Molecular Probes for Vibrational Imaging of Cellular Targets: Ions and Reactive Species

With support from the Chemical Measurement and Imaging (CMI) and Chemical Structure, Dynamics, and Mechanisms B (CSDM-B) programs in the Division of Chemistry, Professor Daniela Buccella and her research group at New York University are working to develop responsive molecular probes to investigate intracellular targets based on a technique called Raman spectroscopy. Microscopy techniques are ubiquitous tools in the study of biological analytes, allowing the detection of metal ions and reactive species in cells and tissues with high spatial and temporal resolution.

The ability to track these species in real time is key to gaining insight on their roles in physiological and pathological processes. Raman-based microscopy has become increasingly valuable in this context, providing numerous advantages over conventional fluorescence microscopy techniques. An important drawback, however, is the low sensitivity and specificity of vibrational-based detection, for which many small and low abundance cellular targets still remain out of reach.

To address this gap, this project seeks to develop novel indicators that are responsive to metal ions and reactive species, with the goal of imaging these species using a Raman technique to which they are currently invisible. This award also supports a partnership with faculty at Spelman College for the development of new laboratory and lecture modules that integrate chemistry and biology into a new capstone research course at Spelman.

This project focuses on establishing basic molecular platforms with Raman scattering properties that can be modulated in an analyte-dependent fashion. The work enables new vibrational imaging probes for stimulated Raman scattering (SRS) microscopy. The designed scaffolds take advantage of charge redistribution and modulation of electronic excited states to enable SRS- and electronic pre-resonance-SRS-based imaging of low abundance and transient cellular species that have small scattering cross sections of their own.

Specific objectives include the development of recognition-based synthetic indicators for detecting biologically relevant metal ions and sensing pH, as well as reaction-based probes for sensing reactive oxygen species. The indicators are being applied toward turn-on and ratiometric detection modalities in cellulo, which have been particularly difficult to achieve for species that quench fluorescence, and therefore continue to pose a major challenge in bioimaging.

In addition to the broader scientific impacts of the work, the project includes educational outreach activities targeting high school girls and college students.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.