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

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

15.3.4 Biocompatibility of Fluorocarbon Polymer

Fluoropassivated carbon polymers and coatings are among the most hydrophobic surfaces known, and are widely employed in “non-stick” applications. They are also extremely chemically inert. In the nanomedical context, polymeric fluorocarbons have already been suggested as in vivo message carriers (Section 7.2.1.1) and for nanocomputer memory tape (Section 10.2.1). Fluoropassivated diamond has been mentioned in the earlier discussions of in vivo nano-morcellation tools (Section 9.3.5.1) and surface data storage (Section 10.2.1), and could in theory be useful at the exterior surfaces of medical nanorobots or as a coating for internal nanofluidics channels. The biocompatibility of low-n fluorocarbons was briefly reviewed in Section 7.2.1.1 (e.g., some potential for liver damage [6204] but generally low-toxicity [6217]; clearance rates decrease as n increases [6205], though triglyceride accumulation induced by perfluorinated fatty acids appears concentration-dependent regardless of chain length [6206]). We now extend this analysis to longer-chain fluorocarbons.

Polytetrafluoroethylene (PTFE), a form of Teflon [1310], is perhaps the most common medical polymeric fluorocarbon [1311]. Commercial Teflon is a packed vinyl polymer, lacking a rigid 2D graphitic or 3D diamondoid crystalline structure. Many different kinds of Teflon are or have been in widespread use, including particulate pastes [1312, 1313], surface films [1314, 1315], wire coatings [1316, 1317], fiber sutures [1157-1159], yarns [1169], microporous membranes [1166-1172] (e.g., Biopore [1193]), high-porosity grafts [1318], multifilament mesh [1194-1196] or textile Teflons [1319], felts [1157], sponges [1158], foils [1164, 1165], sheets [1201-1206], expanded Teflon or e-PTFE (e.g., Gore-Tex [1190-1194]), denucleated e-PTFE or dePTFE [1680], and dense masses, tablets, or disks [1179-1190]. Completely fluorinated surfaces exhibit very low intermolecular forces [858]. The coefficient of friction of Teflon in air is 0.05-0.1, about the same as diamond [1320]. Teflon bulk density is ~2130 kg/m³ [1322].

Teflon in bulk is relatively bioinert. In this Section we review what is known about protein adsorption on Teflon surfaces (Section 15.3.4.1), cell and tissue responses to bulk Teflon (Section 15.3.4.2), the biocompatibility of Teflon-coated prostheses (Section 15.3.4.3), the biocompatibility of fluorocarbon and Teflon particles (Section 15.3.4.4), and the chemical inertness of Teflon (Section 15.3.4.5). But the biocompatibility of atomically smooth fluorocarbon polymer or fluoropassivated diamond surfaces (possibly of greatest relevance in nanomedical applications) has yet to be seriously investigated experimentally, so the results described here can only be regarded as suggestive.

E. Pinkhassik notes that “one can imagine an interesting material produced by the addition of fluorine to the double bonds of fullerenes. The material will be quite different from Teflon and fluorinated diamond. This monomolecular 2D material may be useful in the construction of nanodevices. So far, the methods for the complete fluorination of C₆₀ have not been developed but [as of late 2002] there are at least two groups working on it (Jamie L. Adcock [5866, 5867] at University of Tennessee, Knoxville, and Benjamin T. King [5868] at University of Nevada, Reno).”

Last updated on 30 April 2004