Cytotoxicity and its test methodology for a bioabsorbable nitrided iron stent.

Comprehensive assessments of the cytotoxicity of nitrided iron, a promising bioabsorbable metallic material, were conducted using in vitro methods. Extracting and standing experiments were conducted to determine the factors influencing the precipitation of the extract during extraction and incubation. The MTT method, fluorescent staining, and direct contact method were used to explore the in vitro cytotoxicity of nitrided iron stent extracts, nitrided iron foils, and their bulk corrosion products. The extracting and standing experiments confirmed that the extraction medium and available oxygen are crucial for precipitation during the extraction and incubation processes. In the MTT test, the extract of nitrided iron stents with a high iron ion concentration (124.11 ± 7.55 µg/mL) was not cytotoxic to L929 fibroblasts. Thus, the in vitro cytotoxicity of nitrided iron stents was actually caused by the size effect of corrosion particles and not the material itself. Test methodology for in vitro cytotoxicity of biodegradable iron-based materials was analyzed, and the results demonstrate that multiple methods should be combined for comprehensive evaluation of the cytocompatibility of bioabsorbable iron-based materials to get an impartial conclusion.

Physiological and transcriptional analysis of the effects of aluminum stress on Cryptococcus humicola.

Aluminum (Al) toxicity is a major factor that limits crop productivity in acid soils. The toxic effects of Al exposure on Al-tolerant Cryptococcus humicola were analyzed at the physiological level. The exposure to 20 mM Al led to a clear increase in malondialdehyde content and a significant decrease in the levels of protein carbonyls, suggesting that Al stress caused oxidative damage to membrane lipids but not to proteins. Suppression subtractive hybridization (SSH) results showed that when C. humicola was exposed to 20 mM Al, a total of 141 ESTs were differentially expressed. Of them, 27 had unknown functions and 48 were newly identified in this study. The genes with known functions were categorized into seven groups. The largest group was related to metabolism and energy, followed by protein synthesis and processing, cell structure, signal transduction and transcription, transporters, stress and defense. Reverse transcription (RT)-PCR analysis of certain genes was performed to confirm the reliability of the SSH data. Nine selected genes were upregulated by Al in a time-dependent manner. The potential functions of some genes involved in Al-tolerance were predicted and are discussed. The diversity of the putative functions of these genes indicates that Al stress results in a complex response in C. humicola.