Generation of toxic degradation products by sonication of Pluronic® dispersants: implications for nanotoxicity testing

Abstract

Poloxamers (known by the trade name Pluronic®) are triblock copolymer surfactants that contain two polyethylene glycol blocks and one polypropylene glycol block of various sizes. Poloxamers are widely used as nanoparticle dispersants for nanotoxicity studies wherein nanoparticles are sonicated with a dispersant to prepare suspensions. It is known that poloxamers can be degraded during sonication and that reactive oxygen species contribute to the degradation process. However, the possibility that poloxamer degradation products are toxic to mammalian cells has not been well studied. We report here that aqueous solutions of poloxamer 188 (Pluronic® F-68) and poloxamer 407 (Pluronic® F-127) sonicated in the presence or absence of multi-walled carbon nanotubes (MWNTs) can became highly toxic to cultured cells. Moreover, toxicity correlated with the sonolytic degradation of the polymers. These findings suggest that caution should be used in interpreting the results of nanotoxicity studies where the potential sonolytic degradation of dispersants was not controlled.

Repeated exposure to carbon nanotube-based aerosols does not affect the functional properties of a 3D human epithelial airway model

“…suspension after the preparation process. Recently, Wang et al (2013) reported that surfactants such us Pluronic F127 and Pluronic F68 can become highly toxic to cells due to degradation, during the sonication process. Another study has demonstrated that Pluronic F127 in concentrations as low as 0.01% can induce cell apoptosis on mouse cortical neurons, while the presence of MWCNTs can reduce toxicity (Bardi et al, 2009).…”

Toxicity assessment and bioaccumulation in zebrafish embryos exposed to carbon nanotubes suspended in Pluronic® F-108

“…The bath sonication, centrifugation and dialysis procedures described in our previous work (Wang et al, 2013b) were used with slight modifications to disperse MWNT or SWNT powders in an aqueous 0.2mM PF108 solution. In general, 10mL of 0.2mM PF108 solution was added to a glass vial containing 10 mg pMWNT, cMWNT, pSWNT, or cSWNT powder and sonicated for 1 h at 37 kHz and 120W.…”

“…The physical and chemical properties of these CNT preparations have been previously characterized in addition to their effects on cultured mammalian cells (Wang et al, 2011, 2013b). All the CNTs in PF108 suspensions studied here accumulated in zebrafish embryos in a concentration-dependent manner but only the carboxylated SWNTs were toxic, similar to results found with cultured mammalian cells (Wang et al, 2011).…”

Control experiments to avoid artifacts and misinterpretations in nanoecotoxicology testing

“…4.13 Sonication control with media and organic chemicals/coatings: The purpose of this control is to investigate possible changes to media constituents or toxicological properties of organic chemicals from sonication (19). This control can be tested by adding the test media and any organic chemicals in the test media (e.g., cholesterol), dispersants, or coatings to the container used to sonicate samples, sonicating this sample using the same conditions as those that will be used to disperse the ENMs, and then assessing if this solution would impact the ecotoxicological endpoint being studied.…”