One-Pot Tuning of Au Nucleation and Growth: From Nanoclusters to Nanoparticles

Abstract

We describe a simple and effective method to obtain colloidal surface-functionalized Au nanoparticles. The method is primarily based on irradiation of a gold solution with high-flux X-rays from a synchrotron source in the presence of 11-mercaptoundecanoic acid (MUA). Extensive tests of the products demonstrated high colloidal density as well as excellent stability, shelf life, and biocompatibility. Specific tests with X-ray diffraction, UV-visible spectrometry, visible microscopy, Fourier transform infrared spectroscopy, dark-field visible-light scattering microscopy, and transmission electron microscopy demonstrated that MUA, being an effective surfactant, not only allows tunable size control of the nanoparticles, but also facilitates functionalization. The nanoparticle sizes were 6.45 ± 1.58, 1.83 ± 1.21, 1.52 ± 0.37 and 1.18 ± 0.26 nm with no MUA and with MUA-to-Au ratios of 1:2, 1:1, and 3:1. The MUA additionally enabled functionalization with l-glycine. We thus demonstrated flexibility in controlling the nanoparticle size over a large range with narrow size distribution.

X-ray imaging of tumor growth in live mice by detecting gold-nanoparticle-loaded cells

“…We used two types of AuNPs: bare AuNPs and MUA-AuNPs; both types we extensively tested33343536. The one-pot, reducing agent free synthesis produced clean and monodisperse AuNPs with high colloidal stability.…”

“…We also exploited a new, recently developed type of AuNP36 to extend this tracing approaching to visible light. Using again fast x-ray synthesis but with MUA as capping agent, the nanoparticles were found to become photoluminescent, emitting light at ~602 nm under 290 nm UV irradiation, when the Au core size was smaller than 1.2 nm.…”

“…The synthesis and characterization procedures were reported previously30313233343536. In short, these AuNPs are synthesized by a one-pot, reducing-agent-free method taking advantage of the extremely intense x-rays from synchrotron sources.…”

“…We also implemented this imaging strategy taking advantage of a new type of AuNP which emits photoluminescent red light when their core size is reduced to ~1 nm and capped by MUA (11-mercaptoundecanoid acid)36. Similar to the bare AuNPs, large amount of coated AuNPs (MUA-AuNPs) can also be loaded to EMT-6 cells without affecting their viability and cell division.…”

Gold nanoparticles as high-resolution X-ray imaging contrast agents for the analysis of tumor-related micro-vasculature

“…We obtained very good results in vivo with bare-AuNPs in conjunction with heparin, specifically the detection of small (3-5 μm) blood vessels, whereas the tests were less positive for AuNPs coated with mercaptoundecanoid acid (MUA) [30] and for commercial (ExiTron ® Nano 6000) colloidal nanoparticles [31]. …”