Plastics Can Cause Experimental Errors in Biobanks
Biobanks and laboratories use an array of plastic consumables such as pipette tips, sample storage tubes and cell culture flasks. Plastic consumables are convenient, cost-effective and can be sterile, DNase and RNase free. Therefore, biobanking professionals presume these are safe tools for handling biological samples. However, many of the consumable plastics used in biobanks contain bioactive compounds that leach into samples or are inadvertently extracted by solvents stored in tubes. Leached compounds can compromise research results by inhibiting the normal function of biological samples. This can be an undetected source of experimental error and can make results difficult to reproduce.
How Leached Compounds Affect Biobanked Samples
A group of Canadian researchers sought to quantify how biological assays can be affected by bioactive compounds leached from plasticware in laboratories and biobanks [1]. A range of additives are used during plastic manufacturing to optimize properties of the final product such as flexibility, heat and UV tolerance. Certain additives can also lower the cost of manufacturing and therefore, of the final product. Some of these additives are present on the surface of the plastic and can leach into buffers or solvents.
The Canadian researchers were performing assays with an enzyme, human monoamine oxidase-B (hMAO-B). They had unexplained variability in their experimental results. They traced this back to using plastic microfuge tubes from different manufacturers. The researchers washed tubes from various manufacturers with water, methanol, ethanol and DMSO and then analyzed the wash solutions by mass spectrometry, looking for a chemical that could inhibit the hMAO-B enzyme. They found the presence of several hMAO-B-inhibiting compounds including oleamide.
The authors repeated their experiments with pipette tips and 384-well microplates from a number of suppliers and found similar results.
Other studies have shown that leached compounds can inhibit the growth and viability of cultured cells [2, 3]. Furthermore, cell growth rates are different in plastic culture plates sourced from different manufacturers [4]. Microfuge tubes can also leach UV-absorbing compounds that interfere with DNA and protein quantification [5].
Do Brands Matter?
The Canadian researchers found significant variability in compounds leached from different tube brands but also from different sized tubes of the same brand. Some of these tubes were manufactured in different countries. Tubes that inhibited the hMAO-B enzyme did not always affect the results of other assays such as a benzodiazepine-binding assay, and vice versa.
How to Avoid Leached Compounds in Biobanked Samples
The authors listed a number of recommendations on how to avoid leached compounds causing experimental error in biobanks and laboratories. These recommendations are based on their research and similar research from a number of other labs.
1. Ask manufacturers for virgin plastics i.e. plastics that have not been recycled so manufacturers can know all the additives in the product.
2. Ask for products with minimal additives, in particular no slip agents, plasticizers or biocides.
3. Test washes from all plastic consumables in any critical assays. A consumable may inhibit one assay but not another, therefore, all consumables should be tested for all assays.
4. Record lot numbers of all consumables used. When the lot changes, re-screen the new lot for all assays.
Conclusion
This research, and many other studies, show that leached compounds from plastic consumables can be a significant source of experimental error in biobanks and laboratories. However, leached compounds from different products will not affect all assays. Therefore, it is very important to test plastic consumables for the presence of inhibitors for each assay.
It is not practical to replace all plastic consumables with non-plastic options. A more realistic solution is to talk to all suppliers about this problem and ask whether they have tested their products for leached compounds and whether they can supply any information about the additives used during manufacturing.
References
- Olivieri, A., et al., On the disruption of biochemical and biological assays by chemicals leaching from disposable laboratory plasticware. Can J Physiol Pharmacol, 2012. 90(6): p. 697-703.
- Belaiche, C., A. Holt, and A. Saada, Nonylphenol ethoxylate plastic additives inhibit mitochondrial respiratory chain complex I. Clin Chem, 2009. 55(10): p. 1883-4.
- Pant, A.B., et al., In vitro cytotoxicity evaluation of plastic biomedical devices. Hum Exp Toxicol, 2001. 20(8): p. 412-7.
- Clinchy, B., M. Reza Youssefi, and L. Hakansson, Differences in adsorption of serum proteins and production of IL-1ra by human monocytes incubated in different tissue culture microtiter plates. J Immunol Methods, 2003. 282(1-2): p. 53-61.
- Lewis, L.K., et al., Interference with spectrophotometric analysis of nucleic acids and proteins by leaching of chemicals from plastic tubes. Biotechniques, 2010. 48(4): p. 297-302.
