Reaction receptacles or test tubes are commonly used in the chemical and biological arts to perform a variety of types of assays in a contained space. Assays that commonly have one or more steps performed in reaction receptacles include chemical reactions, immunoassays, and nucleic acid-based assays. Examples of such reactions and assays are thoroughly described in the available literature and are well known to those skilled in the art. While reaction receptacles are generally manufactured and sold as individual units or test tubes, it is common for practitioners to use holding racks to conveniently and collectively organize a group of reaction receptacles for performing multiple assays simultaneously or sequentially. In some instances, multiple reaction receptacles are assembled as a unitary piece.
With most assays, a substance transfer device is used to dispense solutions into or remove solutions from reaction receptacles. The most familiar substance transfer devices are pipettes and aspirators including one or more tubular elements through which fluids are dispensed or withdrawn. When substance transfer devices are used in conducting a group of independent assays at about the same time or in close proximity to one another, there is always the concern that a substance transfer device will inadvertently serve as a vehicle in transferring substances or contaminants between reaction receptacles. An additional concern is that the practitioner will improperly add substances into or remove substances from a reaction receptacle. To minimize the risk of cross-contamination and pipetting and aspirating errors, practitioners must carefully monitor substance transfers and exercise nearly flawless precision when pipetting substances into or aspirating substances from reaction receptacles. Avoiding cross-contamination and pipetting and aspirating mistakes is particularly important when the assay is diagnostic in nature or is designed to provide information concerning the progress of a patient's disease over time or the success of a treatment regimen.
One way to limit opportunities for cross-contamination is to reduce the amount of surface area on the substance transfer device that can come into contact with the contents of a reaction receptacle. This objective can be achieved by using a contact-limiting element, such as a pipette tip, which essentially serves as a barrier between the outer surface of the pipette and the contents of a reaction receptacle. And by selecting a pipette tip of sufficient length and volume, contact between the pipette and contents of a reaction receptacle can be substantially eliminated. This is because substances from the reaction receptacle will be drawn into a portion of the pipette tip which falls below the bottom surface of the pipette. Of course, in most instances, it will also be important to have a single pipette tip dedicated to each reaction receptacle.
Where a number of pipette tips are used to perform multiple assays simultaneously or sequentially, practitioners typically need to position a supply of pipette tips at a location that can be conveniently accessed by at least one pipette. Providing a sufficient quantity of pipette tips becomes more complicated when the substance transfer device functions robotically in an automated (or partially automated) assay instrument. In an automated format, a large reserve of pipette tips may need to be placed in the instrument at a site that is accessible by the pipette, but which limits the total amount of space required. Accordingly, there is a need for pipette tips that are readily accessible by a robotic pipette without requiring the pipette to engage in complicated movements or to travel over substantial distances.
Another problem presented by conventional reaction receptacles is that they come packaged as individual test tubes that are not amenable to manipulation by an automated assay instrument. Individual reaction receptacles hinder throughput efficiency since the practitioner and instrument must each handle the reaction receptacles separately. And because conventional reaction receptacles are not provided with any structure that permits them to be manipulated by an automated instrument, reaction receptacles are generally stationed at one situs within the instrument and are not afforded any automated mobility. This lack of movement imposes certain architectural limitations and assay inefficiencies since the instrument must be designed around the positioning of the reaction receptacles. Accordingly, there is a need for a reaction receptacle apparatus which can be manipulated by an automated assay instrument, where the apparatus may include one reaction receptacle or plurality of reaction receptacles coupled together as a single operative unit.