Sigma-Aldrich Forma/Gluta Fixation Buffer 10X

Formaldehyde/Glutaraldehyde Fixation Buffer 10X (modified Karnovsky′s fixative) composed of 20% formaldehyde and 2% glutaraldehyde is widely utilized in cell biology, microscopy, and immunostaining due to its balance between effective protein crosslinking and antigen preservation. This formulation leverages the rapid tissue penetration of formaldehyde and thestrong cross-linking capacity of glutaraldehyde, making it ideal for high-resolution structural and molecular studies. Formaldehyde reacts quickly with amine groups in proteins, preserving overall cell morphology, while glutaraldehyde forms longer, stable cross-links that better stabilize ultra structure but may mask antigenic sites. The combination of formaldehyde and glutaraldehyde provides optimal reduction of such masking while maintaining cellular detail, a critical consideration for immunostaining and microscopy workflows.

The fixative solution is a vital component in electron microscopy specimen preparation and essential for chemically stabilizing living tissues. Fixation durations vary by tissue type: soft tissues generally require 2–4 hours, hard tissues 12–24 hours, and cell suspensions 1–2 hours.

Applications of the 2% formaldehyde and 0.2% glutaraldehyde mixture:

• Immunochemistry and ultrastructural preservation: Used to fix frozen rat pancreas sections for immunolabeling, reporting optimal structural preservation and antigen retention.
• Stem cell tracking in bone tissue: Used at 4 °C for 4 days to fix both cultured cells and bone explants, demonstrating excellent results for LacZ staining of mesenchymal stem cells.
• Studies confirm that the 2% formaldehyde + 0.2% glutaraldehyde combination are effective in histology, immunohistochemistry, and enzyme-based staining.

To prepare the working solution, dilute 1:10 with ultrapure water (0.2 µM filtered) to achieve final concentrations of 2% formaldehyde and 0.2% glutaraldehyde in 1X PBS (pH 7.2 ± 0.2). Store the prepared 1X solution at -20 °C.