ANSWERS The falsely high leukocyte count obtained with the hemo-cytometer was caused by treatment with Depocyte. This drug is a slow-release formulation of cytarabine encapsulated into liposomes that maintains the drug in the CSF for more than 14 days after injection (1). Cytarabine lipo-somes are spherules with a granular interior similar in appearance to leukocytes. Liposomes can be differentiated from leukocytes because the former vary in size (3-30 m) and have one or more inclusions (2).

We have synthesized two novel phosphoramidites with a ferrocenyl moiety at the 2'-ribose position linked through a butoxy linker. Using automated DNA/RNA synthesis techniques, oligonucleotides containing ferrocene at various positions were prepared and characterized by HPLC, MALDI-TOF mass spectrometry, and electrochemistry. Thermal stability studies of the ferrocene-modified DNA duplexes revealed that introduction of one or two ferrocenyl complexes does not result in an observed change of the T(m) values of the corresponding DNA duplexes when compared to the nonmodified hybrids. These data indicate that the introduction of a ferrocenyl group at the 2'-position of the ribose ring containing either a purine or pyrimidine base has no effect on the stability of the modified DNA. The electrochemical behavior of the ferrocene-containing DNA was examined by cyclic voltammetry. The modified 2'-ferrocene-oligonucleotides are electrochemically active and can be used as signaling probes for the electronic detection of nucleic acids on bioelectronic sensors.

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Electrically conductive hydrogels incorporated with CNTs support PC12 cell growth and differentiation and hold promise for nerve regeneration.