DRUG DISCOVERY & DEVELOPMENT 47
two important new technologies that can help prevent background issues seen in some of the most precise readers.
First, interference from phenol red in cell media requires an optical feature that minimises auto-fluorescence from cell media. Second, since adherent cells do not attach homogeneously at the bottom of each well, it is important to purchase a microplate reader model that has optical features that detect signals of each well and the entire plate.
Te issue of even distribution of cells at the bottom of the wells is a common problem in microplate-formatted cell assays. Te term ‘edge effect’ refers to the observation that results measured from the wells on the edge of the plate may often be statistically different those collected from wells towards the centre of the plate.
Values can vary, and sample results obtained from the edge wells may be higher or lower that those towards the centre.
Tere are methods to prevent the edge effect. Tese include: covering plates during incubation to prevent evaporation, evaluating the assay workflow environment and limiting plate movement.
Another common practice researchers perform to maximise even distribution of cells is to allow the plate to sit for one hour at ambient temperature prior to placing it in 37°C incubator. Tis will allow the cells to distribute more evenly at the bottom of the wells.
Accurately controlling temperature is crucial to maintaining cell viability. Troughout the assay it is important to avoid moving the plate in and out of incubator
since this can cause the edges of the plate to heat or cool at different rates from centre. It is also important to assess the lab space and general area to minimise temperature gradients or other environmental factors.
Also, laboratory personnel may be a source of contamination and human error is a factor known to enable contaminants to enter a cell culture.
Preventing evaporation with plastic lids that have condensation rings or breathable seals that allow gas exchange is an important consideration.
Te Termo Scientific Nunc Edge Plate with evaporation barriers allows researchers to use all 96 wells without exclusion of outer rows due to concern about edge effect. Tis product has superior optical properties for fluorescence signalling in microplate readers.
Demand is increasing for features that will maintain cell viability, keep samples free from contaminants and that are easy to use. Manufacturers have addressed usability by designing microplate readers with features like a user interface with multiple language capabilities.
Operator log files in the software and acoustic alert features help managers monitor personnel usage and sample safety. High sensitivity, a wide dynamic range and low cross talk ensure accurate and precise results for 96- to 384- well plates.
To generate the ideal physiological environment for live-cell assays, high performance microplate readers allow control and monitoring of CO2
levels to provide the flexibility needed for a busy lab. Tese sophisticated instruments have
dual sensor modes for CO2 and O2
and O2
concentration as well as
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