Surface Modification of Cetyltrimethylammonium Bromide-Capped Gold Nanorods to Make Molecular Probes

Abstract

A chemical procedure to replace the cetyltrimethylammonium bromide (CTAB) cap on gold nanorods (GNRs) fabricated through seed-mediated growth with organothiol compounds [3-animo-5-mercapto-1,2,4-triazole (AMTAZ) and 11-mercaptoundecaonic acid (MUDA)] was developed to reduce the cytotoxity of GNRs and facilitate further biofunctionalization. Compared to phosphatidylcholine (PC) modification, our procedure yields stable GNRs that are biocompatible and suitable for whole-cell studies. The PC-, AMTAZ-, and MUDA-activated GNRs all showed low cytotoxicity. By choosing different organothiols, net positive or negative charges could be created on the nanorod surface, for different applications. Gold nanorod molecular probes (GNrMPs) were fabricated by subsequent attachment of antibodies to the activated GNRs and were used to visualize and detect cell surface biomarkers in normal and transformed human breast epithelial cells, demonstrating the potential of developing novel biosensors using gold nanorods. The sensitivity of GNrMPs made from organothiol-activated GNRs is considerably higher than that of CTAB/PC-activated GNRs, demonstrating that the protocol reported here is favored in developing molecular probes using GNRs.

Applications of gold nanorods in biomedical imaging and related fields

“…In direct ligand exchange, thiolated biomolecules, such as PEG [29,30] and DNA [31], are directly linked to GNRs by Au-S bonds. In covalent coupling, small bifunctional molecules such as 11-mercaptoundecanoic acids [32] are used as a linker to introduce functional carboxyl groups for further bioconjugation with antibody and protein using carbodiimide coupling agent. Charged proteins, such as antibodies, can adsorb on GNRs via electrostatic interaction.…”

Functionalized gold nanoparticles for the detection of nitrates in water

“…This interest has led to the development of biological and chemical sensors that utilize nanoparticles in different fields (catalysis, biotechnology, electronic, photonic and medicine) (Mosier-Boss and Lieberman 2002;Stewart and Anderton 2008;Tan et al 2010;Vongsvivut et al 2010). Particle size and shape in fact influence physical and chemical properties of nanomaterial and provide a unique optical behavior that, according to the state of aggregation of nanoparticles, produces changes in color (Michota et al 2002;Sharma et al 2010;Yu et al 2007). In fact, the greater k max the larger NPs dimension; larger is the peak and wider is the NPs distribution (Doering and Nie 2002;Handley 1989;Keating et al 1999).…”

Microspectroscopic characterisation of gold nanorods for cancer detection

“…34,45,58,66 Such small gold nanospheres are used as seed particles in the preparation of gold nanorods, which are generally prepared by wet chemical synthesis or so-called seeding growth method, which involves cetyl trimethylammoniumbromide (CTAB) micellar templates, resulting in nanorods capped with a CTAB bilayer (Figure 1.3). [14][15][16][17][18]37,38,40,44,45,50,53,54,67 Gold nanorod sizes can be tuned by altering the ratios of chemicals involved. 14,[16][17][18]20,22,23,[67][68][69] …”

“…14,[16][17][18]32,[34][35][36]42,43,45,48,[51][52][53][55][56][57]62,65,[71][72][73] For example, nonspecific adsorption of serum proteins mediates the uptake of the nanoparticles in vivo. 35,40 Biomolecules have the advantage of inducing very specific cell interactions but their versatility is often limited.…”

“…75 Polyelectrolytes (PE) are used to manipulate the surface charge and functional groups on the nanoparticle surface to tune the charge dependent particle-cell interaction. 34,40,41,53,58,76 Bifunctional polymers often are employed as a linker between the gold nanoparticle and targeting antibodies. 32,48,61 Thiolated polyethylene glycol (PEG-SH) is widely used on the surface of gold nanoparticles 34,36,38,[42][43][44]46,48,65,74,[77][78][79] as well as alkanethiolates 34,45,58 and alkaneamines.…”