MRI is a powerful, non-invasive imaging technique with exceptional soft tissue contrast, requiring contrast agents to enhance sensitivity by shortening longitudinal (T1) and transverse (T2) relaxation times. While most clinical agents are chelate-based, their potential toxicity has driven the development of nanoparticle-based alternatives. Nanoparticles offer reduced toxicity, improved stability, prolonged circulation time, and better control over surface properties. Lanthanide-based nanoparticles, in particular, are promising due to their paramagnetic properties enhancing MRI contrast. The design of these nanoparticles focuses on optimizing size, shape, and colloidal stability with advances in synthesis techniques allowing for precise control over particle size, morphology, and stability to significantly influence relaxivity. Larger sizes increase r₂ values but may reduce stability, while anisotropic shapes enhance relaxivity compared to the more stable spheres. Surface modifications with functional polymers improve stability and prevent aggregation, optimizing imaging performance. As research progresses, lanthanide-based nanoparticles are poised to become crucial tools in radiology-driven cancer diagnosis and therapy, offering dual functionality for early detection, targeted treatment, and minimized off-target effects. However, these nanoparticles must be refined for tumour-specific diagnostic and therapeutic applications and undergo comprehensive safety evaluations before clinical trials.@en

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 (°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 °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.

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