Nanodiamond Particles: Properties and Perspectives for Bioapplications

Nanodiamonds (NDs) are members of the diverse structural family of nanocarbons that includes many varieties based on synthesis conditions, post-synthesis processes, and modifications. First studied in detail beginning in the 1960s in Russia, NDs have now gained world-wide attention due to their inexpensive large-scale synthesis based on the detonation of carbon-containing explosives, small primary particle size (∼ 4 to 5 nm) with narrow size distribution, facile surface functionalization including bio-conjugation, as well as high biocompatibility. It is anticipated that the attractive properties of NDs will be exploited for the development of therapeutic agents for diagnostic probes, delivery vehicles, gene therapy, anti-viral and anti-bacterial treatments, tissue scaffolds, and novel medical devices such as nanorobots. Additionally, biotechnology applications have shown the prospective use of NDs for bioanalytical purposes, such as protein purification or fluorescent biolabeling. This review critically examines the use of NDs for biomedical applications based on type (i.e., high-pressure high-temperature [HPHT], CVD diamond, detonation ND [DND]), post-synthesis processing and modifications, and resultant properties including bio-interfacing. The discussion focuses on nanodiamond material in the form of nanoparticles, while the biomedical uses of nanodiamond coatings and thin films are discussed rather briefly. Specific use of NDs in both non-conjugated and conjugated forms as enterosorbents or solid phase carriers for small molecules including lysozyme, vaccines, and drugs is also considered. The use of NDs as human anti-cancer agents and in health care products is already showing promising results for further development. The review concludes with a look to the future directions and challenges involved in maximizing the potential of these exciting little carbon-based gems in the fields of engineering, medicine, and biotechnology.