Detecting Contaminants from Plastics

Invented in 1907, plastics have been incorporated into a wide range of industrial and consumer products. While plastics offer many advantages, including flexibility and durability, focus is turning toward the hazards associated with plastics. Aside from the dangers of the physical accumulation of plastics in the environment, certain chemicals used in the production of plastics can be harmful to human, animal, and marine health. After fifty years of use in electrical/hydraulic equipment, plastics, dyes, and related products, polychlorinated biphenyls (PCBs) were banned in the U.S. in 1979.4 More recently, the potential hazards of other classes of chemicals leaching from plastics have come to light.

Phthalates, DEHP

DEHP, or Di(2-ethylhexyl) phthalate, is a chemical added to plastics, including PVC/vinyl, to increase flexibility. It is found in many household products, including vinyl wallpaper, shower curtains, swimming pool liners, plastic lunch boxes, and some plastic food and beverage containers. It is also found in certain medical devices, including dialysis tubing, surgical gloves and blood storage bags. It is currently regulated in children’s toys and clothing and acceptable limits in fresh water and drinking water have been set by the U.S. Environmental Protection Agency, the European Union, and the World Health Organization. Exposure to high doses and extended exposure have caused liver/kidney damage and liver tumors and affected reproductive development in animal studies. The U.S. EPA has designated DEHP a probable carcinogen.  Exposure to newborns or pregnant women is of particular concern. DEHP can gradually be released from products and accumulate in the home and environment. The greatest risks are ingestion through contaminated food or water and extended exposure through medical devices.1,2,3,9

Researchers at Texas A&M University utilized a DNA aptamer discovered by Base Pair to detect low levels of DEHP in tap water, bottled mineral water, and a carbonated beverage, showing utility for environmental and food testing. The sensor was based on surface enhanced raman spectroscopy (SERS), a technique that measures the vibration of molecules on the surface of a noble metal. The sensor measured unbound functionalized SERS silica particles following incubation with aptamer-magnetic beads and free DEHP. Due to preferential binding of aptamer to free DEHP, increased levels of free particles correlated with an increased concentration of DEHP in the sample. Lower limit of detection for the sensor was just 8pM of DEHP, well below published limits of 15 – 20 nM in water.2 View the abstract.

Bisphenols, Bisphenol A (BPA)

BPA is used in the production of polycarbonate plastics, including some food / drink packaging and food storage containers. It is also used in the manufacture of epoxy resins used to coat food cans and water supply pipes and in some dental sealants. BPA can leach from the plastics and resins into food and beverages. Leaching is thought to be accelerated with heat. Exposure to BPA is very widespread. Results of some animal studies have suggested risks to infants and children exposed to certatin levels of BPA. BPA-containing materials are no longer used in baby bottles, sippy cups, and infant formula packaging.8 Researchers in Korea developed a fluorescence assay for detection of BPA in buffer using a truncated DNA aptamer. A 33% change in fluorescence was observed for a 1 ng/mL concentration of BPA vs. a 2 – 4% change for similar compounds.7

Selection of Aptamers to Chemical Contaminants

Aptamers can be selected to differentiate between very similar chemical compounds. In vitro selection enables to discovery of aptamers that perform in a broad range of end-use conditions, accommodating environmental, industrial, and food/beverage testing. Stability of aptamers in a wide range of temperatures makes them ideal candidates for field-based tests utilizing re-usable sensors, lateral flow assays, and solution-based assays. Base Pair has successfully discovered aptamers to BPA and DEHP. View the DEHP product page.

Contact Base Pair for information on selection of aptamers to similar compounds.

References:

  1. CDC, ATSDR, Toxic Substances Portal – Di(2-ethylhexyl)phthalate (DEHP), https://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=377&tid=65c.  Accessed Feb 12, 2019.
  2. Du, T. et al. A SERS aptamer for sensitive and selective detection of bis(2-ethylhexyl)phthalate. RCS Advances. 2019. 9:2618-2625.
  3. EPA. https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=14.  Accessed Feb 12, 2019.
  4. EPA. Polychlorinated Biphenyls (PCBs) https://www.epa.gov/pcbs/learn-about-polychlorinated-biphenyls-pcbs. Accessed Feb 13, 2019
  5. FDA. https://www.fda.gov/NewsEvents/PublicHealthFocus/ucm064437.htm#summary. Accessed Feb 12, 2019
  6. Lan, L. et al. Recent progress in nanomaterial-based optical aptamer assay for the detection of food chemical contaminants. Applied Materials & Interfaces. 2017. 9(28):23287-23301. 
  7. Lee, E., et al., Highly sensitive bisphenyl A detection by NanoAptamer assay with truncated aptamer. ACS Applied Materials and Interfaces. 2017.
  8. NIEHS. https://www.niehs.nih.gov/health/topics/agents/sya-bpa/index.cfm. Accessed Feb 12, 2019
  9. OEHHA. https://www.p65warnings.ca.gov/fact-sheets/di2-ethylhexylphthalate-dehp.  Accessed Feb 12, 2019