Comparison of different DNA preservation solutions for oral cytological samples

Abstract

Objective: The objective of this study was to compare the DNA preservation capacity of buccal mucosa exfoliated cells when stored in different solutions under varying time and temperature conditions.

Design: DNA preservation solutions, including Dimethyl sulphoxide disodium-EDTA-saturated NaCl (DESS), Tris-EDTA-NaCl-Tween20 buffer (TENT), Nucleic Acid Preservation Buffer (NAP), and phosphate-buffered saline (PBS), were prepared. Buccal mucosa cells from a single patient were collected, dispensed into these solutions, and stored at room temperature (RT) and 4 °C for 24 h, 72 h, 30 days, 90 days, and 180 days. DNA was extracted using the salting-out method and the QIAamp DNA Mini Kit. DNA concentration and purity were determined using the QuBit device and NanoDrop, while DNA integrity was assessed using the Agilent 4200 TapeStation system. The ability to amplify the IFNA primer was also evaluated by PCR.

Results: The salting-out method yielded better concentration and purity results, with PBS, TENT, and DESS buffers demonstrating superior concentration values when stored at 4 °C, resulting in mean values exceeding 10 ng/μL for up to 30 days. DESS consistently exhibited the best integrity values over time for both temperature conditions. Amplification capacity was enhanced when samples were stored at 4 °C. When stored at RT, PBS achieved 100% amplification within 24 h. NAP yielded the poorest results.

Conclusion: In the context of long-term preservation, the DESS buffer emerges as the most effective solution, maintaining requisite DNA quality and quantity standards for up to 30 days at RT and up to 3 months at 4 °C.

Keywords: DNA; DNA Preservation Solutions; Molecular Analysis; Oral Cytology; Oral cancer.