Molecular Design of Ultrabright Semiconducting Polymer Dots with High NIR‐II Fluorescence for 3D Tumor Mapping

Abstract

Fluorescence probes emitting in the second near-infrared (NIR-II, 1000-1700 nm) window with the ability for deep-tissue imaging in mammals herald a new era in surgical methodology. However, the brightness of these NIR-II probes is still far from satisfactory due to their low fluorescence quantum yields (QYs), preventing the observation of high-resolution images such as whole-organ vascular networks in real time. Described here is the molecular engineering of a series of semiconducting polymer dots (Pdots) incorporated with aggregation-induced emission moieties to exhibit the QYs as high as 14% in the NIR-II window. Benefiting from the ultrahigh brightness, a 1400 nm long-pass filter is utilized to realize in vivo 3D tumor mapping in mice. To further understand how the geometrical and electron structures of the semiconducting polymers affect their optical properties, the in-depth and thorough density-functional theory calculations are performed to interpret the experimental results. This study lays the groundwork for further molecular design of highly bright NIR-II Pdots.

Development of Stereo NIR-II Fluorescence Imaging System for 3D Tumor Vasculature in Small Animals

“…Glass capillary tubes (OD = 1.5 mm/ID = 1.1 mm) filled with IR-TPE Pdots were immersed in the Intralipid ® solution. IR-TPE Pdots were synthesized according to the method in our previous study [ 22 , 23 ]. Capillaries were immersed at depths from 1 to 6 mm from the surface.…”

“…NIR-II imaging agents have been applied in optical angiography for visualizing blood vessel structure [ 16 , 17 , 18 , 19 , 20 , 21 ]. In our previous study, NIR-II fluorescent semiconducting polymer dots (IR-TPE Pdots) were developed to obtain high SNR NIR-II blood vessel imaging [ 22 , 23 ].…”

Recent advances in D–A–D based Pdots with NIR-II fluorescence for deep-tissue imaging

“…To date, researchers have developed two methodologies to relieve the ACQ issue: 1) the introduction of bulky side groups and 2) the employment of aggregation-induced emission (AIE) moieties. 87 Additionally, the design of alternating planar and twisted molecular structures of polymers has been proved to provide both high QYs and high absorption efficiency. 21…”

“…4G). 87 In this work, [1,2,5]thiadiazolo[3,4- g ]quinoxaline was selected as the acceptor due to its outstanding electron affinity to lower the LUMO level of the polymer and alkylthio thiophene-substituted BDT was used as the donor moiety. Moreover, the bulky 3,4-ethylenedioxy thiophene spacer was inserted between the donor and acceptor to afford a conformational distortion of the polymer backbone for the additional anti-ACQ effect.…”

TADF-based NIR-II semiconducting polymer dots for in vivo 3D bone imaging

“…63–65 This is attributed to the fact that, so far, only a few Pdots have been reported to have emission maxima over 1100 nm with acceptable fluorescence quantum yields (>1%) for bioimaging. 66,67 Our group recently developed two types of NIR-II emissive Pdots: polymethines 68 and donor–acceptor–donor based conjugated polymers, 69 trying to overcome the energy gap law and the aggregation-caused quenching (ACQ) issue. However, the unbalance between the longer emission wavelength and the higher fluorescence quantum yield remains a bottleneck for exploring the next generation of NIR-II Pdots.…”