Microplate Luminometer

Basic information about microplate luminometers

A microplate luminometer is a piece of equipment capable of detecting the light photons emitted by chemical, bio-chemical or enzymatic reactions in a microplate and quantify them. Luminescence detection is not an absolute measurement, like absorbance. The intensity of the signal is usually relative to other samples or to a reference measurement taken by an instrument. Consequently, luminometers quantify the light signal emitted by a sample in Relative Light Units (RLU).

A luminometer able to measure samples present in a microplate is usually referred to as a microplate luminometer.

Luminometers are used for different applications in various fields, such as academic life science research, drug discovery and screening, clinical laboratories, synthetic biology and food or water quality monitoring. Most common applications include cell viability, reporter gene assays and mycoplasma contaminations.

What is a microplate luminometer?

Microplate luminometers are quite simple instruments, optically speaking, when compared to fluorescence readers. Because of the nature of the luminescent signal or assay, microplate luminometers require neither an excitation light source, nor optics for excitation wavelength selection (as needed for absorbance or fluorescence detection). They just require a reading chamber, an optical system for bringing the light signal from the sample to the detector, a detector (photomultiplier tube, PMT) and possibly an optical system for the selection of luminescent (emission) wavelengths.

If you are on the market for a new luminescence reader, there are a few factors to take into account, as the performance of the instrument can significantly affect the quality of your assay results.

Sensitivity

The luminescent signal is typically generated by a bio-chemical or chemical reaction and does not require excitation light. Consequently, it generally offers high sensitivity when compared to absorbance or fluorescence. The unspecific background or noise signal is extremely limited when compared to fluorescence intensity, since there is no excitation process that can trigger light scatter or autofluorescence from both the sample and the microplate.

Nevertheless, a sensitive microplate luminometer with superior luminescence assay performance will deliver assay data with a better statistic, less variability among replicates, and a larger delta (distance) between responding and not-responding samples. In addition, high sensitivity will allow you to reduce the amount of reagents and/or samples used to achieve good quality data and consequently reduce costs.

Dynamic range

Luminescent reactions in microplates are usually based on the addition of a substrate to the wells to start an enzymatic reaction. Once the reaction is started and the amount of substrate is metabolised by the enzyme, the reaction is exhausted and cannot be retriggered again, unless new detection reagents and samples are used in a fresh microplate. Consequently, it is imperative to acquire the signal of all samples that have to be measured at once on the microplate. This avoids the risk of having to repeat the assay and to consume more reagents.

If you have samples spanning over a large range of signal intensities on a single microplate, it may be difficult to acquire them all in one measurement with one setting. Very strong signals may saturate the detector of the microplate luminometer. Very weak bioluminescence experimental samples may be undiscernible from the blanks.

Having a broad dynamic range allows your luminescence reader to acquire highly divergent samples (bright samples and dim samples) in one run on a single microplate, avoiding waste of reagents and time caused by multiple trial-and-error measurements to find the correct dilution-gain-integration time ratio. The Enhanced Dynamic Range feature on the PHERAstar FSX, CLARIOstar Plus and VANTAstar offers the largest possible dynamic range on the market (8 concentration decades), and makes it possible to automatically measure very bright and dim signals in the same microplate in one run– easy to use and no adjustment required.

Wavelength selection

This capability (with filters or monochromators) in luminescence readers is not mandatory (as for absorbance or fluorescence detection), especially when detecting a basic assay. However, depending on the application and especially for luminescent assays with multiple signals, the possibility to select the emission from a wavelength range is beneficial. Filters or monochromators can be employed for this purpose. This option is useful when developing new assays or detecting multiple luminescent signals. Moreover, it helps to optimise the assays by reducing background noise.

Filters are usually more sensitive, whereas monochromators offer more flexibility. An exception to this paradigm is the Linear Variable Filter (LVF) MonochromatorTM system available on the CLARIOstar Plus and the VANTAstar. LVF Monochromators have filter-like performance and make the CLARIOstar Plus the most sensitive monochromator based plate reader on the market. LVF Monochromators can be used in fluorescence intensity and luminescence detection. Moreover, monochromators have the capability to acquire scans and offer extra fexibility for assay development.

Compatible microplate formats

Commonly, basic luminescent assays are measured in 96-well plates. However, if you have multiple samples, have high-throughput needs, and/or wish to save precious reagents or time, 384-well and 1536-well formats can also be used and require less µL fill volume. Just make sure that your instrument of choice is also capable of reading the microplate format you plan on using. Moreover, absorbance, fluorescence, and luminescence detection require different plate types. Light cross-talk should also be considered when using high-density microplates.

Light cross-talk

Light cross-talk is mainly related to luminescence detection and happens when during the quantification of a well, the light signal from the adjacent wells on a microplate is also picked up by the detector. This leads to adulterated results. Cross-talk is specifically a factor when working with high-density plates (384-wells and higher), negligible crosstalk is present in 96-well plates instead. There are two ways by which cross-talk light can be picked up by the detector, either from the top of the well or through the plastic wall of the microplate.

High-end instruments such as the CLARIOstar Plus, the VANTAstar and the PHERAstar FSX can compensate this factor by physically blocking the light coming from the neighbouring wells. Specific algorithms can calculate the amount of light transmitted through the plastic wall and subtract it from your samples to deliver a more robust performance.

Glow and flash luminescence

When looking for a microplate luminometer, you should consider the nature of the assays you want to run. According to their kinetic, luminescent assays can be divided in flash and glow reactions. Flash reactions are short-lived and give off a very bright signal for a very short amount of time, usually seconds. Glow reactions are rather long-lived. The reaction can last for several minutes, but usually emits a less intense signal.

Any microplate luminometer can detect glow reactions. Flash assays require instead the use of reagent injectors. By manually pipetting reagents into the wells of a microplate you can run the risk of losing the peak of your reaction as the short-lived signal could already be exhausted before you detect it. Our instruments equipped with reagent injectors can automatically inject and detect the signal of a well and then move to the next one.

Dual luciferase reporter assays

Reagent injectors are also beneficial for Dual Luciferase Reporter (DLR) assays. Here, the activity of two luciferases (renilla and firefly luciferase) is sequentially measured from a single sample and reports the transcription of a gene of interest and a transfection control. Both reporter gene assays can be completed in about 4 seconds using an instrument with reagent injectors.

Bioluminescence Resonance Energy Transfer (BRET)

Additionally, the capability of detecting two emission channels simultaneously is quite beneficial for BRET and NanoBRET assays. This option halves measurement time and reduces data variability. Simultaneous Dual Emission (SDE) detection is available on the LUMIstar Omega and on the PHERAstar FSX.

Our microplate luminometers

Luminescent detection can be performed on BMG LABTECH´s dedicated microplate luminometer LUMIstar^® Omega, and multi-mode readers including the PHERAstar^®FSX, CLARIOstar^®Plus, VANTAstar^®and FLUOstar^® Omega.

All of our microplate luminometers are certified for Dual-Luciferase Reporter assays utilize optimized low-noise PMT (photomultiplier tube) and can be equipped with high-precision reagent injectors.

PHERAstar FSX

Powerful and most sensitive HTS plate reader

CLARIOstar Plus

Most flexible plate reader for essay development

VANTAstar

Flexible plate reader with simplified workflow

Luminescence plate reader FLUOstar Omega

Omega Series

Upgradable single and multi-mode plate reader series

Which assays can be measured by a microplate luminometer?

Both a single- or multi-mode device (incl. for instance absorbance and fluorescence, TRF and AlphaScreen detection) can cover a wide range of basic luminescence technologies including all Promega bioluminescence assays, enzymatic reactions, biochemical assays, gene expression by Dual Luciferase Reporter gene (DLR), luminescent calcium flux and chemiluminescent ELISAs.

Microplate luminometers are also useful for analysing cell cultures for cell viability (ATP-based), cytotoxicity and apoptosis, signalling pathways and metabolism. Mycoplasma contamination in cells can also be measured.

Even proximity or protein-protein interaction assays can be measured by BRET and nanoBRET assays.

BRET is a dual reporter detection assay based upon resonance energy transfer between a bioluminescent donor and a fluorescent acceptor. As the donor emits photons by bioluminescence, excitation is dispensable.

Examples for luminescent measurements:

The following are examples of luminescence measurements made on BMG LABTECH readers:

See a complete list of luminescence application notes.

Why to choose BMG LABTECH?

BMG LABTECH is specialized in producing microplate readers only and brings 30 years of full expertise in microplate reading technology. This knowledge gets visible in the results that our instruments deliver - the only factor that counts in your lab! BMG LABTECH users can trust to receive best results in sensitivity, speed and flexibility. Moreover, our instruments are developed to provide optimum performance for years. Our instruments are developed, produced and tested in Germany and are built to be extremely robust and reliable.

Buy only what you need

Due to their modularity, all our readers can be equipped with different detection modes and cover a multitude of applications. Additional features can be upgraded at any time. This gives you the chance to keep your options open even if you don’t use the full scope of your instrument right at the bat.

All-round service and support

At BMG LABTECH we strive to provide you with the very best customer service. If you need customer support, we are only a phone call or email away. During business hours, you immediately speak live to a person who is happy to assist. There is no automated phone system or waiting in a queue, our scientists, engineers and technicians are always there to help.

Multi-user integrated software package

All our instruments come with a multi-user software package that can be installed on as many computers as users requires, without the need to purchase licenses. Software updates are of no charge within the first 12 month after purchase.

Microplate luminometer