Chemistry: analytical and immunological testing – Optical result – With claimed manipulation of container to effect reaction or...
Reexamination Certificate
2000-09-19
2003-07-01
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Optical result
With claimed manipulation of container to effect reaction or...
C436S164000, C359S196100, C359S197100, C359S202100
Reexamination Certificate
active
06586257
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to devices and methods for rapidly identifying chemicals with biological activity in liquid samples, particularly automated screening of low volume samples for new medicines, agrochemicals, or cosmetics.
2. Description of the Related Art
Drug discovery is a highly time dependent and critical process in which significant improvements in methodology can dramatically improve the pace at which a useful chemical becomes a validated lead, and ultimately forms the basis for the development of a drug. In many cases the eventual value of a useful drug is set by the timing of its arrival into the market place, and the length of time the drug enjoys as an exclusive treatment for a specific ailment.
A major challenge for pharmaceutical companies is to increase the speed and efficiency of this process while at the same time minimizing costs. One solution to this problem has been to develop high throughput screening systems that enable the rapid analysis of many thousands of chemical compounds per 24 hours. To reduce the otherwise prohibitive costs of screening such large numbers of compounds, typically these systems use miniaturized assay systems that dramatically reduce reagent costs, and improve productivity. To efficiently handle large numbers of miniaturized assays it is necessary to implement automatic robotically controlled analysis systems that can provide reliable reagent addition and manipulations. Preferably these systems and the invention herein are capable of interacting in a coordinated fashion with other systems sub-components, such as a central compound store to enable rapid and efficient processing of samples.
Miniaturized high throughput screening systems require robust, reliable and reproducible methods of analysis that are sensitive enough to work with small sample sizes. While there are a large number of potential analysis methods that can successfully be used in macroscopic analysis, many of these procedures are not easily miniaturizable, or lack sufficient sensitivity when miniaturized. This is typically true because absolute signal intensity from a given sample decreases as a function of the size of the sample, whereas background optical or detector noise remains more or less constant for large or small samples. Preferred assays for miniaturized high throughput screening assays have high signal to noise ratios for very small sample sizes.
Fluorescence based measurements have high sensitivity and perform well with small samples, where factors such as inner filtering of excitation and emission light are reduced. Fluorescence based measurements therefore exhibit good signal to noise ratios even with small sample sizes. A particularly preferred method of using fluorescence based signal detection is to generate a fluorescent (emission) signal that simultaneously changes at two or more wavelengths. A ratio can be calculated based on the emission light intensity at the first wavelength divided by the emitted light intensity at a second wavelength. This ratiometric measurement of a fluorescent assay has several important advantages over other non-ratiometric types of analysis. Firstly, the ratio is largely independent of the actual concentration of the fluorescent dye that is emitting fluorescence. Secondly, the ratio is largely independent of the intensity of light with which the fluorescent compound is being excited. Thirdly, the ratio is largely independent of changes in the sensitivity of the detector, provided that is that these changes are the same for the detection efficiency at both wavelengths. This combination of advantages makes fluorescence based ratiometric assays highly attractive for high throughput screening systems, where day to day, and, assay to assay reproducibility are important.
Traditionally, there are two general ways to read fluorescence from a multi-well plate. In one arrangement, a read head is moved from well to well and at each well, there is a dwell time during which the fluorescence signal is digitized and stored into memory. Optically, this scheme is the simplest. There is only one optical assembly, one set of filters and one detector. However, depending on how many wells there are in the plate, the read time can be unacceptably long. It is not just the dwell times that contribute to the total read time. Every time the read head is moved from well to well, it takes time to accelerate and decelerate the stage used in moving the setup.
In the other arrangement, some sort of parallelism is employed. Either a picture is taken of the plate, using a CCD camera or some other imaging arrangement, or multiple optical read heads are employed. The advantage of this arrangement is a significant reduction in the read time. However, a new difficulty is introduced, namely that of normalization. When several wells are read at the same time by several read heads, the question that arises is how to make sure that these heads behave in the same way in terms of collection efficiency, detector sensitivity, filter quality and the like. In the case of a CCD camera, the analogous issue is one of flat-fielding. Accordingly, improved methods and systems for rapidly and accurately measuring fluorescence signals in high throughput screening environments are needed.
SUMMARY OF THE INVENTION
In one embodiment, a method in accordance with the invention comprises placing a platform on a detector for detecting sample attributes, wherein the detector has an adjustable parameter. The method includes making a plurality of measurements of a characteristic of the platform to obtain a plurality of measured values of the characteristic at different locations on the platform. The attributes are measured with the detector with the parameter adjusted based upon the measured values.
In one embodiment, the platform is a multi-well plate, the characteristic comprises a bottom contour of the multi-well plate, and the adjustable parameter comprises the distance between an optical detector and the multi-well plate bottom. In some of these embodiments, to maintain the optimal distance between the optics and the plate, the detector is provided with a sensor used to detect the location of a plate element of interest. In addition, the optics are mounted on an optics positioning device, for example a linear stage. In one embodiment, the optics positioning device may be oriented in the vertical axis so that the vertical position of the optics may be adjusted relative to the plate. Alternative to adjusting the optics, the plate positioner may be mounted on a stage oriented in the vertical axis and the plate may be moved to adjust the relative position of the plate and optics. The optics positioning device is slaved to the stages on the plate positioner which controls the horizontal position of the plate relative to the optics.
The method of reading a microplate while compensating for plate variations comprises first mapping the topology of the plate element of interest, for example the elevation of the plate bottom relative to the optics. The plate is moved relative to the sensor along all or a representative portion of the plate element of interest. The plate may be moved in any desired pattern which covers the desired area, but is preferably moved in a raster scan. As the plate is moved, the sensor measures the location of the plate element of interest. From these measurements a contour map of the plate element of interest may be computed which describes the plate topology. After the mapping is complete, the scanner reads the plate. During the reading scan, the optics positioning device adjusts the positioning of the optics based upon the mapped plate topology to maintain the desired distance between the optics and the critical plate element. For example, the optics positioning device may adjust the distance between the optics and the bottom of the plate to maintain a substantially constant distance between the optics and the bottom of the plate as each of the wells is scanned. In some advantageous embo
Gakh Yelena
Knobbe Martens Olson & Bear LLP
Vertex Pharmaceuticals Incorporated
Warden Jill
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