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Microplate Washers

Microplate Washers


The development of the enzyme-linked immunosorbent assay (ELISA) brought about a revolution in the way that a solution can be assayed for the presence of antibodies or antigens. Briefly, this technique involves immobilising an unknown amount of antigen onto a solid background using either adsorption or by binding to a specific antibody. A detection antibody is added and then a visual reaction is elicited by using a large enzymatic substrate which can be seen as a subtle colour change.

All these steps must be managed with careful washes of detergent in between each to remove unbound substrate. This is a very useful method to detect the presence of pathogens and allergens and is invaluable as a diagnostic screen for various conditions such as HIV. On an epidemiological level, it can be performed in such large numbers that the plates used to host the reactions have also grown in size. From the original small tubes, standard laboratory plates can now be 96 wells, or 384 wells in size. Automated systems can use larger numbers still. 

Microplate washers are a vital part of the technique for a variety of reasons. A good washer must wash the solution with just enough force so that the unbound substrates and buffers are removed without disturbing the reaction products. In addition to complete washing, there is a need to eliminate cross-contamination and provide accuracy and there may be a requirement for speed in a high-throughput environment. There are several different types of washer available to suit the changing needs of the lab.

A manual washer can consist of one or two reservoirs which are attached to a multi-channel dispenser of either eight or twelve jets. Different manifolds can be used to wash strips, or whole plates. 384 well attachments can also be used for faster and accurate washing of the smaller wells. Manual washers are completely controlled by the operator and provide speed and flexibility to the assay.

Automated washers differ greatly in size and complexity. They can incorporate plate aspiration as well as dispensing wash buffer. They can also be programmed with several different wash programs. They can differ in complexity depending on how automated the entire process is. The choice of which microplate washer to use ultimately depends on several considerations. These include speed, accuracy, flexibility or could even be down to space considerations. 

Washing is an essential part of the assay process. Accurate and efficient washing promotes accuracy and prevents variations which can be caused by manual operations. They can increase the percentage of accurate duplicates and increase user faith in the assay results.