Tracking the effect of binder length on colloidal stability and bioconjugation of gold nanoparticles
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Understanding the organization of self-assembled monolayers (SAMs) on gold nanoparticles (AuNPs) as protective coatings is a key role of biological applications of nanomaterials. Here, we report the influence on the stability of the surface coverage of three mercaptocarboxylic lingands onto AuNPs, mercaptopropanoic acid (MPA), mercaptoundecanoic acid (MUA) and mercaptopropionic acid (MHA) under different conditions. In addition, we optimized a bioconjugation route using bovine serum protein (BSA) as a protein model. AuNPs and successful binding of ligands and BSA on the AuNPs were analyzed by UV–Vis, TEM, FTIR, RAMAN, DLS and zeta potential. The size of as-synthesized AuNPs was 18 ± 1,2 nm with surface plasmon resonance (SPR) peak at 522 nm. The magnitude of the bathochromic shift of AuNPs with MPA, MUA and MHA was determined by UV–Vis and the SPR band position of AuNP shifts to 1.5, 3 and 5 nm longer. Moreover, the data show the influence of chain length on colloidal stability and covalent and non-covalent coupling steps with nanomaterials. We demonstrate a method for quantitative determination of the coatings on gold nanoparticles and open new perspectives in understanding the influence of monolayer thickness on the generation of nanobioconjugates for biological applications.
KeywordsGold nanoparticles Colloidal stability Thiol ligands Bioconjugation
The authors acknowledge financial support from the Brazilian Ministry of Science and Technology (CNPq Grant 483036/2011-0), the Ministry of Science and Technology (MCTI/FINEP/CT-INFRA grant PROINFRA 01/2006) and the Foundation Support Research and Innovation of Espírito Santo (Grant 006/2014). This work used the equipment facilities at the Laboratory of Cellular Ultrastructure Carlos Alberto Redins and the Laboratory of Biomolecular Analysis (LABIOM) at the Federal University of Espírito Santo, with thanks for providing the equipment and technical support for experiments.
JPO conceived the project. JPO, ARP and WJK performed the characterizations and analysis. All authors contributed to discussions and writing of the manuscript. MCCG guided the research.
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