Near-Infrared Squaraine Dye Encapsulated Micelles for in Vivo Fluorescence and Photoacoustic Bimodal Imaging

Combined near-infrared (NIR) fluorescence and photoacoustic imaging techniques present promising capabilities for noninvasive visualization of biological structures. Development of bimodal noninvasive optical imaging approaches by combining NIR fluorescence and photoacoustic tomography demands suitable NIR-active exogenous contrast agents. If the aggregation and photobleaching are prevented, squaraine dyes are ideal candidates for fluorescence and photoacoustic imaging. Herein, we report rational selection, preparation, and micelle encapsulation of an NIR-absorbing squaraine dye (D1) for in vivo fluorescence and photoacoustic bimodal imaging. D1 was encapsulated inside micelles constructed from a biocompatible nonionic surfactant (Pluoronic F-127) to obtain D1-encapsulated micelles (D1micelle) in aqueous conditions. The micelle encapsulation retains both the photophysical features and chemical stability of D1. D1micelle exhibits high photostability and low cytotoxicity in biological conditions. Unique properties of D1micelle in the NIR window of 800–900 nm enable the development of a squaraine-based exogenous contrast agent for fluorescence and photoacoustic bimodal imaging above 820 nm. In vivo imaging using D1micelle, as demonstrated by fluorescence and photoacoustic tomography experiments in live mice, shows contrast-enhanced deep tissue imaging capability. The usage of D1micelle proven by preclinical experiments in rodents reveals its excellent applicability for NIR fluorescence and photoacoustic bimodal imaging.NRF (Natl Research Foundation, S’pore)Accepted versio

Donor-Acceptor Dyes for Organic Photovoltaics

Small-molecule pi-systems bearing donor (D) and acceptor (A) groups constitute an interesting class of dyes because of their tunable strong absorption, which covers the visible and near-infrared range. The dipolarity associated with D-A structures directs antiparallel stacking arrangements in the solid state, thus reducing the dipolar disorder at the supramolecular level. Their straightforward synthesis and purification make them good candidates for photovoltaic application with power conversion efficiencies > 6 %. This review summarizes the application of D-A dyes, and in particular merocyanines, in organic photovoltaics in recent years