Green fluorescent nanodiamond conjugates and their possible applications for biosensing

Various nanoparticles play a prominent role in modern biosciences and medicine. Especially fluorescent cellular biomarkers are a prospective material for diagnostics and therapy. Nevertheless, most of the available biomarkers have some drawbacks due to either physical and optical or cytotoxic properties. Here we investigated the potential of green fluorescent nanodiamonds as extra- and intracellular biomarkers for living cells. We characterized the structure of the used detonation synthesized nanodiamonds (DND) by X-ray diffraction (XRD) and the optical properties by fluorescence and infrared spectroscopy. For the extracellular attachment the nanodiamonds were functionalized by attaching antibodies that target extracellular structures such as membrane. Transfections were mediated by dendrimers, cationic liposomes and protamine sulfate. Using fluorescence microscopy, we confirmed successful extracellular binding on and transfection of the nanodiamonds into prostate cancer cells. Furthermore, nanodiamonds can be targeted selectively to intracellular structures. Therefore, nanodiamonds are a promising tool for biosensing.