Dead cell performance

The phototoxicity test 3T3 NRU was proposed in 1994 and is so far the only in vitro method that has been validated by European regulatory authorities for predicting the photoirritant potential of substances [5,40,41]. In this test, the mouse fibroblasts cell line Balb/c 3T3 is exposed to simulated solar UV (or, more frequently, solar UVA) in the presence of the test compound after an incubation of 1 h in the dark. Evaluation of cytotoxicity is performed 24h post-exposure using the neutral red uptake (NRU) method. N RU permits to distinguish live and dead cells, since intact cells retain this dye (detailed method in INVITOX protocol 78). The validation was performed with substances selected on the basis of their in vivo photoirritant or phototoxic properties. Some of these structures are shown in Table 19.1. 

In summary, it has been demonstrated that surface morphology is critically important in determining the performance of solar cells with layered compound semiconductors. Steps on structured surfaces of transition metal dichalcogenides have been identified as carrier recombination sites. The region defined by the depth of the space charge layer parallel to the van der Waals planes can be considered as essentially "dead" in the sense that its photoresponse is negligible. As the "step model" predicts, marked improvement in solar cell performance is found on samples with smooth surfaces. 

The seeding of carcinoma cells must be performed based on a live, healthy cell count. Dead cells (those that stained with Trypan blue) are not to be considered because they are expected to sediment in the high-density region. 

Synthetic hiomaterials, whether they are metallic, ceramic or polymeric, shall be thoroughly tested for their in vivo hiocompadbility. In vivo animal tests apparently place a burden on the shoulders of many materials-hased research groups since such animal tests require tedious histological examinations and careful interpretation. In vitro osteoblast cell culture tests, mainly reporting the live/dead cell numbers and the popular ALP (alkaline phosphatase) activity data, have thus been the most routine tests performed by the materials-based research groups which lack collaborative partnerships with the external veterinarians and skilled histologists. DMEM (or a-MEM) solutions are the media of choice in such in vitro cell culture tests. 

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