HEPES Buffer
Quick Facts
| Feature | Information |
|---|---|
| Supplement Type | Biological buffer |
| Full Name | 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid |
| Abbreviation | HEPES |
| Molecular Formula | C₈H₁₈N₂O₄S |
| Molecular Weight | 238.30 g/mol |
| Effective Buffering Range | pH 6.8-8.2 |
| Optimal Buffering Range | pH 7.2-7.6 |
| Typical Stock Solution | 1 M |
| Typical Working Concentration | 10-25 mM |
Overview
HEPES is a zwitterionic biological buffer widely used in mammalian cell culture to stabilize physiological pH independently of the bicarbonate/CO₂ buffering system. It is particularly valuable during procedures performed outside a CO₂ incubator, where conventional bicarbonate-buffered media rapidly become alkaline due to CO₂ loss.
HEPES is commonly incorporated into media used for live-cell imaging, flow cytometry, cell sorting, electrophysiology, transfection, and prolonged sample handling.
Biological Role
HEPES maintains extracellular pH, helping preserve:
- Enzyme activity
- Membrane integrity
- Protein stability
- Cellular metabolism
- Cell viability during handling
Unlike nutrients or growth supplements, HEPES functions solely as a buffering agent.
Mechanism of Action
HEPES acts as a zwitterionic buffer by reversibly binding or releasing hydrogen ions (H⁺), thereby resisting rapid pH fluctuations.
This buffering capacity is especially important when cultures are exposed to atmospheric air outside a CO₂ incubator.
Typical Applications
HEPES is commonly used for:
- Live-cell imaging
- Fluorescence microscopy
- Time-lapse microscopy
- Flow cytometry
- Fluorescence-activated cell sorting (FACS)
- Electrophysiology
- Cell transport
- Stem cell manipulation
- Primary cell handling
Recommended Use
| Parameter | Recommendation |
|---|---|
| Stock Solution | 1 M |
| Working Concentration | 10-25 mM |
| Addition | Use only if the basal medium does not already contain HEPES |
Many commercial formulations of DMEM, DMEM/F-12, RPMI-1640, IMDM, Neurobasal, and Williams' E are available with pre-added HEPES.
Advantages
- Stabilizes physiological pH outside CO₂ incubators
- Improves cell viability during prolonged handling
- Compatible with most mammalian culture media
- Particularly useful for microscopy and flow cytometry
- Low cytotoxicity at recommended concentrations
Limitations
- Does not replace bicarbonate buffering for routine long-term culture
- Provides no nutritional value
- High concentrations may influence certain experimental systems
- Can generate reactive oxygen species during prolonged exposure to intense UV or blue light during fluorescence microscopy
Comparison with Related Buffers
| Buffer System | Primary Use |
|---|---|
| HEPES | CO₂-independent pH stabilization during handling and imaging |
| Sodium Bicarbonate | Primary buffering system for routine incubator culture |
| Leibovitz's L-15 | Complete CO₂-independent basal medium with an alternative buffering system |
References
- Good NE et al. Hydrogen ion buffers for biological research. Biochemistry (1966).
- Freshney RI. Culture of Animal Cells: A Manual of Basic Technique and Specialized Applications.
- Gibco™ HEPES Buffer Product Information.
- Thermo Fisher Scientific Cell Culture Handbook.
- ATCC Animal Cell Culture Guide.