A well plate, often called a microplate or microtiter plate, is a fundamental tool in scientific laboratories designed to hold multiple small samples simultaneously. It is a flat, rectangular tray containing an array of small, uniform depressions, each acting as an individual reaction vessel. This standardized format allows researchers to conduct numerous experiments or assays in parallel, enabling increased laboratory efficiency and standardizing experimental conditions for reliable and reproducible biological research.
Physical Characteristics and Standard Design
The defining feature of a 96 well plate is its grid pattern of 8 rows and 12 columns, totaling 96 separate wells. Rows are labeled alphabetically (A to H) and columns are numbered (1 to 12), allowing each well to be uniquely identified (e.g., A1 or H12). This arrangement adheres to the strict physical dimensions defined by the American National Standards Institute (ANSI) and the Society for Laboratory Automation and Screening (SLAS).
This standardized footprint ensures universal compatibility with automated laboratory equipment. The plates are most commonly manufactured from plastics like polystyrene or polypropylene, with the choice depending on the specific experiment. Polystyrene is used for assays requiring optical clarity, such as absorbance measurements. Polypropylene is preferred for applications like Polymerase Chain Reaction (PCR) because of its chemical resistance and ability to withstand wide temperature changes.
The shape of the well bottom is customized for different uses. Flat-bottom wells are ideal for optical readings and cell culture, while V-bottom wells help concentrate samples for maximum recovery. Plates can be manufactured in clear, white, or black colors. Clear plates are used for visual observation, white plates enhance the signal in luminescence assays, and black plates minimize background interference for fluorescence detection.
The Principle of High-Throughput Analysis
The 96 well plate format facilitated the concept of high-throughput screening (HTS). HTS is a method used to rapidly screen large numbers of samples, such as chemical compounds or genetic materials, against a biological target. The plate’s design enables parallelism, meaning 96 different tests can be performed simultaneously under identical conditions.
This parallel testing accelerates the pace of discovery. The small volume capacity of the wells, typically in the microliter range, allows for significant assay miniaturization. Miniaturization conserves costly reagents and biological samples, leading to substantial reductions in experimental cost and waste.
The standardized dimensions of the plate are essential for automation, integrating seamlessly with robotic liquid handlers and plate readers. These automated systems accurately dispense minute volumes of liquids into all 96 wells and then measure the results, such as light absorbance or fluorescence, quickly. This combination of miniaturization and automation makes the 96 well plate the backbone of modern scientific experimentation.
Primary Uses in Biological Research
The standardized format of the 96 well plate makes it a versatile tool across biological and medical research applications. In pharmaceutical research, its most common use is in drug discovery. It allows researchers to screen vast libraries of chemical compounds to identify potential drug candidates. Thousands of different compounds can be tested for their ability to affect a disease-related protein or cell function.
In diagnostics, the plate is the standard platform for the Enzyme-Linked Immunosorbent Assay (ELISA). ELISA is a technique used to detect and quantify substances like antibodies or antigens in blood samples. Each well can be coated with a specific protein, allowing 96 different patient samples or controls to be tested for the presence of a target molecule, such as a disease marker. This method forms the basis of many modern medical tests for conditions ranging from infectious diseases to hormonal imbalances.
The plates are also routinely used for cell culture. The small, isolated wells provide a controlled environment for growing small populations of cells. Specialized surface treatments encourage cell adherence and growth, allowing scientists to conduct dose-response experiments. The effect of different concentrations of a substance, like a toxin or a growth factor, can be observed on cells in parallel. This application is crucial for cytotoxicity testing and understanding cellular biology.