A long-wavelength xanthene dye for photoacoustic imaging

Abstract

Photoacoustic (PA) imaging is a powerful biomedical imaging modality. We designed KeTMR and KeJuR, two xanthene-based dyes that were readily obtained through a 2-step synthetic route. KeJuR has low molecular weight, good aqueous solubility, and superior chemical stability compared to KeTMR. KeJuR shows a robust PA signal under 860 nm excitation and can be paired with traditional PA dyes for multiplex imaging in blood samples under a tissue-mimicking environment.

Figure 1.

Structural comparison of previously reported xanthene based fluorescent dyes and the re-purposed PA dyes reported in this work.

Figure 2.

Synthesis of KeTMR.

Figure 3.

Absorbance and Emission Spectra of KeTMR. a) Plot of relative absorbance (red) or emission intensity (dark red) for KeTMR (10 μM, DPBS). Emission intensity is corrected for solvent re-absorption (SI). b) Plot of emission maxima for KeTMR (10 μM) vs. dielectric constant (ε).

Figure 4.

Synthesis of KeJuR.

Figure 5.

Absorbance and Emission Spectra of KeJuR. a) Plot of relative absorbance (red) or emission intensity (dark red) for KeJuR (10 μM, DPBS). Emission intensity is corrected for solvent re-absorption (SI). b) Plot of emission maxima for KeJuR (10 μM) vs. dielectric constant (ε).

Figure 6.

Photoacoustic imaging with Ke-xanthene dyes. a) Plot of relative PA intensity for 50 μM of the indicated dye in DBPS (pH 7.2, 1% DMSO). Data are mean ± S.D. for n = 7 different depths. b) Plot of PA signal (ex: 860 nm) vs. KeJuR concentration. c) 3D reconstruction of PA tomograph of KeJuR (magenta) or ICG (green) in sheep blood within a tissue phantom containing 60% milk. Cross - sections through d) x-y or e) x-z planes show strong PA signal for KeJuR.