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

Abstract

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 (D1(micelle)) in aqueous conditions. The micelle encapsulation retains both the photophysical features and chemical stability of D1. D1(micelle) exhibits high photostability and low cytotoxicity in biological conditions. Unique properties of D1(micelle) 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 D1(micelle), as demonstrated by fluorescence and photoacoustic tomography experiments in live mice, shows contrast-enhanced deep tissue imaging capability. The usage of D1(micelle) proven by preclinical experiments in rodents reveals its excellent applicability for NIR fluorescence and photoacoustic bimodal imaging.

Ion‐in‐Conjugation: Squaraine as an Ultrasensitive Ammonia Sensor Material

“…In squaraines' resonance forms, there are always one (two) electron(s) intramolecularly transferred from the over‐bonded N in arylamine to carbonyl O of squaric ring, forming a resonance‐stabilized zwitterionic structure (N + and O − in Figure a). Such an ion‐in‐conjugation structure produces strong absorption, high photostability, and therefore rendering squaraines highly attractive in optoelectronics . Our thin‐film chemiresistor from a typical squaraine molecule ((Z)‐2‐( p ‐toluidino)‐3‐oxo‐4‐( p ‐tolyliminio) cyclobut‐1‐enolate (noted as SA‐CH 3 as in Figure a) shows an ammonia detection limit as low as 40 ppb, which is the lowest one among all reported small molecule‐based electrical sensors (Table ).…”

Photoacoustic Imaging: Contrast Agents and Their Biomedical Applications

“…The C‐HSA‐BOPx‐IR825 NP was employed to test the pH in the tumor region by both ratiometric PA and fluorescence imaging. Other NIR dyes, including naphthalocyanines, phthalocyanine, croconine, squaraine, and Prussian blue, can also serve as PA contrast agents.…”

Nitrogen‐Doped Carbon Quantum Dot Stabilized Magnetic Iron Oxide Nanoprobe for Fluorescence, Magnetic Resonance, and Computed Tomography Triple‐Modal In Vivo Bioimaging

“…Medical imageology is an important part of clinical medicine since it can make accurate diagnosis for the location and nature of the lesion which is essential for the follow‐up treatment. Currently, medical imaging diagnosis techniques mainly include X‐ray diagnostic (such as computed radiography, digital radiography, and digital subtraction angiography), X‐ray computed tomography (CT), photoacoustic and ultrasound imaging, magnetic resonance imaging (MRI), optical imaging, and position emission tomography . Among them, fluorescence (FL), magnetic resonance (MR), and CT imaging are the most routinely applied imaging diagnostic techniques.…”