Agrawal Richa, Gorai Sudip, Yadav Sunil Suresh, Wadawale Amey P, Mula Soumyaditya
Bio-Organic Division, Bhabha Atomic Research Centre, Mumbai, India.
Homi Bhabha National Institute, Mumbai, India.
Front Chem. 2024 Oct 10;12:1473769. doi: 10.3389/fchem.2024.1473769. eCollection 2024.
With the aim to develop a FRET-based viscosity sensor, two dyad molecules, and , comprising tetraarylpyrrolo[3,2-]pyrrole (TAPP) (donor) and naked boron-dipyrromethene (BODIPY) dyes (acceptor), were designed. Dyads were synthesized via acid-catalyzed multicomponent reactions followed by Sonogashira coupling. In both dyads, the BODIPY and TAPP moieties are linked through phenylethynyl groups, which allow free rotation of the BODIPY dyes; that is, they can act as molecular rotors. This was supported by X-ray crystallographic and DFT-optimized structures. Spectroscopic studies also confirmed the presence of both TAPP and BODIPY dyes in dyads with no electronic interactions that are suitable for fluorescence resonance energy transfer (FRET). Very high energy transfer efficiency (ETE >99%) from the donor TAPP moiety to the acceptor BODIPY moiety on excitation at the TAPP part was observed. However, due to the non-fluorescent nature of naked BODIPY dyes, no fluorescence emission was observed from the BODIPY moiety in both dyads. With increasing solvent viscosities, emission from the BODIPY moieties increases due to the restricted rotation of the BODIPY moieties. Plotting the logarithms of the fluorescent intensity of dyad and the viscosity of the solution showed a good linear correlation obeying a Förster-Hoffmann equation. Non-fluorescent dyad in methanol became greenish-yellow fluorescent in a methanol/glycerol (1:1) solvent. Furthermore, with an increase in the temperature of the methanol/glycerol (1:1) system, as the viscosity decreases, the fluorescence also starts decreasing. Thus, dyad is capable of sensing the viscosity of the medium via a FRET-based "Off-On" mechanism. This type of viscosity sensor with a very large pseudo-Stokes shift and increased sensitivity will be useful for advancing chemo-bio sensing and imaging applications.
为了开发一种基于荧光共振能量转移（FRET）的粘度传感器，设计了两种由四芳基吡咯并[3,2 - ]吡咯（TAPP）（供体）和无荧光硼二吡咯亚甲基（BODIPY）染料（受体）组成的二元分子 和 。二元分子通过酸催化的多组分反应，然后进行Sonogashira偶联反应合成。在这两种二元分子中，BODIPY和TAPP部分通过苯乙炔基相连，这使得BODIPY染料能够自由旋转；也就是说，它们可以作为分子转子。这一点得到了X射线晶体学和密度泛函理论（DFT）优化结构的支持。光谱研究也证实了二元分子中同时存在TAPP和BODIPY染料，且不存在适合荧光共振能量转移（FRET）的电子相互作用。在TAPP部分激发时，观察到从供体TAPP部分到受体BODIPY部分的能量转移效率非常高（ETE>99%）。然而，由于无荧光BODIPY染料的非荧光性质，在这两种二元分子中均未观察到BODIPY部分的荧光发射。随着溶剂粘度的增加，由于BODIPY部分的旋转受限，BODIPY部分的发射增加。绘制二元分子 的荧光强度对数与溶液粘度的关系图，显示出符合Förster - Hoffmann方程的良好线性相关性。在甲醇中无荧光的二元分子 在甲醇/甘油（1:1）溶剂中变为黄绿色荧光。此外，随着甲醇/甘油（1:1）体系温度的升高，由于粘度降低，荧光也开始减弱。因此，二元分子 能够通过基于FRET的“关 - 开”机制检测介质的粘度。这种具有非常大的伪斯托克斯位移和更高灵敏度的粘度传感器将有助于推进化学生物传感和成像应用。
