Phosphate-Buffered Saline, commonly known as PBS, is a widely used buffer solution in biological and biochemical research. This solution provides a stable environment for various laboratory applications, particularly those involving living cells. Gibco supplies this reagent. It forms a balanced salt solution designed to mimic the physiological conditions of the human body, ensuring cellular stability during experimental procedures. Researchers across numerous disciplines depend on Gibco PBS for maintaining cell integrity and achieving reproducible results in their studies.
Core Composition and Chemical Properties
Gibco PBS is formulated with several specific chemical components to achieve its buffering capabilities and physiological compatibility. These typically include monobasic potassium phosphate, sodium chloride, and dibasic sodium phosphate; some formulations also contain potassium chloride. The combination of these salts creates an isotonic solution, which helps prevent cells from swelling and bursting (lysis) or shrinking due to water loss.
The carefully controlled pH of Gibco PBS, typically around 7.4, closely matches the pH of human blood and cellular environments. The phosphate buffering system maintains this physiological pH, resisting changes in acidity or alkalinity that could harm cells during experiments. The precise osmolarity, usually ranging from 280 to 315 mOsm/kg, is also strictly controlled to ensure optimal cellular function and viability.
Primary Applications in Cell Culture
Gibco PBS serves multiple practical purposes within the cell culture laboratory, primarily acting as a gentle, non-toxic medium for handling cells. One common application involves washing cells to remove residual growth media, serum components, or non-adherent cells. This washing step is performed before procedures like cell passaging or applying experimental treatments. The isotonic nature of PBS ensures that cells are not subjected to osmotic shock during these rinsing steps, preserving their structural integrity.
The solution also functions as a stable vehicle for suspending cells for various downstream processes. Cells are often diluted in Gibco PBS for accurate counting using a hemocytometer or automated cell counter. It is also used for preparing reagents by diluting concentrated stock solutions to their working concentrations. Gibco PBS can also be employed for the short-term transport of delicate cell or tissue samples, providing a stable and balanced environment during transit.
Choosing the Right Gibco PBS Formulation
Selecting the appropriate Gibco PBS formulation is based on the presence or absence of divalent cations. The main distinction is between formulations with or without calcium (Ca2+) and magnesium (Mg2+). These divalent ions are necessary cofactors for proteins that mediate cell adhesion, including cell-to-cell and cell-to-extracellular matrix attachments. Therefore, for adherent cells that need to remain attached, such as during routine media changes or gentle washes, PBS formulations with calcium and magnesium are generally suitable.
Conversely, when the goal is to detach adherent cells from their culture vessel, for instance, before passaging or cryopreservation, PBS without calcium and magnesium is typically used. The absence of these ions helps disrupt cell-substrate interactions, making it easier for enzymes like trypsin to detach cells. This formulation is also preferred when rinsing chelating agents from the culture, as these agents bind to divalent cations. Gibco also offers PBS formulations with or without phenol red, a pH indicator, which can be excluded if it interferes with certain downstream assays.
Proper Storage and Handling
Proper storage and handling of Gibco PBS are essential to prevent contamination and preserve its chemical properties. Unopened bottles of Gibco PBS are generally recommended to be stored at room temperature, typically between 15°C and 30°C. This temperature range helps ensure the solution’s stability over its stated shelf life. Storing the solution within this range prevents salt precipitation, which can occur if refrigerated.
When using Gibco PBS, strict aseptic technique is necessary to avoid microbial contamination. Working in a laminar flow hood with sterile pipettes and containers helps prevent contamination. If salt precipitation is observed, the solution can be warmed to room temperature and gently mixed to redissolve the salts. Before each use, visually inspect the solution for cloudiness, particulate matter, or discoloration, as these may indicate contamination or degradation.