Decrease DNA contamination in the laboratories

In this study, we tested various approaches to remove DNA from hard laboratory surfaces. We contaminated clean surfaces with four different concentrations of massively parallel sequencing libraries. The DNA was dried and left for 45 min and for 24 h, respectively, before any treatment. The surfaces were cleaned with six different methods water, 96% ethanol, water followed by 96% ethanol, 3-6% hypochlorite solution, 0.9-1.8% hypochlorite solution, and no treatment. Subsequently, the surfaces were swabbed using cotton. DNA was extracted from the swabs and the DNA concentrations were determined by real-time PCR. The results showed that leaving the DNA traces for 24 h decreased the amount of amplifiable DNA approximately four times. The concentrations of amplifiable DNA were approximately five times lower after cleaning with 96% ethanol. Cleaning with water and water followed by 96% ethanol reduced the amount of amplifiable DNA 100-200 times, whereas cleaning with hypochlorite removed all traces of amplifiable DNA. This indicated that the 'mechanical' cleaning was efficient but cleaning with hypochlorite was superior. In conclusion, it is recommended to clean laboratory surfaces with 0.9-1.8% hypochlorite in order to eliminate laboratory contamination and simultaneously minimise any poisonous gases.