Synthesis, Physicochemical Characterization, and Cytotoxicity Assessment of Rh Nanoparticles with Different Morphologies-as Potential XFCT Nanoprobes

Abstract

Morphologically controllable synthesis of Rh nanoparticles (NPs) was achieved by the use of additives during polyol synthesis. The effect of salts and surfactant additives including PVP, sodium acetate, sodium citrate, CTAB, CTAC, and potassium bromide on Rh NPs morphology was investigated. When PVP was used as the only additive, trigonal NPs were obtained. Additives containing Br^- ions (CTAB and KBr) resulted in NPs with a cubic morphology, while those with carboxyl groups (sodium citrate and acetate) formed spheroid NPs. The use of Cl^- ions (CTAC) resulted in a mixture of polygon morphologies. Cytotoxicity of these NPs was evaluated on macrophages and ovarian cancer cell lines. Membrane integrity and cellular activity are both influenced to a similar extent, for both the cell lines, with respect to the morphology of Rh NPs. The cells exposed to trigonal Rh NPs showed the highest viability, among the NP series. Particles with a mixed polygon morphology had the highest cytotoxic impact, followed by cubic and spherical NPs. The Rh NPs were further demonstrated as contrast agents for X-ray fluorescence computed tomography (XFCT) in a small-animal imaging setting. This work provides a detailed route for the synthesis, morphology control, and characterization of Rh NPs as viable contrast agents for XFCT bio-imaging.

Keywords: X-ray fluorescence; XFCT; bio-imaging; contrast agent; morphology control; polyol synthesis; rhodium nanoparticles; role of additives; surfactants; toxicity.

Figure 1

TEM micrographs of (a) Rh_PVP; (b) Rh_PVP-KBr; (c) Rh_PVP-Na-Ac; (d) Rh_ PVP-CTAB; (e) Rh_PVP-Cit; and (f) Rh_PVP-CTAC.

Figure 2

(a–f) HRTEM micrographs of Rh NPs: (a) Rh_PVP; (b) Rh_PVP-KBr; (c) Rh_PVP-Na-Ac; (d) Rh_ PVP-CTAB; (e) Rh_PVP-Cit; and (f) Rh_PVP-CTAC (the lattice spacings are indexed for fcc Rh using ICDD PDF card no: 03-065-2866).

Figure 3

Hydrodynamic size distribution plots, using the DLS technique, of as-synthesized Rh NPs, with different morphologies in (a) DIW and (b) DMEM. Data presented in volume distribution.

Figure 4

FT-IR spectra of pure PVP and Rh NPs; Rh_PVP, Rh_PVP-KBr, Rh_PVP-CTAB, Rh_PVP-CTAC, Rh_PVP-Ac, and Rh_PVP-Cit.

Figure 5

CCK-8 toxicity assay of Rh-NPs in the RAW 264.7 cell line after 24 h of incubation. The percentage of cell viability is calculated relative to the cells incubated in the absence of NPs (negative control) with 100% viability.

Figure 6

CCK-8 toxicity assays of Rh-CTAC NPs in the (a) RAW 264.7 and (b) SKOV-3 cell lines after 24 h of incubation. The percentage of cell viability is calculated taking negative control cells incubated in the absence of NPs with 100% viability.

Figure 7

CCK-8 toxicity assay of Rh NPs in the SKOV-3 cell line after 24 h of incubation. The percentage of cell viability is calculated relative to the cells incubated in the absence of NPs (negative control) with 100% viability.

Figure 8

In situ XFCT performance of sample Rh-PVP. (a) A pipette tip was used as an imaging target by filling it with Rh-PVP NPs (250 μg/mL), where the conical shape offered a target with an inner diameter ranging from 4 to 0.5 mm. (b) Reconstructed tomographic data visualized in 3D (grayscale: CT, red: XFCT). The portion of the pipette tip visible in the XFCT reconstruction was estimated to be ~20 mm. (c) Selected axial slices with 5 mm separation in y of the XFCT reconstruction, with the theoretical expected diameters at each location denoted with scale bars and numbers. Each pixel in the axial slices corresponds to 200 × 200 μm².