Microplate Readers Buying Guide
What should you think about when considering a microplate reader purchase for your laboratory? Maybe you are looking for an upgrade for a specific capability, application or mode. Or perhaps you are a first time buyer of a microplate reader and need to know what is useful and what is not. This guide provides important information to help you make the right purchasing decision.
Learn about the different types of readers; their read modes, applications, technologies and other important considerations.
Introduction to Microplate Readers
Microplate readers are used to detect biological, chemical or physical events in microtiter plates via the measurement of light. They are the key workhorses in many laboratories and are extensively used for many applications across a wide range of disciplines, including life sciences, basic research, target discovery, lead discovery, bioassay validation, quality control, drug safety, toxicity testing and biopharmaceutical/pharmaceutical manufacturing processes.
Although part of a well established product category, microplate readers are continuing to evolve towards greater functionality, flexibility, speed and throughput. There is a wide variety of microplate readers on the market, each offering different capabilities and functionalities.
Microplate readers largely differ by the type of detection mode they offer. Common detection modes include absorbance, fluorescence and luminescence. Some readers may also include additional detection modules, such as those for fluorescence resonance energy transfer (FRET), time-resolved fluorescence (TRF) , the variant TR-FRET, fluorescence polarization, bioluminescence resonance energy transfer (BRET), AlphaScreen and nephelometry.
Microplate readers also differ by the technology used in these detection modes. Absorbance measurements can be performed with filters, monochromators or a spectrometer. Filter- and monochromator-based instruments capture one wavelength at a time, while the newer spectrometer-based readers capture an entire spectrum of wavelengths. Fluorescence measurements can be performed with filters or monochromators. Filters offer great sensitivity, monochromators offer great flexibility, and new linear variable filter monochromators offer the best of both. Lastly, lasers can be used instead of a flash lamp for better performance in time-resolved fluorescence and AlphaScreen measurements. But be aware that different technologies may be used for the different detection modes in the different microplate readers.
Microplate readers can be purchased as either single-mode or multimode; the latter combines several read modes in one instrument. Multimode microplate readers enable researchers to perform multiple assay types in one system. Inevitably, multimode readers are typically more expensive than single-mode readers, but purchasing one multimode reader is likely to be more cost-effective than buying several dedicated machines. In addition, they do not consume much more bench space than a single reader and are often modular and upgradable, allowing a laboratory to purchase only what they need at the time.
Consider your Applications
When choosing a microplate reader, the first, and perhaps the most important, consideration is what application(s) will be measured? Microplate readers are used for numerous applications across a wide range of disciplines.
If you work within a life science, basic research or drug discovery laboratory, you may be using a microplate reader for applications such as:
- Enzyme-Linked Immunosorbent Assay: ELISA is an immunodetection assay for the identification of specific antigens in samples. Horseradish peroxidase (HRP) is typically conjugated to the secondary antibody to detect the binding of antibody to the antigen of interest. A chromogenic substrate for HRP, such as tetramethybenzidine hydrochloride (TMB), which absorbs visible light at 450 nm, is used to detect binding. ELISA is used widely in life sciences but also in pre-clinical testing for drug development.
- Protein and Nucleic Acid Quantification: DNA and RNA absorb light efficiently in the UV range. Quantitation of nucleic acid occurs at 260 nm. Purity can be determined by measuring both at 260 nm and 280 nm as protein absorbs at 280 nm. Protein is a common contaminate in DNA and RNA preparations.
- Kinetics: Enzyme kinetics is an important aspect of enzymology. The use of a chromogenic substrate allows for the determination of enzyme kinetics, such as the Michaelis-Menten constant and the rate of a reaction.
- Protein Assays: A variety of commercially available kits allow for measuring the amount of total protein in a sample. Reagents that change color linearly in response to the amount of protein in the sample are typically used. Commonly used assays include bicinchoninic acid (BCA), Lowry and Bradford.
- Cell Density: An important aspect of preparing bacterial cultures is to determine the growth phase before harvesting the cells. Measurement of optical density (O.D.) at 600 nm allows for this determination.
- Cell Viability, Proliferation and Cell Death: There are many different commercially available cell-based assay kits that enable cell viability, proliferation and apoptosis to be measured. These include those for monitoring ATP, measuring caspase activity and detecting bromodeoxyuridine (BrdU). Cell based assays are crucial in the early stages of disease research and identification of potential protein pathways. They are also used in toxicity testing in pre-clinical drug development.
- Fluorescent Protein Assays: EGFP, YFP, mCherry, tdTomato and the many other variants of GFP can be used to measure a variety of real-time cellular-based activities, including: intracellular transport, protein signaling, receptor desensitization, cell movement, migration, division, apoptosis, metabolism, differentiation, chemotaxis, transcription and translation.
- Gene Expression: Reporter genes, such as luciferase, are important tools for studying gene expression. The use of reporter genes allows the in vitro and in vivo measurement of gene expression from virtually any endogenous genetic control element. Luciferase enzyme and its subsequent luminescent reaction is often the gene reporter of choice for many experimental conditions.
If you work in a target or lead discovery laboratory, high content screening (HCS) of protein targets and high throughput screening (HTS) of compounds are likely to be key application areas. For such applications, speed and sensitivity are of major importance. Consequently, several multimode microplate readers have been designed specifically for HTS and HCS applications. The ability to measure all wells of a microplate at once is a factor to consider alongside reliability, sensitivity and consistency, which are essential for high throughput. There are several assay technologies that have been developed specifically for screening applications, which include:
- AlphaScreen: AlphaScreen (Amplified Luminescent Proximity Homogeneous Assay Screen) is a versatile assay technology developed to measure analytes using a homogenous protocol. It enables the highly sensitive and precise interrogation of various signaling pathways, receptors and kinase targets, and the measurement of full-length, endogenous protein phosphorylation in a cell-based format. A wide variety of applications for AlphaScreen have been reported. It is especially ideal for screening GPCRs and growth factor receptors, and for screening intracellular kinase inhibitors of MAPK and other signaling pathways.
- HTRF: Utilizing rare-earth lanthanides with long emission half-lives as donor fluorophores, Homogeneous Time Resolved Fluorescence (HTRF) technology combines standard FRET with the time resolved measurement (TR) of fluorescence. HTRF is commonly used for GPCR and kinase screening, two of the most important target classes investigated within drug discovery. Other HTRF applications include discovery of new biomarkers, studies of protein-protein interactions, epigenetics and an alternative method for bioprocess monitoring.
Microplate readers are used for many more applications, and as technologies evolve even more applications will emerge. When purchasing a microplate reader, it is important to establish what applications you will be using it for; you will need to ensure that your chosen microplate reader is capable of fulfilling all of your requirements. In addition, you will need to consider any future applications and the needs of any other users of the instrument.
General and Future Considerations
Try it Out
Once you have considered both your application needs and the different technologies that are available, the chances are you will have narrowed down the choice to just a few microplate readers. Before going ahead and purchasing a microplate reader, it is highly recommended that you try it out. Most manufacturers will let you demo the instrument for a trial period of time and it is important to use this time wisely to ensure the instrument is capable of fulfilling all of your requirements.
Technical Support and Warranty
Consider the extent of the technical support and training that is available from the manufacturer at the point of purchase. It is also recommended that you look into the company’s policy on after-sales service and standard warranty. While everything is operating well, this may be the last thing on your mind, but in the event that after-sales support is required, it is important to know how this will be achieved.
Is it Included with the Reader?
Not all microplate readers have the same standard features. Make sure to ask what is included with the reader at the time of demonstration. Optional items can include: computers to run the instrument, filters or filter cubes, software licenses, software upgrades, FDA compliant software or injectors.
It is essential to consider current and future trends to maximize the lifespan of your microplate reader. As systems become more sophisticated, integration, convenience and application specificity will be fundamental. Systems will become faster and more efficient and will be able to run a larger variety of different assays.
Application possibilities will increase as manufacturers work to provide solutions to individual and industry demands, such as those currently being requested in the food/beverage and biofuels industries, as well as in emerging countries. Manufacturers are taking into consideration customer feedback and requirements, with many developing strategies for even greater specificity assays and technology for the future.
Whether purchasing a microplate reader for a new application, or replacing an existing system, there are a number of factors to consider. You will need to examine your current and future application needs and determine which of the available technologies best suits these applications.
Visit the SelectScience product directory for an overview of the latest microplate readers from leading manufacturers and read hundreds of user reviews. Keep up to date with the latest microplate reader techniques by visiting the SelectScience application note and video libraries.
Drug Discovery & Development Editor
"It is very easy to use and produces high quality images…”
Sunil Rangarajan, University of Alabama at Birmingham
“This multi-functional equipment is sturdy, durable, and reliable in accuracy…”
Hemant Vyas, Texas Biomedical Research Institute
To help you choose the correct system, use the SelectScience product and supplier directory for an overview of systems from leading manufacturers and read user reviews from other SelectScience members.