[
Langmuir,
2017]
Controlling the graphene-bio interface is important for biological applications of graphene, which is touted as the wonder material of the new century. Graphene samples made in animal sera indicated low toxicity to cells and nematodes, due to the adsorption of the serum proteins on the nascent graphene sheets. The graphite samples were exfoliated in 6 different animal sera, using three different methods, shear reactor, the kitchen blender and by ultrasonication, and maximum efficiency was noted with the kitchen blender. Raman spectra and electron microscopy of the graphene/serum samples confirmed the formation of 3-4 layer, submicron size graphene, independent of the type of serum used. Graphene prepared in serum was directly transferred to cell culture media without post treatments for toxicity studies. Contrary to many reports, no acute toxicity was detected for human embryonic kidney cells, human lung cancer cells and nematodes (C. elegans) for up to 7 days at various doses (50-500 g/mL). But prolonged exposure to higher doses (300-500 g/mL, 10-15 days) showed cytotoxicity to cells (~95% death) and some reproductive toxicity to C. elegans (5-10% reduction in brood size). The origin of toxicity depended on the flake size, the smaller graphene sheets (<200 nm) were toxic, while the larger sheets were non-toxic (50-300 g/mL dose). In comparison, graphene made with sodium cholate as the exfoliant was cytotoxic to these cells at dosages 50-300 g/L. Thus, exfoliation in serum altered the graphene/bio interface in a favorable manner, and serum suspensions of graphene pacified with serum components are more suitable for biological applications.
[
J Vis Exp,
2014]
Protocols for anoxia/starvation in the genetic model organism C. elegans simulate ischemia/reperfusion. Worms are separated from bacterial food and placed under anoxia for 20 hr (simulated ischemia), and subsequently moved to a normal atmosphere with food (simulated reperfusion). This experimental paradigm results in increased death and neuronal damage, and techniques are presented to assess organism viability, alterations to the morphology of touch neuron processes, as well as touch sensitivity, which represents the behavioral output of neuronal function. Finally, a method for constructing hypoxic incubators using common kitchen storage containers is described. The addition of a mass flow control unit allows for alterations to be made to the gas mixture in the custom incubators, and a circulating water bath allows for both temperature control and makes it easy to identify leaks. This method provides a low cost alternative to commercially available units.