Boron Dye-PLA Materials for Oxygen Sensing

Many applications benefit from the development of multicolor luminescent materials, such as bioimaging and displays. Optical bioimaging with fluorescent dyes can provide spatial and temporal information of important analytes, such as oxygen. Difluoroboron dibenzoylmethane-poly(lactic acid) (BF2dbmPLA) exhibits both fluorescence (F) and oxygen sensitive room-temperature phosphorescence (RTP). This material has enabled ratiometric oxygen sensing. The fluorescence acts as an internal reference, and the phosphorescence changes intensity based on the oxygen concentration. While BF2dbmPLA has blue fluorescence and green phosphorescence, non-ideal for biomedical applications, its simple structure is a powerful starting point. There are tremendous possibilities for chemically diverse derivatives to optimize the luminescence colors and oxygen sensitivities.
Synthesis of new dyes and polymers was conducted. First, halide substituents on the ligand scaffold proved to be an effective method to tailor the oxygen sensitivity of BF2dbm(X)PLA (X = H, F, Cl, Br, or I). Second, for red-shifted optical properties, a combination of aromatic conjugation and polymer molecular weight was used to synthesize polymers of different luminescence colors. Exploration of different aromatic groups included phenyl, naphthyl, and thienyl substituents. Fluorescence colors range from ~400-550 nm, and phosphorescence colors span ~500-590 nm. Third, synthetic protocols were established to prepare BF2bdk dye-poly(lactic acid)-poly(ethylene glycol) (BF2bdk-PLA-PEG) block copolymers via a Mitsunobu reaction. Finally, polymers were fabricated as nanoparticles for oxygen sensing in cells, tumors and wounds. Synthesis and characterization are discussed.