Product
Review
Microplate Fluorometers Reach Critical Mass Whether you need an intensity reader or a multimode instrument, 96 wells or 1536, there's a microplate fluorometer for you . •
With the rapid spread of combinatorial and parallel screening methods, the drive to make assays better, faster, and smaller is becoming more intense. As a result, microplate (or microwell plate—both generic terms for Microliter plate) formats have become increasingly popular in big and small labs alike. In addition, recent advances have made a wider variety of ffuorescence assays available for a broader range of applications. "Fluorescence is really taking off because there'sfinallygotten to be a critical mass of instrumentation that's sensitive enough " says James Nelson of the instrument manufacturer Molecular Devices
tions and features of which are listed in Table 1. This review, although not comprehensive, describes some of the technical and practical considerations for potential buyers.
Types of fluorometers The simplest instruments measure fluorescence intensity and, in some cases, absorThese days, instruments can be as bance or luminescence too. Many accomplain or as fancy as you like—from basic modate anywherefrom6- to 384-well mii fluorometers that measure intensity to croplates; some handle the small-volume mid-range multimode readers to systems (10-20 uL) Terasaki plate as well. Most can optimized for high-throughput screening switch between reading platesfromthe top (HTS). But how do you decide which in(for solid-color plates) and reading from strument is right for you? Analytical Chemistry took a look at selected dommer- the bottom (for clear plates). Prices for these instruments generally stay below cially available products, the specifica$25 000. The mid-range fluorometers are generElizabeth Zubritsky al-purpose multimode readers for inten-
sity, time-resolved fluorescence, and, in some cases, polarization. There are two varieties: the more common filter-based instruments and the variable-wavelength monochromators. Monochromators are more flexible and, therefore, more expensive. Nonetheless, most mid-range instruments fall into the $25,000-$50,000 range. The third class of multimode readers consists of instruments designed for particular applications—usually, high-throughput screening (HTS) or calcium uptake assays. These systems often provide a relatively high degree of automation in addition to the ability to read intensity, time-resolved fluorescence, polarization, and luminescence. The exception is Packard Instrument's Discovery, which performs only special dual-wavelenth time-resolved fluorescence readings called Homogeneous
Analytical Chemistry News & Features, January 1, 1999 3 9 A
Product
Review
Table 1 : Summary of selected microplate fluorometers 1 Model
FL600
Fluoromark
FluoStar
MFX
FluoroMax-2
Fluoroskan Ascent FL
Manufacturer
Bio-Tek Instruments Highland Park Box 998 Winooski, VT 05404 800-451-5172
Bio-Rad Laboratories Life Science Group 2000 Alfred Nobel Dr. Hercules, CA 94547 800-424-6723
BMG LabTechnologies P.O. Box 11268 Durham, NC 27703 919-682-1228
Dynex Technologies 14340 Sullyfield Circle Chantilly, VA 20151 800-336-4543
Instruments SA 3880 Park Ave. Edison, NJ 08820 800-438-7739
Labsystems 8 East Forge Pkwy. Franklin, MA 02038 508-520-0009
URL
www.biotek.com
www.biorad.com
www.bmglabtechnologies.com
www.dynextechnologies www.isainc.com com
Fluorescence modes
Intensity
Intensity, time-resolved
Intensity, Intensity time-resolved, polarization (optional)
Intensity
Intensity
Compatible plates
1-384 wells; Teraski; PCR tubes
6-384 wells
Up to 1536 wells
6-384 wells
96 wells (with attachment)
1-864 wells; Teraski
Wavelengths: excitation emission
300-750 nm 350-850 nm
300-900 nm 300-900 nm
250-900 nm 250-900 nm
320-700 nm 360-800 nm
250-800 nm 250-850 nm
320-700 nm 360-800 nm
5 pg/well fluorescein
5 pg/well fluorescein 0.025 pmol fluorescein
0.2 pmol fluorescein
0.01 pmol fluorescein
Sensitivity (intensity mode) 5 decades
5 decades
7 decades
Read times
96 wells in 28 s
96 wells in 30 s
384 wells in 30 s
96 wells in 25 s
96 wells in 45 s
96 wells in 5 s
Light source
Quartz halogen lamp Xenon flash lamp
Xenon flash lamp
Quartz halogen lamp
Xenon arc lamp
Quartz halogen lamp
Filter capacity
6 excitation, 6 emission
8 excitation, 8 emission
8 excitation, 8 emission
no filters: monochromator
6 excitation, 6 emission
Robotics and automation capabilities
Compatible with third-party robotics including Beckman Biomek 2000, Zymark Twister plate stacker
Can be equipped with a stacker with an internal bar code reader
Compatible with full robotics or platestacking accessories
no
Available with assist robot, which handles up to 108 384-well plates
8 excitation, 8 emission
$27,000
$24,990
Price
$24,000
Software compatible with:
Windows 3.1, 95, or NT
Windows 3.1, 95, or NT
Windows 3,1, 95, 98, or NT
Windows 95
Windows 95
Other features
Absorbance and luminescence modes; auto software switching from topto bottom-reading; fast kinetics for Caz* uptake assays
UV option for wavelengths down to 250 nm; optional incubation; switching between top-and bottom-reading
Fast kinetics for uptake assays; instant switching between top- and bottomreading
Reads from top or bottom of plate; automatic gain control; narrowangle light beam reduces crosstalk
Top-reading; con- Reads from top or tinuous scanning bottom; also reads of spectra in all luminescence; wells: kinetics direct-reading optics do not use fibers or mirrors
Reader service number
401
402
403
404
405
Windows 3.1 or above
406
Several manufacturers offer instruments other than those shown. Contact the individual vendors for descriptions of their full product lines.
Time-Resolved Fluorescence (HTRF) measurements. Generally, the high-end instruments cost at least $100,000, but prices are significantly higher for those optimized for HTS, such as Molecular Device's FLIPR or LJL BioSystems's new Acquest, because they have the ability to handle 1536-well plates and have a very high degree of automation. 40 A
Which type to choose
Users who run primarily ELISA-type assays probably need only an intensity reader for their current work, but it is a good idea to plan for the future. Laurence Demers at Pennsylvania State University recommends buying a machine that reads both fluorescence and luminescence because some of the assays that have used
Analytical Chemistry News & Features, January 1, 1999
fluorescence are being converted to chemiluminescence. According to Keith Moore at SmithKline Beecham, buying'a machine that reads time-resolved fluorescence or polarization might make sense because some fluorescence intensity assays are being replaced by the more advanced ones. Still, the experts say, basic fluorescence is not on its way out. All
SPECTRAFIuor Plus
Victor2
Perkin-Elmer PE Biosystems 761 Main Ave. PerSeptive Biosystems Norwalk, CT 06859 500 Old Connecticut 800-762-4000 Path Framingham, MA 01701 800-899-5858
Tecan P.O. Box 13953 Research Triangle Park, NC 27709 919-361-5208
Wallac 9238 Gaither Rd. Gaithersburg, MD 20877 800-638-6692
www.packardinst. com
www.perkin-elmer. com
www.pbio.com
www.tecan.com
www.wallac.fi
Intensity, time-resolved
Intensity
Intensity, time-resolved
Intensity
Intensity
Intensity, time-resolved
6-384 wells
6-384 wells
6-1536 wells;
6-384 wells; Terasaki
6-1536 wells
Analyst
SPECTRAmax Gemini
LJL BioSystems 404TasmanDr. Sunnyvale, CA 94043 888-611-4555
FluoroCount
HTS 7 0 0 0 Plus
Molecular Devices 1311 Orleans Dr. Sunnyvale, CA 94089 800-635-5577
Packard Instrument 800 Research Pkwy. Meriden, CT 06450 800-323-1891
www.ljlbio.com
www.moldev.com
Intensity. time-resolved, polarization
96 or 384 wells
CytoFluor
Terasaki
6-864 wells; Terasaki
250-900 nm 320-720 nm
250-850 nm 250-850 nm
340-650 nm 340-670 nm
230-700 nm
300-700 nm
230-700 nm
340-700 nm
(in 100uL)
