Inhibition of DNA restrictive endonucleases and Taq DNA polymerase by trimalonic acid C60

Screening of fullerene toxicity by hemolysis assay

Fullerene is a compound formed during carbon burst that has been produced synthetically starting from the 1990s. The spherical shape and the characteristic carbon bonds of this allotrope (C(60)) have made it a suitable molecule for many applications. During the last decade, the low aqueous solubility of this molecule has been improved by chemical functionalization allowing the use of fullerene derivatives in biological fluids. The characterization of the toxicity potential of fullerenes is therefore of growing interest for any biomedical application. Intravenous injection is one of the possible routes of their administrations and therefore red blood cells are among the first targets of fullerene cytotoxicity. Human red blood cells are easily available and separated from plasma. Membrane disruption by toxic compounds is easily detected in red blood cells as release of hemoglobin in the cell medium, which can be assayed spectrophotometrically at λ = 415 nm. Due to the high molar extinction coefficient of hemoglobin, the assay can be performed on a small amount of both red blood cells and the test compounds, which might be available only in small quantities. So, the hemolysis assay is a simple screening test, whose results can guide further investigations on cytotoxicity in more complex experimental models.

Inhibition of in vitro amplification of targeted DNA fragment and activity of exonuclease I by a fullerene-oligonucleotide conjugate

Novel biological activities of a fullerene-oligonucleotide conjugate (FONC) were examined in the present report. A new FONC containing a complementary sequence to a specific region of the beta-actin cDNA was synthesized. We found that the FONC at a low concentration (10(-6)M) could specifically inhibit PCR-amplification of the beta-actin cDNA by inhibiting the activities of both Taq DNA polymerase and the cDNA template. This inhibition appeared to be mediated by reactive oxygen species (ROS). The FONC also exhibited the ability of antagonizing the enzymatic activity of an engineered nuclease, exonuclease I (Exo I). Our data provided some valuable evidences on the prospective use of FONC in the antisense strategy for gene silencing.