Cell Culture Calculators

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Cell culture is the process of maintaining and growing cells in a controlled artificial environment outside an organism. Mammalian cell culture is foundational to biopharmaceutical production, toxicity testing, virology, cancer research, and regenerative medicine. Cells are grown in growth medium (basal medium + serum or defined supplements + antibiotics), in incubators maintaining 37°C and 5% CO₂/95% air. Strict aseptic technique prevents contamination. Cells are periodically passaged (subcultured) to prevent overcrowding. Cell line authentication (STR profiling) and mycoplasma testing are essential quality checks.

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Cell Culture Requirements

  • Growth medium: basal medium (DMEM, RPMI, MEM); 5–20% fetal bovine serum (FBS); L-glutamine (2 mM, usually included); antibiotics (penicillin/streptomycin — optional but common); buffers (HEPES or bicarbonate)
  • Incubator conditions: 37°C; 5% CO₂ (maintains pH via carbonate buffer); 95% relative humidity (prevents evaporation)
  • Atmosphere: Bicarbonate-buffered media requires CO₂ for pH balance. HEPES-buffered media more stable in air.

Passaging (Subculturing)

When cells reach 70–90% confluence: aspirate medium; wash with PBS; add trypsin-EDTA (dissociates cell-ECM and cell-cell adhesion); incubate 3–5 min; neutralize with medium; pellet by centrifugation; reseed at appropriate density.

Contamination

  • Bacterial/fungal: visible turbidity or color change in medium; pH change (yellow medium); treat with antibiotics or discard
  • Mycoplasma: invisible; no turbidity; affects metabolism, gene expression; test monthly by PCR or MycoAlert assay; treat with BM-Cyclin or Plasmocin; discard infected lines
  • Cell line cross-contamination: STR (short tandem repeat) profiling authenticates cell identity

Cryopreservation

Freeze in: 90% FBS + 10% DMSO (cryoprotectant); freeze gradually (−1°C/min in isopropanol-filled Mr. Frosty or controlled rate freezer); store at −150°C or liquid nitrogen (−196°C). Thaw rapidly (37°C water bath); dilute DMSO quickly to avoid toxicity.

Glossary

Cell Culture
Maintenance and growth of cells in a controlled artificial environment; requires 37°C, 5% CO₂, sterile technique, and growth medium with serum; foundational for biopharmaceuticals and research.
Mycoplasma
Small wall-less bacteria (0.2–0.3 μm) that pass through 0.22 μm filters; invisible in culture; alter cell metabolism and gene expression; require monthly PCR testing; major cause of invalidated research data.
DMSO (Cryoprotectant)
Dimethyl sulfoxide used at 10% for cell cryopreservation; prevents intracellular ice crystal formation; toxic at > 1% at 37°C — dilute immediately after thawing; enables indefinite storage at −196°C.

Frequently Asked Questions

Mammalian cells require carefully controlled conditions: Temperature: 37°C (body temperature); cells die or change behavior outside 34–38°C. CO₂: 5% CO₂ in air; maintains pH ~7.2–7.4 via bicarbonate buffer in media (if bicarbonate-based); pH indicator dye (phenol red) turns yellow when acidic (pH < 7.0) and pink/purple when basic (> 7.6). Humidity: 95% relative humidity prevents media evaporation. Sterility: cells have no immune system — any contamination quickly overwhelms them; strict aseptic technique (biosafety cabinet, sterile reagents, gloves) is essential. Growth surface: most cell lines are adherent — they require a flat plastic surface (tissue culture-treated polystyrene); some lines are suspension cells (lymphocytes, some tumor lines) grown in spinner flasks.

Passage adherent cells when they reach 70–90% confluence to prevent contact inhibition and overcrowding. Protocol: (1) Aspirate spent medium. (2) Wash with PBS (room temperature; removes divalent cations that inhibit trypsin activity). (3) Add trypsin-EDTA (0.25% trypsin + 1 mM EDTA); incubate 3–5 min at 37°C — EDTA chelates Ca²⁺/Mg²⁺ (disrupts cell adhesion); trypsin cleaves adhesion proteins. (4) When cells round up and detach: add 4–5× volume of complete medium (serum inhibits trypsin). (5) Transfer to centrifuge tube; spin 300×g 3–5 min; aspirate supernatant; resuspend in fresh medium; count cells; reseed at appropriate density. Common split ratios: CHO, HEK293: 1:5–1:10; HeLa: 1:4–1:8.

Mycoplasmas are the smallest free-living bacteria (0.2–0.3 μm diameter); they pass through 0.22 μm sterilizing filters. They cannot be detected by visual inspection — mycoplasma-contaminated cultures look normal. Effects of mycoplasma: altered gene expression and signaling; abnormal karyotype; inhibited or stimulated proliferation; altered glucose/lactate metabolism; impaired transfection; invalid experimental results. Prevalence: 15–35% of cell cultures in some studies are mycoplasma-positive. Detection: PCR (most sensitive); luminescent assay (MycoAlert); Hoechst staining (shows extranuclear DNA). Treatment: BM-Cyclin or Plasmocin may clear contamination; discard irreplaceable contaminated lines to prevent spread. Prevention: regular testing (monthly); closed work practices; validated cell stock management.

Cryopreservation preserves cells at ultra-low temperatures (−150°C to −196°C liquid nitrogen) indefinitely. DMSO (dimethyl sulfoxide, 10% final): cryoprotectant that penetrates cells and replaces water — prevents intracellular ice crystal formation that would lyse cells. Protocol: prepare cell suspension; mix 1:1 with 2× freezing medium (80% FBS + 20% DMSO); transfer to cryovials; cool gradually: 1°C/min controlled rate (isopropanol 'Mr. Frosty' freezing container at −80°C freezer → liquid nitrogen). Gradual cooling allows water to leave cells slowly before freezing. Thawing: rapid thaw (37°C water bath, 1–2 min); dilute DMSO immediately by adding to 10× volume warm medium; DMSO is toxic to cells at 37°C at > 1% concentration.