A dissociation agent is a chemical or enzyme used to separate cells from each other and from the extracellular matrix in a cell culture, tissue sample, or organotypic culture. These agents are commonly used to detach adherent cells from culture vessels for passaging, cell counting, or further analysis. Some common dissociation agents include:

1. Trypsin: Trypsin is a proteolytic enzyme derived from animal sources (usually bovine or porcine) that cleaves peptide bonds in proteins. In cell culture, trypsin is used to break down proteins responsible for anchoring cells to the culture surface, allowing the cells to detach. Trypsin is often used in a diluted solution (e.g., 0.25%) and combined with EDTA.
2. EDTA (Ethylenediaminetetraacetic acid): EDTA is a chelating agent that binds divalent cations such as calcium and magnesium, which are essential for maintaining the integrity of cell-cell and cell-matrix interactions. By chelating these cations, EDTA weakens these interactions, facilitating cell detachment. EDTA is often used in combination with trypsin to improve cell dissociation efficiency.
3. Collagenase: Collagenase is an enzyme that breaks down collagen, a major component of the extracellular matrix. Collagenase is particularly useful for dissociating cells from tissues or organotypic cultures, where the extracellular matrix is more complex and robust than in standard cell cultures.
4. Accutase: Accutase is a commercially available dissociation reagent that contains proteolytic and collagenolytic enzymes, making it useful for a wide range of cell types. Accutase is often used as a gentle alternative to trypsin, as it may cause less damage to cell surface proteins.
5. Dispase: Dispase is a neutral protease that cleaves fibronectin, laminin, and collagen IV, facilitating cell detachment from the extracellular matrix. Dispase is often used for cells that are sensitive to trypsin or for applications where preservation of cell surface proteins is critical.
6. Mechanical dissociation: In some cases, cells can be dissociated by mechanical means, such as gentle scraping or pipetting, without the need for enzymatic agents. This method may be useful for cells that are particularly sensitive to enzymatic treatments or when the preservation of cell surface proteins is crucial.

The choice of dissociation agent depends on the cell type, culture conditions, and the specific application. Always follow the recommended guidelines for your cell line and the dissociation agent to ensure optimal cell recovery and viability.