Microtox system, a new approach to the safety evaluation of medical devices

New applications of genetically modified Pseudomonas aeruginosa for toxicity detection in water

A novel mediator-free method based on genetically modified bacteria was developed for detecting water toxicity, where genetically modified Pseudomonas aeruginosa (GM P. aeruginosa) was selected as the biosensor strain and pyocyanin (PYO) produced by this strain was used as the indicator. The toxicity response of GM P. aeruginosa to 3, 5-dichlorophenol (3, 5-DCP) was measured electrochemically and spectroscopically, and the half maximal inhibitory concentration (IC₅₀) of 3, 5-DCP was determined to be 15.1 mg/L. Strikingly, the toxicity of sample solution with 3, 5-DCP could also be estimated visually by naked eyes at a concentration as low as 10 mg/L. The present study provided a convenient, sensitive and cost-effective method for water toxicity detection, and extended biosensing application of the genetically modified bacterium.

Comparison of test methods to screen for residual chemical contamination on medical device surfaces

Reprocessing medical devices involves several steps including cleaning and disinfection or sterilization. Chemical residuals can occur at various stages of reprocessing. These residues could interfere with device function and potentially harm patients. These solutions are composed of a combination of various chemicals and their residues are highly diluted post rinsing, therefore, it is difficult to find a sensitive and rapid method to detect toxicity due to chemical residues. This study focused on (1) finding the levels of residues that are cytotoxic using two mammalian cell lines and Daphnia magna, and (2) evaluating two test methods, Total Organic Carbon (TOC) and the Luminescent Bacteria Test (LBT), to measure residual chemicals levels. The two mammalian cell lines were equal in their cytotoxicity responses. However, Daphnia were more sensitive to some chemical residue than the two mammalian cell lines. TOC and LBT were able to detect the presence of residue well below the levels that were determined to cause mammalian cytotoxicity. LBT was more sensitive for some chemicals and TOC for others, both in solution and in simulated cleaning and rinsing for the limited number of solutions tested in this study.

Examination of in vivo influences on bioluminescent microbial assessment of corrosion product toxicity

The composition of ionically dissolved and precipitated corrosion products from both free corrosion of ASTM F75 Co-Cr-Mo and galvanostatic polarization of Co-Cr-Mo and F138 316L stainless steel was determined using differential pulse polarography and inductively coupled plasma atomic emission spectroscopy. A bacterial bioluminescence assay, Microtox, was used to assess the toxicity of the solid and dissolved corrosion products produced by galvanostatic polarization and the individual ions within them. The role of in vivo salinity, temperature, and protein content as modulators of corrosion product toxicity assessment was investigated empirically and mechanistically. Co-Cr-Mo products were found to be more toxic than those of 316L, and the most toxic ions were Cr6+, Ni2+, and Co2+. Ringer's solution potentiated the toxicity of the more toxic metal ions and reduced the toxicity of the less toxic ions. Using theoretical analysis in conjunction with experimental measurements, the ions in both alloys were found to interact in an antagonistic fashion. The presence of albumin was found to decrease metal toxicity, presumably by chelation.