Development and characterization of optical imaging probes

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Currently, there is one overarching project focused on functionalizing and characterizing fluorescent nanodiamonds: We are working on functionalizing and characterizing nitrogen vacancy center fluorescent nanodiamonds (FNDs) for use as multi-modal imaging probes. These are attractive fluorescence particles for in vivo and in vitro tracking and imaging studies as they are bright, non-blinking fluorophores that are excited in the green (560 nm) and emit in the far red spectrum (680-800 nm), which has superior tissue penetration and signal-to-noise characteristics compared with shorter wavelengths. Moreover, diamond is inert and the fluorescence arises from the nitrogen vacancy so the core particle contains no organic dyes or other potentially toxic material that would be problematic for in vivo applications. Remarkably, the FNDs can be as small as 10 nm, which is also advantageous for biocompatibility and clearing. We have established protocols to functionalize FNDs for biomedical applications. We recently published work describing methods to enhance the density of carboxylic acid groups on the surface of FNDs, and demonstrated that this approach enables the robust functionalization of FNDS with more than 10 different biologically important functional groups. This work provides a means of overcoming the inherent variability and inhomogeneity in the surface properties of FNDs and other carbon nanoparticles. Following up on our work developing FNDs as biocompatible multimodal probes for the development and detection of latent fingerprints, we worked with our collaborator, Junsang Cho, in the Department of Chemistry, Duksung Women's University, South Korea, to develop highly stanble cesium lead bromide perovskite nanocrystals as fluorescent probes for the detection of latent fingerprints. Work is continuing to expand the functionalization of the FNDs to produce multi-modal particles that can serves as both targeted fluorescent nanoparticles and drug delivery agents employing a novel mesoporous polydopamine encapsulation approach. Using a recently developed micro-mirror TIRF microscope combined with a magnetic tweezers, we developed a method to simultaneously determine the size and brightness of individual FNDs in a massively parallel measurement. This is an important measurement for the characterization of FNDs that has previously been exceedingly low throughput. This new approach allow affords us the opportunity to simultaneously measure the magnetic response of individual FNDs as a function of their size and brightness.