Stability of Gold Nanorods Passivated with Amphiphilic Ligands

Abstract

The stability of gold nanorods (NRs) coated with amphiphilic ligands (ALs) was investigated. NRs coated with cetyltrimethylammonium bromide (CTAB) were ligand exchanged with polyoxyethylene [10] cetyl ether (Brij56), Oligofectamine (OF), and phosphatidylserine (PS). An aggregation index based on the longitudinal surface plasmon resonance peak broadening was used to measure stability of the NR-ALs under different conditions including the number of washes, pH, ionic concentration, and temperature. The aggregation index was also used to measure the stability of the NR-ALs under ultrafast laser irradiation and in the presence of proteins commonly used in cell culture. Differences in NR-AL stability were found, which were due to differences in the physical and chemical properties of the ALs. Apart from the charge on the AL headgroup, we suggest the Gibbs free energy of passivation (ΔG(p)) and enthalpy of passivation (ΔH(p)) of the AL could potentially aid in the selection of amphiphiles that can effectively passivate NRs for stability and optimize their properties and desired biological impact.

Slow release of ions from internalized silver nanoparticles modifies the epidermal growth factor signaling response

“…This is due to the fact that NP properties are strongly dependent on their surrounding environment [30,31]. DLS analysis indicated that the particles did agglomerated in SF media, with an approximate hydrodynamic diameter of 150 nm.…”

Physiological Fluid Specific Agglomeration Patterns Diminish Gold Nanorod Photothermal Characteristics

“…Theoretical models have linked AR dependent spectral signatures of Au-NRs to projected photothermal efficiencies and have identified particle absorbance to be the predominant factor contributing to the nanophotonic response [11]. Furthermore, previous studies have shown that ionic strength and refractive index of the dispersant fluid directly impacts the absorbance, agglomeration state, and stability of Au-NRs: all of which have the potential to modify the innate photothermal abilities of these nano-sized particles [12,13].…”

“…Aggregation of particles has been shown to have wide-reaching effects and influences outcomes including cytotoxicity, rate of internalization, particle distribution, and spectral profiles [12]. Agglomeration induced modifications to a nanomaterial's absorption spectrum would cause a significant change in nanophotonic response as absorbance is the dominant physical basis for photothermal therapy and imaging applications [14,15].…”

Optical Aggregation of Gold Nanoparticles for SERS Detection of Proteins and Toxins in Liquid Environment: Towards Ultrasensitive and Selective Detection

“…Due to the interplay between the 226 electrostatic interaction of molecules surrounding the NRs with the positively charged CTAB bilayer 227 and the destabilization of the CTAB bilayer induced by the PBS at physiological pH, amino acid 228 residues of the protein get in close contact with NRs gold surface [63,64,65,66]. This yields the 229 formation of biomolecule-NRs complexes [65,67] in which individual NRs are stabilized by the 230 protein layer in the solution.…”

“…This is also the case of NRs 238 covered with CTAB. When we mix BSA (10 -4 M) in PBS (200 mM in water), the high ionic 239 concentration and the pH value of 7.2 causes the destabilization of the CTAB bilayer surrounding 240 the NRs [63]. The presence of BSA and its fast interaction with the gold surface (they form a stable 241 bound in less than 1 µs [65]) ensures a new protein capping layer that can stabilize the suspension.…”