The development of novel tunable fluorescent probes whose excitation and emission fall within the spectral region of minimal biological tissue absorption (~650-1450 nm) is needed in order to improve in vivo imaging sensitivity in biological systems. Current limitations of known materials (dyes, quantum dots) include broad emissions and limited photostability. Lanthanide complexes offer significant advantages, including sharp, stable emissions and long-lived luminescent lifetimes, which can enable long-term tracking experiments. To date, only a very limited number of studies are demonstrating their applicability to this field. Here we report the design, synthesis, and characterization of a novel multifunctional MOF materials platform for biomedical applications, that displays both porosity and tunable emission properties, as function of the metal identity (visible to NIR). In this context, Nd ion was deliberately chosen for this study, due to its NIR-emitting properties. Photoluminescence in the NIR has rarely been observed in MOFs, due to the fact that the emission can be easily quenched by solvents and functional groups on the organic ligand. In this investigation, the Nd-based MOF exhibits sharp emission in the NIR at 808 nm excitation, inferring an efficient sensitization of the Nd ions by the organic linker. Importantly, the photoluminescence spectra remains unaltered for the as-synthesized and guest-free samples, demonstrating that the emission is independent of pore environment. A similar behavior was noted for the red-emitting Eu analog, which in addition, has a broad, tunable UV excitation band which peaks at ~368 nm, and narrowband visible excitation peaks at ~464 and 532 nm. Ongoing work is focused on synthesizing nanoparticle analogs, along with determining the biocompatibility of these systems, in order to commence the in vivo biodistribution studies.

Multifunctional MOFs materials platform for biomedical applications

253rd National Meeting (2017)

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