Single-Walled Carbon Nanotube Dispersion in Tryptic Soy Broth

Abstract

There has been little research on the dispersion of carbon nanotubes in dispersions of standard microbiological media. We report that tryptic soy broth (TSB) containing casein digest disperses single-walled carbon nanotubes (SWNT) at concentrations similar to those achieved in lysozyme (LSZ), one of the best known biomolecular SWNT dispersants. Similar to LSZ, the proposed mechanism for SWNT dispersion in TSB is favorable π–π stacking interactions with l-tryptophan. This is supported by similar SWNT concentrations in both LSZ and TSB supernatants, and the absence of appreciable dispersion in TSB that does not contain a source of l-tryptophan. Since l-tryptophan alone is insufficient to enable dispersion, it was previously hypothesized that LSZ’s macromolecular structure created steric hindrance that was critical for SWNT dispersion. These new results show that intermediately sized l-tryptophan containing species can also enable dispersion. In addition, since TSB is a commonly used growth medium for microbiological research, its dispersive ability presents new research avenues for studying the effect of SWNT on prokaryotic cells without the need to oxidize SWNT or add dispersants that may induce microbial stress.

Dispersant Effects on Single-Walled Carbon Nanotube Antibacterial Activity

“…Pluronic and TSB had intermediate concentrations of 0.58 and 0.45 mg/mL, respectively, while lysozyme resulted in the lowest concentration, 0.23 mg/mL. These values were similar to literature values [ 10 , 19 , 20 , 21 , 22 , 23 ] with the exception of SDS, which has a higher final dispersion concentration than reported in the literature [ 11 , 24 ]. Since SWNTs are polydisperse in length, and supernatants can contain both individuals and small bundles, atomic force microscopy (AFM) was used to measure the sizes of the SWNT-dispersant adducts present in each sample.…”

“…The other samples were predominantly individuals. Interestingly, TSB (which was only recently identified as a good SWNT dispersant [ 19 ]) had the highest individual-to-bundle ratio. Length measurements showed the expected polydispersity, with all samples having an average length of approximately 200 nm due to the use of ultrasonication.…”

“…The relatively recent finding by Sloan et al that a standard microbiological growth media, tryptic soy broth, can disperse SWNTs as individuals and small bundles [ 19 ] has created a new opportunity for the direct comparison of SWNT activity in media ranging from mildly bactericidal to growth-supporting. Therefore, in contrast to the existing literature, this work uses the same protocols to explore the activity of SWNTs in both the SDS and pluronic commonly used as pristine SWNT dispersants and the biological dispersants DNA, lysozyme, and tryptic soy broth (TSB).…”

Tuning Mechanical Properties of Pseudopeptide Supramolecular Hydrogels by Graphene Doping

“…A crucial step for the inclusion of graphene in hydrogels is the achievement of a stable dispersion. Various polymers/surfactants/biomolecules were used to facilitate the dispersion of carbon nanomaterials [42,43,44,45] in solution, but these dispersants usually alter the gelation process. The best solution is the dispersion of graphene using directly the supramolecular gel medium.…”

Solid-Phase Debundling of Single-Walled Carbon Nanotubes for the “Stock Solid” Delivery of Concentrated Nanotube Dispersions

“…Between the two approaches developed so far for preparing SWNTs dispersions, noncovalent functionalization is considered to be superior to the covalent one in terms of preserving the conjugated structure and intrinsic properties of SWNTs. Therefore, a number of researchers have concentrated on developing novel and efficient dispersants, including surfactants, − biomolecules, − aromatic compounds, − and polymers, ,, for noncovalent functionalization of SWNTs. On the other hand, the means employed to achieve noncovalent functionalization have been mostly limited to bath and probe type sonication. ,,− Although these liquid-phase sonication based techniques are sufficient for debundling and dispersing SWNTs in various solvents in the presence of dispersant, they suffer from either low concentration or low yield (<60 μg / mL or <15%, respectively) .…”