Our comprehensive line of reliable Microplate Readers deliver the versatility, sensitivity, precision, dynamic range and throughput you need to solve your complex analytical challenges. Every lab is unique. That's why you deserve a Microplate Reader that fits your needs. Maybe your research requires maximum application flexibility, or high throughput. Perhaps you are looking for simplicity, delivering reliable results. Whatever you need, there is a Berthold Technologies Microplate Reader to fit your research needs.
Types of microplate readers
There are several ways to classify microplate readers, but in the event of choosing or purchasing one, there are two important classifications: by detection technologies and by wavelength selection mechanism.
Microplate readers by detection technologies
There are two main types of microplate readers by detection technologies: dedicated microplate readers and multimode microplate readers.
Dedicated Microplate Readers
Dedicated microplate readers are able to measure one single technology only: either absorbance, luminescence or fluorescence. They lack the flexibility of multimode microplate readers, but they often offer better sensitivity and reliability than multimode microplate readers, and they are usually cheaper. For example, the Centro XS³ LB 960 Microplate Luminometer offers the best senstitivity in luminescence, unmatched even by the most sensitive multimode microplate readers.
Multimode Microplate Readers
Multimode microplate readers are able to use more than one detection technology. They are more complex than dedicated microplate readers, and some design compromises have to be made to accommodate all detection modes in a single instrument, but they offer great flexibility and, especially in advanced instruments with dedicated optical paths for each detection mode, such as the Mithras² LB 943 Multimode Microplate Reader have excellent performance in most applications.
Multimode microplate readers have been traditionally expensive, but some instruments offer a high modularity that allows the instrument to be configured only with the options that are really needed. The Tristar² and Tristar² S are excellent examples of modular multimode microplate readers.
For more information about the available detection technologies, see below.
Microplate Readers by Wavelength Selection
Another important characteristic when choosing a microplate reader is the system used to select the wavelength, as it has a major impact on many applications. The main options are filters, monochromator, and no wavelength selection.
Affordable microplate readers use normally filters to select the desired wavelength for any given detection method. Being the affordable option does not mean it is the worst one: filters have a very high transmittance and this brings a higher sensitivity in many applications. In addition, wavelength switching is very fast, a desirable feature in ratiometric assays. The main disadvantage is that you need a different filter for each wavelenght needed, and that reduces flexibility and makes it impossible to perform a wavelength scan.
On the other hand, monochromators provide total flexibility, not only in wavelength selection, but also in bandwidth selection. But, as mentioned, sensitivity in most applications is worse than when using filters.
Some microplate readers from Berthold Technologies offer you the best of both worlds: both the Tristar² S LB 942 and the Mithras² LB 943 can be configured with both filters and monochromators, so you can select the best option for your application.
No wavelength selection
Luminometers usually lack filters or any other way of wavelength selection: light of all wavelengths can potentially reach the photomultiplier. This provides the best sensitivity, but is a limitation for BRET, as this application requires to selectively measure light emitted by the donor and by the acceptor.
Berthold Technologies offers multimode as well as dedicated microplate readers for a wide range of detection modes:
- Time-Resolved Fluorescence (TRF)
- Fluorescence Polarisation (FP)
Both filter- and monochromator-based microplate readers are available. Find out more about the detection modes below:
UV/VIS Absorbance or Optical Density is used in countless classical colorimetric methods, ELISA, nucleic acid and protein quantification, and many others. The basic principle of absorbance measurements is described by Lambert-Beer's law.
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. Methods based on fluorescence offer better sensitivity, specificity and dynamic range than similar methods based on absorbance. Fluorescence is also involved in methods such as FRET and Fluorescence Polarisation (see below). Fluorescence measurements are performed very often using multimode microplate readers.
Luminescence is the result of a chemical or biochemical reaction. Thus, no excitation energy is required. Luminescence is most frequently used in methods involving reporter genes, ATP measurement and CLIA (Chemiluminescence Immunoassays). Other luminescence applications are caspase or kinase assays and ROS. Luminescence is usually measured using either microplate luminometers or tube luminometers.
BRET (Bioluminescence Resonance Energy Transfer) is based on the fact that the energy derived from a luciferase reaction can be used to excite a fluorescent protein if the latter is in close proximity to the luciferase enzyme, and is thus, an excellent tool to monitor macromolecular interactions. As many dedicated luminometers lack filters, multimode microplate readers are usually the instrument of choice for BRET measurements.
FRET (Fluorescence Resonance Energy Transfer) is a dual dye fluorescence detection assay. It requires a donor and an acceptor dye being in close proximity (10-100 Å). As a result of excitation, the donor fluorophore can transfer part of its energy to the acceptor fluorophore, e.g. YFP and starts emitting light without being directly excited. FRET is most frequently used to visualize molecular interactions of proteins and nucleic acids.
Fluorescence Polarisation (FP) is ideal to measure the binding of a small molecule to a much larger one. It is based on a fluorophore being excited by polarized light. Proteins and other large molecules in solution rotate slowly due to their size and emit polarized light when getting excited by polarized light. Small molecules on the other hand rotate faster and emit depolarized light. Thus, high levels of polarization indicate the presence of a larger molecule.
AlphaScreen® relies on hydrogel coated donor and acceptor beads providing functional groups for conjugation to biomolecules. When excited with a laser at 680 nm the donor bead produces singlet oxygen which transfers energy to the donor resulting in light emission between 520 and 620 nm. The amount of light produced is directly proportional to the amount of bound donor-acceptor beads. AlphaScreen® is a versatile method used to evaluate interactions between a binder (or a collection of binders) and a target (or a collection of targets). Only microplate readers equipped with a laser are suitable for AlphaScreen® measurements.
Time-Resolved Fluorescence (TRF) implies the use of fluorophores with a distinctive fluorescence lifetime to avoid the interference caused by molecules with a very different fluorescence lifetime or other factors (most importantly, excitation light). It uses long emission fluorophores (lanthanides) such as Europium or Terbium. TRF is used to elucidate molecular interactions, inter- or intramolecular distances, changes in the microenvironment, resolution of molecular mixtures, and more. A flash lamp or laser are the light sources of choice in any microplate reader to be used for Time-Resolved fluorescence measurements.
TR-FRET (Time-resolved fluorescence energy transfer) is a variant of FRET using long emission fluorophores (lanthanides) as donors. TR-FRET represents a powerful tool for drug discovery researchers. The resulting assay provide an increase in flexibility, reliability and sensitivity in addition to higher throughput and fewer false positive/false negative results. TR-FRET can be applied to detect the association of two molecules, for example to analyze receptor-ligand or protein-protein interactions.