Difluoroboron β-diketonate poly(lactic acid) materials exhibit both fluorescence (F) and oxygen sensitive, room-temperature phosphorescence (RTP). These materials enabled ratiometric oxygen sensing from a single component material, without limitations in excitation (1 or 2-photon), dye/matrix leaching or photobleaching. Multidisciplinary efforts in theoretical quantum chemistry, polymeric materials, and biomedical engineering were critical to the design of these functional materials. In this work, an unsymmetrical naphthyl-phenyl β-diketonate ligand was used to induce intramolecular charge transfer (ICT) in a boron complex to modulate the dual emissive properties. Introduction of halide substituents (Br and I) was an effective strategy to enhance the phosphorescence via the heavy atom effect, thus controlling the RTP intensity, lifetime and oxygen sensitivity. Boron dye initiators were prepared for the polymerization of DL-lactide to yield single component dye-PLA conjugates, BF2nbm(X)PLA (X = H, Br and I). The dye-PLA materials were fabricated as nanoparticles, suitable for topical application or 3D printing. The iodo derivative, BF2nbm(I)PLA, showed excellent F to RTP peak separation and a 0-100% oxygen sensitivity range unprecedented for metal-free RTP emitting materials. To demonstrate the prospects of this material design for bioimaging, BF2nbm(I)PLA nanoparticles were applied to a murine wound model to detect oxygen levels. Surprisingly, wound oxygen imaging with good contrast was achieved without covering (i.e. without isolating from ambient conditions, air). Additionally, would healing was monitored via wound size reduction and associated oxygen recovery, from hypoxic to normoxic tissue. These single-component materials provide a simple tunable platform for biological oxygen sensing that can spatially and temporally resolve oxygen levels in a variety of environments.

Difluoroboron β-diketonate polylactides as luminescent oxygen sensing materials for wound imaging

253rd National Meeting (2017)

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