RESUMO
Protecting RNA from degradation, whilst maintaining its biological activity, is essential in molecular biology. However, RNA is very sensitive to degradation by ribonucleases, especially at temperatures above 0 degrees C. The stability of RNA was examined at 4 degrees C and -20 degrees C, in a new stabilizing solution consisting of a low-molarity mixture of chaotropic agents guanidinium and ammonium thiocyanate, a buffer for pH stabilization, phenol, and yeast RNA. Two substrates were tested for storage: RNA in human plasma positive for hepatitis C virus (HCV) and naked RNA (purified from HCV positive human plasma or transcribed in vitro). Stability was followed by viral load estimation, using an in-house competitive RT-PCR assay. Naked RNA purified from human plasma positive for HCV was stable at 4 degrees C for at least 24 months. An RNA standard transcribed in vitro was still viable after 36 months of storage at 4 degrees C. Human plasma dilutions positive for HCV were stable for at least 5 months in this solution when stored at 4 degrees C. It was concluded that the described stabilizing solution ensures long-term stability on naked RNA at 4 degrees C, and ideal for the storage of RNA controls and standards for molecular diagnosis, the solution may be used for preserving clinical samples prior to transport to a clinical laboratory.
