We report a library of functionalized lignins and demonstrate their utility as nanocontainers for organic dyes in biologically relevant applications. Kraft lignin was modified via SN2 reaction at the phenolic -OH group utilizing a mild base, potassium carbonate, and various alkyl halides, several bearing additional functionalities, with dimethylsulfoxide as solvent. The resulting phenoxy ethers were characterized by 1H-NMR and IR spectroscopy, as well as DLS and SEM to evaluate their morphology and supramolecular organization. Lignin modified with long-chain hydrocarbon tails was found to effectively encapsulate DiD, a cyanine dye, decrease aggregation, enhance optical transitions and exert a photoprotective effect. The dye-lignin assemblies were also examined as imaging agents, via confocal microscopy, and found to accumulate intracellularly with no leaching of the dye to hydrophobic subcellular components observed. Lignin functionalized with short chain carboxylic acids effectively interacts with ligands directed at the norepinephrine transporter (NET), suggesting applications in sequestration of neuroactive compounds.

中文翻译：

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功能化木质素生物材料，可增强染料的光学性质和细胞相互作用

我们报告了一个功能化的木质素文库，并展示了它们在生物学相关应用中作为有机染料纳米容器的效用。通过使用弱碱，碳酸钾和各种烷基卤化物的SN2反应在酚-OH基上通过SN2反应对牛皮纸木质素进行了改性，其中一些具有附加的功能，并使用二甲基亚砜作为溶剂。所得苯氧基醚通过1 H-NMR和IR光谱以及DLS和SEM进行表征，以评估其形态和超分子组织。发现用长链烃尾修饰的木质素可以有效地包封花青染料DiD，减少聚集，增强光学跃迁并发挥光保护作用。还通过共聚焦显微镜检查了染料-木质素组装体是否作为显像剂，并且发现在细胞内积累，而没有观察到染料向疏水性亚细胞组分的浸出。用短链羧酸官能化的木质素可有效地与去甲肾上腺素转运蛋白（NET）的配体相互作用，从而提示其在螯合神经活性化合物中的应用。