The Biotin–Avidin Interaction in Biotinylated Gold Nanoparticles and the Modulation of Their Aggregation

Abstract

The biotin–avidin interaction is used as a binding tool for the conjugation of biomolecules for more diverse applications; these include nanoparticle conjugation. Despite this, a thorough investigation on the different aggregates that may result from the interaction of biotinylated nanoparticles (gold nanoparticles, AuNPs, in this work) with avidin has not been carried out so far. In this paper, we address this problem and show the type of aggregates formed under thermodynamic and kinetic control by varying the biotinylated AuNP/avidin ratio and the order of addition of the two partners. The analysis was performed by also addressing the amount of protein able to interact with the AuNPs surface and is fully supported by the TEM images collected for the different samples and the shift of the surface plasmon resonance band. We show that the percentage of saturation depends on the size of the nanoparticles, and larger nanoparticles (19 nm in diameter) manage to accommodate a relatively larger amount of avidins than smaller ones (11 nm). The AuNPs are isolated or form small clusters (mostly dimers or trimers) when a large excess or a very low amount of avidin is present, respectively, or form large clusters at stoichiometric concentration of the protein. Daisy-like systems are formed under kinetic control conditions when nanoparticles first covered with the protein are treated with a second batch of biotinylated ones but devoid of avidin.

Formation of Aggregate-Free Gold Nanoparticles in the Cyclodextrin-Tetrachloroaurate System Follows Finke–Watzky Kinetics

“…However, it should be underlined that the main goal of the present work was to ensure the complete absence of aggregates in order The yield of gold nanoparticles calculated from absorbance spectra (Figure S2) was 6%. This is less than those reported for other systems (e.g., 75% for gold nanoparticles functionalized with a thiol containing a phosphate and a quaternary amino group [73]; 52.5% for those synthesized using Curcuma mangga extract [74]; 15% for those with RNA layer inside peptide-containing lipid envelope [75]). For the calculation of the latter yield [75], only the coating stage was considered, and the possible loss of gold during the synthesis itself was not taken into account.…”

Antibody-Functionalized Polymer Nanoparticles for Targeted Antibiotic Delivery in Models of Pathogenic Bacteria Infecting Human Macrophages

“…A supramolecular interaction between avidin (i.e., positively charged) and the NPs (i.e., negatively charged) functionalized with biotin could be responsible for the agglomeration observed, as was previously described in the literature. 23 However, this agglomeration was reversible under sonication or stirring. Avidin presents four identical subunits (homotetramer), which show high affinity with up to four biotin molecules which could explain the increase in the particle sizes observed.…”

“…aureus antibody is shown in Figure A. The biotinylated antibody was conjugated to the NPs using the avidin–biotin system . First of all, avidin was conjugated to the NPs functionalized with biotin.…”

“…The biotinylated antibody was conjugated to the NPs using the avidin−biotin system. 23 First of all, avidin was conjugated to the NPs functionalized with biotin. For avidin conjugation, 500 mL of NP dispersion (20 mg/mL) were incubated with 2 mL of avidin solution (2 mg/mL) in a closed flask and gently rotated on a roller shaker for 30 min at 4 °C to conjugate avidin with the nanoparticles.…”

A dual-labeled fluorescence quenching lateral flow assay based on one-pot enzyme-free isothermal cascade amplification for the rapid and sensitive detection of pathogens

“…Hence, the pH and concentration of streptavidin were crucial for the conjugation of streptavidin with AuNPs. According to the literature, 42,43 the pH for the best efficiency of the conjugation of protein with AuNPs is calculated as pH = pI + 0.5. The pI of streptavidin is 6.0, so the pH of AuNPs solution was adjusted to be 6.5 during conjugation.…”