ABSTRACT
Carbon materials possess excellent mechanical, tribological, and biological properties, and as a result, carbon-based materials Šnd applications in biomedical devices including cardiovascular, orthopedic, and dental applications [1-3]. Pyrolytic graphite (PG) and other
CONTENTS
Introduction ................................................................................................................................. 111 Methods of Synthesis of Various Carbon-Based Materials ................................................... 112
Pyrolytic Graphite .................................................................................................................. 112 Highly Oriented PG ............................................................................................................... 113 Glassy Carbon ......................................................................................................................... 114 Carbon Fibers .......................................................................................................................... 114 Carbon Black ........................................................................................................................... 114 Carbon Film............................................................................................................................. 115 Diamond-Like Carbon ........................................................................................................... 115 Carbon Nanotubes ................................................................................................................. 115 Fullerenes ................................................................................................................................ 116 Graphene ................................................................................................................................. 116
Biomedical Applications of Carbon-Based Materials ........................................................... 117 Biomedical Utility of CNTs ................................................................................................... 117
CNTs for Therapeutic Applications ................................................................................ 117 CNTs and Their Related Cellular Uptake ...................................................................... 118 CNTs for Drug Delivery ................................................................................................... 119
Biomedical Utility of Diamond ............................................................................................ 120 Diamond for Orthopedic Applications .......................................................................... 121 Diamond for Cardiovascular Applications.................................................................... 121 DLC-Coated Guide Wires ................................................................................................ 122 Other Biomedical Applications of Diamond ................................................................. 122
Biomedical Applications of Fullerenes ................................................................................ 123 Functionalized Fullerenes as Drug Delivery Agents .................................................... 123 Suppression of Reactive Oxygen Species by Functionalized Fullerenes ................... 124 Functionalized Fullerenes as MRI Contrast Agents ..................................................... 125 Other Important Applications of Functionalized Fullerenes ...................................... 127
Acknowledgment ........................................................................................................................ 127 References ..................................................................................................................................... 127
forms of carbon coatings such as carbon nanotubes (CNTs), fullerenes, and diamond-like carbon (DLC) in its pure, hydrogenated, and doped forms [4, 5] have raised much interest as potential wear-resistant coatings for biomedical applications because of their attractive properties such as high hardness, high chemical inertness, and low-friction coefŠcient [6, 7]. Furthermore, carbon is widely used as a common electrode material in a great deal of electrochemical detection of biologically signiŠcant species. Usually, carbon materials are characterized by properties such as wide potential window, low background current, fast electron transfer rate, and stability. In electroanalytical chemistry, the carbon materials used are all sp2 hybridized, as these sp2 hybridized carbons are highly reactive and prone to required surface modiŠcation with ease. All these foretold carbon materials have identical C-C bonding but different bulk properties as a result of orientation and size of carbon crystallites. Carbon material possesses structural variables such as the intraplanar carbon-carbon bond distance, intraplanar carbon crystallite size (La), interplanar microcrystallite size (Lc), and the interplanar spacing as shown in Figure 3.1. Of these, the intraplanar C-C bond distance is estimated to be 1.42 Å [8]. La of the carbon crystallite is deŠned as the average size of the graphitic crystallite, and it can vary between 2 and 105 Å. The intraplanar size can be measured using x-ray diffraction technique [8]. A perfect single crystal of graphite has a larger La value. On the other hand, Lc is the distance perpendicular to the plane of the graphite sheet, which is usually 2.46 Å, and it can be increased by heating the carbon materials above 2000°C. Neutron scattering can also be used to measure the intraplanar spacing. For single crystal graphite, the intraplanar spacing value is 3.354 Å [9, 10], and for less ordered sp2 carbon material, the intraplanar spacing value is 3.6 Å. Synthesis of various carbon materials such as PG, carbon Šber (CF), DLC, CNTs, fullerenes, and graphene is brie£y described below.
