# Gold Nanoparticles and Nanorods in Nuclear Medicine: A Mini Review
## 3 In Vitro Evaluation of Radionuclides Delivered by AuNPs and AuNRs
Similar results are obtained embedded \({}^{124}\)I-Au@AuCBs in the macrophage, which is used as a delivery system for photothermal therapy (PTT) in colon cancer cells (CT26) (see Figure 5) [125]. The cytotoxicity of PEG-\({}^{124}\)I-Au@AuCBs has been examined in various cell types (Chinese hamster ovary-CHO; murine dendritic-DC2.4; breast cancer cells-4T1) by proliferation and apoptotic assays. Figure 4: (**A**) Histogram showing percentage of cell viability against the HeLa cell line after incubation with arabinaxl (AX) suspension. (**B**) Microscopic images showing no morphological changes (**a**) control cells, (**b**) AX-treated cells, (**c**) AX-encapsulated \({}^{198}\)AuNP-treated cells, and (**d**) \({}^{198}\)AuNP-treated cells. Adapted with permission from [122]. Overall, the results show no differences in cell viability; in apoptosis, unlabeled and labeled samples were compared at the concentrations of PEG-124I-Au@AuCBs used, as reported in Figure 6[126]. Figure 5: Cytotoxic effects of 124I-Au@AuCBs in colon cancer CT26 cells after photothermal therapy. (**a**) Analysis of cell viability and (**b**) apoptosis in irradiated cells via annexin V/PI staining. ***\(p<0.0001\); _NS_ not significant. Reproduced with permission of [125]. Figure 6: Cell proliferation assay to determine the biocompatibility of 124I-Au@AuCBs in Chinese hamster ovary (CHO), murine dendritic (DC2.4), and breast cancer (4T1) cells. Cells were plated in 96-well plates for 24 h, and PEG-124I-Au@AuCBs were then added for 48 h. Cell proliferation was determined with (**a**) Cell Counting Kit-8 (CCK-8) assays and (**b**) CellTiter-Glo@Luminescent Cell Viability Assay. Reproduced with permission of [126]. Finally, trastuzumab-\({}^{211}\)At-AuNPs exhibited higher cytotoxicity compared to \({}^{211}\)At-AuNPs. This result encourages the further development of trastuzumab-\({}^{211}\)At-AuNPs as an innovative radiopharmaceutical for local \(\alpha\) therapy of HER2-positive cancers due to specific tumor cell binding and high internalization in the tumor [82]. The cytotoxicity of the polyethylenimine-entrapped gold nanoparticles (Au-PE-NPs) functionalized with PEG, chlorotoxin (CTX)--namely, the peptide tumor-targeting ligand--and 3-(4-hydroxyphenyl) propionic acid-OSu (HPAO) has been assessed in glioma C6 cells in terms of proliferation, before and after radiolabeling with \({}^{131}\)I. The \({}^{131}\)I-Au-PE-NPs-CTX were tested for targeted SPECT imaging and radionuclide therapy in glioma C6 cells. Overall, the results show high viabilities without \({}^{131}\)I, suggesting good cellular compatibility. On the contrary, after treatment with \({}^{131}\)I, the C6 viability decreases in a dose-dependent manner. Also, the cellular uptake is furthered by the addition of the CTX peptide, which occurs through a pathway mediated by receptors. Finally, the targeted specificity has been evaluated by in vitro SPECT imaging. The SPECT signal intensity is increased 4.2-fold in the cells treated with the \({}^{131}\)IAu-PE-NPs-CTX compared to those treated with the \({}^{131}\)I-Au-PE-NPs, as reported in Figure 7[127]. The technetium (Tc) is the radionuclide that is most used in nuclear medicine for diagnostic investigations with SPECT. For this reason, in the age of nanomedicine, it becomes very important to be able to combine it with nanostructures. In a recent paper, the dendrimer-entrapped AuNPs (Au DENPs), labeled with \({}^{99m}\)Tc and functionalized with duramycin, are tested in vitro using SPECT/CT imaging, in order to detect tumor apoptosis in glioma C6 cells after doxorubicin treatment. Duramycin has a high specificity in recognizing the phospholipid phosphatidylserine (PS), which is present on the outer surface of the cellular membrane of apoptotic cells. The results show that SPECT images of apoptotic C6 cells treated with the 99 mTcTc-duramycin-Au DENPs are much brighter than those of apoptotic C6 cells treated with the \({}^{99m}\)Tc-duramycin-Au DENPs [128].