There is an unmet need in the imaging market for bright, photostable reagents that fluoresce in the near-infrared region (NIR) and are also safe for in vivo clinical applications, such as cancer diagnosis and treatment. Fluorescent nanodiamonds meet these requirements and thus offer a better way to identify high-risk individuals, to provide earlier diagnosis before symptoms occur, and to monitor treatment effects. Additionally, there is great interest in using NV-center nanodiamonds for molecular-scale, magnetic resonance imaging (MRI) since they can be used as spin sensors for optically detected NMR.
Part of the emission spectra of NV-center nanodiamonds occurs in the near infrared (NIR) region, making them well-suited for in vivo biomedical imaging. In vivo imaging in the NIR is desirable because autofluorescence from blood components, such as water and metabolites, is lowest in this spectral regime. While some organic fluorescent molecules, such as the FDA-approved indocyanine green, exhibit emission in the NIR window, they suffer from eventual dye quenching, poor solubility, low quantum yield and poor overall in vivo stability. NV-center nanodiamonds overcome these shortcomings by virtue of their non-quenching nature, good dispersion properties, high quantum yield and excellent in vivo stability.
Fluorescent nanodiamonds have novel and unique features that that make them excellent optical probes for in vivo biomedical imaging applications. They are nontoxic and their stable fluorescence can be retested frequently over long periods of time, making them useful probes for bioimaging applications such as real-time dynamic imaging and single molecule tracking applications, and could potentially allow them to replace many commercial fluorescent probes such as quantum dots (QDs) and organic fluorophores.