Micro-patterning for cell culturing is a critical technique for today s bioengineering that has gained increasing attention in recent years. Micro-patterning can be achieved by chemical or physical means. One important way of modifying the interaction between living cells and surfaces of materials conventionally used in biomedical applications is by means of thin coatings: of particular interest to this work is diamondlike carbon films (DLC). Rather than a single material, DLC is best described as a class of materials, typically formed by carbon atoms or carbon and hydrogen atoms in a random network with no long-range order. The properties of these materials cover a broad range of values, and are primarily determined by their chemical composition and bonding configuration. Biocompatibility of DLC has been demonstrated in a series of publications 1-4. DLC can be alloyed with other elements, such as refractory metals, Si, N, F and others. Adding these elements modifies both bulk and surface properties. Bulk properties, such as electrical properties or intrinsic stresses, have a great effect on the performance of the coated part under different operating conditions e.g., external load, temperature and so forth. On the other hand, surface properties determine the interaction between the film and its environment, which is critical, for instance, for cell culturing. An interesting application of DLC in micro-patterning has been recently proposed for the selective growth of neurons 5. Preferential attachment on DLC coated glass slides was demonstrated, as shown in Figure 1. However, cell growth takes place not directly over the deposited DLC, but on a layer of collagen, which lies between the modified surface and the cells. Therefore in order to understand the observation of preferential growth on DLC coated surfaces, it is important to understand the interaction between DLC and the collagen molecules .In this article we discuss the deposition processes of the different types of DLC films on a variety of substrates, and some basic properties of such films. The effect of adding different alloying elements (N, Si, Ti) to the DLC on cell growth is discussed. In this article we also discuss our experiments to test the hypothesis proposed in our earlier publication 5 that the selectivity in cell growth is actually due to differentiation in the collagen films prepared on the treated and untreated surfaces. Atomic force microscopy (AFM) and electron microscopy are used to characterize the collagen morphology on surfaces coated with the different types of DLC and surfaces without any DLC. References: 1. Ohl, A and Shroder, K, Surface and Coatings Technology 116-119, 820-830 (1999). 2. Lettington, A H, Phil. Trans. R. Soc. London Ser. A, 342 287-296 (1993). 3. Dowling, DP et al. Diamond and Related Materials 6, 390-393 (1997). 4. Hauert, R Diamond and Related Materials 12 583-589 (2003) 5. Brown, I G et al. Plasma Phys. Control. Fusion 45 547-554 (2003).

To understand the possible environmental interactions of uranium with the radioresistant bacterium Deinococcus radiodurans we have characterized its sorption complex chemically and spectroscopically. The binding strength, pH sorption edge, selective blocking of cell-surface functional groups, and competition with known complexors support laser fluorescence and infrared spectroscopic data indicating that a carboxyl surface group, consistent with known characteristics of D. radiodurans' S-layer, interacts with and binds the uranium. Although its high survivability in gamma radiation fields has been well studied, the effects of alpha particles from uranium bound to its surface may affect its survivability and interaction with the environment. Using Helium and Nitrogen nuclei cyclotron beams to mimic the effect of typical actinide alpha particles, we explored the ability of D. radiodurans to survive ion irradiation. In addition, a Co-60 gamma source was used to study the effects of environmental conditions on survivability.

Deinococcus radiodurans, a nonpathogenic prokaryote able to withstand high doses of ionizing radiation, is being engineered for bioremediation and biostabilization of heavy metals and actinides. An actinide bioprecipitation system for D. radiodurans capable of polyphosphate accumulation, inducible degradation and secretion, and UO22+ precipitation, is being developed.The radioresistance of D. radiodurans to ionizing gamma radiation has been well studied, yet is not well understood. Several DNA repair mechanisms have been discovered, yet survivability studies are typically done under nutrient-rich conditions at a single growth stage. Although a minimal irradiation medium has been described, the effect of different variables on survivability in a nutrient-starved environment has not been systematically studied. Results indicate that there is a threshold below which the radiation dose is not sufficient to overcome the cells' passive defense mechanisms, such as radical scavenging and constitutive repair proteins. Additional radiation survivability is then from active resistance induced by cell damage, possibly related to aging. The effects of light-ion irradiation in aqueous suspension have also been studied using the 88" cyclotron at the Lawrence Berkeley National Laboratory and increasing lethality corresponding to increasing linear energy transfer (LET) values of the radiation is seen. Previous studies only examined heavy ion effects on cells supported on solid medium.To better understand the sorption chemistry of D. radiodurans, the interaction of strain R1 with UO22+ has been studied. The Gram-negative R1 uranyl sorption load is an order of magnitude less than that of non-engineered Gram-positive Bacillus sphaericus under similar conditions, and more than two orders of magnitude less than a polyphosphate accumulation engineered strain of Gram-negative Pseudomonas aeruginosa. Chemical studies of the cell-uranyl binding strength and pH sorption edges support spectroscopic data indicating that a carboxyl surface group, consistent with known characteristics of D. radiodurans' S-layer, interacts with and binds the uranyl. A strain engineered with the putative polyphosphate accumulation genes shows promise for use in applications of uranyl bioprecipitation and its efficacy and contrast to the non-engineered strain will be discussed.