Sampling probe for microarray read out using electrospray mass spectrometry

#This invention relates generally to methods and apparatus for transport, ionization and subsequent analysis of analytes, and more specifically to methods and apparatus for analyzing a plurality of sample spots on an array using electrospray mass spectrometry.

#The study of protein complements of cells, tissues or whole organisms is referred to as proteomics. Proteomics is of great interest and much progress has been made in recent years in large part because of new enabling analytical technologies. One theme in proteomics is to monitor the expression of proteins in a biological system as the system responds to a stimulus. Currently, two-dimensional gel electrophoresis (2-DE) is the most common and powerful platform for the measurement of such protein complements. This approach can support expression profiling of several thousand proteins in multiple samples.

#However, 2-DE has several significant limitations. These limitations include, for example, difficulty in running membrane proteins, complicated gel image analysis and manual preparation and running of the gels. Moreover, 2-DE requires spot excising and clean-up to utilize the highly specific and sensitive mass spectrometric-based protein identification methods employed. Therefore, alternative measurement platforms for protein expression profiling within complex samples are being explored.

#A fuller understanding of the present invention and the features and benefits thereof will be accomplished upon review of the following detailed description together with the accompanying drawings, in which:

#FIG. 1 illustrates a sampling probe/ES-MS for surface array read out, according to an embodiment of the invention.

#FIG. 2(a) illustrates a surface contact probe, according to an embodiment of the invention.

#A system for detecting at least one analyte disposed in any of a plurality of spots in a surface array includes at least one sampling probe. An automatic positioning device is preferably provided for aligning the sampling probe relative to the array spots and for stepping to other array spots so that the detection process can be automatically repeated. The probe includes an inlet for flowing at least one eluting solvent to any of the array spots to carry the analyte and an outlet for directing the analyte away from the spot to an electrospray ion source for ionizing the analyte. A structure for analyzing ions, preferably being a mass spectrometer, identifies the analyte by analysis of the ions generated by the ES source. Accordingly, the invention does not require complicated and often unreliable extrinsic labeling methods for analysis generally required by previous methods for array sampling.

#The invention may be used to sample virtually any surface of interest. Accordingly, the invention has a broad range of potential applications. Protein microarrays is one such application. Protein microarray technology is a rapidly expanding market with a rapid projected growth rate. Some general uses of the invention include protein purification, protein expression profiling and protein interaction profiling, including protein-protein interactions and drug discovery. A road block to growth in this area has been identification of sensitive molecular specific detection methods for arrays that do not required complicated and often unreliable extrinsic labeling methods. Significantly, the invention does not require labeling for analyte detection.

#With regard to protein arrays, substrate surfaces can be coated with one or more regions having immobilized capture material thereon. For example, protein arrays can contain antibodies covalently immobilized onto the array surface to capture corresponding antigens from a complex mixture. Different spots can have different capture material thereon. Many different types of capture material substances can be bound to array substrates including antibodies, receptors, ligands, nucleic acids (e.g. DNA), carbohydrates, gels (e.g. isolelectric focusing gels), and chromatographic surfaces, such as cationic, anionic, hydrophobic, hydrophilic surfaces. Molecular imprinted materials may also be used as a capture material. Some surfaces can be designed to have broad specificity and bind whole classes of proteins, while others can be designed to be highly specific and bind to one or only a few proteins from a complex sample.