The scientist, the pipette and the microplate - who isn't familiar with that generic image of a modern laboratory? No research facility would be complete without its microplates and (at least!) one microplate reader - with an astonishing number and variety of industry and research applications. Since the microplate or microtiter plate, as it is also known, was first invented over half a century ago, in a time of epidemic, not unlike today's, the device employed to read assays has gone through some major developments in terms of types and formats. Choosing the right one is a matter of requirements and budget... plus a tiny drop of background knowledge.

Flu for thought

During an influenza outbreak in Hungary in the 1950s, in his search for a way to make serial dilutions, the microbiologist Dr. Gyula Takatsy effectively invented the first 8 by 12-well microplate. Since that time, the microplate has evolved to now even feature various well densities, coatings or colours - the readers too. Previously, spectrophotometers had always been used to detect events or reactions, but could only analyse just one sample at a time. Microplate spectrophotometers or more commonly, microplate readers, could handle multiple samples all in one go and extremely quickly too.

A remarkable trio

Once pipetted into a microplate, the microplate reader detects the light signals produced by samples. The samples go through optical changes as a result of any reactions of a chemical, biological, biochemical or physical nature. An analysis is then made of any changes using various detection modes. There are three popular and widely used detection modes 

• Absorbance

• Fluorescence intensity

• Luminescence 

Absorbance-based microplate readers measure the amount of ultraviolet or visible light absorbed by the sample. Located on the lower end of the price scale, they can be used, for example, for protein quantification or microbial growth assays. Fluorescence intensity detection devices tend to be costlier, but also more sensitive and versatile, and involve illuminating the sample with a specific wavelength. They are often employed for cell viability or enzyme activity assays. Luminescence occurs as a result of a chemical or biochemical reaction and this type of reader is highly sensitive and requires no light source to agitate the sample.  Gene expression or biorhythm assays are just two common applications for luminescence microplate readers, or luminometers - their alternative name. 

More advanced fluorescence-based modes have entered the market including time-resolved fluorescence (TRF) or fluorescence resonance energy transfer (FRET), as well as light scattering and nephelometry devices.

Viable options

Both single-mode and multi-mode plate reader formats are available.  Single-mode microplate readers only use one detection mode while multi-mode devices can handle different modes all in just one machine. The multi-mode variety tend to feature more complex optics and detectors making them more expensive, yet they do of course take up less space.  With so many possibilities and variables, it is important to bear several things in mind when choosing a microplate reader. Firstly, what type of assay and so what kind of measurement is needed. The plate format is also an extremely important factor. Although the most common format is 96 individual wells, arranged in 8 rows and 12 columns (50-200µL per well), plates with thousands of wells are not uncommon and not all readers are equipped to deal with every type of microplate. If larger volumes of samples and therefore plates need to be handled, then the reader processing speed is crucial. With a larger throughput, speed is of the essence. Other considerations include the reader system's ease-of-use and its configuration possibilities. The software to analyse the data obtained should be user-friendly with easy integration with existing systems. Finally, an often-overlooked area is the system's maintenance and support costs as well as other options to ensure the smooth functioning of the entire research process. When all said and done, it's all about choosing the right option to succeed and save labour time and costs.

Here to stay

According to a recent report, the microplate reader market value will be worth US$ 704.4 million by 2027, up from US$ 534.5 million in 2019. In terms of growth, a CAGR of 3.6% is anticipated during 2020-2027. This growth is fuelled by rising research and development activities in the pharmaceuticals industry and the growing incidence of infectious diseases. The major dampener to this growth is the actual high cost of advanced microplate readers, but these rapid and highly specialised readers are in huge demand from companies in the biopharmaceutical and biotechnology sectors. 

Our friend Dr. Takatsy probably never imagined just how key his discovery, perhaps through pure serendipity, would be for us all today in our everyday coronavirus-affected lives. But now, just like then, maybe 'after the darkness comes the dawn'.