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Automation of immunoassay

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  388

2026-11-05

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Automation of immunoassay

The ability of an immunoassay to screen large numbers of samples has lead to the development of a number of different automated solutions. These can be tailored to meet the requirements of laboratories using either semi-automated system through to full automation with walk away capability. Automation of a heterogeneous assay sequence up to the separation step is referred to as the ‘front-end’, while those steps post separation are termed ‘back-end’. Full automation of all stages requires a system able to carry out the separation stage. Front-end automation involves an accurate pipetting mechanism for samples and reagents. This is achieved by employing a robotic sample processor that facilitates the automatic transfer of samples (with bar code recognition) from primary tubes to reaction wells (or tubes). This transfer can be done in batch mode (i.e. all samples are pipetted from one destination to another) or by random access (i.e. the selective transfer of sample to one or more different reaction wells) and can be read directly from an imported work-list.

Sampling can be done using either disposable pipette tips or a fixed polytetrafluoroethylene (PTFE)-coated probe coupled with a high precision syringe drive. Use of disposable pipette tips removes the possibility of carry-over, while fixed probe instruments require extensive washing to reduce carry. As this increases the processing times, multiple probe instruments have been developed to increase throughput. Back-end automation can also use pipettes for the reagents (e.g. substrate) and, as with front end systems, can have the ability to time incubation stages and maintain elevated temperatures if required. Both systems require a mechanism that allows multiple batches to be run at the same time. Back-end systems also include a reader and suitable software for data reduction, and can be interfaced with laboratory mainframe computers.

Full automation is essentially a combination of front- and back-end systems that incorporates a suitable mechanism to complete the separation phase. For microplates this involves a simple ‘on board’ washer that automatically dispenses and aspirates wash fluid. Similar systems have been developed for tube washing, although the size constraint means these are stand-alone modules. The process of automation of heterogeneous enzyme immunoassays is well developed and is widely used in blood-bank laboratories in which many thousands of tests can be processed per day. Automation of homogeneous assays is less complex as they do not require a separation step. The most widely used systems, such as the EMIT, CEDIA and Online methods, are readily auto mated on modern clinical chemistry analysers. These analysers are able to pipette accurately, control temperature and measure rates of absorbance. The throughput of the instrument can range from a hundred up to a thousand tests per hour.