水/助溶剂体系中漆酶活化木质素的功能化及其纳米颗粒的构建

Lignin nanoparticle will have a promising application in many fields such as composite materials and biomedical engineering due to its great properties including richness in active groups, aqueous dispersion, renewability, biodegradability and good biocompatibility. However, the former methods of lignin nanoparticle preparation underwent low efficiency, poor suitability, employing hazard organic solvents and difficulty to functionalization, resulting from the complicate structure and slightly solubility of lignin. In our previous work, we have found that the lignin nanoparticles could be self-assembly formed through adjusting the concentration of hydrotrope in water. Hence, we plan to activate the lignin using laccase in the water/hydrotrope system with recyclable and non-toxic properties, make the active groups of lignin functionalization such as pH response, photothermal effect and magnetic response, then force the self-assemble formation of nanoparticles from lignin with or without modifications via modulate the concentration of hydrotrope in water. The mechanism of laccase activation of lignin will be exploited as well as the efficiency of functionalization in the present solvent system. The factors including processing pH value, species of hydrotrope and intrinsic properties of lignin will be investigated to understand the physiochemical properties of lignin nanoparticles. We hope to provide an efficient and sustainable method for producing functional lignin nanoparticles, as well as theoretical foundation and application prospect for highly valued utilization of lignin.

木质素纳米颗粒由于其富含活性基团、水分散性、可再生性、可生物降解性及良好的生物相容性，将在很多领域如复合材料和生物医学工程有广阔的应用前景。但由于木质素结构的复杂性及难溶性，目前木质素纳米颗粒的制备方法效率低、适应性差、使用有毒的有机溶剂且后期难以功能化。在前期研究中，申请人发现通过调节助溶剂水溶液浓度，可使木质素自组装为纳米颗粒。基于此，本项目拟在可回收无毒的水/助溶剂体系中对木质素进行漆酶活化，利用木质素自身或经活化新增的活性基团进行功能化（如有pH响应、光热效应和磁响应），然后通过调节助溶剂水溶液浓度使经过或未经过改性的木质素自组装成纳米颗粒。探讨木质素在该溶剂体系中漆酶活化机制及功能化的效率。将系统研究pH值、助溶剂类别、木质素自身性质等因素对所形成的纳米颗粒理化性能的影响规律。以期为功能化木质素纳米颗粒的合成提供高效可持续的制备方法，给木质素的高附加值利用提供理论基础及应用依据。

木质素是地球上储量最丰富的多酚类天然高分子，它的高值化利用将削弱对石油基高分子材料的依赖，有利于减少碳足迹和实现碳中和。然而，木质素不同来源的异质性是制约其高值规模化利用的主要因素之一。通过自组装合成易于水分散的具有规整形态的木质素微纳米粒子，可有效消除它的异质性问题。目前，纳米木质素的合成方法及应用已取得一定程度的进展，且在多个领域展现出优异性能及应用潜力。但是，纳米木质素形成机制的不明确性制约其可控合成及精准功能化。本项目结合密度泛函理论（DFT），半经验量子化学（SQC）和分子动力学（MD）等多尺度研究纳米木质素的形成机理。最终，我们发现γ-戊内酯(GVL)这一种绿色无毒的溶剂对LNPs的形成和功能化表现出优异的能力。它不仅能以合适的方式与木质素和药物分子相互作用，使木质素堆积成稳定均匀的球形载药LNPs，并且，GVL可以在酸性或加热环境中水解为4-羟基戊酸(HVA)，从而协同稳定金属纳米粒子(如AuNPs)作为光热转化剂。本项目揭示了木质素纳米球形成的内在驱动力为木质素分子内芳环的堆叠作用，为挑选合适的溶剂体系制备具有特定性质的纳米木质素具有重要的指导性意义。同时，采用木质素纳米粒子稳定植物精油，使植物精油的抗菌效果取得了大幅度的提升，为抗菌领域提供了一种优异的载体材料。另外，对LNPs的体外细胞毒性、血液相容性、降解性和急性毒性做了评估，显示出其较低的体外细胞毒性和较好的血液相容性，尾静脉注射的LD50高度800mg/kg。在此基础上，尝试了注射高剂量LNPs（300mg/kg）的手段进行肿瘤治疗，结果显示该策略可提高药物的靶向效果，甚至高于同源肿瘤细胞膜伪装的载体，实现肿瘤的高效治疗。因此，纳米木质素低成本、可再生可降解及良好的生物相容性，结合高剂量注射纳米材料提高药物靶向病灶的策略将为肿瘤治疗提供有价值的参考。