Automated micro-volume assay system

#This invention generally relates to an assay system for assaying volumes of biological substances of microliter sizes and smaller and, in particular, to a micro-volume assay system which is automated.

#A number of methods and systems have been developed for conducting various processing and/or analyses of biological substances, such as those described in U.S. Pat. No. 6,423,536 for temperature cycling processes, U.S. Pat. Nos. 5,843.680, 5,784,154, 5,395,502, and 5,137,609 for separation assay methods, U.S. Pat. No. 5,785,926 for a capillary transport system, international publication WO94/13829 for an isoelectric focusing separation assay system, and U.S. Pat. No. 6,430,512 for a chromatographic fluorescence separation and display system.

#U.S. patent application Ser. No. 60/589,139, filed Jul. 19, 2004 and entitled “CONTINUOUS DETERMINATION OF CELLULAR CONTENTS BY CHEMILUMINESCENCE”, U.S. patent application Ser. No. 60/617,362, filed Oct. 8, 2004 and entitled “DETERMINATION OF CAPTURED CELLULAR CONTENTS”, and U.S. patent application Ser. No. 11/185,247, filed Jul. 19, 2005 and entitled “METHODS AND DEVICES FOR ANALYTE DETECTION”, and U.S. patent application Ser. No. 10/139,100 entitled MICROFLUIDIC DEVICE FOR ANALYZING NUCLEIC ACIDS AND/OR PROTEINS, METHODS OF PREPARATION AND USES THEREOF, the disclosures of all of which are incorporated herein by reference, all describe apparatus and methods for assaying microliter volumes of cellular material by separating constituent substances of the material in a fluid chamber such as a capillary, binding the separated substances in place, then eliciting an optical response from the bound substances such as fluorescence or chemiluminescence. The resulting information has content similar to that of a Western gel blot but without the complex, extensive and time-consuming handling and processing steps that adversely affect reproducibility and make automation difficult. This technique also has advantages such as the ability to assay very small volumes of materials such as those on the cellular level, and good sensitivity due to the ability to receive optical data from chemiluminescence for as long as necessary to obtain a desirable output signal level. However, it would be desirable to automate this technique so that multiple samples may be analyzed simultaneously or in rapid succession with ease and robustness while only consuming minimal volumes of precious reagents and expensive disposables. Thus, further developments are needed.

#Other objects and advantages of the invention become apparent upon reading of the detailed description of the invention and the appended claims provided below, and upon reference to the drawings, in which:

#FIGS. 1 and 2 are front perspective views of an immunoassay system constructed in accordance with principles of the present invention.

#FIGS. 3a, 3b, 3c and 3d illustrate capillary holders constructed in accordance with the principles of the present invention.

#In accordance with the principles of the present invention an assay system is presented. In some embodiments, the system of the present invention is configured to provide the functionality of both pipettes and fluid paths for analysis in a single system. This enables analysis of very small volume samples, and among other advantages improves overall fluid consumption as well as simplifying automation and improving robustness.

#Referring first to FIGS. 1 and 2 a immunoassay system 10 constructed in accordance with principles of the present invention is shown in a perspective view. In the illustrative embodiment, the system 10 is mounted on a baseplate 12 with a surface suitable for wipe down if biohazardous materials are processed though the system (e.g., stainless steel or plastic). Shown on the baseplate 12 are a pair of bottles 14 which contain bulk fluids. Clean wash fluid is pumped for use from one bottle while all system waste fluids are pumped into the other bottle. Toward the back of the baseplate 12 is a detection module 16. The detection module 16 houses a movable tray 17 with a space 20a for a capillary holder 20′(shown in FIG. 3a) and an intermediate holder 20″ (shown in FIG. 3e). The movable tray 17 is automated to slide into and out from the detection module in the manner of a disk tray of a computer optical disk drive to transport the capillary holders into and out of the module 16. The detection module houses an imaging optical detector for detecting light emitted from within the capillaries. In this embodiment the optical detector is a cooled charge-coupled device (CCD) array detector. Light from the capillaries is imaged onto the CCD by a lens assembly. The detection module is light-tight when the tray 17 is retracted to the interior of the module, enabling the CCD array detector to detect light emitted from a capillary by chemiluminescence or fluorescence. To excite fluorescence an array of light emitting diodes inside the detection module is arranged to uniformly illuminate the capillaries. Alternatively, a laser or other light source could be used for excitation. Wavelength-selective filters are used to prevent excitation light, emitted from the light emitting diodes, from interfering with detection of the fluorescent emissions. For chemiluminescent detection a material such as luminol is flowed through the capillaries by hydrodynamic flow as described below and the emitted photons are detected by the CCD array detector. In an alternative embodiment luminol may be electrically pumped through the capillaries by application of voltage across the capillaries with hardware similar to that described in the section below for isoelectric focusing. During detection the capillary is held in a capillary holder 20′ on the tray 17 which is retracted into the detection module and moves out again after photodetection is completed. The detection process may take from seconds to hours depending on the level of sensitivity desired.

#As referred to herein, the term capillary or capillaries is meant to include any device that has one or more internal tubes or bore with a small dimension. The internal tube(s) can have any suitable shape, and for example may be circular, square, triangular, and the like. The term capillary or capillaries include multiple internal tubes, and for example include microfabricated devices that contain internal channels as the tubes. Generally, the internal tube(s) have any suitable dimension. In some embodiments the dimension of the internal tube(s) is in the range of 1 micron to 2000 microns. In other embodiments, the dimension of the internal tube(s) is in the range of 25 microns to 250 microns. In some embodiment, the length of the internal tube(s) is in the range of 30 mm to 100 mm. The external size and shape of the capillaries are not limited.