Cellular Uptake and Intra-Organ Biodistribution of Functionalized Silica-Coated Gold Nanorods.

PURPOSE: To develop a new nanobiosystem based on folate-functionalized silica-coated gold nanorods and to investigate its cellular uptake and intra-organ biodistribution in vitro and in vivo. PROCEDURES: Ellipsoidal silica-coated gold nanorods (GNRs@SIO2) were prepared by seeded growth method using silicon dioxide (SIO2) as the shell material. Rhodamine-labeled GNRs@SiO2-folic acid (FA) were obtained by reacting the amino group located on GNRs@SiO2-FA with rhodamine isothiocyanate. The characteristics of the prepared GNRs@SiO2-FA were studied using transmission electron microscopy (TEM) and UV spectra. The 3-[4, 5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) colorimetric method was used to assess the biocompatibility of GNRs@SiO2-FA, and their uptake into cells was observed using TEM. In vivo experiments of cellular uptake and study of the intra-organ biodistribution of GNRs@SiO2-FA were detected using intrinsic two-photon luminescence. RESULTS: Analysis of UV spectra confirmed the successfu1 preparation of GNRs@SiO2-FA. Results of the MTT assay demonstrated that surface modification of GNRs@SiO2-FA resulted in excellent biocompatibility. TEM examination revealed that GNRs@SiO2-FA entered the cells via endocytosis, which could connect to cancer cells with high folic acid expression. We found that GNRs exhibit bright luminescence and could be visualized in vivo by direct imaging of these particles within the tissue. Additionally, GNRs@SiO2-FA could specifically bind to tumor cells. GNRs@SiO2-FA entered tumor cells within 24 h and had a heterogeneous distribution with higher accumulation at the tumor cytoplasm. CONCLUSION: GNRs@SiO2-FA can bind to cells and were found to be internalized by targeted folate receptor-expressing cells via a ligand-receptor-mediated endocytosis pathway, which is very useful in diagnosing diseases as well as in treating neoplasm with I-125 particles.

GNRs@SiO2-FA in combination with radiotherapy induces the apoptosis of HepG2 cells by modulating the expression of apoptosis-related proteins.

The aim of the present study was to examine the apoptosis of the hepatocellular carcinoma cell line, HepG2, induced by treatment with folic acid-conjugated silica-coated gold nanorods (GNRs@SiO2-FA) in combination with radiotherapy, and to determine the involvement of apoptosis-related proteins. An MTT colorimetric assay was used to assess the biocompatibility of GNRs@SiO2-FA. The distribution of GNRs@SiO2-FA into the cells was observed using transmission electron microscopy (TEM). HepG2 cells cultured in vitro were divided into the following 4 groups: i)the control group (untreated), ii) the GNRs@SiO2-FA group, iii) the radiotherapy group (iodine 125 seeds) and iv) the combination group (treated with GNRs@SiO2-FA and iodine 125 seeds) groups. The apoptosis of the HepG2 cells was detected by flow cytometry. The concentration range of <40 µg/ml GNRs@SiO2-FA was found to be safe for the biological activity of the HepG2 cells. GNRs@SiO2-FA entered the cytoplasm through endocytosis. The apoptotic rates of the HepG2 cells were higher in the GNRs@SiO2-FA and radiotherapy groups than in the control group (P<0.05). The apoptotic rate was also significantly higher in the combination group than the GNRs@SiO2-FA and radiotherapy groups (P<0.05). Taken together, these findings demonstrate that the combination of GNRs@SiO2-FA and radiotherapy more effectively induces the apoptosis of HepG2 cells. These apoptotic effects are achieved by increasing the protein expression of Bax and caspase-3, and inhibiting the protein expression of Bcl-2 and Ki-67. The combination of GNRs@SiO2-FA and radiotherapy may thus prove to be a new approach in the treatment of primary liver cancer.