Tetrazine- trans-Cyclooctene Chemistry Applied to Fabricate Self-Assembled Fluorescent and Radioactive Nanoparticles for in Vivo Dual Mode Imaging

Multimodal imaging agents combine two or more imaging modalities into one probe. Self-assembling fluorescent nanoparticles are a promising class of modular multimodal imaging probes as they can allow easy blending of imaging and targeting modalities. Our group recently developed a class of self-assembling and intrinsically fluorescent small molecule-based nanoparticles (SMNPs) with excellent optical properties. In this article, we describe the efficient radiolabeling of these SMNPs via a two-step bioconjugation strategy involving the inverse-electron-demand Diels-Alder ligation between a tetrazine (Tz)-tagged radiolabel and a trans-cyclooctene (TCO)-tagged fluorescent small molecule building block of the SMNPs. Studies in mice revealed that the SMNPs are well tolerated and could be monitored by both radioactivity and fluorescence, thereby demonstrating the potential of SMNPs in optical and dual-mode imaging in vivo. The work also testifies to the utility of the Tz-TCO conjugation chemistry for the labeling of self-assembled nanoparticles.

Easily Processable Temperature-Responsive Infrared-Reflective Polymer Coatings

A temperature-responsive near-infrared reflective coating was fabricated based on a side-chain liquid crystal siloxane polymer using a simple wired-bar method. The cholesteric liquid crystalline polymer film showed a blue shift of the reflection band of ∼1000 nm in the IR region upon heating. The temperature-responsive change of the reflection band was reversible. Compared to that of the same mixture system in an alignment cell, the coating showed a significantly faster response. This research demonstrates an easy way to prepare a temperature-responsive IR-reflective coating that shifts its reflection to a shorter wavelength upon heating. As IR radiation of shorter wavelengths is more strongly represented in sunlight than longer wavelengths, this coating could be used to selectively reduce heating of an indoor space when the temperature is high. This is promising for the future application of smart climate control.