A photoresponsive hydrogel composite material and its application in the treatment of pulpitis

Abstract

This invention discloses a photoresponsive hydrogel composite material and its application in the treatment of pulpitis. The material, named GelMA-MOF@Cr-Al, is composed of metal-organic framework (MOF)@Cr-Al nanoparticles and GelMA hydrogel, and possesses the following functions: 1) rapid cross-linking and molding under ultraviolet light, enabling precise clinical operation; 2) scavenging reactive oxygen species and regulating inflammatory signaling pathways; and 3) promoting odontoblast differentiation. Experiments show that GelMA-MOF@Cr-Al can significantly inhibit pulpitis, enhance dentin regeneration, and exhibit excellent antibacterial properties and biocompatibility. This material overcomes the limitations of traditional inorganic trioxide polymers (MTA) pulp capping materials, providing a dual anti-inflammatory and regenerative strategy for pulp vitality treatment.

Description

Technical Field

[0001] This invention relates to the field of oral biomedical materials technology, specifically to a light-responsive hydrogel composite material that can be used for the treatment of pulpitis. Background Technology

[0002] Dental pulp is a complex biological tissue composed of various cell types and extracellular matrix, playing a vital role in maintaining tooth physiological function, including nutrient transport, removal of metabolic waste, and tissue repair mechanisms. In young permanent teeth, pulp vitality is crucial for tooth development and long-term health maintenance. The success of pulp revitalization therapy (VPT) fundamentally depends on activating the regenerative potential of stem cells within the inflamed dental pulp to promote tissue repair and maintain tooth vitality. However, the clinical efficacy of VPT remains limited by several factors, including accurate assessment of the inflammatory state, level of bacterial contamination, stage of tooth development, and, critically, the selection of the pulp covering material.

[0003] Calcium hydroxide-based materials are considered the historical gold standard for pulp covering, exhibiting superior antibacterial properties and the capacity to promote mineralization. However, their clinical limitations are well-known: rapid dissolution leading to compromised long-term sealing performance, cytotoxicity caused by extreme alkalinity (pH 12–13), and the susceptibility to microleakage in the resulting porous dentin bridges. While mineral trioxide polymers (MTA) and calcium silicate-based materials demonstrate better biocompatibility and sealing capabilities compared to calcium hydroxide, they still face challenges, including prolonged setting times, tooth discoloration, and incomplete resolution of inflammatory responses. Notably, neither of these materials reliably induces odontoblast-like cell differentiation, raising concerns about the truly regenerative nature of the resulting hard tissue barrier. These limitations underscore the urgent need to develop innovative pulp covering materials that simultaneously achieve both inflammation modulation and tissue regeneration.

[0004] The inflammatory microenvironment in infected dental pulp presents a paradoxical picture. Moderate inflammation helps clear bacteria through neutrophil recruitment and cytokine signaling, while excessive inflammation triggered by overactivation of reactive oxygen species (ROS) initiates a pathological cascade via the NF-κB / MAPK pathway. This oxidative stress disrupts cellular homeostasis by impairing the expression of adhesion molecules (e.g., integrins), cell cycle progression, and the differentiation capacity of dental pulp stem cells (DPSCs). Furthermore, ROS and proteases produced by neutrophils cause collateral damage to surrounding tissues while fighting pathogens, creating a vicious cycle that hinders reparative dentin formation.

[0005] Emerging nanotechnology approaches offer promising solutions to this therapeutic dilemma. Metal-organic frameworks (MOFs), crystalline porous materials constructed from metal nodes and organic ligands, have emerged as multifunctional platforms in biomedical applications. Their unique advantages include: 1) intrinsic enzyme-mimicking activity (catalase) for scavenging reactive oxygen species; 2) controlled metal ion release for sustained antibacterial effects; and 3) the ability to be internalized within cells, bypassing transmembrane transport limitations. These properties make MOFs ideal candidates for developing multifunctional pulp covering materials that can simultaneously address infection control, inflammation resolution, and tissue regeneration. Summary of the Invention

[0006] In view of the above-mentioned problems in the prior art, the purpose of this invention is to provide a light-responsive hydrogel composite material for the treatment of pulpitis, which can effectively remove ROS, eliminate inflammation, promote dentin formation, and facilitate clinical operation.

[0007] To achieve the above objectives, the present invention provides a photoresponsive hydrogel composite material (GelMA-MOF@Cr-Al), which uses metal ions Cr... 3 The functional core of the metal-organic framework material MOF@Cr-Al, which is formed by the self-assembly of Al3+ and organic ligands, and the bioactive matrix of methacrylamide gelatin (GelMA) hydrogel, can be used as a drug for treating pulpitis. MOF@Cr-Al is a nanoparticle that is uniformly distributed in the GelMA hydrogel. The amount of MOF@Cr-Al added is 2.5% to 5% of the mass of GelMA hydrogel. The GelMA hydrogel also contains a photoinitiator, which initiates cross-linking and curing of the GelMA hydrogel under light irradiation.

[0008] Further, the organic ligand in the MOF@Cr-Al is preferably 2-methylimidazole, benzimidazole, 5-aminotetrazole, etc. In some embodiments of the present invention, 2-methylimidazole, aluminum nitrate, and chromium chloride hexahydrate are used to synthesize MOF@Cr-Al nanoparticles via a hydrothermal reaction. The MOF@Cr-Al nanoparticles have a particle size of 50-100 nm, a cuboid morphology, and Cr... 3 + and Al3+ are uniformly distributed in the material, Cr 3 The preferred molar ratio of Al+ to Al3+ is 1:1 to 3:1.

[0009] Furthermore, the photoinitiator is LAP (Lithium Phenyl-2,4,6-trimethylbenzoylphosphinate).

[0010] This invention also provides a method for preparing the above-mentioned photoresponsive hydrogel composite material GelMA-MOF@Cr-Al, comprising the following steps:

[0011] 1) Synthesize MOF@Cr-Al nanoparticles and disperse them in a buffer solution;

[0012] 2) Prepare a GelMA aqueous solution and add a photoinitiator;

[0013] 3) Add MOF@Cr-Al nanoparticles to GelMA solution in a certain proportion, mix evenly, and then crosslink under light and solidify.

[0014] In step 1) above, preferably, MOF@Cr-Al nanoparticles are synthesized by a solvothermal reaction of 2-methylimidazole, aluminum nitrate and chromium chloride hexahydrate, the precipitate is collected by centrifugation, washed and dispersed in phosphate buffer (PBS).

[0015] If the photoinitiator used in step 2) above is LAP, then crosslinking is performed using 405nm light in step 3).

[0016] In some embodiments of the present invention, step 2) involves adding 5% to 10% GelMA and 0.25% LAP photoinitiator to water and heating to 60 to 70°C to form a homogeneous solution.

[0017] The photoresponsive hydrogel composite material GelMA-MOF@Cr-Al of the present invention can be used to prepare therapeutic agents for pulpitis, including acute and chronic pulpitis caused by bacterial infection, trauma, or chemical stimulation. GelMA-MOF@Cr-Al achieves pulpitis treatment through the following methods:

[0018] 1. Rapid light curing: Crosslinking can be achieved after 15 seconds of 405nm light irradiation, meeting the needs of clinical operation;

[0019] 2. ROS scavenging: MOF@Cr-Al has catalase-like activity and can downregulate inflammatory factors such as IL-1β, IL-6, and TNF-α;

[0020] 3. Antibacterial properties: Releases Cr 3 + and Al3+ ions disrupt the bacterial cell membrane structure and inhibit the proliferation of Escherichia coli and Porphyromonas gingivalis;

[0021] 4. Promoting regeneration function: By regulating the TGF-β signaling pathway, it upregulates the expression of ALP, OCN, RUNX2 and DSPP, thereby promoting odontoblast differentiation.

[0022] This invention integrates metal-organic framework (MOF)@Cr-Al nanoparticles with GelMA hydrogel. The resulting photoresponsive hydrogel composite material, GelMA-MOF@Cr-Al, can rapidly cross-link and solidify under light irradiation, enabling precise clinical manipulation. It effectively scavenges reactive oxygen species (ROS), modulates the NF-κB / MAPK inflammatory signaling pathway, and promotes odontoblastic differentiation of dental pulp stem cells (DPSCs). Experiments show that GelMA-MOF@Cr-Al significantly reduces inflammatory infiltration and restores the odontoblast layer structure in a rat pulpitis model, without significant cytotoxicity, exhibiting excellent antibacterial properties and biocompatibility. This multi-faceted therapeutic strategy overcomes the limitations of traditional calcium hydroxide and MTA materials, providing an anti-inflammatory and regenerative strategy for pulp vitality therapy. It marks a paradigm shift from traditional passive debridement methods to active tissue reprogramming, and is expected to redefine the clinical standards for pulp vitality therapy. Attached Figure Description

[0023] Figure 1 A schematic diagram of the preparation of the photoresponsive hydrogel composite material GelMA-MOF@Cr-Al in Example 1 of this invention.

[0024] Figure 2 Bright-field images of the solution state and the solid state formed by ultraviolet light crosslinking of the photoresponsive hydrogel composite material GelMA-MOF@Cr-Al prepared in Example 1.

[0025] Figure 3 Transmission electron microscopy images of MOF@Al, MOF@Cr, and MOF@Cr-Al prepared in Example 1.

[0026] Figure 4 Scanning electron microscope images of MOF@Al, MOF@Cr, and MOF@Cr-Al prepared in Example 1.

[0027] Figure 5 In Example 1, morphological analysis was performed using scanning electron microscopy, and the elemental composition of the photoresponsive hydrogel composites GelMA-MOF@Cr-Al, GelMA-MOF@Cr, and GelMA-MOF@Al was analyzed using energy-dispersive X-ray spectroscopy.

[0028] Figure 6 The results of elemental analysis of MOF@Cr-Al using X-ray photoelectron spectroscopy (XPS) in Example 1.

[0029] Figure 7 In Example 1, GelMA-MOF@Cr, GelMA-MOF@Al, and GelMA-MOF@Cr-Al released metal ions Cr. 3 + Experimental results.

[0030] Figure 8 Experimental results of GelMA-MOF@Cr, GelMA-MOF@Al and GelMA-MOF@Cr-Al releasing metal ions Al3+ in Example 1.

[0031] Figure 9 The cytotoxicity test results of different concentrations of MOF@Cr-Al in Example 2 after incubation with dental pulp stem cells for different times (1 day, 3 days, 5 days and 7 days).

[0032] Figure 10 In Example 3, iDPSCs treated with MOF@Al, MOF@Cr, and MOF@Cr-Al for 3 hours were analyzed by RT-qPCR to detect the expression levels of mRNA of the inflammatory cytokine interleukin-6 (IL-6) and tumor necrosis factor a. The positive control group consisted of iDPSCs, and the negative control group consisted of normal dental pulp stem cells.

[0033] Figure 11 Example 4 shows the in vitro hydrogen peroxide scavenging rate of MOF@Cr-Al at concentrations of 200 μM and 8 mM.

[0034] Figure 12 Example 4 shows the results of flow cytometry detection of reactive oxygen species (ROS) levels in iDPSCs before and after MOF@Cr-Al treatment, and statistical analysis of the average fluorescence intensity of flow cytometry data. P-values ​​were derived from the significance analysis of the differences between the experimental group and the iDPSCs group. **P < 0.01 indicates a statistically significant difference.

[0035] Figure 13 In Example 5, the growth of Escherichia coli treated with MOF@Al, MOF@Cr, and MOF@Cr-Al was detected and the colony count was statistically analyzed using the plate coating method.

[0036] Figure 14 Scanning electron microscopy results of Porphyromonas gingivalis and Escherichia coli before and after treatment with MOF@Al, MOF@Cr, and MOF@Cr-Al in Example 5.

[0037] Figure 15 Example 6 shows the results of Alizarin Red staining of inflammatory dental pulp stem cells after osteogenic induction for 14 days using different treatment groups MOF@Al, MOF@Cr, and MOF@Cr-Al. The negative control was normal human dental pulp stem cells (hDPSC), and the positive control was hDPCS (hDPSC+OM) containing osteogenic induction medium.

[0038] Figure 16In Example 6, RT-qPCR was used to measure the changes in mRNA expression levels of multiple markers related to osteogenic and odontoblast differentiation in iDPSCs treated with MOF@Cr, MOF@Al, and MOF@Cr-Al for 7 days.

[0039] Figure 17 In Example 6, RT-qPCR was used to measure the changes in mRNA expression levels of multiple markers related to osteogenic and odontoblast differentiation in iDPSCs treated with MOF@Cr, MOF@Al, and MOF@Cr-Al for 14 days.

[0040] Figure 18 In Example 7, after 7 days of root canal capping treatment with MOF@Al, MOF@Cr, and MOF@Cr-Al in different treatment groups, sagittal sections of the maxillary first molar in a rat model of diffuse pulpitis were stained with hematoxylin and eosin. The results showed the presence of dentin cambium cells in the inner wall of the root canal.

[0041] Figure 19 Immunohistochemical staining results of osteopontin in sagittal sections of the maxillary first molar of a rat model of diffuse pulpitis after 7 days of root canal capping treatment with MOF@Al, MOF@Cr and MOF@Cr-Al in different treatment groups. Detailed Implementation

[0042] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0043] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art; unless otherwise specified, the reagents used in the embodiments are all commercially available.

[0044] Example 1: Preparation and characterization of GelMA-MOF@Cr-Al

[0045] 1) Dissolve 2-methylimidazole (5mM), aluminum nitrate (2mM) and chromium chloride hexahydrate (2mM) in deionized water and react at 37°C for 30 minutes;

[0046] 2) After centrifugation (12000 rpm, 5 minutes), collect the precipitate, wash it 3 times with PBS, and disperse it for later use;

[0047] 3) Mix GelMA (10% w / v) with 0.25% LAP aqueous solution and heat at 60°C until completely dissolved;

[0048] 4) Add MOF@Cr-Al (2.5% by mass), vortex mix well, and then inject into the mold;

[0049] 5) Irradiate with a 405nm light source for 15 seconds to solidify and obtain a porous hydrogel.

[0050] Experimental results are as follows Figure 2 As shown, the hydrogel composite in solution was photocured under ultraviolet light at a wavelength of 405 nm for 15 seconds. After ultraviolet irradiation, the hydrogel composite formed a stable solid morphology, and chromium-aluminum metal-organic framework hydrogel (GelMA-MOF@Cr-Al) could be obtained.

[0051] The morphologies of MOF@Al, MOF@Cr, and MOF@Cr-Al were characterized using transmission electron microscopy and scanning electron microscopy, such as... Figure 3 and Figure 4 As shown, the synthesized MOF@Al, MOF@Cr, and MOF@Cr-Al exhibit uniform and stable particle sizes, displaying a cuboid structure with particle sizes ranging from 50 to 100 nm.

[0052] Furthermore, after freeze-drying, the morphology of GelMA, GelMA-MOF@Cr, GelMA-MOF@Al, and GelMA-MOF@Cr-Al was analyzed by scanning electron microscopy, and the elemental composition was analyzed by energy-dispersive X-ray spectroscopy (EDS). Figure 5 Scanning electron microscopy results showed that GelMA-MOF@Cr, GelMA-MOF@Al, and GelMA-MOF@Cr-Al exhibited porous surface morphologies, and Cr and Al elements were uniformly distributed in the material. Furthermore, as... Figure 6 Elemental analysis using X-ray photoelectron spectroscopy (XPS) also showed the presence of Cr and Al elements in the hydrogel.

[0053] To evaluate the ion release capacity of GelMA-MOF@Cr-Al, the material was immersed in phosphate-buffered saline (PBS, pH 7.4), and the Cr content in the leachate was measured at 0, 6, 12, 24, and 48 hours. 3 The concentrations of Al+ and Al3+. For example... Figure 7 and Figure 8 As shown, compared to GelMA-MOF@Cr or GelMA-MOF@Al alone, GelMA-MOF@Cr-Al exhibited lower ion concentrations under physiological conditions and at the same time points (24 hours and 48 hours), indicating that GelMA-MOF@Cr-Al can achieve the slow release of metal ions Cr. 3 The effects of + and Al3+ are beneficial for long-term treatment of pulpitis.

[0054] Example 2: In vitro cell compatibility assessment of GelMA-MOF@Cr-Al

[0055] To further explore its potential application in human dental pulp stem cell (hDPSC) therapy, we investigated the cytotoxicity of MOF@Cr-Al against hDPSC. The results are as follows: Figure 9 The effect of MOF@Cr-Al on hDPSC proliferation was evaluated using a CCK-8 assay. hDPSCs were treated with MOF@Al, MOF@Cr, and MOF@Cr-Al for 1, 3, 5, and 7 days, respectively. The CCK-8 results showed that, compared with the blank control group, different concentrations of MOF@Cr-Al did not inhibit hDPSC proliferation, indicating that MOF@Cr-Al possesses good biocompatibility.

[0056] Example 3: Anti-inflammatory properties of MOF@Cr-Al

[0057] To investigate the effects of MOF@Cr-Al on the expression of inflammatory cytokines in inflammatory dental pulp stem cells (iDPSCs), quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to measure the levels of inflammatory cytokines under different treatment conditions. Figure 10 As shown, after 3 hours of stimulation with lipopolysaccharide (LPS), the expression levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were significantly upregulated in iDPSCs. However, after treatment with MOF@Al, MOF@Cr, and MOF@Cr-Al, the mRNA expression levels of these inflammatory factors (IL-6 and TNF-α) were significantly downregulated in iDPSCs. These results indicate that MOF@Cr-Al possesses good anti-inflammatory capabilities.

[0058] Example 4: Determination of reactive oxygen species scavenging capacity of MOF@Cr-Al

[0059] To evaluate the reactive oxygen species scavenging ability of MOF@Cr-Al, a hydrogen peroxide (H2O2) detection kit (Beyotime, product number: S0038) was used for detection. Figure 11 As shown, with increasing MOF@Cr-Al concentration, the H2O2 scavenging rate increased from 9.4% at 200 μmol / L to 38.0% at 8 mmol / L. These results indicate that MOF@Cr-Al possesses catalase-like activity and the ability to scavenge reactive oxygen species.

[0060] In addition, intracellular reactive oxygen species levels in iDPSCs treated with MOF@Cr-Al were assessed. Flow cytometry results ( Figure 12 The results showed that, compared with untreated hDPSC, LPS-treated iDPSC produced a large amount of reactive oxygen species. After treatment with MOF@Cr-Al, the reactive oxygen species level in iDPSC was significantly reduced.

[0061] Example 5: Evaluation of the antibacterial properties of MOF@Cr-Al

[0062] The antibacterial activity of MOF@Cr-Al against *Escherichia coli* was evaluated using colony counting, and morphological changes in MOF@Cr-Al-treated bacteria were observed using scanning electron microscopy (SEM). MOF@Al, MOF@Cr, and MOF@Cr-Al were co-cultured with *Escherichia coli* and *Porphyromonas gingivalis* for 16 and 24 hours, respectively, with phosphate-buffered saline (PBS) as a blank control. Colony counting was performed on culture dishes. Figure 13 As shown, there was a significant difference between the experimental group and the control group. The antibacterial effect of MOF@Cr-Al increased with increasing concentration, and no visible colonies formed in the culture dishes treated with 50 μmol / L MOF@Cr-Al.

[0063] Scanning electron microscope (SEM) Figure 14 The results showed that *E. coli* treated with MOF@Cr-Al exhibited flagella breakage and cell surface shrinkage. *Porphyromonas gingivalis* also showed surface shrinkage, indicating that MOF@Cr-Al affected the normal morphology of *Porphyromonas gingivalis*.

[0064] Example 6: Biological effects on the odontogenic effects of iDPSCs

[0065] To investigate the effects of MOF@Cr-Al on osteogenic and odontoblastic differentiation of iDPSCs, the expression levels of markers related to osteogenic and odontoblastic differentiation in MOF@Cr-Al treated cells were assessed by Alizarin Red S (ABS) staining and RT-qPCR experiments.

[0066] Alizarin Red S staining results ( Figure 15 The results showed that osteogenic-induced hDPSCs exhibited significantly enhanced staining compared to normal dental pulp stem cells (hDPSCs) and inflammatory dental pulp stem cells (iDPSCs). However, iDPSCs treated with MOF@Al and MOF@Cr-Al showed significantly increased staining, indicating a promoting effect on osteogenic / odontogenic differentiation. In contrast, iDPSCs treated with MOF@Cr showed lighter staining, with no significant difference compared to iDPSCs that underwent osteogenic induction alone.

[0067] RT-qPCR was used to measure the changes in mRNA expression levels of several markers related to osteogenic and odontogenic differentiation in iDPSCs treated with MOF@Cr, MOF@Al, and MOF@Cr-Al. Untreated hDPSCs expressed low levels of alkaline phosphatase (ALP), osteocalcin (OCN), RUNX-associated transcription factor 2 (RUNX2), and dentin salivary phosphoprotein (DSPP). Osteogenically induced hDPSCs significantly upregulated the expression of ALP, OCN, and RUNX2, while osteogenically induced iDPSCs downregulated the expression of ALP, OCN, RUNX2, and DSPP. Figure 16 As shown, at 7 days, MOF@Cr-Al and MOF@Al treatments significantly increased the expression levels of ALP, RUNX2 and DSPP (p<0.05), while MOF@Cr treatment only upregulated RUNX2 expression (p<0.01), and no significant changes were observed in other markers.

[0068] like Figure 17 As shown, after 14 days of osteogenic induction, MOF@Al and MOF@Cr-Al significantly upregulated the mRNA expression levels of ALP, OCN, RUNX2, and DSPP (p<0.05). MOF@Cr also moderately upregulated the expression of ALP, OCN, and RUNX2, although the upregulation of ALP and OCN was relatively weak (p<0.05). These experiments indicate that MOF@Cr-Al significantly promoted the mRNA expression of markers related to osteogenic and odontoblastic differentiation in inflammatory dental pulp stem cells, thus MOF@Cr-Al has the function of promoting osteogenic and odontoblastic differentiation.

[0069] Example 7: In vivo anti-inflammatory properties of GelMA-MOF@Cr-Al

[0070] A rat pulpitis model was established to evaluate the anti-inflammatory and reparative effects of GelMA-MOF@Cr-Al in vivo. Histological evaluation was performed using hematoxylin-eosin staining and immunohistochemical staining to assess inflammatory cell infiltration, pulp tissue status, reparative dentin formation, and secondary infection, thereby evaluating the efficacy of the pulp covering material. Rat molar pulp was stimulated with 1 μmol / L E. coli LPS for 10 minutes, followed by direct filling without pulp covering. One week after treatment, rat molar pulp was harvested for decalcification, sectioning, hematoxylin-eosin staining, and immunohistochemical staining.

[0071] Hematoxylin-eosin staining results ( Figure 18The results showed that after 7 days of LPS treatment, a diffuse inflammatory response appeared in the dental pulp tissue, with degradation and degeneration of the pulp tissue from the exposed pulp chamber to the middle and upper root canals. Furthermore, no clear cell nuclei or matrix tissue were observed, and the odontoblast layer disappeared in the root canals. Extensive lymphocytic infiltration was observed in the lower root canal and apical region, with small, round, and deeply stained nuclei, indicating a successful establishment of the rat pulpitis model. In the GelMA pulp coverage group, significant lymphocytic infiltration was observed in the rat pulp chamber and root canals, indicating a diffuse inflammatory response and the disappearance of the odontoblast layer. This indicates that GelMA alone has no significant effect on rat pulpitis.

[0072] Samples from both the GelMA-MOF@Cr-Al and conventional pulp capping material (mineral trioxide polymer (MTA)) groups showed localized lymphocytic infiltration and fibrotic pulp tissue beneath the capping material, while the pulp tissue within the root canals maintained a relatively normal structure. However, in the MTA group, the odontoblast layer in the root canals was disordered and unclear. In contrast, the GelMA-MOF@Cr-Al group exhibited a clear odontoblast layer with tall, palisade-like cell arrangement. This indicates that GelMA-MOF@Cr-Al possesses good anti-inflammatory properties and the ability to restore the odontoblast layer structure.

[0073] Example 8: In vivo regeneration properties of GelMA-MOF@Cr-Al

[0074] To further evaluate the differentiation capacity of odontoblasts after pulp coverage, immunohistochemical staining with osteocalcin (OCN) was performed. The staining results are as follows: Figure 19 As shown, in the GelMA-MOF@Cr-Al pulp covering group, a tightly packed layer of odontoblasts was observed lining the root canal wall, with strong brownish-yellow positive staining in the cytoplasm, indicating high OCN expression levels. GelMA-MOF@Cr-Al promotes odontoblast differentiation and enhances OCN expression, highlighting its potential as an effective pulp covering material.

Claims

1. A photoresponsive hydrogel composite material, characterized in that, The invention comprises a metal-organic framework material MOF@Cr-Al, which is self-assembled from metal ions Cr³⁺ and Al³⁺ with an organic ligand, and a methacrylamide gelatin (GelMA) hydrogel. MOF@Cr-Al consists of nanoparticles uniformly distributed within the GelMA hydrogel, with an addition amount of 2.5% to 5% of the GelMA hydrogel's mass. The GelMA hydrogel also contains a photoinitiator that initiates cross-linking and curing of the GelMA hydrogel under light irradiation. The organic ligand is 2-methylimidazole.

2. The photoresponsive hydrogel composite material as described in claim 1, characterized in that, The MOF@Cr-Al is a nanoparticle synthesized by hydrothermal reaction of 2-methylimidazolium, aluminum nitrate and chromium chloride hexahydrate. It has a cuboid morphology and a particle size of 50~100 nm.

3. The photoresponsive hydrogel composite material as described in claim 2, characterized in that, Cr³⁺ and Al³⁺ are uniformly distributed in MOF@Cr-Al nanoparticles, and their molar ratio is Cr³⁺:Al³⁺ = 1:1 to 3:

1.

4. The photoresponsive hydrogel composite material as described in claim 1, characterized in that, The photoinitiator is LAP.

5. A method for preparing the photoresponsive hydrogel composite material according to any one of claims 1 to 4, comprising the following steps: 1) Synthesize MOF@Cr-Al nanoparticles and disperse them in a buffer solution; 2) Prepare an aqueous solution of GelMA and add a photoinitiator; 3) Add MOF@Cr-Al nanoparticles to GelMA aqueous solution in a certain proportion, mix evenly, and then crosslink by light and solidify.

6. The preparation method according to claim 5, characterized in that, Step 1) MOF@Cr-Al nanoparticles were synthesized by solvothermal reaction of 2-methylimidazole, aluminum nitrate and chromium chloride hexahydrate. The precipitate was collected by centrifugation, washed and dispersed in phosphate buffer.

7. The preparation method according to claim 5, characterized in that, The photoinitiator mentioned in step 2) is LAP, and crosslinking is performed using 405 nm light in step 3).

8. The preparation method according to claim 7, characterized in that, Step 2) Add 5%~10% GelMA and 0.25% LAP photoinitiator to water and heat to 60~70℃ to form a homogeneous solution.

9. The use of the photoresponsive hydrogel composite material according to any one of claims 1 to 4 in the preparation of a drug for treating pulpitis.

10. The application as described in claim 9, characterized in that, The pulpitis mentioned includes acute and chronic pulpitis caused by bacterial infection, trauma, or chemical irritation.

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