## 3 Results
### Multifunctional Nanoparticles for Therapy and Imaging
#### 3.1.2 Engineered Nanoparticles for Enhanced Diagnostic Imaging  
* Magnetic Nanoparticles  
In the realm of tumor diagnostics, MRI is widely utilized; however, its specificity and sensitivity remain suboptimal. Additionally, adverse reactions to contrast agents in sensitive patients make this method unsuitable for certain groups. To overcome these limitations, researchers have focused on using magnetic nanoparticles in nuclear magnetic resonance, offering potential advancements in imaging precision and safety. These nanoparticles act as contrast agents, improving the resolution and clarity of MRI scans. They can also be functionalized with targeting ligands to allow for more precise imaging of specific tissues, facilitating early detection of diseases such as cancer [39]. Magnetic nanoparticles, particularly those based on superparamagnetic iron oxide (SPIONs), attract significant interest due to their tunable physicochemical properties. Their morphology--typically spherical or ellipsoidal--influences circulation time, cellular internalization, and biodistribution. For clinical applications, ensuring biocompatibility remains essential. Surface functionalization with polymers such as dextran or polyvinyl alcohol improves stability and reduces cytotoxicity. SPION toxicity depends on both dose and particle size. Concentrations below 100 \(\mu\)g/mL are generally considered safe in vitro, although cellular responses may vary depending on the cell type and route of administration. When administered intravenously, SPIONs primarily accumulate in the liver, spleen, and kidneys. In normal hepatic tissue, Kupffer cells selectively uptake these particles, while malignant lesions show minimal or no uptake. This selective distribution enhances lesion-to-liver contrast in MRI. In hepatocellular carcinoma, the absence or depletion of Kupffer cells leads to minimal SPION retention within tumor tissue, producing marked signal differences on T2-weighted MRI. This contrast enhancement improves visualization and supports early detection of HCC, particularly in cases where conventional imaging methods are limited or contraindicated [40]. * Quantum dots (QDs) are semiconductor nanoparticles with exceptional optical properties, including intense, stable, and size-tunable fluorescence, broad absorption spectra, and narrow emission bands. These characteristics make them ideal for advanced biomedical imaging applications, particularly in cancer diagnostics [41]. Thanks to their photostability and strong signal intensity, QDs enable long-term monitoring of cellular processes and the acquisition of high-contrast images, thereby surpassing the limitations of traditional fluorophores. Their well-defined emission also enables the multiplex detection of multiple biomarkers simultaneously, contributing to early cancer diagnosis and the differentiation of tumor-associated molecular patterns [42]. Functionalizing QD surfaces with recognition molecules such as antibodies, aptamers, or peptides allows the specific identification of tumor cells by targeting biomarkers such as AFP, EpCAM, or Her2. This molecular specificity significantly improves diagnostic accuracy by allowing precise tumor localization and facilitating the capture of cancer cells from biological samples such as circulating tumor cells (CTCs) [43]. Researchers have successfully applied QDs in both in vitro and in vivo imaging, even under high autofluorescence conditions, due to their distinct emission signals. Their integration into advanced optical systems generates detailed spectral tumor maps, enabling a clear distinction between healthy and pathological tissue, even at early disease stages [42]. Although earlier generations of QDs raised toxicity concerns, advances in synthesis and functionalization have produced more biocompatible variants--such as carbon-, graphene-, or phosphorus-based QDs--which significantly reduce toxic potential without compromising diagnostic performance [43].