Research On Design,Synthesis And Application Of Novel Polysaccharide Composite Materials

Basing on the research status of natural polysaccharide materials at home and abroad,a series of novel biocompatible hydrogel materials were prepared by chemical cross-linking and physical cross-linking methods using pullulan,agarose and salecan as the gel matrix.The relationship between the type,structure and concentration of cross-linking agents and the physical-chemical properties of the hydrogel was systematically explored.These polysaccharide gels were functionally modified by introducing nanoparticles and biomimetic polymers.The obtained research results have important academic value and guiding significance for the design and functionalization of polysaccharide gel materials.The main research contents and conclusions were summarized as follows:1.Influence of the chain length of the cross-linking agent on the gel properties and the functional construction of the nanocomposite polysaccharide hydrogelPullulan hydrogels were constructed by chemical crosslinking at room temperature,while glycidyl ethers(epichlorohydrin,ethylene glycol diglycidyl ether,and 1,4-butanediol diglycidyl ether)were used as the crosslinker.Under the influence of pullulan intermolecular repulsion,the crosslinking degree is proportional to the chain length of the crosslinking agent.Increasing the chain length of the crosslinker(from 3 to 12 atomic lengths)can reduce the gel pore sizes(from 338 to 182?m)and increase the storage modulus of gel(from 250 Pa to 800 Pa).Based on the above studies,1,4-butanediol diglycidyl ether(with the longest chain length)was chosen as cross-linking agent,and nanomontmorillonite was introduced into the resulting hydrogel network to construct the nanocomposite polysaccharide hydrogel.The incorporation of nanoparticles further increased the storage modulus of gel(from 800Pa to 1200 Pa).The maximum adsorption capacity of the obtained nano-composite gel to crystal violet was 80 mg/g.The results of this study are helpful for understanding the structure-activity relationship between the chain length of the cross-linking agent and the properties of the corresponding hydrogel materials,and provide new ideas for the design of bioadsorbents.2.Effects of crosslinker configuration on gel performance and functional construction of polydopamine complex pullulan hydrogelDumbbell-shaped neopentyl glycol diglycidyl ether(NGDE,two arms)and T-shaped trimethylolpropane triglycidyl ether(TTE,three arms)were selected as cross-linking agents to study the relationship between the configuration of crosslinker and properties of the resulting pullulan hydrogels.Through density functional theory(DFT)calculations,the conformation,energy level,and electrostatic potential(ESP)of NGDE and TTE were evaluated.The results show that the energy gap of NGDE(8.44 e V)is lower than that of TTE(8.81 e V),and the terminal oxygen atomic charge density of NGDE is higher(more red areas are displayed in the ESP image),that is,NGDE has higher reactivity.When the configuration of the crosslinker changed from three arms(TTE)to two arms(NGDE),the hydrogel pore sizes decreased from 150?m to 110?m,and the storage modulus of hydrogels increased from 49 Pa to 740 Pa.Based on the above research results,the dual-arm cross-linking agent NGDE was used,while the biomimetic polymer polydopamine was used to functionally modify the pullulan hydrogel.The resulting composite hydrogel can selectively adsorb cationic organic dyes,the maximum adsorption capacity was 96 mg/g.This study describes the the structure-activity relationship between the crosslinker configuration and the hydrogel properties,and provides a new strategy for the functionalization of natural polysaccharide hydrogels.3.Functional construction of novel polydopamine-polysaccharide composite hydrogel as drug controlled release vectorBased on the results of the above study,dumbbell-shaped polyethylene glycol glycidyl ether with a long hydrophilic chain(about 21 atoms in length)was selected as the cross-linking agent,and the pullulan polysaccharide hydrogel with uniform texture was formed at 30 ^oC.The presence of a hydrophilic chain makes polyethylene glycol glycidyl ether hydrophilous.The introduction of polydopamine into the gel network changed the micro-morphology of the polysaccharide hydrogel,making the originally dense honeycomb structure rough.With the increase of the polydopamine content,the pores of hydrogels could increase from 205?m to 348?m,the modulus of hydrogels could reduce from 449 Pa to 69 Pa.The introduction of polydopamine endows the pullulan hydrogel with p H-responsive drug release behavior,and the cumulative release of the model drug crystal violet at p H 7.4 and 5.0 was 60.3%and87.0%,respectively.In vitro cytotoxicity studies(L929)showed that the complex polysaccharide gel did not show cytotoxicity even at high concentrations(3.4 mg/m L).This work provides a new strategy for the design of drug controlled release gel vectors.4.Synthesis and characterization of the polysaccharide metal coordination hydrogelIn this work,the ability of salecan to form gels with 11 kinds of metal ions was checked.It was found that Cr³⁺could effectively interact with salecan to form gels.The minimum amount of Cr³⁺(as a physical gelling agent)to promote the formation of salecan metal hydrogel is 0.2 wt%,below which the entire system exists in the liquild form.Cr³⁺dosage can regulate the structure and properties of the obtained metal coordination hydrogels.When the concentration of Cr³⁺increases from 0.2 wt%to 2.0 wt%,the pores of the gel decrease from 880?m to 520?m,and the storage modulus increases from 1310 Pa to 5700 Pa.The water absorption and dehydration behavior of the gel system showed that an increase in the concentration of chromium ions and salt would cause a significant decrease in the swelling capacity of the gel.The decrease in the hydrophilicity of salecan,the increase in crosslinking density,and the complexation of carboxylate and salt ions are the synergistic mechanisms of this process.This study report for the first time a salecan-based metal coordination hydrogel and opens a new way for the design of salecan-derived polysaccharide hydrogel materials.5.Investigation on the construction and cell adhesion behavior of the agarose derived 3D cell culture hydrogel scaffoldIn this work,inspired by the mussel foot muscle protein,gel performance and cell adhesion abilities were adjusted through the integration of low-concentration polydopamine(0.05?0.2 mg/m L)with an agarose hydrogel.After the introduction of polydopamine,the porosity of the gel increased from 33?m to 60?m,and the storage modulus of the gel decreased from 28715 Pa to 20250 Pa.The cell adhesion ability of the gel is proportional to the polydopamine content.At the highest level(0.2 mg/m L),the adhesion and proliferation rate of the four fibroblasts cells MRC-5,RS1,NIH3T3,and DPSC on the gel surface are comparable to that on the cell culture flasks.The 2D migration rates of MRC-5 and RS1 on the gel surface were 218?m/day and 308?m/day,which were higher than that on the surface of the culture flask(200?m/day and 227?m/day).MRC-5 and RS1 can migrate from the surface of the gel to the inside of the gel,and the corresponding maximum 3D migration rate is 50?m/day.By fluorescently labeling F-actin and integrin-?1 in the MRC-5 and RS1 cells,it was found that increase in the polydopamine content can promote the formation of actin fibers and integrin clusters inside the cells,thereby enhancing the cell adhesion on the gel.Subcutaneous transplantation experiments in rats were used to verify the histocompatibility of the hydrogel scaffolds.The results showed that the inflammation of the tissues surrounding the agarose scaffolds was comparable with the PBS control group(as the number of inflammatory cell is equivalent)and the agarose scaffolds has no toxic effect on the vital organs of the host.This study provides a simple and convenient strategy for the construction of multifunctional hydrogel scaffolds for 3D cell culture and tissue engineering,and has potential for clinical translation applications.