Carbon nanotubes for stabilization of nanostructured lipid particles

Abstract

Carbon nanotubes (CNTs) are increasingly studied for innovative biotechnological applications particularly where they are combined with essential biological materials like lipids. Lipids have been used earlier for enhancing the dispersibility of CNTs in aqueous solutions. Here we report a novel application of CNTs for stabilization of internally self-assembled nanostructured lipid particles of 2-5 μm size. Single-walled ( pristine) as well as -OH and -COOH functionalized multi-walled CNTs were employed to produce nanostructured emulsions which stayed stable for months and could be re-dispersed after complete dehydration. Concentrations of CNTs employed for stabilization were very low; moreover CNTs were well-decorated with lipid molecules. These features contribute towards reducing their toxicity and improving biocompatibility for biomedical and pharmaceutical applications. Our approach paves the way for future development of combination therapies employing both CNTs and nanostructured lipid self-assembly together as carriers of different drugs.

Effect of fullerene on the dispersibility of nanostructured lipid particles and encapsulation in sterically stabilized emulsions

“…Pickering or a combination of the two mechanisms [17,18]. In case of fullerenes, we found that 25 and 30 g/ml solutions of C60 stabilize the lipid particles into an o/w emulsion; however, lower C60…”

“…Emulsions stabilized by solid particles are termed generally as Pickering [32] or Ramsden-Pickering [33] emulsions. Clay platelets [34], food hydrocolloids [35,36] and silica nanoparticles [37] are among such stabilizers, but in our recent work [18] we have employed carbon nanotubes (CNTs) for stabilizing nanostructured lipid particles. Pristine single-walled (SW) CNTs and functionalized multi-walled (MW) CNTs were employed successfully to stabilize internally selfassembled lipid particles [18].…”

“…In this work we have taken a different approach and exploited dispersions of a lipid that forms non-lamellar selfassemblies. The main motivation behind this was twofold, 1) lyotropic liquid crystalline selfassemblies of non-lamellar (hexagonal and cubic) types, are highly attractive for biotechnological applications [15,16], hence studying their interaction with fullerenes may outline the possibilities of developing novel hybrid nanomaterials similar to carbon nanotube-lipid hybrids we developed recently [17][18][19], and 2) due to their unique structure fullerenes could act as stabilizers for nanostructured lipid emulsions, by which an elegant properties of both -fullerenes and lipid nanostructures could be utilized for novel applications.…”

“…More interestingly, concentrations of CNT-stabilizers were very low (<10 µg/ml). The lipid coating [18,19] onto CNTs is believed to reduce their potential cytotoxicity given the fact that lipids are already among essential biomolecules in cells. The 'fullerene' is another carbon allotrope like CNTs, hence it is worth examining for stabilizing properties of nanostructured emulsions similar to CNTs [18].…”

“…The lipid coating [18,19] onto CNTs is believed to reduce their potential cytotoxicity given the fact that lipids are already among essential biomolecules in cells. The 'fullerene' is another carbon allotrope like CNTs, hence it is worth examining for stabilizing properties of nanostructured emulsions similar to CNTs [18]. Moreover, this study is also important in terms of understanding the interaction of fullerenes with a different (non-lamellar) type of model lipid membranes, which, to our knowledge has never been studied before.…”