Complete growth medium

ComponentCat. No.
Gibco DMEM, with GlutaMAXA3635201
10% Gibco FBSA3160401
1.0 mM Gibco Sodium Pyruvate11360070

Proper culture techniques and procedures are an essential part of ensuring successful transfection. Subculturing, also referred to as passaging, is the removal of medium and transfer of cells from a culture into fresh growth medium, in order to propagate the cells.

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Brightfield image of MCF7 cells in culture
Brightfield image of MCF7 cells in culture, prior to transfection.

Passaging

  • Maintain cells in T-75 flasks.
  • Use Gibco TrypLE dissociation reagent.
  • Passage cells every 3–4 days to ensure that they do not enter senescence.
  • Transfection of cells should be performed only between passages 5 and 25 post-thaw.
  • If designing an experiment that involves transfection, ensure that setup coincides with a cell passage.
  • Plate cells for transfection only 1 day before the experiment.

Tip: Trypsinize HepG2 cells with TrypLE dissociation reagent for 10–15 min in a 37°C incubator. Then add 10 mL of growth medium and use a 10 mL serological pipette with a 200 μL tip on the end to pipette the cell suspension up and down at least 5 times. This step is the most critical to obtain single cells for accurate counting and plating.

Seeding cells for transfection

  • The day before transfection, dissociate cells that are 80–90% confluent in a T-75 flask.
  • Count the cells using standard trypan blue exclusion.
    • ––Important: The cell number and concentration determined can vary significantly depending on what method is used for counting; it is important to be consistent and use a single method throughout an experiment.
  • The cell culture must have >90% viability and be 70% confluent on the day of transfection.
    • ––Important: If cells are not at the right confluence, do not wait until the next day to perform transfection, as this can significantly affect transfection efficiency.
  • Seed 1.1 x 105 cells in 500 μL growth medium for a single well of a 24-well plate.

Transfection protocol

ComponentCat. No.
Invitrogen Lipofectamine 3000 Transfection ReagentL3000008
Gibco Opti-MEM I Reduced Serum Medium31985062
Thermo Scientific Nunc Multidish, 24-Wells, Cell Culture Treated142475

On the day of transfection, which should be 1 day following cell plating, perform the following steps, which have been optimized for a single well of a 24-well plate using Invitrogen Lipofectamine 3000 Transfection Reagent:

StepTubeComplexation componentsAmount per well
(24-well)
1Tube 1Opti-MEM I medium25 μL
Lipofectamine 3000 reagent1 μL
2Tube 2Opti-MEM I medium25 μL
DNA amount (DNA concentration should be 0.5–5 μg/μL)250 ng
P3000™ reagent0.5 μL
3Add tube 2 solution to tube 1 and mix well
4Incubate mixture from step 3 at room temperature for 10–15 min
5Add 50 μL of complex from step 4 to cells;
gently swirl plate to ensure homogeneous distribution of complex to the entire well

Transfection efficiency analysis

At 48 hr following transfection of a GFP reporter construct, cells were evaluated via microscopy and flow cytometry. To assess transfection efficiency, cells were first visualized via fluorescence microscopy for qualitative assessment of protein expression, morphology, and viability (Figure 1). Cells were then prepared for flow cytometry by aspirating the medium and replacing it with 250 μL of a 7:3 mixture of TrypLE reagent:1X DPBS. Cells were incubated at 37°C for 10 min and then pipetted up and down to ensure single cells for flow cytometry analysis.

Posttransfection analysis of fluorescence cells
 Posttransfection analysis of bright-field cells

Figure 1. Posttransfection analysis of cells. (A) Fluorescence and (B) bright-field images demonstrating 57% transfection efficiency.

 

Tips and tricks

  • Decreasing the serum content of the culture medium (to <10%) at the time of transfection is acceptable, but replace with complete growth medium within 4–24 hr post-transfection.
  • Antibiotics can be used during transfection.
  • Prior to flow cytometry, visualize cells under a bright-field microscope to verify dissociation following incubation with TrypLE reagent.

Scaling up or down Lipofectamine 3000 reagent transfections

Use the following table to scale the volumes for your transfection experiment. The most common sizes are listed below.

Culture vesselMultiplication factor*Shared reagentsDNA transfectionsiRNA transfection
Growth mediumOpti-MEM medium for complexingDNAP3000 reagentLipofectamine 3000 reagent**siRNALipofectamine 3000 reagent**
96-well0.2100 μL2 x 5 μL50 ng0.1 µL0.2 µL3 pmol0.3 µL
48-well0.5250 μL2 x 12.5 μL0.25 µg0.5 µL0.5 µL7.5 pmol0.75 µL
24-well1500 μL2 x 25 μL0.5 µg1 µL1 µL15 pmol1.5 µL
12-well21 mL2 x 50 μL1 µg2 µL2 µL30 pmol3 µL
6-well52 mL2 x 125 μL2.5 µg5 µL5 µL75 pmol7.5 µL
60 mm11.055 mL2 x 250 μL5.5–11 µg11–22 µL11 µL166 pmol17 µL
10 cm28.9510 mL2 x 500 μL14–28 µg28–56 µL29 µL434 pmol43 µL
T-7539.4715 mL2 x 750 μL20–40 µg40–80 µL40 µL592 pmol59 µL
T-17592.1135 mL2 x 1.75 mL46–96 µg92–180 µL92 µL1,382 pmol138 µL

* After determining the optimum reagent amount, use the multiplication factor to determine the reagent amount needed for your new plate format.
** Optimum amount needed is determined from the protocol for Lipofectamine 3000 Transfection Reagent.

Ordering information

Gibco Breast Cancer Starter Kit

For your convenience, the essential components of this protocol are now available in the Gibco Breast Cancer Starter Kit. The kit includes: basal medium, FBS, Lipofectamine 3000 reagent, Opti-MEM medium, and TrypLE reagent. The kit is available at thermofisher.com/cancercellculture. For additional components required for the protocol see ordering table below.