Gadolinium nanoparticles (GdNPs) are nanomaterials with great potential to be applied as MRI contrast agents. GdNPs have been widely explored in recent years as a T1 contrast agent with high performance due to the large relaxivity value (r1) compared to commercial Gd-based contrast agents. However, the major limitations of using these materials for biomedical applications are their cytotoxic effects and cellular uptake efficiency. The morphology of GdNPs, such as size, charge, and surface play an important role in affecting biocompatibility and cellular uptake. For instance, by modifying the surface of nanoparticles, the physical-chemical properties can be altered, leading to improvement in biocompatibility and cellular uptake. Various molecules have the potential to be functionalized on GdNPs, but it is essential to select those that can effectively enhance their abilities. Therefore, this review aims to discuss several studies on the effect of morphology and surface modification of GdNPs to improve biocompatibility and cellular uptake. HIGHLIGHTS Biocompatibility and uptake challenges: Size, surface charge, and functionalization of gadolinium nanoparticles (GdNPs) directly affect cellular uptake and biocompatibility, which are essential for safe and effective Magnetic Resonance Imaging (MRI) contrast. Surface modification: The review emphasizes surface modification strategies to enhance biocompatibility and cellular uptake. Functionalization with various molecules tailors GdNPs' physicochemical properties for optimized performance. Implications for design: A detailed examination of studies on morphology and modification approaches reveals pathways to improve GdNPs efficacy and safety in medical imaging. GRAPHICAL ABSTRACT

Radiation therapy has made tremendous progress in oncology over the last decades due to advances in engineering and physical sciences in combination with better biochemical, genetic and molecular understanding of this disease. Local delivery of optimal radiation dose to a tumor, while sparing healthy surrounding tissues, remains a great challenge, especially in the proximity of vital organs. Therefore, imaging plays a key role in tumor staging, accurate target volume delineation, assessment of individual radiation resistance and even personalized dose prescription. From this point of view, radiotherapy might be one of the few therapeutic modalities that relies entirely on high-resolution imaging. Magnetic resonance imaging (MRI) with its superior soft-tissue resolution is already used in radiotherapy treatment planning complementing conventional computed tomography (CT). Development of systems integrating MRI and linear accelerators opens possibilities for simultaneous imaging and therapy, which in turn, generates the need for imaging probes with therapeutic components. In this review, we discuss the role of MRI in both external and internal radiotherapy focusing on the most important examples of contrast agents with combined therapeutic potential.

Dysprosium oxide nanoparticles (Dy₂O₃-nanoparticles) have been extensively used in many different fields of technologies. In addition, with a proper synthesis modification, Dy₂O₃-nanoparticles are promising materials not only for industry purposes, but also for biomedical applications, for instance, through polyethyleneglycol (PEG) attachment as a template on nanoparticles. This study focuses on the optimization of hydrothermal synthesis of Dy₂O₃-nanoparticles using Response Surface Methodology – Box-Behnken experimental design (RSM-BBD). The influences of the volume and concentration of PEG-template to the size diameter of nanoparticles were also studied. The crystal structure and surface morphology Dy₂O₃-nanoparticles with PEG-template modification were characterized using Tabletop Scanning Electron Microscopy (TSEM) coupled with Energy Dispersive X-Rays (SEM-EDX) and X-Rays Diffraction (XRD). Dy₂O₃-nanoparticles were prepared by using hydrothermal synthesis method with PEG-template attachment on the nanoparticles. PEG as a template will create the uniform shapes and prevent the agglomeration of the nanoparticles. For further biomedical applications, it also helps to enhance the biocompatibility of nanoparticles. The optimization of influence parameters on the hydrothermal synthesis of Dy₂O₃-nanoparticles, (e.g. mass ratio precursor (PEG and Dy₂O₃), temperature, and time) were investigated using RSM-BBD. The optimum conditions were 15 g PEG and 0.45 g Dy₂O₃ at 200°C for 7 h resulting in the highest amount of Dy₂O₃-nanoparticles products. SEM image results show spherical and nanowires shapes of Dy₂O₃-nanoparticles produced with the average size diameter of 10.1 nm as the smallest size of nanoparticles. In addition, XRD-patterns indicates the typical cubic structure of Dy₂O₃-nanoparticles with the estimation crystal size of 45.47 nm.