Synthesis and Characterization of Surface Functionalized Nanoscale Ln3+-based Metal-Organic Frameworks for Biological Imaging Applications — 73p — Ryan Schulte

Studying intercellular interactions in biological systems is difficult due to the variety of cellular processes and number of cells engaging in complex communications with one another. Cellular imaging is an essential tool for visualizing, identifying, and characterizing cells in a constrained system under similar conditions to their native environments. Multiplexing experiments using molecular fluorophores as fluorescent labels can be challenging due to photobleaching, small Stokes shifts, and broad emission profiles. Lanthanide ions (Ln³⁺) are an enticing alternative due to their narrow emission peaks, similar reactive chemistries, and consistent fluorescence intensities. Herein, we describe our work to develop a palette of lanthanide-based fluorescent biomarkers based on Ln³⁺ metal-organic frameworks (Ln-MOFs). MOFs are an ideal platform for this application due to their high concentration of fluorescent emitters, protective coordinative environments to prevent quenching, and tailorable structural and fluorescent properties. Using MOF-76 (Ln³⁺(BTC)(H₂O)_1.5, BTC = trimesic acid) as a model, we have synthesized Yb, Eu, and Tb nanoscale crystallites. An advantage of this system is that all three fluorophores excite at the same wavelength due to the antenna effect but each have unique emission profiles across the visible and NIR regions. Furthermore, we functionalize the exterior of the MOFs with boronic acid moieties, which show a strong interaction between the peptidoglycan layer of bacterial cells. We utilize fluorescence microscopy to monitor the interactions between several different bacteria and Ln-MOFs for multiplexing studies.

Augustana University
Dr. Zachary Schulte