Khadria Anjul, Fleischhauer Jan, Boczarow Igor, Wilkinson James D, Kohl Michael M, Anderson Harry L
Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK.
Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.
iScience. 2018 Jun 29;4:153-163. doi: 10.1016/j.isci.2018.05.015. Epub 2018 May 26.
Second harmonic generation (SHG)-based probes are useful for nonlinear optical imaging of biological structures, such as the plasma membrane. Several amphiphilic porphyrin-based dyes with high SHG coefficients have been synthesized with different hydrophilic head groups, and their cellular targeting has been studied. The probes with cationic head groups localize better at the plasma membrane than the neutral probes with zwitterionic or non-charged ethylene glycol-based head groups. Porphyrin dyes with only dications as hydrophilic head groups localize inside HEK293T cells to give SHG, whereas tricationic dyes localize robustly at the plasma membrane of cells, including neurons, in vitro and ex vivo. The copper(II) complex of the tricationic dye with negligible fluorescence quantum yield works as an SHG-only dye. The free-base tricationic dye has been demonstrated for two-photon fluorescence and SHG-based multimodal imaging. This study demonstrates the importance of a balance between the hydrophobicity and hydrophilicity of amphiphilic dyes for effective plasma membrane localization.
基于二次谐波产生（SHG）的探针可用于生物结构（如质膜）的非线性光学成像。已经合成了几种具有高SHG系数的两亲卟啉基染料，其具有不同的亲水头基，并对它们的细胞靶向性进行了研究。与具有两性离子或不带电荷的乙二醇基头基的中性探针相比，具有阳离子头基的探针在质膜上的定位更好。仅以二价阳离子作为亲水头基的卟啉染料定位于HEK293T细胞内以产生SHG，而三价阳离子染料在体外和体内均能强烈定位于包括神经元在内的细胞的质膜上。荧光量子产率可忽略不计的三价阳离子染料的铜（II）配合物用作仅产生SHG的染料。游离碱三价阳离子染料已被用于双光子荧光和基于SHG的多模态成像。这项研究证明了两亲染料的疏水性和亲水性之间的平衡对于有效的质膜定位的重要性。
