Diamond standard in diagnostics: nanodiamond biolabels make their mark

Fluorescent defects in non-cytotoxic diamond nanoparticles have recently emerged as a preferred candidate for optical labels in biological and medical imaging. The bright fluorescence at 550-800 nm originates from point defects within the particles, some of which appear naturally, while others can be artificially incorporated during synthesis or can be introduced using high-energy ion beam irradiation and subsequent thermal annealing. However, in order for the fluorescent defects to be useful in bio-medical applications there are a number of materials challenges that must be overcome. In this paper, recent studies on nanodiamonds and their use as biolabels are reviewed, while highlighting the links between the physical, chemical and biological issues that arise.