Comparative in vitro cytotoxicity study on uncoated magnetic nanoparticles: effects on cell viability, cell morphology, and cellular uptake.

Magnetic iron oxide nanoparticles (MIONPs) must be biocompatible, and a thorough knowledge on their potential cytotoxicity is crucial for their biomedical applications. However, the detailed study about the effects of iron oxide nanoparticles on cell viability, cell morphology, and cellular uptake of different mammalian cells is still insufficient. In this paper, comparative cytotoxicity study of uncoated magnetite nanoparticles at different concentrations was performed on human cervical cancer cell line (HeLa) and immortalized normal human retinal pigment epithelial cell line (RPE). The size, structure, and magnetic behavior of the MIONPs were characterized using transmission electron microscopy (TEM), X-ray diffractometry (XRD), and vibrating sample magnetometry (VSM) respectively. After 24-hour incubation with the MIONPs, the cell viability was determined by live/dead assay, the cell morphology at high magnification was observed under scanning electron microscopy (SEM), and the cellular uptake of MIONPs was measured under TEM and verified by energy-dispersive X-ray spectroscopy (EDX) analysis. Our results indicate that the uncoated MIONPs at a high concentration (0.40 mg/ml) were toxic to both HeLa and RPE cells. However, the cytotoxicity of uncoated MIONPs at low concentrations was cell-type specific, and RPE cells were more susceptible to these MIONPs than HeLa cells. The effects of the MIONPs on cell morphology and the nanoparticles uptake also showed different features between these two cell lines. Hence cell type should be taken into consideration in the in vitro cytotoxicity study of uncoated MIONPs. Additionally, it should be noticed that the cell morphological changes and the uptake of nanoparticles can take place even though no toxic effect of these MIONPs at low concentrations was reflected in the traditional cell viability assay.

Role of mitogen-activated protein kinase in Zn-BC-AM PDT-induced apoptosis in nasopharyngeal carcinoma cells.

Photodynamic therapy (PDT) with a recently developed photosensitizer Zn-BC-AM was found to effectively induce apoptosis in a well-differentiated nasopharyngeal carcinoma (NPC) HK-1 cell line. Sustained activation of p38 mitogen-activated protein kinase (MAPK) and c-jun N-terminal kinase (JNK) as well as a transient increase in activation of extracellular signal-regulated kinase (ERK) were observed immediately after Zn-BC-AM PDT. A commonly used p38 MAPK/JNK pharmacological inhibitor PD169316 was found to reduce PDT-induced apoptosis of HK-1 cells. PD169316 also prevented the loss of Bcl-2 and Bcl-xL in PDT-treated HK-1 cells. However, inhibition of JNK with SP600125 had no effect on Zn-BC-AM PDT-induced apoptosis while inhibition of ERK with PD98059 or p38 MAPK with SB203580 significantly increased Zn-BC-AM PDT-induced apoptosis. Further study showed that knockdown of the p38beta isoform with siRNA also increased Zn-BC-AM PDT-induced apoptosis, indicating that the anti-apoptotic effect of PD169316 in PDT-treated HK-1 cells was probably independent of p38 MAPK or JNK activation. Taken together, the results suggest that inhibition of p38beta and ERK may enhance the therapeutic efficacy of Zn-BC-AM PDT on NPC cells. It should be noted that data only based on the use of PD169316 should be interpreted in caution.

Apoptosis and expression of cytokines triggered by pyropheophorbide-a methyl ester-mediated photodynamic therapy in nasopharyngeal carcinoma cells.

The photodynamic properties of pyropheophorbide-a methyl ester (MPPa), a semi-synthetic photosensitizer derived from chlorophyll a, were evaluated in a human nasopharyngeal carcinoma HONE-1 cell line. MPPa was non-toxic to the HONE-1. At the concentrations of 0.5-2µM, MPPa-mediated a drug dose-dependent photocytotoxicity in the HONE-1 cells. Confocal microscopy revealed a subcellular localization of MPPa in mitochondria and the Golgi apparatus. MPPa PDT-induced apoptosis was associated with the collapse of mitochondrial membrane potential, release of cytochrome c, the up-regulation of endoplasmic reticulum (ER) stress proteins (calnexin, Grp 94 and Grp78), and the activation of caspases-3 and -9. The photocytotoxicity was reduced by the corresponding specific caspase inhibitors. MPPa PDT-treated HONE-1 cells also up-regulated the gene expression of pro-inflammatory cytokines (IL-1ß, IL-6, and TNF-α) and beta-chemokines (MIP-1ß, MPIF-1, and MPIF-2). These results suggest that the MPPa may be developed as a chlorophyll-based photosensitizer for the treatment of nasopharyngeal carcinoma.