Saliva is a biofluid, which constitutes a source of biomarkers to be considered a non-invasive and, therefore more acceptable by patients. Techniques of biology molecular, such as PCR and sequencing, have been frequently optimized in saliva to improve microorganism's analysis. Considering the cost of sequencing and genotyping in saliva has decreased in recent years, these techniques have contributed to the diagnosis of diseases and disorders. Guanidine hydrochloride and thiocyanate are powerful agents at purification and detection of nucleic acids (DNA and RNA). These compounds inhibit nuclease activities and promote cell lysis. However, guanidine hydrochloride has appeared to be less effective than guanidine thiocyanate with respect to RNase inhibition. Once little is known about the influence of guanidine salts on the stability of DNA in saliva, the aim of this study is to evaluate the stability of genomic DNA (gDNA), observing how long after thawing is possible to maintain the properties of the nucleic acid intact and if guanidine thiocyanate is able to prolong this stability. Saliva samples of volunteers attending at Dentistry undergraduation course will be used for gDNA extraction, which will be followed by nucleic acid quantification by real time PCR.
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