Facile Preparation of Near Infrared-Luminescent Protein Complexes with Conjugated Polymers Consisting of Boron Azobenzene Units

Abstract

We report herein facile preparation of near infrared (NIR)-luminescent protein complexes with conjugated polymers. We have discovered that solid-state luminescence in the NIR region can be obtained from the series of conjugated polymers consisting of boron azobenzene complexes. We demonstrate in this paper that protein molecules can be modified through adsorption with the boron azobenzene-containing conjugated polymers simply by mixing in an aqueous buffer and subsequently purification with filtration followed by freeze drying. The modified protein complexes can exhibit NIR emission in the buffer and high dispersibility. In particular, comparing to the complex with indocyanine green (ICG), which is a conventional NIR-luminescent dye, polymer-modified protein complexes showed higher resistance to photobleaching. Finally, by using lipase as a scaffold, we confirmed that enzymatic activity can be detected after polymer modification.

NIR‐II Absorption/Fluorescence of D–A π‐Conjugated Polymers Composed of Strong Electron Acceptors Based on Boron‐Fused Azobenzene Complexes

“…This fact suggested that our materials gained high resistance toward oxidation. [20] To support experimental data, we performed density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations at B3LYP/6-311G(d,p) level (Figures 3 and S10-S12, Tables S6 and S7). In monomers, the LUMO energy levels decreased in the order of FÀ Br > CF 3 À Br > F 4 À FÀ Br > F 4 À CF 3 À Br, which was in good agreement with the results from CV (Figure 3a).…”

“…[15][16][17] In this strategy, lowering LUMO energy levels by using strong acceptor units are crucial since not only the desired optical properties but also high stability against oxidative and photodegradation are required. [18][19][20] On the other hand, a variety of strong electron acceptors are still limited. Therefore, excellent but limited strong electron acceptors such as benzobisthiadiazole, thiadiazoloquinoxaline, triazoloquinoxaline, diketopyrrolopyrrole, isoinidigo and their derivatives have been frequently used.…”