Quinoid Conjugated Polymer Nanoparticles with NIR‐II Absorption Peak Toward Efficient Photothermal Therapy**

Abstract

Recently, extensive efforts have been devoted to the development of the second near-infrared bio-window (NIR-II, 1000-1700 nm) theranostic agents owing to the excellent tissue-penetration capability of NIR-II light. The exploration of organic NIR-II photothermal therapy materials, especially those with absorption peak over 1000 nm, is an appealing yet significantly challenging task. Herein, we have designed conjugated polymer nanoparticles (PIS NPs) with NIR-II absorption peak at 1026 nm through a combined strategy of introducing quinoid donor-acceptor (D-A) structures, constructing intramolecular "conformational locks" and extending the conjugation area to narrow the band gap. Irradiated at 1064 nm, PIS NPs showed remarkable photothermal conversion performance for efficient photothermal ablation of tumor cells in vitro and in vivo. This study provides useful insights into the rational design of organic NIR-II photothermal agents based on multiple strategies.

A skeletal randomization strategy for high-performance quinoidal-aromatic polymers

“…Mixed quinoidal-aromatic CPs containing quinoidal units in the conjugated polymer backbone have exhibited distinctive optoelectronic properties and impressive semiconducting properties, inspiring complementary design principles to the classic donor–acceptor (D–A) type CPs. 26–28 The introduction of a quinoidal unit with oligothiophene in the repeat unit in the polymer backbone often leads to high mobility due to the reinforced backbone, strong interchain interaction and aggregation, high crystallinity, and dense molecular packing. 29–33 As previously demonstrated by us, a planar quinoidal building block, para -azaquinodimethane ( p -AQM), is easily accessible and has been successfully employed in organic semiconductors for OFETs and various applications.…”

High-Performance Hybrid Phototheranostics for NIR-IIb Fluorescence Imaging and NIR-II-Excitable Photothermal Therapy

“…However, the excitation wavelengths of the current PTT systems are mostly within the range of 650–900 nm (traditional near-infrared window, NIR-I), which inevitably impair the treatment outcome of deep-seated tumors due to the limited tissue penetration depth and strong background tissue absorption [ 24 , 25 , 26 , 27 ]. It is widely known that the absorption and scattering of light in biological tissue decrease as the light wavelength increases, achieving deeper tissue penetration and higher maximum permissible exposure (MPE) [ 28 , 29 , 30 , 31 ]. For instance, the MPE for a 1064 nm laser was 1 W/cm 2 , which was much higher than for a 808 nm laser (0.33 W/cm 2 ).…”