Pulsed laser ablation synthesis of thiol-functionalized W/Fe nanoparticles in liquid for MRI and CT imaging

Novel Thiol-functionalized tungsten iron oxide nanoparticles with potential applications as contrast agents in medical imaging have been obtained using scanning pulsed ablation in liquid. First, bulk ceramic targets of an orthorhombic (Pbcn) iron (III) tungstate phase type γ-Fe2WO6 with a tri-a-PbO2 structure were prepared using a reaction-sintering method. Then, colloidal dispersions of nanoparticles were produced directly in both distilled water and ethanol by irradiating bulk γ-Fe2WO6 targets with high-power infrared nanosecond laser pulses. In addition, ex situ functionalization processes using glutathione or cysteamine as capping agents were applied, to enhance biocompatibility and colloidal stability at physiological pH values. A battery of techniques was used to characterize the γ-Fe2WO6 targets, the as-synthesized and the functionalized colloidal dispersions of W/Fe nanoparticles, including their composition, structure, magnetic properties, X-ray attenuation potential, biocompatibility and colloidal properties. The results indicate the successful formation of amorphous W/Fe nanoparticles using both distilled water or ethanol as the ablation medium, although only those synthesized in ethanol display a dominant ferromagnetic behavior, making them suitable for use as contrast agents in MRI. Moreover, nanoparticle colloidal dispersions synthesized in ethanol exhibit high X-ray attenuation. The linkage mechanism of functionalization was extensively studied to obtain information for subsequent bioconjugation. The formation of NPs with higher stability and proper functionalization occurs when cysteamine was used as a capping agent, although biocompatibility is better when using glutathione. Finally, functionalized W/Fe nanoparticles demonstrated good magnetic resonance imaging and X-ray computerized tomography imaging abilities, suggesting promising potential as dual-contrast agents.