Htermi nation Otermi nation Hl0

p-type conductive

(Conductive layer thickness <10 nm) (Surface hole concentration -1013 cm 2)

Hydrophobic Negative electron affinity p-type conductive

(Conductive layer thickness <10 nm) (Surface hole concentration -1013 cm 2)

Hydrophobic Negative electron affinity

Insulating

Hydrophilic Positive electron affinity

Figure 8.6. Schematic diagram of the H- and O-terminated (00 1) diamond surfaces and their physical properties. Source: From Ref. 26.

Diamond in Biomedical Applications | 169 "11

Figure 8.7. An X-ray radiogram taken after an implantation of orthopedic screws, coated with NCD film, into a human organism. Source: From Ref. 11.

Figure 8.8. Endoprothesis of a hip joint, coated with NCD film. Source: From Ref. 11.

of preliminary surface studies of it, carried out in Lyon and in Bratislava.

With the development of CVD, diamond coating is an attractive method to improve the cutting performance and tool life. Jackson and coworkers12 used hot filament CVD (HFCVD) technique to coat tungsten carbide (WC-Co) dental burs with diamond film and examined the cutting performance of these dental burs by drilling materials such as borosilicate glass, acrylic teeth, and natural human teeth. Figure 8.9 shows the dental bur drilling machine. Figures 8.10 show that diamond film is uniformly coated onto the cylindrical substrate surface after HFCVD. After drilling human tooth materials, the tooth materials such as dentine clog interstices on the bur, reducing its abrasive performance. The life of the burs was measured by comparing the amount of flank wear of dental bur. Figure 8.10(C) shows that HFCVD diamond bur has the best performance. These experiments show that HFCVD diamond coated dental bur gives longer bur life and a much better quality of drilling and machining.

Catheter ablation is an invasive treatment method for cardiac arrhythmia by thermal destruction of the structures causing arrhythmia. Figure 8.11 shows the sketch of conventional ablation catheter setup and the temperature sensor.13 To improve the accurate measurement and controllability of the temperature so as to control the size of the lesion, Müller and coworkers designed a diamond-based heater system shown in Fig. 8.12.13 Figure 8.13

Figure 8.9. Dental bur drilling machine and air-operated spindle unit attached to the clamping device and driving unit attached to the teeth. Source: From Ref. 12.
Figure 8.10. (A) (111) faceted CVD diamond-coated dental bur. (B) HFCVD diamond-coated dental bur after drilling human tooth materials. (C) Flank wear of burs matching human tooth materials. Source: From Ref. 12.

controller

Figure 8.11. (a) Sketch of a conventional ablation catheter setup. (b) Tip of a conventional ablation catheter with four electrodes and one temperature sensor. Source: From Ref. 13.

controller

Figure 8.11. (a) Sketch of a conventional ablation catheter setup. (b) Tip of a conventional ablation catheter with four electrodes and one temperature sensor. Source: From Ref. 13.

Figure 8.12. (a) Cross-section of the designed heater. (b) Photograph of the test structure. Source: From Ref. 13.
Figure 8.13. (A), (B) dead pig myocardium tissue samples treated with the diamond heater. (C), (D) dead pig myocardium tissue samples treated with a conventional RF ablation catheter. The scales are 0.5mm/div. Source: From Ref. 13.

shows that the diamond heater causes nearly perfect circular lesions with homogeneous depths to the tissue, whereas the conventional catheter (radio frequency (RF) catheter) results in large lesions, which are difficult to control.

IMMOBILIZATION OF BIOMOLECULES

The chemical modification and physical absorption of diamond surface hold promises for diamond to be applied in immobilization of protein and DNA for purification, separation, and further analysis.

Using detonation ND, Bondar and coworkers14 successfully separated recombinant Ca2+-activated photoprotein apoobelin and recombinant luciferase from bacterial cells of Escherichia coli through physical absorption of proteins on ND. For traditional purification by chromatographic means, it usually takes several days. Figure 8.14 shows the procedures using ND. The cells were disrupted through ultrasound and the cell debris was removed by centrifugations. Then suspended detonation ND was added and then centrifuge to separate ND with protein absorbed on it. When treated by a selective block of SH group such as dithiothreitol,

Esciierichii. coli cells containing recombinant proteins concentrated and pure solution of protein cell disruption ^ remove cell ^^ pi X ^-zK jhs

concentrated and pure solution of protein

centrifugation ^

centrifugation ^

centrifugation resuspend sediment

Eppendorf tube

^ recombinant

cell debris

nanodiamond

A solution T contaminant

\ protein

particle

Figure 8.14. Scheme of separation and purification of the recombinant protein from E. coli cells using adsorption of protein onto detonation ND. Source: From Ref. 5.

protein was desorbed from ND. The whole process took 30-40 min with a yield of 35-60%.

Kong and corworker15,16 applied the same principle to capture proteins and DNA for the matrix-assisted laser desorp-tion/ionization (MALDI) time of flight (TOF) mass spectrometry (MS). Carboxylated ND (~100 nm) exhibits high affinity to proteins and polypeptides through hydrophobic and hydrophilic forces. Proteins in very dilute solution can be easily captured by ND and separated and directly analyzed by MALDI-TOF-MS. The sensitivity is enhanced by more than two orders of magnitude. Car-boxylated ND coated with poly-L-lysine was used to form stable complex with DNA oligonucleotides for MALDI-TOF-MS analysis. No-pre-separation of ploy-L-lysine or DNA was necessary prior to MS analysis.

Puzyr' and cowoekers designed a luminescent biochip with nanodiamonds and bacterial luciferase.40 Figure 8.15 shows the structure. It is demonstrated that the enzyme in this structure retains the catalytic activity from recording the luminescent signal. The luminescent intensity is sufficient high for this biochip to be used in bioluminescent analysis.

Aldehyde Luciferase

Aldehyde Luciferase

Figure 8.15. A hypothetical "aluminum oxide film-adhesive layer-nanodiamond-luciferase" supermoleculer structure of the biochip for the components arranged in monolayers. Source: From Ref. 40.

8.4 DRUG DELIVERY VEHICLES

Recently, the uptake of ND by living cell found in the biological ND research facilitated the use of NDs as drug carriers and delivery vehicles. In 1995, Kossovsky and coworkers used ND coated with cellobiose,17 a disaccharide to immobilize mussel adhesive protein (MAP) antigen. Figure 8.16 shows schematic diagram of the structure of diamond-callbiose-MAP. Then the complex was injected into New Zealand white rabbits which have their specificity against MAP. The delivery of antigen caused a strong and specific antibody response. Further experiments showed that ND immobilization

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