多级孔结构碳纳米管/炭复合微球的可控制备及其用于血液灌流研究

Because of their singular microporous and mesoporous structure, activated carbon and macroporous resin microspheres cannot meet the needs of hemoperfusion presently. Carbon nanotubes (CNTs), although having excellent adsorption capacity for toxins with different molecular weights and hepatitis B virus, cannot be used in hemoperfusion directly for as-produced CNTs are powdery until they could be made as microspheres with appropriate porous structure, mechanical properties and surface states. In this project, CNTs/C composite microspheres with flexible CNTs ratio and hierarchically porous structure, i.e., containing micropores, mesopores and macropores which could act as diffusing channels, would be fabricated by a dripping method in combination with a freeze casting process followed by freeze drying, carbonization and pore surface functionalization. Herein, their application in hemoperfusion would be investigated in detail as well. Since the pore structure is actually the mirror image of the crystalline of the solvent in the suspension, then the key points of this project is how to design the suspension system, the freezing medium and make clear the interactions between CNTs, binders and solvent crystallizing. The influence of composition of CNT suspension, process conditions and chemical properties on solvent crystallization during freeze casting is also studied. Probably, the intrinsic physical and chemical mechanism of solvent crystallization and CNT self-assembly could be elucidated based on the phase diagram analyses, finite element analyses and molecular dynamics simulations. As a result, the design and controllable synthesis of hierarchically porous CNTs/C composite spheres can be realized.

现役血液灌流吸附剂由于孔径单一已不能满足临床需要，尽管碳纳米管（CNTs）对不同分子量的毒素具有优异的吸附性能，有望用于血液灌流，但目前基于CNTs的微球缺乏合适的多级孔结构和综合吸附性能。本研究采用滴定法将CNTs悬浮液滴定到冷冻介质中冻铸成球，再经冻干、炭化及表面官能团配载，得到CNTs含量可控，且兼具微孔、中孔及（可作为扩散通道的）大孔的多级孔结构碳纳米管/炭（CNTs/C）复合微球，并探讨其在血液灌流领域的应用。将冻铸过程中溶剂结晶体升华后即可获得与此结晶成镜像的多孔结构，故研究核心在于悬浮液体系和冷冻介质的设计，以及从理论上明确冻铸过程中CNTs、粘结剂与溶剂结晶之间的相互作用机制。通过研究冻铸过程中CNTs悬浮液的组成、性质及工艺条件等对溶剂结晶的影响，并结合相图分析和模拟计算，揭示冻铸过程中溶剂结晶和CNTs自组装的内在机制，从而实现对多级孔结构的设计和可控构建。

血液灌流疗法可用于治疗重症肝衰、肾衰、免疫疾病、急性中毒等疾病，其疗效主要取决于血液灌流器中吸附剂的性能，现役血液灌流吸附剂由于孔径单一，疗效受限。开发多级孔结构、综合吸附性能优异的碳纳米管/炭（CNTs/C）复合微球，不仅具有较高学术价值，在血液灌流等吸附应用领域也将有广阔的使用前景。.本课题主要研究并完成了多级孔结构CNTs/C复合微球的可控制备。通过研究骨架材料与冻铸温度对孔结构的影响，确定了构建复合微球最佳骨架材料，获得了微球表面形貌和孔道结构随冻铸温度变化的影响规律，进而利用Nano-CT表征揭示了不同冻铸温度下孔结构的形成与演变机理。.通过筛选骨架材料和调控制备工艺，实现了挤出滚圆法CNTs/C复合微球的批量制备（公斤级）和10-1000 nm范围孔结构可调，复合微球对VB12和溶菌酶的饱和吸附量和吸附速率均远高于商用样品（活性炭和HA树脂），对溶菌酶的2 h饱和吸附量达到商用活性炭样品的6倍以上。进一步研究发现，通过调控微球成型干燥方式、成球辅料、溶剂等关键因素，能解决CNTs/C复合微球力学性能和吸附性能难以调和的矛盾，实现了在提高微球强度的前提下，保持了对中、大分子毒素优异的吸附性能，吸附能力是商用样品的5-10倍。.设计并构建了模拟体外血液灌流的实验装置。在基于CNTs/C复合微球吸附剂的血液灌流模拟实验中，新型吸附剂展现了优异的吸附动力学特性和良好的血液相容性，满足行业标准YY0464-2003。模拟实验以VB12作为吸附对象，复合微球的初始吸附速率（0.96 mg/g·min）约为商用活性炭的5倍，且30 min VB12清除率高达99.99%，有望能在实际临床治疗中缩短治疗时间，减少吸附剂用量。.在CNTs/C复合微球的研究基础上，进一步利用比表面积更大、自身孔结构更为发达的多孔炭空心球（HCSs）作为基材，探索了HCSs/C复合微球的制备，通过对其孔结构的调控，实现了对中、大分子毒素的高效清除。其良好的吸附动力学和血液相容性显示了这种炭复合微球也有作为血液灌流吸附剂的潜力。

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