The Importance of Evaluating the Lot-to-Lot Batch Consistency of Commercial Multi-Walled Carbon Nanotube Products

Abstract

The biological response of multi-walled carbon nanotubes (MWNTs) is related to their physicochemical properties and a thorough MWNT characterization should accompany an assessment of their biological activity, including their potential toxicity. Beyond characterizing the physicochemical properties of MWNTs from different sources or manufacturers, it is also important to characterize different production lots of the same MWNT product from the same vendor (i.e., lot-to-lot batch consistency). Herein, we present a comprehensive physicochemical characterization of two lots of commercial pristine MWNTs (pMWNTs) and carboxylated MWNTs (cMWNTs) used to study the response of mammalian macrophages to MWNTs. There were many similarities between the physicochemical properties of the two lots of cMWNTs and neither significantly diminished the 24-h proliferation of RAW 264.7 macrophages up to the highest concentration tested (200 μg cMWNTs/mL). Conversely, several physicochemical properties of the two lots of pMWNTs were different; notably, the newer lot of pMWNTs displayed less oxidative stability, a higher defect density, and a smaller amount of surface oxygen species relative to the original lot. Furthermore, a 72-h half maximal inhibitory concentration (IC-50) of ~90 µg pMWNTs/mL was determined for RAW 264.7 cells with the new lot of pMWNTs. These results demonstrate that subtle physicochemical differences can lead to significantly dissimilar cellular responses, and that production-lot consistency must be considered when assessing the toxicity of MWNTs.

Graphene-like Carbon from Calcium Hydroxide

“…The MWCNT pores were not accessible as they had closed sections in the core. The lattice fringes of the MWCNT were also shown in Figure S8b and were similar in morphology to commercial MWCNT produced by NanoArmor Figure S9 then shows TEM images of commercially produced nanotubes.…”

“…Other CVD methods, like the formation mechanism of CNTs, use heavy metal catalysts such as cobalt, iron, or molybdenum as catalysts to form carbon such as carbon nanotubes (CNTs). The CNTs form by rapid edge growth by hydrogen abstraction/acetylene addition (HACA) reaction. , The use of heavy metals in the synthesis of carbon nanotubes is well known to be biologically toxic, while calcium is one of the most abundant elements in biological systems. Carbon synthesized using the calcium-catalyzed method is likely to have a high level of biocompatibility.…”

Scavenger Receptor A1 Mediates the Uptake of Carboxylated and Pristine Multi-Walled Carbon Nanotubes Coated with Bovine Serum Albumin

“…The combined carbon, hydrogen, nitrogen, sulfur, and oxygen elemental analyses of the pMWNTs and cMWNTs were 99.52% and 98.18%, respectively, indicative of MWNT powders that are essentially metal-free. An extensive physical and chemical characterization of the pMWNTs and cMWNTs powders appears elsewhere [ 23 ]. The major similarities of the pMWNTs and cMWNTs were their outer diameters (18 ± 3 nm and 19 ± 5 nm, respectively) and inner diameters (5.6 ± 1.3 and 5.7 ± 1.7 nm, respectively), as determined using transmission electron microscopy.…”

Use of Cause-and-Effect Analysis to Optimize the Reliability of In Vitro Inhalation Toxicity Measurements Using an Air–Liquid Interface

“…Changes in the suspension caused by agglomeration and sedimentation can affect the performance of analytical methods (e.g., dynamic light scattering), and the exposure process (e.g., nebulization or aerosolization). Therefore, the use and characterization of an appropriate dose metric, considering all the aforementioned possible changes, are required. , It is important to note that relevant characterization methods of the ENMs, such as mass and size, typically are highly dependent upon the type of ENM evaluated. ,− In addition to sources of variability for the ENM itself, the preparation, handling, batch-to-batch variability, and storage of the formulations used for ENM dispersion can introduce additional variabilities similar to those for chemical formulation. Morever, some ENMs can cause interferences in some biological assays .…”

“…72,73 It is important to note that relevant characterization methods of the ENMs, such as mass and size, typically are highly dependent upon the type of ENM evaluated. 72,74−76 In addition to sources of variability for the ENM itself, the preparation, handling, batch-to-batch variability, 77 and storage of the formulations used for ENM dispersion can introduce additional variabilities similar to those for chemical formulation. Morever, some ENMs can cause interferences in some biological assays.…”