March 15, 2013 (Vol. 33, No. 6)
Charles A. Lunn, Ph.D.
Economic realities have made the drug discovery process an increasingly intricate, daunting, and financially risky enterprise. Advances in our understanding of disease processes have allowed scientists to design discovery campaigns tackling complex diseases. However, scientists are under increasing financial pressure to carry out these experiments in a cost-effective way.
Pharmaceutical companies are investigating the benefit of outsourcing target validation to the academic and biotechnology community to decrease costs. The industry is also making more use of contract research organizations to perform standard in vitro and in vivo assay systems, a tactic designed to improve flexibility and to decrease manpower costs. All aspects of the research expenditure environment are being examined to identify strategies that increase financial efficiency in the short term and, over the long term, improve the return on investment.
Current Liquid-Handling Hurdles
A major expense in the current drug discovery campaigns and an increasing concern in genomics and proteomics research is the utilization of single-use consumable plastic products. Many in vitro biochemical assays and screening programs are carried out in multiwell assay plates for simultaneous evaluation of compounds under identical experimental conditions. The single-use plastic ware provides confidence in there being minimal sample carryover, but the ongoing expense is a major concern.
Robotic liquid-handling systems with disposable pipette tips are the generally accepted paradigm used to perform these experiments. However, disposable tips and the related storage and disposal costs can add hundreds of thousands of dollars to research spending annually per liquid handler. As an alternative to disposable tips, investigators have used single-volume pin tools as a liquid-handling solution.
The down side of using pin tools is the high replacement cost when pins are damaged, and the multistep pin-cleaning process consumes time and generates liters of liquid biohazardous waste daily. A second alternative is to use an acoustic dispenser, but high initial capital investment and liquid-handling limitations have narrowed its applications. Figure 1 shows a snapshot of the single-use consumables.
Renewing Lab Consumables
As a strategy to decrease the high cost of laboratory consumables, cold plasma has been suggested as a decontaminating agent that allows the reuse of plastic products without an effect on assay robustness or reproducibility. Cold plasma can be generated by applying a high frequency (~7 KHz), high voltage (~5 kV) electric current across an air gap between two ceramic dielectric barriers. The ensuing discharge causes avalanching ionization of the air within the gap, resulting in the formation of ionized and activated gas molecules present in air. The ionized plasma species chemically decompose organic and biological molecules, forming nonhazardous gaseous species like CO2 and NO2.
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.
Figure 3 shows that standard aqueous cleaning protocols were insufficient to remove residual DNA at all concentrations tested. In contrast, cold plasma cleaning was sufficient to remove detectible DNA at all concentrations—washing plus cold plasma cleaning does not appear significantly better than cold plasma cleaning alone.
The University of Edinburgh SynthSys lab routinely uses the 8-channel TipCharger system as part of a high-throughput qPCR protocol in 384-well format, where thousands of plates are being processed each week. The ability of cold plasma cleaning to eliminate contaminants is becoming increasingly important with the emergence of DNA-based molecular diagnostics, where minor contaminants may significantly impact the outcome of the investigations.
Cutting Pipette Tip Costs by 90%
The cold plasma technology embodied in the TipCharger system decreases the research expenditure by cutting laboratory consumable pipette tip costs by 90% per year. Cold plasma cleans pipette tips and pin tools by removing contaminants such as nucleic acids, small molecules, complete organisms, and cellular debris—with the TipCharger Plasma Cleaning System, researchers can expect to reuse disposable pipette tips 10 times without sacrificing data quality.
The TipCharger system has been integrated with many liquid-handling platforms including Tecan EVO Freedom, Beckman Coulter Biomek FX, PerkinElmer Sciclone, Hamilton Star, Cybio CyBiWell, and Agilent Automations Bravo. The “plug-and-go” integration requires no programming interface but simply adding a plasma-cleaning protocol to existing liquid-handling routines, allowing the TipCharger system to be productive with minimal setup time. To date, cold plasma cleaning systems have been in use for as long as seven years with no change in cleaning efficiency. A simple and robust solution to the high liquid-handling consumable cost, the cold plasma technology offers significant economic benefits to research labs large or small.
Charles A. Lunn, Ph.D., is a scientific adviser and Jean Shieh (email@example.com) is a marketing director at IonField Systems. Trademarks mentioned are owned by the respective companies.