Recent advances in nanotechnology have increased the development and production of many new nanomaterials with unique characteristics for industrial and biomedical uses. The size of these new nanoparticles (<100 nm) with their high surface area and unusual surface chemistry and reactivity poses unique problems for biological cells and the environment. This paper reviews the current research on the reactivity and interactions of carbon nanoparticles with biological cells in vivo and in vitro, with ultrastructural images demonstrating evidence of human cell cytotoxicity to carbon nanoparticles characteristic of lipid membrane peroxidation, gene down regulation of adhesive proteins, and increased cell death (necrosis, apoptosis), as well as images of nontoxic carbon nanoparticle interactions with human cells. Although it is imperative that nanomaterials be systematically tested for their biocompatibility and safety for industrial and biomedical use, there are now ways to develop and redesign these materials to be less cytotoxic, and even benign to cell systems. With this new opportunity to utilize the unique properties of nanoparticles for research, industry and medicine, there is a responsibility to test and optimize these new nanomaterials early during the development process, to eliminate or ameliorate identified toxic characteristics.

Summary:The bacterial endospores of C. sporogenes ATCC 3584 are quite small (approximately 0.7-1.0 pm in length) and are difficult to examine during the attachment and germination process by conventional light microscopy methods. Although transmission electron microscopy provides high magnification and resolution, it has not been possible to date to visualize the attachment process and surface changes of intact clostridial endospores. With the advent of higher resolution conventional scanning electron microscopes (SEM), it is now possible to study these small spores attached to their nutrient substrate in their intact state and readily obtain detailed morphologic information about the attachment, germination, and outgrowth process. Spores were examined in their dormant, dehydrated state and allowed to germinate. Samples were prepared for light, transmission, and SEM under anaerobic conditions for morphologic and histochemical examination. SEM revealed that the spores developed a distinct polarity at the beginning of the germination process and that the exosporial membrane at this time produced projections that attached the spore to a substrate. These projections were altered by calcium chelation with EDTA and the presence of barium. Following colchicine and cytochalasin B treatment, the exosporial membrane projections were morphologically altered and the germination sequence was modified. Histochemical examination of the spores suggested that calcium was predominantly located in the protoplast and spore coat.

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