A Discussion on Bio-Fluorescent Particle Counters: Summary of the Process and Environmental Monitoring Methods Working Group Meeting with the FDA Emerging Technology Team.

The Process and Environmental Monitoring Methods Working Group, composed of members from industry and instrument manufacturers, met with the FDA Emerging Technology Team to discuss bio-fluorescent particle counting technology, a type of rapid microbiological method. This is a summary of the meeting including submitted questions and answers, and the Process and Environmental Monitoring Methods Working Group's understanding of the FDA Emerging Technology Team's points made.

Differences in the toxicity of cerium dioxide nanomaterials after inhalation can be explained by lung deposition, animal species and nanoforms.

Considerable differences in pulmonary responses have been observed in animals exposed to cerium dioxide nanoparticles via inhalation. These differences in pulmonary toxicity might be explained by differences in lung deposition, species susceptibility or physicochemical characteristics of the tested cerium dioxide nanoforms (i.e. same chemical substance, different size, shape, surface area or surface chemistry). In order to distinguish the relative importance of these different influencing factors, we performed a detailed analysis of the data from several inhalation studies with different exposure durations, species and nanoforms, namely published data on NM211 and NM212 (JRC repository), NanoAmor (commercially available) and our published and unpublished data on PROM (industry provided). Data were analyzed by comparing the observed pulmonary responses at similar external and internal dose levels. Our analyses confirm that rats are more sensitive to developing pulmonary inflammation compared to mice. The observed differences in responses do not result purely from differences in the delivered and retained doses (expressed in particle mass as well as surface area). In addition, the different nanoforms assessed showed differences in toxic potency likely due to differences in their physicochemical parameters. Primary particle and aggregate/agglomerate size distributions have a substantial impact on the deposited dose and consequently on the pulmonary response. However, in our evaluation size could not fully explain the difference observed in the analyzed studies indicating that the pulmonary response also depends on other physicochemical characteristics of the particles. It remains to be determined to what extent these findings can be generalized to other poorly soluble nanomaterials.

The effect of zirconium doping of cerium dioxide nanoparticles on pulmonary and cardiovascular toxicity and biodistribution in mice after inhalation.

Development and manufacture of nanomaterials is growing at an exponential rate, despite an incomplete understanding of how their physicochemical characteristics affect their potential toxicity. Redox activity has been suggested to be an important physicochemical property of nanomaterials to predict their biological activity. This study assessed the influence of redox activity by modification of cerium dioxide nanoparticles (CeO2 NPs) via zirconium (Zr) doping on the biodistribution, pulmonary and cardiovascular effects in mice following inhalation. Healthy mice (C57BL/6 J), mice prone to cardiovascular disease (ApoE-/-, western-diet fed) and a mouse model of neurological disease (5 × FAD) were exposed via nose-only inhalation to CeO2 NPs with varying amounts of Zr-doping (0%, 27% or 78% Zr), or clean air, over a four-week period (4 mg/m3 for 3 h/day, 5 days/week). Effects were assessed four weeks post-exposure. In all three mouse models CeO2 NP exposure had no major toxicological effects apart from some modest inflammatory histopathology in the lung, which was not related to the amount of Zr-doping. In ApoE-/- mice CeO2 did not change the size of atherosclerotic plaques, but there was a trend towards increased inflammatory cell content in relation to the Zr content of the CeO2 NPs. These findings show that subacute inhalation of CeO2 NPs causes minimal pulmonary and cardiovascular effect four weeks post-exposure and that Zr-doping of CeO2 NPs has limited effect on these responses. Further studies with nanomaterials with a higher inherent toxicity or a broader range of redox activities are needed to fully assess the influence of redox activity on the toxicity of nanomaterials.

Photo-activated affinity-site cross-linking of antibodies using tryptophan containing peptides.

Affinity-based conjugation methods for antibodies can produce defined and reproducible conjugates. This requires that the target antibody has an affinity site for the ligand and that the ligand has a reactive site. These requirements are critical for the conjugation of antibodies designed for diagnostic and therapeutic application. Our laboratory has discovered a novel affinity of antibodies for the amino acid tryptophan using an azido derivative of tryptophan. Here we show that tryptophan without the azido group can be photo-cross-linked to antibodies. Biotinylated tryptophan peptides are photolysed into monoclonal and polyclonal antibodies and such biotinylated antibodies are used in avidin-based ELISA. With the simple and gentle tryptophan-affinity photo-conjugation of peptides, antibodies can be conjugated with peptides to enhance their potency and expand their targeting range.