Received on August 9, 2005
Accepted on March 8, 2006

Cancer Diagnostics

Microfluidic Techniques for Single-Cell Protein Expression Analysis

¹ Department of Biology, Rider University, Lawrenceville, NJ
² Sarnoff Corporation, Princeton, NJ
³ Division of Medical Oncology/Hematology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, NJ

^* To whom correspondence should be addressed. E-mail: wiederro{at}umdnj.edu.

Background: The analysis of single cells obtained from needle aspirates of tumors is constrained by the need for processing. To this end, we investigated two microfluidic approaches to measure the expression of surface proteins in single cancer cells or in small populations (<50 cells).

Methods: One approach involved indirect fluorescence labeling of cell-surface proteins and channeling of cells in a microfluidic device past a fluorescence detector for signal quantification and analysis. A second approach channeled cells in a microfluidic device over detection zones coated with ligands to surface proteins and measured rates of passage and of retardation based on transient interactions between surface proteins and ligands.

Results: The fluorescence device detected integrin 5 expression induced by fibroblast growth factor-2 (FGF-2) treatment in MCF-7 cells and that of Her-2/neu in SK-BR-3 cells compared with controls. Experiments measuring passage retardation showed significant differences in passage rates between FGF-2-treated and untreated MCF-7 cells over reaction regions coated with fibronectin and antibody to integrin 51 compared with control regions. Blocking peptides reversed the retardation, indicating specificity.

Conclusions: Immunofluorescence detection in a microfluidic channel has the potential for assaying surface protein expression in a few individual cells and could permit the development of future iterations not requiring cell handling. The flow retardation device represents the first application of this technology for assessing cell-surface protein expression in cancer cells and may provide a way for analyzing expression profiles of single cells without preanalytical manipulation.