We report a series of alkyne-functionalized meso-aryl boron dipyrrin (BODIPY) molecular rotors sensitive to viscosity. The planar and twisted conformation within the molecular structure decides the viscosity-dependent behavior. The variations in fluorescence lifetime and intensity were appreciable to the local viscosity. Hence, the dye has been successfully employed in the enumeration of microbes by considering the proportionate fluorescence intensity of the BODIPYs as an index of the number of cells per mL. With increasing cells per mL, the viscosity of the bacterial solution is increased. Consequently, the fluorescence intensity of the sample containing BODIPY tends to increase due to the restricted rotation in the viscous medium. The BODIPY probe offers high sensitivity and is easier than other conventional techniques of colony-forming unit (CFU) determination. The theoretical studies indicate that intramolecular charge transfer is responsible for the enhanced fluorescence intensity in a highly viscous solvent.

中文翻译：

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开发炔烃-BODIPYs 作为细菌细胞计数的粘度敏感荧光探针

我们报告了一系列炔烃功能化的中观-芳基硼二吡啶 (BODIPY) 分子转子对粘度敏感。分子结构内的平面和扭曲构象决定了粘度依赖性行为。荧光寿命和强度的变化与局部粘度有关。因此，通过将 BODIPY 的比例荧光强度作为每毫升细胞数的指标，该染料已成功用于微生物计数。随着每毫升细胞的增加，细菌溶液的粘度增加。因此，由于在粘性介质中旋转受限，含有 BODIPY 的样品的荧光强度趋于增加。BODIPY 探针具有高灵敏度，并且比其他传统的菌落形成单位 (CFU) 测定技术更容易。