Department of Polymer Science & Engineering, Polymeric Nanomaterials Laboratory, School of Applied Chemical Engineering, Kyungpook National University, 1370 Sankyuk-dong, Buk-ku, Daegu 702-701, Korea.
Reliability Assessment Center for Chemical Materials, Korea Research Institute of Chemical Technology (KRICT), 141 Gajeong-ro, Yuseong-gu, Daejeon 305-600, Korea.
ACS Appl Bio Mater. 2022 Jun 20;5(6):3057-3066. doi: 10.1021/acsabm.2c00337. Epub 2022 May 9.
Spontaneously sp-carbonized polyamides (PA1, PA2) were prepared via Knoevenagel-type side reactions of malonyl moieties under mild conditions in the polycondensation of dicarbonyl chloride and diamine. Both polymers were soluble in water and emissive in the visible region, and the fluorescence (FL) intensity and the maximum wavelength were highly dependent on the excitation wavelength and the pH. Their chemical structures and FL origin were clarified by performing various spectroscopic analyses. π*-π transition was assumed to be allowed in an enol form based on the conjugated structure formed by the side reaction; this was responsible for its pH dependency and high FL quantum efficiency. In particular, PA2, which comprises the tertiary amide linkage, showed quick endocytosis, low cytotoxicity, excellent biocompatibility, and exclusively stained lysosomes with the lowest intracellular pH. These results will help in understanding the origin of the FL emission of carbonized nanomaterials and exploring more advanced functions in the field of bioimaging.
自发碳化聚酰胺（PA1、PA2）通过在二羰基氯和二胺缩聚过程中亚丙二酰基的 Knoevenagel 型侧反应，在温和条件下制备而成。两种聚合物都可溶于水，在可见光区具有荧光发射，荧光（FL）强度和最大波长高度依赖于激发波长和 pH 值。通过进行各种光谱分析，阐明了它们的化学结构和 FL 起源。根据侧反应形成的共轭结构，假定烯醇形式允许π*-π 跃迁；这是其 pH 值依赖性和高 FL 量子效率的原因。特别是包含叔酰胺键的 PA2，表现出快速的内吞作用、低细胞毒性、优异的生物相容性，并且仅在最低细胞内 pH 值下特异性染色溶酶体。这些结果将有助于理解碳化纳米材料的 FL 发射的起源，并在生物成像领域探索更高级的功能。
