© 2003 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume IIA: Biocompatibility, Landes Bioscience, Georgetown, TX, 2003

15.3.1.5 Chemical Inertness of Diamond

A major benefit of diamondoid surfaces on medical nanorobots is that such surfaces should be extremely inert against attack by chemical substances at concentrations likely to be found inside the human body (Section 9.3.5.3.6). For example, in one study of a possible diamond-coated total hip replacement material [609], 0.2- to 10-micron thick amorphous diamond (DLC) deposited on stainless steel alloys was found, after lengthy exposure to 10% HCl, to have corrosion rates reduced by a factor of ~15,000 compared to uncoated surfaces (see Section 15.3.3.6). No significant damage to the coatings was observed after 6 months. The Phytis diamond-like coated stainless steel stents showed almost zero release of chromium and nickel ions after 44-hour immersion in 1N HCl [626]. Diamondized stents incubated over 96 hours at 37 ^oC in human plasma released no detectable metal ions (e.g., nickel, chromium, molybdenum and manganese), as determined by Atomic Adsorption Spectroscopy (AAS) or by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) [626]. Diamond-like carbon and diamond are both insoluble in reagents that dissolve graphite and other polymeric carbon structures [599].

While diamond is believed to be very inert in tissues, further studies of bulk and particulate diamond biocompatibility with various tissues and organs are probably warranted, to supplement the traditional ADME and toxicology studies that the pharmaceutical industry might ordinarily consider in designing a clinical study for a new nanorobot.

Of course, medical nanorobot exteriors, while consisting mostly of diamondoid surfaces, may include various other materials (Section 15.3.6). The biocompatibility of internal nanorobot components and crush fragments of destroyed medical nanorobots is briefly addressed in Section 15.4.4.

Last updated on 30 April 2004