In addition to triggering desired reactions, nanoparticles can also cause undesired, toxicological responses. However, even looking at the interactions between cell membranes and nanoparticles is still a complex problem. Many numerical simulations have attempted to study the phenomena of a nanoparticle crossing a lipid bilayer using molecular dynamics (MD) or dissipative particle dynamics (DPD). Physiochemically, these nanoparticles have many variables to consider: size, shape, surface charge, deformability or stiffness, chemical composition, etc. These variables can affect how the body interacts with the DDS in the bloodstream and in other environments. Because of the complexity of developing the ideal DDS, computational studies, including those using MD, can provide insight to assist the design of new formulations. Simulations can be used to study drug-DDS interactions, stability, drug retention, drug release mechanisms, drug loading capacity, resulting aggregations such as protein coronas, self-assembly, and various environmental conditions. Since simulations of full liposomes that are in the micron scale can be computationally expensive, many studies infer liposome behavior from lipid bilayer simulations. This is particularly true of the atomistic level. For example, Dzieciuch et al. did atomistic simulations of PEGylated lipid bilayers with polyethylene glycol (PEG) and zwitterionic lipid bilayers to determine drug loading efficiency of their corresponding liposomes. While the majority of experimentally and clinically studied nanoparticles are spherical, there has been a growing understanding of non-spherical nanoparticles, furthering the possibilities for versatile drug delivery technologies. Studies of carbon nanotubes found that those with an aspect ratio of 1.5 penetrate the lipid bilayer better than spherical nanoparticles or those with a larger aspect ratio, or the length:diameter ratio. This kind of elongation could also be pertinent to the transport of deformable and ultra-deformable liposomes through a cell membrane. Deformable liposomes respond to mechanical stress by displacing some lipid layer components to zones of higher curvature or stress. This is particular true of edge activators, which are single chain surfactants with high radius curvature and are extremely mobile. On the other hand, phospholipids stay in the zones of lower curvature or stress to minimize the elastic energy of the membrane. This allows the deformable liposomes to change shape and volume with minimal energy cost. Figure : The RNT hierarchy from motif to nanotube functionalized with a lysine side chain. While targeted cellular uptake of CNTs has shown promise, the long term degradation of CNTs has yet to be studied. While many nanoparticles have a tendency to degrade quickly in the bloodstream, CNTs can persist for weeks. This raises the question of long term toxicity of CNTs, especially considering the biological vulnerabilities patients may possess as a side effect of various cancer therapies. Many experiments use rodent models, which differ from humans and primates in some organ functions, and these models are not observed past six months. That time period is not sufficient enough to study the possibilities of any long term damage. For nanoparticles, it was found that the toxicity is a function of size, stability, aggregation, surface area, functionalization, and other variables. Therefore, a more biocompatible nanotube, such as RNTs, could provide the same, or even better, results as the CNTs while mitigating the potential long term toxicity damage.