Antifungal Single Agent - Mammalian Cell Toxicity Measured in Cell-Based and Microorganism Combination System Using Plate Reader - 2148-03_Inhibitor_Dose_CherryPick_Activity
Assay Overview: The basic assay strategy will consist of NIH 3T3 mammalian fibroblasts cultured in 384-well format. Test compounds that do not inhibit subsequent growth will merit further evaluation for their selectivity for fungal inhibition over mammalian cell toxicity. This whole cell phenotypic screening approach will only capture compounds that are capable of entering and accumulating in more ..
BioActive Compounds: 35
Keywords: Candida albicans, drug resistance
Assay Overview: The basic assay strategy will consist of NIH 3T3 mammalian fibroblasts cultured in 384-well format. Test compounds that do not inhibit subsequent growth will merit further evaluation for their selectivity for fungal inhibition over mammalian cell toxicity. This whole cell phenotypic screening approach will only capture compounds that are capable of entering and accumulating in cells to bioactive concentrations. Compound activity will be measured by the metabolism of Alamar Blue, a cell stain that is metabolized to a fluorescent product by living cells but that remains non-fluorescent in wells with growth-inhibited organisms. Geldanamycin serves as the inhibitory control.
Expected Outcome: Wells in which there is toxicity will show a reduced fluorescence intensity due to a reduction in the amount of Alamar Blue dye metabolized by fewer viable cells.
Geldanamycin (GA) 15mM stock sol'n in DMSO
Pen/Strep 100x in PBS
Optimem medium (Invitrogen Cat#31985-070, Lot# 548536)
2.5% (v/v) Fetal Bovine Serum (Hyclone Cat#30071.03, Lot# ARF26748)
1% (v/v) Pen/Strep solution (Invitrogen Cat#15140-122, Lot#529891)
Test Strain: NIH-3T3 mammalian fibroblasts (ATCC # CRL1658)
Concentration in assay plate:#Cells plated at 1,000/well in 40 uL assay medium and cultured overnight at 37C under 5% CO2 in 384-well, transparent bottom, black, tissue culture-treated, bar-coded assay plates
Procedure:#After overnight culture, compounds are pinned into wells at 100nL/well using the CyBio pinning instrument. The final nominal concentration in the well will be a dose range of 26 - 0.195 uM of test compound. The plates will be returned to the tissue culture incubator and culture continued for 48 hrs at 37C under 5% CO2. At the completion of this incubation, Alamar Blue solution diluted 1:40 will be added to each well (10uL/well) to achieve a final dilution of 1:200. Plates will be incubated for a further 2-3 hrs at 37C under 5% CO2 and then fluorescence intensity as a measure of relative viable cell number will be determined on an Envision plate reading fluorometer.
Dilute Alamar Blue Reagent (Biosource International Cat# DAL1100) 1:40 in Ca/Mg-free PBS. Add 10ul/well to plates with Combi (final dilution factor 1:200). Incubate 2 hrs at RT. Read Relative Fluorescence Intensity (RFU) of wells on standard plate reader as measure of relative fungal growth.
Plate reader set-up- Envision, Perkin Elmer: Ex 544nm, Em 590nm, Bandwidth 12nm, Top read.
PRESENCE OF CONTROLS: Neutral control wells (NC; n=36) and positive control wells (PC; n=36) were included on every plate.
EXPECTED OUTCOME: Active compounds result in decreasing readout signal.
ACTIVE CONCENTRATION LIMIT:
For each sample, the highest valid tested concentration (Max_Concentration) was determined and the active concentration limit (AC_limit) was set to equal (2)(Max_Concentration).
The raw signals of the plate wells were normalized using the 'Neutral Controls Minus Inhibitors' method in Genedata Assay Analyzer (v7.0.3):
The median raw signal of the intraplate neutral control wells was set to a normalized activity value of 0.
The median raw signal of the intraplate positive control wells was set to a normalized activity value of -100.
Experimental wells values were scaled to this range.
PATTERN CORRECTION: The plate pattern correction algorithm 'Runwise Pattern (Multiplicative)' in Genedata (v7.0.3) was applied to the normalized plate data.
MEASUREMENT USED TO DETERMINE ACTIVE CONCENTRATION (AC): AC50
AC values were calculated using the curve fitting strategies in Genedata Screener Condoseo (7.0.3).
AC values were calculated up to the active concentration limit described for each sample.
pAC was set to equal -1*log10(AC)
Activity_Outcome = 1 (inactive) when:
a) compound shows activity but in a direction opposite to the expected outcome
in these cases, values describing curve fitting parameters (Sinf, S0, Hill Slope, log_AC50, log_AC50_SE) are set to null
b) curve fit is constant where activity is > -30% and < 30% at all tested concentrations, or
c) AC > AC_limit
Activity_Outcome = 2 (active) when:
AC <= AC_limit
Activity_Outcome = 3 (inconclusive) when:
a) Curve fitting strategy resulted in a constant fit with activity >= -70% but <= -30%, or
b) The fit was deemed not valid due to poor fit quality.
If PUBCHEM_ACTIVITY_OUTCOME = 1 (inactive) or 3 (inconclusive),
then PUBCHEM_ACTIVITY_SCORE = 0
If PUBCHEM_ACTIVITY_OUTCOME = 2 (active)
then PUBCHEM_ACTIVITY_SCORE = (10)(pAC)
Scores relate to AC in this manner:
120 = 1 pM
90 = 1 nM
60 = 1 uM
30 = 1 mM
0 = 1 M
When the active concentration (AC) is calculated to be greater than the highest valid tested concentration (Max_Concentration), the PUBCHEM_ACTIVITY_SCORE is calculated using Max_Concentration as the basis.
When the active concentration (AC) is calculated to be less than the lowest tested concentration, the PUBCHEM_ACTIVITY_SCORE is calculated using the lowest tested concentration as the basis.
The individual dose data point columns ('Activity_at_xxuM') reported here represent the median of valid (unmasked) replicate observations at each concentration. These values are the inputs to a curve fitting algorithm.
All other data columns represent values which are derived during the curve fitting algorithm; this may sometimes include automatic further masking of some replicate data points.
Occasionally this results in perceived inconsistencies: for example, between the derived 'Maximal_Activity' and the apparent most active data point.
Categorized Comment - additional comments and annotations
Assay Format: Cell-based/Organism-based
Assay Type: Toxicity
Assay Cell Type: NIH 3T3
* Activity Concentration. ** Test Concentration.
Data Table (Concise)