Alginate fiber and preparation method thereof

Abstract

The invention relates to the technical field of alginate fiber preparation, and discloses an alginate fiber and a preparation method thereof.The preparation method comprises the steps that chemical modification is conducted on a sodium alginate macromolecular chain, a side chain group which can be controllably hydrolyzed and can catalyze main chain breakage is introduced, meanwhile, a weak covalent bond sensitive to spinning shear force is introduced, and reducing agent microcapsules are dispersed in a spinning solution; according to the invention, the disassembly of the main chain of the fiber is bound with an internal chemical reaction endpoint which is not influenced by external environmental fluctuation, so that the transformation of the fiber degradation behavior from passive environmental response to active programmed structure disassembly is realized; and in combination with a self-repairing quality control mechanism in the spinning process, the high uniformity and predictability of the programmed degradation performance in a final product are ensured.

Description

Technical Field

[0001] This invention relates to a seaweed fiber and its preparation method, belonging to the field of seaweed fiber preparation technology. Background Technology

[0002] In the field of synthetic fiber preparation technology, especially for seaweed fibers derived from natural polymers, wet spinning is a mature and widely used method that utilizes sodium alginate aqueous solution to undergo ionic cross-linking in a coagulation bath containing divalent cations to form alginate fibers with specific mechanical strength. The structural integrity of this fiber is essentially determined by two chemical structures with different properties: one is the ionic cross-linking network that provides macroscopic mechanical strength, and the other is the glycosidic bonds that constitute the polymer chain itself, which are chemically extremely stable under physiological conditions. Existing technologies for regulating fiber degradation behavior almost entirely focus on intervening in the ionic cross-linking network, controlling fiber disintegration by adjusting the rate of ion exchange.

[0003] However, when these fibers are used in applications requiring stable bearing within a specific time window before disassembly, the aforementioned ion exchange-dependent degradation method reveals its inherent limitations. In complex real-world environments, the types, concentrations, and pH levels of ions in the surrounding medium are constantly changing. This makes the fiber's performance degradation process directly subject to unpredictable external variables, rendering the accuracy of its functional lifespan impossible. Simply enhancing the ion crosslinking strength or adding a physical coating to improve its controllability does not change the fact that its degradation is driven by the external environment. The former merely delays a random process, while the latter introduces new issues regarding the controllability or residue of the coating's own degradation.

[0004] Specifically, existing technologies have the following shortcomings: 1. The initiation and process of fiber degradation are entirely dependent on the external environment, lacking an internal, autonomous control mechanism; 2. The mechanical property decay curve of the fiber is difficult to predetermine, and the timing of functional failure is unpredictable; 3. The long-term structural stability of the fiber and its eventual rapid and complete disintegration are mutually restrictive under this passive-response degradation mode, making it difficult to achieve both simultaneously. Therefore, the technical problem to be solved by this invention is how to implant a pre-set timing mechanism, determined by its own chemical characteristics and unaffected by external environmental fluctuations, into the macromolecular chemical structure of seaweed fibers, and how to trigger the breakage of the fiber backbone at a predetermined time point through this mechanism, thereby achieving programmed control of the fiber life cycle. Summary of the Invention

[0005] This invention provides seaweed fiber and its preparation method. Its main purpose is to solve the problem of implanting a pre-programmed self-degradation mechanism into the chemical structure of seaweed fiber, which is determined by itself and is not affected by external environmental fluctuations.

[0006] To achieve the above objectives, the present invention provides a method for preparing seaweed fiber, the method comprising: The carboxyl group on the sodium alginate macromolecular chain is chemically modified to introduce side chain chemical groups by covalent bonds. The side chain chemical groups contain an ester bond whose hydrolysis rate is determined by its chemical structure. After the ester bond is hydrolyzed, the side chain chemical groups release catalytic functional groups that can catalyze the breaking of the glycosidic bond in the main chain. In the chemical modification, weak covalent bonds that are sensitive to shear force are also introduced, which are generated by the reaction of functional groups on the sodium alginate macromolecular chain with aldehyde compounds. Chemically modified alginate was formulated into a spinning solution, and reducing agent microcapsules were dispersed in the spinning solution. The reducing agent microcapsules could be activated by the products of weak covalent bond breaking. In the spinning extrusion step, shear stress is used to break the weak covalent bonds on the molecular chains with uneven molecular weight in the spinning solution. The broken products activate the reducing agent microcapsules to release the reducing agent, which repairs the broken molecular chain ends. The spinning solution is extruded into a coagulation bath containing divalent cations, and seaweed fibers are formed through ionic cross-linking.

[0007] Preferably, in the chemical modification, the proportion of side chain chemical groups introduced is 1 to 5 per 100 alginate repeating units.

[0008] Preferably, the chemical structure of the ester bond is selected such that its hydrolysis half-life corresponds to a time range of several days to several months.

[0009] Preferably, the shear-sensitive weak covalent bond is generated by the reaction of an amino group or hydroxyl group on the alginate chain with a dialdehyde or acetal; the reducing agent microcapsules are microcapsules encapsulated with an inert coating and contain at least one reducing agent selected from thiols and ascorbic acid.

[0010] Preferably, the chemical modification also introduces a molecular group with a temperature-sensitive conformational change. The molecular group is a polymer with a low critical solution temperature (LCST) in the range of 37°C to 42°C. The molecular group undergoes conformational contraction when the ambient temperature increases, thereby counteracting the slowdown in the hydrolysis rate of ester bonds when the ambient temperature increases.

[0011] Preferably, the chemical modification also covalently introduces functional nanoclusters, which are activated to generate at least one signal source selected from microbubbles that can be detected by ultrasound imaging equipment and structures that cause changes in acoustic impedance when the glycosidic bonds of the main chain break and the fiber matrix structure becomes loose.

[0012] Preferably, the chemical modification enables the modified alginate to form multivalent chelating functional groups on the surface and ends of fiber fragments when the main chain breaks. These functional groups can bind to metal ions or receptor sites on the cell surface.

[0013] Preferably, the prepared seaweed fiber, in a phosphate buffer solution at 37°C, meets the following two-stage degradation characteristics: during the first stage of stabilization, the tensile strength retention rate is not less than 80% of the initial value; during the subsequent second stage of rapid disintegration, the tensile strength decreases by more than 50% of the initial value; and the ratio of the average tensile strength loss rate during the second stage of rapid disintegration to the average tensile strength loss rate during the first stage of stabilization is not less than 50.

[0014] Preferably, chemical modification is achieved by a carbodiimide activator, with the catalytic functional group being hydroxyl or carboxyl; in the spinning extrusion step, the spinning solution is extruded into a coagulation bath containing calcium or barium ions.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention achieves programmed control of degradation time, making it precise and predictable. For example, existing fiber degradation technologies depend on external environments (such as ion concentration), and the process is random and uncontrollable. This invention introduces a chemical clock (i.e., rate-controllable side-chain hydrolysis groups) into the molecular chain, allowing fiber degradation to be precisely triggered by internal chemical reactions. This enables the fiber to remain stable up to a preset time point, such as 30 or 90 days, after which it rapidly disintegrates. This resolves the contradiction between long-term stability and rapid degradation inherent in existing technologies. Furthermore, since the initiation and process of degradation are determined by the internally preset molecular structure, rather than uncertain external environmental factors, the functional lifespan of the fiber of this invention exhibits extremely high reliability and consistency in complex practical applications, avoiding the risk of premature performance failure due to environmental changes.

[0016] 2. Addressing the technical problem of performance fluctuations in final products caused by uneven molecular weight of raw materials in industrial production, this invention introduces shear-sensitive weak covalent bonds and reducing agent microcapsules. This enables the preferential breakage of excessively long chains with uneven molecular weight at weak covalent bonds during high-shear spinning. The breakage products activate the reducing agent microcapsules, releasing the reducing agent, which then repairs the broken molecular chain ends, restoring spinnability. This process transforms raw material differences into a quality control step to improve product uniformity, effectively eliminating the impact of raw material batch fluctuations on the predictability of fiber's final degradation performance and improving product reliability.

[0017] 3. The method of this invention also includes introducing a functional nanocluster during the chemical modification step. This nanocluster possesses unique acoustic contrast characteristics: when the overall fiber structure remains intact, they are tightly encapsulated by a dense matrix and remain in a quiescent state; once the pre-programmed degradation is initiated, the fiber backbone breaks, the matrix rapidly becomes loose and forms a porous structure, and this physical change activates the nanoclusters, causing them to release signals detectable by conventional ultrasound imaging equipment. Through this design, the fiber's disintegration process after fulfilling its functional mission is no longer a hidden process difficult to monitor non-invasively, but rather transformed into a visible signal release process that occurs synchronously with the degradation stage. This provides a direct window for external observation to determine the integrity of the fiber structure, allowing its degradation dynamics in vivo to be tracked and evaluated in real time. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the temperature compensation mechanism of the seaweed fiber of the present invention; Figure 2 This is a curve comparing the tensile strength retention rate of the seaweed fiber of this invention with that of the control group fiber; Figure 3 This is a flowchart illustrating the preparation method and self-healing quality control mechanism of seaweed fiber according to the present invention. Figure 4 This is a schematic diagram of the two-stage programmed degradation mechanism of seaweed fiber in this invention; Figure 5 This is a scanning electron microscope image showing the intact microstructure of the fiber during the stable period of this invention. Figure 6 This is a scanning electron microscope image showing the microscopic changes on the fiber surface during the transition period of this invention. Figure 7 This is a scanning electron microscope image of the fiber structure disintegration during the rapid disintegration phase of this invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail 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.

[0020] This invention provides an alginate fiber and its preparation method, the overall process of which mainly consists of the following core stages: First, the sodium alginate macromolecular chain, used as the raw material, undergoes pre-defined chemical modification to introduce programmed self-degradation and process quality control functions into the molecular structure; second, the chemically modified alginate is formulated into a spinning solution, and a self-molecular mass screening and repair mechanism is established within this solution system during the spinning process; finally, the spinning solution is extruded in a coagulation bath containing divalent cations through a wet spinning process, and alginate fiber with a pre-defined lifespan is formed through ion crosslinking. In the preparation of man-made fibers, especially for functional medical fibers, the mechanical property stability within a specific time window and the final rapid disintegration and absorption capacity are key technical indicators determining the success or failure of their application. However, the degradation behavior of traditional alginate fibers is completely subject to the unpredictable ion exchange balance in their environment, resulting in a limited functional lifespan. The degradation process cannot be precisely defined. To address this technical problem, this method involves chemically modifying the sodium alginate macromolecular chain by introducing specific side-chain chemical groups through covalent bonds. These side-chain chemical groups contain an ester bond whose hydrolysis rate is determined by its own chemical structure. After the ester bond hydrolyzes, the side-chain chemical group releases a catalytic functional group, such as a hydroxyl or carboxyl group, that can catalyze the cleavage of the glycosidic bonds in the main chain. This chemical modification is achieved using a carbodiimide activator. In an aqueous reaction system, the carboxyl group on the sodium alginate molecular chain serves as the reaction site, undergoing a coupling reaction with a small alcohol or amine molecule containing a pre-defined ester bond and a protected catalytic functional group. This covalently integrates the side-chain chemical group into the sodium alginate main chain. Consequently, the fiber degradation behavior no longer depends on the external environment but is determined by a controllable internal chemical reaction endpoint, transforming the fiber degradation mode from a passive environmental response to structural disintegration driven by an internal chemical process.

[0021] To ensure the feasibility and stability of the aforementioned programmed degradation function, the introduction ratio of side-chain chemical groups was set at 1 to 5 per 100 alginate repeating units. This ratio range was determined based on systematic experimental calibration results of the technical trade-off between fiber spinnability and degradation efficiency. When the introduction ratio is below 1%, even if all side chains are hydrolyzed, the density of released catalytic functional groups is insufficient to effectively catalyze the breakage of a sufficient number of main-chain glycosidic bonds in a short time, resulting in an indistinct second-stage rapid disintegration period of the fiber and degradation behavior approaching the traditional slow process. Conversely, when the introduction ratio is above 5%, excessive... Excessive carboxyl groups occupy the fiber, weakening the ability of alginate molecular chains to ionically crosslink with divalent cations (such as calcium or barium ions) in the coagulation bath. This results in insufficient initial mechanical strength of the obtained fibers, and even the inability to form a continuous fiber morphology. Therefore, an introduction ratio of 1% to 5% ensures an efficient triggering window for programmed degradation without compromising the basic spinnability and mechanical properties of the fiber. Furthermore, to address the technical challenge of uneven molecular weight distribution between batches of sodium alginate raw materials in industrial production, this unevenness leads to differences in the mechanical properties and degradation rate of the final fiber product, weakening the fiber's mechanical strength. Its predictability stems from the introduction of shear-sensitive weak covalent bonds in the chemical modification step of this method, along with the dispersion of reducing agent microcapsules in the subsequently prepared spinning solution. These weak covalent bonds are generated through the reaction of functional groups on the alginate chain with aldehyde compounds, such as Schiff bases or hemiacetal amine bonds formed by the reaction of amino or hydroxyl groups with dialdehyde or acetal. The bond energy is designed to be just below the shear stress threshold applied by the spinneret during spinning extrusion. The reducing agent microcapsules consist of an inert coating encapsulating at least one reducing agent selected from thiols and ascorbic acid. This coating is stable to the spinning solution system but can be broken by the weak covalent bonds. The aldehyde or ketone compounds generated later are destroyed; in the spinning extrusion process, which experiences high shear stress, long chains or entangled segments with molecular weights exceeding the average range in the spinning solution will preferentially break at weak covalent bonds. The breakage products then activate the surrounding reducing agent microcapsules, causing them to release the reducing agent. The reducing agent chemically repairs the ends of the broken molecular chains, for example, reducing the newly formed aldehyde groups to hydroxyl groups, restoring their ability to participate in ionic crosslinking. Through this screening-melting-repair mechanism that is automatically completed during the spinning process, the impact of raw material inhomogeneity is transformed into a quality control step that improves the uniformity of the final product.

[0022] Furthermore, considering the temperature fluctuations that fibers may experience in certain applications, such as localized heating caused by inflammatory responses, which can accelerate ester bond hydrolysis and cause the actual degradation time of the fiber to deviate from the preset value, the chemical modification step of this method can selectively covalently introduce molecular groups with temperature-sensitive conformational changes. These molecular groups, such as oligomers of poly(N-isopropylacrylamide), are designed to have a low critical solution temperature (LCST) slightly higher than normal physiological temperatures (e.g., 37°C). At normal temperatures, these groups exhibit an extended conformation and have no significant effect on the hydrolysis reaction of adjacent ester bonds. When the ambient temperature rises and exceeds its LCST, these molecular groups undergo conformational contraction, transforming into a collapsed spherical structure. This conformational physical change directly increases the steric hindrance around the ester bond hydrolysis sites, thereby kinetically slowing down the hydrolysis rate of the ester bonds. This slowing effect counteracts the accelerating hydrolysis caused by temperature increases, thus improving fiber degradation. Temperature compensation is applied to the de-clock to ensure the accuracy of its functional lifespan within a certain temperature fluctuation range. To achieve non-invasive monitoring of the fiber degradation process, functional nanoclusters can be covalently introduced during the chemical modification step. These functional nanoclusters, such as encapsulated gas precursor nanoparticles, remain chemically stable and do not generate detectable signals when the fiber structure is intact, as they are encapsulated by a dense matrix network. When the preset programmed degradation is initiated, the breakage of numerous glycosidic bonds in the main chain causes the fiber matrix structure to rapidly become loose and porous within a short period of time. This structural physical change allows surrounding bodily fluids to penetrate and react with the gas precursors, activating them to generate at least one signal source selected from microbubbles that can be detected by ultrasound imaging equipment and structures that cause changes in acoustic impedance. Thus, the fiber's structural disintegration process is no longer an invisible event, but rather provides a window for external observation to judge its structural integrity through the release of a physical signal synchronized with the degradation stage.

[0023] After the fiber completes its functional mission and disintegrates, to accelerate its clearance in the application environment, the chemical modification scheme of this method is further configured to form multivalent chelating functional groups on the surface and ends of fiber fragments when the modified alginate breaks down along the main chain. This is achieved by introducing specific molecular groups during modification. These groups have their chelating ability shielded when the main chain is intact, but once the main chain breaks, they are exposed and activated as new chain ends. These functional groups can bind with high affinity to metal ions or receptor sites on the cell surface, thereby guiding phagocytes and other cells to recognize and clear the fiber, transforming the terminal clearance process of the fiber from a passive metabolism to an active one. The seaweed fiber prepared by the aforementioned method exhibits specific two-stage degradation characteristics in a phosphate buffer solution at 37°C: during the first stable phase, the tensile strength retention rate is not less than 80% of the initial value; during the subsequent second rapid disintegration phase, the tensile strength decreases by more than 50% of the initial value; and the ratio of the average tensile strength loss rate during the second rapid disintegration phase to the average tensile strength loss rate during the first stable phase is not less than 50. This combination of technical features constructs a novel seaweed fiber and its preparation method with highly controllable degradation behavior, highly uniform product performance, and monitorable process status.

[0024] Example 1: In an in vivo implantation application requiring long-term mechanical support followed by rapid, residue-free degradation, such as absorbable tendon fixation sutures, the technical challenge lies in ensuring that the tensile strength of the suture material does not decrease during the 6-8 week tendon healing period, while simultaneously enabling the material to rapidly disintegrate after this period to avoid long-term foreign body reactions or affecting tissue remodeling. The linear or logarithmic degradation curves of conventional biodegradable materials often fail to simultaneously meet these two performance requirements. To address this scenario, the method of this invention is used to prepare an alginate fiber suture. This is achieved by selecting ester bonds with specific steric hindrance structures as side chain chemical groups in a chemical modification step, followed by hydrolysis. The half-life is set at 7 weeks, or 49 days. Meanwhile, the shear-sensitive weak covalent bonds introduced in the chemical modification step, together with the reducing agent microcapsules dispersed in the spinning solution, constitute a quality control mechanism that operates in the fiber manufacturing process. During the spinning extrusion process, the uneven chain segments in the raw material preferentially break at the weak covalent bonds due to shear stress. The fracture products then activate the reducing agent microcapsules, repairing the broken molecular chain ends. The role of this series of steps is to ensure that the polymer chains entering the coagulation bath have a similar molecular weight distribution, thereby ensuring the consistency of the programmed degradation clock start and rate within all fibers, and establishing a premise for the predictability of the final degradation behavior.

[0025] When this suture is applied to fix the tendon, the mechanical integrity of the fiber is maintained by its internal stable ionic cross-linking network during the first 6 weeks of its functional life, and the tensile strength remains above 80% of its initial value, providing reliable fixation for tissue healing. At the same time, the side chain ester bonds, which are unaffected by fluctuations in the concentration and pH of the surrounding body fluid ions, begin to hydrolyze at a uniform rate as an internal chemical clock. When a local inflammatory response occurs after surgery, causing the temperature of the implantation area to rise from 37°C to 38.5°C, the molecular groups with thermosensitive conformational changes covalently grafted onto the molecular chain undergo conformational contraction, increasing the steric hindrance around the ester bonds, thereby slowing down the hydrolysis rate. This slowing effect counteracts the hydrolysis acceleration caused by the temperature rise, so that the timing accuracy of the degradation clock is not affected by the pathological temperature fluctuation. By week 7, most ester bonds had been hydrolyzed. A large number of activated catalytic functional groups, utilizing the ortho-catalytic effect, triggered multi-point synchronous breakage of the main chain glycosidic bonds in a short period of time. The mechanical properties of the fiber rapidly declined within a few days, with a strength loss of more than 50%, transforming it from a stable load-bearing structure into absorbable small molecular fragments. Ultimately, the tendon tissue healed after receiving sufficient and stable mechanical support, while the suture material disintegrated spontaneously after a predetermined time point, avoiding the risk of chronic inflammation that might occur with long-term implants. This process no longer relies on regulating the interaction between the material and the external environment to control the degradation rate, but rather resolves the contradiction between long-term performance stability and eventual rapid disintegration within a single material system through an internal chemical reaction sequence determined by the molecular structure.

[0026] Example 2: To quantitatively verify the effectiveness of the preparation method of the present invention in imparting two-stage degradation characteristics to seaweed fibers, namely, maintaining stable mechanical properties within a preset time window and then undergoing rapid structural disintegration, the following comparative experiment was conducted; two sample groups were set up in the experiment. The control group used unmodified sodium alginate to prepare seaweed fibers through a conventional wet spinning process; the sample group of the present invention used the above method to prepare seaweed fibers, in which the introduction ratio of side chain chemical groups in the chemical modification step was set to 3 per 100 alginate repeating units, and the process was further modified by selecting the corresponding ester bond chemical structure. The initiation time for sequential degradation was set at 30 days. All fiber samples were prepared under the same spinning and post-treatment conditions to ensure consistency in initial diameter and mechanical properties. The test environment was set to simulate a body fluid environment, that is, the two groups of fiber samples were placed in phosphate buffer solution (PBS) with a pH of 7.4 and aged in a constant temperature water bath at 37°C. The mechanical properties were characterized by a tensile strength tester with a mechanical sensor range of 5N and a data acquisition resolution of 0.001N. During the test, the tensile rate was set to 10mm / min.

[0027] After the experiment began, fiber samples were taken from the solutions of the two sample groups at preset time points for tensile strength testing, and their retention rate relative to the initial strength was calculated. Comparing the strength retention rates of the two groups over time revealed two distinctly different decay trends. The strength retention rate of the control group samples showed a continuous, gradual decline throughout the 35-day test period, decreasing to 65.2% on day 28 and further to 53.6% on day 35. In contrast, the sample group of this invention exhibited high stability in the early stages of the test, maintaining a strength retention rate of 89.1% on day 28. However, between day 28 and day 32, its mechanical properties underwent a sharp change, with the strength retention rate rapidly dropping from 89.1% to 35% within four days. The degradation rate was 0.2% on day 35 and decreased to 18.9% on day 35. The difference shown in the experimental data corresponds to the degradation mechanism of the two fibers. The gradual decay of the control group is an external feature of its structure relying on passive ion exchange for degradation. The curve of initial stability followed by a sudden drop in the sample group of this invention is a manifestation of its internal programmed degradation mechanism. During the stable period of the first 28 days, the mechanical properties of the fiber are guaranteed by the ion cross-linking network, while the internal side chain ester bonds act as a chemical clock for slow hydrolysis. When the hydrolysis reaction is completed at around day 30, the released catalytic functional groups cause the main chain to break rapidly, resulting in the disintegration of the fiber's macroscopic structure. The experimental results show that the preparation method of this invention can achieve programmed control of its functional life by setting a timing and execution mechanism determined by molecular reactions in the chemical structure of the fiber.

[0028] To further verify the signal release and terminal clearance characteristics of fibers during the structural disintegration stage, two follow-up tests were conducted on the samples of the present invention on day 35, i.e., fiber fragments that had undergone structural disintegration. The first test was in vitro ultrasound observation, in which a phosphate buffer solution containing fiber fragments was placed in a water tank of an ultrasound imaging device. The results showed that obvious microbubble signals could be observed around the fiber fragments, and its acoustic imaging effect was comparable to that of commercially available microbubble contrast agents with matching concentrations. This phenomenon confirmed that after the main chain broke, resulting in a loose matrix structure, the pre-placed functional nanoclusters were successfully activated and released detectable acoustic signals. The second test was an in vitro cell phagocytosis experiment, in which macrophages were co-cultured with fiber fragments and observed at different time points using microscopic imaging technology. The results showed that the surface of the fiber fragments in the present invention exhibited significant chemotaxis and adsorption to macrophages, and the rate of phagocytosis by cells was 5 to 7 times that of the control group fiber fragments that had also disintegrated. This result indicates that the multivalent chelating functional groups exposed when the main chain breaks can effectively guide phagocytes to rapidly clear fiber residues.

[0029] Example 3: This example combines Figures 1 to 7A description of a type of seaweed fiber and its preparation method is provided, such as... Figure 1 As shown, under normal physiological conditions, the body temperature is 37°C. At this temperature, the covalently grafted thermosensitive conformational group maintains an extended conformation, which does not create steric hindrance to the adjacent side-chain ester bonds, allowing the ester bonds to hydrolyze at a normal rate, thus driving the degradation clock to keep accurate time. When the physiological environment is heated due to inflammation, for example, when the temperature rises to 38.5°C, the increased temperature will have an effect that accelerates the hydrolysis of ester bonds. However, it will also be transmitted to the thermosensitive conformational group, triggering a conformational change, which shrinks into a spherical structure. This conformational change increases the steric hindrance around the ester bonds, thus producing a hydrolysis slowing effect. This hydrolysis acceleration effect and the hydrolysis slowing effect counteract each other, and the final result is that the timing accuracy of the degradation clock is maintained, so that the programmed degradation time of the fiber is not affected by the fluctuation of the ambient temperature.

[0030] like Figure 2 As shown in the figure, a set of comparative experimental data intuitively demonstrates the two-stage programmed degradation characteristics of the seaweed fiber of the present invention. The horizontal axis of the figure represents time in days, and the vertical axis represents the tensile strength retention rate in %; the dashed line representing the control group (unmodified) shows that its tensile strength retention rate shows a continuous and gradual decrease throughout the test period. In contrast, the solid line representing the sample group of the present invention (programmed degradation) shows that its tensile strength remains at a high level close to the initial value for 28 days in the early stage of the test, showing high stability. However, after the preset time point, its strength drops sharply and disintegrates rapidly within a few days, showing the characteristics of first stabilizing and then suddenly dropping. This confirms the effectiveness of the internal programmed degradation mechanism.

[0031] like Figure 3 As shown, this invention reveals the overall preparation process of seaweed fiber and its embedded self-healing quality control mechanism. The process begins with the sodium alginate macromolecular chain as the raw material, which is first chemically modified to introduce programmed self-degradation and self-healing quality control functions. Then, the modified product is formulated into a spinning solution, in which reducing agent microcapsules are uniformly dispersed. In the wet spinning extrusion stage, the shear stress on the spinning solution triggers the quality control mechanism, that is, the uneven chain segments in the raw material break under high shear force. The broken products then activate the surrounding reducing agent microcapsules, releasing the reducing agent to repair the broken molecular chain ends. The solution that has passed through this self-healing stage is finally extruded into a coagulation bath containing divalent cations, and seaweed fiber, the final product with programmed degradation capability, is formed through ionic cross-linking.

[0032] like Figure 4As shown, during the first stage of stabilization, the complete ionic cross-linking network ensures the mechanical properties of the fiber, with the tensile strength retention rate not less than 80%. At this time, the protected catalytic functional groups are in an inactive state, while the ester bonds of the side chains act as an internal clock for slow hydrolysis. After entering the transition period, the ester bonds are hydrolyzed, the shielded catalytic functional groups are activated and released, and then multi-point breakage of the main chain is triggered in a short time, causing the fiber to enter the second stage of rapid disintegration. At this time, the fiber matrix is ​​completely disintegrated, and the tensile strength drops rapidly to below 50%.

[0033] Example 4: This example provides a standardized engineering calibration procedure for determining the specific chemical modification parameters of the seaweed fiber of the present invention, so as to achieve precise setting of the programmed degradation cycle and modification ratio of the fiber. In the engineering practice of fiber preparation, it is necessary to develop products with different functional lifespans for different application scenarios. One type of fiber used for epidermal suturing requires a functional lifespan of 21 days, while another type of fiber used for tendon repair requires a mechanical property stabilization period of up to 90 days. Therefore, it is necessary to establish a method to meet the two different technical requirements by parameterizing and controlling a single raw material system. To achieve the setting of the fiber degradation cycle, a hydrolysis kinetics database of side chain chemical groups is first established. The initial state of this procedure is to select sodium alginate raw material of the same specifications as above and prepare a set of candidate alcohol small molecules for subsequent coupling. These small molecules have the same protected catalytic functional groups, but the chemical structure of their ester bond formation sites has a systematic gradient change. The structural adjustment method includes changing the branching degree of the alkyl chain to adjust the structure. The procedure involves steric hindrance and the introduction of different functional groups onto the aromatic ring to modulate electronic effects. The steps are as follows: each candidate alcohol molecule is covalently coupled to the sodium alginate macromolecular chain under the same reaction conditions at a fixed ratio of 2 per 100 alginate repeating units to prepare a series of modified alginate samples. Subsequently, fibers made from these samples are subjected to accelerated aging tests in a phosphate buffer solution at 37°C and pH 7.4 (Example 2). The concentration of small-molecule alcohols released due to ester bond hydrolysis is monitored at different time points using high-performance liquid chromatography (HPLC). This allows for the plotting of hydrolysis kinetic curves for each side-chain chemical group structure and the determination of its hydrolysis half-life. This experimental database establishes a correspondence between the molecular structure of the side-chain chemical group and its degradation half-life under simulated body fluid conditions. When a fiber with a specific lifespan is required, the corresponding chemical structure can be directly selected from this database for modification, transforming the selection of the degradation cycle into a data-supported engineering operation.

[0034] After determining the side-chain chemical group structure that meets the 90-day lifespan requirement, the introduction ratio was further optimized to maximize the initial mechanical properties of the fiber while ensuring degradation reliability. This procedure employed a gradient experimental method, using the selected side-chain chemical group structure to chemically modify sodium alginate at five gradients: 1.0%, 2.0%, 3.0%, 4.0%, and 5.0%, preparing five groups of fiber samples with different modification ratios. Subsequently, two key performance indicators were tested on these five groups of samples: initial dry tensile strength and the time point at which the strength decreased to below 50% of its initial value when placed in a simulated body fluid environment. The test results... The results show that as the introduction ratio increases, the time point at which the fiber strength drops sharply gets closer to the set 90 days, but its initial tensile strength shows a downward trend. When the introduction ratio is 1.0%, the initial strength of the fiber is the highest, but its degradation start time is delayed to about 115 days. When the introduction ratio is 5.0%, the degradation start time is closest to 90 days, but its initial strength has decreased by about 18%. Through a trade-off analysis of the two sets of performance data, 3.5% was finally determined as the introduction ratio for the 90-day lifespan tendon repair fiber. At this ratio, the initial strength loss of the fiber is less than 10%, and the deviation between its actual degradation start time and the set value is within 5%.

[0035] Example 5: This example provides a process parameter calibration procedure designed to ensure the stable operation of a self-healing quality control mechanism in continuous production. Its core lies in establishing a matching relationship between the shear stress during spinning and the introduced threshold for the breaking of weak covalent bonds sensitive to shear force. In the industrial wet spinning process of seaweed fiber, the shear stress experienced by the spinning solution as it passes through the spinneret is affected by factors such as the solution viscosity, extrusion rate, and spinneret geometry. To ensure that this shear stress can induce selective breaking of weak covalent bonds on molecularly uneven segments while avoiding damage to the alginate backbone, the following pre-calibration procedure must be performed before production. First, a rotational rheometer is used to calibrate the spinning solution containing weak covalent bonds and reduced... Shear scan tests were conducted on specific batches of spinning dope containing the microcapsules. By monitoring the abrupt change in viscosity during the increase of shear rate, the target shear stress threshold τ_target that would trigger the breakage of weak covalent bonds was determined. Secondly, based on the hydrodynamic model of the spinning equipment, i.e. the functional relationship between the shear stress τ_spin at the spinneret and the viscosity η of the spinning dope, the volumetric extrusion rate Q, and the spinneret radius R, the actual shear stress τ_spin was calibrated within a working range around the target threshold by adjusting the controllable variable, the volumetric extrusion rate Q. The upper and lower limits of this working range were determined based on the minimum stress value that ensures the effective breakage of non-uniform chain segments and the maximum stress limit that avoids damage to the main chain, respectively.

[0036] To verify the effectiveness of the above calibration procedure, experimental spinning was conducted on two groups of spinning solutions using the calibrated volumetric extrusion rate. The first group of solutions contained modified alginate with a known non-uniform molecular weight distribution, while the second group contained modified alginate with a highly uniform molecular weight distribution as a control. The molecular weight distribution of the fiber samples obtained from the two experiments was detected by gel permeation chromatography (GPC). The results showed that despite the differences in the initial raw materials, the final molecular weight distribution curves of the two groups of fiber samples basically overlapped, and both exhibited a single narrow peak. This result indicates that the established process parameter calibration procedure can accurately activate the self-healing quality control mechanism during the production process, thereby eliminating the impact of raw material batch fluctuations on the uniformity of the final product and providing a uniform material basis for the predictability of the final degradation performance of the fiber.

[0037] Example 6: This example provides a standardized procedure aimed at establishing a correlation model between the chemical properties of sodium alginate raw materials and core process parameters, in order to eliminate the impact of batch-to-batch differences in raw materials on the performance of the final fiber product. In the continuous production of fibers, in order to ensure that different batches of sodium alginate raw materials can produce fiber products with consistent performance indicators, it is necessary to establish a process parameter matrix between the key chemical properties of the raw materials and the optimal ion concentration in the coagulation bath in advance. The establishment process of this procedure is as follows: First, select multiple batches of sodium alginate raw materials with gradient differences in M / G ratios, and quantitatively characterize their M / G ratios by nuclear magnetic resonance spectroscopy. Subsequently, each batch of raw materials is prepared into spinning solutions with the same chemical modification parameters according to the above procedure.

[0038] For each M / G ratio spinning solution, an independent optimization experiment was conducted to determine the ion concentration in the coagulation bath. The experiment aimed to obtain fibers that balance tensile strength and network stability. The spinning solution was extruded through a fixed spinning assembly into a series of coagulation baths with calcium chloride concentrations increasing in 0.5% increments. Fiber samples formed in each concentration coagulation bath were tested for initial dry tensile strength and equilibrium swelling rate. Analysis of the experimental data determined an optimal calcium chloride concentration for each M / G ratio, which ensures that the resulting fibers possess sufficient tensile strength while maintaining optimal equilibrium swelling rate. The expansion rate is within a preset range that characterizes the stability of the network structure. By fitting the M / G ratio of all batches of raw materials and their corresponding optimal calcium chloride concentration data points, a process parameter matrix that can guide production can be obtained. In subsequent routine production, when a new batch of raw materials is added, it is only necessary to first determine its M / G ratio, and then the optimal coagulation bath concentration that matches it can be directly found or calculated through this parameter matrix, thus saving a lot of repetitive experiments. This procedure transforms the original process adjustment that relied on trial and error into a standardized pre-setting process based on a data model, ensuring the batch-to-batch stability of fiber product performance.

[0039] Example 7: To prepare a seaweed fiber with a target stability of 28-30 days, sodium alginate with an M / G ratio of 1.2 was selected as the raw material. The chemical modification steps were as follows: 10 g of sodium alginate was dissolved in 500 mL of pure water. Under nitrogen protection and stirring, an ester formed by 2-(2-hydroxyethoxy)ethanol and glycine protected by tert-butyloxycarbonyl (Boc) was added, making the molar ratio of 2-(2-hydroxyethoxy)ethanol to the carboxyl group on sodium alginate 0.1:1. 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC-HCl) and N-hydroxythiosuccinimide (Sulfo-NHS) were added as catalysts, and the reaction was carried out at room temperature for 24 hours. After the reaction, unreacted small molecules were removed by dialysis, and the product was obtained by freeze-drying. The introduction ratio of side chain chemical groups was confirmed by 1H NMR spectroscopy to be 3.8 per 100 alginate repeating units. This side chain ester bond was stable under simulated body fluid conditions (37°C, pH 7.4). The hydrolysis half-life of PBS buffer solution was determined to be 29.5 days by high performance liquid chromatography. The preparation of the spinning solution involved preparing a 6% (w / v) aqueous solution of the modified sodium alginate, adding reducing agent microcapsules made of polycaprolactone (PCL) as the wall material and ascorbic acid as the core material, at a dosage of 0.8% of the dry weight of sodium alginate; simultaneously, glutaraldehyde was added as a weak covalent bond forming agent, with a molar ratio of glutaraldehyde to the remaining usable hydroxyl groups on sodium alginate of 0.05:1. After stirring evenly, the solution was allowed to stand to remove bubbles. The wet spinning process involved extruding the spinning solution through a 0.1 mm orifice into a 2.5% (w / v) calcium chloride aqueous solution coagulation bath at a rate of 15 mL / h. The coagulation bath temperature was maintained at 20°C. After the fiber traveled 1 meter in the coagulation bath, it was stretched, washed, and dried. The mechanical property decay curve of the obtained fiber in PBS buffer solution at 37°C was compared with... Figure 2 The curves of the sample group of the present invention are highly consistent, with an intensity retention rate of 88% on day 28 and a rapid decrease to 34% on day 32.

[0040] 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 present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing seaweed fiber, characterized in that, The method includes: The carboxyl group on the sodium alginate macromolecular chain is chemically modified to introduce side chain chemical groups by covalent bonds. The side chain chemical groups contain an ester bond whose hydrolysis rate is determined by its chemical structure. After the ester bond is hydrolyzed, the side chain chemical groups release catalytic functional groups that can catalyze the breaking of the glycosidic bond in the main chain. In the chemical modification, a shear-sensitive weak covalent bond is also introduced, which is generated by the reaction of functional groups on the sodium alginate macromolecular chain with aldehyde compounds; wherein, the shear-sensitive weak covalent bond is generated by the reaction of the amino or hydroxyl groups on the alginate chain with dialdehyde or acetal; the reducing agent microcapsules are microcapsules encapsulated by an inert coating and contain at least one reducing agent selected from thiols and ascorbic acid. Chemically modified alginate was formulated into a spinning solution, and reducing agent microcapsules were dispersed in the spinning solution. The reducing agent microcapsules could be activated by the products of weak covalent bond breaking. In the spinning extrusion step, shear stress is used to break the weak covalent bonds on the molecular chains with uneven molecular weight in the spinning solution. The broken products activate the reducing agent microcapsules to release the reducing agent, which repairs the broken molecular chain ends. The spinning solution is extruded into a coagulation bath containing divalent cations, and seaweed fibers are formed through ionic cross-linking.

2. The method for preparing seaweed fiber according to claim 1, characterized in that, In chemical modification, the proportion of side chain chemical groups introduced is 1 to 5 per 100 alginate repeating units.

3. The method for preparing seaweed fiber according to claim 1, characterized in that, In the chemical modification, a molecular group with thermosensitive conformational change is also introduced. The molecular group is a polymer with a low critical solution temperature (LCST) in the range of 37°C to 42°C. The molecular group undergoes conformational contraction when the ambient temperature increases, so that the slowdown in the hydrolysis rate of ester bonds at the increase in ambient temperature counteracts the hydrolysis acceleration effect caused by the increase in temperature.

4. The method for preparing seaweed fiber according to claim 1, characterized in that, In the chemical modification, functional nanoclusters are also covalently introduced. When the glycosidic bonds of the main chain break and the fiber matrix structure becomes loose, the functional nanoclusters are activated to generate at least one signal source selected from microbubbles that can be detected by ultrasound imaging equipment and structures that cause changes in acoustic impedance.

5. The method for preparing seaweed fiber according to claim 1, characterized in that, Chemical modification enables the modified alginate to form functional groups with multivalent chelating capabilities on the surface and ends of fiber fragments when the main chain breaks.

6. The method for preparing seaweed fiber according to claim 1, characterized in that, The obtained seaweed fiber, in a phosphate buffer solution at 37°C, meets the following two-stage degradation characteristics: during the first stage of the stabilization period, the tensile strength retention rate is not less than 80% of the initial value; during the subsequent second stage of the rapid disintegration period, the tensile strength decreases by more than 50% of the initial value; and the ratio of the average tensile strength loss rate during the second stage of the rapid disintegration period to the average tensile strength loss rate during the first stage of the stabilization period is not less than 50.

7. The method for preparing seaweed fiber according to claim 1, characterized in that, Chemical modification is achieved through carbodiimide activators, with hydroxyl or carboxyl functional groups as the catalytic functional groups; in the spinning extrusion step, the spinning solution is extruded into a coagulation bath containing calcium or barium ions.

8. A type of seaweed fiber, characterized in that, The seaweed fiber is prepared by any one of the preparation methods according to claims 1 to 7.

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