Response surface methodology box-behnken design to optimise the hydrothermal synthesis of gadolinium nanoparticles

Gadolinium (Gd) nanoparticles (NPs) are increasingly considered as a viable alternative to clinically employed Gd chelates in magnetic resonance imaging (MRI). The utilisation of these materials as contrast agents offers several advantages including lower toxicity, prolonged circulation time, and a sufficiently high Gd content, thereby enhancing disease imaging during MRI diagnosis. Therefore, this study synthesised Gd NPs using the hydrothermal method based on the response surface methodology Box-Behnken design (RSM-BBD) to determine the optimal conditions. In this experimental design, three independent variables, the mass of Gd2O3 (g), the synthesis temperature (degrees C) and time (h), were optimised to obtain sufficiently sized nanoparticles for further biomedical applications. In addition, polyethene glycol-6000 (PEG-6000) was used as a stabiliser to form uniformly sized nanoparticles. The optimal conditions were 0.4910 g of Gd2O3, a temperature of 180 degrees C, and a synthesis time of 7 h. Characterisation by scanning electron microscope-energy dispersive X-ray (SEM-EDX) and transmission electron microscope (TEM) demonstrated that the Gd NPs were spherical with a size range below 20 nm. Fourier transform infrared (FTIR) spectroscopy identified PEG molecules with low intensity on the Gd NPs and the obtained zeta potential value was + 36.7 +/- 0.802 mV. The RSM-BBD analysis applied in this study facilitated the determination of the optimal synthesis conditions.