Scanning kelvinmicroprobe system and process for biomolecule microassay

• US 20040029131A1
• Filed: 02/28/2003
• Published: 02/12/2004
• Est. Priority Date: 05/24/2000
• Status: Abandoned Application

• Current Assignee: Sencorchem International Corporation
• Original Assignee: Sencorchem International Corporation
• Inventors: Thompson, Michael, McGovern, Mark, Cheran, Larisa-Emilia
• Application Number:
  US10/296,508
• Publication Number:
  US 20040029131A1
• Time in Patent Office: Days
• US Class Current: 435/6
• CPC Class Codes: B82Y 35/00 Methods or apparatus for measurement or analysis of nanostructures
• CPC Class Codes: G01N 27/002 by investigating the work function voltage
• CPC Class Codes: G01N 33/5438 Electrodes
• CPC Class Codes: G01Q 60/30 Scanning potential microscopy

Abstract

There is provided a system and process for detecting biomolecular interaction on a substrate having a biomolecule immobilized on a surface of the substrate. The system and process incorporate a scanning Kelvin microprobe (SKM) capable of analyzing surface topography as well as a contact potential difference image signal. Also provided is the use of SKM in measuring and analyzing biochemical molecular interactions between a probe bound to the surface of the substrate, and a target suspected to be present in a liquid sample. One of the probe and target combination is a biomolecule such as a nucleic acid, a polypeptide, or a small molecule, and an antibody antigen combination may be used.

Claims

1. A scanning Kelvin microprobe system for analyzing a biomolecular interaction on a surface of a substrate, said surface being capable of interacting with a biomolecule, the system comprising:

a tip with a predetermined work function for exploring the surface, and for extracting Kelvin current from the local capacitor formed between the tip and the substrate;

a scan table for placing the substrate thereon;

a micropositioner for moving the scan table in x and y directions;

a piezoelectric translation stage attached to the scan table for moving the substrate in the z direction for maintaining a constant substrate-tip distance;

a charge amplifier for converting the Kelvin current extracted by the tip into a voltage;

a first lock-in amplifier tuned at a first frequency for measuring the voltage and generating a contact potential difference image signal;

a second lock-in amplifier tuned at a second frequency for monitoring substrate-tip distance and for generating a topographic image signal, the second frequency being above the first frequency; and

a controller for controlling the micropositioner.

2. The scanning Kelvin microprobe system according to claim 1, additionally comprising a data acquisition system for acquiring said contact potential difference image signal and said topographical image signal.

3. The scanning Kelvin microprobe system according to claim 1, wherein said biomolecular interaction on a surface of a substrate comprises binding, hybridization, absorption, or adsorption.

4. The scanning Kelvin microprobe system according to claim 1, wherein the tip is a microelectrode having the apex radius of curvature less than about 100 nm.

5. The scanning Kelvin microprobe system according to claim 4, wherein said radius of curvature is about 50 nm.

6. The scanning Kelvin microprobe system according to claim 1, wherein the first frequency is from about 1 to about 20 kHz.

7. The scanning Kelvin microprobe system according to claim 1, wherein the second frequency is from about 100 to about 500 kHz.

8. The scanning Kelvin microprobe system according to claim 1, additionally comprising a substrate having a surface on which a probe is attached

14. Use of a scanning Kelvin microprobe system according to any one of claims 1 to 8, for assessing biomolecular interaction on a substrate.

15. A process for analyzing an interaction between a probe and a target using a scanning Kelvin microprobe system according to any one of claims 1 to 8, comprising the steps of:

immobilizing a probe on the surface of a substrate;

subjecting the probe to a first scanning Kelvin microprobe analysis;

exposing the probe to a composition suspected of containing the target;

subjecting the substrate to a second scanning Kelvin microprobe analysis; and

comparing the results of the first and second scanning Kelvin microprobe analyses to determine interaction between the probe and the target.

16. The process according to claim 15, wherein at least one of the probe and the target is a nucleic acid, a polypeptide, or a small molecule.

17. The process according to claim 16, wherein at least one of the probe and the target is a small molecule.

18. The process according to claim 15, wherein at least one of the probe and the target is an antibody.

19. The process of claim 18, wherein one of the probe and the target is an antigen.

9. A process for analyzing a biomolecular interaction on a surface of a substrate using a scanning Kelvin microprobe system, said surface being capable of interacting with a biomolecule, the process comprising the steps of:

placing a substrate on a scan table;

exploring a surface of the substrate with a tip having a predetermined work function;

extracting Kelvin current from a local capacitor formed between the tip and the substrate;

amplifying the Kelvin current extracted by the tip;

measuring the Kelvin current and generating a contact potential difference signal using a first lock-in amplifier tuned at a first frequency; and

monitoring distance between the substrate and the tip and generating a topographic image signal using a second lock-in amplifier tuned at a second frequency, the second frequency being above the first frequency.

10. The process according to claim 9, wherein the steps are controlled using a software program.

11. The process according to claim 9, wherein said biomolecular interaction on a surface of a substrate comprises binding, hybridization, absorption, or adsorption.

12. The process according to claim 9, wherein the first frequency is from about 1 to about 20 kHz.

13. The process according to claim 9, wherein the second frequency is from about 100 to about 500 kHz.