Molecular engineering of gold nanorod surfaces: towards improved physical properties and understanding nanoparticle-cell interactions

Gold nanorods;Partitioning;admicelles;nanotoxicity;nanocomposites;Polymerization;Layer by layer coating;cholesterol;protein adsorption

Alkilany, Alaaldin M.

关键词: Gold nanorods;    Partitioning;    admicelles;    nanotoxicity;    nanocomposites;    Polymerization;    Layer by layer coating;    cholesterol;    protein adsorption;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/18495/Alkilany_Alaaldin.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Gold nanorods have unique optical properties and various promisingapplications. Wet chemical synthesis of gold nanorods requires the use of cetyltrimethylammonium bromide (CTAB) as shape-directing surfactant, which form a bilayeron the surfaces of gold nanorods. CTAB bilayer stabilizes the nanorods againstaggregation and has the ability to sequester organic molecules from aqueous bulk.CTAB molecules in the bilayer are held via weak hydrophobic forces and thus tend todesorb resulting in nanorods aggregation and toxicity to cultured cells. Herein, threesurface-engineering approaches to enhance the colloidal physical stability andbiocompatibility of gold nanorods have been examined: 1) electrostatic approach viaovercoating with polyelectrolytes; 2) covalent approach via surfactant polymerization; 3)and hydrophobic approach via cholesterol insertion into the bilayer.Layer-by-layer coating has been used to overcoat CTAB-capped nanorods withboth negatively and positively charged polyelectrolytes. Compared to CTAB-cappednanorods, polyelectrolyte-coated gold nanorods showed improved stability againstaggregation in culture medium and enhanced biocompatibility to cultured cells. Thetoxicity of CTAB-capped gold nanorod solutions was assigned quantitatively to freeCTAB molecules, where gold nanorods themselves were found not toxic. Similarbiocompatibility profiles for both cationic and anionic coated-gold nanorods wereobserved due to spontaneous protein adsorption. In growth media, all examinednanorods were covered with protein corona and thus bear similar negative effectivesurface charge explaining their similar toxicity profiles.! """! !Our covalent approach to stabilize the surfactant bilayer on the surface of goldnanorods relies on synthesizing a polymerizable version of the CTAB, which we haveused to prepare gold nanoparticles (both spheres and rods). Surfactant polymerizationon the surface of gold nanoparticles was found to retard surfactant desorption and thusenhance both stability against aggregation and biocombatibility of these nanomaterials.The hydrophobic approach to stabilize the CTAB bilayer on gold nanorods relieson using a bilayer-condensing agent such as cholesterol to increase the totalhydrophobic interactions. Cholesterol is known to consist of up to 50% of mammaliancell membrane’s total lipids, and thus have important effect on their stability andphysical properties. Using cholesterol-rich growth medium, we have prepared goldnanorods with excellent size and shape distribution. The prepared gold nanorods in thepresence of cholesterol have a significantly higher surface charge and exhibit superiorstability against aggregation compared to the nanorods prepared without cholesterol.In addition to the enhanced aqueous stability and biocompatibility, stabilizationthe CTAB bilayer on the surface of gold nanorods have allowed for suspension goldnanorods in organic solvents without aggregation. Polyelectrolyte-coated gold nanorodsshowed remarkable stability in polar organic solvents against aggregation as comparedto CTAB-capped nanorods. The suspendability of coated-gold nanorods in polar organicsolvents facilitates the incorporation of these nanomaterials into hydrophobic polymersand thus fabrication of thin films that contain uniform gold nanorod dispersions(nanocomposites).