Visualizing the presence and distribution of multiple specific molecular markers within a tumor can reveal the composition of its microenvironment, inform diagnosis, stratify patients, and guide treatment. Raman imaging with...

Rationale: Surface enhanced Raman scattering (SERS) is proving to be a useful tool for biomedical imaging. However, this imaging technique can suffer from poor signal-to-noise ratio, as the complexity of biological tissues can lead to overlapping of Raman bands from tissues and the Raman reporter molecule utilized. Methods: Herein we describe the synthesis of triple bond containing Raman reporters that scatter light in the biological silent window, between 1750 cm -1 and 2750 cm -1 . Results: Our SERS nanoprobes are comprised of uniquely designed Raman reporters containing either alkyne-or cyano-functional groups, enabling them to be readily distinguished from background biological tissue. Conclusion:We identify promising candidates that eventually can be moved forward as Raman reporters in SERS nanoparticles for highly specific contrast-enhanced Raman-based disease or analyte detection in biological applications.

Despite 40 years of interest in chalcogenopyrylium polymethine dyes, significant gaps remain in our understanding of their photophysical properties. These gaps hinder efforts to apply such dyes as photodynamic therapy and/or biomedical sensing agents where a complete understanding of their excited-state dynamics and chemistry are important. For example, despite previous reports that establish singlet oxygen yields as high as 12% for certain dyes, we observe no evidence for 1 O 2 from direct phosphorescence measurements. We now fill in many of these gaps through steady-state and pulsed-laser kinetic experiments on a family of 14 dyes, including six novel dyes, selected to vary physical and electronic structure. These structural changes encompass the selenium and tellurium heteroatoms, phenyl, thiophene, tert-butyl substituents, and methine linker length. Excited-state lifetimes were obtained by femtosecond transient absorption spectroscopy. Lifetimes were all sub-300 ps, suggesting rapid relaxation out of their excited states. Notably, we observed no evidence of any triplet transient processes; phosphorescence was only observed in samples at 77 K. Variable-temperature NMR experiments implicate rotation of the pyran ring about the methine backbone as a critical determinant of the dynamics of these dyes that distinguishes their photophysics from more rigid analogues. Our work establishes that even within the same class of compounds (e.g., pyrylium dyes), properties and reactivities may differ significantly yet the origins of these differences are not apparent from photophysical measurements alone. When combined with studies of structural dynamics, we have obtained a complete structure−function relationship that we can now apply to much broader classes of dyes and serves as a reliable foundation for developing the applications of such species.

Previous reports of chalcogenopyrylium polymethine dyes establish singlet oxygen yields as high as 12%. Our studies of these systems suggested that the current understanding of the excited state dynamics is incomplete. In fact, we observe no evidence for singlet oxygen generation across a range of experiments. We have carried out steady-state and pulsedlaser kinetic experiments on a family of fourteen dyes, including six novel dyes, selected to vary physical and electronic structure. We have changed the identity of the chalcogen between selenium and tellurium heteroatoms, phenyl, thiophene, tert-butyl substituents, and methine linker length. Excited-state lifetimes were obtained by femtosecond transient absorption spectroscopy. Lifetimes were all sub-300 picoseconds, suggesting rapid relaxation. Furthermore, we observed no evidence of any triplet transient processes; phosphorescence was only observed in samples at 77 K. Variable-temperature NMR experiments implicate rotation of the pyran ring about the methine backbone as a critical determinant of the dynamics of these dyes that distinguishes their photophysics from more rigid analogues.

Correction for ‘Multiplexed molecular imaging with surface enhanced resonance Raman scattering nanoprobes reveals immunotherapy response in mice via multichannel image segmentation’ by Chrysafis Andreou et al., Nanoscale Horiz., 2022, 7, 1540–1552, https://doi.org/10.1039/d2nh00331g.