Engineering of Electrochromic Materials as Activatable Probes for Molecular Imaging and Photodynamic Therapy

Abstract

Electrochromic materials (EMs) are widely used color-switchable materials, but their applications as stimuli-responsive biomaterials to monitor and control biological processes remain unexplored. This study reports the engineering of an organic π-electron structure-based EM (dicationic 1,1,4,4-tetra­aryl­buta­diene, 1 2+) as a unique hydrogen sulfide (H2S)-responsive chromophore amenable to build H2S-activatable fluorescent probes (1 2+-semiconducting polymer nanoparticles, 1 2+-SNPs) for in vivo H2S detection. We demonstrate that EM 1 2+, with a strong absorption (500–850 nm), efficiently quenches the fluorescence (580, 700, or 830 nm) of different fluorophores within 1 2+-SNPs, while the selective conversion into colorless diene 2 via H2S-mediated two-electron reduction significantly recovers fluorescence, allowing for non-invasive imaging of hepatic and tumor H2S in mice in real time. Strikingly, EM 1 2+ is further applied to design a near-infrared photosensitizer with tumor-targeting and H2S-activatable ability for effective photodynamic therapy (PDT) of H2S-related tumors in mice. This study demonstrates promise for applying EMs to build activatable probes for molecular imaging of H2S and selective PDT of tumors, which may lead to the development of new EMs capable of detecting and regulating essential biological processes in vivo.

Hexaarylbutadiene: A Versatile Scaffold with Tunable Redox Properties towards Organic Near‐Infrared Electrochromic Material

“…In 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 this geometry, two MHB + chromophores can be stacked to each other with the shortest CÀ C contact of 3.01(2) Å. The Zconfiguration of the dication was previously found in 1 a 2 + (I 3 À ) 2 [torsion angle: 19.8(5)°, contact 2.88(1) Å] [ 9,16] or 2 a 2 + (BF 4 À ) 2 [torsion angle: 15.4(4)°, contact 3.018(5) Å]. [20] Preliminary analysis on 3 b 2 + (BF 4 À ) 2 also shows Z-configuration (Figure 4d).…”

“…Dication 1 a 2+ was found to react efficiently with H 2 S over endogenous reducing agents (e. g., glutathione, L ‐cysteine and vitamin C) in cells to give 1 a . The large difference in the absorption spectra between 1 a 2+ and 1 a can be used for the OFF/ON switching mechanism of detection, and the activatable probe for non‐invasive and real‐time detection of H 2 S was successfully constructed based on the EM of 1 a / 1 a 2+ …”

“…Although only a limited numbers of such NIR EM have been reported so far, [10][11][12][13][14][15] they are attracting considerable recent attention since the NIR absorption can be applicable for bioimaging and phototherapy. [16] Absence of heavy metals in organic EM is also favorable for their use in biological systems.…”

“…The large difference in the absorption spectra between 1 a 2 + and 1 a can be used for the OFF/ON switching mechanism of detection, and the activatable probe for non-invasive and real-time detection of H 2 S was successfully constructed based on the EM of 1 a/1 a 2 + . [16] The switching efficiency and the reaction kinetics are largely dependent on the NIR absorption and reduction potential (E red ) of NIR dye 1 a 2 + . Very recently, we synthesized decafluorinated dication 2 a 2 + (Scheme 2b), which has a red-shifted NIR absorption as well as higher E red compared to 1 a 2 + .…”

Recent progress in H2S activated diagnosis and treatment agents

“…9C). In addition, Wu et al 100 reported a class of H 2 S-activated uorescent probes and photodynamic smart reagents using electrochromic materials (EMs) with organic p-electron structure (dicationic 1,1,4,4-tetraphenylbutadiene, 1 2+ ) as H 2 Sresponsive chromophores. EM1 2+ is doped into semiconductor polymer nanoparticles (SNPs) to form H 2 Sactivatable uorescent probes (1 2+ -SNPs) (Fig.…”