Plastic Lab Equipment May Be Distorting Research Results

By Nina Bai | November 7, 2008 1:10 pm

tubesThe standard lab equipment used by scientists to study subtle chemical reactions and examine biological processes may be compromising their results. A new study found that disposable plastic tubes, pipette tips, and culture plates contain compounds that can leach into common solvents. The study is the first to show how thousands of scientists worldwide may be unwittingly contaminating their experiments with plastic lab equipment. “People are clearly aware that plastics can cause problems. Quite remarkably, nobody appears to have done what we were forced to do,” says co-author Andrew Holt [New Scientist].

Holt was studying the effect of drugs on the enzyme monoamine oxidase B (MAO-B) when he noticed strange fluctuations in the results. “We were banging our head against the wall. Finally, we realized that the plastics must be involved in the issue” [Bloomberg]. Holt washed out his equipment with water, methanol or dimethylsulphoxide (DMSO), then analysed what chemicals had leached into the solvents using mass spectrometry. Reporting in Science, Holt and his colleagues show that the plastic tubes they were using were leaching the disinfectant di(2-hydroxyethyl)methyldodecylammonium (DiHEMDA) into water and the lubricant oleamide into methanol and DMSO [Nature News]. Though the amount of leaching varies, some of the plastic equipment produced contaminant concentrations of several hundred parts per million. “The compounds that leached out of the plastic were remarkably potent inhibitors,” [said Holt]. “We were getting variability caused by these leachates that could completely mask the effects of the drugs” [Nature News].

Many of the chemicals are added during the manufacturing of the plastic equipment to create helpful properties. The additives are used to prevent static buildup, reduce stickiness and eliminate bacterial colonization. But many have been shown to interact with proteins, and to leach from food containers into their contents. [Wired Science]. The enzyme that Holt was studying, MAO-B, is thought to play a role in Parkinson’s disease and a colleague of Holt noticed that the leached compounds affected the binding of GABA receptors in the brain.

For now, Holt is dealing with the problem in his own lab by carefully washing out plastic equipment with methanol and pure water to remove as much of the additives as possible. But the pre-cleaning process is inconvenient, as is switching to non-disposable glass equipment. In the long term, he hopes manufacturers will offer a choice of products that contain different additives so researchers can choose the type that will have the least affect on their particular experiments. “It leaves us in a mess, but I don’t think it’s a mess that we can’t address,” he says [New Scientist].

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Image: flickr / mararie

CATEGORIZED UNDER: Health & Medicine, Technology
MORE ABOUT: plastic
  • gillt

    I think most molecular biologists are aware of the possibility for plastic contamination when using DMSO, especially during certain pcr reactions. When there are unexpected results, troubleshoot. It’s a rare problem to be sure, and seems a bit over-hyped.

  • Dr. Andy Holt

    Scientists are indeed aware that plastics cause problems in some experiments. However, problems are “avoided” by trying not to use plastics (not always possible) or by ignoring what are often relatively minor effects. To say that “it’s a rare problem to be sure” is actually very wrong. We have shown effects on several enzymes and receptor systems, and I have received many e-mails from other scientists over the past week with similar stories of effects on other functional proteins – ion channels seem to be particularly susceptible to the effects of many plastic leachates. Some of the horror stories I have heard are quite astounding, and the detective work done to confirm plastics as the source of the problems typically took months. In our Pharmacology Department (fewer than 20 active research groups), two groups have confirmed plastic-related problems and two further groups are investigating what they believe to be plastic-related problems. Four research groups from fewer than twenty! This is an issue affecting, most likely, a minority of experiments, but a small percentage of a huge number of experiments is still a very large number! Rather than stick their heads in the sand, scientists should look carefully at whether their own experiments may be susceptible. These are potent effects, and in some cases, they are predictable effects – one of the compounds we identified (oleamide) is probably the most potent reversible inhibitor of human monoamine oxidase-B identified to date!

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