Schulte, Zachary

• Ph.D., Inorganic/Materials Chemistry, University of Pittsburgh 

• B.S., Chemistry, University of South Dakota

Research in the Schulte Lab will focus on the synthesis and characterization of lanthanide-based metal-organic frameworks (Ln-MOFs) for use in bioimaging applications. Metal-organic frameworks (MOFs) are a class of hybrid organic/inorganic materials composed of metal ions or clusters bridged by coordinating organic ligands. Constructing MOFs with lanthanide ions (Ln3+) combines the luminescent properties of the Ln3+ and the porous, crystalline nature of MOFs. Compared to traditional organic fluorophores, Ln3+ offer several advantages as emitters for bioimaging such as narrow emission peaks, similar reactive chemistries for facile substitutions, and resistance to photobleaching or blinking. By nature of the MOF structure, the large densities of Ln3+ emitters and organic ligands are adjacent to one another in a periodic pattern. This arrangement can enable the "antenna" effect where the chromophoric ligands sensitize the Ln3+ emission, overcoming the low quantum yields that plague direct sensitization of Ln3+. The simple synthesis, interesting photophysical  properties, and impressive thermal and air stability of some Ln-MOFs make them attractive for cellular and biological imaging applications.

While many Ln-MOFs have been investigated for cellular imaging or bioimaging applications, we intend to incorporate several key studies and impart additional controls to our system to develop a robust and versatile technology for imaging applications. Firstly, we will impart morphological controls to produce nanoscale (sub- 100 nm) Ln-MOFs by tuning the synthetic conditions, such as the use of microwave reactors or chemical modulators. The morphological effects on luminescence and dispersion properties will then be thoroughly investigated. Secondly, enhancing the specificity of binding between the Ln-MOF and the target (e.g. bacterial cells or eukaryotic cells) can be achieved by modifying the surface of our MOF nanocrystals. Surface functionalization studies will include previously reported surface-binding compounds such as boronic acid moieties as well as novel antimicrobial compounds produced by the Eichler lab at Augustana University designed to adhere to peptidoglycan layers of bacterial cell membranes. Once surface modifications are made, we will test the binding affinity to various cellular species using fluorescence microscopy. Finally, the luminescent properties will be tuned and characterized by making molecular modifications to functional groups on the organic ligands, thus resulting in variable energy transfer efficiencies.

This project combines aspects of organic, inorganic, physical, and biochemistry, though no particular experience in any of these fields is required. Students involved in this project will have opportunities to create novel MOF compounds and receive hands-on training on advanced instrumentation and characterization techniques, including fluorescence microscopy and spectroscopy, electron microscopy, X-ray diffraction spectroscopy, and nuclear magnetic resonance spectroscopy.