Method and apparatus for delivery of submicroliter volumes onto a substrate

Abstract

A slotted pin tool, a delivery system containing the pin tool, a substrate for use in the system and methods using the pin tool and system are provided. The slotted pin tool contains a plurality of pins having slotted ends designed to fit around each loci of material deposited on a surface, such as a microarray, without contacting any of the deposited material. Sample is delivered by contacting the pin tool with the surface; the amount delivered is proportional to the velocity of the pin tool as it contacts the surface or the velocity of the liquid when movement of the pin is halted.

Description

RELATED APPLICATIONS [0001] Benefit of priority under 35 U.S.C. §119(e) to U.S. provisional application Ser. No. 60 / 244,404, filed Oct. 30, 2000, to Chao Lin et al., entitled “METHOD AND APPARATUS FOR DELIVERY OF SUBMICROLITER VOLUMES ONTO A SUBSTRATE” is claimed herein. The subject matter of the provisional application is incorporated by reference in its entirety.BACKGROUND [0002] 1. Field of the Invention [0003] The invention relates to sample dispensing systems and, more particularly, to the delivery of liquid samples onto substrate, such as a microarray, for laboratory analysis. [0004] 2. Description of the Background Art [0005] Genetic sequencing efforts, such as the Human Genome project, have produced vast amounts of information for basic genetic research that have proven useful in developing advances in health care and drug research. These advances are possible because of improvements in engineering and instrumentation that provide advanced tools for the biotechnology communi...

AI Technical Summary

Benefits of technology

[0012] One delivery system with pin tool as constructed as provided herein, accurately delivers small volumes, typically submicroliter or nanoliter or picoliter volumes, of liquid samples onto a substrates, such as a microarray substrate, at high throughput rates by dipping a slotted pin tool (a pin tool having one or more pins with slotted ends) having an open tip into a sample reservoir or well containing a liquid sample to be delivered onto the substrate, thereby drawing a volume of liquid sample up into the pin tool. The slotted pin tool is then moved toward the substrate at a predetermined rate and then is halted, thereby expelling the liquid sample from the slotted pin tool onto the reaction location of the substrate. Thus, the sample fluid is expelled from the slotted pin tool by the force of momentum. The volume of liquid sample expelled is proportional to the momentum of the moving pin tool (i.e., the amount delivered is proportional to the velocity of the pin tool as it contacts the surface or to the velocity of the liquid in a pin when movement of the pin tool is halted). Hence volume delivered is a function of the speed of moving the pin tool toward the microarray, which provides a way to accurately control and deliver desired sample volumes. For each pin tool size there is a range of volumes in which the amount of volume delivered is a linearly of the velocity of the pin tool. Sample volume delivered is not dependent on tip surface areal, thereby providing for flexibility in use since it is not necessary to change pins to dispense different volumes.

[0014] For example, a pin tool provided herein with a 300 μm slot permits delivery of volumes of as low as about 1 nanoliter to 30 nanoliters. For this pin tool and for delivery of volumes in this range the volume delivered is linearly related to the velocity of the tool prior to halting it. Varying the size of the slot permits greater variation in volume delivered.

[0017] To move the pin tool towards the substrate, the holding block can be moved toward the substrate, such as a microarray substrate, until the slotted pins on the tool make contact with the microarray, whereupon the pin tool tips fit around the loci, such as spots of matrix material, without contacting any deposited material on the surface. The pin tool then moves upward in the pin tool holding block, which is then moved away from the microarray. Because it is designed to fit around each locus, the pin tool does not contact any material, such as matrix material for MALDI, cells, protein crystals or other materials, on the substrate. In this way, the dispensing system accurately deposits precise amounts of liquid sample on target locations, such as on a microarray substrate, with a high throughput rate, without contacting or damaging any material, such as matrix material, deposited on a substrate.

[0019] By virtue of the pin tool design herein, it is possible to transfer the sample to a pre-determined locus on a substrate that already has pre-deposited material, such as matrix, cells, such as bacterial or mammalian cells, protein crystals and other materials sensitive to contact. Since the instant tools provided herein rely on inertial forces for delivery, delivery of liquids is primarily dependent upon the momentum of the liquid in the slotted tool, not on the relative surface tensions of the pin and the substrate for the liquid. As one result, the pin tools provided herein permit accurate and controlled delivery of defined volumes by selection of the velocity of the tool at impact or as it reaches it the substrate and is stopped prior to contact.

Problems solved by technology

Pin tools also can be problematic for high throughput systems because the pins may have to be changed if different sample volumes are desired, or if the nature of the liquid sample is changed to avoid sample contamination.

In addition, pin tools cannot be used in situations where contact dispensing where there is a risk of damage to a fragile preloaded sample, such as for mass spectrometric analyses in which samples are deposited on loci that have preloaded material, such as matrix material for matrix-assisted laser desorption (MALDI).

When a sample target is preloaded or prespotted with the porous matrix material required for mass spectrometry, direct contact by the solid pin with the matrix material can crush the material.

Such piezoelectric delivery systems are susceptible to dispensing satellite droplets on a target location because of surface tension effects.

Piezoelectric systems also may be prone to variations in voltage and frequency among different tips, which results in variation between the volume of liquid sample dispensed from different individual tips.

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