The Response of HeLa Cells to Fluorescent NanoDiamond Uptake.

Fluorescent nanodiamonds are promising probes for nanoscale magnetic resonance measurements. Their physical properties predict them to have particularly useful applications in intracellular analysis. Before using them in intracellular experiments however, it should be clear whether diamond particles influence cell biology. While cytotoxicity has already been ruled out in previous studies, we consider the non-fatal influence of fluorescent nanodiamonds on the formation of reactive oxygen species (an important stress indicator and potential target for intracellular sensing) for the first time. We investigated the influence of different sizes, shapes and concentrations of nanodiamonds on the genetic and protein level involved in oxidative stress-related pathways of the HeLa cell, an important model cell line in research. The changes in viability of the cells and the difference in intracellular levels of free radicals, after diamond uptake, are surprisingly small. At lower diamond concentrations, the cellular metabolism cannot be distinguished from that of untreated cells. This research supports the claims of non-toxicity and includes less obvious non-fatal responses. Finally, we give a handhold concerning the diamond concentration and size to use for non-toxic, intracellular measurements in favour of (cancer) research in HeLa cells.

Paraoxonase polymorphism in rabbits.

Paraoxonase in serum and liver of rabbits and cattle was investigated. In serum the two substrates paraoxon and phenylacetate are exclusively hydrolyzed by alpha-lipoprotein-bound paraoxonase. In rabbit liver paraoxon is hydrolyzed only by paraoxonase, while phenylacetate is hydrolyzed by paraoxonase (20%) and additionally by an organophosphate sensitive carboxylesterase (B-Esterase), which is responsible for 80% of total liver phenylacetate hydrolysis. Phenyl acetate hydrolysis by B-Esterase of rabbit liver was shown to be inhibited by paraoxon and by mipafox covalently in a time and concentration dependent manner. Rabbit serum exhibits by far the highest serum paraoxonase activity (2.6 +/- 0.66 U/ml) of all vertebrate species tested up to now, while rabbit liver contains only 0.5 +/- 0.2 U/g fresh weight. In cattle extremely high paraoxonase activity is found in liver (2.8 U/g), while bovine serum contains only 0.2 U/g. The paraoxonase activity ratio (hydrolysis rate paraoxon: phenylacetate x 1000) in cattle does not show interindividual variation (activity ratio 4.0 +/- 0.4, correlation coefficient 0.996, P < 0.001). In contrast, the paraoxon/phenylacetate hydrolysis ratio of rabbit paraoxonase in serum as well as in liver does vary considerably between individuals. In cross-bred rabbits paraoxonase activity ratios from three to ten are found. In a strain of pure-bred New Zealand White rabbits three polymorphic serum paraoxonase phenotypes could be clearly differentiated by the activity ratio. By analogy with the human paraoxonase polymorphism, the rabbit paraoxonase isotypes were classified as paraoxonase A (activity ratio 3.8-4.3), AB (ratio 5.5-6.0) and B (ratio 7.3-8.6). The corresponding frequencies of the three isotypes were 40, 35 and 25%.