Table 8 Limitations and recommendations for in vitro studies to perform informative IVIVE

Limited data availability

Availability of raw data files (currently scarcely available in literature)

Better recording of methodological information required for modelling. Details typically missing include number of biological replicates used to create averages, reporting units used, and missing information on the protocols such as volume of particle dispersions applied (if reported in µg/mL), the surface area of the well or details of the plate used, and dispersion method followed

Variability in study protocols

Harmonizing endpoint analysis with in vivo studies (i.e. same cytokines/chemokines)

Harmonizing particle dispersion protocols and aligning dose

Harmonizing cell culture and endpoint analysis protocols

Realistic dosimetry values

Providing information about particle deposition on lung cell surface (Dosimetry, Modelling or ALI with quartz microbalance)

Too few applied doses

Increase dose range for assessing dose–response relationship. This is a particular issue for ALI exposures as the process is usually very time-consuming and aerosolization limits the deposition concentration

Known hazardous materials typically only used as positive benchmarks in in vitro assays, therefore typically limited dose ranges applied