UV-Accelerated Synthesis of Gold Nanoparticle-Pluronic Nanocomposites for X-ray Computed Tomography Contrast Enhancement

Abstract

Eco-friendly chemical methods using FDA-approved Pluronic F127 (PLU) block copolymer have garnered much attention for simultaneously forming and stabilizing Au nanoparticles (AuNPs). Given the remarkable properties of AuNPs for usage in various fields, especially in biomedicine, we performed a systematic study to synthesize AuNP-PLU nanocomposites under optimized conditions using UV irradiation for accelerating the reaction. The use of UV irradiation at 254 nm resulted in several advantages over the control method conducted under ambient light (control). The AuNP-PLU-UV nanocomposite was produced six times faster, lasting 10 min, and exhibited lower size dispersion than the control. A set of experimental techniques was applied to determine the structure and morphology of the produced nanocomposites as affected by the UV irradiation. The MTT assay was conducted to estimate IC50 values of AuNP-PLU-UV in NIH 3T3 mouse embryonic fibroblasts, and the results suggest that the sample is more compatible with cells than control samples. Afterward, in vivo maternal and fetal toxicity assays were performed in rats to evaluate the effect of AuNP-PLU-UV formulation during pregnancy. Under the tested conditions, the treatment was found to be safe for the mother and fetus. As a proof of concept or application, the synthesized Au:PLU were tested as contrast agents with an X-ray computed tomography scan (X-ray CT).

Keywords: Pluronic F127; UV accelerated synthesis; X-ray computed tomography; cytotoxicity; gold nanoparticle; maternal and fetal toxicity assays; nanocomposites.

Figure 1

(A) UV-vis spectra obtained from monitoring the AuNP-PLU:2.0UV formation from the precursor mixture (HAuCl4 + PLU) at t = 0 and after 10 min. The formation of the AuNP-PLU:2.0UV nanocomposite is observed after 10 min. The lower and upper insets show digital snapshots of the reaction mixture at t = 0 min and t = 10 min and changes in the maximum absorption for AuNP-PLU:2.0UV of the plasmonic band during the photoexcitation time, respectively. (B) The observed rate constant of AuNP-PLU:2.0UV and AuNP-PLU:2.0 by the PLU concentration used in the synthesis process, as indicated.

Figure 2

Cyclic voltammograms of the HAuCl4 solution at a concentration of 2.0 mmol L⁻¹, and the AuNP-PLU:0.1UV (lowest PLU concentration), 4.0UV:AuNP-PLU NCs, and AuNP-PLU:0.5 control sample, as indicated. (B) UV-vis spectra of the same samples displayed in (A), as indicated.

Figure 3

TEM micrographs of the AuNP-PLU:2.0UV sample (A) and of the AuNP-PLU:2.0 control (B) both with a scale bar of 0.5 µm and 5 nm in the respective insets. The upper insets depict a crystalline plane {111} of gold nanoparticles; the lower insets (red and blue) show the nanoparticle diameter histograms as vertical bars, as indicated. Data of (B) were reproduced with permission [31]. Copyright 2018, Elsevier B. V.

Figure 4

Sedimentation velocity analytical ultracentrifugation assay. Typical raw sedimentation profiles of absorbance at 530 nm versus cell radius for the particles present in the NCs are shown in (A,B). Residual plot produced using SEDFIT v14.7 software showing the fitting goodness. The lower panels show the apparent distributions of the sedimentation coefficient Is−g* (S) at 260 nm (black) and 530 nm (red) obtained for AuNP-PLU:2.0UV (C) and control AuNP-PLU:2.0 (D). The peaks correspond to different populations of nanoparticles and are indicated with Roman numerals.

Figure 5

ATR FTIR spectra obtained for aqueous solutions of F127 at a concentration of 2.0 mmol L⁻¹ and the AuNP-PLU:2.0UV sample after 10 min of photoexcitation. Inset: enlarged view of the region close to 1700 cm⁻¹.

Figure 6

Effect of AuNP-PLU:2.0UV or AuNP-PLU:2.0 on viability of the NIH-3T3 cells determined using an MTT assay. Cells were incubated with AuNP-PLU:2.0UV (A) or AuNP-PLU:2.0 (B) for 15 min or 24 h. AuNP concentrations ranged from 0.22 to 3.4 μM in the AuNP-PLU:2.0UV sample and 0.05 to 0.86 μM in the AuNP-PLU:2.0 sample. Data are presented as mean ± standard deviation (SD) from three independent experiments. Differences among groups were determined using the Kruskal–Wallis test and Dunn’s multiple comparison post hoc test. Asterisks indicate significant differences compared to the respective control group: * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.

Figure 7

Percentage of losses of embryos before and after implantation at the term of pregnancy (DP21) for rats treated with water (Control) or AuNP (Treated) during pregnancy. p > 0.05 compared with the Control group (Fisher’s Exact test).

Figure 8

Fetal and placental development of rats treated with water (Control) or AuNP (Treated) during pregnancy. (A)—Fetal weight. (B)—Percentages of fetuses classified as small (SGA), adequate (AGA), or large (LGA) for gestational age. (C)—Ossification sites of fetuses. (D)—Placenta weight. (E)—Percentage of anomalies. (F)—Image of normal sternebra of rat fetuses. (G)—Incomplete ossification of sternebra (arrow). * p < 0.05 compared with the Control group (A,C,D—Student’s t-test; B,F—Fisher’s Exact test).

Figure 9

(A) CT images of AuNP-PLU:2.0UV with Au of 1.23 mg/mL compared with Optiray@320_1 containing I at the same concentration (I = 1.23 mg/mL), and AuNP-PLU:2.0 containing a Au concentration of 1.09 mg/mL compared with Optiray@320_2 with I at the same concentration (I = 1.09 mg/mL) attained for beam energies of 80, 100, 120, and 140 KV. (B) CT number attained for the same samples displayed in (A) as a function of beam energy.