Radiant energy – Ionic separation or analysis – With sample supply means
Reexamination Certificate
2003-04-30
2004-07-27
Wells, Nikita (Department: 2881)
Radiant energy
Ionic separation or analysis
With sample supply means
C250S281000, C250S282000, C250S42300F, C210S198200, C210S748080, C430S313000, C430S320000
Reexamination Certificate
active
06768107
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an integrated miniaturized fluidic system fabricated using microelectromechanical systems (MEMS) technology, particularly to an integrated monolithic microfabricated dispensing nozzle capable of dispensing fluids in the form of droplets or as an electrospray of the fluid.
BACKGROUND OF THE INVENTION
New trends in drug discovery and development are creating new demands on analytical techniques. For example, combinatorial chemistry is often employed to discover new lead compounds, or to create variations of a lead compound. Combinatorial chemistry techniques can generate thousands of compounds (combinatorial libraries) in a relatively short time (on the order of days to weeks). Testing such a large number of compounds for biological activity in a timely and efficient manner requires high-throughput screening methods which allow rapid evaluation of the characteristics of each candidate compound.
The compounds in combinatorial libraries are often tested simultaneously against a molecular target. For example, an enzyme assay employing a colorimetric measurement may be run in a 96-well plate. An aliquot of enzyme in each well is combined with tens of compounds. An effective enzyme inhibitor will prevent development of color due to the normal enzyme reaction, allowing for rapid spectroscopic (or visual) evaluation of assay results. If ten compounds are present in each well, 960 compounds can be screened in the entire plate, and one hundred thousand compounds can be screened in 105 plates, allowing for rapid and automated biological screening of the compounds.
The quality of the combinatorial library and the compounds contained therein is used to assess the validity of the biological screening data. Confirmation that the correct molecular weight is identified for each compound or a statistically relevant number of compounds along with a measure of compound purity are two important measures of the quality of a combinatorial library. Compounds can be analytically characterized by removing a portion of solution from each well and injecting the contents into a separation device such as liquid chromatography or capillary electrophoresis instrument coupled to a mass spectrometer. Assuming that such a method would take approximately 5 minutes per analysis, it would require over a month to analyze the contents of 105 96-well plates, assuming the method was fully automated and operating 24 hours a day. Even larger well-plates containing 384 and 1536 wells are being integrated into the screening of new chemical entities imposing even greater time constraints on the analytical characterization of these libraries.
Recent technological developments in combinatorial chemistry, molecular biology, and new microchip chemical devices have created the need for new types of dispensing devices. Applications in combinatorial chemistry require robust sample delivery systems that are chemically inert and distribute less than microliter amounts of liquid in high-density formats. The systems need to be highly reproducible and have overall quick dispensing times. Current dispensing technology utilizes serial injection schemes. The use of serial dispensers will be inherently limited due to their slows overall distribution times as the move to high-density formats progresses. For example, for combinatorial chemistry applications, to synthesize a library of 1 million discrete compounds, each composed of 4 monomers, a total of 4×106 dispensing steps would be required. If each dispensing step required 3 seconds (considering dispense time, rinsing, and, location positioning), the total time to dispense all of the reagents would be 12×106 seconds, or 3333 hours, or 139 days. Thus, for high-density formats, dispensing must be conducted in parallel. In order for parallel dispensing to work in high-density formats, the dispensing device must be small enough to allow all dispensing units to be simultaneously positioned within a corresponding receiving well. This requires the dispenser to be relatively small. As high density formats reach greater than 10,000 wells, dispensing devices will need to be spaced within 100 &mgr;m or less. In addition, in order for the dispenser to be practical, the device must dispense small quantities of liquid (10
−9
to 10
−12
L), and only require small volumes to operate.
Piezoelectric dispensing units have also been used for dispensing small amounts of liquid for microdevices. However, piezoelectric dispensers suffer from several problems. Currently, the closest spacing of individual dispensers is 330 &mgr;m in an array of four. Due to the current piezoelectric design and fabrication, the number of dispensers that can be positioned adjacent to one another is limited because of downstream device features. Additionally, sample requirements may be quite high even though the dispensing volume is small.
Enormous amounts of genetic sequence data are being generated through new DNA sequencing methods. This wealth of new information is generating new insights into the mechanism of disease processes. In particular, the burgeoning field of genomics has allowed rapid identification of new targets for drug discovery. Determination of genetic variations between individuals has opened up the possibility of targeting drugs to individuals based on the individual's particular genetic profile. Testing for cytotoxicity, specificity, and other pharmaceutical characteristics could be carried out in high-throughput assays instead of expensive animal testing and clinical trials. Detailed characterization of a potential drug or lead compound early in the drug development process thus has the potential for significant savings both in time and expense.
Development of viable screening methods for these new targets will often depend on the availability of rapid separation and analysis techniques for analyzing the results of assays. For example, an assay for potential toxic metabolites of a candidate drug would need to identify both the candidate drug and the metabolites of that candidate. An assay for specificity would need to identify compounds that bind differentially to two molecular targets such as a viral protease and a mammalian protease.
It would, therefore, be advantageous to provide a method for efficient proteomic screening in order to obtain the pharmacokinetic profile of a drug early in the evaluation process. An understanding of how a new compound is absorbed in the body and how it is metabolized can enable prediction of the likelihood for an increased therapeutic effect or lack thereof.
Given the enormous number of new compounds that are being generated daily, an improved system for identifying molecules of potential therapeutic value for drug discovery is also critically needed. Accordingly, there is a critical need for high-throughput screening and identification of compound-target reactions in order to identify potential drug candidates.
Liquid chromatography (LC) is a well-established analytical method for separating components of a fluid for subsequent analysis and/or identification. Traditionally, liquid chromatography utilizes a separation column, such as a cylindrical tube with dimensions 4.6 mm inner diameter by 25 cm length, filled with tightly packed particles of 5 &mgr;m diameter. More recently, particles of 3 &mgr;m diameter are being used in shorter length columns. The small particle size provides a large surface area that can be modified with various chemistries creating a stationary phase. A liquid eluent is pumped through the LC column at an optimized flow rate based on the column dimensions and particle size. This liquid eluent is referred to as the mobile phase. A volume of sample is injected into the mobile phase prior to the LC column. The analytes in the sample interact with the stationary phase based on the partition coefficients for each of the analytes. The partition coefficient is defined as the ratio of the time an analyte spends interacting with the stationary phase to the time spe
Corso Thomas N.
Schultz Gary A.
Advion BioSciences, Inc.
Holme Roberts & Owen LLP
Wells Nikita
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