Oral Development of Mehanochromic Charge Transfer Complex Materials: Biomedical Imaging Applications both in Vitro and in Vivo

Abstract

New p-conjugated oligomers with high crystallinity were prepared from the simple solvothermal reaction of squaricacid and diaminopyrenes. The oligomers were bonded at the 1,3- and 1,6-positions of the pyrene units, which greatlyaffected their planer configuration and resulting mechanochromic properties. Oligomers containing a charge transfer (CT)complex were selectively synthesized in one step. Upon mechanical grinding in the solid state, the color changed from orangeto deep metallic green. However, this property was lost in solution. To overcome this limitation, we envisioned ordering the CTcomplexes into a templated design, on a polymer backbone to promote enhanced tumor retention for imaging applications. Itis known that the modular structure of CT complexes coupled with environmental dependence on CT properties allows thecontrol over crystal structure and optical properties by alternating CT interactions between electron donors and acceptors.Because small molecule CT complex particles have shown utility in biomedical imaging,29 we were inspired to design CTcomplexes based on supramolecular self-assembly of natural polymers, which would enable enhanced tumor retention for invivo imaging applications. Next presentation introduces newly the preparation of CT complex-connecting cellulose. The blueand red emission of CT complexes appended to a cellulose template was induced by using nanoprecipitation, in which a DMSOsolution of CT-cellulose was precipitated drop wise into a large amount of water under stirring to form nanoparticles with anaggregation-induced emission effect. Furthermore, due to the biocompatible nature of the CT emission-active material, thecellulose-CT NPs were nontoxic to cells in vitro and could be used for biological imaging.