It is well established that early cancer detection increases patient survival rates. The most obvious approach is to employ cancer markers for disease detection, but thus far, no single cancer marker has been demonstrated to conclusively predict a disease state. To address this problem we are developing diagnostic tools that are capable of multiplexed detection in a single sample. Toward this goal, we have designed a fully integrated, chip-based system for carrying out simultaneous, high-sensitivity detection of two protein cancer markers. Previously, we reported chip-based detection of a single protein target [1, 2, 3]. However, until now we have not demonstrated multiplexed detection, which presents significant new challenges. Here, we have addressed the many challenges associated with achieving a chip-based multiplexed assay. We have improved the microfluidic chip design, identified the proper chip coating to minimize nonspecific binding of probes, and advanced the identification of multiplexed biobarcode oligonucleotide strands [4]. Compared to the equivalent bench-top assay [5], the chip-based system decreases the reagent volumes, shortens the assay time (to less than three hours for the entire assay), and achieves comparable sensitivity. The shortened assay time assay time is attributed to the fact that the chip-based system forces the target molecules and probes into close proximity, leading to faster capture and decreased overall assay time. Our system also eliminates the need for several pieces of equipment used in the bench-top assay including incubators, vortexes, and centrifuges.

[1] E.D. Goluch, et al., “A Bio-Barcode Assay for On-Chip Attomolar-Sensitivity Protein Detection”, Lab-on-a-Chip, vol. 6, pp.1293-1299, 2006. [2] K.A. Shaikh, et al., “A Modular Microfluidic Architecture for Integrated Biochemical Analysis”, PNAS, vol. 102, pp. 9745-9750, 2005. [3] E.D. Goluch, et al., “A Microfluidic Device Using Nanoparticle-Based Bio-Barcodes for Ultra-Sensitive Detection of Protein”, in MicroTAS'04, Malmo, Sweden, September 26-30, 2004, pp. 342-344. [4] E.D. Goluch, et al., “Chip-Based High-Sensitivity Detection of Multiple Disease Biomarkers”, in MEMS'06, Istanbul, Turkey, January 22-26, 2006, pp. 478-481. [5] S.I. Stoeva, et al., “Multiplexed Detection of Protein Cancer Markers with Biobarcoded Nanoparticle Probes”, J. Am. Chem. Soc., vol. 128, pp. 8378-8379, 2006.