Cytotoxicity of 1-alkylquinolinium bromide ionic liquids in murine fibroblast NIH 3T3 cells

Minimal toxicity data are available for 1-alkylquinolinium bromide ionic liquids. Here, their toxicity to NIH 3T3 murine fibroblast cells, of relevance to their potential antimicrobial application, is presented. Toxicity data, presented by time-point analysis with a particular focus on the immediate toxicity upon short term cellular exposure, indicate a link between the length of the alkyl chain substituent and resultant biological toxicity. 1-Tetradecylquinolinium bromide was found to exhibit cellular toxicity comparable to benzalkonium chloride over all time points tested. By comparison, 1-octylquinolinium bromide initially exerted significantly lower cytotoxicity at one hour; however, toxicity was found to have a cumulative effect over time-course analysis up to three days. This illustrates that alkyl chain components may govern not only overall toxicity, but also the rate of toxicity. Fluorescence microscopy was utilised to examine destabilisation of the plasma membrane by 1 tetradecylquinolinium bromide and benzalkonium chloride after one hour, with membrane destabilisation not observed for 1-octylquinolinium bromide, or the base constituent quinoline.

Cell type-dependent uptake, localization, and cytotoxicity of 1.9 nm gold nanoparticles

Background: This follow-up study aims to determine the physical parameters which govern the differential radiosensitization capacity of two tumor cell lines and one immortalized normal cell line to 1.9 nm gold nanoparticles. In addition to comparing the uptake potential, localization, and cytotoxicity of 1.9 nm gold nanoparticles, the current study also draws on comparisons between nanoparticle size and total nanoparticle uptake based on previously published data.

Methods: We quantified gold nanoparticle uptake using atomic emission spectroscopy and imaged intracellular localization by transmission electron microscopy. Cell growth delay and clonogenic assays were used to determine cytotoxicity and radiosensitization potential, respectively. Mechanistic data were obtained by Western blot, flow cytometry, and assays for reactive oxygen species.

Results: Gold nanoparticle uptake was preferentially observed in tumor cells, resulting in an increased expression of cleaved caspase proteins and an accumulation of cells in sub G1 phase. Despite this, gold nanoparticle cytotoxicity remained low, with immortalized normal cells exhibiting an LD50 concentration approximately 14 times higher than tumor cells. The surviving fraction for gold nanoparticle-treated cells at 3 Gy compared with that of untreated control cells indicated a strong dependence on cell type in respect to radiosensitization potential.

Conclusion: Gold nanoparticles were most avidly endocytosed and localized within cytoplasmic vesicles during the first 6 hours of exposure. The lack of significant cytotoxicity in the absence of radiation, and the generation of gold nanoparticle-induced reactive oxygen species provide a potential mechanism for previously reported radiosensitization at megavoltage energies.