR(1.1), PR(2.1), PR(3.8) and PR(5.9) prepared according to Examples 1 to 4 are shown ( 1 H NMR, DMSO-d6, 298K), the characteristic peak of the hydroxyl group on the newly formed bridging bond confirmed the successful synthesis of the locked-ring polyrotaxane. Further analysis of the number of hydroxyl groups reduced in the NMR spectrum can infer the number of bridging bonds on each cyclodextrin molecule.

[0079] Example 5: Exploring the relationship between the molecular motion of the ring molecules on the polyrotaxane axis and the degree of ring locking

[0080] In order to further study the relationship between the molecular motion of the ring molecules on the polyrotaxane axis and the degree of ring locking, polyrotaxane solutions with different degrees of ring locking were prepared, and the molar concentration of the ring molecules in each sample was ensured to be the same. The variable temperature H NMR spectroscopy (VT H NMR) was performed in the range of 25 to 80 °C. 1 H NMR) experiments were performed to observe the changes in the motion of the ring molecules of the ring-locked polyrotaxane under different temperature conditions.

[0081] The results are as follows Figure 7 As shown, the variable temperature NMR spectrum of polyrotaxane PR is shown. Figures 8 to 11 These are the variable temperature NMR spectra of the locked ring polyrotaxanes PR(1.1), PR(2.1), PR(3.8) and PR(5.9) prepared according to Examples 1 to 4, respectively. The differences in the motion of the ring molecules are reflected in the changes in the peak shape of the ring molecules -OH-2,3, H-1, and OH-6 with temperature. As the temperature rises from 25°C to 80°C, the peak shape becomes higher and narrower with temperature change, and the signal becomes stronger, indicating that the molecular motion of the ring molecules is faster. Figures 7 to 11 It can be seen that the movement of the ring molecules in polyrotaxanes with different degrees of ring locking shows obvious differences. Specifically, when the temperature rises from 25°C to 80°C, the peak shapes of the characteristic peaks such as -OH-2,3, H-1, and OH-6 of the PR and PR(1.1) samples change most significantly under temperature changes. The peak shapes become sharper with increasing temperature, and the signal intensity increases, indicating that the cyclodextrin molecules in these samples have faster molecular motion. In the ring-locked polyrotaxanes PR(2.1) and PR(3.8), the amplitude of the morphological changes of the characteristic peaks of the ring molecules is smaller than that of PR(1.1), indicating that the movement speed of the ring molecules in these samples is relatively slow. In contrast, the characteristic peaks of the ring molecules of the ring-locked polyrotaxane PR(5.9) have almost no obvious changes when the temperature rises, indicating that its ring molecules move the slowest.

[0082] Based on the above experimental data, as the degree of ring locking increases, the bridging effect between ring molecules increases, which restricts the free rotation of the molecules and causes the movement of the ring molecules to gradually slow down, which ultimately manifests as smaller peak changes and weaker signal enhancement in the variable temperature NMR spectrum. Figures 7 to 11 It can be inferred from the variable temperature NMR data that the degree of ring locking of the polyrotaxane directly affects the mobility of the ring molecules on its axis. The higher the degree of ring locking, the more restricted the molecular motion is, which has a certain controllability in regulating the molecular motion of the polyrotaxane ring molecules.

[0083] The gel permeation chromatography (GPC) spectra of the polyrotaxane and the ring-locked polyrotaxane prepared according to Examples 1 to 4 are as follows: Fig.12As shown in the figure, by analyzing these spectra, it can be concluded that the elution time before and after the polyrotaxane ring lock changes very little, indicating that the molecular weight has not increased significantly. This shows that at a given bridging agent concentration, the polyrotaxane does not undergo large-scale cross-linking during the ring lock process, and the role of the bridging agent is mainly to connect coaxially adjacent cyclodextrin molecules to form bridging bonds.

[0084] Example 6 Synthesis of Ring-Locked Polyrotaxane

[0085] The method for synthesizing polyrotaxane (PR) is the same as steps (1) and (2) of Example 1.

[0086] 1g of polyrotaxane was dissolved in 30mL of anhydrous dimethyl sulfoxide (DMSO), and dibutyltin dilaurate (DBTDL, 20μL) was added as a catalyst under nitrogen protection, and 2,6-di-tert-butyl-p-cresol (BHT, 1.0mg, 0.0047mmol) was pre-dissolved in 3mL of anhydrous DMSO. Subsequently, a solution of terephthalate (62mg, 160g / mol) dissolved in 3mL of anhydrous DMSO was slowly added dropwise, stirred evenly, and reacted at 40°C for 12h. After the reaction was completed, the obtained reaction solution was slowly poured into excess ice acetone for precipitation, and the precipitate was collected by centrifugation. The obtained precipitate was washed with acetone and then vacuum dried to obtain the final product.

[0087] Experimental results show that terephthalate can also be used as a bridging agent to adjust the degree of ring locking of polyrotaxane ring molecules.

Claims

1. A method for regulating the molecular motion of a polyrotaxane ring, characterized in that: Some coaxially adjacent ring molecules are connected by chemical bonds to adjust the activity level of the ring molecules.

2. A ring-locked polyrotaxane, characterized in that: The polyrotaxane comprises an axis molecule, a ring molecule, a capping structure, and a connection structure formed by chemical reaction between coaxially adjacent ring molecules and hydroxyl groups on adjacent ring molecules; the axis molecule is polyethylene glycol or a polyethylene glycol block copolymer; and the ring molecule is cyclodextrin.

3. The ring-locked polyrotaxane according to claim 2, characterized in that: The cyclic molecule is one of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin.

4. The ring-locked polyrotaxane according to claim 2, characterized in that: The end-capping structure is formed by the reaction of adamantane amine or 2,4-dinitrofluorobenzene with the terminal carboxyl group of the axle molecule.

5. The ring-locked polyrotaxane according to claim 2, characterized in that: The connection structure is formed by bridging the hydroxyl groups of coaxially adjacent ring molecules with a bridging agent; the bridging agent is one of epichlorohydrin or diisocyanate compounds.

6. The ring-locked polyrotaxane according to claim 5, characterized in that: The epichlorohydrin is used at a concentration of 0 to 0.508 mol / L.

7. The ring-locked polyrotaxane according to claim 5, characterized in that: The diisocyanate compounds are terephthalate diisocyanate and o-phthalate diisocyanate.

8. The ring-locked polyrotaxane according to claim 2, characterized in that: The average number of connection structures on each polyrotaxane ring molecule in the ring-locked polyrotaxane is 1 to 6.

9. Use of the ring-locked polyrotaxane according to any one of claims 2 to 8 in the preparation of biomedical materials.

10. The use according to claim 9, characterized in that: The biomedical material is a material used for drug delivery, controlled release or preparation of tissue and cell scaffolds.

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