Lipid Bilayers Covalently Anchored to Carbon Nanotubes

Abstract

The unique physical and electrical properties of carbon nanotubes make them an exciting material for applications in various fields such as bioelectronics and biosensing. Due to the poor water solubility of carbon nanotubes, functionalization for such applications has been a challenge. Of particular need are functionalization methods for integrating carbon nanotubes with biomolecules and constructing novel hybrid nanostructures for bionanoelectronic applications. We present a novel method for the fabrication of dispersible, biocompatible carbon nanotube-based materials. Multi-walled carbon nanotubes (MWCNTs) are covalently modified with primary amine-bearing phospholipids in a carbodiimide-activated reaction. These modified carbon nanotubes have good dispersibility in nonpolar solvents. Fourier transform infrared (FTIR) spectroscopy shows peaks attributable to the formation of amide bonds between lipids and the nanotube surface. Simple sonication of lipid-modified nanotubes with other lipid molecules leads to the formation of a uniform lipid bilayer coating the nanotubes. These bilayer-coated nanotubes are highly dispersible and stable in aqueous solution. Confocal fluorescence microscopy shows labeled lipids on the surface of bilayer-modified nanotubes. Transmission electron microscopy (TEM) shows the morphology of dispersed bilayer-coated MWCNTs. Fluorescence quenching of lipid-coated MWCNTs confirms the bilayer configuration of the lipids on the nanotube surface and fluorescence anisotropy measurements show that the bilayer is fluid above the gel-to-liquid transition temperature. The membrane protein α-hemolysin spontaneously inserts into the MWCNT-supported bilayer, confirming the biomimetic membrane structure. These biomimetic nanostructures are a promising platform for the integration of carbon nanotube-based materials with biomolecules.

Mixtures of Supported and Hybrid Lipid Membranes on Heterogeneously Modified Silica Nanoparticles

“…The peak in the 240 °C - 270 °C region is primarily attributed to PC as it is unique to the PC-coated samples and is consistent with previous studies of PC pyrolysis. 39 The weight loss from a corresponding uncoated SiNP was subtracted from the coated sample to determine the amount of PC on the SiNP (Table 2). Attempts at lipid coating SiNPs with 100% ODTS functionalization resulted in rapid aggregation in aqueous solutions.…”

“…Sodium dithionite, which quenches the NBD fluorescence by chemically reducing the dye, 39 was added to the PC-coated SiNPs. The fluorescence of each sample was measured and compared to its initial fluorescence.…”

High yield formation of lipid bilayer shells around silicon nanowires in aqueous solution

“…Thus, no further thickness increase of the 1D template is required, compared to e.g. thinner single-walled CNTs [21,41]. Due to Brownian motion the NW moves inside its fluid environment variantly leaving and entering the focus plane (see movie 1 in ESI available at stacks.iop.org/Nano/24/355601/mmedia).…”

“…Longer incubation times will probably increase the chances for SLB formation on uncoated NWs. According to Dayani et al [41], 1D templates of comparable diameter with a lipid bilayer shell are stable in buffer solution for 60 days. Moura et al [42] reported single stabilization of a colloidal solution of lipid coated silica particles when intact single bilayers cover the surface with a saturated phosphocholine density.…”

Directed Assembly of Hybrid Nanomaterials and Nanocomposites

“…Several approaches have been developed to integrate nanoparticles with polymeric species. These include physical wrapping, chemical grafting, and in situ growth of nanoparticles in polymeric media . Noncovalent, or physical functionalization of nanoparticles may utilize strong polymer–particle interactions such as electrostatics or π−π stacking, for example in the case of conjugated polymers or pyrene derivates on graphene and carbon nanotubes (CNTs) .…”