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 red to 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 encapsulate FNDs with mesoporous polydopamine, and demonstrated that this approach enables diverse biological applications including cellular imaging, sensitive siRNA detection at the single-molecule level, and enhanced loading and cellular delivery of the chemotherapeutic agent Doxorubicin. This work extends the functional surface modification approaches available for continued development of FNDs as biological imaging probes. In addition to their remarkable fluorescence properties, the high index of refraction of diamond makes nanodiamonds potentially useful as optical trapping probes. We followed up previous demonstration of optical trapping of FNDs in collaborative work with Professor Michael Woodside in the department of Physics at the University of Alberta Canada. In a recently published study, we demonstrated that nanodiamonds on the order of 300 nm are excellent optical trapping probes that could increase the time resolution to the microsecond scale in optical trapping measurements, which is a substantial increase over the time-resolution achieved with conventional polystyrene or silica optical trapping probes.