The TipCharger Plasma Treatment System (IonField Systems) uses ionized cold plasma to clean pipette tips and pins in 8-, 96-, or 384-channel configuration. As shown in Figure 2, contaminated tips are positioned into the TipCharger system by a robotic liquid-handling system. Plasma generation starts when an optical sensor is triggered as tips are inserted into the chamber. The resulting ionized gas is simultaneously drawn into the tips, exposing the contaminated surfaces to plasma. Exposure to the electric plasma discharge for less than 30 seconds is sufficient to remove organic contaminants from pipette tips. After the plasma treatment, pipette tips are ready for immediate reuse.
Investigators at Novartis Institutes for Biomedical Research recently published on their evaluation of the TipCharger system. Using calcium mobilization assays and cAMP assays, Akhlaq and colleagues showed that plasma cleaning removed lysophosphatidic acid and iloprost from polypropylene tips used in signal transduction experiments. In a bacterial decontamination experiment, water wash followed by a TipCharger cleaning protocol was able to completely remove detectible E. coli DH5 alpha from the tips. Akhlaq showed that cold plasma cleaning was also able to remove plasmid DNA from pipette tips—no trace of nucleic acid was detected from contaminated tips by the 7900HT Fast Real-Time PCR system (Life Technologies). The TipCharger system offered Novartis researchers financial savings and a reduction in the laboratory’s environmental impact while maintaining the high level of data quality.
Cold plasma cleaning proved to be particularly effective in eliminating DNA from instruments used in highly amplified quantitative DNA sequence analysis. The University of Pennsylvania DNA Sequencing Facility confirmed this fact using quantitative PCR. After generating a standard qPCR dose-response curve, scientists used the DNA-contaminated tips to pipette water into fresh reactions with and without cleaning.